Brigham Young University Geology Studies
Brigham Young University Geology Studies
Brigham Young University Geology Studies
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<strong>Brigham</strong> <strong>Young</strong> <strong>University</strong> <strong>Geology</strong> <strong>Studies</strong><br />
Volume 24, Part 2<br />
CONTENTS<br />
<strong>Studies</strong> for Students: A Question Set for Sands and<br />
Sandstones ........................................................................................................................................................... Sedimentation Seminar<br />
A New Species of Arrqocrinus (Inadunata) from the Park City<br />
Formation (Upper Permian) of Utah .................................................................................................................... H. L. Strimple and<br />
J. F. Miller<br />
Additional Specimens of the Hypsilophodontid Dinosaur Dysaurus<br />
altus from the Upper Jurassic of Western North America ..............................................................................J effrey D. Shepherd,<br />
Peter M. Galton, and<br />
James A. Jensen<br />
Paleoenvironments of the Moenave Formation, St. George, Utah ........................................................................J ohn Daniel Davis<br />
Foraminifera1 Abundance Related to Bentonitic Ash Beds in the<br />
Tununk Member of the Mancos Shale (Cretaceous) in<br />
Southeastern Utah ................................................................................................................................... Rebecca Lillywhite Bagshaw<br />
Paleoecology of the Lower Carrnel Formation of the San Rafael Swell,<br />
Emery County, Utah .......................................................................................................................................... Lawrence H. Bagshaw<br />
Structure, Stratigraphy, and Tectonic History of the Indianola<br />
Quadrangle, Central Utah ........................................................................................................................................ David M. Runyon<br />
Compound Faceted Spurs and Recurrent Movement in the Wasatch<br />
Fault Zone, North Central Utah ....................................................................................................................... Thomas C. Anderson<br />
A Subsurface Correlation of Permian-Triassic Strata in<br />
Lisbon Valley, Utah .................................................................................................................................................. Ralph T. Bohn<br />
Mesozoic-Cenozoic Structural Development of the Kern Mountains,<br />
Eastern Nevada-Western Utah ............................................................................................................................... Robert C. Ahlborn<br />
Publications and Maps of the <strong>Geology</strong> Department<br />
Cover: Sahara dune sand, X130. Photo courtesy Amoco Pmduction Research, Tulsa, Oklahoma, contributed try Paul E. Potter, Depart-<br />
ment 4 Geolou, Univer~ity of Cincinnati, Cincinnati, Ohio 45221.
A publication of the<br />
Department of <strong>Geology</strong><br />
<strong>Brigham</strong> <strong>Young</strong> <strong>University</strong><br />
Provo, Utah 84602<br />
Editors<br />
W. Kenneth Hamblin<br />
Cynthia M. Gardner<br />
<strong>Brigham</strong> <strong>Young</strong> Univerrity <strong>Geology</strong> Studzes is published semiannually by the depart-<br />
ment. <strong>Geology</strong> <strong>Studies</strong> consists of graduate-student and staff research in the depart-<br />
ment and occasional papers from other contributors. <strong>Studies</strong> for Students supple-<br />
ments the regular issues and is ~ntended as a series of short papers of general<br />
interest which may serve as guides to the geology of Utah for beginning students<br />
and laymen.<br />
ISSN 0068-1016<br />
Distributed December 1977<br />
Pnce $>. 00<br />
(Subject to change without notice)<br />
12-77 525 28856
CONTENTS<br />
STUDIES FOR STUDENTS: A QUESTION SET<br />
FOR SANDS AND SANDSTONES ................................... 1<br />
PALEOENVIRONMENTS OF THE MOENAVE<br />
FORMATION. ST . GEORGE. UTAH ............................. 17<br />
I . Questions primarily answered in the laboratory .......... 1<br />
I1 . Questions primarily answered by the megascopic examination<br />
of outcrops and cores and by the study of wire<br />
line logs ............................................................................ 4<br />
111 . Format for a basin-Questions primarily answered by<br />
study of the entire basin or perhaps even a larger area<br />
such as a continental margin ......................................... 6<br />
Figures<br />
1 . Definition sketch of a typical sandstone ..................... 2<br />
2 . Minerals filling sandstone interstices ........................... 3<br />
3 . Flow chart using wire line logs ................................... 5<br />
4 . Flow chart for basin analysis ........................................ 6<br />
Tables<br />
1 . Classification of sand and sandstone bodies ................ 4<br />
2 . Format for basin study: properties and methods ....... 7<br />
Introduction ...........................................................................<br />
Previous work ....................................................................<br />
Location ..............................................................................<br />
Methods of study ..............................................................<br />
Acknowledgments ..................................................................<br />
Geologic setting .....................................................................<br />
General sedimentary features ................................................<br />
Geometry ............................................................................<br />
Channel-filling mechanisms ..........................................<br />
Composition .....................................................................<br />
Sedimentary structures ......................................................<br />
Paleocurren t data ....................................................................<br />
Fossils ......................................................................................<br />
Interpretation and reconstruction of the<br />
Moenave environment of deposition ...............................<br />
Interpretation I ........................... . ..................................<br />
Interpretation I1 .................................................................<br />
A NEW SPECIES OF ARROYOCRINUS (INADUNATA)<br />
FROM THE PARK CITY FORMATION (UPPER<br />
PERMIAN) OF UTAH ......................................................... 9<br />
Reconstruction of the Moenave tidal flat environment<br />
..............................................................................................<br />
Summary ................................................................................<br />
References cited ......................................................................<br />
29<br />
30<br />
30<br />
Introduction .............................................................................<br />
Systematic paleontology ..........................................................<br />
Description ...........................................................................<br />
Discussion ............................................................................<br />
Measurements of holotype in millimeters ......................<br />
Occurrence ..........................................................................<br />
Holotype .............................................................................<br />
Acknowledgments ..................................................................<br />
References ...............................................................................<br />
Figures<br />
1 . Photographs ....................................................................<br />
2 . Camera lucida drawings ...............................................<br />
ADDITIONAL SPECIMENS OF THE<br />
HYPSILOPHODONTID DINOSAUR<br />
DRYOSAURUS ALTUS FROM THE<br />
UPPER JURASSIC OF WESTERN<br />
NORTH AMERICA ............................................................. 11<br />
Introduction ...........................................................................<br />
Data on s~ecimens ............................................................<br />
Acknowledgments .................................................................<br />
Description and comparisons ................................................<br />
Vertebral column ...............................................................<br />
Pectoral girdle ....................................................................<br />
Fore limb ............................................................................<br />
Pelvic girdle ........................................................................<br />
Hind limb ...........................................................................<br />
Discussion ...............................................................................<br />
References cited ......................................................................<br />
Figures<br />
1 . Vertebrae .......................................................................<br />
2 . Pectoral girdle and forelimb ........................................<br />
3 . Pelvic girdle ...................................................................<br />
4 . Femora and tibiae .........................................................<br />
5 . Pes ..................................................................................<br />
Figures<br />
1 . Index map ................................................................... 18<br />
2 . Moenave Formation stratigraphy .............................. 19<br />
3 . North channel in airport roadcut ............................ 20<br />
4 . South channel in airport roadcut ............................. 20<br />
5 . Schematic drawing of tabular appearance of massive<br />
mudstone layers which enclose the channel deposits<br />
20<br />
6 . Bedding plane inclinations in channels ................... 21<br />
7 . Bundles of ribbon sand bodies at Interstate 15 roadcut<br />
................................................................................ 22<br />
8 . Schematic drawing . of ribbon sand bodies, Interstate 15<br />
roadcu t ......................................................................... 22<br />
9 . Intraformational conglomerate lens .......................... 23<br />
10 . Flaser bedding ................................ . ..................... 23<br />
11 . Wavy bedding ............................................................. 23<br />
12 . Planar cross-bedding ................................................... 24<br />
13 . Small-scale trough type crossbedding ...................... 24<br />
14 . Paleocurrcnt trends in channel undulations ............ 24<br />
15 . Vector diagrams of paleocurrent trends ................... 25<br />
16 . Location map of paleocurrent measurements along the<br />
erosional cliffs north of St . George Blvd ................ 26<br />
17 . Location map of paleocurrent measurements for positions<br />
G and H ............................................................ 26<br />
18 . Paleocurrent summary diagram of positions Aj .... 27<br />
19 . Vertical burrows ......................................................... 28<br />
20 . Horizontal burrows ................................................... 28<br />
21 . Burrows preserved as cavities .................................... 28<br />
22 . Reconstructed model diagram of the Moenave tidal<br />
flat in the St . George area ........................................ 29<br />
23 . Regional paleocurrent trends .................................... 30<br />
Table<br />
1 . Summary of current flow data ................................. 25<br />
FORAMINIFERAL ABUNDANCE RELATED TO<br />
BENTONITIC ASH BEDS IN THE TUNUNK
MEMBER OF THE MANCOS SHALE (CRETACEOUS) Au tecology .........................................................................<br />
IN SOUTHEASTERN UTAH ............................................ 33<br />
Introduction ...........................................................................<br />
Acknowledgments ..............................................................<br />
Previous work ....................................................................<br />
Field and laboratory methods ...........................................<br />
Fauna .......................................................................................<br />
Paleoecology ............................................................................<br />
Conclusions .............................................................................<br />
Systematic paleontology ........................................................<br />
References cited ......................................................................<br />
Figures<br />
1 . Stratigraphic section ...................................................<br />
2 . Index map ...................................................................<br />
3 . View of Tununk stratigraphy ...................................<br />
4 . View of trench through ash 2 ..................................<br />
5 . Graph of foraminifera1 abundance in ash 1 ............<br />
6 . Graph of foraminifera1 abundance in ash 2 ............<br />
7 . Graph of foraminifera1 abundance in ash 3 ............<br />
8 . Graph of foraminifera1 abundance in ash 4 ............<br />
9 . Graph of foraminifera1 abundance in ash 5 ............<br />
10 . Foraminifera1 fauna .....................................................<br />
11 . Foraminifera1 fauna<br />
. .<br />
.....................................................<br />
12 . Foraminiferal fauna .....................................................<br />
13 . Foraminifera1 fauna .....................................................<br />
Tables<br />
1 . Foraminifera] occurrence in ash 1 ............................<br />
Trigonza and Vaugonia ..................................................<br />
Camptmrectes ....................................................................<br />
Gtphea ( ?) .......................................................................<br />
ModioIus(?) and Nucula(?) ...........................................<br />
Environment ...........................................................................<br />
General ................................................................................<br />
Salinity ............................................................................<br />
Temperature ...................................................................<br />
Interpretation of sedimentary environments .......................<br />
Tidal flat .............................................................................<br />
Open marine ......................................................................<br />
Barrier lagoon ..................................................................<br />
Sedimentary model .................................................................<br />
Conclusions .............................................................................<br />
Appendix .................................................................................<br />
References cited ......................................................................<br />
Figures 0<br />
1 . Index map .....................................................................<br />
2 . Stratigraphic section .....................................................<br />
3 . Generalized east-west Carmel time cross section ......<br />
4 . Paleogeographic setting of the study area .................<br />
5 . Field views .....................................................................<br />
6 . Photomicrographs ........................................................<br />
7 . Stratigraphic section ..................................................<br />
8 . Fossils and an unusual sedimentary structure ...........<br />
9 . Sedimentary model .......................................................<br />
2 . Foraminifera1 occurrence in ash 2 ............................<br />
3 . Foraminifera1 occurrence in ash 3 ............................<br />
4 . Foraminifera] occurrence in ash 4 ............................<br />
5 . Foraminifera1 occurrence in ash 5 ............................<br />
37<br />
38<br />
39<br />
41<br />
STRUCTURE. STRATIGRAPHY. AND TECTONIC<br />
HISTORY OF THE INDIANOLA QUADRANGLE.<br />
CENTRAL UTAH ...............................................................<br />
Introduction ..........................................................................<br />
PALEOECOLOGY OF THE LOWER CARMEL<br />
FORMATION OF THE SAN RAFAEL SWELL.<br />
EMERY COUNTY. UTAH ................................................<br />
Acknowledgments ..............................................................<br />
Previous work ....................................................................<br />
Geologic evolution and regional setting .............................<br />
Present-day setting ................................................................<br />
Introduction ...........................................................................<br />
Acknowledgments ..............................................................<br />
Location ..............................................................................<br />
Methods of study ..............................................................<br />
Previous work ....................................................................<br />
Geologic setting .................................................................<br />
Li thologies ..............................................................................<br />
Sandstone ............................................................................<br />
Stratigraphy .............................................................................<br />
Jurassic .....................................................................................<br />
Arapien Shale .....................................................................<br />
Twist Gulch Formation ....................................................<br />
Cretaceous ...............................................................................<br />
Indianola Group ................................................................<br />
South Flat Formation ........................................................<br />
Price River Formation ......................................................<br />
Light yellow brown sandstone ....................................<br />
Medium brown sandstone ............................................<br />
Siltstone ..............................................................................<br />
Red siltstone ................................................................<br />
Gypsiferous and dolomitic siltstone ............................<br />
Shale ....................................................................................<br />
Green shale ....................................................................<br />
Grey shale ......................................................................<br />
Red shale ........................................................................<br />
Carbonate rocks .................................................................<br />
Calcarenite ....................................................................<br />
Dololu tite .......................................................................<br />
Cretaceous-Tertiary ................................................................<br />
North Horn Formation ....................................................<br />
Tertiary ....................................................................................<br />
Flagstaff Formation ............................................................<br />
Green River Formation .....................................................<br />
Unnamed volcanic rocks ...................................................<br />
Quaternary ..............................................................................<br />
Unnamed ...........................................................................<br />
Sedimentary tectonics ............................................................<br />
Structure ..................................................................................<br />
Faults ..................................................................................<br />
Joints ...................................................................................<br />
Dolarenite ......................................................................<br />
Sedimentary structures ...........................................................<br />
Ripple marks ......................................................................<br />
Flute casts ...........................................................................<br />
Mudcracks ...........................................................................<br />
Miscellaneous ......................................................................<br />
Paleon tology ...........................................................................<br />
Faunal assemblages ...........................................................<br />
Folds ...................................................................................<br />
Tectonic history ....................................................................<br />
Economic geology .................................................................<br />
Overview .................................................................................<br />
Appendix .................................................................................<br />
Arapien Formation ...........................................................<br />
Twist Gulch Formation ....................................................<br />
Indianola?-Price River Formation?<br />
..................................
North Horn Formation ................................................. 81<br />
Flagstaff Formation ............................................................ 81<br />
References cited ...................................................................... 81<br />
Figures<br />
1 . Index map ...................................................................<br />
2 . Stratigraphic column .................................................<br />
65<br />
65<br />
3 . Hjork Creek diapir (Twist Gulch) ........................... 66<br />
4 . North San Pitch collapsed diapir (high altitude vertical)<br />
............................................................................... 66<br />
5 . Hjork Creek vertical outcrop .................................... 68<br />
6 . Price River outcrop, overturned South Flat ............ 69<br />
7 . Formline contour map ...............................................<br />
8 . North Horn channels ................................................<br />
69<br />
71<br />
9 . North Horn "giant" algal balls ................................<br />
10 . North Horn algal ball ...............................................<br />
71<br />
71<br />
11 . Pollen photomicrographs ...........................................<br />
12 . Tertiary volcanic stream deposits ..............................<br />
73<br />
74<br />
13 . North San Pitch collapsed diapir (low oblique) .... 75<br />
14 . Salt Valley cuesta ........................................................ 75<br />
15 . Green River cuesta ..................................................... 75<br />
16 . Seven-step geologic evolution ................................... 76<br />
17 . Stream pattern analysis . Stippled areas denote areas of<br />
controlled drainage ..................................................... 77<br />
18 . Rebound diagram ................................................. 79<br />
19 . Geologic map with cross sections A-A', B-B', and C-<br />
C' ...................................................................... in pocket<br />
COMPOUND FACETED SPURS AND RECURRENT<br />
MOVEMENT IN THE WASATCH FAULT ZONE.<br />
NORTH CENTRAL UTAH ............................................... 83<br />
Introduction ...........................................................................<br />
Acknowledgments ..............................................................<br />
Previous studies ......................................................................<br />
Early work ..........................................................................<br />
General geology .................................................................<br />
Wasatch fault geometry ....................................................<br />
Geophysics ..........................................................................<br />
Origin of pediments ..........................................................<br />
Conceptual model ..................................................................<br />
Pediment formation ..........................................................<br />
Recurrent uplift ................................................................<br />
Pediment preservation .....................................................<br />
Downcutting ......................................................................<br />
Slope retreat .......................................................................<br />
Structural control .............................................................<br />
Sequential development ...................................................<br />
Methods ...............................................................................<br />
Aerial photography ...........................................................<br />
Pediment mapping ..........................................................<br />
Profile projection .............................................................<br />
Correlation ..........................................................................<br />
Results ....................................................................................<br />
Payson Canyon to Spanish Fork Canyon ......................<br />
Spanish Fork Canyon to Springville ...............................<br />
Springv~lle to Provo Canyon ............................................<br />
Provo Canyon to American Fork Canyon ......................<br />
American Fork Canyon to the Traverse Mountains .....<br />
Conclusions .............................................................................<br />
Pediment formation and slope retreat ............................<br />
Uplift and quiescence .......................................................<br />
Absolute dating ................................................................<br />
Tilt .....................................................................................<br />
Regional geodynamics .......................................................<br />
Suggested further studies ..................................................<br />
References cited ...................................................................... 33<br />
Figures<br />
1 . Index map ................................................................... 84<br />
2 . Conceptual model of compound faceted spur development<br />
.................................................................... 87<br />
3 . Spanish Fork Peak ...................................................... 30<br />
4 . Selected facets on Spanish Fork Peak ...................... 30<br />
5 . Area near Hobble Creek Canyon ............................. 30<br />
6 . Section of Spanish Fork Peak quadrangle topographic<br />
map ........................................................................... 91<br />
7 . Same map as figure 6 with facets and pediments dentified<br />
.......................................................................... 91<br />
8 . Profile of rangefront ................................................. 92<br />
9 . Loafer Mountain area with key pediment correlations<br />
94<br />
10 . Spanish Fork Peak area with key pediment correlations<br />
............................................................................. 94<br />
11 . Hobble Creek area with key pediment correlations<br />
94<br />
12 . Maple Flat area with key pediment correlations ..... 95<br />
13 . Mount Timpanogos area with key pediment correlations<br />
............................................................................. 96<br />
14 . Alpine area with key pediment correlations ............ 96<br />
15 . Stranded streams at Corner Creek area .................... 97<br />
16 . Generalized profile of range showing main correlations .<br />
and uplift patterns ...................................................... 97<br />
17 . Sketches of the Spanish Fork Peak area showing probable<br />
historical development ...................................... 98<br />
A SUBSURFACE CORRELATION OF PERMIAN-<br />
TRIASSIC STRATA IN LISBON VALLEY. UTAH .... 103<br />
Introduction ..........................................................................<br />
Acknowledgments ............................................................<br />
Previous work ..................................................................<br />
Geologic setting ...................................................................<br />
Stratigraphy ....................................................................<br />
Structure ...........................................................................<br />
Cutler stratigraphy ...............................................................<br />
Sandstones ..............................................................<br />
Calcareous arkose .........................................................<br />
Arkosic wacke ...........................................................<br />
Mudstones ...................................................................<br />
Sandy rnudstone .....................................................<br />
Mudstone ................................................................<br />
Sandy limestone ..............................................................<br />
Chinle stratigraphy ..............................................................<br />
Sandstone .......................................................................<br />
Calcareous arkose .....................................................<br />
Arkosic wacke ......................................................<br />
Mudstone ...................................................................<br />
Sandy mudstone ........................................................<br />
Mudstone .............................................................<br />
Conglomerate ...............................................................<br />
Mudstone conglomerate .......................................<br />
Strat~graphic correlation ....................................................<br />
Appendix ............................................................................<br />
Measured section ............................................................<br />
Core 3 .........................................................................<br />
Core 9 ............................................................................<br />
References cited ................................................................<br />
Figures<br />
1 . Index map ...............................................................<br />
2 . Fence diagram .........................................................<br />
3 . Map of Lisbon Valley ..............................................
4 . Stratigraphic column ................................................<br />
5 . Cutler Formation calcareous arkose ........................<br />
6 . Cutler Formation arkosic wacke .............................<br />
7 . Mudstone ...................................................................<br />
8 . Cutler Formation sandy limestone .........................<br />
9 . Diagram of cores ......................................................<br />
10 . Chinle Formation calcareous arkose .......................<br />
11 . Chinle Formation arkosic wacke .............................<br />
12 . Chinle Formation conglomerate .............................<br />
13 . Cutler and Chinle formations .................................<br />
Tables<br />
1 . Logs and drilling data ..............................................<br />
2 . Core composition .....................................................<br />
MESOZOIC-CENOZOIC STRUCTURAL DEVEL-<br />
OPMENT OF THE KERN MOUNTAINS. EASTERN<br />
NEVADA-WESTERN UTAH ......................................... 117<br />
Introduction ..........................................................................<br />
Previous work ..................................................................<br />
Acknowledgments ............................................................<br />
Structures of the sedimentary cover ..................................<br />
General statement ............................................................<br />
Low-angle faults ...............................................................<br />
Regional denudation ...................................................<br />
Local denudation .........................................................<br />
High-angle faults .............................................................<br />
Folds ..................................................................................<br />
Metamorphic structures .......................................................<br />
General statement ............................................................<br />
Skinner Canyon study .....................................................<br />
Macroscopic structures ................................................<br />
Mesoscopic fabric .........................................................<br />
Microscopic fabric ........................................................<br />
Structure of the plutonic complex ....................................<br />
General statement ............................................................<br />
Foliation ............................................................................<br />
Joints .................................................................................<br />
Dikes .................................................................................<br />
Stratigraphy ...........................................................................<br />
General statement ............................................................<br />
Metamorphic rocks ..............................................................<br />
General statement ............................................................<br />
Metamorphic rock description ............................................<br />
Marble and dolomarble ...................................................<br />
Phyllitic rocks ..................................................................<br />
Calc-silicate rocks .............................................................<br />
Schist .................................................................................<br />
Quartzite ...........................................................................<br />
Metaigneous rocks ...........................................................<br />
Mineral assemblages .........................................................<br />
Mafic assemblages ........................................................<br />
Pelitic assemblages .......................................................<br />
Calcareous and calc-silicate assemblages ....................<br />
.<br />
Contact vs . regional metamorphism .................................. 127<br />
Age of metamorphic rocks ................................................. 127<br />
Igneous rocks ..................................................................... 128<br />
General statement ............................................................ 128<br />
Volcanic rocks .............................................................. 128<br />
Rhyodacite .................................................................... 128<br />
Dacitic rocks ................................................................ 129<br />
Tuff ............................................................................. 129<br />
Summary and conclusions ............................................. 129<br />
References cited .............................................................. 130<br />
Figures<br />
1 . Index map ............................................................... 118<br />
2 . Structural outline .................................................... 119<br />
3 . Geologic map ................................................. in pocket<br />
4 . Sterographic projection of fold axes ....................... 121<br />
5 . Sterographic projection of axial planes .................. 121<br />
6 . Sterographic projection of metamorphic foliation 121<br />
7 . Sterographic projection of granitic foliation ......... 123<br />
8 . Sterographic projection of joints ............................ 123<br />
9 . Sterographic projection of aplitic dikes .................. 123<br />
10 . Generalized stratigraphic column of regional stratigra-<br />
phic and Kern Mountains stratigraphic column .. 124<br />
11 . Generalized geologic map of Kern Mountains ..... 125<br />
12 . Metamorphic rock correlation ................................. 129<br />
Table<br />
1 . Kern Mountains geologic history ........................... 120
<strong>Studies</strong> for Students: A Question Set for Sands and Sandstones<br />
SEDIMENTATION SEMINAR*<br />
H. N. Fisk Laboraloty of Scriirnentology<br />
Untvcrnry o/ Gnnnnali<br />
Gncmnati, Ohro 45221<br />
He who asks good questions cannot but profit and advance his cause.<br />
ABSTRAC~ -This questlon set 1s based on the assumption that each fcamre of learning exper~ence-one directly aimed at solving the many<br />
sand or sandstone has a reason for being what and where it IS-~f we as xdi- significant problems associated with sands and sandstones,<br />
mentolop~sts " could but wrceive ~t. In addinon, we are firm bellwers In the<br />
idea that success-in virtually all aspects of human endeavor-is based on correct<br />
answers to nght questions.<br />
We developed this question set during a quarter's study<br />
of advanced sandstone petrology primarily to help us solve,<br />
in as systematic a way as possible, some of the many fasclnating<br />
problems associated with sand and sandstone. Our initial<br />
inspiration came from Wilson's question set for limestones<br />
(1975, p. 60-63) and from Folk's earlier detailed petrographic<br />
report form (1968a, p. 133-38). Consider, for example, some<br />
of the general questions below-only a small sample of the<br />
many that one can answer better after a carefully detailed<br />
analysis.<br />
1. What factors control the framework composition of a<br />
sand? How does the relative importance of these factors<br />
vary in basins with different climatic settings'<br />
How is framework composition related to plate tectonics?<br />
How can we better distinguish between the immediate<br />
and ultimate source of a sandstone?<br />
2. With petrography as the sole basis, how effectively<br />
can we recognize major and minor depositional environments?<br />
3. How much can be said about the hydraulics of the<br />
depositional medium on the basis of grain size, structures,<br />
and geometry of a sandstone body?<br />
4. How does a careful appraisal of the fossll content of a<br />
sandstone help us better determine its environment of<br />
deposition? And what bearing does fossll content have<br />
on cementation?<br />
5. To what extent does the porosity and cementation<br />
history of a sandstone depend upon the initial composition<br />
of its framework grains in their final deposltiona1<br />
environment? Or are ultimate depth of burial and<br />
thermal hlstory more important?<br />
A wide range of specific detailed observations are needed to<br />
answer such broad questions as these-or, in other words, an<br />
inventory of essentzal facts, facts that are relevant to today's<br />
ideas of the origin of sand and sandstones. We organized the<br />
question set below under three major headings: those that<br />
are best answered in the laboratory; those that are based on<br />
the megascopic study of cores and outcrops; and those that<br />
pertain to an entire depositional basin or perhaps even a<br />
wider area such as an entire continental margin. After many<br />
questions we have given a short explanation of their background<br />
and/or motivation as well as a few references, where<br />
these seemed necessary. Together, the question and its background<br />
motivation serve, we hope, as a type of programmed<br />
I. QUESTIONS PRIMARILY ANSWERED IN THE<br />
LABORATORY. These questions primarily involve petrography,<br />
the SEM, X-ray diffraction, and radiography, as<br />
well as grain size and chemical ana(yses. Typically, these<br />
techniques are applied to the grain types present in the<br />
framework and to the interstices-solids (cements and rnatnx)<br />
as weCl as the pore space and its &ids (fig. I).<br />
A. Grain types and their abundance? Many papers are<br />
devoted to the general signijicance of grain types, but we<br />
Jound Drckinson (1969, 1970) and Pettijohn et al.<br />
(1 972, p. 29-47, 175-326) epecially helpfuul.<br />
1. Amount of quartz, feldspars, rock fragments,<br />
and micas?<br />
2. Amount of unlt auartz. bimodal com~osite<br />
I<br />
quartz, unimodal composite quartz, and polygonal<br />
composite quartz? See Basu et al. (1975) Jar<br />
the most recent miew of quartz types, whrch continue<br />
to play an important role in sandone petrology.<br />
3. Amount of K-feldspar, Na-plagioclase, and Caplagioclase?<br />
a. Amount of sanidine, microcline, and orthoclase?<br />
b. Amount of A-twins, C-twins, and untwinned<br />
plagioclases (Pittman 1970) ?<br />
c. Ratio of unweathered to weathered K-feldspar<br />
as well as the ratio of unweathered to<br />
weathered plagioclase?<br />
4. Amount of igneous, sedimentary, and metamorphlc<br />
rock fragments? Rock fragments, their types<br />
and abundances, are one of the most telling pmvenance<br />
indicators even m thezr absence-an almost<br />
sure sign of a many-cycled sandstone.<br />
5. Ratio of plutonlc to volcanic rock fragments? A<br />
rough measure of the depth 4 erosion of the crust as<br />
well as an zndzcation of leading (more volcanics) versus<br />
trailing (more plutonics) contznental margins<br />
(Reading 1972, table 2).<br />
a. Percent of plutonic rock fragments chat have<br />
an acid, intermediate, and basic composition?<br />
b. Percent of volcanic rock fragments that have<br />
an acid, intermediate, and basic composition?<br />
6. Ratio of clastic to carbonate sedimentary rock<br />
fragments? Carbonate rock fragments (cabbths) in<br />
a temgenous sand or sandstone derived from outszde<br />
the basin of deposition indzcate either a dry clzmate, a<br />
glacial source, or very, vely rapid erosion of a high<br />
relief tewazn rich in carbonates.<br />
'Pamcrpno nnclude Barv Acomb. Mrhacl D Lmn. Lynn E McLanc, Bnndon C Nurnll. Nal &muds. Fdcnrk Schauf, Gmgory Wahlrnm, and Rul Edwln Porrcr<br />
1
a. Percent of clastic rock fragments that are<br />
shales, silts, sandstones, and conglomerates?<br />
b. Percent of carbonate rock fragments that are<br />
mudstones, wackestones, packstones, and<br />
grainstones?<br />
c. Percent of sedimentary rock fragments that<br />
are cherts and siliceous sediments, iron-bear-<br />
ing sediments, glauconites, and phosphorites?<br />
7. Percent of metamorphic fragments that are slate-<br />
phyllite, schist, gneiss, marble, and quartzite?<br />
8. Heavy minerals? Currently less used in studies 4<br />
sandstones than they probably shouM be but still a<br />
very useful and efficient indicator of provenance.<br />
a. Which heavy minerals are present?<br />
b. Percent of heavy minerals that are ultrastable,<br />
stable, moderately stable, unstable, very un-<br />
stable? What is the ZTR index of Hubert<br />
(1962)?<br />
c. Which species show evidence of etching<br />
and/or overgrowths? A sensitive indicator of di-<br />
agenesis.<br />
9. Microfossil debris? Fods in sands and sandstones<br />
have too ofen been overlooked try too many 4 us, yet<br />
when present, they can contribute importantly to our<br />
knowledge of ofositiond environment, via their pa-<br />
lewcology, as well as to stratigraphic correlation and<br />
possibly win diagmetic history-as a source of carbo-<br />
nate cement.<br />
a. Percentage of diverse types? Fossils versus pel-<br />
lets?<br />
b. Ratio of benthonic to planktonic forams, if<br />
forams are present? Particularly useful in help-<br />
ing to better define sheIf-to-basin transitions and<br />
possible associated turbidites (6 Pflum and Fred-<br />
richs 1976, for a good example f m the Gulf of<br />
Mexico).<br />
SEDIMENTATION SEMINAR<br />
c. Ratio of in-situ-to-reworked fossil debris? Primarily<br />
based on chambers containing a filling different<br />
from the matrix and on Agree of wear<br />
and fragmentation.<br />
d. Special significance for bathymetry? Modern as<br />
well as ancient marine communities are penerallv 0<br />
distributed in bands parallel to coastlines and can<br />
thus suggest &th, which is also relatable direct4<br />
to temperature, light, and other factors (Walton<br />
1964, Murray 1973).<br />
e. Evidence of solution? A direct clue to diagenetic<br />
history-a good example is the carbonate<br />
study of Boyd and Newell (1972), which has<br />
many techniques applicable to the study of fossils<br />
in sands and sandstones.<br />
B. Types of interstice fillings and their relative abundances<br />
(fig. 2)? These questions generally are directed<br />
toward the evaluation 4 the economic value of a sandstone,<br />
its history of fluid migration, and secondary mineralization.<br />
1. Porosity: is it filled with air, water, or organic<br />
matter (including oil and tar)?<br />
2. Percent of interstices filled by mineral matter?<br />
Percent of mineral interstices composed of<br />
quartz, chert, calcite, dolomite, siderite, magnesite,<br />
clay minerals, feldspars, sulfate minerals,<br />
and crushed rock fragments? Do any of these<br />
grow on favored hosts?<br />
3. Types and abundance of authigenic clays? A vital<br />
aspect of reservoir studies 4 sandstones, because of<br />
the tendency for clays to 'Iplug up" sandstones and<br />
thus greatly reduce their permeability. See Wilson and<br />
Pittman (1977) for the most up-to-date, well-documented<br />
study.<br />
4. Percent of the interstices filled by solid carbonaceous<br />
matter, tar, and oil?<br />
FRAMEWORK GRAINS INTERSTICES<br />
7 7<br />
Indicate mostly provenance, but<br />
yield some information about<br />
depositional environment and can<br />
influence history of compaction<br />
and diagenesis especially when<br />
rich in rock fragments and/or<br />
fossil debris.<br />
FIGURE 1.-Dcf~nition sketch of a typical sandstone and thc gcncnl significance of studies of its fnmework and intcrsticcs.<br />
Fine detrital debris, secondary<br />
precipitated cements and possible<br />
empty pores, the key to successful<br />
understanding being the<br />
establishment of an "interstices<br />
stratigraphy" followed by the<br />
mapping of its units.
5. Is the water in the interstices fresh, brackish,<br />
marine, or hypersaline? What is the chemical<br />
composition (e.g., Ca, Mg, Na, SO4-, C1-,<br />
and HCO;), Eh, and pH of the interstice wa-<br />
ters? The chemistry of the pore waters of sandstones is<br />
still poorly known, partly because it is troublesome to<br />
determine in subsurface drilling. Nonetheh, rt offers<br />
a signzficant potential for better dating diagenetic<br />
minerals to their precipirating (or dissolving) f7uids.<br />
One should recognize, of course, that the history of<br />
fluid saturation 4 a sandstone varies with the burial<br />
history of its basm; e.g., uplift and proximity to un-<br />
conformities and/or faulting both of which may in-<br />
troduce j'uids whose composition varies markedly from<br />
pevious ones. A general overuiew of water chemistry<br />
is provided by Bemer (1971, p. 86-209), Helgeson<br />
(1968) gives a careful thermodynamic anaLysis, and a<br />
specific discussion of interstitial waters and clastics is<br />
provided by Schmidt (1973) for the Gulf Coast of<br />
the United States,<br />
C. Textural aspects of grains?<br />
1. What is the grain-size distribution? Grain size is<br />
a function of what was available in the unweathered<br />
source rocks, of the weatheving history of the source<br />
areas, and, to same degree, of the depositional procesJ.<br />
A vast literature has been produced on this subject<br />
from the time of U& (1914) to the present day-<br />
good reuiews being those of &an (1970), Glaister<br />
and Nelson (1974) and Middleton (1976).<br />
a. What is the central tendency of the distribu-<br />
tion (e.g., mean, mode, and median)? A very<br />
rough measure of the competence of the media.<br />
b. Is the distribution bimodal? See Folk (1968b)<br />
for one specific interpretation 4 bimodal texture<br />
in sandstones.<br />
c. What is the sorting and skewness? To some<br />
degree a measure of the depositional procesj with,<br />
Drusy Quartz Syntaxial Rim Early Fibrous<br />
or Calcite Pore Cement of Rim Cement<br />
Filling Calcite or Quartz and/or Cloy<br />
Kaolinite Pseudo- Kaolinite Pore<br />
morph and Clay Filling Following<br />
Matrix of Wacke- Quartz Overgrowths<br />
stone<br />
Clay Poste of Dolomite Rhombs Floating Grains<br />
Wackestone Replace Calcite in Early Poikilitic<br />
and Quartz Calcite Cement<br />
FIGURE 2.-Some textural and mineralogical features of minerals filling sand-<br />
stone interstices.<br />
QUESTION SET FOR SANDS 3<br />
for example, wind favoring an elimination of<br />
j~nes, etc,<br />
d. What form does the distribution have when<br />
plotted on log probability paper? Many consid-<br />
er a plot of the size distribution on log normal<br />
paper to give the best insight into its origin.<br />
2. What percent of the grains are rounded, sub-<br />
rounded, subangular, and angular? How does<br />
roundness vary with grain type? And with size<br />
for each grain type? Easy to see and measure, the<br />
roundness of individual grains is the key to their<br />
abrasion history.<br />
3. What percent of the grains are equidimensional<br />
and elongate? Generally elongate grains are the<br />
product of a metamopPhic prwince, whereas equi-<br />
dimensional grains are the prodmt of plutonrc or sedi-<br />
mentary provinces (Bokman 1952).<br />
4. What percent of the grains have overgrowths<br />
and how, if at all, do they affect the overall<br />
grain-size distribution?<br />
5. Do elongated grains show a preferred orienta-<br />
tion? Elongate grains are the best fabric elements of<br />
the framework to infer paleocurrents (Potter and<br />
Mast 1963, fig. 3).<br />
6. Are grain surfaces frosted or pitted? SEM photo-<br />
graphs of grain surfaces have rehabilitated the study<br />
of grain-surface textures and, in modem loose ~ands,<br />
apparently give some clues to environmental history<br />
(Krinsleely and MargoIis 1969, Attman 1972) where-<br />
ac in ancient sandstones surface texture probably most-<br />
ly represents diagenetic history.<br />
D. Textural aspects of interstices? Here we are primarily<br />
concerned with the geometry of the pore system-its size<br />
distribution and surface roughness, two factors that are<br />
hard to measure directly but are, nonetheless, the immedi-<br />
ate determinants of permeabilig. See Orme and Brown<br />
(1 963, fig. 1) and Ome (1 974, pl. 10) for a summary<br />
of the texture and fabrics of secmrdtry quartz and car-<br />
bonate cements and the study of Glover (1963).<br />
1. What are the average diameter and size range of<br />
the open pores? Are the interstices lined with a<br />
druse, or with clay minerals?<br />
2. Are the interstices filled with a carbonate or ar-<br />
gillaceous mud, microcrystalline material, or do<br />
they have instead a filling of a coarse crystalline<br />
mosaic? How much is present? Is filling com-<br />
plete or partial?<br />
3. To what degree are interstices connected to one<br />
another?<br />
4. What is the typical cross-sectional shape of a<br />
pore?<br />
5. Do syn taxial overgrowths fill interstices?<br />
6. Does microcrystalline material near the border of<br />
an interstice grade inward into coarser crystalline<br />
mosaics toward the center?<br />
7. Do spherulitic growths occur along the inter-<br />
stice boundaries?<br />
8. Do interstices appear to be the result of partial<br />
or complete dissolution of unstable framework<br />
grains?<br />
E. Textural relationships between grains and inter-<br />
stices? These relationships are a result of events that oc-<br />
curred in the final depositional environment as well as<br />
subsequently. Not uncommanly, separation of these two<br />
possibilities is difficult, but more and more it is being re-
SEDIMENTATION SEMINAR<br />
alized that many oj the dzagenetic features o/ a sandstone<br />
are related to its framework composrtron (4 Galfway<br />
1974).<br />
1 the sandstone gram supported? A rough measure<br />
of sedrment sorting.<br />
2. What are the relatlve percentages of sutured<br />
grain contacts, concavo-convex contacts, polnt<br />
contacts, long contacts, and floating grains (Pett~john<br />
et al. 1972, table 3-4)? A good guzde to<br />
compactional and cementation brstoty.<br />
3. What evidence of compaction (eg., stylolites,<br />
crinkled mlca flakes, crushed rock fragments,<br />
and packing density)?<br />
4. Can fractures be seen In th~n sect~on?<br />
a. Is the fracture pattern systematic, anastomosing,<br />
or random?<br />
b Are the fracture boundar~es sharp or ragged?<br />
c. Are the fractures filled or empty? If filled, by<br />
what minerals?<br />
d. Do fractures cut grains?<br />
5. What is the poroslty and permeab~l~ty of the<br />
sample' It has been proposed that the two best werall<br />
measures o/ the dzagmetrc hrstory of a sandstone<br />
are rts porosrty and its penneabrlrty.<br />
F. What sed~mentary structures can be seen In thln<br />
section or hand spec~men? Even on the small scale of<br />
thin sectrons and hand specimens the study o/ sedimentary<br />
structures can be most rewardrng especially in relatzon to<br />
fabnc and permeabilrty.<br />
1. Are there any prlmary sed~mentary structures<br />
(e.g., massive, laminated, or graded bedd~ng or<br />
cr&-bedding) ?<br />
2. Types and abundance of inorganic deformational<br />
structures (founder and load structures, convolute<br />
bedding, slump~ng, inject~on, etc.)' Ratlo<br />
of d~sturbed to undisturbed beddlng?<br />
3. Types and abundance of b~oturbation patterns<br />
(e.g., vert~cal or horizontal burrows, and crawling,<br />
feedlng, and grazlng tra~ls, resident structures,<br />
or resting marks)' Bioturbation can be seen<br />
in thrn sections, rn radiographs, and zn hand speczmens<br />
and increasingly plays a szgnzficant role m the<br />
environmental assessment of a sandstone (see Part 11).<br />
Broadly speaking, the amount of bzoturbatron depends<br />
on the rate 4 sedzmentation as well as the bottom<br />
conditions o/ light, depth, and oxygen content.<br />
G. Bulk chemistry using the standard ox~des? For many<br />
years largely the rnterest of a /nu academrcs, bulk chemist~<br />
is now much easrer and cheaper to detennzne with<br />
X-ray Jluorescmce and atomic absorption and is of znterest<br />
to sedimentary geochemists for mass balance computatrons<br />
in the earth's rock rycle and rn assesszng the<br />
chemical maturity of a sandstone. In a broad way the<br />
chemzcal composrtion of a sandstone can also be related to<br />
its plate tectonrc settrng (Schab 1975).<br />
1. Si02/A1203 maturlty ratio?<br />
2. K20/Na20 tectonlc setting ratio? See Crook<br />
(1 974 p. 306-7) for an early dzscussron o/ the plate<br />
tectonrc signz$cance of bulk chemistty.<br />
11. QUESTIONS PRIMARILY ANSWERED BY THE<br />
MEGASCOPIC EXAMINATION OF OUTCROPS<br />
AND CORES AND BY THE STUDY OF WIRE<br />
LINE LOGS. Here we are interested m the megascopzc fea-<br />
tures of sands and sandstones, features which not only de/me<br />
thezr rnternal subdivrsrons, but also help deposrtional<br />
environment and geographic distnbutron uszng the concept o/<br />
a deposrtzonal sand model. Sand mudels are essentrally d+ed<br />
on the gemetly and rnternal fiatures o/ a sandstone bdy<br />
and are based on both Holocene and ancrent examples, the<br />
best usually berng a cmbrnatron a/ both, and exrst /or all<br />
the major envrronments (table 1). Idmtzficatron, use, and<br />
orientatzon of the correct sand model rs an essentral step /or<br />
e//rcrmt exploratron-of porosrty and penneabilrty and/or<br />
mzneralrzatron. Good summaty descnptzons znclude Sellty<br />
(1970), LeBlanc (1972), Rzgby and Hamblrn (1972), Shl-<br />
ton (1973), and Rerneck and Srngh's (1973) and Hays and<br />
Kana's (1 976) summary o/ mdrn terngenous envzronments.<br />
A very brie/ summary of all mapr sources rs also prwzded<br />
by Potter and Pettijohn (1977, table 7-1). Good, succrnct<br />
wervreurs are also prwrded by Walker (1976a, 19766) and<br />
Mzall (1 976).<br />
A. Geometry? Geometry alone, although rt cannot do evetythzng,<br />
can go /ar to help zdenti/y the correct model.<br />
1. Geograph~c location and trend? How far from<br />
the estimated bas~n margln and, if elongate,<br />
how or~ented, w~th respect to deposit~onal<br />
strike)<br />
2. Vertical posit~on? Does the sandstone body occur<br />
near the base, middle, or top of some larger<br />
genetlc packet?<br />
3 Length, w~dth, and thickness?<br />
4 Boundar~es and lateral equ~valents?<br />
a Upper and lower: sharp or gradat~onal'<br />
b. Lateral equ~valents? What l~thologies and environments?<br />
Vrrtually always assignment of the<br />
correct model zs best when rvrdence /rom assoczated<br />
lrthologres rs rntegrated wrth that from the sandstone<br />
Uy ztself: -<br />
B. Internal features?<br />
1. Interbedded litholog~es? What, how much, and<br />
where' Usually very helpJul rn envrronmental judgments<br />
and, because shale partrngs and beds rnterrupt<br />
Jlmu, an zmportant /actor to consrder rn reservoir engineering<br />
and posszbly even rn mmerabzatron.<br />
2. Fracture systems? Kznds, den~rty, and drstnbutron?<br />
Agazn, commonly, most srgnrficant /or reservozr geolo-<br />
gY.<br />
3. Sedimentary structures? What kinds, relat~ve<br />
abundance, and where? Answers to these questrons<br />
TABLE 1<br />
CLASSIFICATION OF SAND AND SANDSTONE BODIES<br />
(Shelton 1973, table 2)<br />
Cont~nental (nonmanne) Inrerdelra~c<br />
Barrier Island, bar, beach<br />
Alluv~al T~dal pass<br />
P~edmont T~dal flat<br />
Valley<br />
Pla~n Marme<br />
Shelf (shallow)<br />
Nearshore<br />
Offshore<br />
Coastal-parallc-rrans~t~onal Deep<br />
Estuary (alluv~al-estuarine)<br />
Delta~c<br />
Delta front and margln<br />
D~srnbutary<br />
Turbtdlry current<br />
Normal bottom current
4ne, perhaps better and easier than anything else,<br />
the internal furies 4 a sandstone body. Moreover,<br />
study of directional sedimentary structures permits us<br />
not onb to better estimate sadstone trend;, but also<br />
to help idmtif) the depositional environment and its<br />
Lydraulic regime (Potter and Pettijohn 1977).<br />
4. Texture and mass-derived properties? Does the<br />
sandstone body fine or coarsen upward? What<br />
signiticance, if any, does the size distribution<br />
have? How is the size distribution related to ce-<br />
mentation, permeability, and porosity?<br />
5. Mineral composition? See Part I.<br />
6. Macrofossils and bioturbation? Paleontology and<br />
paleoecology of macroforrils give important information<br />
on ecological and sedimentological conditions in a dep-<br />
ositional environment which the rocks alone cannot<br />
yield (Ager 1963; Imbrie and Newell 1964). Because<br />
animals have diffimt ecological requirements (sali-<br />
nity, light, temperature, wave and current energy,<br />
substrate type, and tusbidiry), different communities<br />
of animals o/im characterize certain ecologic-sedi-<br />
mentoLogic conditions (Ziegfer 196.5, Bretsky 1969).<br />
Furthermore, the modes of life of the animals and<br />
, J J<br />
their dirttibution within the community can provide<br />
more dltaiIed environmental data (Walker 1972,<br />
Rhoads et al. 1972, Thayer 1974). The type and<br />
quality of fossil preservation also rejlect depositional<br />
conditions (Gave 1964, Driscoll 1970), as well as<br />
diagenetic events (Bayd and Newel1 1972). When<br />
body fossils are lacking, a common situation in sand-<br />
QUESTION SET FOR SANDS 5<br />
1 1<br />
GLAUCONITE GLAUCO- CARBONACEOUS GLAUCONITE GLAUCONITE<br />
8 CARBONA- NlTE 8 CARBONA-<br />
CEOUS<br />
DETRITUS DETRITUS<br />
or CREVASSE<br />
SPLAY<br />
stones, trace fossils (buwows, trails, etc.), which repre-<br />
sent modes of life and are largely environmentally<br />
controlled, can yield environmental data (Sklacher<br />
1964, Crimes 1970, Fsq, 1975). Combining sedimen-<br />
tological and paleontological data nearly always im-<br />
pmes tbe definition af faris subtypes and paleo-<br />
geographic mapping (Kaufman 1967). And finally,<br />
macrofossils can act as index fossils for stratigraphic<br />
correlation (Betry and Boucot 1970, p. 29; Kennedy<br />
and Cobban 1976).<br />
a. Relative abundances of different types of fos-<br />
sils? Diversity generally increases seaward to the<br />
edge 4 a continental shelf:<br />
b. Is distribution of fossils patchy, uniform, or<br />
random? Are they concentrated within beds<br />
or on bedding planes?<br />
c. Are the fossils intact and well preserved or<br />
fragmented and worn? Molds or casts? Re-<br />
crystallized or replaced? The condition of the<br />
fossils gives information on the energy of the 40-<br />
sitional environment, on the in situ or transported<br />
nature of the fossifs, and on diag~neic mts.<br />
d. Are fossils preferentially or randomly orien-<br />
ted? Orientations of fossils zn life posztion or those<br />
transported gives information on direction ofpaleo-<br />
cu wents.<br />
e. What functional types of organisms are pres-<br />
ent? Encrusters, sediment trappers or binders,<br />
epifauna or infauna, mobile or sessile? Sus-<br />
pension feeders, deposit feeders, scavengers,<br />
4<br />
*API GR Units<br />
CARBONA-<br />
CEOUS<br />
DETRITUS<br />
DELTAIC<br />
DISTRIBUTARY<br />
REDRAWN FROM SELLEY (1976; FIG. I)<br />
FIGURE 3.-Flow chart for recognition of dcposirional environments using wire line logs (Sdley 1967, fig. 2)-a very useful modd for many diverse environ-<br />
ments of sand deposition (published by permission of the American Association of Pcttolcum Geologists and the author).
predators? Animal-sediment relations influence<br />
depasition, stabilization, and mixing of sediments.<br />
Different m& of llfe and feeding habits can indicate<br />
dflerent ecologic-sedimentologic conditions.<br />
f. Types and abundance of bioturbation?<br />
(1) mostly within beds or on bedding surfaces?<br />
(2) sizes and forms?<br />
(3) orientation: vertical, oblique, horizontal?<br />
g. Recurrent associations of fossils through a<br />
vertical sequence? Shows the shifting back and<br />
forth of environmental conditions.<br />
C. Vertical sequence and log expression? The essential,<br />
and only fairly recently recognized, key to environmental<br />
recognition, wherein grain size, beding, and sedimentary<br />
structures, and to a minor degree composition combine to<br />
fonn consistent vertical changes that have environmental<br />
significance, some good examples being those of Saitta<br />
and Visher (1968, fig. 8), Poupon et al. (1970), and<br />
Selley (1976, fig. 2). Signature on wire line logs in combination<br />
with eeometn, commd bennits environmental<br />
0 / 1<br />
judgments, especzally when combined with some knozuledge<br />
4 the position of the sandstone body in the basin (/ig.<br />
3). It is the vertical sequence-a kind 4 micm stratlgrapby<br />
that is either based on outcrop study, cores, or<br />
logs-that puts "all the . parts . together" (A4 and B) to<br />
pennit an envtronmental judgment.<br />
SEDIMENTATION SEMINAR<br />
D. Economic significance? As diverse as the economic<br />
needs of man, but nearly always relatable to primary<br />
sedimentation (gold and heavy mineral placers, super<br />
pure g h sands, coal cutouts at the base 4 fluvial<br />
channels, etc.) or to the porosig and penneabilicy system<br />
of the sandstone which in turn is commonly traceable<br />
back to original sedimentation.<br />
111. FORMAT FOR A BASIN-QUESTIONS PRIMARI-<br />
LY ANSWERED BY STUDY OF THE ENTIRE<br />
BASIN OR PERHAPS EVEN A LARGER AREA<br />
SUCH AS A CONTINENTAL MARGIN. Consid-<br />
eration of the basin as a whole-how a particular sandstone<br />
body or group of sandstone bodies relates to the entire basin-<br />
provides the widest of perspectives and thus enhances our<br />
vietqboznts for regional exploration. The questions of this sec-<br />
tion are primarily answered try wire line logs and geophysics<br />
(especially seismic sections) plus the supplemental data of out-<br />
crops and cores and some laboratory analyses. And, rather<br />
than list these as separate questions, we have found a tabu-<br />
lar format to be most useful (table 2). Such a fonat seems<br />
particularly desirable when a systematic inventory of basin<br />
facts is desired. Inventories such as table 2 provide the basis<br />
for a series of basin madels whose conceptual elements are<br />
largely identical to those of the depositional models for the<br />
major sand environments of Part 11. Spencer's (1974, p.<br />
788-802) tectonic inventory of Mesozoic and Cenozoic foM<br />
Directional Size<br />
Thickness Lithofacies Fossils structures Composition sorting<br />
\l<br />
a -<br />
\ \ 1<br />
GEOMETRY FILL DEPOSITIONAL ENVIRONMENT<br />
\I<br />
Broadly responsive to ratio of<br />
input to subsidence and only<br />
secondarily affected by climate.<br />
For sandstones, vertical profiles<br />
are most significant.<br />
PALEOGEOGRAPHY<br />
FIGURE 4.-Flow chart for basin analysis, the ultimate goal being a paleogeography for as fine a time interval as practical. Basin size and thickness, lithofacies,<br />
fossils, directional structures, composition, and size and sorting are the facts from which all the orher elements of a basin analysis are derived.<br />
a<br />
T<br />
-<br />
11<br />
PALEOCURRENTS<br />
Structure maps,<br />
mineral associations<br />
and size gradients<br />
a<br />
BASIN TYPE - PALEOCIRCULATION<br />
11<br />
PATTERN<br />
1
Time pan<br />
Properties<br />
Stratigraphic range and possible worldwide megasequence<br />
Geometry and barin rype<br />
Shape, area, volume, and maximum thickness.<br />
Lithic fill: Kinds, proportions, and distribution of major depositional<br />
environments and systems (implying kinds, proportions, and distribu-<br />
tion of major facies and lithologies and sandstone types).<br />
Composition: Mineralogy, texture, and petrographic types of sandstones<br />
and other major lithologies.<br />
Paleocurrents: Integrate depositional systems and help predict major<br />
sedimentary trends.<br />
Structural sgie<br />
Predepositional: May be hard to assess, but commonly the chief control<br />
on basin geometry and regional paleoslope.<br />
Syndepositional: Abundance and magnitude of regional arches, hinge<br />
lines, and/or growth faults plus unconformities.<br />
Postdepositional: May consist of major fold systems and/or thrusting or<br />
be chiefly normal faulting, or the basin may be essentially undeformed<br />
with only broad regional arches.<br />
QUESTION SET FOR SANDS<br />
TABLE 2<br />
FORMAT FOR BASIN STUDY: PROPERTIES AND METHODS<br />
Methods<br />
Paleontology, especially micropaleontology in the Phanenoic; in the Pre-<br />
cambrian primarily radioactive dating.<br />
Outcrop and subsurface mapping plus seismic and gravity study<br />
Outcrop and subsurface stratigraphic correlation and paleontology, especially<br />
micropaleontology plus systematic environmental analysis from both outcrop<br />
and subsurface. Possible use of seismic stratigraphy.<br />
Mostly thin section and binocular petrology plus some X-ray identification.<br />
Primarily the systematic mapping of crossbeds and sole marks in outcrop sup-<br />
plemented by facies distribution and mineral provinces as well as possibly ori-<br />
ented cores.<br />
Seismic, gravity, and subsurface geology.<br />
Subsurface stratigraphy, abundance, and magnitude of regional and local<br />
unconformities plus seismic sections.<br />
As above plus field mapping.<br />
T~tonic jetting<br />
Summarizes basin type and relates to possible plate tectonic schemes. Based on nature of lithic fill, structural style, and relation to continental<br />
margin. Sandstone composition can be helpful in assessing possible plate tectonic<br />
setting in pre-Mesozoic basins.<br />
Paleoclimate<br />
Semiqualitative to qualitative identification of broad worldwide climatic Climatically sensitive sediments (coals, evaporites, diamitites, and carbonates),<br />
zones. and fossils plus evidence from continental drift and paleomagnetics.<br />
Closely related to economic potential of basin and depends on burial Organic and inorganic evidence, the former including coal rank, phytoclasts,<br />
depth and geothermal gradient and thus ultimately on tectonic history plus kerogen and conodont color; the latter including crystallinity of illite,<br />
percent expandables in illite, zeolites, and metamorphic mineral assemblages.<br />
Economic<br />
Depends on objective, but nearly always involves volume and distribu- All of above plus geochemical study of organic content (for petroleum) and<br />
tion of host sediment and/or source rock in combination with local mineralization.<br />
and/or regional structure.<br />
belts is a good example of the vast quantity of relevant information<br />
that ic obtainable for basins. And how should<br />
these elements be put together? A simplified JMU chart (fig.<br />
4) gives an mewiew of how the subparts of the firmat are<br />
integrated- the ultimate objective being a careful paleogeography<br />
fir as fine a time slice as possible. A brief recent<br />
summary of developments in basin analysis and beyond, including<br />
much of the relevant literature, is given by Potter<br />
and Pettijohn (1977, p. 340-63), while Vannty (1977) provides<br />
a very interesting geamorphological appraisal.<br />
ACKNOWLEDGMENTS<br />
We are indebted to C. K. Seyfried of Texaco, Inc., Tulsa,<br />
Oklahoma, for his helpful comments.<br />
REFERENCES CITED<br />
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371 p.<br />
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of the use of undulatory extinction and polycrystallinity in detrital<br />
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82.<br />
Berner, R. A., 1971, Principles of chemical sedimentology: New York,<br />
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lurian rocks: Geol. Soc. Amer., Spec. Paper 102. 289 p.<br />
Bokman, J., 1952, Clastic quartz particles as indices of provenance: Jour. Sed.<br />
Petrol., v. 22, p. 17-24.<br />
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14.<br />
Bretsky, P. W., Jr., 1969, Evaluation of Paleozoic benthic marine invertebrate<br />
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Wiley & Sons, p. 377-87.<br />
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in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Liverpool, See1<br />
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Crook, K. A. W., 1974, Lithogenesis and geotectonics: The significance of<br />
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Jr., and Shaver, R. H. (eds.), Modem and ancient geosynclinal sedimentation:<br />
Soc. Econ. Pdeont. Mineral., Spec. Pub. 19, p. 304-10.<br />
Dickinson, W. R., 1969, Evolution of calc-alkaline rocks in the geosynclinal<br />
system of California and Oregon: in McBirney, A. R. (ed.), Pre<br />
ceedings of the Andesite Conference: Oregon Dept. Geol. and Min.<br />
Ind., p. 151-56.<br />
, 1970, Interpreting detrital modes of graywacke and arkose: Jour. Sed.<br />
Petrol., v. 40, p. 695-707.<br />
Driscoll, E. G., 1970, Selective bivalve destruction in marine environments: a<br />
field study: Jour. Sed. Petrol., v. 40, p. 898-905.<br />
Folk, R. L., 1968a, Petrology of sedimentary rocks: Austin, Hemphill's Bookstore,<br />
170 p.<br />
, 1968b, Bimodal supermature sandstones: Product of the desert floor:<br />
23rd Int. Geol. Congress, Proc. Ser. 8 (Genesis and classification of<br />
sedimentary rocks), p. 9-33.<br />
Frey, R. W. (ed.), 1975, The study of trace fossils: New York, Springer-Vet-<br />
~ -<br />
lag, 562 p.<br />
Galloway, W. E.. 1974, Deposition and diagenetic alteration of sandstone in<br />
northeastern Pacific arc-related basins: Implications for graywackc genesis:<br />
Geol. Soc. Amer. Bull., v. 85, p. 379-90.<br />
Glaister, R. P., and Nelson, H. W., 1974, Grain-size distributions, an aid in<br />
facies identification: Bull. Canadian Petrol. Geol., v. 22, p. 203-40.<br />
Glover, J. E., 1963, <strong>Studies</strong> in the diagenesis of some Western Australian<br />
sedimentary rocks: Jour. Royal Soc. Westem Australia, v. 46, pt. 2, p.<br />
33-56.<br />
Hays, M. O., and Kana, T. W. (eds.), 1976, Terrigeneous clascic depositional<br />
environments: Univ. South Carolina Coastal Research Div.-Dept. <strong>Geology</strong>,<br />
Tech. Rept. 11-CRD, pts. I and 11, 131 and 171 p.<br />
Helgeson, H. C., 1968, Geologic and thermodynamic characteristics of the<br />
Salton Sea geothermal system: Amer. Jour. Sci., v. 266, p. 129-66.<br />
Hubert, J. F., 1962, A zircon-tourmaline-rutile maturity index and the interdependence<br />
of the composition of heavy mineral assemblages with the<br />
gross composition and texture of sandstones: Jour. Sed. Petrol., v. 32,<br />
p. 440-50.<br />
Imbrie, J., and Newell, N. D. (eds.), 1964, Approaches to paleoecology:<br />
New York, John Wiley & Sons, 432 p.<br />
Kauffman, E. G., 1967, Coloradoan macroinvertebrate assemblages of central<br />
westem interior, United States: in Kauffman, E. G., and Kent, H. C.<br />
(eds.), Paleocnvironments of the Cretaceous seaway in the western interior:<br />
A Symposium, Colorado Sch. Mines, Spec. Pub., Prcprints, p. 67-<br />
143.<br />
Kennedy, W. J., and Cobban, W. A., 1976, Aspects of ammonite biology,<br />
biogeography, and biostratigraphy: Palaeont. Assoc., Spec. Papers in<br />
Paleo., No. 17, 94 p.<br />
Klovan, J. E., 1970, The use of factor analysis in determining depositional<br />
environments from grain-size distributions: Jour. Sed. Petrol., v. 36, p.<br />
115-25.<br />
Krinsley, D., and Margolis, S., 1969, A study of quartz grain sand surface<br />
texmres with the scanning electron microscope: Trans. New York<br />
Acad. Sci. Ser. 11, v. 31, p. 457-77.<br />
LeBlanc, R. J., 1972, Geometry of sandstone reservoir bodies: in Cook, T. D.<br />
(ed.), Underground waste management and environmental implications:<br />
Amer. Assoc. Petrol. Geol., Mem. 18, p. 133-89.<br />
Miall, A. D., 1976, Facies models-4. Deltas: Geoscience Canada, v. 3, p.<br />
215-17.<br />
Middleton, G. V.. 1976, Hydraulic interpretation of sand size disrributions:<br />
Jour. Geol., v. 84, p. 405-26.<br />
Murray, J. W., 1973, Distribution and ecology of living benthic foraminiferids:<br />
New York, Crane, Russak, and Co., 274 p.<br />
Orme, G. R., 1974, Silica in the Visean limestone of Derbyshire, England:<br />
Proc. Yorkshire Geol. Soc., v. 40, p. 63-104.<br />
Orme, G. R., and Brown, W. W. M., 1963, Diagenetic fabrics in the Avonian<br />
Limestones of Derbyshire and North Wales: Proc. Yorkshire<br />
Geol. Soc., v. 34, p. 51 -66.<br />
SEDIMENTATION SEMINAR<br />
Pettijohn, F. J., Potter, P. E., and Siever, R., 1972, Sands and sandstones:<br />
New York, Springer-Valag, 618 p.<br />
Pflum, C. E., and Fredrichs, W. E., 1976, Gulf of Mexico deep-water foraminifen:<br />
Cushman Found. for Foram. Res., Sp. Pub. 14, 124 p.<br />
Pittman, E. D., 1970, Plagioclase fcldspr as an indicator of provenance in<br />
sedimentary rocks: Jour. Sed. Petrol., v. 40, p. 591-98.<br />
, 1972, Diagmesis of quartz in sandstones as revealed by scanning<br />
clectron microscopy: Jour. Sed. Petrol., v. 42, p. 507-19.<br />
Potter, P. E., and Mast, R. F., 1963, Sedimentary structures, sand-shape fabrics<br />
and permeability: Jour. Geol., v. 71, p. 441-71.<br />
Potter, P. E., and Pettijohn, F. J., 1977, Paleocurrents and basin analysis-up<br />
date: New York, Springer-Valag.<br />
Poupon, A., Clavier, E.. Dumanoir, J., Gaymard, R., and Mi*, A,, 1970, Log<br />
analysis of sand-shale scqumces: A systematic approach: Jour. Petrol.<br />
Tech., July, p. 867-81.<br />
Reading, H. G., 1972, Global tectonics and the genesis of flysch successions:<br />
24th Int. Geol. Congress, Sect. 6 (Stratigraphy and sedimentology), p.<br />
59-66 .,<br />
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New York, Springer-Valag, 439 p.<br />
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Upper Cretaceous (Maestrichtian) bivalve assemblages from South Dakota:<br />
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Rigby, J. K., and Hamblin, W. K., 1972, Recognition of ancient sedimentary<br />
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of the Bluejacket-Bartlesville Sandstone, Oklahoma: Oklahoma<br />
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N. D. (eds.), Approaches to paleoccology: New York, John Wiley<br />
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Springer-Verlag, 471 p.<br />
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Recognition and influence on reservoir properties and paleocnvironmental<br />
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Ziegler, A. M., 1965, Silurian communities and their environmental significance:<br />
Nature, v. 27, p. 270-72.
A New Species of Arroyocrinus (Inadunata) from the<br />
Park City Formation (Upper Permian) of Utah<br />
H. L. STRIMPLE AND . F. MILLER<br />
Uniwrsi!y o/ lwa, Iwa Ciry, Iowa 52240, an d Soutbw~t M~~~oun' State Uniwr~i/y,<br />
Spring/;eId, Missouri 63 102<br />
ABSTRACT.-A singlc well-prcscrvcd cup with a rigid tcgmcn, or anal sac, prc- Five radials very large, with proximal terminations well above<br />
xrving a singlc axillary first primibrach in C ray is described as Arroyorrinus the basal plane of ;he cup; buter ligamental area well devel-<br />
~tukrsj, n. sp. Thc spccics is from thc Fnnson Member, Park City Formation,<br />
'ped Primibrachs I axillary* low*<br />
Upper Permian cxpovd in Dry Crcck Canyon, Wasatch Mountains, northeast<br />
rather lateral<br />
of Salt Wtc City, Utah. This is the first Permian crinoid to be dcscribcd sides, tumid. Anal sac broad, domelike, but short, composed<br />
from Utah. ~rrobrrinus was prcviousl~ rcported from only a sinprlc localicy of large rigidly united plates. Proximal columnals round. alin<br />
Nevada. ~ l o k rcscmblancc; of both sp;cics of ~rro~ocrinw to-TCXUC~~~U; most YoveGng' infrabasais. Deep crenellae the perimeter<br />
suggest that thc formcr should be clasvd with thc Tcxacrinidac rather than<br />
of the articular facet between columnals; lumen small, round.<br />
with the Ampelocrinidac.<br />
INTRODUCTION<br />
The specimen described in the paper was discovered by a<br />
geology student and given to Dr. W. Lee Stokes, <strong>University</strong><br />
of Utah, in about 1949. It was found in talus on the south-<br />
king slope of Dry Creek Canyon in the Wasatch Mountains<br />
northeast of Salt Lake City almost certainly in the northeast<br />
corner of section 33, T.l N, R.l E, Salt Lake Base and Meri-<br />
dian.<br />
The rocks exposed here belong to the upper half of the<br />
Franson Member of the Park City Formation. The entire<br />
south-facing canyon wall at this locality is very nearly a dip<br />
slope in the Franson Member with rocks of no other unit<br />
present. There are many fossils, mostly poorly preserved. The<br />
precise age is somewhat in doubt, but is certainly either late<br />
Guadalupian or early Ochoan. In any event the strata here<br />
are only a few hundred feet below the base of the Triassic<br />
and may belong near the close of Permian deposition in the<br />
region. No other Permian crinoids have yet been described<br />
from Utah; this is in stark contrast to the rich Permian cri-<br />
noid fauna reported for southern Nevada by Lane and Web-<br />
ster (1966). Other crinoids are known to occur in the Fran-<br />
son Member, but cups are exceedingly rare.<br />
Dr. Stokes kindly made the specimen available to us for<br />
description, as well as providing the information above. The<br />
species has been named Aryocrinus stokesi, n. sp., in his hon-<br />
or.<br />
SYSTEMATIC PALEONTOLOGY<br />
Subclass INADUNATA Wachsmuth & Springer, 1885<br />
Order CLADIDA Moore & Landon, 1943<br />
Suborder POTERIOCRININA Jaekel, 1918<br />
Superfamily TEXACRINACEA Strimple, 1961<br />
Family TEXACRINIDAE Strimple, 1961<br />
Genus ARROYOCRINUS Lane & Webster, 1966<br />
Arroyorrinus stokesi, n. sp.<br />
Figures 1, 2<br />
Description.-Dorsal cup bowl-shaped with broad, deep basal<br />
concavity; cup plates, other than infrabasals, tumid with im-<br />
pressed sutures. Infrabasals small, apparently fused, extending<br />
only slightly beyond the round proximal columnal in a sub-<br />
horizontal plane. Five large basals flex into the basal con-<br />
cavity; their proximal portions form a sizable funnellike in-<br />
vagination; posterior (CD) basal longer than other basals<br />
with distal end truncated for reception of a single anal plate.<br />
Discussion.-Awqyocrinus stokesi is more advanced than A. po-<br />
penoei, type species of the genus, in the positioning of anal<br />
plates in the CD interray. In the latter species, the radianal<br />
lies obliquely across the upper surface of CD basal with anal<br />
X and RX respectively to the left and right above. Both anal<br />
X and RX in A. popenoei extend above the cup summit, but<br />
proximal portions reach well below the distal edge of the<br />
cup. The lower right portion of the radianal maintains con-<br />
tact with BC basal. A. stokeji has only two anal plates in the<br />
cup, but the RX, which is much reduced in size, still main-<br />
tains a narrow contact with the radianal. However, the radi-<br />
anal in this species is much reduced in size, has lost contact<br />
with BC basal, and has a wide diagonal contact with anal X,<br />
which plate is almost ejected from the cup.<br />
Although arms are not preserved above the primibachs in<br />
the present specimen, it is needful to discuss them in con-<br />
junction with the disposition of the genus. Lane and Web-<br />
ster (1966, p. 40) were aware of the unique nature of the<br />
FIGURE I.-Photographs of Arrqorn'nns stokrsi n. sp.. holorypc (SUI 44080)<br />
viewed from A. posterior, B. base, C. anterior, X2.7.
10 STRIMPLE AND MILLER<br />
arms of Arrayoctinus, that is, their close opposition when the<br />
arms are closed and their broad short brachials. Neither char-<br />
acteristic is found in Plummerirrinus (Pennsylvanian) which is<br />
chronologically the closest related genus. Other genera of<br />
Pennsylvanian age which have arms in close opposition and<br />
broad short uniserial brachials are Texacrinus and Ulrichicrinus.<br />
Moapocrinus Lane and Webster (1966), which occurs with<br />
Arrcryocrinus, has a similar structure although the brachials are<br />
somewhat modified so that one half of each brachial is con-<br />
siderably higher then the other half. Short brachials are an al-<br />
ternative method of producing closely packed pinnules; many<br />
contemporaneous genera are biserial. Moapocrinus is currently<br />
considered to belong to the Cr~m~ocrinidae.<br />
Moore, Lane, and Strimple (1973, p. 21) assigned Arryo-<br />
crinus to the Ampelocrinidae. Relationship with ampelocri-<br />
FIGURE 2. -Camera lucida drawings of holotype (SUI 44080) of Arroyorrinur<br />
stokesl n. sp.; a. base, b. posterior, X3.2.<br />
nids, all of which have two or more primibachs in all rays, is<br />
even more unlikely than relationship with pachylocrinids.<br />
The low cup with basal invagination, advanced anal plates<br />
(radianal in contact with D radial), together with broad, low<br />
uniserial brachials suggest close affinity with Texacrinus as<br />
exemplified by Texascrinus con{onnis Strimple (1961). Hence,<br />
Arryocrinus is here transferred to the Texacrinidae. Possible<br />
relationship with Ulrirhicrinus is not entirely ruled out but<br />
from presently known evidence does not seem to be a fea-<br />
sible alternative. To derive Arrovacrinus from Texacnus<br />
would involve merely reduction in arm branching and migra-<br />
tion of the second bifurcation of the arms toward the cup.<br />
The same changes in arm structure would be required to de-<br />
rive Arryocrinus from a genus like Plummerirrinus or from Ul-<br />
richicrinus ramosus Strimple & Watkins (1969), both of the<br />
latter are of Pennsylvanian age; Texacrinus is more nearly<br />
contemporary to the known occurrences of Arryocrinus. Ad-<br />
ditionally, this alternative would also require modification<br />
from comparatively high main arm brachials to quite narrow<br />
ones.<br />
Measurmrnts o/ holotype in millimeters<br />
Height of cup (anterior)<br />
Width of cup (posteroanterior)<br />
Width of cup (right to left)<br />
Width of infrabasal circlet<br />
Diameter of proximal columnal<br />
Length of AB basal<br />
Width of AB basal<br />
Length of A radial<br />
Width of A radial<br />
Maximum length of anal plate<br />
Minimum length of anal plate<br />
Maximum width of anal plate<br />
0ccurrmce.-Franson Member, Park City Formation, late Gua-<br />
dalupian or early Ochoan, Upper Permian; Dry Creek Can-<br />
yon, NE corner sec. 33, T.l N, R.l E, northeast of Salt Lake<br />
City, Utah.<br />
Holotype. - Reposited at the <strong>Geology</strong> Depart men t Repository,<br />
The <strong>University</strong> of Iowa, Iowa City (SUI 44080).<br />
ACKNOWLEDGMENTS<br />
We are grateful to N. Gary Lane, Indiana <strong>University</strong>,<br />
Bloomington, and to T. J. Frest, The <strong>University</strong> of Iowa,<br />
Iowa City, for critical perusal of this paper.<br />
REFERENCES<br />
Lane, N. G., and Webster. G. D., 1966. New Permian crinoid fauna from<br />
southern Nevada, Univ. California Geol. Sci. v. 63, 87 p. illus.<br />
Moore, R. C., Lane, N. G., and Strimple, H. L., 1973. Classification of flex.<br />
ible and inadunate crinoids: in Moore and Strimple, Univ. Kansas, Pa-<br />
leontological Contr., Art. 60: 15-31<br />
Srrimple, H. L., 1961. Late Desmoinesian crinoid faunule from Oklahoma,<br />
Okla. Geol. Sur. Bull. 93. 189 p.<br />
Strimple, H. L, and Warkins, W. T., 1969. Carboniferous crinoids of Texas<br />
with stratigraphic ~mplications, Palaeontographica Americana,<br />
6:137-275.
Additional Specimens of the Hypsilophodontid Dinosaur Dryosaurzls altzls<br />
from the Upper Jurassic of Western North America<br />
I Department of Biologv, Univerrity o/ Bridgeport, Bridgeport, Connecticut 06602.<br />
Department of Biology, Westchester Cummunity College, VaLbaIla, New York 10191<br />
Eurtb Science Museum, <strong>Brigham</strong> <strong>Young</strong> Univerrity, Provo, Utah 84602.<br />
Ass-.-Specimens of the hypsilophcdontid dinosaur (Reptilia: Orni- seum of Natural History; Dr. J. H. Ostrom, Peabody Muthischia:<br />
Ornithopoda) Dtyoraunrs altur (Manh) are described from the Mor- seum of Yale <strong>University</strong>; and Dr. T. E, white Mr. J,<br />
rison Formation (Upper Jurassic) of Colorado, Utah, and Wyoming. As Adams of Dinosaur National Monument. NSF grant DEB<br />
shown by these specimens, the postcranial anatomy of Dtyoraurur altur<br />
(Marsh) is very similar to that of Dfyosaurur lettowvorbecki Pompeckj from 76-09769 to P. M. Galton partly supported this work and<br />
the Tendaguru Formation (Upper Jurassic) of Tanzania, East Africa. provided $250 toward the publication of this paper.<br />
INTRODUCTION<br />
The purpose of this paper is to describe four specimens<br />
(AMNH 834, CM 1949, CM 21786, DNM 1016)* of an or-<br />
nithopod dinosaur (Reptilia: Ornithischia) from the Morri-<br />
son Formation (Upper Jurassic) of Colorado, Utah, and<br />
Wyoming. Comparisons with YPM 1876 (holotype of Lao-<br />
saurus altus Marsh, 1878, the type species of genus Dryosaurus<br />
Marsh, 1894) show that these four specimens are referable to<br />
the hypsilophodontid Dtyosaums altus (Marsh). A summary<br />
of previous work on hypsilophodontid dinosaurs from the<br />
Upper Jurassic of North America is given by Galton and<br />
Jensen (1973: 137-38).<br />
Data on Specimens<br />
AMNH 834.-From Bone Cabin Quarry, Medicine Bow<br />
anticline, Wyoming; specimen consists of one cervical and<br />
several fragmentary dorsal and caudal vertebrae; right scapula,<br />
coracoid. humerus, ilium, ischium and pubis, both femora,<br />
incomplete left tibia, pes and some phalanges (figs. 1A-D,<br />
2A-D, 3F, 4A-C, 5A-B). Length of right femur 222 mm and<br />
original length of animal about 2.0 m.<br />
CM 1949.-Collected by W. H. Utterback in 1905 from<br />
the Elk Mountains near Brown's Ranch, Johnson County,<br />
Wyoming; specimen consists of several dorsal and caudal ver-<br />
tebrae, right ilium, femur and tibia (figs. 31, 4D-E, 5N-0).<br />
Length of tibia 496 mm and original length of animal about<br />
3.8 m.<br />
CM 21786.-Collected by J. L. Kay and A. C. Lloyd in<br />
1955 from Lily Park, Moffat County, Colorado; specimen<br />
consists of 41 vertebrae, incomplete left ilium, ends of all<br />
long bones (left tibia with intact calcite core, length 356<br />
mm, and original length of animal about 2.7 m) with both<br />
pes almost complete (figs. 1E-V, 2E-H, 3G-H, 4F-0, 5C-M).<br />
DNM 1016.-Collected by J. Adams from the exhibit cliff<br />
at Dinosaur National Monument near Jensen, Uintah Coun-<br />
ty, Utah (White 1964, fig. 1); left ilium (fig. 3A-E), length<br />
of original animal about 2.4 m.<br />
ACKNOWLEDGMENTS<br />
We thank the following people for all their assistance<br />
while studying specimens under their care: Dr. D. S. Ber-<br />
man, Carnegie Museum; Dr. E. S. Gaffney, American Mu-<br />
DESCRIPTION AND COMPARISONS<br />
No attempt is made to describe the specimens in detail<br />
because there are several good descriptions of the bones of<br />
cursorial ornithopods in the literature. Instead comparisons<br />
have been drawn primarily with the following taxa: the fab-<br />
rosaurid Fabrosaurus australis (Thulborn 1972) from the Up-<br />
per Triassic of Lesotho, southern Africa; the hypsilophodon-<br />
tids Hypsilopbodo h i (Galton 1974) from the Lower<br />
Cretaceous of England; Dysalotosaurus lettow-vorbecki (Janensch<br />
1955) from the Tendaguru Formation (Upper Jurassic) of<br />
Tanzania, East Africa, and Otbnielia (Galton 1977, based on<br />
Nanosaurus rex Marsh, 1887; see Galton & Jensen 1973) from<br />
the Morrison Formation of western North America; and the<br />
iguanodontid Camptosaurus dispar (Gilmore 1909; the several<br />
Morrison species described are probably all referable to C. dis-<br />
bar) from western North America. Unless stated to the con-<br />
1 ,<br />
trary, data for comparisons with these taxa are taken from<br />
the papers indicated above.<br />
Vertebral Column<br />
Using the vertebral column of Hypsilophadon foxii (Galton<br />
1974, figs. 19-22) as a guide, the vertebrae of Dryosaunrs represented<br />
by centra in CM 21786 (fig. 1E-V) are identified as<br />
shown. The two cervical centra (fig. 1E-H) are tentatively<br />
identified as cervicals four and seven, with the seventh showing<br />
a stouter medioventral keel than does the fourth (fig. IF,<br />
H). A well-preserved cervical of Dvosaurus (fig. 1A-D) is<br />
tentatively identified as the ninth, and presumably it is the<br />
last of the cervical keels and, on the basis of Hypsilaphodon,<br />
are identified as dorsals one and three. The remaining seven<br />
centra are tentatively identified as shown (fig. 1J-M). The<br />
dorsal centra of CM 21786 increase in width passing posteriorly<br />
to culminate in a heavy, squat centrum that is wider<br />
than long (fig. IN, O), and clearly this is the last dorsal.<br />
The sacrum of Dryosaurus probably consisted of six vertebrae<br />
as in Hvbsilobbodm. The last four are reserved in CM 21786<br />
L 1<br />
(fig. 1P; first four vertebrae, unnatural hyperflexion between<br />
sacrals 3 and 4 not compensated for). In the caudal series<br />
(fig. 1P-V) the first chevron was borne between the centra<br />
of the first two caudals as indicated by the presence of ventral<br />
articular facets. Starting with about the twentieth caudal,<br />
the transverse process is represented by a small ridge on the<br />
side of the centrum (fig. 1SV).<br />
*Institutional namcs urcd in this ppcr have brm abbm~arcd as follows: AMNH, American Muvum of Narunl Hisrory, New York, CM, Clrncgrc Mumm of Narunl History, Pirrsbuph; DNM, Dinoraur<br />
Narlonal Monument Quarry. Jmun. Utah; YPM. Peabody Muuum, Yllc Un~verury, N m Havcn<br />
11
12 SHEPHERD, GALTON, AND JENSEN<br />
Pectoral Girdle<br />
The scapula and coracoid (fig. 2A) of Dryosaurus<br />
(AMNH 834) are not well preserved, but are typically hypsi-<br />
lophodontid in form. The ratio of the maximum length of<br />
humerus to that of scapula is 0.7 and, judging from the<br />
measurements given by Gilmore (1925), the corresponding<br />
ratio for another specimen of Dysaurus (CM 3392) is about<br />
0.8. In Hypsil~pbodon, Othnielia, Dysalotosaurus, Thescelosaurus<br />
neglectus (Gilmore 1915) and Parksosaurus warreni (Parks 1926,<br />
as Tbescelosaurus warreni), this ratio is 1.0. The scapula of<br />
DysaIotosaums, as figured by Janensch (1955), is slightly<br />
shortec than the humerus, but with the anteroventral process<br />
for the clavicle restored as in other hypsilophodontids, the<br />
scapula and humerus of Dysalotosaurus are of equal length.<br />
Fore Limb<br />
The deltopectoral crest of the humerus (fig. 2D, E) is<br />
low but stout as in Othnielia, Dysalotosaum, Camptosaurus,<br />
and in young individuals of Hypsillophodon, rather than high<br />
and slender as in mature individuals of Hypsilopbodon The anterior<br />
aspect of the distal outer condyle of D~yo~auru~ (CM<br />
21786) is flat with a groove on its median surface (fig. 2E,<br />
H). The form of this condyle is the same as in Dysalotosaurus<br />
(Janensch 1955, fig. 34d) and is in contrast to the wellrounded<br />
condyles of the humeri of Othnielia, Hypsilopbdon<br />
and Camptosaurus. The distal end of the humerus of AMNH<br />
834 is badly damaged, but the form of the condyles of YPM<br />
1876, the holotype of Dtyosaurus altus, are identical to those<br />
of CM 21786. Posteriorly in CM 21786 there is a well-defined<br />
intercondylar groove (fig. 2F, H) with a foramen at the end<br />
of the indented nonarticular surface (fig. 2F, H). Only the<br />
ends of the radius and ulna of CM 21786 are preserved and,<br />
although flattened, are similar to those of other hypsilophodontids.<br />
Pelvic Girdle<br />
The ilia of AMNH 834 (fig. 3F), CM 1949 (fig. 31),<br />
DNM 1016 (fig. 3A-E), and the posterior portion of CM<br />
21786 (fig. 3G, H) are hypsilophodontid in form. They differ<br />
from the ilia of Hypsilophhodo (Galton 1969, 1974) in being<br />
proportionally low in lateral view (fig. 3B, F, G, I) with a<br />
much broader brevis shelf (fig. 3C, D). However, the brevis<br />
shelf of DNM 1016 (fig. 3A, D) and its preserved proximal<br />
portion in AMNH 834 (fig. 3F) are as in the specimens re-<br />
ferred to Dlyosaurus by Gilmore (1925, fig. 5) and to Dysa-<br />
lotosaurus by Janensch (1955, pl. 13, fig. 19). The brevis shelf<br />
is wide, thin, and at an acute angle to the main body of the<br />
ilium (fig. 3C) to give the V-shaped appearance noted by<br />
Gilmore (1925). Although damaged, the brevis shelf of CM<br />
1949 was obviously thin and wider than the main body of<br />
the ilium. The form of the posterior part of the main body<br />
of the ilium is identical in the ilia of DNM 1016 (fig. 3A-<br />
E), AMNH 834 (fig. 3F), CM 1949 (fig. 31), CM 21786 (fig.<br />
3G), YPM 1884, and those of Dysalotosaurus. The posterior<br />
portion of the ilium becomes very broad and contrasts with<br />
the thinness of the brevis shelf. In this respect these speci-<br />
mens differ from Hypsilophodon and Othnielia in which the<br />
posterior end is much deeper, and the termination is gently<br />
rounded. The dorsal edges of AMNH 834 and DNM 1016<br />
have a distinct lateral bevel (fig. 3B, F, G). Posteriorly this<br />
beveled surface becomes deeper to include most of the height<br />
of the ilium. This feature is also shown quite clearly in the<br />
ilia of Dlyosaurus (YPM 1884 and Gilmore 1925, fig. 6) and<br />
Dysalotosaurus Uanensch 1955, fig. 37a). The posterior surface<br />
of the ilium of CM 21786 (fig. 3G, H) has a matt finish,<br />
and in life this part was covered in cartilage.<br />
The ischium of Dtyosaurus (fig. 3F) has a proximally<br />
placed obturator process, and posterior to it the two ischia<br />
are in contact for the rest of their length. The distal half of<br />
FIGURE I.-D~osa~rm<br />
aLtu~, referred specimens, vertebrae X M. A-D.-Ninth cervical vertebra, AMNH 834, in A, lateral; B, anterior; C, dorsal; D, ventral<br />
views; E-V.-vertebral centra of CM 21786: E, cervical 4 in lateral view; F, as E in ventral view; G, cervical 7 in lateral view with posterior half sec-<br />
tioned along midline; H, cervical 7 in ventral view; 1-0, dorsal vertebrae: I, dorsal 1 in lateral view; J, dorsals 3 to 5 in lateral view; K, dorsal 7 in lat-<br />
eral view; I, as K in ventral view; M, dorsals 10 to 12 in lateral view; N, last dorsal in lateral view; 0, as N in ventral view; P, three sacral vertebrae<br />
conjoined with cando-sacral vertebrae; Q-V, caudal vertebrae in lateral view, tentatively identified as follows: Q, 9; R, 15; S, 20 to 27; T, 31 and 32; U,<br />
36 and 37; V, 42. Scale line represents 10 cm.
the ischium is bar-shaped (fig. 3F, sections) and gently<br />
curved in lateral view (fig. 3F). The ischia of Dryosaurus<br />
(Marsh 1896, pl. 55, fig. 4), Dysalotosaurus Uanensch 1955, pl.<br />
13, figs. 21, 22) and, apart from the distal half being more<br />
curved with the end more expanded, the ischia of Camp-<br />
touurus (Gilmore 1303, 1912) are also very similar. In Oth-<br />
nielia, Parksosuurus (Parks 1926), and Thescehaums (Gilmore<br />
1915) the obturator process is also proximally placed, but the<br />
distal half of the ischium is dorsoventrally flattened and<br />
bladelike. This is also the case in the ischia of Hypsilophodrm<br />
in which the obturator process is at midlength (Galton 1969,<br />
1974).<br />
The preserved part of the right pubis (fig. 3F) of Dryo-<br />
saurus is similar to the corresponding region of the pubis of<br />
YPM 1876 (Marsh 1896, pl. 55, fig. 4), Othnielia, Dysaloto-<br />
saums, and Hypsilophodon In Dlyosaurus (AMNH 834, YPM<br />
1876) and Othnzelid the prepubic process is long and in<br />
marked contrast to the short and sharply pointed prepubis, as<br />
figured by Marsh (1894, 1896) for Laosaurus cmors, and to<br />
the very short prepubic process of Fahrosaurus.<br />
Hind Limb<br />
The femora of hypsilophodontids are the most diagnostic<br />
postcranial bones for taxonomic identification. The femora of<br />
CM 21786 (fig. 4J-O), AMNH 834 (fig. 4A-C), and CM<br />
1949 (fig. 4D, 50) are almost identical to that of YPM 1876<br />
(Galton 1975, fig. 2G-L), the holotype of Dryo~aurus altus. In<br />
particular all the femora show the following combination of<br />
characters: a deep cleft between the greater and lesser tro-<br />
chanters (fig. 4A, B, D, J), the fourth trochanter is on the<br />
HYPSILOPHODONTID DRYOSAURUS ALTUS 13<br />
FIGURE ~.-DTDJ~U?WJ aItw~, pcctonl girdlc and forelimb, rcfcrrcd spccimens.<br />
A, right scapula and concoid in latcnl view, AMNH 834 X0.38, dahcd<br />
linc based on imp~ssion in plastcr jackct into which spccimcn fits.<br />
B, dorsal rib, AMNH 834, X0.38; C-D, right humcms, AMNH 834,<br />
X0.38 in C, antcrior and D, medial vicars; E-H, right humcms CM<br />
21786, X0.3 in E, antcrior vicar; F, postcrior view of distal cnd; G,<br />
medial vicar of distal end; H, distal end. c, capimlum; C, concoid; cf,<br />
concoid fonmcn; cl, facct for clavicle; d, dcltcpcctonl crcst; g, glcnoid<br />
cavity; i, inner condylc; o, outcr condylc; SC, scapula. Scalc lincs rcprcscnt<br />
5 crn.<br />
FIGURE 3.-Dryosaurur altur, rcfcrrcd specimens, pclvic girdle. A-E.-Ilium DNM 1016, X0.25 in A, vcnml; 8, Iatcnl; C, postcrior; D, dorsal; E, medial<br />
views; F, pclvic girdle of AMNH 834 in latcnl vicw, X0.5; G, latcral and H, postcrior vicws of postcrior portion of ilium, CM 21786, X0.25; I, ilium,<br />
CM 1949 in latcnl vicw X0.125. Scalc linc rcprcscnts 20 cm for I, 10 cm for A-E, G-H, and 5 cm for F. a, acctabulum; ap, antcrior process; b, bmis<br />
shclf; i, ixhiadic had; if, area for M. iliotibialis; IL, ilium; IS, ixhium; P, pubis; p, pubic pcdunclc; po, postpubic rod; pp, prcpubic rod or antcrior<br />
proca; 1, 2, 3, 4, attachmcnt arms for sacnl ribs 1 to 4 (area for 5 brokcn).
14 SHEPHERD, GALTON, AND JENSEN<br />
proximal half of the femur (fig. 4A, B, D), the deep depres-<br />
sion for the M. caudi-femoralis longus (Galton 1969) is set<br />
well on the shaft (fig. 4A), the distal end is nearly square<br />
(fig. 4C, 0) with a well-developed anterior intercondylar<br />
groove (fig. 4C, 0, SO), and posteriorly a proportionally<br />
small lateral condyle (fig. 4C, 0). The femora of Dysaloto-<br />
saum (Janensch 1955, pl. 14, figs. 1, 2) are very similar. The<br />
femora of Camptosauna have a much more anteroposteriorly<br />
expanded lesser trochanter and a more distally placed fourth<br />
trochanter. Distally the femora of Othnieh, Hypsilophodon,<br />
Parksosauru~ (Parks 1926) and Thescelosautu~ (Gilmore 1915)<br />
lack an anterior intercondylar groove.<br />
The slender tibia of CM 1949 is longer than the femur<br />
(fig. 4D, E) as in all other hypsilophodontids. The form of<br />
the tibia (fig. 4E-I, 5B, N) of Dlyosaurus is almost identical<br />
to that of YPM 1876, Dysa~otojaum, Othnielia, and Hypsilopho-<br />
don. In Camptosaurus and Tbescelosaurus the tibia is much<br />
FIGURE ~ .-D~~oJ~u~uJ aIta~, referred specimens, femora and tibiae. A-C.-Rich<br />
femur, CM 1949, in lateral view, X0.2. E.-right tibia, fibula, CM 1949,<br />
lateral view, X0.2. F-1.-Left tibia, CM 21786, X0.25 in F, medial view;<br />
G, proximal end; H, anterior view of distal end; I, disral end. J-0.-<br />
Right femur, CM 21786, X0.25; J, proximal end in lateral view; L, distal<br />
end in posterior view; M, distal end in anterior view; N, distal end<br />
in medial view; 0, distal end. A, astragulus; c, cnemial crest; d, deep<br />
depression for insertion of M, caudi-femoralis longus; F, fibula; g, anterior<br />
intcrcondylar groove; gt, greater trochanter; i, inner malleolus; ic,<br />
inner condyle; o, outer malleolus; oc, outer condyle; 4t, fourth trochanter.<br />
Scale lines represent 10 cm.<br />
stockier and shorter than the femur. The fibula of CM 1949<br />
is incomplete (fig. 4E), and it is of normal hypsilophodontid<br />
form. The fibulae of CM 21786 are represented by crushed<br />
ends that are not well preserved.<br />
Only three metatarsals (fig. 5A) and some phalanges are<br />
represented in AMNH 834, but the pes of CM 21786 (fig.<br />
5~3) is the most complete pes of dlyosaurus discovered to<br />
date. CM 21786 possesses two incomplete right distal tarsals<br />
(fused 2-3, 4), the preserved parts of which are of the standard<br />
hypsilophodontid type (Galton 1974, figs. 57F, G). Although<br />
the shafts of the metatarsals are rather crushed, all<br />
the articular surfaces are well preserved (fig. 5H-J). The general<br />
form of the pes is shown (fig. 5C, D), and it is obviously<br />
slender. In Hypsillophodon (Galton 1974, fig. 58), Parksosaurus<br />
(Parks 1926, figs. 15, 16), and Othnielia (Galton and<br />
Jensen 1973, fig. 6D) the first metatarsal is relatively large.<br />
In Dlyosaum the pes of YPM 1884, AMNH 834, and CM<br />
21786 (fig. 5C) all have associated phalanges, but there is no<br />
trace of a good-sized metatarsal I or of any phalanges referable<br />
to this digit. However, in the case of CM 21786,<br />
metatarsal I is probably represented by a dimunitive element<br />
(fig. SC, D, K-M). This element has a convex proximal arricular<br />
surface, so it is not a phalanx; and it shows a well-defined<br />
distal articular surface with two separate condyles (fig.<br />
5M). It cannot be a fifth metatarsal because where known, as<br />
in Hypsillophodon (Galton 1974, fig. 58B) and in Othnielia<br />
(Galton and Jensen 1973, fig. 6A), it is a slender, tapering<br />
rod with a rounded distal end without condyles. This small<br />
element of CM 21786 (fig. 5C, D, K-M) is very similar in<br />
form and size to an element preserved with the pes of Dysalotosaurus<br />
Uanensch 1955, fig. 40) and identified as metatarsal<br />
I. The pes of Camptosaurus and Tbescelosaurus (Gilmore 1915)<br />
are much shorter and stockier than are those referred to<br />
D ryosau rus.<br />
DISCUSSION<br />
On the basis of the comparisons made above, it is appar-<br />
en t that the postcranial anatomy of Dtyosaurus altus (Marsh)<br />
is most similar to that of Dysalotosaurus lettow-vorbecki Pom-<br />
peckj, 1920, from the Upper Jurassic of Tanzania. As noted<br />
earlier (Galton 1973), a comparison of the skull of CM 3392<br />
from the Morrison Formation of Utah with the holotype of<br />
Dryosaurus altus confirms the provisional identification by<br />
Gilmore (1925). However, the skull of CM 3392 does not<br />
have a supraorbital bar as described by Gilmore (1925, fig.<br />
3). Instead, the supraorbital tapers gently to a point lateral<br />
to the postorbital with no suture between these bones. Apart<br />
from the longer supraorbital, the skull of CM 3392 (Galton<br />
1977) is almost identical to that of Dysalotosaurus Uanensch<br />
1955, fig. 1). In all other genera of hypsilophodontids no<br />
two skulls are alike.<br />
In addition to general hypsilophodontid characters, Dryo-<br />
saurus and Dysalotosaurus show the same combination of post-<br />
cranial features. The humeri (fig. 2C-H) are very similar with<br />
a low delto-pectoral crest (also shown by Othn~elia) and a<br />
uniquely flat lateral condyle, but in Dryosaurus the scapula is<br />
longer than the humerus whereas in Dysalotosaurus these<br />
bones are subequal in length. The ilia are very similar; the<br />
ilium of AMNH 834 is almost identical to that of Dysaloto-<br />
saurus as figured by Janensch (1955). In particular both show<br />
a very low main body to the ilium, an obliquely truncated<br />
posterior end, and a broad brevis shelf (fig. 3A-C). In the is-<br />
chia (fig. 3F) the obturator process is proximal in position<br />
(also shown in Othnielia, Parksosaurus), and the distal halves<br />
are bar-shaped and curved in lateral view. In the hind limb
A C B D<br />
FIGURE 5.-Dvosaurus altus, referred specimens, pes. A, metatarsals 2-4,<br />
AMNH 834, dorsal view, X0.3. B, left tibia, AMNH 834, X0.3; C-M,<br />
left pes of CM 21786, X0.2; C, dorsal; D, ventral views; E-G, medial<br />
view of digits: E, 2; F, 3; G, 4; H-J, distal view of metatarsals: H, 2;<br />
I, 3; J, 4; K-M, metatarsal 1 in K, dorsal; L, proximal; M, distal<br />
views; N, proximal end of left tibia, CM 1949, X0.15; 0, distal end of<br />
right femur, CM, 1949, X0.15. 1-4, digits 1 to 4. Scale lines represent 5<br />
cm except K-M where 1 cm.<br />
the femora of Dtyosaums (figs. 4A-D, J-0, 50; Galton 1975,<br />
fig. 2G-L) and Dysalotosaums are nearly identical and possess<br />
the following combination of characters: lesser trochanter is<br />
rodlike and separated from the greater trochancer by a deep<br />
cleft, the deep depression level with [he fourth trochanter is<br />
set well anteriorly on the shaft, and the distal end is square<br />
with a well-developed anterior intercondylar groove. In the<br />
pes metatarsal I is rudimentary (figs. 5C, K) and is represenr-<br />
ed by a small nubbin of bone in both genera.<br />
Dtyosaums altus and Dysalotosaurus lettmu-vorbecki are very<br />
similar and, as discussed elsewhere (Galton 1977, in press),<br />
these species are congeneric and are referred to che -genus<br />
Dtyosaums Marsh 1894 as Dryosaurus altus (Marsh 1878) and<br />
HYPSILOPHODONTID DRYOSAURUS ALTUS 15<br />
Dtyosaurus lettow-vorbecki (Pompeckj 1920). The occurrence of<br />
Dtyosaums in the Upper Jurassic of North America and East<br />
Africa provides good evidence of the presence of a land route<br />
between Laurasia and Gondwanaland in the early Upper Ju-<br />
rassic (Galton 1977, in press).<br />
REFERENCES CITED<br />
Galton, P. M., 1969, The pelvic musculature of the dinosaur Hypsilopbodo<br />
(Reptilia: Omithischia): Postilla, no. 181, 64 p.<br />
, 1973, Redescription of the skull and mandible of Park~o~aurus from<br />
the Late Cretaceous with comments on the family Hypsilophodontidae<br />
(Omithischia): Life Sci. Contr., Royal Ont. Mus., no. 89, 21 p.<br />
-, 1974, The ornithischian dinosaur Hypsilophodo from the Wealden of<br />
the Isle of Wight: Bull. Brit. Mus. (Nat. Hist.) Geol., v. 25, p. 1-152.<br />
-, 1975, English hypsilophodontid dinosaurs (Reptilia: Omithischia):<br />
Palaeontology, v. 18, no. 4, p. 741-52.<br />
, 1977a, The Upper Jurassic ornithopod dinosaur Dryoraurus-widence<br />
for a Laurasia-Gondwanaland connection: Jour. Paleont., v. 51 (2) . . 111,<br />
p. 11-12.<br />
, 1977b, The omithopod dinosaur Dlyoraurus and a Laurasia-Gondwanaland<br />
connection in the Upper Jurassic: Nature, v. 268, p. 230-32.<br />
__, in press, Upper Jurassic ornithopod dinosaur Dryoraurus and a Lauraia-Gondwanaland<br />
connection: Milwaukee Public Mus. Spec. Pap.<br />
Biol. Geol.<br />
Galton, P. M. and Jensen, J. A., 1973, Skeleton of a hypsilophodontid dinosaur<br />
Nanosaufirr (?) re% from the Upper Jurassic of Utah: <strong>Brigham</strong><br />
<strong>Young</strong> Univ. Geol. St., v. 20, no. 4, p. 137-57.<br />
Gilmore, C. W., 1909, Osteology of the Jurassic reptile Camptosaurus with a<br />
revision of the species of the genus, and description of rwo new specimens:<br />
Proc. U.S. Nat. Mus., v. 36, p. 197-333.<br />
-, 1912, The mounted skeletons of Camptosaurus in the United States<br />
National Museum: Proc. U.S. Nat. Mus., v. 41, p. 687-96.<br />
-, 1915, Osteology of Thescelosaurus, an omithopdous dinosaur from<br />
the Lance Formation of Wyoming: Proc. U.S. Nat. Mus., v. 49, p.<br />
591- 616.<br />
, 1925, Osteology of ornithopodous dinosaurs from the Dinosaur National<br />
Monument, Utah: Mem. Carnegie Mus., v. 10, no. 4, p. 385-<br />
409.<br />
Janensch, W., 1955, Der Omithopode Dysa~oto~aurus der Tendagum-schichten:<br />
Palaeontographica Suppl., v. 7(3), p. 105-76.<br />
Marsh, 0. C. 1877, Notice of new dinosaurian reptiles from thc Jurassic Formation:<br />
Amer. Jour. Sci. (3) v. 14, p. 514-16.<br />
, 1878, Principal characters of American Jurassic dinosaurs: Amer.<br />
Jour. Sci. (3) v. 16, p. 411-16.<br />
, 1894, The rypical Ornithopoda of the American Jurassic: Amer.<br />
Jour. Sci. (3) v. 48, p. 85-90.<br />
, 1896, The dinosaurs of North America: 16th Ann. Rpt. U.S. Geol.<br />
Surv., 1894-95, pt. I, p. 133-244, pls. 2-85.<br />
Parks, W. A,, 1926, Thescelosaunrs warren;, a new species of omithopodous<br />
dinosaur from the Edmonton Formation of Alberta: Univ. Toronto<br />
Geol. Ser., no. 21, 42 p.<br />
Pompeckj, J. F., 1920, Das angebliche Vorkommen und Wandern des Parietal<br />
foramens bei dinosauriern: Sber. Ges. Naturf Freunde Berlin, v.<br />
1920. p. 109-29.<br />
Thulbom, R. A., 1972, The postcranial skeleton of the Triassic ornithischian<br />
dinosaur Fabrosaurus austra/ir: Palaeontology, v. 15, no. 1, p. 29-60.<br />
White, T. E., 1964, The dinosaur quarry: Intermountain Assoc. of Petrol.<br />
Geol. 13th Ann. Fld. Conf., v. 1964, p. 22-28.
Paleoenvironmen ts of the Moenave Forma tion,<br />
St. George, Utah*<br />
Assman.-Geometry of sandstone bodies, sedimentary structures, and paleo-<br />
current trends obtained from channel pods and numerous ribbon sandstone<br />
lenses in the Moenave Formation in St. George, Utah, were studied to deter-<br />
mine the Moenave environment of deposition.<br />
A north-south trending toadcut leading to St. George Municipal Airport<br />
exposes two major channels filled with homogeneous very fine sandstone and<br />
siltstone which fine upward. The south channel consists of four major undu-<br />
lations, each of which appears to represent a different segment of a single<br />
sinuous channel. Sixty-five oriented hand samples taken from all the channel<br />
undulations reveal environmentally diagnostic sedimentary structures (flaser<br />
and wavy bedding) and bimodal paleocurrent trends. The hand samples, cut<br />
in three dimensions, indicated strong primary north and northeast current<br />
trends, but also revealed weak secondary trends to the west and southwest.<br />
Anticipated characteristics of subaerial fluvial processes in these channels were<br />
lacking.<br />
East of the airport location 2 km, the vertical sequence is composed of<br />
bundles of sandstone and siltstone ribbonlike lenses whose average width-to-<br />
depth ratios exceed 40:l. Sixty paleocutrent measurements taken in this toad-<br />
cut show north-south bimodal current trends with central tendencies of 1.0<br />
calculated frorn vector analysis of the current measurements. Three hundred<br />
additional current measurements taken in the erosional cliffs north of the<br />
city of St. George, indicate bimodal trends toward the northeast and south-<br />
west. Only ichnofaunal fossil rypes resembling Skolithos, Arenicolifes, and Dip-<br />
locraterian were found in the sandstone lenses of the erosional cliffs and east-<br />
an roadcut.<br />
Bimodality of paleocuttent trends in the Moenave sediments is inter-<br />
preted to be related to depositional processes in a tidal flat system. The large<br />
channel undulations and surrounding deposits ate interpreted to have formed<br />
in the subaqueous subtidal zone. Paleocurrent results frorn the erosional cliffs<br />
help define a north-south trend of the paleoshoreline, and ribbon sandstone<br />
bodies at the eastern toadcut locations suggest deposition in the sandy inter-<br />
tidal zone. Regional paleocuttent trends indicate that the Moenave tidal flat<br />
extended from Ivins, Utah, to Zion Canyon, Utah, and may have occupied a<br />
peripheral position on a large delta forming on the eastern margin of a shal-<br />
low sea which existed in the present site of southeast Nevada.<br />
INTRODUCTION<br />
The Upper (?) Triassic Moenave Formation of northern<br />
Arizona and southwestern and south central Utah forms the<br />
basal section of the familiar reddish-brown Vermillion Cliffs<br />
which tend in a sinuous pattern from the Moenave type sec-<br />
tion near Moenave, Arizona, westward to the Beaver Dam<br />
Mountains, Nevada, and northward to Cedar City, Utah. Ex-<br />
cellent exposures of two unusuallv well-meserved channel de-<br />
posits within the Moenave Formation are revealed in a road-<br />
cut on the highway leading to the municipal airport in the<br />
city of St. George, Utah. The two northeast trending chan-<br />
nels are cut obliquely by the roadcut so that five large chan-<br />
nel undulations are exposed. The first channel consists of a<br />
single, large concave upward undulation and is found at the<br />
north end of the roadcut. The second channel is located 40<br />
m south of the first, and consists of four major undulations,<br />
each of which appears to represent a different segment of a<br />
single channel meander. Overall length of the two channels<br />
in this roadcut is 195 m.<br />
A second roadcut, located at the intersection of Middle-<br />
ton Black Ridge and Interstate 15, exposes a vertical se-<br />
quence of bundles of ribbonlike or lenticular sandstone and<br />
JOHN DANIEL DAVIS<br />
Guf Energy and Mjnerals, Carper, Wyoming 82601<br />
siltstone bodies. Seen in vertical section, this exposure cuts<br />
diagonally across the long axis of the lenses. The rocks of<br />
these cliffs consist of thick lenses of sandstone and siltstone,<br />
and massive, tabular layers of mudstone.<br />
Sediments exposed in the two roadcuts and the cliffs<br />
north of St. George Boulevard are part of the slope-forming<br />
Dinosaur Canyon Member of the Upper (?) Triassic Moenave<br />
Formation. This member consists of siltscone, silty mudstone,<br />
and very fine sandstone, with minor amounts of in-<br />
traformational mud-pebble conglomerate. Sandstone and silt-<br />
stone lithologies of the study area are confined to the thick<br />
channel undulations or to thin ribbonlike lenses within the<br />
Dinosaur Canyon Member of the Moenave Formation. In-<br />
traformational conglomerates are found sandwiched between<br />
lenses of sandstone.<br />
Sedimentary structures commonly found in the sediments<br />
of the study area are flaser and wavy bedding, planar and<br />
trough cross-bedding, current ripple marks, burrows, feeding<br />
trails, and mud cracks. Bimodal current directions and overall<br />
slight upward fining also characterize the Moenave sediments.<br />
Massive layers of mudstone enclose the channel undulations<br />
and ribbon sandstone lenses and have very few sedimentary<br />
structures, but are mildly bioturbated. Moenave sediments in<br />
the St. George study area are but little deformed except for<br />
slight regional tilting to the north, and are accessible by sev-<br />
eral major roads: Interstate 15, Utah Highway 18, U.S. High-<br />
way 91, and residential streets within the city of St. George,<br />
Utah.<br />
The main objective of this research is to determine the<br />
paleodepositional environment which was responsible for the<br />
. .<br />
stratigraphic and sedimentary characteristics of these rocks as<br />
seen in vertical sequences of selected outcrops. This objective<br />
was accomplished by analyzing the geometry, internal struc-<br />
tures, current flow measurements, and depositional fabric of<br />
the sediments in the roadcuts and cliffs of the study area and<br />
synthesizing this information into a reconstruction of a pa-<br />
leodepositional model.<br />
Previous Work<br />
Regional stratigraphic studies of the Chinle, Moenave,<br />
Wingate, Kayenta, and Navajo formations began in the early<br />
1900s, and their classification and subdivision have been re-<br />
vised several times (Harshbarger, Repenning, and Irwin<br />
1957). The first attempt to discriminate the Moenave Forma-<br />
tion was made by L. F. Ward (1901) in his studies of the<br />
basal unit of the "orange red sandstone" of the "Painted<br />
Desert beds." Ward's use of the term Painted Desert bed sub-<br />
sequently led to considerable confusion owing to the wide-<br />
spread occurrence of painted deserts in the Chinle Formation.<br />
What is now referred to as the Chinle Formation constituted<br />
Ward's "Le Roux beds." Ward's "Painted Desert beds" rep-<br />
'A thcsir pracnrcd ro rhc Lkprrmmr of Gcolom. Br!gham <strong>Young</strong> Univcrsio. xn plrrrrl fulfillmcnr of rhc rcquircmmrs for rhc degm Mvrcr of Sricnce, Deccmbcr 1976: W. Kmnerh Hamblin, th& chair-<br />
man
18 J. D. DAVIS<br />
resent the Glen Canyon Group and include the D~nosaur<br />
Canyon siltstone member (Ward" '"range red sandstone"),<br />
the alty factes of the Kayenta Formation (Ward's "var~egated<br />
sandstones," the well-known 'Tainted Cliffs"), and the Nav-<br />
ajo Sandstone (Ward's "brown and white sandstone")<br />
In 1917, Gregory descrtbed Ward's "Panted Desert beds"<br />
as "undifferentiated La Plata and McElmo" of the Moenkopi<br />
Plateau He also correlated Ward's "brown and whtte sand-<br />
stone" with the Navajo Sandstone to the north Gregory and<br />
W~lliams (1947), and Gregory (1948, 1950a, b) made a de-<br />
ta~led study of the geology and geography of southwestern<br />
Utah which tncluded the Moenave strata In his 1950 pub-<br />
lication Gregory revlsed the preexisting Mesozoic stratigra-<br />
phic correlattons of the region and named and defined the<br />
springdale Member as on< of the four subdivisions of the<br />
Chinle Formation.<br />
Colbert and Mook (1951) named and defined the Dino-<br />
saur Canyon Sandstone after Dinosaur Canyon, 16 km east of<br />
Cameron, Coconino County, Arizona. Harshbarger, Repenn-<br />
ing, and Irwin (1957) redefined the stratigraphic relationships<br />
of the Chinle, Moenave, Wingate, Kayenta, and Navajo for-<br />
mations and proposed that they be placed in the Glen Can-<br />
yon Group. Wilson (1959) madr a regional stratigraphic<br />
study of the Moenave and Kayenta formations of north-<br />
western Arizona and southwestern Utah. He mapped the<br />
boundary relationships of these two formations and suggested<br />
that fluvial and eolian environments, respecttvely, were re-<br />
sponsible for the deposition of them. He also mapped, de-<br />
fined, and named a third member of the Moenave Formation,<br />
called the Whttmorc Point Member. Day (1367) mapped the<br />
Moenave Formation in the western portion of Zion Canyon<br />
and Washington areas and also proposed that fluvial process-<br />
es were responsible for deposition of Moenave sediments in<br />
his study area. These earlier papers provide adequate litholog-<br />
ic descriptions and set a regional framework for the present<br />
study.<br />
Location<br />
The principle study area IS confined to selected outcrops<br />
to the west, north, and northeast of St. George, Utah (fig.<br />
1). The westernmost outcrop studied is located at the base of<br />
the access road leading to the St. George Municipal Airport<br />
where it intersects Utah Highway 18. This outcrop wtll be<br />
referred to as the "airport roadcut" in this study. The northern<br />
outcrops are the' east-west trending natural slopes and<br />
cliffs whtch lie north of the city and parallel the length of<br />
St George Boulevard The northeast outcrop is the Interstate<br />
15 roadcut wh~ch passes through the north-south trending<br />
lava-capped Middleton Black R~dge Th~s outcrop will be referred<br />
to as the "Interstate 15 roadcut" In this study Paleocurrent<br />
measurements were collected at selected locations<br />
near the Leeds offramp along Interstate 15, above the Visitors'<br />
Center in Zion Canyon, in Kanab Canyon along<br />
U.S.Highway 89, and north of the community of Ivins,<br />
Utah.<br />
The principle study area is located in sections 24 and 25<br />
of T. 42 S, R. 16 W, and sections 19, 20 and 21, of T. 42 S,<br />
R. 15 W.<br />
Mcthids of Study<br />
This study cirncentrated on the character of the channel<br />
depos~ts near the alrport and the lentrcular sandstone bodies<br />
in the Interstate 15 roadcut In~tial field work commenced<br />
with construction of a deta~led photomosa~c cross section of<br />
each roadcut. This task was accomplished by photographing<br />
in sequence small segments of roadcut, each segment measur-<br />
ing 4 m in width. A 4-m stadia rod was especially helpful for<br />
thickness measurements of inaccessible beds in both roadcuts.<br />
Each bed was then plotted on the cross section so that<br />
geometry and bedding relationships between each lithic layer<br />
could be determined.<br />
Hand samples were collected at the airport roadcut in<br />
vertical sections at every change in lithology and at horizon-<br />
tal intervals of approximately 15 m. Sampling and study of<br />
the outcrop face at precarious and inaccessible heights of this<br />
roadcut were accomplished by the use of a utility telephone<br />
truck quipped with a hydraulic extensional arm and per-<br />
sonnel bucket. Hand samples were also collected in some of<br />
the large sandstone lenses in the Interstate 15 roadcut. Prop-<br />
er orientation control of the samples was maintained by<br />
marking a reference azimuth on the samples in situ. All col-<br />
lected samples were sawed in the laboratory into approx-<br />
imately rectangular shapes (about 9 cm on a side) so that in-<br />
ternal structures and current directional properties could be<br />
analyzed in a true three-dimensional perspective.<br />
A few thin sections of channel sandstones/siltstones and<br />
mudstones were made so that lithology, sorting, micro-<br />
structures, and fabric relationships could be studied. Some<br />
samples were etched for model composition of alkali feldspar<br />
and X-rayed for identification of the presence of iron miner-<br />
als.<br />
A total of 300 measurements of current directions was<br />
made at various locations within the St. George study area<br />
and plotted on low-altirude, oblique aerial photographs in or-<br />
der to provide control of the locaticms of current flow mea-<br />
surements. An additional 165 paleocurrent measurements<br />
were collected at Ivins, Leeds, Zion Canyon, and Kanab,<br />
Utah, to provide a regional concept flow direction at the<br />
time of deposition of the Dinosaur Canyon Member of the<br />
Moenave Formation in the St. George, Utah, study area.<br />
The author wishes to extend sincere gratitude to Dr. W.<br />
K. Hamblin, Dr. J. Keith Rigby, and Dr. Morris Petersen of<br />
Flcuxe 1.- Index mdp<br />
STUDY AREA
the Department of <strong>Geology</strong> for their advice and assistance in<br />
field research, illustration techniques, and writing of the<br />
thesis. Financial assistance was provided through the Jake L.<br />
Berge Exploration Grant. Rudger MacArthur of the city of<br />
St. George, Utah, provided a utility telephone truck for sam-<br />
pling roadcuts at inaccessible positions. Appreciation is also<br />
extended to all the graduate students in the <strong>Geology</strong> Depart-<br />
ment who freely gave their advice, counsel, and consolation.<br />
GEOLOGIC SETI'ING<br />
Regional paleotectonic history of the southwestern<br />
United States during Triassic and Jurassic time has been sum-<br />
marized by McKee et al. (1959). During Early Triassic time<br />
the Colorado Plateau area of the Four Corners region and<br />
southern Utah was relatively quiescent tectonically, and the<br />
highlands of western Colorado were eroded to low or moder-<br />
ate relief. Regularity of bedding, fineness of grain sizes, and<br />
related features suggest tectonic stability.<br />
In contrast to the Early Triassic period, the Late Triassic<br />
was tectonically unstable because of uplift of the Colorado<br />
Plateau in the east and subduction along the North Ameri-<br />
can plate margin to the west (Burchfiel and Davis 1975).<br />
Wide dispersal of conglomerate beds and lenses in the west-<br />
ern Colorado Plateau attest to the irregularities of sedimenta-<br />
tional processes resulting from episodic orogenic pulsations.<br />
Uplift in the Colorado Plateau, however, was probably more<br />
influential upon the sedimentary systems involved in the dep-<br />
osition of the Moenave Formation than were the orogenic in-<br />
fluences to the west in west central Nevada. Grain-size distri-<br />
bution (size increase toward the east) and increases in<br />
mud/clay content in the sediments westward to the St.<br />
George area from the Colorado Plateau suggest an eastern<br />
provenance (Harshbarger et al. 1957).<br />
As subduction processes evolved and persisted at the<br />
western plate margin in western Nevada, miogeosynclinal se-<br />
quences were being deposited in southeastern Nevada and<br />
southwestern Utah (McKee et al. 1959). Fluvial processes in<br />
the Four Corners region contemporaneously carried sediments<br />
Novaio Sandstone<br />
Kayento Formalion<br />
Spr4ngdolc Member<br />
D,nosaur Canyon Member<br />
PALEOENVIRONMENTS OF THE MOENAVE FORMATION 19<br />
from the uplifted Colorado Plateau to the southwestern Utah<br />
area during Moenave time. Wide flood plains, with well-de-<br />
veloped meandering channel systems and isolated lacustrine<br />
environments, evolved during this period (Harshbarger et al.<br />
1957; Wilson 1959).<br />
The overall depositional system of the Moenave Forma-<br />
tion in western Utah appears to be fluvial-deltaic (Wilson<br />
1959) as inferred from interpretation of the overall upward<br />
coarsening of its members: Dinosaur Canyon Member-very<br />
fine sandstone, siltstone, and mudstone; Whitmore Point<br />
Member-siltstone, mudstone; and Springdale Sandstone<br />
Member-fine to medium sandstone. The Dinosaur Canyon<br />
Member of the study area is not typically fluvial as it lacks<br />
the characteristic point bar sequences of upward fining sedi-<br />
ments in sandstone lenses. The Moenave sediments of the<br />
study area may represent a marginal tidal flat within the<br />
larger deltaic system which bordered the shallow marine shelf<br />
environment southwest and west of the study area in south-<br />
eastern Nevada.<br />
GENERAL SEDIMENTARY FEATURES<br />
Stratigraphically, the Moenave Formation is included in<br />
the Glen Canyon Group and lies above the uppermost mem-<br />
ber of the Chinle Formation (Petrified Forest Member) and<br />
below the Kayenta Formation, with minor unconformities at<br />
both upper and lower contacts. In some locations the Moen-<br />
ave/Kayenta contact is gradational. The intertonguing facies<br />
relationships of the Springdale Sandstone with the Whitmore<br />
Point and Dinosaur Canyon members are complex but are<br />
not included as part of the objective of this research. Overall<br />
geometry of the Moenave Formation on a regional scale is<br />
somewhat wedge shaped, thickening toward the west and<br />
northwest from the Four Corners region. Thicknesses vary<br />
from 103 m in the type locality to 165 m at Cedar City,<br />
Utah. Locally, the geometry of the Moenave sediments is pod<br />
and lenticular shaped. Grain size of the Moenave sediments<br />
generally decreases from the Four Corners area toward the St.<br />
George and Cedar City areas.<br />
INDEX TO STRATIGRAPHY<br />
Iv~nr St George Zion Cola,-ado City Konob<br />
I I<br />
FIGURE 2.-Moenave Formation stratigraphy from lvins to Kanab, Utah.
20 J. D. DAVIS<br />
FIGURR 3.-North channd in airport roadcut. Stadia rod is 4 m.<br />
.-. ,. , ', -- ,.<br />
FIGURE 4.-South channel in airport roadcut, located 40 m south of the north channel.<br />
Very F~ns Sondr~one<br />
n Siltstone<br />
RGURE<br />
>.-Schematic drawing of tabular appearance of massive mudstone layers which enclose the channel deposits. Letters A, 8, and C are in sequence from<br />
south to north.
Three members comprise the Moenave Formation: (1) a<br />
basal slope-forming Dinosaur Canyon Member, consisting of<br />
dull reddish brown siltstone and silty mudstone, which varies<br />
in thickness from 60 m at the type-locality to 135 m at Ce-<br />
dar City; (2) a middle slope-forming Whitmore Point Mem-<br />
ber found between Pipe Springs National Monument, Ari-<br />
zona, and the Silver Reef mining district, Washington, Utah,<br />
consisting of greyish colored siltstone and mudstone; and (3)<br />
the uppermost light brown prominent cliff-forming unit, the<br />
Springdale Sandstone, consisting of fine- to medium-size<br />
sandstone conspicuously cross stratified by medium-to-large-<br />
scale planar and [rough type cross-bedding. Roadcuts of the<br />
study area and the natural cliffs north of St. George Boule-<br />
vard are part of the Dinosaur Canyon Member. Comparative<br />
profiles oi stratigraphic sequences of the Moenave ~oimation<br />
and units above and below it, from Ivins to Kanab, Utah,<br />
appear in figure 2.<br />
Geometry<br />
Sandbodies of the Moenave Formation in the study area<br />
have three different shapes: (1) thick, pod-shaped channel de-<br />
posits composed of siltstone and very fine sandstone found in<br />
the airport roadcut; (2) thin, lenticular ribbon bodies com-<br />
posed of siltstone and very fine sandstone located in the In-<br />
terstate 15 roadcut; and (3) massive tabular layers of mud-<br />
stone which surround the channel pods and ribbonlike lenses<br />
and are found at both roadcuts.<br />
The north-south trending airport roadcut exposes two<br />
major channels (figs. 3 and 4). Approximately one-half of the<br />
northern channel (fig. 3) has been eroded; the remaining<br />
half is 45 m wide and 5 m deep. Its upper boundary is flat<br />
and horizontal whereas the lower surface is concave uoward.<br />
PALEOENVIRONMENTS OF THE MOENAVE FORMATION 21<br />
pebbles, gravel, shells, plant debris, etc.-accumulates as chan-<br />
nel lag. The remainder of the overlying sediments of a fluvial<br />
channel fill may be composed of graded sandy material. It is<br />
not uncommon to find channels completely filled with mud-<br />
dy and/or silty sediments, as in gullies and channels in tidal<br />
flat environments.<br />
Sediments which fill the Moenave channels at the airport<br />
roadcut are fairly homogeneous siltstone and very fine sand-<br />
stone. It is particularly significant that no coarse debris, rock<br />
particles, or graded bedding are present. Homogeneity of the<br />
sediments in these channels may indicate that they were de-<br />
posited in submerged channels produced by submarine cur-<br />
rents rather than by subaerial fluvial processes.<br />
Channel- Filling Mecbanirms<br />
Channels may be filled in three ways as suggested by<br />
McKee (1957):<br />
1. By horizontal layers (fig. 6a). Channels filled by this<br />
method are not submerged, and the water level re-<br />
mains within the channel. This method of channel fill<br />
may represent rapid deposition because of rapid in-<br />
crease of sediment load or decrease in stream velocity.<br />
Sediment sizes are somewhat coarse.<br />
2. By layers conforming approximately to the channel<br />
shape with upward concavity (fig. 6b). Channels filled<br />
in this manner are usually submerged, and, in cross<br />
section, the channel fill may show uniform thickness<br />
of layers, or layers may thin laterally toward the sides.<br />
3. By asymmetrical filling with steeply inclined layers<br />
(fig. 6c). Asymmetrical channel fills are produced by<br />
diagonally passing currents as in submerged intertidal<br />
zones where flow of tidal water is controlled more by<br />
The width-to-depth ratio is 9:l. Contacts of the channel<br />
boundaries with the enclosing mudstone deposits are sharp<br />
and well defined (fig. 5).<br />
The southern channel, located 40 m south of the north<br />
channel (figs. 4 and 5), consists of four major undulations,<br />
each of which appears to represent a different segment of a<br />
single sinuous channel. Its overall exposed width measures<br />
115 m. The upper surface of this large channel is flat and<br />
horizontal, with lower boundaries of all undulations concave<br />
upward. Width-to-depth ratios of the undulations average<br />
6:l. UDD~~ and lower contacts of all channel undulations<br />
I I<br />
with the surrounding mudstone sediments are sharp and well<br />
defined.<br />
The geometry of the channel pods, expressed as a ratio<br />
of its length-to-width or width-to-depth dimensions, is significant<br />
in that width/depth ratios may be indicators of the nature<br />
of sediment load (Schumm 1968). Width/depth ratios<br />
are used in this study because only a single plane br surface<br />
of the channels is expressed in the roadcuts. Streams carrying<br />
sand by bed-load processes have width/depth ratios which<br />
commonly exceed 40 (Schumm 1968), whereas in dominantly<br />
suspended load streams, w/d ratios are less than 10 (Pettijohn<br />
et al. 1973).<br />
W/d ratios in the Moenave channel deposits in the airport<br />
roadcut average 6:l and may suggest that the sediments<br />
which filled the channels were carried by suspension.<br />
Channels are produced either by streams in a partially<br />
subaerial position or by submerged or submarine currents<br />
(McKee 1957). Decreases in velocity result in proportionate<br />
rates of deposition and eventual complete infilling of the<br />
channel. Sediments of the channel fill are commonly different<br />
from sediments which may surround the channel deposits. In FIGURE 6.-Bedding plane lndinarions In<br />
general, at the base of fluvial channels, coarse sediment-mud<br />
filling processes.<br />
channels indicate types of channel
22 J. D. DAVIS<br />
differences in tidal levels than by surface morphology<br />
or by laterally migrating, meandering streams.<br />
Sediments filling the channels in the airport roadcut are<br />
mostly parallel bedded at the tops of the channels, but be-<br />
come more inclined near the sides of the deepest portions of<br />
the channels (fig. 3). This slight inclination of the bedding<br />
may suggest that the channels were filled by methods 2 or 3.<br />
The vertical sequence in the Interstate 15 roadcut is<br />
made up of bundles of thin ribbonlike lenses composed of<br />
siltstone, very fine sandstone, and mudstone (fig. 7). These<br />
lenses are both asymmetrical and symmetrical and appear in a<br />
vertical cut as ribbons. The asymmetrical ribbon sandstone<br />
lenses have flat tops and concave upward lower surfaces (fig.<br />
8). Symmetrically shaped lenses are biconvex on upper and<br />
lower surfaces. Contacts of all sandstone and siltstone lenses<br />
in this roadcut are sharp and well defined. There are 21 iden-<br />
tifiable sandstone and siltstone lenses in this roadcut whose<br />
widths range from 12 to 80 m, and whose average maximum<br />
depth is 1.2 m. Width-to-depth ratios range from 12:1 to<br />
67:l (fig. 8).<br />
The geometry of the sediments of this roadcut is in-<br />
dicative of rather unstable conditions of sedimentation where<br />
periods of deposition and erosion are relatively short and<br />
somewhat cyclic (Weller 1960). The high w/d ratios may in-<br />
dicate that very fine sand- and silt-size particles were carried<br />
by bed-load mechanisms in shallow water having relatively<br />
stronp; currents (Schumm 1968). Some of the sandstone len-<br />
ses may have b&n small channels or runnels.<br />
Quantitatively, the dominant lithology of the airport<br />
roadcut area consists of massive layers of mudstone deposits<br />
RCURE 7.-Bundles of ribbon sand bodies at Interstate 15 roadcut.<br />
FIGURE 8.-Schematic drawing of ribbon sand bodies. Interstate 15 roadcur.<br />
which surround thick sandstone channel pods (undulations).<br />
Mudstone layers are laterally persistent and fairly horizontal<br />
and appear to be somewhat tabular (fig. 5). Thicknesses of<br />
the individual mudstone layers are reasonably consistent,<br />
ranging from 18 cm to 1.5 m, although their consistency is<br />
periodically interrupted by some minor irregular pinching and<br />
swelling of their upper and lower contacts. Lateral continuity<br />
is also interrupted by deep excavations of the channel undu-<br />
lations (fig. 5). Channel undulations 3 and 5 of figure 5<br />
both cut through the green clay marker bed (the narrow<br />
stippled pattern in fig. 5), but channel undulation 3 scoured<br />
even deeper into the underlying massive very fine sandstone<br />
layer at the base of the outcrop. All contacts of the mud-<br />
stone units with the sandstone and siltstone bodies are sharp<br />
and well defined.<br />
Shapes of mudstone layers found in Interstate 15 roadcut<br />
are not so easily determined because of the complex stratigra-<br />
phic appearance imparted to the vertical cut from the bun-<br />
dles of sandstone and siltstone lenses (fig. 8). Mudstone lay-<br />
ers located in the basal one-third of this roadcut are massive<br />
and average 0.9 to 1.5 m in thickness. Upper surfaces are<br />
fairly flat and horizontal, while lower surfaces are covered by<br />
talus and are not observed. Mudstone layers in the middle<br />
portion of this roadcut are not so thick as those in the basal<br />
section and average 0.5 m in thickness. Upper and lower sur-<br />
faces of the mudstone layers in the middle section are mostly<br />
flat but show moderate pinching and swelling where they are<br />
in contact with the sandstone and siltstone lenses. Layers of<br />
mudstone located in the upper third of this roadcut have flat<br />
and horizontal upper and lower boundaries, but slight pinch-<br />
0 32 64 96 128m
ing and swelling are observed. Average thickness of the len-<br />
ses in the upper section is 40 cm.<br />
The geometry of the vertical sequence of the Moenave<br />
sediments in erosional cliffs north of St. George Boulevard is<br />
composed of thick lenses of sandstone and siltstone and thick<br />
tabular mudstone layers. In some locations, lenses of in-<br />
traformational conglomerate consisting of rounded mud/clay<br />
balls, 1.3 cm to 5.0 cm in diameter, are found sandwiched<br />
between the layers of mudstone and lenses of siltstone or<br />
sandstone (fig. 9). Exact measurements of the thicknesses of<br />
the sandstone lenses and tabular mudstone layers were not<br />
made, but in general, they thicken toward the western ex-<br />
tremity of the cliffs.<br />
FIGURE 9.-Intnformational conglomerate lens<br />
Composition<br />
Moenave channel deposits and lenticular or ribbon sandstone<br />
bodies all consist of rather homogeneous siltstone and<br />
very fine sandstone and show slight upward fining. Grains in<br />
both rock types are well rounded and cemented. They are set<br />
in a matrix of calcite and iron oxide cement. Mineralogically,<br />
95 percent of the grains is quartz, the remaining 5 percent is<br />
alkali feldspar, with minor amounts of biotite, muscovite,<br />
and iron silicate minerals (amphibole). Sorting is poor to<br />
moderate as the mud, silt, and sand fractions are commonly<br />
intermixed to some degree. Bedding planes in the channel<br />
deposits are somewhat parallel at the tops of the channels<br />
but appear to conform to the concave upward shape of the<br />
PALEOENVIRONMENTS OF THE MOENAVE FORMATION 23<br />
L 1<br />
channel bottoms or undulations (fig. 3).<br />
Most Moenave sediments are characteristically a reddish<br />
FIGIJR~ 10.-Flaar bedding. -<br />
--<br />
brown color due to pigmentation by the iron oxide coating<br />
on quartz grains of the siltstone and sandstone.<br />
Mudstone units of the Moenave roadcut study areas are<br />
composed of poorly sorted, subrounded grains of quartz and<br />
minor amounts of alkaline feldspar cemented with calcite and<br />
' - -<br />
iron oxicide. They are highly effervescent In dilute hydrochloric<br />
acid. Coloration of these units varies from light<br />
brown or tan to greyish green. Characteristically, the mudstones<br />
are hlghly mottled with spherical inclusions of clay.<br />
For example, a mudstone unit which appears to have an<br />
overall greenish color can be mottled with brown clasts, or<br />
the unit will have a brownish color and be modified by the<br />
presence of greenish-colored clasts. The light brown coloration<br />
is from pigmentation of iron oxide coatings on the<br />
quartz grains. The greyish green coloration is suggestive of<br />
I<br />
reducing conditions. Burrows and tralls, also suggestive of FIGURE 11 -Wavy bedding.<br />
rich organic domains, were the only forms of bioturbation<br />
preserved and were found in the mudstone layers. Weathered<br />
surfaces of the mudstone are typically bulbous or semi-<br />
spherical owing to the presence of clay in minor quantities<br />
in the mudstone.<br />
Very few sedimentary structures are seen in the mud-<br />
stone bodies other than parallel colorations (alternating<br />
cream color, brown or light green), or traces of microsize fla-<br />
ser beds or wavy laminations.<br />
Sedimentaty Structures<br />
Sedimentary structures found in the channel deposits and<br />
ribbon sandstone bodies are mostly flaser and wavy bedding<br />
and small- to medium-scale planar and trough - type .- cross bedding<br />
(figs. 10-13). Details bf bedding are commonly poorly<br />
expressed and obscured in natural outcrop and the roadcuts<br />
of the study area. Major lithologies, especially in the airport<br />
roadcut, appear to be massive and homogeneous, with only<br />
local faint expressions of small-scale sedimentary structures.<br />
Clean hand samples reveal that most, if not all, of the siltstone<br />
within the channel undulations and ribbon sandstone<br />
bodies contain flaser and wavy bedding, ripple laminations, or<br />
microscale cross stratification ranging from a millimeter to a<br />
centimeter or two in thickness. Flaser and wavy bedding<br />
structures are distributed throughout all portions of the<br />
channels. Small-scale planar cross-beds are found predominantly<br />
at the tops of the channels and nearest the<br />
boundary edges of the channel undulations. Planar and<br />
trough type cross-beds of medium scale are distributed<br />
throughout the central and basal portions of the channels.<br />
Distribution of the various types of sedimentary structures<br />
within the channels may be useful in defining locations<br />
of relative current strengths within each channel. Strongest<br />
currents (thalweg) in the Moenave channels are defined by
24 J. D. DAVIS<br />
the distribution of the small- to medium-scale cross-beds lo-<br />
cated in the central and basal portions of the channels. Gen-<br />
erally, sedimentary structures diminish in size outwardly from<br />
the central portions of the channels, suggesting decreasing<br />
current strength toward the sides of the channels.<br />
Flaser and wavy bedding are the most common sedimen-<br />
tary structures found in all the sediments of the study areas.<br />
They suggest the availability of both sand and mud during<br />
alternating periods of current-flow and slack-water conditions<br />
(Reineck 1973). During periods of current activity, sand is<br />
FIGURE 13.-Small-scale trough type crossbedding.<br />
FIGURE 14.-Paleocurrent trends in channel undulations at the airport roadcut.<br />
transported and deposited as ripples, and mud is held in sus-<br />
pension. As the current ceases, mud and fecal pellets settle<br />
out and accumulate in ripple troughs, or completely cover<br />
the ripple crests (fig. lo). The relative thicknesses of sand or<br />
mud between the successive flaser or mud ribbons indicate<br />
the availability of relative amounts of sand or mud and<br />
which conditions were more conductive to deposition of one<br />
sediment over the other. For example, if more mud was<br />
available than sand, and periods of slack water were longer<br />
than periods of tidal flow, wavy bedding structures would be<br />
more common than flaser bedding.<br />
Sedimentary bedding of this Gpe is common in the tidal-<br />
flat environment. Sand deposition results from bed-load trans-<br />
port, from movements of incoming tidal currents, and from<br />
the back-flow currents of ebb tides. The relative periods of<br />
quiescence between the two currents result in deposition of<br />
mud or fecal matter held in suspension (Reineck 1973).<br />
PALEOCURRENT DATA<br />
The most significant information revealed by the sedi-<br />
mentary structures of the Moenave sediments was the direc-<br />
tions of paleocurrent flow trends derived from the cross-bed-<br />
ding.<br />
Paleocurrent directions in the channel deposits of the air-<br />
port roadcut were determined by measuring micro-cross-la-<br />
minae in 65 hand samples collected at relatively close inter-<br />
vals within the channels. Approximately 15 samples were<br />
collected in each channel undulation. Large oriented speci-<br />
mens were collected and sawed into rectangular blocks in the<br />
laboratory so that true current directions could be measured.<br />
Each sample was sawed into blocks. and horizontal sections<br />
cut through the cuspate cross-laminae revealed the true cur-<br />
rent directions of several sets of strata. The points or narrow<br />
rounded noses of the cusps pointed in the direction of cur-<br />
rent flow, as well as the intersection of two planes of dip-<br />
ping stratification. Ten additional measurements of cross-bed-<br />
ding directions were collected on the outcrop face of the<br />
north channel, designated as channel 5 in figure 14. Channel<br />
undulations in the south channel are indicated by the num-<br />
bers 1-4. Current flow measurements in all locations of the<br />
study area ate represented individually as vectors (fig. 15)<br />
having equal length (8 mm) or magnitude. They were<br />
plotted in vector groups or trains for each location. The<br />
mean current direction of each group of vectors is calculated<br />
by drawing a heavy arrow from the origin of each train of<br />
vectors trending in one direction toward the end vector. Let-<br />
ters A-J of the vector diagrams in figure 15 designate the lo-<br />
cations of each group of measurements and correspond to<br />
the locations indicated by the same letters in figure 18. The
north and south channels of the airport roadcut are desig-<br />
nated I and J, respectively. A measure of central tendency, or<br />
consistency ratio, in each direction was calculated by com-<br />
paring the ratio of the total length of the vector mean with<br />
the cumulative magnitude of the individual vectors.<br />
The general trend of the channels is northeast and is<br />
"<br />
summarized in table 1. However, second order trends in<br />
channel undulations numbered 1, 3, and 4 indicate current<br />
flow in the opposite direction of the vectoral sum. Using the<br />
data from table 1 and figure 14, which show the location of<br />
current measurements and current directions of each channel.<br />
it appears that the four interconnected channel undulations<br />
are parts of the same channel meander and may have inter-<br />
sected the large, single channel immediately to the north in<br />
this roadcut. The overall large size, depth, and paleocurrent<br />
direction of the largest channel suggest that it was not part<br />
of the same channel meanders as the other four connected<br />
channel undulations (fig. 14).<br />
Interstate 15 cuts through the Middleton Black Ridge<br />
roadcut study area approximately normal to the regional<br />
north-south trend of the lenticular sandstone and siltstone<br />
bodies. Paleocurrent flow directions of these lenses were de-<br />
termined from 60 in situ measurements of micro-cross-la-<br />
minae found within various sandstone and siltstone lenses lo-<br />
cated near positions 1 and 2 of figure 8 and from hand<br />
samples collected from some of the sandstone and siltstone<br />
lenses. The uppermost portions of the roadcut were in-<br />
accessible for current measurements. At location 1, current<br />
flow data from 30 measurements indicated bidirectional<br />
trends of equal significance having vectoral sums of 001' and<br />
189' (fg. 15A). Central tendencies in each direction were<br />
1.00. Vector mean directions and central tendencies were cal-<br />
culated in the same manner as the paleocurrent data calcu-<br />
lated for the sediments of the airport- roadcut. Measurements<br />
at location 2 are similar to those at location 1, i.e., 000" and<br />
192' (fig. 15A), with central tendencies of 1.00 in each direc-<br />
tion.<br />
An additional 300 measurements of cross-bedding struc-<br />
tures were taken in sandstone and siltstone lenses exposed<br />
along the basal and middle sections of the cliffs north of St.<br />
George Boulevard. An aerial photograph (fig. 16) indicates<br />
the locations where measurements were made. Each general<br />
location of measurements is designated on the aerial photo-<br />
graphs by a large white letter b-f, and the exact position of<br />
each group of measurements is indicated by a small white<br />
numbers. Positions G and H shown in the summary vector<br />
diagram (fig. 15, G and H) are located in figure 17. Current<br />
flow data at each location is shown by vector diagrams figure<br />
15, B-H. Vector means and central tendencies are calculated<br />
in the manner cited earlier.<br />
Figure 18 summarizes the general bimodal current flow<br />
tendencies measured along these cliffs. The number of mea-<br />
surements at each location (fig. 18) is indicated near the let-<br />
ter designating each location, and the lengths of the arrows<br />
in this diagram indicate relative significance of current flow<br />
in each direction. There is a stronger tendency of current<br />
flow towards the northeast and east at positions D, G, F,<br />
and H than towards the southwest or west (vector diagrams<br />
of figure 15, D, F, G, and H). At locations B, C, and E (fig.<br />
la), a stronger trend of current flow is indicated toward the<br />
northwest than toward the northeast. Position F also has a<br />
strong second order tendency to the northwest.<br />
Bimodal current flow in opposite directions, as indicated<br />
along these cliffs, is interpreted to be related to ancient tidal<br />
flat-current conditions. Using the directional data from figure<br />
PALEOENVIRONMENTS OF THE MOENAVE FORMATION<br />
C honnel<br />
no.<br />
I<br />
I<br />
TABLE 1<br />
SUMMARY OF CURRENT FLOW DATA IN THE<br />
CHANNELS OF THE AIRPORT ROADCUT<br />
N o.<br />
Meos<br />
111 ( 8 3 ..I I,." a.<br />
5<br />
I<br />
- 11.1.<br />
-<br />
Vector<br />
sum<br />
318'<br />
138"<br />
......<br />
, . ..., ..<br />
I"...", o..rl,o" .,"l,I."t<br />
III v. me., .<br />
Consistency<br />
ratio<br />
.95<br />
1.00<br />
FIGURE 15.-Vecror diagrams of paleocurrent rrends in all locations of study<br />
area in St. George.<br />
"'<br />
General<br />
trend<br />
310"
26 J. D. DAVIS<br />
18, the trend of a paleoshoreline can be inferred by drawing<br />
a dotted line approximately normal to the locations of bidi-<br />
rectional current flow. The approximation of the shoreline<br />
trend may help to establish a depositional relationship be-<br />
tween the channel deposits of the airport roadcut and the<br />
sandstone lenses of the Interstate 15 roadcut within the in-<br />
ferred tidal environment.<br />
FOSSILS<br />
Fossils are rare and poorly preserved in the Moenave sedi-<br />
ments of the study area, and they include trace fossils, bur-<br />
rows, and trails found mostly in mudstone layers just below<br />
surfaces of contact with siltstone and sandstone lenses. Very<br />
few burrows or trails were found at the airport location, but<br />
FIGURE 16.-location map of paleocurrent measurements along the erosional cliffs north of St. George Blvd.<br />
FIGURE 17.-location map of paleocurrent measurements for positions G and H<br />
those observed were somewhat U- or J-shaped. Average bur-<br />
row length measures 9 cm and .9 cm in diameter. Burrows<br />
were abundant in both siltstone lenses and mudstone layers<br />
in the natural cliffs north of St. George Boulevard and in<br />
the Interstate 15 roadcut but did not occur in any predict-<br />
able pattern of distribution. Most burrows were straight, ori-<br />
ented in an upright vertical position (fig. 19) or horizontally<br />
(fig. 20). Average lengths and diameters are 14 cm and .9 cm<br />
respectively. Modes of preservation are of two types: (1) as<br />
cavities (fig. 21) or (2) as solid casts (figs. 19 and 20).<br />
These burrows may be representative of three categories<br />
of ichnofaunal, or trace-fossil, burrowing structures: (1) feed-<br />
ing structures, or Fondinichnia, (2) dwelling structures, or<br />
Domichnia, and (3) escape structures, or Fugichnia. Feeding<br />
structures consist of temporary burrows of deposit feeders ex-
cavated while in search of food within the sediment or at<br />
the sediment surface. Burrow patterns typical of Fondinichnia<br />
are radial and U-shaped, i.e., Diplocraterion and Phycodes.<br />
Dwelling structures (Domichnia) include those burrow types<br />
which are more or less permanently inhabited by suspension<br />
feeders. These structures are cylindrical, having agglutinated<br />
or strengthened walls. They are also U-shaped and include<br />
Ophimorpha, Skolithos, and Arenicolites.<br />
Escape structures, or Fugichnia, are produced by bivalves<br />
and suspension feeders which uncover themselves after having<br />
been buried by influx of sediment, or burrow deeper into the<br />
sediment to offset erosion at the substrate surface. Fugichnia<br />
are not well understood but are considered to be a transition<br />
classification to feeding structures and Cubichnia, or resting<br />
traces. Examples may be Diplocraterion and Asteriacites.<br />
Ichnofaunas are environmentally significant because varia-<br />
tions in this faunal group can be used to infer both vertical<br />
and lateral facies changes in ancient sediments and hence<br />
may provide clues to viable paleogeographic reconstructions<br />
(Frey 1975). Ichnofossils found in the study area resemble<br />
species of the three groups Fugichnia, Fondinichnia, and Do-<br />
michnia, which are normally associated with the sandy shore<br />
of the littoral zone. This niche is somewhat exacting in that<br />
animals living in this zone must be able to tolerate strong<br />
current and wave action, desiccation, and rapid fluctuations<br />
PALEOENVIRONMENTS OF THE MOENAVE FORMATION 27<br />
- St<br />
in salinity and temperature. Toleration of such conditions is<br />
accomplished by escaping from the surface into permanent or<br />
semipermanent burrows. This response is reflected in the cor-<br />
responding trace fossils showing a preponderance of vertical<br />
burrows such as Skolithos, or "pipe rock", or U-shaped bur-<br />
rows as Arenicolites and Diplocraterion. The intertidal zone is<br />
characterized by abundant U-shaped burrows and burrows<br />
with protective linings.<br />
INTERPRETATION AND RECONSTRUCTION OF THE MOENAVE<br />
ENVIRONMENT OF DEPOSITION<br />
Interpretation I<br />
Collectively, the major Moenave characteristics of paleo-<br />
current trends, geometry, sedimentary structures, and, to a<br />
lesser degree, ichnofaunal types suggest that the deposition of<br />
the Moenave sediments in the St. George area was related to<br />
a tidal-flat system located peripherally on a larger delta.<br />
The major characteristics of the Moenave sediments<br />
found at the airport roadcut indicate that these deposits were<br />
formed in the subtidal zone where subaqueous conditions<br />
predominated over subaerial conditions (fig. 22). This zone<br />
occupies the area which extended landward about 1 m above<br />
mean sea level and seaward to a depth of several meters be-<br />
low sea level. The subtidal zone was submerged for at least<br />
one-half of the tidal cycle and thus was exposed subaerially<br />
George Blvd<br />
0 12 24 36 A8 60 72 Km<br />
FIGURE<br />
18.-Paleocurrent summary diagram of positions A-J. Sizes of arrows indicate relative stengths of current tendencies. Dotted line is inferred trend of<br />
paleoshoreline.
28 J. D. DAVIS<br />
the lesser amount of time. The main features of this zone<br />
are channels and sandbars characterized by megaripples, small-<br />
scale cross-bedding, and flaser, wavy, and lenticular bedding<br />
in the channel walls. Bipolar current flow produced herring-<br />
bone cross-bedding. Bioturbation is sparse. Alternating sand<br />
and mud layers are common and are caused by tidal phases<br />
of current and slack-water conditions (Reineck 1973).<br />
The thickness of the airport channel deposits and their<br />
FIGURE 19 -Vert~cal burrows<br />
size indicate that they were formed by strong incoming tidal<br />
currents flowing landward to the northeast. The large single<br />
channel (channel 5, fig. 14) may have been a major sub-<br />
aqueous channel in the subtidal zone while the smaller chan-<br />
nel undulations were parts of a tributary meander within the<br />
same location. Weak bimodal current flow measurements, in-<br />
dicating current flow in the opposite direction, suggest depo-<br />
sitional influences from ancient ebb currents flowing seaward<br />
toward the southwest. The low w/d ratios (less than 10:l)<br />
of the channels indicate that the channel fill material and the<br />
surrounding mudstone sediments were carried and deposited<br />
mostly by suspension, as in slack-water conditions where cur-<br />
rents are weak in the interim of tidal influx and ebb flow.<br />
The sandstone and siltstone lenses of the Interstate 15<br />
roadcut may have been produced by incoming tidal and re-<br />
gressive ebb currents in the intertidal zone of the tidal flat<br />
environment.<br />
Interpretation I1<br />
The intertidal zone occupies the area covered by high<br />
tide and low neap tides, and the tidal range may represent a<br />
vertical difference in water depth of 2 to 5 m (Reineck<br />
1973). The upper portion of the intertidal flat (high tidal<br />
zone) is subaerially exposed for the greatest periods of time<br />
during neap tidal stages. The lower portion is subject to<br />
daily flooding and is drained by numerous dendritic, linear,<br />
and meandering channels. These channels distribute water<br />
across the flats during flood tide and then collect and funnel<br />
it back in the opposite direction (seaward) during ebb tide.<br />
It is the tidal fluctuations of water level which produce the<br />
channels, runnels, and gullies on the intertidal flat. Currents<br />
of high tidal range excavate deeper channels than currents of<br />
low tidal range (Thompson 1968).<br />
Sediments of the intertidal flats are mostly fine-grained<br />
mud and silt and very fine sand. Gravels are rare, but mud<br />
clasts and shells may be abundant in tidal channel deposits.<br />
Most of the sediments of the intertidal zone have a charac-<br />
teristic distribution pattern: sediments of the high water level<br />
of this zone are muddy, but become more sandy in the lower<br />
level. This distribution pattern of sediment is due largely to<br />
the available energy and transportation mechanisms. Near the<br />
low water line the wave activity is strongest and active for<br />
I<br />
I<br />
i<br />
L<br />
-?RJ -<br />
h.<br />
.T ,<br />
FIGURE 20.-Horizontal burrows. FIGURE 21.-Burrows presewed as cavities
the longest time as compared to the higher parts of the in-<br />
tertidal zone. For this reason sand is concentrated in the<br />
lower intertidal zone.<br />
The sand flats of the intertidal zone arc characterized by<br />
well developed small-scale current and wave ripple cross-bed-<br />
ding. Flaser and wavy bedding are also present but less com-<br />
mon. Megaripples are common in intertidal channels, and<br />
some climbing ripple laminations may be found in the<br />
mouths of small channels and gullies.<br />
The most common bedding forms found in the mixed<br />
flat (sand and mud) environments are flaser, wavy, and len-<br />
ticular bedding (Reineck 1973), and all variations of thinly<br />
and thickly interlayered sand-mud beds. Point bar deposits, if<br />
present, may also have well-developed interlayered sand-mud<br />
bedding. Horizons of shells in their living positions are also<br />
common. Intraformational conglomerates composed of mud-<br />
stone balls, shells, and gravel, as shown in figure 9, are also<br />
commonly found in the intertidal zone (Thompson 1968).<br />
Slightly stronger landward tidal currents flowing north-<br />
ward excavated relatively shallow channels (less than 1.5 m),<br />
resulting in some of the thicker lenses in the central portion<br />
of the Interstate 15 roadcut. Regressive ebb flow funneled<br />
water seaward toward the southwest, modifying the tidal in-<br />
flux channels and scouring out narrow gullies and runnels<br />
which became filled with silt and sand carried by tidal cur-<br />
rents. The relatively thin layers or lenses of mudstone may<br />
have resulted from the accumulation of mud and fecal matter<br />
during the interim slack-water period. Sandstone and siltstone<br />
predominate over mudstone in this roadcut because this area<br />
probably was the sandy, lower intertidal flat where strong<br />
PALEOENVIRONMENTS OF THE MOENAVE FORMATION 29<br />
FIGURE 22.-Rcconst~ctcd model diagram of the Mocnavc tidal flat in the St. Gcorgc area<br />
paleocurrent tidal activity prevented the accumulation of<br />
mud.<br />
Reconstruction of thc Mocnavc<br />
Tidal Flat Environment<br />
During the late Middle to Late Triassic Period, westward<br />
flowing fluvial systems drained the Colorado Plateau region<br />
and deposited the sediments which comprise the Glen Can-<br />
yon Group of the Four Corners region and southwestern<br />
Utah (Harshbarger et al. 1957). The Moenave Formation may<br />
have been deposited in a tidal flat system in the St. George<br />
area as suggested from evidences presented in this study. At<br />
some locations in southwestern Utah, the Moenave and<br />
Kayenta formations have sedimentological characteristics re-<br />
lated to lacustrine, or fluvial-deltaic environments (Wilson<br />
1959; Harshbarger et al. 1957). McKee et al. (1959) show<br />
that miogeosynclinal deposits typical of a continental shelf<br />
were deposited in southeastern Nevada and the extreme<br />
southwest border of Utah. The Dinosaur Canyon Member of<br />
the Moenave Formation in the St. George area, then, may<br />
have occupied a peripheral position on a tide-dominated delta<br />
which bordered on a shallow sea to the southwest and west<br />
much the same, by analogy, as the tidal flat situated on the<br />
northwestern flank of the delta formed by the Colorado Riv-<br />
er in the Gulf of California (Meckel 1975). Within this re-<br />
gional framework, and from the position of the shoreline in-<br />
ferred from figure 18, aspects of the Moenave tidal<br />
environment in the St. George area can be defined.<br />
Figure 22 reconstructs the ancient tidal flat in the St.<br />
George study area. Numbers 1-4 are locations in the study<br />
I Airpart Roadcut<br />
2 1-15 Roadcut<br />
3-4 Natural Cliffs<br />
ARROWS ARE PALEOTIDAL TRENDS
30 J. D. DAVIS<br />
area and indicate their relative position in the reconstructed<br />
model. A seaward transition to deeper portions of the tidal<br />
flat west of Middleton Black Ridge roadcut is suggested by<br />
the increasing thicknesses of sandstone lenses and mudstone<br />
layers in the natural cliffs. The position of the subtidal zone<br />
is indicated by the thick channel pods and thick mudstone<br />
layers which enclose the channel sandstone deposits in the<br />
airport roadcut. The channels in the airport roadcut may rep-<br />
resent remnants of major subtidal channels through which<br />
strong incoming northeast-flowing tidal currents were fun-<br />
neled. Some ebb flow through these channels toward the<br />
southwest is indicated from paleocurrent data (figs. 14 and<br />
15, I and J, and table 1).<br />
Regional bidirectional current flow data collected at<br />
Ivins, Utah, and above the Visitors' Center in Zion Canyon<br />
suggest that this tidal system occupied an area at least 100<br />
km wide (fig. 23).<br />
SUMMARY<br />
Spectacular channels and bundles of lenticular sandstone<br />
sequences in the Dinosaur Canyon Member of the Moenave<br />
Formation in St. George, Utah, are exposed by roadcuts near<br />
the municipal airport and in Middleton Black Rdge along<br />
Interstate 15. Orientation and geometry of the channels and<br />
lenticular sandstone and siltstone bodies, fining upward of all<br />
vertical sequences, and bidirectional current flow measurements<br />
indicate that these deposits were formed in a tidal flat<br />
system.<br />
The bundlelike appearance of the sandstone and siltstone<br />
lenses of the Interstate 15 roadcut and their hig' h w/d ratios<br />
(greater than 40) suggest relatively unstable or fluctuating<br />
depositional conditions in which sediments were carried by<br />
bed-load orocesses in shallow water. Consistent bidirectional<br />
1<br />
current flow measurements in this roadcut indicate deposition<br />
occurred in the intertidal zone of the tidal flat.<br />
FIGURE 23.-Regional paleocurrent trends.<br />
/'<br />
Km<br />
I I I I<br />
0 16 32 48 64<br />
Low w/d ratios (less than 10) and type of channel filling<br />
mechanisms inferred from the nature of bedding within the<br />
thick channel deposits of the airport roadcut indicate that<br />
transportation and deposition of these sediments was mostly<br />
by suspension processes in relatively deeper water than is rep-<br />
resented by the sediments of the vertical sequences at the In-<br />
terstate 15 roadcut. The channel deposits and thick mudstone<br />
layers which surround these channels may represent deposi-<br />
tion in the subtidal zone.<br />
Current flow data indicate a possible meander pattern of<br />
the four interconnected channel undulations and intersection<br />
with the large single channel undulation exposed at the<br />
north end of this roadcut. Regional bidirectional current<br />
flow data collected at Ivins, Utah, and by the Visitors' Cen-<br />
ter, Zion Canyon National Park, suggest that the Moenave<br />
tidal system extended a distance 100 km in width and may<br />
have occupied a peripheral position within a large prograding<br />
fluvial-deltaic system which drained the Colorado Plateau to<br />
the east and dumped its sediment load into the shallow back<br />
arc sea of eastern Nevada.<br />
REFERENCES CITED<br />
Burchfiel, B. C., and Davis, G. A., 1975, Nature and controls of cordilleran<br />
orogenesis, western United States: extensions of an earlier synthesis:<br />
Amer. Jour. Sci., v. 275-A, p. 363-96.<br />
Colbert, E. H., and Mook, C. C., 1951, The ancestral crocodilian Pro-<br />
tosuchus: Amer. Mus. Natl. Hist. Bull., v. 97, arr. 3, p. 149-82.<br />
Day, B. S., 1967, Stntignphy of the upper Triassic Moenave formation of<br />
southeastern Utah: Master's thesis, Univ. of Utah.<br />
Frey, R. W., 1975, The study of trace fossils: Springer-Verlag, New York,<br />
562 p.<br />
Ginsburg, R. N. (ed.), 1975, Tidal deposits: Springer-Verlag, New York, 428<br />
P.<br />
Gregoty, H. E., 1948, <strong>Geology</strong> and geography of central Kane County, Utah:<br />
Geol. Soc. Amer. Bull., v. 59, p. 211-47.<br />
, 1950a, <strong>Geology</strong> of eastern Iron County, Utah: Utah Geol. and Min-<br />
eni. Sum. Bull., no. 37, 153 p.<br />
Zion (25)<br />
290/ 12 7
PALEOENVIRONMENTS OF THE MOENAVE FORMATION<br />
, 1950b, <strong>Geology</strong> and geography of the Zion Park reglon, Utah and<br />
Anzona U.S Geol. Surv. Prof. Paper 220, 200 p<br />
Rcineck, H E., and Slngh, I B, 1967, Pnmary sed~mentary strucrures rn the<br />
Recent sediments of the Jade, North Sa: Marine Geol., v. 5, p. 227-<br />
Gregory, H E., and Wrllrams, N C., 1947, Zion National Monument, Utah<br />
35<br />
Geol. Soc Amer. Bull., v 58, p 211-44<br />
Schumm, S A, 1968, Speculations concemlng paleohydrologic controls of<br />
Harshbatger, J W, Rcpenning, C A,, and Irwrn, J. H., 1957, Stratigraphy of terrestrial scd~mentation: Geol. Soc. Amer. Bull, v 79, p 1573-88<br />
rhe uppermost Triassic and Jurasslc rocks of rhe Navajo country US Thompson, R W, 1968, Trdal flat sedimentation on the Colorado R~vcr del-<br />
Geol. Surv Prof Papcr 291, 74 p<br />
ta, northwestern Gulf of Calrfornra. Geol Soc Amer Mem 107, 133<br />
McKee, E D, 1957, Flume expenments on the productron of stratrficatron<br />
and crossstratrficatron~ Jour. Sed. Petrol. 27, p 129-34<br />
McKce, E D , et a1 , 1959, Paleotectonic maps of the Triassic system MIX.<br />
Geol. Invest Map 1-300, US. Geol. Survey<br />
P.<br />
Ward, L. F, 1901, <strong>Geology</strong> of the Little Colorado Valley Amer. Jour Sci<br />
(4) v. 12, no 72, p 4-1-413<br />
Weller, J M , 1960, Stnr~graph~c principles and practrce Ha~per, New York,<br />
Mcckel, L D., 1975, Holocene sand bodres In the Colorado Rrver delta area, 725 p<br />
northern Gulf of Cahfornra: Deltas: Houston Geol SUN<br />
W~lson, R. F, 1959, The strat~graphy and scdrmentology of the Kayenta and<br />
Pcttrjohn, F. J., Potter, P. E, and Srcver, R.. 1973, Sand and sandstone. Mocnave formarrons, Vamrllron Clrffs regron, Utah and Anzona<br />
Springer-Valag, New York, 618 p.<br />
Rancck, H E., 1973, Dcposit~onal sedimentary envrronments Spnnget-Valag,<br />
New York.<br />
Ph D drssertat~on Stanford Unlv<br />
3 1
Foraminifera1 Abundance Related to Bentonitic Ash Beds in the<br />
Tununk Member of the Mancos Shale (Cretaceous) in Southeastern Utah*<br />
ABSTRA~.-The Tununk Member of the Cretaceous Mancos Shale contains<br />
several thin bentonitic ash beds that are particularly well exposed berween<br />
Caineville, Utah, and Capitol Reef National Monument. Observations have<br />
been made on samples collected at stratigraphic intervals of 5 to 10 cm for<br />
five of the lower ash beds and intervening siltstones near Caineville, west of<br />
Utah Highway 24. Foraminifen present consist of 11 families, represented by<br />
17 genera, and are mainly planktonic calcareous species. Ash falls did not result<br />
in the mass extinction of species. Numbers of specimens decrease in the<br />
lowermost parts of each ash bed, whereas the middle part of each ash shows<br />
a population bloom up to 12,000 foraminifera per gram. At the top of or<br />
immediately above each ash the number of specimens decreases, and another<br />
population bloom, up to 18,000 foraminifera per gram, occurs in the siltstone<br />
above the ash. The increase in numbers within each ash suggests that<br />
the ash falls provided nutrients for organisms upon which the foraminifera<br />
may have fed.<br />
INTRODUCTION<br />
Foraminifera are particularly abundant within and around<br />
bentonite ash beds in the Tununk Shale, and it is thought<br />
that the ash beds have a relationship to the large foraminifera1<br />
numbers. The fossiliferous Tununk Shale, of Late Cretaceous<br />
(Turonian-Cenomanian) age, is the lowermost member<br />
of the Mancos Shale in southeastern Utah (fig. 1) and<br />
was named by Gilbert (1877) for exposures in the Henry<br />
Moun rains. Several thin bentonite beds occur within the Tununk<br />
Shale and record ash falls from distant volcanoes.<br />
Maxfield (1976) observed that the numbers of foraminifera<br />
increased near the ash beds and that further research<br />
(pers. comm. 1975) was needed to determine the effects of<br />
ash falls on the foraminifera1 populations. Foraminifera were<br />
recovered from five of the ash beds and surrounding siltstones,<br />
from the lower beds of the member. Eighty-three -<br />
samples were examined for foraminifera.<br />
The study area is located 3.25 km west of Caineville,<br />
Utah (fig. 2), along the valley west of the Caineville Reef.<br />
The section sampled is 250 m northwest of Utah Highway<br />
24, on the north side of the series of hills forming the summit<br />
between Caineville Wash and the Fremont River, in SE-<br />
NW% Sec. 3, T. 29 S, R. 8 E. The sampled beds dip 24' to<br />
the northeast off the East Caineville Dome and occur 12 to<br />
33 m above the Gyphaea newberryi coquina, which here is at<br />
the base of the Tununk Shale (Lessard 1973, p. 2) (figs. 1,<br />
3). The bentonitic ash beds are white and unconsolidated<br />
and are interbedded with fissile, dark gray siltstones. The Tununk<br />
Member is a valley-forming unit and is vertically gradational<br />
from the thin, discontinuous, uppermost sandstone of<br />
the underlying Dakota Sandstone and to the overlying Ferron<br />
Sandstone Member of the Mancos Shale.<br />
Acknowledgments<br />
The writer would like to express gratitude to Dr. J.<br />
Keith Rigby for his guidance and direction in completing<br />
this thesis and for the use of his microscope. Dr. E. Blair<br />
Maxfield provided valuable assistance in helping identify the<br />
foraminifera and in lending some of his negatives. Dr. Har-<br />
old J. Bissell is appreciated for reading the manuscript and<br />
offering suggestions. Thanks go to Tom Chidsey, Allen<br />
Driggs, Paul Gilmer, Bob Lindsay, and Debbie Reeder for<br />
their help in collecting the samples from the ash beds. Finan-<br />
cial assistance was provided by the American Association of<br />
Petroleum Geologists, Sigma Xi, and the Department of Ge-<br />
ology, <strong>Brigham</strong> <strong>Young</strong> <strong>University</strong>.<br />
Previous Work<br />
Lessard (1973) studied the general paleoecology of the<br />
Tununk Member of the Mancos Shale and described 20 spe-<br />
cies of foraminifera. Maxfield (1976) established a foraminifer-<br />
a1 biostratigraphic zonation of the Mancos Shale, including<br />
the Tununk Member, and described 30 species of foraminifera<br />
from Tununk beds.<br />
<strong>Young</strong> (1951, p. 48) found no foraminifera in bentonite<br />
FIGURE 1.-Stratigraphic section. A. General srrat~graphy, B. Tununk<br />
stratigraphy.<br />
.A thcsir pwvnrcd to rhc Dcprrmmr of Gmlogy. <strong>Brigham</strong> <strong>Young</strong> Univcnq, in partla1 fulfillmcnr of rhc rcqutrcmcnrs for the dcgrcc Mvrer of Scxmcc, Apnl 1977: J. Knrh Rlgby, rhars chairman.<br />
33
34 R. I.. BAGSHAW<br />
beds in the Frontier Formation in Montana. He suggested<br />
that conditions unfavorable for their existence were present<br />
at the time of deposition or that they might have been de-<br />
stroyed by ground water action after deposition of the beds.<br />
Miller (1968, p. 9) reported that the faunal suite of foramini-<br />
fera in the Smoky Hill Member of the Niobrara Formation<br />
in Kansas, which has bentonite beds, lacked arenaceous fora-<br />
minifera and that most of the genera in the area were stun-<br />
ted. Reeside (1957, p. 520-22) suggested that Turonian vol-<br />
canism had little effect on life conditions in western<br />
Cretaceous seaways, but that Cenomanian volcanism was sig-<br />
nificant. However, he did not elaborate on those conclusions.<br />
The most detailed published observations on ash-related<br />
foraminiferal distributions is that of Mello (1969, p. 24). He<br />
studied the Pierre Shale in South Dakota and observed that<br />
at three of his measured sections, where bentonite beds were<br />
significant, greater numbers of foraminiferal species occur be-<br />
low the ash than above and that the number of arenaceous<br />
species was reduced by 50 percent in two of the three cases.<br />
He believed that this effect was restricted, however, for it<br />
was not apparent in any of his other measured sections. His<br />
FIGURE 2.-Ink map.<br />
samples were collected at ten-foot intervals, however, and he<br />
most likely missed sampling some of the ash beds.<br />
Wilcox (1957, p. 456), after studying recent ash falls in<br />
Alaska, thought that any effects of ash falls on marine life<br />
were only temporary, judging from his review of the scanty<br />
literature. Finger (1976) conducted numerous studies on fora-<br />
minifera within and around a volcanic atoll in Antarctica and<br />
found large numbers of calcareous species and few arenaceous<br />
ones after two of the three eruptions studied.<br />
F~eld and Laboratory Methods<br />
The study area was chosen because many well-exposed<br />
ash beds occur in a thin sequence of tilted beds (fig. 3)<br />
which allow close sampling. The selected ash beds and inter-<br />
vening dark gray siltstoncs and shale beds were trenched<br />
with shovels to provide fresh surfaces and prevent sample<br />
contamination (fig. 4). Samples weighing approximately 250<br />
grams each were collected at 5- to 10-centimeter intervals<br />
through the ash beds and from approximately 20 centimeters<br />
below to 30 centimeters above each bentonite.<br />
One-hundred-gram portions were soaked in water con-<br />
taining a wetting agent for several days. When disaggregated,<br />
the samples were washed on a 200-mesh screen. After drying,<br />
the residues were split, and 1/64 of the original residue was<br />
picked when it became apparent that processing all of it was<br />
virtually impossible because each sample contained a large<br />
number of foraminifera. The foraminifera retained on a 100-<br />
mesh screen were picked. Residues smaller than the 100-mesh<br />
screen were again split into varying sizes from 1/16 to<br />
1/4036 original residue weight and picked. Foraminifera<br />
smaller than 100-mesh were not picked in ashes 3 and 4.<br />
Picked specimens were identified using a Wild binocular mi-<br />
croscope. All specimens other than those figured were<br />
mounted on gum-tragacanth-coated microfiaunal slides and are<br />
in collections of the Department of <strong>Geology</strong>, <strong>Brigham</strong><br />
<strong>Young</strong> <strong>University</strong>.<br />
The figured specimens were mounted on electron micro-<br />
scope stubs and were photographed by the scanning electron<br />
microscope at <strong>Brigham</strong> <strong>Young</strong> LJniversity Electron Optics<br />
Laboratory. Figured specimens are housed in the type collec-<br />
tions of the <strong>Brigham</strong> <strong>Young</strong> liniversity Cieology Depart-<br />
ment.<br />
FAUNA<br />
The microfauna of the sampled Tununk Shale intervals is<br />
composed primarily of foraminifera. A few ostracods, fish<br />
teeth, and Inaceramus prisms were found. Fragments of In-<br />
oceramus were the only macrofaunal elements observed. Exam-<br />
ination of the samples was not conducted fttr diatoms, radio-<br />
larians, spores, or pollen.<br />
The Foraminiferida of the Tununk Shale are represented<br />
by 11 families, the Saccamminidae, Hormosinidae, Lituolidae,<br />
Nodosariidae, Turrilinidae, Hetcrohrlicidae, Planomalinidae,<br />
Rotaliporidae, Cibicidae, Caucasinidae, and Anomalinidae. The<br />
first three families are composed of agglutinated forms, and<br />
the others are composed of calcareous types. These families<br />
are represented by 17 genera and 20 species.<br />
The Nodosariidae are represented by the greatest number<br />
of genera (3) and species (4). They occur sporadically and in<br />
very small numbers throughout the sampled intervals. Speci-<br />
mens of the Turrilinidae, represented by Prdehuiz~ninu prolixu<br />
(Cushman and Parker 1935), ate extremely abundant and<br />
constitute the largest foraminiferal numbers in most of the<br />
sampled intervals for all the ashes. The Heterohelicidae, repre-
FORAMINIFERAL ABUNDANCE RELATED TO BENTONITIC ASH BEDS 35<br />
FIGURE ).-View of Tununk stratigraphy: Fcrron Sandstone (F), Gtypbaea netuberryi horizon (G), ash 1 (I), ash 2 (2).<br />
sented by Heterohelix globulosa (Ehrenberg) 1840, and Rota-<br />
liporidae, represented by Hedbergella delriomsis (Carsey 1954),<br />
also constitute large foraminiferal numbers throughout the<br />
Tununk section. The three agglutinate species, Saccamminna<br />
complanata (Franke 1912), (?) Reopbax sp., and Ammobaculites<br />
wenonahae Tappan 1960 are very rare in the section and occur<br />
mainly in ash 5 (fig. 1). The fauna represents Maxfield's<br />
Zone A (1976, p. 78) based upon the occurrence of Ammo-<br />
baculites wenonahae and Planulina austinana Cushman 1935 in<br />
the sampled intervals. His Zone A is composed primarily of-<br />
planktonic forms and nodosarids and buliminids. The sec-<br />
tions studied in this paper, however, have only a few more<br />
planktonic than benthonic forms because the buliminids are<br />
abundant throughout.<br />
Most of the foraminifera are smaller than those desig-<br />
nated as type specimens by the original workers. Several au-<br />
thors thought that smaller specimens are dwarfed or stunted<br />
by unfavorable environmental conditions. Apparent stunting<br />
in Cretaceous foraminifera has been reported by Green (1959,<br />
p. 36) in the Allen Valley Shale of Utah; Miller (1968, p. 9)<br />
in the Smokey Hill Member of the Niobrara Formation in<br />
Kansas; and Lessard (1973, p. 10) in the Tununk Shale in<br />
Utah. Loeblich and Tappan (1964, p. 125), however, state<br />
that smaller specimens indicate unusually favorable conditions<br />
and rapid reproduction.<br />
PALEOECOLOGY<br />
Ash 1 is 40 cm thick and occurs 12 m above the base of<br />
the Tununk Shale. The number of foraminifera per gram de-<br />
FIGURE 4. View of trench through ash 2<br />
creases in the lower part of the ash (fig. 5), increases to<br />
11,876 per gram in the upper part, and then decreases again<br />
at the top of the ash. The foraminiferal number increases in<br />
the siltstone above the ash. The sampled interval contains<br />
predominantly benthonic foraminifera (57-92 percent). The<br />
percentage of planktonic forms is greatest at the base of the<br />
ash (43 percent) and above the ash (42 percent). The ratio<br />
between the various foraminifera1 families remains approx-<br />
imately the same throughout the interval, with a dominance<br />
of Turrilinidae and Heterohelicidae (table 1).
36 R. L. BAGSHAW<br />
Ash 2 is 22 m above the base of the Tununk Shale and<br />
is 22 cm thick. The number of foraminifera per gram de-<br />
creases in the lower part of the ash, but then increases in the<br />
middle, only to decrease again at the top. The number also<br />
shows two increases separated by a minor decrease in the<br />
siltstone above the ash (fig. 6). Foraminifera in the ash are<br />
dominated by planktonic forms (haw percent), but ben-<br />
thonic forms dominate below the ash (50-85 percent) and 30<br />
cm above the ash (53 percent). The ratios between the fora-<br />
miniferal families vary a little, however: Rotaliporidae, Heter-<br />
ohelicidae, and Turrilinidae comprise most of the forms<br />
(table 2).<br />
Ashes 3 and 4 were sampled as a check on the other<br />
bentonite beds, but only the foraminifera larger than a 100-<br />
mesh screen were picked. Therefore, the results do not reflect<br />
the abundance of Guembelitria cretacea Cushman 1935, Globi-<br />
gerinelloides upera (Ehrenberg 1854), Carridella tegulata (Reuss)<br />
1951, or the Turrilinidae since they pass through a 100-mesh<br />
screen.<br />
Ash 3 is 41 cm thick and is 30 rn above the base of the<br />
Tununk Shale. The numbers of foraminifera are low below<br />
FIGURE >.-Graph of fonminifenl abundance in ash 1.<br />
/I per gram I per qram ( per gram I per gram<br />
NUMBERS PER GRAM<br />
the bottom of the ash (fig. 7), increase in the lower half of<br />
the ash, but then decrease in the upper quarter of the ash.<br />
Numbers increase again in the uppermost part of the ash<br />
and in the basal part of the siltstone above. Numbers de-<br />
crease at approximately 10 cm above the ash. Foraminifera]<br />
assemblages in the ash are dominated by planktonic forms<br />
(57-85 percent), except for one interval near the top of the<br />
ash. Families present maintain nearly constant abundance ra-<br />
tios throughout the ash, with Rotaliporidae being dominant<br />
(table 3).<br />
Ash 4 is 21 cm thick and is 31 m above the base of the<br />
Tununk Shale. The foraminifera1 number decreases at its<br />
base, but increases vertically through the ash. Numbers de-<br />
crease in the siltstone immediately above the ash, but then<br />
increase again (fig. 8). The ash contains principally plankton-<br />
ic forms (55-89 percent), with Hedhergella delriwnsis (Carsey<br />
1954) dominating the assemblage. Numbers of Anornalinidae<br />
and Cibicidae stay fairly constant throughout the sampled in-<br />
terval (11-35 per gram) (table 4).<br />
Ash 5, 32 m above the base of the Tununk Shale, con-<br />
tains a sequence of separate ash falls within the 195 cm that<br />
TABLE 1<br />
Foraminifera1 Occurrence in Ash I<br />
Nlrmber Planktonic Plumber Number Number<br />
1 per qram 1 percentage I per gram I per qram / per /=am<br />
Benthonic<br />
Number<br />
per gram<br />
Benthonic<br />
Percentaqe<br />
69<br />
58<br />
84<br />
81<br />
82<br />
76<br />
78<br />
74<br />
74<br />
72<br />
59<br />
5 7<br />
89<br />
92
were sampled. The entire sampled interval differs from ashes<br />
1 and 2, for no specimens of Gumbelitria cretacea were recov-<br />
ered (table 5).<br />
The first ash within the sequence, ash 5A, is 28 cm<br />
thick. Numbers of foraminifera decrease at its base, increase<br />
in its middle part, and decrease at its top (fig. 9). The fora-<br />
minifera are mixed benthonic and planktonic, with plankton-<br />
ic forms dominating below, in the lower middle part, and at<br />
the top. Within the ash, Praebulimina prolixa (Cushman and<br />
Parker 1935) dominates the central part, and Hedbergela &-<br />
n'oenn's, Planulina austinana Cushman 1935, Gavelinella neki<br />
(W. Berry 1929), and juvenile forms dominate. The ratio be-<br />
tween families remains approximately constant as in the oth-<br />
er ashes.<br />
Ash 5B is 73 cm thick and occurs 23 cm above ash 5A.<br />
Because of its thickness, it may be two ashes with no appar-<br />
ent stratigraphic break between them. Numbers of foramini-<br />
fera increase at the bottom of the ash, but then decrease in<br />
FIGURE 6.-Graph of foraminifera1 abundance in ash 2.<br />
FORAMINlFERAL ABUNDANCE RELATED TO BENTONITIC ASH BEDS<br />
NUMBERS P E R GRAM<br />
the lower third (fig. 9). In the middle third of the bed, fora-<br />
minifera again increase and decrease. In the upper third,<br />
numbers increase but then show an oscillating decline to the<br />
top of the ash. The numbers increase in the siltstone above<br />
the ash. The forms within ash 5B are mainly planktonic (50-<br />
65 percent), but with benthonic forms dominating twice<br />
(table 5) within the upper half of the ash (55-57 percent).<br />
None of the species present tends to dominate the ash, but<br />
ratios between the species remain approximately constant<br />
throughout.<br />
Ash 5C is the thinnest ash studied, for it is only 10 cm<br />
thick (fig. 9). It is separated from ash 5B by 11 cm of silts-<br />
tone and from ash 5D by 5 cm of siltstone. The numbers of<br />
foraminifera in ash 5C increase from below the ash steadily<br />
to 3 cm from its top. Numbers decrease from there into the<br />
lower part of ash 5D. Assemblages in ash 5C are planktonic<br />
(53-59 percent), and Hedbergella delrioensis dominates the<br />
forms in the central part of the ash.<br />
TABLE 2<br />
Foraminifera1 Occurrence in Ash 2<br />
37
38 R. L. BAGSHAW<br />
Ash 5D is 25 cm thick. The foraminifera] numbers de-<br />
cline in the lower third of the ash (fig. 9), but then increase<br />
in the upper third, only to decline immediately above the<br />
ash. In the siltstones above the ash, the number of foramini-<br />
fera increases and declines in a pattern similar to that in<br />
ashes 2 and 3. The foraminifera in ash 5D are mainly plank-<br />
tonic (54-78 percent) except in the lower 10 cm of the ash<br />
where benthonic forms, mainly Praebulimina prolixa, dominate<br />
(51-62 percent). Above the benthonic layers of the ash, Hed-<br />
bergella delrioensis is the dominant planktonic form.<br />
In summary, the effects on foraminifera of the five ash<br />
falls studied are approximately the same. All the ashes except<br />
5B and 5D show a decrease in the foraminiferal number at<br />
the ash base, but a population bloom within the ash, fol-<br />
lowed by another decrease in numbers occurring near the top<br />
of the ash. Another population bloom occurs immediately<br />
above the ash.<br />
All the ashes, except ash 1, are dominated by planktonic<br />
foraminifera, mainly Hedbergella delrioensis and Heterobelix<br />
globulosa (Ehrenberg) 1840. Praebulimina prolixa is the domi-<br />
nant benthonic species. The ratio between the species con-<br />
tained within each ash remains approximately equal, with<br />
very little domination by any one species. It is suggested that<br />
FIGURE 7.-Graph of foraminifera1 abundance in ash 3<br />
Interval<br />
66-76 cm<br />
61-66<br />
56-61<br />
Total<br />
Number<br />
per gram<br />
147<br />
242<br />
324<br />
40-46 19<br />
::::: I<br />
8-15<br />
2-0<br />
70<br />
20<br />
21<br />
131<br />
*Not in sizes picked<br />
: $<br />
'v .rl<br />
-4 e * -4<br />
? 2<br />
Number<br />
per gram<br />
75<br />
157<br />
136<br />
215<br />
0.6<br />
8<br />
9<br />
4 1<br />
12<br />
12<br />
97<br />
.+ H<br />
N<br />
(U P Z1<br />
0 2<br />
* 2 2<br />
0<br />
2<br />
Number<br />
per gram<br />
-<br />
30<br />
4 3<br />
68<br />
164<br />
6<br />
4<br />
2<br />
10<br />
2<br />
0.6<br />
15<br />
'+<br />
u<br />
*<br />
'* u<br />
N 0<br />
(U 0<br />
oJ 8<br />
Number<br />
per gram<br />
~p<br />
NUMBERS PER G R A M<br />
the ash fell and, after the initial shock on the foraminifera<br />
population, provided nutrients which created population<br />
blooms. When the immediate nutrient supply was exhausted,<br />
the numbers of foraminifera dropped. The return to normal<br />
marine conditions or further solution of the ashes might<br />
have caused the population bloom above each ash.<br />
Maxfield (1976, p. 82) postulates the depth of the Tu-<br />
nunk Sea to be 22.5 to 60 m (75-200 ft.). Lessard (1973, p.<br />
16) concludes that the water was W to 180 m (300-600 ft.)<br />
deep, as indicated by the dominance of planktonic species.<br />
Both Lessard and Maxfield suggest that the distance from<br />
shore is more of a factor determining the high planktonic as-<br />
semblage than water depth. This writer agrees with Max-<br />
field's conclusion regarding water depths and also with the<br />
idea that distance from shore determines the planktonic as-<br />
semblage. The environment of the sampled intervals in this<br />
study is interpreted as being a prodeltaic sequence.<br />
The Tununk Sea was of normal salinity as suggested by<br />
the presence of authigenic glauconite (Lessard 1973, p. 15)<br />
and the lack of agglutinated species (Maxfield 1976, p. 82).<br />
Greiner (1969, p. 169) states that hyaline calcareous foramini-<br />
fera live in water with moderate salinity and temperature-<br />
also with a moderate calcium carbonate content. The Tu-<br />
TABLE 3<br />
Foraminifera1 Occurrence in Ash 3<br />
Planktonic<br />
Number<br />
per gram<br />
-- -<br />
105<br />
200<br />
204<br />
369<br />
6<br />
12<br />
11<br />
51<br />
14<br />
12<br />
112<br />
Planktonic<br />
Percentage<br />
71<br />
82<br />
63<br />
66<br />
24<br />
63<br />
69<br />
7 3<br />
70<br />
57<br />
85<br />
.<br />
0 n a m a<br />
.d<br />
F .A<br />
.A c<br />
4 .A<br />
.4 m<br />
* U m<br />
k :<br />
Number<br />
per gram<br />
-<br />
w<br />
2<br />
I :<br />
m -4<br />
s e<br />
0 4<br />
NUT%=<br />
per gram<br />
13<br />
16<br />
38<br />
61<br />
2<br />
1<br />
3<br />
0<br />
0<br />
0.6<br />
2<br />
4 a<br />
u . C w<br />
.: b<br />
z 3<br />
Number<br />
per gram<br />
30<br />
2 5<br />
81<br />
121<br />
17<br />
5<br />
2<br />
18<br />
6<br />
7<br />
22<br />
Benthonic<br />
Number<br />
per gram<br />
4 3<br />
41<br />
119<br />
182<br />
19<br />
6<br />
5<br />
18<br />
6<br />
7<br />
24<br />
Benthonic<br />
Percentage<br />
--<br />
29<br />
18<br />
37<br />
34<br />
76<br />
37<br />
31<br />
27<br />
30<br />
43<br />
15
nunk Sea in which the studied sequence accumulated was a<br />
warm shallow sea.<br />
Turbidity created by the ash falls decreased the number<br />
of calcareous benthonic species, as calcareous planktonic<br />
forms become more dominant in the four upper ash beds.<br />
These results differ slightly from those of Loeblich and Tap-<br />
pan (I%, p. 133-34). They noted that bentonitic sediments<br />
commonly carry radiolarians and diatoms, and that these<br />
forms occur in an inverse ratio to the numbers of foramini-<br />
fera. It is then suggested that ash falls increased the turbidity<br />
and allowed the survival of planktonic siliceous forms, but<br />
greatly reduced the calcareous foraminiferal faunas.<br />
CONCLUSIONS<br />
The Tununk Member of the Upper Cretaceous Mancos<br />
Shale represents a transgressive seaway. The sediments are<br />
prodeltaic siltstones with interbedded bentonite beds derived<br />
from volcanic ash falls originating far to the west. The sea<br />
was shallow, of normal salinity and moderate temperature.<br />
Five bentonite ash beds in the lower Tununk Shale were<br />
sampled on 5- to 10-cm intervals to determine the effect of<br />
ash falls on the foraminifera inhabiting the Tununk sea.<br />
Eleven foraminifera families, represented by 17 genera, were<br />
recovered. Assemblages for each ash are predominately plank-<br />
tonic, except for ash 1 where benthonic forms are most com-<br />
mon.<br />
Each of the ash sequences which was totally picked<br />
shows that the number of foraminifera decreases at the base<br />
FIGURE 8.-Graph of foraminiferal abundance in ash 4.<br />
Interval<br />
-- ~<br />
- ~-<br />
Total<br />
umber<br />
per gram<br />
.<br />
43-50 cm<br />
130<br />
1<br />
38-43<br />
77<br />
30-38 --r 162<br />
25-30<br />
141<br />
15-20 1 115<br />
6-15 144<br />
2-8 1 19<br />
*Not in sizes picked<br />
. I<br />
rn<br />
'L1 m<br />
.rl .A E<br />
? 2<br />
Number<br />
per gram<br />
FORAMINIFERAL ABUNDANCE RELATED TO BENTONITIC ASH BEDS 39<br />
.r u u<br />
2 2<br />
0 - Y 2 2 o<br />
2%<br />
Number<br />
per gram<br />
106<br />
0<br />
42 1 0<br />
;<br />
115<br />
123<br />
1.:<br />
15<br />
.+ u<br />
'* *. u<br />
N (U<br />
a (U 0 u<br />
It<br />
u" B<br />
Number<br />
per gram<br />
of each ash, increases within the ash, and decreases at the<br />
top or immediately above the ash. The foraminifera popu-<br />
lation also increases above each ash. It is suggested that the<br />
ashes provided nutrients for organisms upon which the fora-<br />
minifera fed and thus created a circumstance favorable for<br />
the bloom within the ash, judging from the large number of<br />
small adult and immature forms in each ash and the slight<br />
number of large forms. Initial shock caused by the ash fall<br />
most likely created the decrease in numbers at the base of<br />
the ashes. The reason for the decrease in numbers near the<br />
top of the ash may be nutrient depletion caused by the pop-<br />
ulation's multiplying at a rate faster than nutrients could be<br />
supplied. The population bloom above each ash may be re-<br />
lated to an increase in nutrients and food supply. For ex-<br />
ample, diatoms or radiolarians may have flourished immedi-<br />
ately following the ash accumulation.<br />
Further study needs to be conducted on the diatom and<br />
radiolarian populations to evaluate variations in their num-<br />
bers as significant food sources. Other Cretaceous bentonite<br />
beds should be studied to see if foraminiferal numbers show<br />
parallel marked fluctuations.<br />
SYSTEMATIC PALEONTOLOGY<br />
The classification followed here is that of Loeblich and<br />
Tappan (1964) and Maxfield (1976). No synonymies are pre-<br />
sented, except for Cassidela tegulata (Reuss) 1951, since the<br />
main emphasis of this paper is the relationship of the fora-<br />
minifera to the ash beds and not systematics. Current synon-<br />
ymies are found in Maxfield (1976).<br />
NUMBERS P E R G R A M<br />
TABLE 4<br />
Foraminifera1 Occurrence in Ash 4<br />
Planktonic<br />
umber<br />
per gram<br />
106<br />
42<br />
117<br />
125<br />
8 3<br />
115<br />
15<br />
Planktonic<br />
Percentage<br />
82<br />
55<br />
72<br />
89<br />
7 2<br />
73<br />
79<br />
.<br />
a I<br />
2 2<br />
C c<br />
-rl<br />
rl .3<br />
.rl Vl 4<br />
Number<br />
per gram<br />
1 -<br />
I<br />
u<br />
'L1 4<br />
a -:<br />
m .A<br />
4 8<br />
V 4<br />
Number<br />
per gram<br />
15<br />
25<br />
25<br />
Y1<br />
rl<br />
.+ 3<br />
x 9<br />
Number<br />
per gram<br />
13<br />
9<br />
19<br />
5<br />
6<br />
4<br />
4<br />
Benthonic<br />
Number<br />
per gram<br />
28<br />
34<br />
44<br />
16<br />
31<br />
39<br />
4<br />
Benthonic<br />
Percentage<br />
18<br />
4 5<br />
28<br />
11<br />
28<br />
27<br />
21
Subphylum SARCODINA Schmarda, 1871<br />
Class RHIZOPODEA von Siebold, 1845<br />
Subclass LOBOSIA Carpenter, 1861<br />
Order FORAMINIFERIDA Eichwald, 1830<br />
Suborder TEXTULARIINA Delage and Herouard, 18%<br />
Superfamily AMMODISCACEA Reuss, 1862<br />
Family SACCAMMINIDAE Brady, 1884<br />
Subfamily SACCAMMININAE Brady, 1884<br />
Genus SACCAMMINA M. Sars in Carpenter, 1869<br />
SACCAMMINA COMPLANATA (Franke 1912)<br />
Fig. lO(6)<br />
Descniptiun.-Test free, consisting of a single bulbous chamber,<br />
crushed in the material at hand; wall very fine-grained sand<br />
particles; aperture single, round, with short neck. Dimen-<br />
sions: breadth, approximately 0.26 mm.<br />
Remarks.-Only two specimens were found in the material;<br />
the smaller one is badly crushed. Specimens are not as<br />
smoothly finished as those described by Cushman (1946).<br />
Figured specimen BYU 1973.<br />
Supcrfamily LITUOLACEA de Blainville, 1825<br />
Family HORMOSINIDAE Haekel, 1894<br />
Subfamily HORMOSININAE Haekel, 1894<br />
FIGURE 9.-Graph of foraminifera1 abundance in ash 5<br />
R. L. BAGSHAW<br />
NUMBERS PER G R A M<br />
Genus REOPHAX Montfort, 1808<br />
(?) REOPHAX sp.<br />
Fig. lO(2)<br />
Description.-Test elongate, consisting of three uniserial cham-<br />
bers: chambers rounded in section; sutures straight, distinct;<br />
wall agglutinated with fine sand grains. Dimensions: length,<br />
approximately 0.7 mm; diameter, approximately 0.3 mm.<br />
Remarks.-Only one specimen was found in the samples. It is<br />
incomplete with only half of the third chamber present. It<br />
could possibly be a fragment of Ammobaculites, with the plan-<br />
ispiral early portion missing.<br />
Figured specimen BYU 1974<br />
Family LITUOLIDAE de Blainville, 1825<br />
Subfamily LITUOLINAE de Blainville, 1825<br />
Genus AMMOBACULITES Cushman, 1910<br />
AMMOBACULITES WENONAHAE Tappan, 1960<br />
Fig. lO(7)<br />
Description.-Test free, elongate, slightly compressed; early por-<br />
tion close coiled, with five to seven chambers in the coil and<br />
a large umbilicus; later portion uniserial with nearly parallel
sides, early uniserial portion of equal or 1;ss breadth than the<br />
coil, peripheral margin broadly rounded; chambers numerous,<br />
inflated in the coil, ranging from subrounded to low and<br />
broad in the uniserial portion; uniserial chamber increasing<br />
very little in diameter as added; sutures distinct, straight, and<br />
depressed; wall agglutinated, texture varying, aperture termi-<br />
nal rounded. Dimensions: length, 0.3-0.6 mm; diameter of<br />
coil, 0.2-0.3 mm; thickness, 0.15-0.2 mm.<br />
Remarks.-Four specimens were found, two of which are<br />
crushed. The specimens are smaller than those described by<br />
Tappan (1360). This species was originally described from the<br />
Upper Cretaceous of the North Slope of Alaska (Tappan<br />
1951).<br />
FORAMINIFERAL ABUNDANCE RELATED TO BENTONITIC ASH BEDS 41<br />
distinct, somewhat limbate, earlier sutures flush with the sur-<br />
face, oblique, later sutures progressively more depressed and<br />
more nearly at right angles to the elongate axis; wall<br />
smooth, or the earliest portion sometimes slightly roughened;<br />
aperture terminal, radiate. Dimensions: length, approximately<br />
1.7 mm; breadth, 0.2-0.24 mm.<br />
re mar&^.-Representatives of the species occur sporadically in<br />
all the ash beds, but all the recovered specimens are broken.<br />
The species is consistently present in both Maxfield's (1976)<br />
and Lessard's (1973) Tununk sections. It ranges through<br />
beds of Taylor and Navarro age in the Gulf Coastal region<br />
of the United States (Maxfield 1976, p. 112).<br />
Figured specimens BYU 2450, 2451.<br />
Figured specimen BYU 1975.<br />
Genus FRONDICULARIA DeFnnce in d'orbigny, 1826<br />
Suborder ROTALIINA Delage and Herouard, 1896<br />
Superfamily NODOSARIACEA Ehrenberg, 1838<br />
Family NODOSARIIDAE Ehrcnberg, 1838<br />
Subfamily NODOSARIINAE Ehrenberg, 1838<br />
Genus DENTALINA Risso, 1826<br />
DENTALINA BASIPLANATA Cushrnan, 1938<br />
Fig. 10(3, 4)<br />
FRONDICULARIA GOLDNSSI Reuss, 1860<br />
Fig. lo(>, 10)<br />
De~rption.-The species has a basal spine and a rounded or<br />
slightly elongate prolocu~um, the following chambers increasing<br />
very slightly in width as added, the sutures becoming<br />
progressively more curved, slightly limbate, but not rising<br />
Description.-Test very elongate, slightly tapering, usually above the flattened, broad face of the test; wall may be<br />
slightly curved; early portion showing oblique costae that in- smooth to a few fine vertical costae on each chamber, and<br />
dicate coiling, especially in the microspheric form, often not crossing the sutures; periphery distinctly truncate, even<br />
slightly compressed; chambers distinct, earlier chambers not slightly concave; apertural end usually projects slightly into a<br />
inflated, later chambers become increasingly inflated as added; very short apertural neck; at the base the chambers reach<br />
earlier chambers much more strongly overlapping; sutures well back, forming a broadly wedge-shaped base with the<br />
Interval<br />
190-195 cm<br />
185-190<br />
180-185<br />
T<br />
165-170 a<br />
150-155<br />
145-150T<br />
140-145-<br />
134-140<br />
j<br />
129-134<br />
124-129<br />
119-124<br />
48-56<br />
40-48<br />
33-40<br />
2 5 - 3 0 7<br />
18-25 4<br />
13-18<br />
5-13-<br />
0-5<br />
Total<br />
Number<br />
per gram<br />
280<br />
1836<br />
406<br />
497<br />
662<br />
646<br />
236<br />
1225<br />
1877<br />
3134<br />
997<br />
703<br />
1554<br />
114-119<br />
109-114<br />
104-109<br />
99-104<br />
94-99<br />
89-94<br />
84-89<br />
79-84<br />
71-79<br />
63-71<br />
* 591<br />
3649<br />
ii;<br />
56-63 5066<br />
1349<br />
1905<br />
967<br />
2907<br />
1934<br />
1028<br />
604<br />
905<br />
0<br />
IY 4<br />
4 Q<br />
w .4<br />
.4 LI -4 C<br />
.$ 2<br />
: S<br />
5 :<br />
Number<br />
per gram<br />
82<br />
706<br />
171<br />
279<br />
173<br />
381<br />
30<br />
405<br />
562<br />
1305<br />
379<br />
1 261<br />
400<br />
147<br />
142<br />
257<br />
257<br />
128<br />
340<br />
116<br />
615<br />
549<br />
200<br />
313<br />
409<br />
1607<br />
621<br />
757<br />
464<br />
798<br />
272<br />
483<br />
- u<br />
.Y<br />
8 8<br />
2 2<br />
3 %<br />
% %,<br />
Nlrmber<br />
per gram<br />
82<br />
298<br />
83<br />
4 3<br />
184<br />
123<br />
61<br />
194<br />
543<br />
653<br />
151<br />
154<br />
517<br />
78<br />
202<br />
99<br />
284<br />
230<br />
556<br />
242<br />
1483<br />
623<br />
820<br />
300<br />
209<br />
1328<br />
288<br />
278<br />
162<br />
399<br />
250<br />
217<br />
107 118<br />
309 231<br />
'+ - u<br />
w<br />
" 8<br />
3 x<br />
0 2<br />
Number<br />
per gram<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
TABLE 5<br />
Foraminifera1 Occurrence in Aah 5<br />
Planktonic<br />
Number<br />
per gram<br />
164<br />
1004<br />
254<br />
322<br />
357<br />
504<br />
91<br />
599<br />
1105<br />
1958<br />
530<br />
415<br />
917<br />
225<br />
344<br />
356<br />
541<br />
358<br />
896<br />
358<br />
2098<br />
1172<br />
1020<br />
613<br />
618<br />
2935<br />
849<br />
1035<br />
626<br />
1197<br />
522<br />
700<br />
225<br />
540<br />
Planktonic<br />
Percentage<br />
58<br />
55<br />
62<br />
65<br />
54<br />
78<br />
38<br />
49<br />
59<br />
62<br />
53<br />
59<br />
59<br />
55<br />
45<br />
52<br />
57<br />
4 3<br />
50<br />
60<br />
57<br />
51<br />
65<br />
61<br />
52<br />
58<br />
63<br />
54<br />
65<br />
41<br />
C C<br />
.4 .a<br />
"7<br />
'4 2<br />
j 2<br />
Number<br />
per gram<br />
82<br />
594<br />
61<br />
71<br />
123<br />
82<br />
133<br />
415<br />
409<br />
350<br />
236<br />
128<br />
401<br />
61<br />
201<br />
123<br />
164<br />
256<br />
450<br />
143<br />
1075<br />
676<br />
307<br />
215<br />
194<br />
1013<br />
220<br />
261<br />
157<br />
497<br />
803<br />
59 100<br />
2 .A<br />
w .d<br />
0 4 -4 c<br />
Number<br />
per gram<br />
19<br />
202<br />
53<br />
56<br />
145<br />
48<br />
10<br />
148<br />
2 98<br />
468<br />
155<br />
98<br />
168<br />
82<br />
102<br />
164<br />
175<br />
109<br />
350<br />
41<br />
397<br />
306<br />
99<br />
161<br />
270<br />
933<br />
191<br />
428<br />
105<br />
611<br />
221<br />
122<br />
231<br />
148<br />
UI<br />
4<br />
. c<br />
:;<br />
2 5<br />
Number<br />
per gram<br />
15<br />
36<br />
36<br />
28<br />
37<br />
12<br />
1<br />
62<br />
63<br />
355<br />
75<br />
60<br />
67<br />
38<br />
101<br />
36<br />
55<br />
114<br />
98<br />
47<br />
78<br />
216<br />
133<br />
10<br />
98<br />
182<br />
89<br />
180<br />
77<br />
601<br />
385<br />
127<br />
59<br />
115<br />
Benthonic<br />
Number<br />
per gram<br />
116<br />
832<br />
150<br />
155<br />
305<br />
142<br />
144<br />
625<br />
770<br />
1173<br />
466<br />
286<br />
636<br />
181<br />
404<br />
323<br />
394<br />
479<br />
898<br />
231<br />
1550<br />
1198<br />
539<br />
386<br />
562<br />
2128<br />
500<br />
869<br />
339<br />
1709<br />
1409<br />
350<br />
379<br />
363<br />
Benthonic<br />
Percentage<br />
4 2<br />
45<br />
38<br />
35<br />
46<br />
2 2<br />
62<br />
51<br />
41<br />
38<br />
47<br />
41<br />
41<br />
45<br />
55<br />
48<br />
4 3<br />
57<br />
50<br />
40<br />
4 3<br />
49<br />
35<br />
39<br />
48<br />
42<br />
37<br />
46<br />
35<br />
59<br />
73<br />
3 2<br />
63<br />
41
42 R. L. BAGSHAW<br />
FIGURE 10.-Foraminifera1 fauna: (1) Fmndicularia invrrra Reuss. Sidc view, X170. (BYU 1976). (2) (?) Rrophax sp. Side view, X190. (BYU 1974). (3) Dmta-<br />
lina basiplanata Cushrnan. Side view, XbO. (BYU 2451). (4) Dmtalina baripIanata Cushman. Side view, X125. (BYU 2450). (5) Fmndiculatia go~furri<br />
Reuss. Side view, X30. (BYU 2491). (6) Saccammina complanata (Franke). Side view, X18O. (BYU 1973). (7) Ammobaculiter monabae Tappan. Side<br />
view, X185. (BYU 1975). (8) Frondirulatia inverra Reuss. Sidc view, X65. (BYU 2489). (9) Fmndiculatia inverra Reuss. Side view, X65. (BYU 2490).<br />
(10) Fmndirularia gold/urri Reuss. Side view, X60. (BYU 2492). (11) Lagma rulcata (Walker & Jacob) Parker & Jones. Apertural view, X320. (BYU<br />
2493).
central portion projecting. Dimensions: length, approximately<br />
1.5 mm; breadth, approximately 1.04 mm.<br />
Remarks.-Only one specimen was found in the samples. It is<br />
broken across its breadth.<br />
Figured specimens BYU 2491, 2492.<br />
FRONDICULARIA INVERSA Reuss. 1844<br />
Fig. lO(1. 8, 9)<br />
Description.-Test elongate, elliptical, very strongly compressed;<br />
periphery rounded, base with a short, stout spine; chambers<br />
distinct, the proloculum narrow, elongate; later chambers<br />
gradually failing to reach the base, giving a narrow tapering<br />
shape to that part of the test; sutures distinct, flush with the<br />
surface to slightly indented, gently curved, usually crossed by<br />
fine discontinuous vertical costae, especially near the apertural<br />
end; aperture terminal radiate. Dimensions: length, approx-<br />
imately 0.76 mm; breadth, approximately 0.22 mm.<br />
remark^.-Only one specimen was found in the ashes; how-<br />
ever it is a complete specimen that is slightly crushed. Max-<br />
field (1976, p. 117) found that the species was limited to the<br />
Tununk Shale in all his sections except one.<br />
Figured specimens BYU 1976, 2489, 2430<br />
Genus LAGENA Walker and Jacob in Kanmacher, 1798<br />
LAGENA SULCATA (Walker and Jacob) Parker and Joncs, 1929<br />
Fig. lO(ll), fig. ll(1, 2)<br />
Description.-Test spherical to elliptical with hyaline, calcareous<br />
walls; unilocular; well-formed vertical costae widely varying<br />
in number, terminating at neck; aperture is a centrally lo-<br />
cated, simple opening at the end of a short neck. Dimen-<br />
sions: length, approximately 0.24 mm; breadth, approximately<br />
0.16 mm.<br />
Remarks.-Three complete and one broken specimen of the<br />
species were found in ash 5. Maxfield (1976) and Lessard<br />
(1973) found Lagma sulcata in all their Tununk Shale measured<br />
sections.<br />
Figured specimens BYU 2493, 2498, 1977.<br />
Supcrfamily BULIMINACEA Jones, 1875<br />
Family TURRILINIDAE Cushman, 1927<br />
Subfamily TURRILININAE Cushman, 1927<br />
Genus NEOBULIMINA Cushman and Wickenden, 1928<br />
NEOBULIMINA CANADENSIS Cushman and Wickenden. 1928<br />
Fig. 1 l(4, 5, 6)<br />
Description.-Test elongate, fusiform, greatest width near the<br />
middle, tapering slightly toward either end, about 2% times<br />
as long as wide in adult specimens; early triserial stage of<br />
twelve to eighteen chambers, the biserial adult stage of four<br />
to six chambers, each part making about one-half the mass<br />
of the test; chambers distinct, subglobular, inflated; sutures<br />
very distinct, depressed; wall calcareous, coarsely perforate;<br />
aperture in the early triserial portion oblique and comma<br />
shaped, in the adult biserial stage broader, the portion at the<br />
basal edge of the chamber broad and the elongate axis nearly<br />
at right angles to the margin of the chamber; the whole<br />
aperture in the adult at the base of a distinct depression. The<br />
microspheric form is often somewhat irregular and twisted.<br />
Dimensions: length, 0.2-0.3 mm; breadth, 0.1-0.14 mm.<br />
Remarks.-The species occurs in all the ash beds, but not in<br />
large numbers. Agreement with the figured type specimen<br />
and description is good in all respects.<br />
FORAMINIFERAL ABUNDANCE RELATED TO BENTONITIC ASH BEDS<br />
Figured specimens BYU 1979, 2437, 2440.<br />
PRAEBULIMINA PROLIXA (Cushman and Parker 1935)<br />
Fig. ll(3)<br />
Description.-Test long and narrow, about 2 1/1 times as long<br />
as broad, tapering very slightly through the whole length,<br />
triangular in section, with angles broadly rounded, often<br />
somewhat twisted on its axis toward the initial end; chambers<br />
numerous, six to seven whorls in adults, those of succcssive<br />
whorls placed directly over others particularly in the initial<br />
part, becoming less so in the later portions, adjacent<br />
series meeting in a zigzag line; sutures very slightly depressed;<br />
aperture elongate, well removed from the juncture of<br />
the third preceding chamber. Dimensions: length, 0.22-0.3<br />
mm; breadth, 0.1-0.16 mm.<br />
Remarks. -Specimens occur abundantly in all sections of the<br />
ashes, with as many as 9000 per gram sample for one interval<br />
and an average of 600 per gram sample. Agreement with the<br />
type figure and description is good.<br />
Figured specimen BYU 1978.<br />
PRAEBULIMINA VENUSAE (Nauss 1947)<br />
Fig. 1 l(7, 8)<br />
Description.-Test free, small, short, triserial throughout, rapidly<br />
flaring from a tiny early portion to an inflated later portion<br />
of greatest breadth, rounded in section; chambers triserially<br />
arranged in about four whorls, increasing quickly in<br />
size and becoming inflated; suture distinct, depressed; wall<br />
calcareous, finely perforate, with smooth finish; aperture a<br />
loop-shaped opening extending up the face of the final chamber.<br />
Dimensions: length, approximately 0.2 mm; breadth, approximately<br />
0.1 mm.<br />
Remarks.-The species occurs sporadically in all the sampled<br />
intervals. Specimens occurring in the Tununk Shale are<br />
slightly smaller than those described elsewhere.<br />
Figured specimens BYU 2386, 2389.<br />
Superfamily GLOBIGERINACEA Carpenter, Parker and Jones, 1862<br />
Family HETEROHELICIDAE Cushman, 1927<br />
Subfamily GUEMBELITRIINAE Montanaro Gallitelli, 1957<br />
Genus GUEMBELITRIA Cushman, 1933<br />
GUEMBELITRIA CRETACEA Cushman, 1933<br />
Fig. 12(1, 2, 3)<br />
Description. -Test triserial, small; chambers globular, nearly<br />
spherical, sutures much depressed; wall smooth, finely perforate;<br />
aperture large, semicircular or semielliptical at the inner<br />
margin of the last-formed chamber. Dimensions: length,<br />
0.2-0.3 mm; breadth, 0.1G0.22 mm.<br />
Remarks.-The species occurs only in ashes 1 and 2; none<br />
were found in ash 5. Maxfield (1976, p. 132) states that it<br />
appears to be a useful marker in the lower Tununk Shale.<br />
Agreement with the figured type material and description is<br />
very good.<br />
Figured specimens BYU 2550, 2552, 2553.<br />
Subfamily HETEROHELICINAE Cushman, 1927<br />
Genus HETEROHELIX Ehrenberg, 1843<br />
HETEROHELIX GLOBULOSA (Ehrenberg), 1840<br />
Fig. 12(5)<br />
Description.-Test rapidly tapering, greatest breadth toward the<br />
apertural end, initial end subacute, 1% to 2 times as long as
44 R. L. BAGSHAW<br />
FIGURE 11.-Fonminifenl fauna: (1) Lagena sulcata (Walker & Jacob) Parker & Jones. Side view, X460. (BYU 2498). (2) Lagma sulcata (Walker & Jacob)<br />
Parker & Jones. Apcrtunl view, X320. (BYU 1977). (3) Praebulimina prolixa (Cushrnan & Parker). Sidc view, X440. (BYU 1978). (4) Neobulimina<br />
canadm~i~ (Cushman & Wickenden). Sidc view, X330. (BYU 2440). (5) Neobulimina canadensis (Cushman & Wickenden). Sidc vicw, X460. (BYU<br />
1979). (6) Neobulimina canadensis (Cushman & Wickenden). Sidc view, X290. (BYU 2437). (7) Praebulimina venusae (Nauss). Side view, X360. (BYU<br />
2389). (8) Praebulimina venusae (Nauss). Sidc vicw, X350. (BYU 2386).
oad, in side view, with the chambers regularly enlarging to<br />
the greatest width at the last-formed chamber, periphery dis-<br />
tinctly indented throughout; chambers inflated throughout,<br />
increasing in size rather more rapidly toward the apertural<br />
end, nearly spherical; sutures distinct, depressed throughout;<br />
wall smooth, finely perforate, aperture broad, low, with a<br />
slightly thickened rim. Dimensions: length, 0.26-0.42 mm;<br />
breadth, 0.20-0.28 mm.<br />
Remarks-Small specimens are more abundant than large ones<br />
throughout the entire sampled intervals of all the ashes. This<br />
species shows considerable variability of position of the final<br />
chamber, presence of the initial planispiral coil, and presence<br />
or absence of surface ornamentation, but remains within the<br />
limits of figured and described types from other areas. The<br />
species has a very wide distribution (Maxfield 1976, p. 134).<br />
Figured specimen BYU 2532.<br />
Familv PLANOMALINIDAE Bolli. Locblich. and Ta~~an. 1957<br />
~cnu; GLOBIGERINELLOIDES dushman and Tcn am; 1948<br />
GLOBIGERINELLOIDES ASPERA (Ehrcnbcrg 1854)<br />
Fig. 12(4, 6)<br />
Description.-Test free, small planispiral, biumbilicate, periphery<br />
moderately lobate, six to seven chambers in the final whorl,<br />
inflated, globular, slightly overlapping; sutures distinct, de-<br />
pressed radial, wall calcareous, finely perforate, surface smooth<br />
to finely hispid; aperture a moderately high arch at the base<br />
of the final chamber, with small lip. Dimensions: diameter,<br />
approximately 0.16 mm; thickness, approximately 0.08 mm.<br />
Remarks.-Specimens occur sporadically throughout all the<br />
ashes. These specimens agree very well with the type speci-<br />
mens figured and described by Barr (1966, 1968) and by Pes-<br />
sagno (1967) and are therefore considered conspecific. The<br />
species has a reported stratigraphic range from the Upper<br />
Coniacian to Maestrichtian and a wide areal distribution<br />
(Maxfield 1976, p. 137).<br />
Figured specimens BYU 1980, 2521.<br />
Family ROTALIPORIDAE Sigal, 1958<br />
Subfamily HEDBERGELLINAE Locblich and Tappan, 1961<br />
Gcnus HEDBERGELLA Bronniman and Brown, 1958<br />
HEDBERGELLA DELRIOENSIS (Carscy 1954)<br />
Fig. 12(7, 8, 9)<br />
Description.-Test free, in a low trochospiral coil of about two<br />
volutions, early whorl flush to slightly depressed below the<br />
final whorl on the spiral side, opposite side deeply umbilicate,<br />
peripheral outline strongly lobulate; chambers much inflated,<br />
nearly spherical, increasing rapidly in size as added, with four<br />
to six chambers in the final whorl, most commonly five; su-<br />
tures distinct, straight to slightly curved, deeply constricted;<br />
wall calcareous, distinctly perforate, earlier chambers with a<br />
papillate surface, final chambers less ornamented, no in-<br />
dication of a keel or poreless margin; aperture an arch on<br />
the umbilical side, interiomarginal and extraumbilical-umbili-<br />
cal. Dimensions: diameter, 0.3-0.68 mm; thickness, 0.2-0.4<br />
mm.<br />
Remarks.-The specimens recovered vary a great deal in size;<br />
however, most are small. Those in ash 5 are flatter. Speci-<br />
mens were found in all five ashes.<br />
Figured specimens BYU 1981, 1982, 1983.<br />
FORAMINIFERAL ABUNDANCE RELATED TO BENTONITTC ASH BEDS<br />
Genus CLAVIHEDBERGELLA Banner and Blow, 1959<br />
CLAVIHEDBERGELLA SIMPLEX (Morrow 1934)<br />
Fig. 12(10, 11)<br />
Descriptzon.-Test free, of medium size, trochospirally coiled,<br />
subglobular to elongate chambers forming about two to two<br />
and one-half whorls, the early whorl with about five globular<br />
chambers, the final whorl with four to six chambers, the last<br />
two or three radially elongate to subclavate; sutures distinct,<br />
depressed; wall calcareous, finely perforate, surface finely spi-<br />
nose; aperture an interiomarginal arch extending from the<br />
periphery to the umbilicus, with a narrow bordering lip. Di-<br />
mensions: diameter, 0.2-0.5 mm; thickness, 0.1-0.24 mm.<br />
Remarks. -Specimens occur sporadically throughout all the<br />
sampled intervals. The immature portions of the specimens<br />
are very close to the form of Hedbergella and would certainly<br />
be placed under that genus.<br />
Figured specimens BYU 1984, 1985.<br />
Supcrfamily ORBITOIDACEA Schwagcr, 1876<br />
Family CIBICIDAE Cushman, 1927<br />
Subfamily PLANULININAE Bcrmudcz, 1952<br />
Gcnus PLANULINA d90rbigny, 1826<br />
PLANULINA AUSTINANA Cushman, 1938<br />
Fig. 13(2, 5)<br />
Description.-Test very much compressed, partially evolute on<br />
both sides, particularly the dorsal side, which is very slightly<br />
umbonate; ventral side slightly umbilicate; periphery sub-<br />
acute, lobate; chambers distinct, somewhat inflated, of uni-<br />
form shape, increasing very gradually in size as added, six to<br />
eight in the adult whorl; sutures distinct, only slightly de-<br />
pressed; wall smooth, finely perforate; aperture a low opening<br />
at the base of the last-formed chamber at the periphery and<br />
extending over along the dorsal side. Dimensions: diameter,<br />
0.18-0.38 mm; thickness, 0.05-0.1 mm.<br />
Remarks,-Specimens were recovered from all sampled inter-<br />
vals; however, fewer examples were recovered from ash 2.<br />
Most of the specimens are juvenile forms. Maxfield (1976, p.<br />
144) states that the species is a useful marker for the Tu-<br />
nunk Shale. Specimens from the Tununk Shale differ from<br />
those of the type description in that they have fewer cham-<br />
bers in the adult whorl and are somewhat smaller. P. austi-<br />
nana differs from P. kansmsis in that the periphery of P.<br />
austinana is more acute and there is less calcareous deposit in<br />
the central area, particularly on the ventral side. This species<br />
has been reported from the Austin Chalk of Texas (Cushman<br />
1938).<br />
Figured specimens BYU 1986, 1987.<br />
PLANULINA KANSASENSIS Morrow, 1934<br />
Fig. 13(6, 9)<br />
Description.-Test much compressed, dorsal and ventral sides<br />
nearly flat, dorsal side evolute, ventral side partially involute;<br />
periphery rounded, chambers numerous, eight to ten in final<br />
whorl; sutures distinct between the later chambers, slightly<br />
depressed, curved outward and backward; central area on<br />
both sides covered by a calcareous deposit varying in thick-<br />
ness from a film to a thick rounded plug, which may be<br />
transparent showing the covered chamber; wall smooth per-<br />
forate; aperture obscure, extending along the base of the last<br />
chamber onto the ventral side. Dimensions: diameter, 0.3-<br />
0.36 mm; thickness, 0.1-0.12 mm.
46 R. L. BAGSHAW<br />
. . , -. .$,'<br />
* ~2 ' " . .<br />
, ,<br />
-,-*"-zrfl;A: y<br />
$6"".<br />
. . ,*, ' \<br />
FORAMINIFERAL ABUNDANCE REWTED TO BENTONITIC ASH BEDS 47<br />
EIGURE 13.-Ponminifenl fauna: (1) GusidcIIa teguclata (Reuss). Side view, X200. (BYU 1988). (2) Planulina austinana Cushrnan. Vmtd view, X180. (BYU<br />
1986). (3) Cassidella tegulata (Reuss). Side view, X220. (BYU 1989). (4) Anomalina tmnes~msis W. Berry. Side view, X125. (BYU 2393). (5) Planulina<br />
aus~inunu Cushman. Dorsal view, X210. (BYU 1987). (6) Planulina kansasmris Morrow. Ventral view, X15O. (BYU 2414). (7) Anomalina tmnersmis<br />
W. Bcrry. Side view, X135. (BYU 2395). (8) Gavelinella nelsoni (W. Berry). Dorsal view, X180. (BYU 1991). (9) Planulina kansasmsir Morrow. Dorsal<br />
view, X135. (BYU 2416). (10) Anomalina tmnersmsis W. Berry. Apertural view, X435. (BYU 1990). (11) Gavelinella nelson; (W. Berry). Ventral view,<br />
X12O. (BYU 2399). (12) Gavelinella nelroni (W. Berry) Ventral view, X135. (BYU 2397).
48 R L BAGSHAW<br />
Remarks.-Specimens identified as P. Ransasens~s Morrow are<br />
very rare In the sampled sections, and may actually be vari-<br />
ants of P. awtznana. As originally defined this species differs<br />
from P. aus/mana In having a more rounded periphery, more<br />
calcareous deposits in the central portion, and a more distinct<br />
aperture with a slight flap extending into the ventral area.<br />
The species was originally described from the Fort Hays<br />
Member of the Niobrara Formatlon of Kansas (Morrow<br />
1934).<br />
Figured specimens BYU 2414, 2416.<br />
Superfamrly CASSIDULINACEA d'orbrgny, 1839<br />
Family CAUCASINIDAE N. K Bykova, 1959<br />
Subfamrly FURSENKOININAE Loeblrch and Tappan, 1961<br />
Genus CASSIDELLA Hoflcer, 1951<br />
CASSIDELLA TEGULATA (Reuss), 1951<br />
Frg 13(1, 3)<br />
Vzrgukna tegulata Reuss 1845, p. 40, pl 13, fig. 81 ; Cushman<br />
1937, p. 4-5, pl. 1, figs. 8-12; Bolin 1952, p. 46-47, pl. 3,<br />
fig. 8.<br />
Bolzvzna tegulata Reuss 1851, p. 29, pl. 4, fig. 12; Morrow<br />
1934, p. 196, pl. 30, fig. 21.<br />
Loxostomum tegulatum (Reuss), Cushman 1931, p. 51, pl. 8,<br />
fig. 8; <strong>Young</strong> 1951, p. 64, pl. 14, fig. 13, Green 1959,<br />
pl. 63, pl. 3, fig. 8; Lessard 1973, p. 25, pl. 2, fig. 8.<br />
Loxostoma tegulatum (Reuss), Cushman 1937, p. 168-69, pl.<br />
20, figs. 17, 18; Loetterle 1937, p. 40, pl. 6, fig. 3.<br />
Cussidella tegulata (Reuss), Hofker 1951, p. 265, fig. 175;<br />
Loeblich & Tappan 1964, p. C732-33, figs. 600-5-7.<br />
Virgulina sp. #I Bolin 1952, p. 47, pl. 3, figs. 9a,b.<br />
Description.-Test free, narrow, elongate, gently tapering, pe-<br />
riphery rounded; triserial in earliest chambers, becoming bise-<br />
rial in early part, biserial portion making up most of test;<br />
later chambers show a slight tendency toward uniserial devel-<br />
opment; many specimens are slightly twisted around long<br />
axis; chambers are numerous, very lightly inflated; sutures<br />
distinct, slightly depressed, tending to be horizontal, wall cal-<br />
careous, finely perforate, granular in structure, surface<br />
smooth; aperture elongate, narrow, extending up face from<br />
base of final chamber. Dimensions: length, 0.24-048 mm,<br />
breadth, 0.1-0.14 mm.<br />
Remarks.-The species occurs sporadically throughout all the<br />
sampled intervals. A few of the specimens have been partially<br />
altered to hematite. The taxonomic position of the species is<br />
uncertain because of conflicting statements and some con-<br />
fusion in the literature. Kent (1967, p. 1450) discussed the<br />
confusion about its position. The Tununk Shale specimens<br />
fit Kent's description and figured specimen very well (1967).<br />
Specles which are similar have been descr~bed from the Allen<br />
Valley Shale of Utah, the Tununk Shale of Utah, the Fron-<br />
tier Formatlon of southern Montana, and the Taylor, Austln,<br />
and Eagle Ford groups of Texas. It has also been found in<br />
the Fort Hays Member of the Niobrara Format~on in<br />
Kansas, Nebraska, South Dakota, and Colorado. The species<br />
was originally described from the Turonlan of Bohem~a<br />
(Reuss 1845).<br />
Figured specimens BYU 1988, 1989.<br />
Fam~ly ANOMAUNIDAE Cushman, 1927<br />
Subfamily ANOMALININAE Cushman, 1927<br />
Genus ANOMALINA d'orbrgny, 1826<br />
ANOMALINA TENNESSEENSIS W Berry, 1929<br />
Rg 13(4, 7, 10)<br />
Descnptzon.-Test small, planisplral, sl~ghtly compressed later-<br />
ally, composed of elght to nlne chambers in the last whorl,<br />
slightly evolute on the dorsal side, only the last whorl visible<br />
on the ventral side, Immature forms completely involute; su-<br />
tures slightly depressed, more or less distinct; aperture a nar-<br />
row curved slit at the base of the final chamber. Dimensions,<br />
diameter, 0.14-0.3 mm, thickness, 0.1-0.15 mm.<br />
Remarks.-Very few specimens were found in the samples, and<br />
most of these are Immature. The species has been reported<br />
previously from the Marlbrook Marl of Arkansas and from<br />
the Selma Chalk of Mississippi. This specles was orig~nally<br />
described from the Coon Creek Tongue of the Ripley Forma-<br />
tion of Tennessee (Berry and Kelley 1929).<br />
Figured specimens BYU 1330, 2393, 2395.<br />
Genus GAVELINELLA Brotzen, 1942<br />
GAVEUNELLA NELSON1 (W Berry, 1929)<br />
Frg 13(8, 11, 12)<br />
Desrn)tion.-Test ~nflated, dorsal side slightly convex, ventral<br />
side deeply umbilicate; periphery broadly rounded, lobate,<br />
chambers numerous, seven to eight In the last-formed coil,<br />
inflated, gradually increas~ng in size; sutures distinct, de-<br />
pressed; wall punctate; umbilical cavity usually filled with<br />
shell material; aperture an arched slit with a slight lip above<br />
it as the base of the last chamber. Dimensions: diameter,<br />
0.32-0.4 mm; thickness, 0.1-0.15 mm.<br />
Remarks.-The species occurs In all of the sampled intervals in<br />
fairly large numbers. The specles has been reported as ranging<br />
from the highest beds of Navarro age down through the<br />
upper beds of Taylor age In deposits of the Gulf Coastal region.<br />
Figured specimens BYU 1991, 2397, 2333.<br />
REFERENCES CITED<br />
Barr, F T, 1966, Upper Cretaceous fonmrnrfera from the Ballydeenlca Chalk,<br />
County Kerry, Ireland Palaeontol., v 9, p 492-510, pl 77-79<br />
-, 1968, Upper Cretaceous stratrgnphy of Jabal a1 Akhdar, northern<br />
Cyrena~ca, In Barr, F T (ed ), <strong>Geology</strong> and archaeology of northern<br />
Cyrena~ca, Lbya Petrol Expl Soc Lbya, Tnpolr, p. 131-37, pl 1-3<br />
Berry, W, and Kelley, L, 1929, The fonmlnlfera of the Rrpley Format~on<br />
on Coon Creek, Tennessee. US. Natl. Mus. Proc, v 76, art 19, 20 p,<br />
3 PI<br />
Bolin, E. J , 1952, Mrcrofossrls of the N~obran Format~on of southeast South<br />
Dakota South Dakota Geol SUN, Rept Invest 70, p 1-74, pl 1-5<br />
Cushman, J A, 1931, Harttgennella and other lnterestrng foramlnrfen from<br />
the Upper Cretaceous of Texas Cushman Lab Foram Res, Contr , v<br />
7, pt 4, p 83-90, pl 11<br />
-__, 1931, A prelrmrnary report of the foramrn~fera of Tmnessee Tmnessee<br />
DIV. Geol Bull , p 1-112, pl 1-13<br />
-, 1937, A monograph of the subfamily V~rgulrnrnae of the foramrnrferal<br />
famrly Bulrmrnrdae Cushman Lab Foram Res, Spec Pub 9, 228<br />
P., 24 PI<br />
-, 1946, Upper Cretaceous fonm~n~fera of the Gulf Coastal regron of<br />
the Unrted States and adjacent areas US Geol SUN Prof Paper 206,<br />
p 1-241, pl 1-66
Cushmafi, J A, and Parker, F. L, 1935, Some American Cretaceous bull-<br />
mlnas Cushman Iab Fonm Res., Contr., v. 11, pt. 4, p. 96-101.<br />
Ehrenberg, C G, 1854, Mlkrogeologle Leopold Voss, Le~pzrg, p 374, pl 1-<br />
40<br />
Ercher, D L, and Worstell, Paula, 1970, Cenomanlan and Turonlan fora-<br />
mrn~fen from the Great Plarns, United States Mrcropaleont , v 16, p<br />
269-324, pl 1-13<br />
Flnger, Kenneth L, 1976, Forarnrnlfera from an actlve volcano In the Antarc-<br />
tic Geol Soc Amer Abstr., v 8, no 6, p 865<br />
Fnnke, Adolf, 1912, Dre Forarnlnlferen der Kre~deformat~on des Munsterchen<br />
Beckens Ver Preuss Rhrneland Westfalens, Vnh , v 69, p 255-85<br />
Gllberr, G K, 1877, Report on the geology of the Henry Mountalns<br />
(Utah) US Geog and Geol Surv Rocky Mtn Reg~on, 160 p<br />
Green P R, 1959, Mlcrofauna of the Allen Valley Shale, Central Utah Master's<br />
them, Unlv of Utah, 82 p, 4 pl<br />
Grernet, G 0 G , 1969, Recent benthonrc foramrnrfera: Envrronrnental facton<br />
controllrng thelr drstnbutron Nature, v 223, p 168-70<br />
Hofket, J, 1951, The forarnlnlfera of the Slboga Expedltron Part 3-Dentata<br />
E J Bnll, Lerden, 513 p , 348 fig<br />
Hunt, C B, Aventt, Paul, and M~llet, R L, 1953, <strong>Geology</strong> and geography<br />
of the Henry Mountalns reglon, Utah US Geol Surv, Prof Paper<br />
228, 234 p<br />
Kent, H. C., 1967, M~crofosmls from the N~obrara Forrnat~on (Cretaceous)<br />
and equrvalent strata In northern and western Colorado Jour Paleont ,<br />
v 41, p 1433-56, pl 183-84<br />
Lessatd, R H., 1973, Micropaleontology and paleoccology of the Tununk<br />
Member of the Mancos Shale Utah Geol and Mrn Surv, Spec Stud<br />
45, 28 p, 2 pl<br />
Loebl~ch, A R, Jt, and Tappan, Helen, 1964, Treatise on Invertebrate paleontology,<br />
pt. C Protrsta 2, Geol Soc Arner, v l & 2, 900 p<br />
Locttetle, G J, 1937, The m~cropaleontology of the Nrobrara Formatlon in<br />
Kansas, Nebraska, and South Dakora Nebraska Geol Surv., Bull 12,<br />
69p, 11 pl<br />
FORAMINIFERAL ABUNDANCE RELATED TO BENTONITIC ASH BEDS<br />
Maxfield, E. B., 1976, Foramln~fera from the Mancos Shale of east ccntral<br />
Utah. Bngham <strong>Young</strong> Unlv. Geol. St., v 23, pt. 3, p. 67-162, 16 pl<br />
Mello, J F, 1969, Foraminrfera and arat~graphy of the upper part of the<br />
P~erre Shale and lower part of the Fox Hrlls Sandstone (Cretaceous),<br />
north central South Dakota US Geol Surv , Prof Paper 611, 121 p.,<br />
11 pl<br />
Mrller, H W, 1968, Invertebrate fauna and envltonment of dcposrtron of<br />
the Nrobrara Formatlon (Cretaceous) of Kansas. Fort Hays Studles, v<br />
8, p 1-30<br />
Morrow, A L, 1934, Forarnln~fera and ostracoda from the Upper Cretaceous<br />
of Kansas Jour Paleont, v 8, p 186-205, pl 29-31<br />
Pessagno, E A, Jr, 1967, Upper Cretaceous plankton~c foclrnrn~fera from the<br />
western Gulf Coastal plaln Palaeontographica Amet~cana, v 5, no 37,<br />
p. 249-440, pl 48-100<br />
Reeslde, J B., Jr, 1957, Paleoecology of the Cretaceous seas of the western<br />
Intenor in Treatrse on rnanne ecology and paleoccology, Geol Soc<br />
Amer Mem. 67, v 2, p 505-42<br />
Reuss, A. E, 1845, Die Versternerungen der Bohmrschen Krerdefotmatlon E<br />
Schwelzerbart, Stuttgatt, Abh. 1, p. 1-58<br />
, 1851, Die Foramlnrfeten and Entomosrraceen des Kre~demergels von<br />
Lernberg Ha~dlnger's Naturwrss Abhandl , v 4, p 17-52, pl 2-6<br />
Tappan, Helen, 1951, Northern Alaska Index forarnlnrfen Cushman Lab Foram<br />
Res, Contr, v 2, pt. 1, p 1-8, pl I<br />
, 1960, Cretaceous biostrat~graphy of northern Alaska. Amet Assoc.<br />
Petrol Geol Bull, v 44, p 273-97, pl 1, 2<br />
Wllcox, R. E , 1959, Some effects of Recent volcanrc ash falls w~th espcc~al<br />
reference to Alaska US Geol Surv. Bull 1028-N, 476 p<br />
<strong>Young</strong>, Kelth, 1951, Forarn~nlfera and strat~graphy of the Ftontrer Forrnatlon<br />
(Upper Cretaceous) of southern Montana Jour Paleont, v. 25, p 35-<br />
68, pl 11-14
Paleoecology of the Lower Carmel Formation of the<br />
San Rafael Swell, Emery County, Utah*<br />
ABsm~c~.-The lower Carmel Formation in the western San Rafael Swell is<br />
a cyclic sequence deposited on the eastern shelf of the Rocky Mountain geosyncline<br />
during Bajocian-Callovian rime. The studied section comprises approximately<br />
one-third of the total Carmel Formation and is divided into two<br />
main sequencm: (1) a lower member dominated by marine carbonate and<br />
clastic sediments, and (2) an upper member dominated by evaporitic siltstone<br />
and dolostone. Lithologies of the Carmel Formation in this area are atypical<br />
of the formation-most units in the study am are dolomitic, as oppoxd to<br />
calcareous units elsewhere.<br />
Paleoenvironments during early Carmel time are tidal flat and barrier lagoon.<br />
Evidence for the presence of the barrier lagoon environment and documentation<br />
of the highly saline conditions in the study area are presented in<br />
this paper. Units which show a cyclic transgressive-regressive marine sequence<br />
occur in portions of both environments.<br />
Transgressive phases are represented in the lower portion of the section<br />
by green shales and carhonates and in the upper portion of the section by<br />
dolostone. Regressive sequences are represented in the lower portion of the<br />
section by calcareous siltstone and in the upper portion of the section by<br />
gypsiferous siltstone.<br />
INTRODUCTION<br />
The Jurassic Carmel Formation in the San Rafael Swell in<br />
east central Utah is a cvclic series of sandstone. siltstonc. carbonate<br />
rocks, and gyps;m. These rocks provide evidence for<br />
higher-than.norma1 salinity conditions which are explained by<br />
the presence of lagoons and evaporating pans isolated from<br />
the sea by barrier bars. The formation is exceptionally well<br />
exposed in the study area along Interstate 70 on the west<br />
flank of the San Rafael Swell (fig. 1). The measured section<br />
is approximately one-third of the Carmel Formation in the<br />
area, although one 650-foot-thick section (Baker et al. 1936,<br />
p. 45) was measured in a nearby area of high salt flowage<br />
(fig. 2).<br />
The area chosen for this study represents a near-shore<br />
marine transgressive-regressive series between dominantly<br />
continental sediments to the southeast and offshore marine<br />
sediments (Arapien Shale and Twin Creek Formation) to the<br />
northwest (figs. 3 and 4). The formation and equivalent<br />
units are widely exposed in central and eastern Utah, and as<br />
far south as northwestern Arizona. Carmel beds were deposited<br />
on the eastern shelf of the Rocky Mountain geosyncline<br />
during Bajocian-Callovian times. Marine fossils found within<br />
the formation corrcspond in agc and spccics to fossils found<br />
in the lower Sundance Formation of Montana and Wyoming.<br />
LAWRENCE H. BAGSHAW<br />
BMG, Inc., Denver, Colorado<br />
Acknowldgments<br />
The author gratefully acknowledges the time and help<br />
given by Dr. J. K. Rigby, thesis committee chairman, in the<br />
completion of this study. Also apprcciatcd is the help of Dr.<br />
W. K. Hamblin and Dr. H. J. Bissell who gave constructive<br />
criticism and helpful suggestions as they reviewed this study.<br />
The help of my brothers, David and Robert, as field assistants<br />
for a portion of this project is gratefully acknowledged.<br />
Ronald Lowrey, Larry Smith, and Robert Stanton helped<br />
with transportation costs and some of the early field work. FIGURE I.-Index map<br />
Allen Petersen and the above persons also provided helpful<br />
suggestions during preparation of this paper.<br />
Considerable financial support for this project came from<br />
summer work and from assistantships provided by the De-<br />
partment of <strong>Geology</strong>, <strong>Brigham</strong> <strong>Young</strong> <strong>University</strong>.<br />
Location<br />
The study area is located on the western slope of the San<br />
Rafael Swell, Utah, in secs. 3 and 4, T. 23 S, R. 9 E (fig. 1).<br />
A detailed stratigraphic section was measured in excellent exposures<br />
provided by roadcuts along Interstate 70 immediately<br />
west of Justensen Flats and east of the Eagle Canyon scenic<br />
overlook and the Copper Globe Road turnoff. The Copper<br />
Globe Road turnoff was chosen as the top of the measured<br />
section.<br />
This roadcut is readily accessible by means of Interstate<br />
70, 45 miles west from Green River, Utah, or 62 miles east<br />
from Salina, Utah.<br />
Methods of Study<br />
Field Methrds.-A section of the lower part of the Carmel<br />
Formation 37 m thick was measured with a steel tape and<br />
described in detail from exposures in roadcuts. The sub-<br />
dividing of the section into 35 units was based primarily on<br />
lithologic changc.<br />
Thickness, lithology, composition, grain size, color, bed-<br />
ding, fossils, and sedimentary structures were noted for each<br />
unit. Paleocurrent directions and trends were determined<br />
'A thws pmrntcd ro rhe Dcpartmcnr of Gmlogy, Bnghsrn <strong>Young</strong> Untveniry, tn prtbl fulfillment of rhc rcqubrcrncnts for the dcgrcc Mmcr of Sc~cnce, Dcccrnber 1976 J. Kcith R$sby. rhrsir chtttmm.<br />
51
52 L. H. BAGSHAW<br />
with a Brunton compass at each bed where measurable sedi-<br />
mentary structures were observed. Since the beds in the<br />
study area dip less than lo0, the azimuths on the sedimen-<br />
tary structures, for all practical purposes, are the original<br />
trends.<br />
Laboratory Methods. -Thin sections were made from samples<br />
of each major lithology and were examined under a stereo-<br />
microscope for microsedimentary structures and rnicrofauna.<br />
They were then stained for dolomite and calcite determina-<br />
tion using Alizarin Red S (Sabins 1962, p. 1184) and HCI-<br />
K3Fe(CN)6 (Friedman 1959, p. 95). Unconsolidated samples<br />
were disaggregated in a wetting solution (Quaternary 0) and<br />
washed through a 200-mesh screen, and the residue was ex-<br />
amined under a stereomicroscope for microfossils and clastic<br />
grain characteristics.<br />
Previous Work<br />
The Carmel Formation was originally noted by Powell<br />
(1875) as a unit above the Vermillion Cliffs, but these rocks<br />
were first described by Gilbert (1875). The name "Carmel<br />
Formation" was proposed for this unit in 1926 at a joint<br />
conference which involved H. E. Gregory, R. C. Moore, and<br />
J. B. Reeside (Wilmarth 1938, p. 351) because the section<br />
FIGURE 2.-Stratigraphic section with studied interval<br />
described by Gilbert is near Mount Carmel, Utah. Many<br />
workers have done reconnaissance-type geology and measured<br />
sections of the Carmel Formation. Amone those who have<br />
(I<br />
contributed significantly to our present understanding are<br />
Baker, Dane, and Reeside (1936); Gilluly and Reeside<br />
(1928); Gregory (1931), and Gregory and Moore (1938).<br />
Many other unpublished sections and some generalized Jurassic<br />
sections, which include descriptions of the formation,<br />
have also been measured. ~urassic- wind directions for the<br />
Navajo Formation were determined by Poole (1962). Hinman<br />
(1957) studied the Carmel-Twin Creek facies in the Uinta<br />
Mountains of Utah.<br />
Several stratigraphic sections were measured, and a generalized<br />
regional interpretation of the paleoecology of the Carme1<br />
Formation on the east flank of the San Rafael Swell was<br />
undertaken by Dover (1969) as a thesis project at Utah State<br />
<strong>University</strong>. He made no attempt to document or explain the<br />
highly saline conditions indicated in the study area covered<br />
by this paper.<br />
Ralph W. Imlay (1952) worked out a generalized timestratigraphic<br />
subdivision of the Carmel Formation and the<br />
partially equivalent Twin Creek Formation after studying<br />
stratigraphic sections in the Uinta and Wasatch mountains.<br />
The Carmel Formation has been determined to be of Bajocian-Callovian<br />
age (Baker et al. 1936, Imlay 1957). Some<br />
supportive radiometric dating was obtained b; ~arvin et al.<br />
(1965).<br />
Regional correlations for the Rocky Mountain geosyncline<br />
have been summarized by Peterson (1972).<br />
Hunt et al. (1953) summarized the fossils found in the<br />
formation in the Henry Mountain area, and R. W. Imlay<br />
listed and described Jurassic bivalves, including those of the<br />
Carmel Formation (1964). N. F. Soh1 published a description<br />
of Jurassic gastropods, including some from the Carmel Formation<br />
(1965).<br />
Geologic Setting<br />
The San Rafael Swell is a large, breached, doubly plung-<br />
ing anticline which was uplifted during the Laramide event<br />
(Hintze 1973, p. 76). It is markedly assymetrical, with dips<br />
that average 3" to 6" and only exceptionally reach lo0, on<br />
the west flank, but with dips in excess of 30" on the east<br />
limb.<br />
The study area is on the western limb of the San Rafael<br />
Swell, near the axis of the Jurassic Rocky Mountain geosyn-<br />
cline. The Uncornpahgre Uplift, and the intermediate eastern<br />
and southeastern shore area probably supplied most of the<br />
terrigenous sediments to the area, but some were probably<br />
also derived from the salt structures of the Paradox Basin<br />
(Shoemaker et al. 1958, p. 51).<br />
The presence of pyrite in some cracks and vugs is prob-<br />
ably due to Laramide heating of the sediments and to the in-<br />
trusion of Oligocene dike ;warms to the west. Authigenic<br />
pyrite present is almost totally altered to limonite.<br />
Stratigraphically, the Carmel Formation sharply overlies<br />
the Navajo Sandstone throughout most of its extent (fig.<br />
5[1, 23). Wright and Dickey (1963) described two tongues<br />
of the Carmel Formation enclosed by Navajo Sandstone be-<br />
low the main part of the formation. One of these tongues is<br />
exposed at Moab, Utah, east of the San Rafael Swell, and the<br />
other is near Glen Canyon to the southeast. Hunt et al.<br />
(1953, p. 70) characterized the Navajo-Carmel contact as<br />
hummocky, but with relief less than 1 foot in 100 feet.<br />
Wright and Dickey (1963, p. 65) noted that cross-beds in<br />
the Navajo Formation are smoothly truncated by the Carmel
Formation. They inferred that the process of planing Navajo<br />
sediments may have involved transport of sand from the<br />
Navajo Formation for up to 110 km.<br />
LITHOLQGIES<br />
Sandstone<br />
Sandstone is a minor constituent of the measured section,<br />
but two types rio occur. Light yellow-brown sandstone<br />
occurs at the base of the formation. and medium brown<br />
sandstone occurs in thin units higher stratigraphically (fig.<br />
5[33).<br />
Ltght ye//~u-br sundstone<br />
hght yellow-brown sandstone occurs in unit 1 of the<br />
measured sectton The untt 1s 5 cm thtck and 1s apparently<br />
reworked Navajo Sandstone, composed predomtnantly of medium-grained,<br />
rounded, detrltal quartz grains wtth some minor<br />
silt- and clay-stzed material Symmetrtcal r~pplc marks,<br />
carbonate cement, and vertically Increasing limontte statntng<br />
are present in the unit The sandstone unit indicates the first<br />
incursion of the 5m onto the cross-bedded Navajo Sandstone<br />
which underlres the Carmel unit<br />
Medium brm sandstone.<br />
Medium brown sandstone occurs as rippled lenses 1 to 17<br />
cm thick, in units 2, 3, 5, 9, 16, and 17 of the secrion.<br />
Grains are characteristically very fine-grained-sand- to silt-size.<br />
Composition of these lenses is rounded quartz grains with<br />
some calcareous or dolomitic cement (fig. 6b).<br />
Typically, this type of sandstone is micro-cross-laminated<br />
and occurs interbedded within shales. Sedimentary structures<br />
in the lenses and surrounding sediments and marine fossils in<br />
enclosing sediments indicate an offshore microbar environ-<br />
men t.<br />
Siltstone<br />
Siltstone makes up a large part of the noncalcarcous clas-<br />
tic rocks in the measured section. Two main types are pres-<br />
FICUR~ 3 -Gencral~zed eabt-west Carmel time cross wttton through central litah<br />
PALEOECOLOGY OF THE LOWER CARMEL FORMATION 53<br />
ent: (1) red siltstone, and (2) gypsifero~is or dolomitic silt-<br />
stone.<br />
Red siltstone<br />
Red siltstone occurs in units 18, 21, and 22 (fig 5f41).<br />
Thickness of these units varies from 92 to 164 cm. IJnit 18<br />
is a medium brown, and units 21 and 22 are red. Coloration<br />
is due to hematite.<br />
These siltstones are dense with clay matrix but contain<br />
little or no cement. Some soft sediment deformation is pre-<br />
served within this lithology. The red or brown color of the<br />
units suggest intermittent wetting and exposure, such as<br />
might occur on a tide-affected beach or lagoon.<br />
FIC~URI 4 -Palcogeogrspll~c rrrrrng of the study arm (moddied from Stanley<br />
ct dl 1971)
54 L. H. BAGSHAW<br />
FIGUM >.-Field views. (1) Contact of Carmd Formation and Navajo Formation (arrow). (2) Closeup of above contact showing the planed-off Navajo Forma-<br />
tion with units l (arrow), 2, and 3 of the Carmd Formation. (3) fine-grained sandstone lens in unit 9, showing micro-crosslamination. (4) Siltstone of<br />
unit 18, showing rapid thickening westward (right side of photo). (5) Siltstonc of unit 27, showing abundant gypsum pillows. (6) Dolostone of unit<br />
32, showing lithographic partings on the cliff face.
Gypsifemas and dolomitic siltstone<br />
Evaporitic siltstone occurs in units 26, 27, 33, 34 and 35<br />
(fig. a). Colors of these siltstone units range from medium<br />
grey (unit 26) to light red (unit 33) and light yellow-green<br />
(units 27, 33, and 35). Grain size in these units varies from<br />
fine-sand- to silt-size. Grains are predominantly flakes of gypsum<br />
and clay with some rounded detrital quartz and dolomite<br />
present (fig. 5151). These siltstones are massive but<br />
poorly indurated, owing to a lack of a cementing agent. Sorting<br />
is fair to good, with good sorting limited to unit 26.<br />
Sedimentary structures are not preserved in these siltstone<br />
units. ~ni; 34 is light red and limonite stained, suggesting<br />
some oxidation since deposition. All these evaporitic siltstone<br />
units indicate warm, hypersaline conditions such as might be<br />
anticipated in an evaporating seaway. Such an environment<br />
might best be found on an extremely low-sloping beach or<br />
in a barrier lagoon. -<br />
Shale<br />
Shale is found throughout the measured section but is<br />
most abundant in the lower third. Green, dark grey, and red<br />
shales are present.<br />
Green shale<br />
Green shale is the dominant clastic lithology in the<br />
lower third of the measured section. Units 2, 3, 5, 9, 11, and<br />
13 are all or predominantly green shale. Thickness of these<br />
PALEOECOLOGY OF THE LOWER CARMEL FORMATION 5 5<br />
units varies from 13 to 50 cm, with an approximate average<br />
thickness of 30 cm. Glauconite apparently colors these shales.<br />
Typically, most of the beds are made up of numerous, small<br />
(2 mm amplitude), silty oscillation ripple marks and have<br />
clay fillings in the ripple troughs and clay partings between<br />
ripple sets. Fossils, other than trace fossils, are lacking. The<br />
ichnofossil Arenicolites occurs in unit 13, and Opbiomotpba is<br />
found in most shale units.<br />
Grey shale<br />
Units 14, 16, and 17 are grey shales. Thickness of these<br />
units ranges from 59 to 112 cm. Bivalves are present in most<br />
grey shales, but poor preservation makes most of them even<br />
generically unidentifiable. Grey shale of the formation is typi-<br />
cally bioturbated, and most units contain some interbedded<br />
limestone or fine-grained sandstone lenses. Preservation of<br />
fossils and ripple marks is fair within limestone lenses.<br />
Red shale<br />
Unit 14 has a 20-cm-thick basal portion which is red<br />
shale. It is particularly fossiliferous and shows excellent pres-<br />
ervation. Most of the identifiable fossils collected in the mea-<br />
sured section came from the red shale of unit 14.<br />
Carbonate Rocks<br />
Carbonate rocks make up approximately half of the mea-<br />
sured section (fig. 7) and are extremely important in paleoe-<br />
FIGURE 6.-Photomicrographs. (a) Bioclasric dolomite of unit 4 (X5). (b) Cross-section of a fine-grained sandstone lens from unit 9 (X5). (c) Dolomitized<br />
ocxalcarenite with gypsum stringers of unit 29 (XS). (d) Gypsum pillows of unit 27 (XS).
56 L. H. BAGSHAW<br />
cological interpretation. Both calcareous and dolomitic carbo-<br />
nate rocks are present within the section. Some units were<br />
apparently secondarily dolomitized (as evidenced by dolomite<br />
concentration along stylolites and bedding planes), but most<br />
are apparently 'primary' (in the sense of evaporicic associ-<br />
ations). In this paper, the terms dolarmtite and dololutite are<br />
limited to those rocks which the author feels reasonably con-<br />
fident are predominantly original (early diagenetic) rather<br />
than secondary dolostone. Most carbonate rocks and some of<br />
the clastic rocks contain some secondary dolomite as cement<br />
and/or as detrital grains. Three major carbonate lithologies<br />
occur: (1) calcarenite, (2) dololutite, and (3) dolarenite.<br />
Calcarenite<br />
Calcarenite occurs throughout the measured section. Typ-<br />
ically, it occurs as very light grey to light grey or light green<br />
bioclastic lenses within shale units. Units 1, 12, 13, 14, and<br />
15 are or contain biocalcarenites composed mostly of bivalve<br />
fragments. Unit 12 contains oolites and is increasingly oolitic<br />
toward the top. Units 11, 13, and 14 occur as lenses within<br />
shales, whereas units 12 and 15 are ledge-forming, massive<br />
units. Most bivalves within units 11 through 15 are preserved<br />
as casts or as bioclasts.<br />
Dololutite<br />
Dololutite occurs in the upper portion of the measured<br />
section in units 7, 30, 31, and 32 (fig. 5[6]), and in units<br />
BC<br />
~ l BT i<br />
FOSSILS<br />
FIGURE 7.-Total studied stratigraphic section.<br />
Bioturb-led BVC nlr.1~. cast.<br />
above the measured section. Thicknesses in the measured sec-<br />
tion vary from 10 cm (unit 7) to 868 cm (unit 32). Carmel<br />
dololutite units are very light grey with varying amounts of<br />
secondary dolomitization. In general, the upper units appear<br />
massive when fresh, but show laminae roughly 10 cm thick<br />
upon weathering. These rocks have been termed lithographic<br />
limestone by some authors.<br />
Dola smite<br />
Dolarenite occurs as light green or light yellow to light<br />
grey slightly bioclastic ledge-forming beds in units 4, 6, 8,<br />
and 10. The units are very poorly bioclastic or not at all and<br />
often show yellow staining from limonite alteration (fig. 6a).<br />
Units 19, 20, and 23 contain dolarenites which gradually<br />
coarsen upward from dolosiltite. These units contain small<br />
gypsum rosettes 1 to 2 cm in diameter and thin stringers 1<br />
to 2 cm thick, which roughly parallel bedding planes. Unit<br />
28 appears to be a marine reworked dolarenite. Unit 29 is a<br />
dolomitized oocalcarenite in which centers of the oolites re-<br />
main calcareous but the surrounding material is dolomitic<br />
(fig. 6c).<br />
SEDIMENTARY STRUCTURES<br />
Ripple Marks<br />
Most units in the measured section contain ripple marks.<br />
They are predominantly nearly symmetrical bidirectional (bi-
modal) ripple marks and symmetrical oscillation ripples.<br />
Units 2, 3, 6, 8, 9, 11, 15, 16, 17, 19, 21, 25, 26, 28, 29, and<br />
32 contain bidirectional current ripple marks. Units 18 and<br />
23 contain unidirectional current ripple marks. Oscillation<br />
ripple marks are present in units 1, 5, 13, 14, 30, and 31.<br />
Azimuths of transport direction range from 260' to 350'<br />
in the measured section. The lower portion of the section<br />
contains most of the westerly azimuths, and the upper part<br />
contains most of the northerly azimuths. Thus, it would ap-<br />
pear that current transport gradually became dominant over<br />
the effects of wind and tidal transport during the time of<br />
Carmel deposition.<br />
Bimodal ripple marks are particularly well developed in<br />
the fine sandstone and calcarenite lenses in the lowest por-<br />
tion of the measured section. Unimodal ripple marks are<br />
found in the middle of the section in the rocks interpreted<br />
to mark the onset of barrier lagoon deposition. Oscillation<br />
ripple marks are confined mainly to shaly units.<br />
PALEOECOLOGY OF THE LOWER CARMEL FORMATION 57<br />
Mudcncks<br />
Mudcracks are found beneath dolostone lenses in unit 17<br />
and on pieces of float from other units, but the crack fillings<br />
were not seen in place.<br />
An unusual sedimentary structure is shown in figure<br />
8(1). Close examination shows that the randomly oriented<br />
linear ridges are restricted to some portions of the bedding<br />
surfaces of shale. The structure somewhat reminds one of<br />
faint salt hoppers or the salt lineation structures mentioned<br />
by McKee (1957, p. 1734, 1735). The author postulates that<br />
this structure is a modification or an earlier stage of these<br />
salt-concentration lineations. Because the ridges in this new<br />
structure are not oriented in one direction, it is proposed<br />
that salt ridges formed during low-wind conditions or that<br />
they represent an early stage of development before the wind<br />
obliterated all transverse salt ridges.<br />
Flute Casts<br />
PALEONTOLOGY<br />
Flute casts are encountered in units 17 and 18, where<br />
Fossils found in the section include both body fossils and<br />
they are associated with siltstones and silty shales. These feaichnofossils<br />
(trace fossils) and are listed by stratigraphic unit<br />
tures average about 4 cm wide, 3 cm deep, and 15 cm long<br />
in figure 7,<br />
and show a northerly transport direction, which is roughly<br />
Most of the observed body fossils are preserved in carboperpendicular<br />
the direction nate units or in bioturbated mudstone and shale, Bivalves<br />
marks in the same units.<br />
make UD most of them in the studv section of the Carmel<br />
Formation. Some foraminifera also were found in thin sections<br />
of some units.<br />
In general, body fossils are fairly well preserved in the<br />
lower part of the section, but preservation is not uniform.<br />
Thick-shelled forms, such as Glyphaea (?) and Trigonia, tend<br />
to occur as recrystallized calcareous shells, but thinner-shelled<br />
forms, such as Camptonectes and Nucula (?), are preserved<br />
mainly as casts or molds. The occurrence of calcite-lined vugs<br />
in some units indicates much calcite mobilization in the<br />
groundwater. Some of the body fossils have been pyritized<br />
but are now altered to limonite. Some fragments of skeletal<br />
material are present in the coarser-grained bioclastic carbonates.<br />
Ichnofossils are generally well preserved but are limited<br />
to the lower third of the measured section, where many<br />
units contain Ophiomolpha and are highly bioturbated. Arenicolztes<br />
is found in unit 13.<br />
Faunal Assemblages<br />
Many of the fossil assemblages in the section are death<br />
assemblages and therefore have limited use from an environ-<br />
mental standpoint (Boucot 1953). These transported associ-<br />
ations are concentrated in the coarser portions of bioclastic<br />
carbonate units and are represented by disarticulated and frag-<br />
mental skeletal material.<br />
Individual monogeneric assemblages are found in some<br />
units (fig. 8). Unit 12 is characterized by Nucula (?) sp. and<br />
unit 14 by Camptonectes (?) sp. A bigeneric assemblage of Nu-<br />
mla (?) and Gryphaea (?) is present in unit 11, but shells of<br />
both genera are quite widely separated, and probably repre-<br />
sent only scattered remains of the original population.<br />
Only one multiple bivalve assemblage was observed in<br />
the section. The basal red portion of unit 14 contains Tri-<br />
gonza americana Meek, Vaugonia conradi Meek and Hayden,<br />
and Camptonectes stygius White. These species were found close<br />
together and suggest a natural community.<br />
Units 2, 3, 5, 6, 10, 11, 12, and 13 show intense infaunal<br />
bioturbation due to activity of Ophiomovpha and, in some
58 L. H. BAGSHAW
cases, various pelecypods. Unit 13 contains some Arenicofites<br />
and Ophiomorpha burrows.<br />
Autecology<br />
Trigonia and Vaugonia<br />
Well-preserved specimens of Trigonia americana Meek and<br />
Vau~onia conradi Meek and Hayden are found in the dark organ;<br />
shale of unit 13. All specimens in the shale are lying<br />
parallel to a bedding plane but are irregularly oriented on<br />
any plane.<br />
Shells of these species are relatively small, thick, and<br />
lightly ornamented. Trigonia amerirana Meek has curved<br />
raised ribs normal to the hinge line, and Vaugonia conradi<br />
Meek and Hayden has V-shaped ribs normal to the hinge<br />
line.<br />
Modern Neotrigonia margaritacea Lamark is the closest living<br />
representative, and its life habits are used for interpretation<br />
of the Jurassic species. Rogers (1906, p. 380) did<br />
the descriptive work on Neotrigonia margaritacea, and the following<br />
data are drawn from his work. Modern Neotrigonia<br />
possesses subequal muscle attachments and lacks a pallial<br />
sinus. Modern lamellibranchs like Neotrigonia are littoral and<br />
sublittoral species and are epifaunal, or only burrow deep<br />
enough to cover their shells. By extension, Trigonia and<br />
Vaugonia probably did the same.<br />
Camptonectes<br />
Well-preserved specimens of Camptonectes stxius White<br />
were found in most units in the lower portion of the measured<br />
section, but Camptonectes platessfomus White is represented<br />
only by rare shell fragments.<br />
Camptonectes is a pectinid bivalve. Modern pectinids are often<br />
attached to plants or rocks by means of a byssus, and<br />
some species retain this attachment throughout life. In forms<br />
which attach, the right valve has a byssal notch and lies<br />
against the bottom. Coarsely ribbed forms rend to occupy -.<br />
tirbulent marine environments, whereas smoother forms prefer<br />
quieter waters (Easton 1960, p. 348).<br />
Camptonectes are found in the study area associated with<br />
other organisms or concentrated in areas of what were probably<br />
firm substrates, such as bioclastic limestones. A common<br />
occurrence is an occasional camptonectid in a Vaugonia and<br />
Trigonia biostrome. Camptonectes shells are often found in an<br />
orientation somewhat normal to and slightly above that of<br />
either Tngonia or Vaugonia, suggesting that shells of the latter<br />
often serve as points of attachment for Camptonectes.<br />
Gryphaea (?)<br />
Shells identified as Gryphaea (?) are flat, torted valves<br />
with a single muscle attachment. Imlay (1964, p. 483) identi-<br />
fied Glyphaea in the Carmel Formation. In the present study<br />
GtyPhaea (?) are found only in units 10 and 11 of the mea-<br />
sured section, and they are rare there.<br />
Gryphaea and its relatives were sessile filter feeders and<br />
apparently preferred moderately agitated water with high silt<br />
and organic content. Their frequency of occurrence in the<br />
measured section suggests that the waters were less agitated<br />
and murky than those in which the genus thrived.<br />
Modiolus (?) and Nucula (?)<br />
Specimens of Modiolus (?) and Nucula (?) were found in<br />
PALEOECOLOGY OF THE LOWER CARMEL FORMATION 59<br />
the measured section only as casts. No ornamentation or<br />
shell was preserved, so identifications are questionable. Their<br />
presence merely indicates a general trophic level of benthonic<br />
filter feeders.<br />
ENVIRONMENT<br />
General<br />
Several. general statements about the depositional environ-<br />
ments of the Carmel Formation may be inferred: (1) sedi-<br />
ments were deposited in a moderately low energy marine en-<br />
vironmen t with in termi tren t and somewhat rhythmic or<br />
periodic higher energy surges, (2) the hypothetical Jurassic<br />
equator was a few degrees to the southeast in such an orien-<br />
tation (fig. 4) that the study area was in a subtropical-to-<br />
tropica.1 climate, and (3) because of the area's nearness to the<br />
equator, most winds which affected it were from the east<br />
and northeast.<br />
All the preceding regional relationships affected the Car-<br />
me1 Formation of the San Rafael Swell and are used to aid<br />
in interpretation of the different environments of deposition.<br />
Salinity<br />
Imlay (1957, p. 484) and Wilbur and Yonge (1964, p.<br />
502) have assumed normal salinities for the Carmel Sea. Imlay<br />
(1957, p. 502) suggests that the Carmel Sea was magnesium<br />
imooverished.<br />
I<br />
Relatively extensive beds of dolomite and the presence of<br />
exclusively euryhaline organisms indicate a different salinity<br />
realm for deposits of the study area than that assumed for<br />
the rest of the Carmel Sea. The lack of stenohaline echinoderms,<br />
particularly Pentacrinus, in even the lower parts of the<br />
study suggests a higher than normal salinity in these deposits.<br />
Pentacrinus is common in many other areas of the Carmel<br />
and Twin Creek formations (Gilluly and Reeside 1928, p. 75;<br />
Gregory and Moore 1931, p. 72; Imlay 1967; Lowrey 1976;<br />
Maxfield 1974, pers. comm.).<br />
Temperature<br />
Imlay (1957, p. 490) suggested that the temperature of<br />
the Arapien-Carmel-Twin Creek sea was about that of the<br />
modern Borneo Sea. A better modern counterpart for the<br />
Carmel Sea environment of the study area might be the Red<br />
Sea east of Sudan for temperature or the Tunisian coast<br />
(Rigby 1975, pers. comm.) for energy but not necessarily for<br />
temperature.<br />
INTERPRETATION OF SEDIMENTARY ENVIRONMENTS<br />
Three major environments are envisioned in the section:<br />
(1) an early tidal flat, (2) a transitional open marine shore-<br />
line, (3) a barrier lagoon (fig. 9).<br />
Tidal Flat<br />
Tidal-flat sediments dominate in the lower one-third to<br />
one-half of the measured section and are represented by a<br />
series of interbedded green shale and dolostone. Units within<br />
this portion of the section are characterized by nearly sym-<br />
metrical ripple marks which show bimodal or oscillatory east-<br />
west current directions (fig. 7). These two current directions<br />
are thought to correspond to the fluctuation of tidal currents<br />
because of the ripple-mark symmetry and orientation and the<br />
degree of sorting evidenced. The westward moving com-<br />
FIGURE<br />
8.-Fossils and an unusual sedimentary structure. (1) Unusual sedimentary strucrure discussed in text. (2) Trigonia and Vaugonia biostrome of unit 14.<br />
(3) Nucda (?) of unit 12. (4) Camptonerrer and biotutbared character of unir 14. (5) Modiolus (?). (6) Myrilus (?).
ponent of these ripple marks is most often dominant, in-<br />
dicating the seaward movement of the tide in this portion of<br />
the measured section following a pattern observed in other<br />
rocks and on modern tidal flats where currents of falling<br />
tides have greatest energy (Newman 1974, p. 84).<br />
Deposition and current directions in this portion of the<br />
mcasured section were affected by three factors: (1) tidal<br />
fluctuations which tended to come from rhe west or north-<br />
west, (2) wind direction which was predominantly from the<br />
east and (3) longshore currents, as evidenced by flute casts in<br />
some units which show a predominantly northerly direction<br />
of flow.<br />
Shaly layers within this sequence are bioturbated, and<br />
most conrain some authigenic glauconite. Dolostones and<br />
limestones interbedded with these shales are moderately to<br />
very coarsely bioclastic, and most show nearly symmetrical bi-<br />
modal ripple marks. All tidal flat deposits tend to be a light<br />
green or yellow color because of the presence of glauconite.<br />
Flute casts arc more common toward the top of this tid-<br />
al-flat portion of the formation. All observed Carmel flute<br />
casts, as mentioned above, show a northward flowing cur-<br />
rent.<br />
FIGURE 9.-Schematic \ed~mentary model<br />
111<br />
BARRIER<br />
LAGOON<br />
OPEN<br />
MARINE<br />
1ri~a5~<br />
k?~-iC~l!.<br />
I<br />
TIDAL<br />
FLAT<br />
F-N;t+ kEfi.L.2 :...I3<br />
Open Marine<br />
Units 11 through 17 indicate a marine stage. Units 11,<br />
13, 14, 16, and 17 are dark shales, and units 12 and 15 are<br />
bioclastic limestones, all of which contain marine bivalve fos-<br />
sils. The preponderance of bivalves suggests that this marine<br />
interim was probably slightly more saline than open ocean.<br />
This interpretation is reinforced by the lack of the stenoha-<br />
line fossils which are common in other areas of the forma-<br />
tion.<br />
Barrier Lagoon<br />
A summary of the Jurassic physiographic setting of the<br />
area indicates (1) deposition of the Carmel Formation paral-<br />
lels the shoreline (Peterson 1972); (2) current flow parallels<br />
the shoreline (Stanley et al. 1971); (3) prevailing winds are<br />
offshore, to the west (modified from Stanley et al. 1971);<br />
and (4) a shallow, low-sloping shoreline was present (fossil<br />
evidence).<br />
Units 16 and 17 contain microbars (micro-cross-laminated<br />
sand lenses which parallel the shoreline). Unit 18 thickens to<br />
the west (fig. 5[4]) and has flute casts in some portions. It<br />
is a coarse-grained siltstone to fine-grained sandstone which<br />
appears to have filled a longshore channel.<br />
Rock units above and including unit 18 show evidence<br />
of a restricted lagoonal environment and alternating periods<br />
of gradual drying (as evidenced by increasing gypsum con-<br />
tent) and rewetting (dolomitic units and some dolomite so-<br />
lution activity along stylolites). All the upper units contain<br />
large amounts of gypsum or are very dolomitic and virtually<br />
unfossiliferous.<br />
A survey of literature on restricted lagoonal environments<br />
indicates that many of the above characteristics are most<br />
common to barrier environments (Davies ct al. 1971; Dickin-<br />
son et al. 1972). Certainly, the intermittent saline and hy-<br />
persaline deposition in the upper portion of the studied stra-<br />
tigraphic section can be most easily explained by periods of<br />
washover or by breaching of barrier bars.<br />
On the basis of the ~robabilitv of findine barriers in a<br />
physiographic setting as outlined above, the author hypoth-<br />
esizes the presence of Carmel-age barrier bars somewhere west<br />
of the study arra. These barriers would then be the cause of<br />
the restricted lagoon environment evidenced here.<br />
SEDIMENTARY MODEI.<br />
The Carmel Formation was deposited in shallow, warm<br />
waters. An initial transgression of the Carmel Sra covered the<br />
Navajo Sandstone and planed off the eolian dunes.<br />
Variation in sediments over a tidal flat thcn formed alter-<br />
nating marine shale and dolostones as the sea transgressed<br />
and regressed from the shoreline. Subsidence of the depocen-<br />
ter or water level varied so that depth increased to the point<br />
where fairly normal marine salinities allowed increased biolog-<br />
ical activity. Salinity at the time. however, was high enough<br />
to exclude all but bivalves and worms from the area. At this<br />
point, longshore microbarriers or bars began forming off the<br />
shoreline. Terrigenous clastic sediment deposition began to<br />
match marine sediment deposition, and water iirculation was<br />
gradually halted by the barriers until evaporation exceeded<br />
water inflow in evaporating pans or lagoons. Extensive depos-<br />
its of gypsum and dolomite were formed in these lagoons<br />
during periods of evaporation. Occasional surges of marine<br />
waters reentered the lagoonal areas during storms and during<br />
wet portions of the climatic cycle. These marine surges re-<br />
sulted in formation of dololutite and brought in sea water<br />
which could produce more evaporite deposits (fig. 5)
PALEOECOLOGY OF THE LOWER CARMEL FORMATION<br />
CONCLUSIONS dominant transport azlmuth 330'<br />
The Carmel Formation in the study area shows a deposi-<br />
tional style different from that of other portions of the Car-<br />
me1 and Twin Creek formations. Major accumulations of do-<br />
lostone and gypsum in the upper portion of the studied<br />
section indicate that the salinity realm of the Carmel Sea in<br />
the area was much higher than in other areas.<br />
Three environments are represented in the Carmel Forma-<br />
tion of the study area: (1) A tidal flat characterized by inter-<br />
bedded light green shale and dolostone; (2) an open marine<br />
portion of the section, transitional between tidal flat and bar-<br />
rier sequences and represented by some bivalve-bearing bio-<br />
clastic carbonates; and (3) a barrier lagoon environment In-<br />
ferred from the paleogeographic setting and the evapontic<br />
lithologies present.<br />
APPENDIX<br />
Strat~graphic sectlon measured along Interstate 70. The sectlon was measured<br />
from east to west from the top of the Navajo Sandstone rmmediately<br />
west of justensen Flats and ends near the Coppcr Globe Road turnoff<br />
Thrcknerr Total<br />
n m<br />
35 Sdtstone llght green to very light grey, 50 3709<br />
weathers whrte; no apparent bedd~ng, hrghly<br />
gypsiferous (Irke unit 32)<br />
34 Srltstone light red, weathers lrght red to very 84<br />
light gray, no apparent bedding; poorly<br />
indurated, h~ghly gypsiferous, as unrts 32 and<br />
35, except oxrdlzed<br />
33 Srltstone lrght green, weathers llght green to 2 1 3575<br />
very light gray, massrve but poorly indurated,<br />
highly gypslferous<br />
32 Dolostone. very light gray to grayrsh whrte<br />
w~th some med~um brown starnlng, b~modal<br />
npple marks, transport azrmuth 350°, masslve<br />
dololutrte and dolosllt~te wrth some<br />
lnterbedded 20-cm-thlck beds of arg~llaceous<br />
dololunte, Irthographrc, wrth rndrvidual<br />
partrngs approximately 20 cm thlck<br />
868 3554<br />
31 Dolostone very l~ght gray to gny~sh whrte,<br />
weathers wh~te, shaly partrngs, oxrllatron<br />
npplc marks, transport drrectron<br />
rndetermrnate, rrpple mark amplrtude 2 mm;<br />
predornrnantly dololut~te<br />
30 Dolostone. lrght gray to very lrght gray, 78<br />
weathers very lrght gray, oscrllatron npple<br />
marks, transport azimuth 340' to 350°, npplc<br />
mark amplrtude 3 cm, ripple marks have<br />
oolites on crests; predominantly doloslltite<br />
w~th some rnterbedded dololut~te<br />
29 Dolostone very l~ght gray, weathers very lrght<br />
gray wrth light red 'rrdrn', brmodal npple<br />
marks, domlnant transport azrmuth 335'.<br />
npple sets 1 cm th~ck, srylol~trc, stylol~te<br />
ampl~tude up to 6 cm, gypsum concentrated<br />
along stylolrres, predomrnantly dolomrrrzed<br />
46 2588<br />
25 Shale: medrum red, weathers lrght green to<br />
yellow, contalns some lnterbedded 5-cm-thrck<br />
limestone lenses, l~mntone lenses are<br />
brmodally nppled, domrnant transport azrmuth<br />
305"<br />
24 Gypsum. light gray to wh~te, weathers white; 220 2034<br />
basal 14 cm IS gray gypslferous doloslltrte,<br />
gypsum thrckens to the northwest, upper 60<br />
cm tends to be drxolored green by algae at<br />
the surface or along fractures<br />
23 Dolostone I~ght gray, weathers slrghtly<br />
orange-gray, minor unimodal ripple marks,<br />
transport azrmuth 320°, predomrnantly<br />
dolarenrte, some gypsum stnngers and rosettes<br />
present, stnngers roughly parallel beddrng<br />
22 Slltstone medrum red, weathers medrum to<br />
lrght red, shows some soft sedrment<br />
deformation (l~ght mrcrltrc loadrng Into<br />
srltstone), contalns numerous thrn gypsum<br />
seams whrch roughly parallel bedding<br />
21 Srltstone: medrum grayrsh red. weathers<br />
medrum to lrght grayrsh red; brmodal npple<br />
marks, domrnant transport azimuth 340'<br />
20 Dolostone medrum lrght red, weathers<br />
medlum red to lrght red, contains numerous<br />
thrn gypsum stnngers whrch roughly parallel<br />
beddlng, predominantly srlt-size dolarenite<br />
19 Dolostone light gray, weathers lrght gray to<br />
light prnk, b~modal npple marks, domrnant<br />
transport azrmuth 295', shows some soft<br />
sediment ddormatron, wrth mrcrlte loaded<br />
onto dolosrltrte, 25-cm-thrck band of small<br />
gypsum rosettes at top of bed<br />
18 Sltstone. lrght brown, weathers lrght gray-<br />
brown to lrght red, un~modal npple marks,<br />
transport azimuth 295", unrt thrckens from 85<br />
cm to 115 cm In the western portron of the<br />
exposure<br />
17 Shale lrghr gray to lrght medrum gray,<br />
weathers l~ght gray to lrght medrum gray,<br />
dolom~tic; b~modal ripple marks, domlnant<br />
transport azlmuth 350'; r~pple sets 1 to 15<br />
cm, lnterbedded 17-cm-thrck fine-grarned,<br />
rrppled sandstone, mudcracks present under<br />
sandstone lenses<br />
16 Shale lrght gray to llght gray-brown, weathers<br />
to lrght medlum gray or brown; calcareous,<br />
b~modal npple marks, domlnant transport<br />
azimuth 350°, npple sets 1 to 15 cm,<br />
b~oclast~c, falrly well-preserved brvalve casts,<br />
some fine sandstone lenses<br />
59 698<br />
15 Lmestone l~ght gray to Irght medrum gray,<br />
weathers l~ghr gray to l~ght medlum gray;<br />
brmodal r~pple marks, transport azlmuth 270°,<br />
grades from th~n-lamrnated calcrsdt~te wrth<br />
npple lamrnatrons to medrum-bedded<br />
calcarenrte, some brvalve casts present<br />
oolrtlc calcaren~te 14 Shale dark gray, weathers medrum gray to<br />
28 Dolostone. lrght yellow, weathers lrght to<br />
med~um yellow, bimodal r~pple marks,<br />
domlnant transport azrmuth 325', npple sets<br />
2 5 cm thlck, predominantly dolaren~te,<br />
appears to be reworked marenal<br />
39 2542<br />
27 Srltstone. light yellow, weathers very Irght<br />
yellow to very l~ght gray, highly gypslferous,<br />
top 20 cm contarns abundant pillows of<br />
gypsum up to I cm In d~ameter, gypsum<br />
plllow abundance increases toward top<br />
216 2503<br />
26 Srltstone. medium gray, weathers light yellow- 114 2287<br />
green, top 30 cm darker yellow, wrth<br />
rncreaslng gypsum, bimodal rrpple marks<br />
l~ght gray, lower 20 cm has red stalnlng,<br />
calcareous, lentrcular calcarenrte lnterspcd,<br />
onillarron npple marks, transport azrmuth<br />
260°, some concretrons wrth sparry fillrngs,<br />
pclecypod and other b~oturbatron, particularly<br />
abundant Tngonza, Vaugonra, and Camp~onerte~<br />
casts in lower 10 cm<br />
13 Shale llghr green, weathers l~ght green,<br />
glaucon~trc, symmetrical osc~llatron r~pple<br />
marks, transport drrect~on 295', many<br />
rnterbedded calcarenrte lenses, shale contalns<br />
Ophiomorpha, Armolrlec top llrnestone<br />
coqulno~d with Tngonra, Campfonecfer, and<br />
other blvalves
12 Lmestone l~ght gray-green, weather? l~ght<br />
gray-green, glaucon~r~c, calcaren~te made up of<br />
b~~~clasts and c)olttes In sparry cement,<br />
bloturbatcd, ~ncreasingly ool~tlc toward top,<br />
contalns Nurula (') and Camptonrctr~<br />
11 Shale l~ght gray-green, weathers l~ghr graygreen,<br />
glaucon~rlc, b~modal npple marks,<br />
dom~nant transport d~rectlon 26So, calcareous.<br />
tntcrbedded calcarrn~re lenses, bloclast~c,<br />
conralns Gryphara (Z) and Nurula (')<br />
10 Dolostone l~ght yell~~w-gray, weathers<br />
med~um yellow-gray, sl~ghrlv glaucon~t~c.<br />
basal Ioad castlng on dolom~tc ledges.<br />
bloclastlc, dolaren~tc w~th mln11r ~nterbedded<br />
arg~llaceous dololut~te<br />
9 Shale l~ght gray-green, wcxthers l~ghr graygreen,<br />
glauc(~n~t~c, b~modal r~pple marks.<br />
dnm~nant transport az~muth 285O, contalns a<br />
thln sandy unlr r~pplcd and Ioad deformed<br />
onto soft muds<br />
8 Dolostone. l~ght gray, weathers l~ght grav to<br />
l~ghr yellow-gray. sl~ghtly glaucon~tlc, b~m(dal<br />
npple marks, transport az~murh 290°, Ioad<br />
castlngs at base of dolostone, bloclast~c<br />
dolaren~te<br />
7 Dolostone l~ghr gray to ltght yellow-brown,<br />
weathers l~ght gray to l~ght yellow-brown,<br />
sl~ghtly glaucon~t~c, argillaceous dol~lut~te<br />
(I~ke that contained tn unlr 6)<br />
6 Dolostone med~um ltght gray to l~ght yellowbrown,<br />
weathers to l~ght yellow-brown.<br />
slightly glaucon~t~c, b~modal r~pple marks,<br />
transport az~muth 290". marcaslte along jolnts<br />
In dolostone, bloturbated, poorly bloclastlc,<br />
dolaren~te w~th some mlnor ~nterbedded<br />
arg~llaceous dololut~te<br />
5 Shale l~ght gray-green, weathers l~ght graygreen,<br />
glaucon~t~c, osc~llatton r~pple marks.<br />
transport az~muth 250", clay r~pple mark<br />
trough fillings, upper portlon w~th small<br />
sandy lenses, l~ke unlt 3<br />
4 Dolostone light to med~um yellow-brown,<br />
weathers med~um yellow-brown, sl~ghtly<br />
glaucon~t~c, b~oclast~c, w~th poorly preserved<br />
b~valves In lower 4 cm and some gently<br />
nbbed fragments, some pyrlte or l~mon~te<br />
foss~l molds, mlnor ool~tes<br />
3 Shale l~ght yellow-green, weathers med~um<br />
yellow-brown, glaucon~tlc, b~modal r~pple<br />
marks, domlnant transport az~muth 320'.<br />
contalns thln (1 cm or less) sand lenses and<br />
gypsum layers, minor Ioad castlng ev~dent at<br />
top, bloturbared<br />
2 Shale 11ghr green, weathers l~ght to med~um<br />
green, glaucon~t~c, b~modal r~pple marks,<br />
transport az~muth 310°, contalns small, thln<br />
(2% cm or less) sand lenses, upper portlon<br />
l~mon~te stalned, clay partlngs between npple<br />
sets, b~oturbated<br />
1 Sandstone. l~ght yellow-brown, weathers l~ghr<br />
to med~um yellow-brown, symmetrical npple<br />
marks, transport az~muth 310'. limon~te<br />
starned toward top<br />
Base of Carmel Formarlon<br />
Navajo Sandstone<br />
Sandstone l~ght yellow, weathers light yellowbrown,<br />
crossbedded, cross-bed sets 80 cm thlck,<br />
transport az~muth approx~mately 285'<br />
REFERENCES CITED<br />
Baker, A A, Dane, C H , and Rees~de, J B, Jr. 1936. Correlal :Ion of the<br />
Jurasslc format~ons of parts of Utah, Anzona, New Mex~co, and Colo-<br />
L H BAGSHAW<br />
rado lJ S Geol Surv Prof Paper 183. 66 p<br />
Boucot. A J. 1953. 1.1fe and death a\\c.mblagcs dmong foss~ls Amcr Jour<br />
SCI. v 251, p 25-40<br />
Davlc\. D K. Ethrldgc. F G . and Berg. R R , 1970. Rccogn~t~~~n of barrlcr<br />
env~rt~nments Amer Assoc Petrol Geol Bull, v 55, p 550-65<br />
D~cklnu~n, K A, Rcrryhtll. H I.. Jr, dnd Holmc\, C W , 1972, Cr~tcr~a for<br />
recogn~~~ng dnclcnt hdrrler coastl~ncs In R~gby. J K . and Hamblln,<br />
W K (cds ). Recogn~tlon of anclcnr x.d~mcntdrv cnv1r
Structure, Stratigraphy, and Tectonic History of<br />
the Indianola Quadrangle, Central Utah*<br />
DAVID M. RUNYON<br />
Southland Royalry Cu., Dmuer, Cularadu 80012<br />
ABS~HACT -Three dla~lrs have been d~scovercd ~n wurhern Utah and norrh- The followine made financial and loeistical contr~butions:<br />
crn Sanpere counrles Thex plcrcemcnr strucrures have recurrenrly upwelled<br />
and collapsed, creatlng local unconform~r~cs, faulting, doming, ovcrturnlng of<br />
srara, and a varlery of possible hydrocarbon rraps Ground-warer sysrems have<br />
removed the upper portlons of rhe d~ap~rs, thus lnirlarlng surface collapse<br />
brecc~a, Thex aquifers zubxquently depos~ted rhe evaporltes Into the Great<br />
S~gma Xi (The xclentific Research soci:ty of North America),<br />
Amer~can Assoc~at~on of Petroleum Geolog~sts, Lloyd<br />
Traupe of Marathon 011 Company, Mr. and Mrs G. D.<br />
Runyon, and the Utah Nat~onal Guard. Special thanks are<br />
Salt Lake Bas~n<br />
The prexncr 1)f slllc~fied ool~rlc I~mcsmnes locarcd adjacenr to volcantc<br />
boulder deposits makes ~mpl~carlon of concealed source venrs for the Ol~gocent<br />
volcan~cs which 11e w~rhln and adjacenr to rhe Indianola quadrangle<br />
The sudy area has becn acrlvely Involved In the blrth and desrructlon of<br />
due Max G. Pltcher of Continental Oil Company who made<br />
h~s expertise and a number of Conoco faciliries accessible.<br />
Ned Foreman prov~ded remote senslng analysis techniques. E.<br />
J N~eves examlned and Interpreted samples processed for poltwo<br />
geosyncl~nes, the Cordllleran and rhe Rocky Mounra~n Ir l~es near the<br />
rr~ple Intrrxcrron of the Colorado Platrau. Bas~n and Range, and Cenrral<br />
Rocky Mountain physlographlc provinces Magneric data suggesr rhe presence<br />
of the cratonal edge beneath rhe Wasatch monocllne, and ~r is felt rhar rh~s<br />
"h~ngt Ilne" reglon may make added conrnbur~ons ro a plate tectonic model<br />
len and spores. Karl W. Schwab (and William C. Elsik of<br />
Exxon Company) also made palynological interpretations and<br />
took photomicrographs Dennis E Palmer (and Mke Plnnell<br />
of Un~on-Texas) proofread and made organ~zat~onal suggesfor<br />
central Utah concerning a poss~ble Jurassic r~fr bas~n and a Cretaceous<br />
zubducr~on zone<br />
The Srvlcr orogmy, Laramlde epelrogeny, and Grear Basin raphrogeny are<br />
conz~dered as xDarare. , dlsrincr recronlc evenrs whlch have made s~enlficanr<br />
, "<br />
conrr~bur~ons ro srrucrural and strar~graph~c expressions In central Urah<br />
[Ions<br />
Alan T Washburn (formerly of Union Oil Company) offered<br />
valuable lnterpretatlons of seismic and gravity dara concernlng<br />
tectonics<br />
Morr~s Peterson of <strong>Brigham</strong> <strong>Young</strong> <strong>University</strong> asslsted<br />
INTRODUCTION with low oblique aer~al photography, and George E <strong>Young</strong><br />
The challenge of the thesis was to produce a ground-pro- proofread and ass~sted measuring strat~graph~c sections. James<br />
ven map of the lnd~anola quadrangle and to unravel the se- Stolle ass~sted In field flora ~dentlfications, and Lehi F. Hlntze<br />
quence of tectonlc history. Previously th~s same area was in- suggested the thesis problem and served as commlttee memvest~~ated<br />
by Khln (1956) and Mase (1957), and they ber. Specla1 grat~tude is extended to James L. Baer, who<br />
produced a broad-scale geologic study The present study has served as commlttee chairman and supplied invaluable experproduced<br />
a decalled map uslng a topograph~c base map and<br />
convent~onal stereo high-alt~tude aer~al photographs. Secondtise<br />
in the field.<br />
Finally, I am grateful to my loving wife who excused<br />
arlly, remote sensing techn~~ues analyzing Sky Lab Jll photos many extended absences from the family.<br />
and ERTS imagery were employed, as well as low obl~que Prevlous Work<br />
late afternoon shadow photography In addltlon, verbal cornmUnlCatlOn<br />
of InterpretatlonS made from selsmlc 2nd gravity<br />
data were offered to me by a petroleum company These<br />
modern lnvestlgatlve tools, coupled with standard ground<br />
procedures, led to the discovery of some unexpected newly<br />
recognized dlaplrlc structures 2nd also aided in solving some<br />
perplexrng strat~graphlc problems In the area<br />
Acqulsltlon of these new data allows a new lnterpretatlon<br />
concerning the geologic evolution In this part of the state<br />
However, at the outset one must realize that to make longrange<br />
extrapolations about such things as plate encounters<br />
from such a small portion of the globe is like vlewlng a dlstant<br />
planet through the wrong end of a giant telescope Although<br />
~t does seem futile to ISC CUSS h~nge-he tectonics<br />
w~thout enlightenment from such a r~ch source of theories,<br />
far-reach~ng conclusions whlch outstretch sohd data are really<br />
only speculat~ve and will be presented In this dlscusslon with<br />
appropriate qualificar~ons. Establ~shed acceptable dara will be<br />
stated factually, and speculation will be treated for what it 1s<br />
thought provoking, but not absolute.<br />
Central Utah has attracted the attentlon of many geologists<br />
since the lace 1880s. Gilllland (1951), who worked the<br />
Gunnlson quadrangle, and Hams (1953), who worked the<br />
Blrdseye quadrangle, both give good accounts of reconnaissance<br />
efforts by ploneer scientists. While dolng a ground-water<br />
study, R~chardson (1907) produced a general recon map<br />
whlch lncluded some s~mpllfied structure and srrat~graphy<br />
Eardley (1932, 1934), Hlntze (1962), and Stokes (1956a) have<br />
done some reglonal geologic analysis of the southern<br />
Wasatch Mounta~ns and vlcin~ty. Schoff (1951) investigated<br />
the Cedar Hills, and Plnnell (1972) produced an accurate<br />
map and unraveled the rectonlc h~story of the Thlstle quadrangle.<br />
McGookey (1960) contributed some valuable stratlgraphic<br />
data south of Indlanola, 2nd Hardy (1952) made slgnifican[<br />
geologic contrlbutlons, also to the south.<br />
The most comprehensive work In specific detailed areas<br />
began In the early 1900s and was done by Spieker (1936,<br />
1946, 19492, 1949b) and Spleker and Reeside (1925) Khln<br />
(1956) and Mase (1957), working under Spieker7s direcrion,<br />
completed master's theses that taken together lncluded the<br />
Indianola quadrangle. Because neither adequate topographic<br />
Acknowledgmenrs base maps nor aer~al photographs were then available, the~r<br />
Numerous people and organlzatlons have contr~buted a~d geolog~c map 1s not des~rable for an accurate representation<br />
toward th~s study I hope th~s recognltlon will be accepted as of the geology present. Therefore, I have endeavored to uponly<br />
a small portion of my grat~tude for their unselfishness. date the geology of the Ind~anola quadrangle<br />
*A rhcn, prcwnrr;d r\, chc Dcp.l
GEOLOGIC EVOLUTION AND REGIONAL SE'ITING<br />
Since Cambrian tlmes the Indianola area seems to have<br />
Listric faults, older fault planes folded by the occurrence of<br />
younger structurally low& positioned thrusts, also support<br />
been situated on the western edge of the stable shelf durlng the idea of gravity gliding during the Swler orogeny.<br />
the existence of the Cordilleran geosyncline. Except for local The problem of crustal foreshortening has been studied<br />
disturbances-the Tooele Arch (Ordovicran), the Stansbury by several authors, and most have agreed on an average fig-<br />
Conglomerate (Devonian), and the Oquirrh Basin (Pennsyl- ure of 65-95 km regionally although in some places, such as<br />
vanlan-Permian) - the Cordilleran miogeosyncline remained the Nebo, Canyon, and Pavant ranges, the shortenrng IS berelatively<br />
calm from late Precambrian until the Jurassic, re- lieved to be 15-25 km of horizontal translat~on (Hlntze<br />
cervlng mostly only clean carbonate and sandstone sediments 1962).<br />
(Hintze 1973). The sediment transport prlor to the Jurassic Regionally this disturbed belt stretches from southern<br />
was from the east and southeast, at least in the central Utah Nevada to Alaska and came into being from Late Jurassrc<br />
area-for example, the Moenkopi and Shinarump formations untrl the Eocene (McGookey 1972). Locally, however, in<br />
were derived from the ancestral Rocky Mountain highlands eastern Utah a more applrcable date would be Early Crein<br />
Colorado and northern New Mexico. In Early to Middle taceous to latest Mastrictian times, when Price River con-<br />
Jurassic the depositional pattern began a gentle shift due to glomerates were laid over the thrust plates. In most cases<br />
the dlstant Nevadian orogeny. Seas invaded now from the they have not subsequently been displaced by compressional<br />
north, and this region In Utah must have contained some forces.<br />
enclosed basrns and tidal flat environments, possrbly created Regionally thrs zone of major crustal deformation IS a<br />
by a r~ft valley, which produced the mud and thick salt de- belt approximately 150-250 km wide. There are numerous<br />
posits of the Arap~en and the sllt of the Twist Gulch Forma- differences of structural styles on a local basis, but they may<br />
tion Then durlng Morrison tlmes there was apparently an- be due simply to different degrees of uplift and relative ages<br />
other gradual reglonal shift in the dralnage pattern as stream of individual disturbances within the orogenic belt.<br />
and lacustrine sediments began to appear in the central Utah Overlapping the Sevler orogeny chronologically but demregion<br />
(W. K. Hamblin 1973 pers. comm.) This fluvratlle onstrating a s~gnificantl~ different structural style was the<br />
system was belng built frorn west to east on the p~edmont Laramide orogeny, or perhaps more correctly the Laramide<br />
surfaces of the uplifting Mesocordilleran high withrn the epeirogeny. It was a linear belt east of the Swier highlands<br />
miogeosynclinal belt. Previous to this time and through this which extended from Mexico to Canada. Its movement beregional<br />
change the central Utah area was near sea level and gan in Late Cretaceous and continued through Eocene times<br />
had a warm climate which lasted until late Tertiary tlmes rn vertical and asymmetrical uplifts many of whlch are fault<br />
(McGookey 1972).<br />
bounded at depth. They created a new episode of minor local<br />
The aforementioned drainage shift constitutes the begrn- gravity sliding, new sediment sources, and baslns of localning<br />
of the Sewer orogeny as defined by Armstrong (1968). deposition The Flagstaff and Green River lakes were Impor-<br />
Frrst came the upllft and possibly some folding in Late Juras- tant features of this time. This disturbance is attributed by<br />
sic, and then in Early Cretaceous the thrusting began. It was Eardley (1963) to gabbroic intrusions beneath the sial.<br />
not a slngle event of upheaval and eroslon, but rather a se-<br />
Oligocene time brought on numerous volcanic events<br />
quence of numerous orogenic pulses, at least three major<br />
throughout Utah. The eruptions were basically srlicic and inones.<br />
They were eastward-migrating pulses that were accomtermedrate<br />
types of ash falls and agglomerates. The newly<br />
panied by an asymmetric foredeep positioned east of the ororecognized<br />
hot water vents north of Thistle (<strong>Young</strong> 1976)<br />
geny. Thls foredeep consumed the majority of the sediments<br />
and possibly the vents located in the Tintic mrning dlstrict<br />
produced by denudation of the highlands. The sediments<br />
are believed to be responsible for the Tertrary age volcanic<br />
were deoosited on the western flank of the mobrle foredeeo<br />
1<br />
conglomerates<br />
and were continually cannibalized and recycled thus creating - within the Indianola study area (Morris 1957)<br />
some clastic deposits composed of multrple second-generation<br />
The Basin and Range taphrogeny postdates the Oligocene<br />
volcanic events, begins in Early Miocene, and contrnues<br />
clasts. This sediment consumption was accentuated by the<br />
through present times. It is a system of steep normal faults<br />
beginning of an imbricate gravity glide system. Denudation<br />
wlth roughly a north-south orientation that has produced<br />
and gliding were aided by east-sloping surfaces which develhorst<br />
and graben, range and valley, and also the rnternal<br />
oped structural weaknesses caused by abnormally high pore<br />
dralnage characteristrc of the Great Basin physrographic propressures<br />
In the natural aquifers created by the migrating<br />
vince. Concurrently the accompanyrng explosive volcanic sums<br />
pulses of energy (Eardley 1967). The result was that by Early<br />
changed frorn Oligocene felsic and rntermedrate types to<br />
Cretaceous, compressional thrusting was well under way and<br />
dominantly basaltlc extrusive floods (Eardley 1963)<br />
was shoving the thlck miogeosyncllnal sediments over the<br />
unstable shelf and onto the cratonal edge over the thin shelf The final main event of tectonrc history began when the<br />
sediments of the Colorado Plateau as we know them today. eastern Great Basrn and adjacent foreland were uplifted<br />
The next structural development was to lead to the birth of 3,000-25,000 m regionally. This movement has continued to<br />
the Rockv Mountain eeosvncline. The flood of sediments the present and has produced such renowned features as the<br />
D 2<br />
shed from the dylng thrust belt accumulated to great thick- entrenchment of the San Juan and Colorado rlvers and the<br />
nesses and represent a basin filled with high-energy "Gilbert" existlng topography<br />
deltas, marine sandstones, and thick lacustrine sequences.<br />
This entlre sequence of evolution from the Jurassic untll<br />
As noted by Armstrong (1968) the structural weaknesses today is believed to have begun wlth a plate collrsion bewhich<br />
served as glide planes for Swier thrusting were usually tween the Paclfic and Amer~can plates which ~nstlgated the<br />
in Eo-Cambrian quartzite and shale beds. He accounts for a Sevier orogeny. The Latamide eperrogeny was a result of congravity-thrusting<br />
mechanism by the allochthonous plates tinental override of a Cretaceous subduction zone where the<br />
being thin, one to two mrles thick, and unmetamorphosed at Farralon plate was being consumed. The Basin and Range<br />
their bases, except for some speclfic instances In the hinter- crustal extension and extrusive change to basalt floods was<br />
land of the Sevier belt in western Utah and eastern Nevada. frorn the collision of the East Pacific Rise and mid-Tertlary
trend along the North American continental margin (Atwa-<br />
ter 1970).<br />
This brief geologic review has brought us to the main<br />
topic. Hopefully it has given us the necessary background to<br />
realize the implications of the problems which lie within the<br />
Indianola quadrangle.<br />
PRESENT-DAY SETTING<br />
Indianola (fig. 1) is now cradled in the heart of a triple<br />
intersection of physiographic provinces. Fenneman's bound-<br />
aries place the eastern half of the study area in the Colorado<br />
Plateau. To the west is the eastern Great Basin section of<br />
the Basin and Range province, and to the north is the<br />
southern tip of the Central Rocky Mountains. The study<br />
area has been located within or near two separate geosynclin-<br />
a1 hinge lines for most of its geologic existence. These are<br />
the Rocky Mountain and Cordilleran geoclines, according to<br />
the tectonic model constructed by Robert Dietz (1972).<br />
Analysis of basement faulting does reveal that the mapped<br />
area is an expression of a tectonic triple junction and repre-<br />
sents the deposition and destruction of a hinge-line geosyn-<br />
cline.<br />
Topographic evaluations at Indianola range from 1800<br />
meters in the valley to almost 2750 meters atop Brown's<br />
Peak. In general, normal faults, collapsed salt domes, and a<br />
major monocline control the topography. The fault blocks<br />
are downthrown to the west and have been tilted to the<br />
east, thus presenting a rugged steep western front and a<br />
gentle eastern slope. Valleys eroded along the lines of dis-<br />
placement reveal the geology with a clarity not often found.<br />
Sanpete and Sevier valleys have developed along extensions of<br />
the Sevier and Markagunt faults on the downthrown side of<br />
the Wasatch monocline (Buss 1363). Generally the western<br />
valley fronts are steepest because of a complication of fault-<br />
ing and monoclinal folding, and the eastern front, if steep, is<br />
erosional.<br />
The terrain is reasonably accessible for eight months of<br />
the year by four-wheel-drive vehicles or horseback and hiking.<br />
The climate is semiarid. Numerous species of wildlife are<br />
abundant. The land is cared for in the valley and foothills by<br />
farmers and ranchers and in the highlands by the U.S. Forest<br />
Service.<br />
FIGURE I.-Index map.<br />
INDIANOLA QUADRANGLE 65<br />
STRATIGRAPHY<br />
From Late Cretaceous on, the Indianola area was effec-<br />
tively removed from marine invasion and was completely<br />
dominated by continental orogenic processes. The sedimen-<br />
tary record from Cretaceous to Oligocene (fig. 2) is the<br />
foundation crf proof for the Sevier and Laramide orogenies<br />
and their recurrent effects on the Rocky Mountain geosyn-<br />
cline. Sedimentation was then dominated by fluvial systems,<br />
Gilbert-type deltas, intense subaerial erosion, and widespread<br />
lacustrine environments. The interaction of these systems cre-<br />
ated thick deposits and formations which more often than<br />
not have an exceptionally high number of lateral facies<br />
changes. Lithologies are commonly monotonous and their<br />
boundaries transitional or gradational. It is certainly not un-<br />
common even for an experienced geologist to mistakenly<br />
confuse one formation with another on the basis of rock<br />
type or color alone. Fossils are unusually rare, and when<br />
found they are not likely to yield a diagnostic age, although<br />
they may be reliable environmental indicators. For these rea-<br />
sons I attempted to collect a few pollen-prone samples from<br />
critical locations in the hope that some of the stratigraphic<br />
dilemmas might be resolved. Unfortunately, this endeavor<br />
met with limited success.<br />
e.tre8m c~lmemtes<br />
rprse algel bells<br />
qusrtzite bwlder con-<br />
glomerate, oolitic lime-<br />
=tones, elgnl balls old<br />
mts, Ostracods, pollen<br />
qunrt?lte conglomemtes,<br />
algal bslls, pollen,<br />
assortad fresh voter<br />
sn-ils and elnos<br />
quartzite and limestone<br />
boulder conglmerntes,<br />
concretions, "GIANT"<br />
algsl bslls, Goninb.isis,<br />
Cretaceous mmnl bonos<br />
mRS5iVe q"cltziLC<br />
boulder con~lmeistCs<br />
with thin clii.nnel sands<br />
0' fluvial c!isnnel suiids,<br />
86~0rtcfl pliciit debris,<br />
q"BrLzite 8-3 Hmcstonc<br />
boulder con~lo:r!er3tc,<br />
~yalic aerlioientation<br />
Pcnt?crii.iis<br />
FIGURE 2,-Stratigraphic column of rocks exposed within the Indianola quad-<br />
rangle.
JURASSIC<br />
Arapien Shale<br />
The type section is located in Arapien Valley which par-<br />
allels the Wasatch Plateau near Gunnison, Utah. Exposures<br />
are also found along Twelve Mile Creek west of the valley.<br />
E. M. Spieker (1946, p. 123-24) named this formation and<br />
defined two members, the lower member being the Twelve<br />
Mile Canyon and the upper being the Twist Gulch. How-<br />
ever, since the Twist Gulch has been raised to formation<br />
rank (Spieker 1946, Hardy 1952), the Arapien is now consid-<br />
ered to be a formation containing only the Twelve Mile Can-<br />
yon Member, which name seems to have faded from usage.<br />
Hardy (1952) recognized five units, A through E, within the<br />
Arapien separate from the Twist Gulch. Gilliland (1951) also<br />
made some refinements on the Arapien terminology.<br />
The base of the Arapien Formation has not been ob-<br />
sewed at the surface in Sanpete or Sevier County. It was pre-<br />
sumed by Spieker to overlie the Navajo Sandstone, and his<br />
presumption has been verified by drill bit as reported by Rit-<br />
zma (1972) in the Levan and Sigurd areas. The Arapien lith-<br />
ology is exposed in the study area at one small linear out-<br />
crop on the southwest wall of Little Clear Creek Canyon in<br />
sections 7 and 8. It is mostly covered except for an isolated<br />
spot exposed at the intersection of East Lake Fork Canyon.<br />
Here the rocks dip very steeply and may even be overturned<br />
(?). They are overlain by the Price River Conglomerate to<br />
FIGURE 3.-Vertical outcrop of Twist Gulch rocks in stream cut of Hjork<br />
Creek. Width of photo is 5 m.<br />
D. M. RUNYON<br />
the east and overturned South Flat (?) Sandstone to the<br />
west. Pinnell (1972) considered this contact to be a sedimen-<br />
tary angular unconformity, but I believe the Arapien has<br />
been emplaced next to the Price River by diapiric drag fault-<br />
ing, which has resulted in the subsequent overturning of the<br />
South Flat (?) and even some Price River rocks. Although<br />
no salt or gypsum is present on the surface because of re-<br />
moval by solution activity, the Arapien is known to produce<br />
numerous other diapiric . structure; in Sanpete valley. Gyp-<br />
sum outcrops and is being mined from an exposed diapir at<br />
the mouth of Salt Creek Canyon near Nephi, Utah.<br />
Piercement structures caused by the mobility of the Ara-<br />
pien have played an important role in the geologic evolution<br />
of the Indianola area. Three diapiric structures are clearly ex-<br />
pressed at the surface, as shown in figure 19, but only the<br />
one at East Lake Fork actually exposes the Arapien lithology.<br />
The conical hill in section 16 near Hjork Creek was described<br />
by Khin (1956) as Arapien rocks exposed within a complex<br />
maze of tear faults. I disagree with his stratigraphic identi-<br />
fication and structural interpretation. It is an uplifted, radi-<br />
ally faulted dome, a diapir which has upwelled and partially<br />
collapsed because of various effects on the underlying Ara-<br />
pien evaporites. The exposed sediments, which have been<br />
stretched and folded, belong to the Twist Gulch Formation<br />
(fig. 3). The third structure interpreted as a collapsed diapir<br />
forms low-relief hills of brecciated Green River sediments at<br />
the base of the frontal scarp of the faulted Wasatch mon-<br />
ocline in sections 12, 13, 17, and 18 (fig. 4).<br />
These piercement structures which Lave penetrated to the<br />
surface are the first to be recognized this far north in central<br />
Utah. It is believed that they have an important structural<br />
significance related to the present-day valley.<br />
As was noted by Khin (1956), a major drainage divide is<br />
formed within the Indianola quadrangle. North San Pitch<br />
Creek and everything south via the San Pitch River flows<br />
into the Sevier Lake drainage basin. All the streams north of<br />
the divide dump into Thistle Creek and eventually discharge<br />
FIGURE 4.-Vertical photograph of the N. San Pitch River collapsed diapir.<br />
Diameter of the diapir is approximately 1.3 km. Dashed pattern de-<br />
notes faulted frontal scarp of Wasatch Plateau on right side of photo.<br />
North is at top of photo.
into the Great Salt Lake. Since the or~gin of the high con-<br />
centrations of salt and gypsum of the Salt Lake has been<br />
somewhat puzzling, I agree with H. J. Bissell's (1970 pers.<br />
comm.) observation that the Arapien sediments in Sanpete<br />
Valley may have contributed a significant portion of the<br />
Great Salt Lake evaporites.<br />
The lithology of the Arapien exposures (see appendix) in<br />
East Lake Fork consists predominately of light cream and<br />
buff-colored shale, thin-bedded mudstone, and fine-grained<br />
sandstone, some of which show oscillation ripple marks. The<br />
only fossils from this section were reported by Pinnell<br />
(1972). They were whlte crinoid fragments and Camptonectes<br />
rtygrus. I collected samples for pollen and spore analysis, but<br />
they proved to be barren of any dlagnostic forms. However,<br />
E. J. Nieves (1974 pers comm.) mentioned that floral frag-<br />
ments suggested a near-shore, possibly tidal-flat, environment.<br />
Lithologlcally the Arapien of East Lake Fork appears<br />
equivalent to the Twin Creek exposed near Thistle. The<br />
units do have some basic differences, but Imlay (1967) sug-<br />
gests they are at least time equivalent if not facies related, as<br />
noted by J L. Baer (1974 pers. comm.). The Arapien is also<br />
believed equivalent to the Carmel of the San Rafael Group.<br />
Baker, Dane, and Reeside (1936, p. 6) assigned ~t an age of<br />
Upper Jurassic. Imlay (1948) speculates an age as old as<br />
Middle Jurassic for the Arapien as well as for the lower part<br />
of the Carmel. Thus, without further fossil evidence it seems<br />
appropriate on a regional correlation basis to assign an age of<br />
Middle and/or Upper Jurassic to the Arapien of East Lake<br />
Fork Canyon.<br />
INDIANOLA QUADRANGLE 67<br />
38O to vertical (fig. 3). The lower contact has collapsed and<br />
is faulted against the upper portion of the Indianola Group.<br />
The upper contact may also be faulted but is in near proximity<br />
of depositional contact with the stratigraphically overlying<br />
Indianola Group (fig. 19).<br />
The other diapir 1s a linear outcrop of Twist Gulch<br />
which forms the lower portion of the west canyon wall of<br />
Little Clear Creek. It has been brought up with the same diapiric<br />
actlon that overturned (fig 19, A-A') the South<br />
Flat(?) which forms the opposite canyon wall and the lower<br />
structural contact. The upper contact on the west side of the<br />
outcrop was believed by Khin (1956) to be a fault contact,<br />
but I interpret it as a depositional feature where the stream<br />
deposits of the Oligocene volcanic rocks were la~d In angular<br />
unconformity against the Twist Gulch and other units as in-<br />
dlcated In fieure 19.<br />
"<br />
At both these locations the sections are incomplete. A<br />
section was measured In L~ttle Clear Creek Canyon and is<br />
contained in the appendix of this paper. The lithology IS a<br />
repetitive cyclic sequence of thin- to medium-bedded red<br />
sandstone, laminated to th~n-bedded green and red s~ltstone<br />
and brick red-brown mottled shale. Pentacrinus IS the only re-<br />
ported fossil (Baer 1974 pers. comm.) except for uniden-<br />
t~fiable carbonized woody material in the crinkled shales at<br />
the base of the measured sectlon.<br />
The Twist Gulch correlates regionally with the Entrada,<br />
Curtis, and Summerville formations of the San Rafael Group.<br />
Hardy (1952 p 27-28) compares the lower 850 m of Twist<br />
Gulch In Salina Canyon with the Entrada and the upper 60<br />
m wth the Curt~s and Summerville. Others (Wright &<br />
Dickey 1963, Sp~eker 1946, 194913) make s~m~lar correlat~ons.<br />
Tw~st Gulch Formarlon<br />
The drast~c thinnine " of the Twist Gulch Format~on in<br />
The type section is located on the north wall of Sal~na the Indianola area is due to drag faulting caused by the dia-<br />
Canyon in central Utah, where its basal contact w~th the un- piric upwelling of the underlying Arapien, not by depos~tionderlying<br />
Arapien is not exposed. The upper contact IS with a1 differences as Pinnell (1972) suggesred.<br />
variegated shales and diverse strata of the Morrison (?) For- Samples for spore and pollen analysis were collected from<br />
mation It was originally named by Spieker (1946, p. 124) the Twist Gulch at the local~ty of the measured section, but<br />
and intended to be a member "above the red salt bearing" the results were negative. Although no other dlagnostic fossil<br />
Twelve M~le Canyon Member of the Arapien. But, as pre- data has been reported, field relat~onsh~ps indicate its age to<br />
viously discussed, it was later separated out and raised to formation<br />
rank because of its distinctwe color, I~thology, and rebe<br />
Upper Jurassic (Imlay 1967, chart p. 20; see appendix).<br />
gional distribution.<br />
Khin (1956) and Mase (1957) reported the Twist Gulch<br />
underlying Morrison (?) strata immediately south of Smith's<br />
CRETACEOUS<br />
Indlanola Group<br />
Reservoir. I searched for this Morrison (7) unit and decided<br />
that either we d~sagree on the identification or that the ex-<br />
The Indianola Group was named by Sp~eker (1946, p.<br />
126) and lies between Hjork Creek and Dry Creek about 6<br />
posure lies to the north beyond the boundary of the In- km north of the Ind~anola townsite. These rocks are the olddianola<br />
guadrangle.<br />
est Cretaceous units known in central Utah and represent a<br />
The Tw~st Gulch was mapped at two locations within drastic change in the pattern of sedimentation from the Corthe<br />
quadrangle. It was reported at a th~rd locality by Sp~eker d~lleran geosyncline of the continental shelf to the Rocky<br />
(1946, p. 136-37, 1949b, p 88-89). This latter occurrence was Mountain geosyncline of the continental Interior. Spieker<br />
supposedly northeast of Blackhawk at Indian Graves hog- (1946) made some suggestions of correlation and subdiv~sion<br />
back. There, In linear outcrop approximately "one hundred but later had to go to other localities to set apart d~sfeet<br />
long at the bottom of a small valley, steeply-dipping<br />
Twist Gulch was seen to be overlain by nearly hor~zontal<br />
Flagstaff Limestone.". Mase (1957) reports search~ng for this<br />
tinguishable formatFons, thus describ~ng the type sict~on as<br />
"Indianola (und~fferentiated)." In ascend~ng - order the formatlons<br />
of the group are the follow~ng:<br />
exposure in the summer of 1955 without success. I too, 1. Sanpete Formation, which is descr~bed as a basal group<br />
searched on more than one occasion for the described out- of sandstone, conglomerate, and minor shale containing foscrop<br />
but also met with d~sappointment. This relat~onship of sils of Colorado age. Its type locality is south of Manti,<br />
the Twist Gulch and Flagstaff obviously has some Important Utah, on the east s~de of the valley exposed as a serles of<br />
tectonlc implications<br />
hogbacks. Lithology suggests correlation between ~t and the<br />
One of the two mapped Twist Gulch exposures is adja- lower conglomerates on Hjork Creek and in the Cedar Hills, as<br />
cent to Hjork Creek in section 16. It was described in the noted by Schoff (1951), and the Gunnison Plateau, as noted<br />
Arapien stratigraphic section as the center of a domal uplift. by Hunt (1954).<br />
This is a series of red silt, sand, and shale which dlps from 2 Allen Valley Shale, largely consisting of a unlform,
even-bedded, gray marine shale containing fossils of Middle<br />
Colorado age. Its type locality is in Allen Valley about 4 km<br />
southwest of Manti. It does not seem to have a correlation<br />
equivalent in the group (undifferentiated).<br />
3. Funk Valley Formation is a sand-shale sequence of ma-<br />
rine origin that yields fossils of Niobrara age. The type sec-<br />
tion is in Funk Valley 6.5 km southwest of Manti. The ma-<br />
rine sandstone of Dry Creek is the group (undifferentiated)<br />
equivalent although Spieker states that nonmarine strata of<br />
the same age are probably abundant and widespread at the<br />
group type section.<br />
4. Sixmile Canyon Formation is a thick succession of<br />
coarse-grained, gray sandstone and conglomerate containing a<br />
coal-bearing member. Fossils collected from the coal indicate<br />
an age of Early or Middle Montana, but not younger. The<br />
type section is in Sixmile Canyon immediately east of the<br />
Funk Valley Formation.<br />
Spieker (1946, p. 129) illustrates in his cross-section from<br />
Hjork Creek to Little Clear Creek that the coal-bearing sand-<br />
stone of the Sixmile Canyon Formation is involved in an an-<br />
ticlinal structure. However, I have identified this feature as<br />
overturned beds of South Flat rocks. Previous to the naming<br />
of the South Flat Formation, Little Clear Creek is the only<br />
locale other than the type section that he speculated on as<br />
an occurrence of the Sixmile Canyon strata. He has since<br />
changed his mind because of Hunt's (1954) work and al-<br />
lowed this speculation to be corrected. Thus the Sixmile<br />
Canyon ~orm'ation is believed to exist only at its type local-<br />
ity adjacent to Funk Valley.<br />
Spieker (1946) and Khin (1956) measured the Indianola<br />
Group (undifferentiated) and came up with about 610-915<br />
m at Dry Creek and 2130-2440 m at Hjork Creek. Schoff<br />
(1951) reports over 460 m in the Cedar Hills 13 km west of<br />
the type section. It is obvious that these are very thick units<br />
of mollasse type sediments (fig. 5). They are traceable to<br />
theeast as they interfinger, fine, and become correlatable with<br />
the Lower Mancos and possibly some of the Middle Mancos<br />
of Colorado. They are also believed equivalent to the Kelvin<br />
Formation of the southern Wasatch Mountains (Eardley<br />
1932).<br />
Generally the lithology of the undifferentiated group con-<br />
sists of alternating conglomerate, sandstone, shale, and a few<br />
thin beds of fresh-water limestone. Oncolites are common in<br />
the sandy, silty units and seem to be most directly associated<br />
with the red-orange oxidized sediments. The average bedding<br />
thickness ranges from 30 cm to more than 20 m. Pebbles in<br />
the conglomerate range from 2.5 to 30 cm in diameter and<br />
consist of quartzite of various colors and dark gray to blue-<br />
black Middle Paleozoic limestones. Limestone cobbles are<br />
abundant in some beds and scarce in others. Sandstones are<br />
commonly light gray, orange, or yellow-brown and are often<br />
highly calcareous in the lower part of the section. Some of<br />
the red-orange sands near the upper section, especially the<br />
ones containing algal balls, bear a remarkable resemblance to<br />
the North Horn sediments. This resemblance can be con-<br />
fusing at times. For example, I am not sure that in section<br />
17 the stratum identified as Indianola is not really North<br />
Horn. Here they demonstrate identical lithologies. This ap-<br />
parent unconformity, if actually present, seems a real possi-<br />
bility since Pinnell (1972) reports just such a relationship in<br />
the Lake Fork area. Unfortunately there is no fossil evidence<br />
to give anv suvport to the idea, so the stratum has been<br />
Hjork Creek appear to be different, in part because of some<br />
perplexing structural problems and rapid facies changes.<br />
The rocks which Spieker (1946) photographed north of<br />
"Hjork Creek Dome" may not be Price River, as he calls<br />
them. Lithologic composition and interpretations made from<br />
seismic data reveal that these rocks may belong to the In-<br />
dianola Group (fig. 5) and present a major unconformity be-<br />
tween the Indianola Group and the North Horn Formation.<br />
If it is the correct relationship, which seems plausible, it con-<br />
tributes even stronger support for the model of diapirism in<br />
that it represents a local hiatus rather than a regional ero-<br />
sional break.<br />
Spieker (1946) and Khin (1956) report some marine<br />
brachiopods from the uppermost sand unit on Dry Creek<br />
which yielded a Coloradoan age. I unsuccessfully tried to<br />
confirm this age with a pollen sample.<br />
South Flat Formation<br />
The type section was named by Hunt (1954, p. 121) and<br />
is located in the northern half of the Gunnison Plateau. It is<br />
separated from the underlying Indianola Formation and the<br />
overlying Price River by angular unconformities. The South<br />
Flat is lithologically uniform and does not demonstrate the<br />
rapid facies changes of most other Cretaceous units in the<br />
central Utah area. This uniformity is one reason it has been<br />
equated with the Blackhawk Formation (Pinnell 1972, p.<br />
100). Concerning this, Spieker (1946, p. 130) states:<br />
Attention may be directed to the fact that the west-<br />
ernmost Blackhawk rocks exposed are no coarser in<br />
grain than those to the east. This suggests that by<br />
middle Montana time the highlands from which the<br />
coarse sediments of Colorado age were derived had<br />
been worn down. It seems likely that by middle<br />
Montana time the rate of subsidence in the geosyn-<br />
clinal belt had slowed down. It might also be noted<br />
that the western outcrops of the Blackhawk Forma-<br />
tion are so close to the belt of Laramide folding<br />
that the original presence of early and middle Mon-<br />
tana sediments in the folded belt seems almost cer-<br />
tain.<br />
Hunt (1954) suggests that the South Flat was being de-<br />
posited in piedmont and flood-plain environments of the oro-<br />
genic belt while the littoral marine Blackhawk Formation<br />
maFped as brigi;l'allY defined by ~pieker. FIGURE<br />
>.-Ourcrop of vertical Indianola-Price River? rocks on Hjork Creek.<br />
Within the study area the units on Dry Creek and Black line is a fault.
was being deposited farther east. Whether this unit has re-<br />
corded a dying phase of the Sevier orogeny (Armstrong<br />
1968) or an early pulse of the Laramide orogeny (Armstrong<br />
1968) is hard to say at this point. One confusing fact about<br />
the South Flat Formation is that, where the section was mea-<br />
sured at Little Clear Creek (see appendix), there is a min-<br />
imum thickness over 600 m of almost entirely fluvial sand. It<br />
is considered a minimum thickness because the base of the<br />
formation is not exposed, and the measurement was taken<br />
from a fault contact. Yet only 3 km to the northwest, at the<br />
head of Hjork Creek, the unit is completely absent. This<br />
presents a picture of erosion and rugged topography in the<br />
Late Cretaceous, but the sediments do not reflect any coarse,<br />
high energy deposition. The upper contact is not exposed<br />
well enough to determine if it really is conformable to the<br />
Price River Formation on Rock Creek, but measurements on<br />
either side of the creek suggest a possible ten-degree diver-<br />
gence. Khin (1956) reported it as a conformable contact. Ac-<br />
tually the disagreement may be only minor, and, for the pur-<br />
pose of recreating a sequence of tectonic events, this upper<br />
contact will be treated as at least a disconformity if not an<br />
angular unconformity.<br />
The South Flat rocks in the northern portion of Little<br />
Clear Creek Canyon (fig. 6) have been overturned by the col-<br />
lapse of a diapir (fig. 7), the feature that Spieker (1946) mis-<br />
takenly called an anticline.<br />
The exposure of the South Flat Formation north of In-<br />
dianola is the only one known exclusive of the type section<br />
in the Gunnison Plateau. Because of the confusion expressed<br />
by several other workers in identifying these rocks, I traveled<br />
to the Gunnison Plateau to examine the outcrops as they<br />
were originally defined. I found that they do bear a remark-<br />
able resemblance to the rocks near Indianola, not only lith-<br />
ologically, but especially in the common occurrence of iron<br />
(limonitic) concretions and some plant debris. Hunt (1954,<br />
p. 126) found six different flora in the Gunnison Plateau,<br />
and I found three types north of Indianola, all three of<br />
which commonly agree with those reported by Hunt. They<br />
are:<br />
Cinnammum afine Lesquareux<br />
SabaIiitps mmatanrrJ (Lesquareux) Dorf<br />
Fragments of dicotyledonous leaves<br />
FIGURE 6.-Massive conglomcntcs of the Price River Formation in background<br />
outcrop on the cast face of Rock Creek Canyon. In foreground,<br />
the dashed fault pattern denotes contact of overtumcd South Flat rocks<br />
on the left with right-side-up South Flat rocks on the right.<br />
INDIANOLA QUADRANGLE 69<br />
R. W. Brown of the USGS identified these plants found by<br />
Hunt in the type section as Upper Cretaceous in age. These<br />
fossils are preserved in light gray, fine sandstone and without<br />
exception have been replaced by limonite.<br />
One thin discontinuous coal seam at Rock Creek was<br />
sampled for spores and pollen. No diagnostic forms were pre-<br />
served, but Schwab (1974 pers. comm.) said that the plant<br />
debris present indicated a fresh-water flood-plain environment.<br />
So, on the basis of plant leaves and stratigraphic position, I<br />
agree with Hunt (1954) that the best assignment for age is<br />
Early and/or Middle Montana. I also agree with Spieker,<br />
Khin, and Hunt that the best name for the rocks exposed<br />
on Little Clear Creek is South Flat Formation.<br />
Price River Formation<br />
The Price River was named by Spieker and Reeside<br />
(1925, p. 445-48) from exposures in Price River Canyon near<br />
Castlegate, Utah. It is a succession of gray sandstone, grit,<br />
conglomerate (fig. 6), and minor amounts of shale that lie<br />
between the Blackhawk Formation below and the North<br />
Horn Formation above. The Price River at the type locality<br />
consists of two members: a basal, cliff-forming unit, the Cas-<br />
tlegate Member (Clark 1928, p. 20), composed of massive,<br />
white-to-brown, medium-to-coarse sandstone containing lenses<br />
of quartz and chert pebbles; and an upper, less massive,<br />
slope-forming member of similar lithology. Progressing west-<br />
ward from the Castlegate area the facies coarsen drastically<br />
and become dominant cliff-forming masses of high energy<br />
elastics. It is this boulder-sized unit which exclusively com-<br />
FIGURE 7.-Formline contour map of the study quadrangle. The elevation<br />
contours are drawn on top of the North Hom Formation. Contour intewal<br />
is 150 m.
prises the Pr~ce R~ver l~thology of the Indianola distr~ct Here what Spieker has termed "postorogenic conglomerates," and<br />
it is relied on as a marker unlt. It IS th~s coarse lithology, he attributes them to the first record and strongest pulse of<br />
and In part ~ts stratigraphic relat~onships, that prompted the M~ddle to Late Montana Laram~de orogeny Thus, the<br />
Moussa (1965, p. 113) to call the unit at Rock Creek the Price Rlver Format~on, espec~ally In the Indianola area, is be-<br />
Benn~on Creek - Formation. However his conclus~ons come l~eved to represent a whole new tectonlc event, one which<br />
only on the bas~s of l~terary research since he never personal- has a style s~gn~ficantly d~fferent from the previous Sev~er<br />
ly Inspected this unlt near Ind~anola Also he made this de- orogeny<br />
duct~on from Mase's (1957) observat~on that the "overlying The coarse western fac~es of the Prlce Rlver IS barren of<br />
North Horn was a conformable contact," and th~s IS not the any fosslls, a fact not hard to understand when one views<br />
case In the East Lake Fork Canyon.<br />
th~s h~gh energy deposit with rounded quartz~te clasts which<br />
There are two major exposures of the Pr~ce Rlver Forma- commonly range from grlt slze to 46 cm In d~ameter. Howtlon<br />
contamed w~thln the Ind~anola quadrangle. One is on ever, its stratlgraph~c posltlon (as related to the orogeny), to-<br />
Dry Creek where ~t clearly overl~es the Ind~anola Format~on gether w~th fossils reported by Spieker (1946) from the sandy<br />
with aneular d~scordance. The other 1s a much thicker sec-<br />
w<br />
tlon on the eastern face of Rock Creek Canyon, where ~t exfacles<br />
In the Castlegate area, yields an age of Late Montana<br />
An assumption can be made that this coarse westernmost<br />
tends cont~nuously northward across the dramage divide for facies is a b~t younger, belng In closer proxlmlty to the oroseveral<br />
kilometers out of the study quadrangle On the west geny, so a date of poss~ble Mddle and/or Late Montana IS<br />
side of Rock Creek Canyon atop the dra~nage d~v~de and given. Spieker (1946, p 131) places the Price R~ver equlvacontlnulne<br />
northward there IS a thln sectlon of Price R~ver lent to the Fru~tland and K~rtland format~ons of the San<br />
w<br />
several thousand meters long which has been faulted, tipped Juan reglon, Colorado<br />
vert~cal, and sl~ghtly overturned along w~th the South Flat<br />
Format~on It has been overturned by collapse of the hear<br />
diapir at Llttle Clear Creek. At the Rock Creek sectlon of<br />
CRETACEOUS-TERTIARY<br />
Puce Rlver rocks, the lower contact w~th the underlying<br />
North Horn Formanon<br />
South Flat 1s very near conform~ty, unl~ke the exposures at The North Horn was first ~ncluded by Sp~eker and Rees-<br />
Dry Creek and Hjork Creek<br />
~de (1925, p. 448) as the lower member of the Wasatch For-<br />
Another exposure, at the head of Hjork Creek, IS an im- mation Later lt was rarsed to format~onal rank (Sp~eker 1946,<br />
presslve outcrop of masslve conglomerates whlch stand on<br />
end and form enormous bulbous pinnacles (fig 5) The base<br />
p 132) because ~t was d~scovered to be not entlrely Tert~ary<br />
in age After the unearthing of fossils that y~elded a Lance<br />
of these rocks appears to represent an angular discordance<br />
with the underlying Indianola formatlon, but th~s relat~onage,<br />
Sp~eker (1946, p 132) defined a new type locality on<br />
North Horn Mountaln whlch IS on the east s~de of the<br />
ship is most l~kely due to complex faulting and masking by Wasatch Plateau opposite Mant~, Utah. There he descr~bed<br />
eroslon These are the rocks which Spieker (1946) called four main unlts whlch are mostly vanegated shale with sand-<br />
Pr~ce R~ver A close Inspection of the clast composltlon re- stone, conglomerate, and some fresh-water Ilmestone. Th~s<br />
veals a d~fference from other nearby exposures In that quart- sectlon IS 500 m thlck and In th~s part of the plateau reprezlte<br />
no longer predomtnates, but there IS rather an abun- sents an alternat~on of fluv~atlle and lacustrlne cond~t~ons<br />
dance of Jurassic age sandstone clasrs. Also seismic The rocks wlthln the Indianola quadrangle are slm~lar to<br />
lnterpretatlons made by Alan Washburn (1975 pers. comm.) the type sectlon but do have some minor differences At the<br />
show that In the subsurface thls hor~zon forms an uncon- Indianola d~str~ct the North Horn is predom~nantly calformity<br />
wlth the overly~ng North Horn For these reasons careous sand, algal unlts, conglomerate, and mlnor shale<br />
the outcrop 1s shown w~th a quest~onable des~gnat~on of affi- Sand IS the most abundant, conglomerate IS common, shale<br />
nlty in figure 19<br />
and l~rnestone are rare The last two are usually thln and dis-<br />
At all the descr~bed local~t~es the Price Rlver grades tran- continuous over large areas. They are representatives of small<br />
sit~onally Into the overlylng North Horn Format~on 11th- d~sconnected lakes wh~ch encroached on the fluv~al plalns<br />
olog~cally, but In the East Lake Fork Canyon there seems to and were short llved ~f not ephemeral. The conglomerate<br />
be a sllght angular discordance of about lo0 However, th~s normally contalns abundant Paleozo~c limestone clasts, whlch<br />
relationsh~p dies out, and the contact appears concordant fur- help to dlstlnguish it from the Pr~ce River Formarlon in this<br />
ther south For mapping purposes the contact was placed area They are thought to be channel systems rhat were deatop<br />
the uppermost, masslve, quartzitlc conglomerate It IS a posted Into an external dramage system (Hamblin pers.<br />
slmple boundary to plck, not only because of fhe masslve na- comm.). Th~s conclusion comes not lust from the~r chanture<br />
of the rocks, but mainly because the color is usually neled nature (fig. 8) but also from the~r belng, In many<br />
some shade of light gray, contrasting w~th the red and or- cases, open-work conglomerates.<br />
ange of the North Horn. The clasts are dom~nantly quartz~te Other conglomerates rhat make the sedimentary unlts of<br />
with some sandstones present. Paleozoic l~mestone clasts are this area unlque (figs. 9, 10) are the masslve deposlts of "alcons~~cuouslv<br />
absent. In some olaces the Pr~ce R~ver has<br />
L I<br />
been stalned red w~th hemat~te from the overlylng North<br />
gal ball" calcareous sandstone and sandy l~mestone What<br />
makes them unlque IS the~r slze and re'urrent d~str~but~on<br />
Horn, but th~s colorat~on appears to be only surficial In na- They occur not only In the North Horn Format~on but<br />
ture Except for Dry Creek, where Plnnell (1972) reports 75 throughout Tertiary unlts l~ke the Flagstaff, Green R~ver,<br />
m, the th~ckness IS fairiy constant At Hjork Creek I mea- and even the volcan~c conglomerates However, the North<br />
sured about 300 m, and on Rock Creek the unlt is 250-300 Horn Formarlon seems to have them most abundantly spread<br />
m thlck<br />
throughout ~ts 11m1ts and exclus~vely contains the glgantlc<br />
Although Moussa (1965) strongly d~sagrees, Spleker forms which often range in d~ameter from 2 5 to 50 cm<br />
(1946) clalms rhat the two members of Prlce R~ver defined Malcolm We~ss (1969) studled the algal balls of the<br />
In the Castlegate area grade impercept~bly Into th~s coarse North Horn and Flagstaff format~ons In the central Utah remasslve<br />
unlt as ~t exlsts In the study quadrangle These are glon and concluded-that they were formed In near-shore,
INDIANOLA QUADRANGLE 71<br />
warm, shallow, active waters, often near the mouths of dianola was Hydrobia. I also sampled several shales for pollen<br />
streams. He even claims that several types are distinguishable analysis and found no diagnostic forms. However, some of<br />
as either autochthonous oncolites or allochthonous forms. the organic debris in the samples did suggest a fresh-water<br />
The oncolites found in the Indianola vicinity do seem to fit environment.<br />
his theorv in that thev are eenerallv autochthonous. Some TERTIARY<br />
0<br />
oolitic beds are also locally common near the top of the for- Flagstaff Formation<br />
mation. I do not deny that these algal balls may have even- ~h~ ylagstaff limestone formerly of the<br />
tually reached the lake waters, and I concede that some may<br />
havi even been generated completely within the lake bound-<br />
aries, but I do not believe it to be true for the very large<br />
balls. These "giants" originated in streams of moderately<br />
high gradients. The climate was warm, and surface vegetation<br />
was a cacti type. The nucleus for the balls could be virtually<br />
anything as they generated and saltated downstream. They<br />
probably were maintained in the stream channel and grew<br />
most rapidly during flood stages of the fluvial systems. This<br />
simple hypothesis is shared with R. J. LeBlanc, Sr. (1975<br />
pers. comm., Shell Research).<br />
North Horn sediments range in color from bright red to<br />
cream white, but the dominant color is medium red-orange.<br />
Van Houten (1948, p. 2083) investigated the colors of vari-<br />
ous Cenozoic formations and came to the conclusion that<br />
variegated formations such as the North Horn were depos-<br />
ited in open country of savanna environments. In contrast to<br />
the gray Price River below and the whites and tans of the<br />
Flagstaff and Green River formations above, the consistent<br />
orange color of the North Horn is a reasonably reliable<br />
marker in the studv area.<br />
Stratigraphic relationships between the Price River and<br />
North Horn formations in the Indianola district are varied.<br />
As previously mentioned, there is a slight angular divergence<br />
between the two as demonstrated east of Rock Creek and<br />
East Lake Fork Canyon. It is due to renewed upward move-<br />
ment of a diapir and helps to date its recurrent movement.<br />
The upper contact northwest of West Lake Fork is con-<br />
formable and clearly transitional with the Flagstaff, but non-<br />
conformable with the volcanics further southwest. On<br />
Brown's Peak, the crest is capped by a tongue of question-<br />
able Flagstaff (?) origin. But the Flagstaff (?) immediately<br />
east of the Blackhawk hogback seems to have a position at-<br />
tained by "strip thrusting" similar to the type Moussa (1965<br />
p. 93) and Hardy (1952) describe in some of the Green Riv-<br />
er sediments of central Utah.<br />
The age of the North Horn was first thought by Spieker<br />
to be Early Tertiary, but the discovery of reptilian bones near<br />
the base df the foimation proved it to be in part Upper Cre-<br />
taceous. Fossil bones of placental mammals found in the up-<br />
per portion of the formation proved it to be in part Paleo-<br />
cene. Thus Spieker announced (1946, p. 135) that the<br />
passage from Cretaceous to Tertiary lies within the body of<br />
the formation. He also proceeded to correlate the North<br />
Horn with the Lance and Fort Union formations of Wyom-<br />
ing and Ojo, Alamo, Puerco, and Torrejon formations of the<br />
San Juan Basin. No physical or lithological basis for regional<br />
subdivision of the strata grouped in the North Horn Forma-<br />
tion has been recognized, and as presently understood a<br />
boundary between Cretaceous and Paleocene cannot be map-<br />
ped.<br />
Reeside identified several fresh-water mollusks from<br />
North Horn rocks (Spieker 1946, p. 134). Their significance<br />
is regarded as uncertain because of the general reputation for<br />
long ranges of these fresh-water faunas. The type commonly<br />
found in the Indianola area which coincides with that noted<br />
by Spieker is Goniobasis. One form noted by La Rocque<br />
(1956, p. 140) and not by Spieker which I found in In-<br />
FIGURE %-Channel deposits in the North Horn Formation located on Black-<br />
hawk hogback.<br />
FIGURE 9.-"Giant" algal balls in the North Horn Formation on Jones 1<br />
Ridge. Note hammer for scale.<br />
FIGURE<br />
10.-"Pigeon egg" algal ball from the North Horn Formation near<br />
Blackhawk hogback.
Wasatch Formation, was defined by Spieker and Reeside<br />
(1925, p. 448) as a fresh-water, white limestone that appeared<br />
consistently between units previously called "upper and lower<br />
members of the Wasatch Formation." Later Spieker (1946, p.<br />
135-36) raised the unit to formational rank and called it the<br />
Flagstaff Limestone. At the type section it is mostly compos-<br />
ed of white to buff weathering lacustrlne limestone with in-<br />
terbedded gray calcareous shales. Minor occurrences of sand-<br />
stone, volcanic ash, oil shale, and carbonaceous beds are<br />
common. In other localities it is not uncommon to find a<br />
vastly different lithologic sequence occupying the same stra-<br />
tigraphic horizon. Gilliland (1949, p. 70) reports such a case<br />
in the Gunnison Plateau where it contains a considerable<br />
amount of sandstone and conglomerate. A similar lithology<br />
is reported by Stolle (1974 pers. comm.) on Long Ridge<br />
southwest of Levan, Utah. Gilliland found the term limestone<br />
inappropriate and substituted formation. McGookey (1960, p.<br />
596) and La Rocque (1951, 1960) followed suit and also em-<br />
ployed the term formation rather than its descriptive counter-<br />
part limestone. Thus Flagstaff Formation is the name applied<br />
to equivalent rocks exposed in the Indianola area.<br />
Regionally, the upper contact of the Flagstaff is with ei-<br />
ther the Colton Formation or the Green River Formation.<br />
The Colton is a predominantly red sequence of sediments of<br />
fluvial origin that were initially considered the uppermost<br />
member of the Wasatch Formation. It is absent in the In-<br />
dianola area as well as in the Thistle quadrangle (Pinnell<br />
1972), thus connoting a high during Colton or pre-Flagstaff<br />
time in this region.<br />
Three different exposures of Flagstaff occur within the<br />
Indianola quadrangle, each distinct from the other. Two of<br />
these are even questionable Flagstaff. The exposure in sec-<br />
tions 12 and 14 northwest of Little Clear Creek is a southern<br />
continuation of the units exposed in Dipping Pen Creek in<br />
the Thistle quadrangle, a series of limestone, shale, and sand<br />
similar to the type section. However, one unique unit bears<br />
attention. It is an oolitic limestone that has been completely<br />
replaced by silica. It does not appear in outcrop, but it is 10-<br />
cally prevalent as slope wash and therefore does not appear in<br />
the description of the measured section. I do not deny the<br />
occurrence of some siliceous limestones in other Flagstaff lo-<br />
cations or the possibility of transportation of this material<br />
from another area, but the nature of fragmental angularity<br />
and local distribution suggests that it is very near its in situ<br />
position. Possibly it had collected as talus and was later mod-<br />
ified by uplift and modern sedimentation such as colluvial<br />
deposits. In any event the point to be made is that the<br />
unique and total silicification of this "sedimentary" material<br />
may be due to a nearby volcanic vent. This possibility does<br />
not seem too far fetched since the Flagstaff here is covered<br />
by materials of a volcanic affinity. Admittedly, these are dom-<br />
inantly stream-transported deposits at this location, but the<br />
possibility of a concealed vent is not ruled out.<br />
The Flagstaff (?) atop Brown's Peak is markedly distinct<br />
from the units just described. Here the rocks are dominantly<br />
clastic. Clean quartz sand, calcareous sand, algal balls, and<br />
thin laminar white limestone are present. Mase (1957)<br />
mapped this as Flagstaff and reported that Spieker had identi-<br />
fied appropriate fauna. After studying regional characteristics<br />
and traveling extensively throughout central Utah to view<br />
the Flagstaff, as well as other stratigraphic units, I concluded<br />
that the rocks which cap Brown's Peak may be a tongue of<br />
the Flagstaff Formation. Its clastic nature suggests elther a<br />
fluvial equivalent or a near-shore mud flat, as evidenced by<br />
shallow, lacustrine limestones which oftentimes display mud<br />
cracks healed with calcite.<br />
The third exposure of Flagstaff, again questionable, is lo-<br />
cated between Indian Graves hogbacks east of the townsite<br />
of Indianola. The outcrop here is relatively small and does<br />
create some confusion. Spieker (1946) reported finding the<br />
Flagstaff in "dramatic" angular unconformity with the Ara-<br />
pien. Mase (1957) and Khin (1956) looked for this exposure<br />
and could not locate it, even with the benefit of Spieker's<br />
personal directions. I too spent considerable time seeking this<br />
unconformable surface and met with frustrating failure. How-<br />
ever, the lower contact of the rocks that are here seems to<br />
be at a slight angular discordance with the North Horn.<br />
This may be due to postdepos~tional gravitational gliding<br />
similar to that reported by George <strong>Young</strong> (1975 pers.<br />
comm.) west of Thistle, Utah. The sllppage occurred along<br />
either unconformable de~ositional lanes or within in-<br />
I<br />
competent shale beds. In any event the aftermath apparently<br />
demonstrates, on a small local scale, some form of sedimen-<br />
tary tectonism or structural failure from secondary dia-<br />
strophism.<br />
The lithology here too is mostly clastlc and is not easily<br />
differentiated from the overlying Green River, with which it<br />
may indeed be confused. Surface samples yield a strong pet-<br />
roliferous odor when freshly broken, indicating that at some<br />
time these rocks may have been a hydrocarbon reservoir. This<br />
is entirely feasible since several kilometers to the north near<br />
Thistle, Utah, the Flagstaff Formation contains prolific tar<br />
sands.<br />
The upper contact with Green River rocks IS not clear; it<br />
seems to be faulted but may actually be transitional as point-<br />
ed out in other areas by Spieker (1946, p. 136), White<br />
(1886) at Wales, Utah, and La Rocque (1960, p. 73).<br />
Not only IS the lithology of the Flagstaff in Indianola<br />
questionable, but its age is somewhat dubious. Spieker (1946,<br />
p. 136) dates it as probable Paleocene. Palynomorphs and or-<br />
ganic debris seen in samples collected from the questionable<br />
Flagstaff indicate an age of Upper Paleocene and Lower Eo-<br />
cene, but these particular forms are not rel~able for specific<br />
dates. However, one algal form, Pedia~trum, does Indicate a<br />
fresh-water environment. A suggested correlatron from these<br />
results is beneath but near the Wasatch-Fort Union bound-<br />
ary in Wyoming which is considered to be a<br />
Paleocene-Eocene time division marker. (Schwab, Nleves, El-<br />
sik 1975 pers. comm.).<br />
In summary it is only falr to mention that the Flagstaff<br />
lithology is very similar here to the Green River, and in real-<br />
ity a division of the two wlthin the Indianola quadrangle<br />
may not be fair to elther.<br />
Green R~ver Format~on<br />
The Green River Formation was named by Hayden<br />
(1869, p. 90) from exposures near Rock Springs, Wyoming.<br />
It was deposited into two basins separated by the Ulnta<br />
Mountains. The famous oil shale deposits are contained in<br />
the northern basin, Goshiute Lake (King 1878, p. 446). The<br />
southern basin, Uinta Lake (Bradley 1930, p. 88), includes<br />
the study area and demonstrates lithologies of higher energy<br />
envlronments. They seem to be more clastlc as a whole, and<br />
oil shales are rare if not absent. Spieker (1949, p. 35) recog-<br />
nized two distinct members in the Sevier County area. The<br />
lower is blue-gray to light blue shale, and the upper is cream<br />
to tan limestone. The Green Rlver sediments within the In-<br />
dianola quadrangle seem to differ greatly from these adjacent
areas. The formation is characterized by numerous con-<br />
glomerate units which reach 6-9 m in thickness. The clasts<br />
are predominantly pink and white quartzites with some dark<br />
limestones. The quartzites are from the Eo-Cambrian and<br />
Cambro-Ordovician Tintic and Eureka formations. The dense<br />
limestones bear Devonian and Mississippian marine fossils<br />
and often occur beneath units composed exclusively of<br />
quartzite, but this is not a strict rule. Mase (1957, p. 40) was<br />
correct when he gave credit to streams of great carrying ca-<br />
pacity which drained highlands immediately adjacent to the<br />
basin. This stream action created eastward extending boulder<br />
fans which extended into the lake and is why shales some-<br />
time interfinger with the conglomerates. In my opinion, this<br />
section in the southern part of the Indianola quadrangle rep-<br />
resents deltaic deposition of the classic Gilbert type. This the-<br />
ory is hard to demonstrate in the field because most of the<br />
Green River has been eroded from atop the Wasatch Plateau<br />
during the folding and faulting of the Wasatch monocline.<br />
However, the cuestas which are exposed here do remain true<br />
to form and exhibit a variety of lithologies and an unusual<br />
sequence of stratigraphy. There are some minor oil shales and<br />
ashy units present. Massive biostromal algal limestones are<br />
not uncommon, many of which have been silicified and are<br />
similar to those which McGookey (1960) describes several<br />
kilometers to the south. Some oolitic units are also present<br />
at Snail Hollow. It should be easy to recognize that Green<br />
River time provided a colorful sedimentary history in the<br />
limited area of these outcrops.<br />
In areas adjacent to the Indianola townsite where the<br />
Green River Formation is present, its base is in contact with<br />
either the Colton or the Flagstaff Formation. These are<br />
gradational contacts and, in the case of the Colton, represent<br />
a change of environment from fluvial to lacustrine. At In-<br />
dian Hollow, however, the Green River is faulted against<br />
questionable Flagstaff, Along the frontal scarp of the<br />
Wasatch Plateau the Green River has been faulted down<br />
against the North Horn. In the area north of Milburn a<br />
small series of cuestas has been interrupted structurally by a<br />
piercement diapir. It is evident from aerial photos that re-<br />
moval of the soluble contents of the diapir has taken place<br />
causing the cap rock of Green River to collapse creating<br />
breccia and a "caldera type" effect (fig. 4).<br />
Pollen samples were taken near the Green River-North<br />
Horn fault contact and did yield some helpful but limited re-<br />
sults (fig. 11). The age determined for this Lower Green<br />
River shale was Upper Paleocene-Lower Eocene. Determina-<br />
tions were based on the presence of Aquilapollenites sp. and<br />
the high percentages of Pistillipollmites mcgregorii. The latter is<br />
always, or nearly always, common of the Lower Eoc-<br />
ene-Upper Paleocene contact. This is especially true in<br />
Wyoming where the greater concentration is near or at the<br />
Wasatch- Fort Union boundary.<br />
Pistillipollenites mcgregorii becomes more scarce higher in<br />
the section, i.e., Upper Wasatch and Green River. The envi-<br />
ronment of deposition is continental with some fresh-water<br />
transport involved and/or a fresh-water lake. This conclusion<br />
is predicated on the presence or absence of the algae Pediast-<br />
rum sp. It is worth noting that Plrrtycary sp. was not found<br />
in these samples; otherwise an age of Lower Eocene could<br />
positively have been given. However, had it been found, it<br />
would also prove to be no older than Lower Eocene.<br />
In most places of deposition into Uinta Lake, the Green<br />
River is thought to be Middle Eocene, but the accepted age<br />
is considered to be restricted only to the Eocene. The rocks<br />
exposed at Indian Hollow are believed to be an incomplete<br />
INDIANOLA QUADRANGLE 73<br />
section of Lower Green River, and the pollen data suggest<br />
an age as old as uppermost Paleocene. A Paleocene age sug-<br />
gests the possibility of this belonging to the Flagstaff or at<br />
least being its equivalent, but no other diagnostic fossil or<br />
lithologic evidence supports this conclusion at this location.<br />
Therefore, I have elected to call these sediments Green River<br />
and Flagstaff (?), as indicated in figure 19.<br />
Unnamed Volcanic Rocks<br />
The suite of volcanic rocks north of the Indianola town-<br />
site represents a drastic change in the geologic history of<br />
Utah. Locally, large volumes of explosive volcanics were ush-<br />
ered in during the Oligocene. Centers developed at Bingham,<br />
Tintic, Crystal Peak, Marysvale, Little Cottonwood, and in<br />
the Needle Range. These are generally silicic and inter-<br />
mediate types (rhyolite-andesite-dacite) which were spewed<br />
out of the earth as ash falls, tuff, and latite flows (Hintze<br />
FIGURE 11.-Samples from Green River Formation, pollen photomicrographs.<br />
A.-Pisti~Iipollenite~ mcgngotii, 22.4 microns. B.-P~stillipol~enites mrgn-<br />
gorii, 24.0 microns. C.-Catya sp., 40.0 microns. D.-Taxodium sp., 32.0<br />
microns. E.-Alnus sp., 27.0 microns. F.-Tricolporare pollen, 20.0 mi-<br />
crons. G.-AquilapoIIenites sp., no scale. H.-Pdiastrum sp., 30.0 mi-<br />
crons.
1973, p. 82). In most cases they seem to have filled the val-<br />
leys and drainage systems of the Oligocene topography.<br />
Such is the case with the rocks near Indianola. They are<br />
predominantly andesitic with common occurrences of both si-<br />
licic and mafic types. In this case they definitely filled the ex-<br />
isting drainage systems, but they are not occupying their<br />
original depositional sites. That is to say few if any of these<br />
rocks here are in their primary state. Rather they have been<br />
eroded and carried here by streams (fig. 12). For the most<br />
part they are at least crudely bedded and in some instances<br />
even cross-bedded. Many of the units are very coarse and<br />
contain clasts up to 40 cm in diameter. They are uncon-<br />
solidated and commonly have algal balls mixed in with their<br />
nonsorted matrix.<br />
Hintze (1973) considers these rocks a valuable reference<br />
horizon because they predate Basin and Range block faulting<br />
and postdate folding and thrusting of the bier and Lara-<br />
mide orogenies. In the Little Clear Creek area they also help<br />
to date recurrent movement on the adjacent diapir. They<br />
now stand atop some of the highest topography in that vi-<br />
cinity and form an impressive outcrop. Beneath them are dis-<br />
conformable and angular unconformable contacts with the<br />
Flagstaff, North Horn, and Indianola units.<br />
FIGURE 12.-Stream deposits of Tertiary volcanic conglomerates. Location is<br />
west of Little Clear Creek near the drainage divide.<br />
The source area for these volcanics near Indianola is not<br />
accurately known. Morris (1957) and Hintze (1973, p. 83)<br />
suggest they may have come from the Tintic area. Schoff<br />
(1951), who reports oral communication with A. A. Baker<br />
and states that the volcanics of the Cedar Hills, adjacent to<br />
Indianola, may have come from vents in Strawberry Valley,<br />
goes on to rule this out on the basis of sedimentary texture<br />
and clast size. Khin (1956), who did some petrographic work<br />
on basalt clasts sampled near Little Clear Creek, speculates on<br />
a source area in the Park Citv ,district. All these source lot-1-<br />
ities seem feasible and have merit, but recently discovered hot<br />
water vents northwest of Thistle, Utah, near Wanrhodes<br />
Canyon, shed new light on the subject. After finding one of<br />
these vents, George <strong>Young</strong> invited me into the field to in-<br />
spect a newly unearthed fissure. Were it not for a very re-<br />
cent roadcut, this vent may possibly have been overlooked<br />
since at the surface it cuts the unconsolidated Tibble Forma-<br />
tion which forms an indistinct topography. Also because of<br />
its topographical expression it is noted by George <strong>Young</strong><br />
(1975 pers. comm.) that the entire Wanrhodes Canyon may<br />
be a collapse caldera.<br />
Since the net effective transportation by the streams of<br />
the Oligocene was still east and south, and because this new-<br />
ly recognized area is in relatively close proximity to In-<br />
dianola, I speculate that the "Wanrhodes Canyon Caldera"<br />
offers a good solution for this source enigma. It is also time-<br />
ly to note from my observation that since these vents are so<br />
easily concealed, it is not at all improbable that other<br />
vents could be buried near Little Clear Creek and possibly<br />
have supplied the necessary chemical ingredients for the "sili-<br />
cified oolitic limestone" found in the Flagstaff near there.<br />
Supporting this idea is the fact that the large volcanic boul-<br />
ders have not moved far and may be near their source.<br />
Inasmuch as these rocks were deposited on an old ero-<br />
sional surface in topographic depressions of various types,<br />
their thickness varies from place to place. I estimate a thick-<br />
ness west of Little Clear Creek of 300-450 m. Pinnell (1972,<br />
p. 111) to the north of the study area estimated 45-125 m.<br />
Age dates on these deposits range from Eocene to Mio-<br />
cene, but most workers seem to agree that Oligocene is the<br />
most likely age.<br />
QUATERNARY<br />
Unnamed<br />
Valley fill, alluvial fans, floodplain materials, alluvium,<br />
landslide debris, and colluvium all contribute to the Recent<br />
sediments and the existing topography within the Indianola<br />
quadrangle. Occasional minor accumulations of stream terrace<br />
gravels occur in the low hills around Hjork Creek. Merrill<br />
(1972) reports such gravels in the Mill Fork area and attri-<br />
butes them to stream equilibrium during the prominence of<br />
Lake Bonneville. Pinnell (1972) offers an alternative explana-<br />
tion for the presence of similar gravels in the Thistle quad-<br />
rangle, saying it is due to stream equilibrium recurrently in-<br />
terrupted by rejuvenation from active faults along the<br />
Wasatch front.<br />
Alluvial fans and their subsequent erosional dissection re-<br />
cord recent changes in Utah climatic conditions and contin-<br />
ued uplift of the High Plateaus and Great Basin provinces.<br />
Landslides occur predominantly in canyons along the impres-.<br />
sive front of the faulted Wasatch monocline although some<br />
do occur in conjunction with the salt collapse breccias at the<br />
foot of the plateau's frontal scarp. In any event, all debris<br />
areas were judged to be minor features and to pose no im-<br />
'..
mediate threat to civilization or natural ecosystems. Actually<br />
surface creep seems to be the only presently active phenome-<br />
non. For this reason few debris areas were singled out an-<br />
dmapped except when they displayed a geologic or topo-<br />
graphic significance of some sort.<br />
Since the terrace gravels and volcanics at Bone Yard and<br />
Hill Top are higher than the valley floor, they are probably<br />
older. Schoff (1951, p. 636) suggests they may be assigned as<br />
Quaternary in age because there is a lack of any other evi-<br />
dence, but a Late Tertiary age for the higher-standing vol-<br />
canic outwash should not be ruled out.<br />
SEDIMENTARY TECTONICS<br />
Diapiric tectonism is a phenomenon which seems uniquely<br />
capable of producing unusual and impressive structures.<br />
For example, it is well documented (Halbouty 1967) in the<br />
Gulf Coast region of the United States that subsurface<br />
domes have created tremendous hydrostatic pressures. These<br />
hyper pore-pressures play an important role in the structural<br />
rupture of stratigraphic systems. In Iran (Gera 1972, Kent<br />
1958), where the climate is arid, &It spines have been known<br />
to propagate to the surface and create "salt glaciers" which<br />
produced soil "tills" while being powered by gravity. In the<br />
Paradox Basin salt overhangs have caused beds to overturn<br />
and form hydrocarbon traps in the subsurface. These are only<br />
a few exam~les of manv which could be used to illustrate<br />
I<br />
that diapirism, on a local scale, can create structural relationships<br />
and unconformities that can be confusing unless one<br />
clearly recognizes the mechanism with which he is dealing.<br />
Such is the case in the Indianola area where previous workers<br />
overlooked the exmess Dowers of salt. Within this small<br />
quadrangle, only 156 km', are three impressive piercement<br />
structures. As with most salt domes throughout the world,<br />
they are believed to have formed through a sequence of differential<br />
timing and pulsing rates of ascension which have<br />
created local inter- and intraformational unconformities, faulting,<br />
folding, and bed overturning. Collapse and cap-rock<br />
FIGURE 13.-Low oblique aerial view from south of the collapsed N. San<br />
Pitch River d~apir.<br />
INDIANOLA QUADRANGLE 75<br />
brecciation located atop these features have also played a key<br />
role in their evolution. This "roof caving" action was prob-<br />
ably brought about as spines attached to the master domes<br />
encounterid open-system; ground-water aquifers. The evapo-<br />
rites were taken into solution by the water and removed<br />
from the immediate area. This section of removal and col-<br />
lapsing, however, probably did not play an important role<br />
until the later stages of upwelling which has produced the<br />
present structure and topography (figs. 4, 13, 14, and 15).<br />
Another point of interest associated with the removal of<br />
these evaporites is that during Recent times this area has<br />
comprised part of the Great Salt Lake drainage system. Many<br />
ideas have been promoted about the origin of evaporites for<br />
the lake, but I believe that the Jurassic salt from the Arapien<br />
Formation of central Utah provides a most credible explana-<br />
tion for a rich source of gypsum and halite.<br />
The domes in the Indianola area fall under the classifica-<br />
tion of halokinesis as described by Halbouty (1967, p. 2). In<br />
general this means that the initiation of growth resulted<br />
from variations of overburden and isostatic physics which<br />
equalize the pressures between materials of two different spe-<br />
FIGURE 14.-Circular depression on left is the collapsed diapir. The diced patrern<br />
marks location of faults in N. San Pitch River Valley. In thc<br />
background is the fronral scarp of the Wasarch Plateau.<br />
FIGURE 15.-Background is Wasatch Range and Cedar Hills. Middleground is<br />
lndianola townsite and cuestas of Green River-North Horn rocks.<br />
Foreground is western edge of the collapsed diapir.
cific gravities. In this case the Arapien is believed to be the<br />
mother salt. As in other areas along the Colorado Plateau<br />
(Stokes 1956b, p. 46), accumulations of salt were most likely<br />
amassed by tectonic folding, critical overburden, basement<br />
faulting, and/or locally increased geothermal gradients. Don-<br />
ald Kupfer (1975) notes that temperature is one of the most<br />
im~ortant factors involvine salt dome movement. He also<br />
0<br />
provides a good explanation of purification that results from<br />
ascension and crystal strain hardening, which aid in the me-<br />
chanics of domal growth. These processes seem to be impor-<br />
tant since the Arapien is not known for its massive purity of<br />
evaporites. Whatever the mechanism for initiation of evapo-<br />
rite massine. it is a well-known fact that densitv differences<br />
0'<br />
alone are able to maintain an active state of diapir growth<br />
for a very long period of time.<br />
Salt often forms valleys, both regionally, as those under-<br />
lying the bolsons of West Texas, and locally, such as some<br />
of the entrenched river valleys in the Paradox Basin (Stokes<br />
1956b, p. 44). This model holds true for the North San<br />
Pitch River Valley diapir north of Milburn in the study<br />
quadrangle, but not for Hjork Creek dome or Little Clear<br />
Creek piercement because these two are at the core of highs<br />
both structurally and topographically.<br />
The Little Clear Creek diapir is similar to the ones in the<br />
Paradox Basin (Stokes 1956b, p. 46) in that it outcrops as a<br />
linear feature (fig. 19) instead of as a dome. This peculiarity<br />
is probably due to an obscure intimate relationship with the<br />
Little Clear Creek fault. The overturning of the Price River<br />
and South Flat on the east wall of the canyon is probably<br />
due, firstly, to the asymmetric ascension of the diapir and,<br />
secondly, to accentuation by subsequent collapse.<br />
The Hjork Creek piercement is actually an elongated<br />
dome rather than a circular one and is illustrated on the<br />
formline contour map (fig. 7) as a plunging anticline. The<br />
exposed stratigraphy surrounding this immediate area clearly<br />
demonstrates numerous local angular unconformities which<br />
are the basis for explaining various episodes of upwelling.<br />
All three of the diapirs in the study area are believed to<br />
be separate distinct master domes each acting independently<br />
of the others, thus revealing their evolutions and personal-<br />
ities as different topographic expressions. Their relations to<br />
and interactions with thick Rocky Mountain geosynclinal<br />
sediments, Laramide folds, Wasatch monocline, and Basin-<br />
Range faults are extremely complex and are best described by<br />
the sequence of cross-sections in figure 16.<br />
An apparent problem with these diapirs is that they do<br />
not show up as strong negative anomalies on gravity maps<br />
compiled by the exploration efforts of an oil company. One<br />
explanation for this could be found in the concept of solu-<br />
tion, removal of the low-density material, and collapse, which<br />
has previously been discussed. However, the most likely rea-<br />
son they did not show up strongly is that the gravity survey<br />
was too regional to indicate such small local anomalies. Thus<br />
it is felt that a proper scale of investigation relative to the<br />
size of the diapirs would show intense gravity lows.<br />
STRUCTURE<br />
Faults<br />
Analysis of faulting was undertaken by standard methods<br />
using stream patterns (figure 17), field tracing of breccias,<br />
springs, and stratigraphy. Aerial photos, both conventional<br />
and low oblique late afternoon shadows, were also used.<br />
More sophisticated techniques, employing imagery analysis of<br />
Skylab 111 and ERTS photos and vibroseismic data, proved to<br />
be extremely interesting but were actually of limited help. By<br />
density slicing of the space photography, we attempted to<br />
produce a linear-trend overlay, making identification of faults,<br />
joints, and stratigraphy, but we were limited by nondescript<br />
geomorphology and vegetation. However, this method did<br />
demonstrate some interesting results and holds great poten-<br />
tial for mapping and structural analysis from aerial photos,<br />
especially those from space, owing to their excellent band-<br />
width control.<br />
Most of the faults in the study quadrangle fall in a nor-<br />
mal-fault category. However, diapirism has allowed for some<br />
very unusual relationships and timing which is often difficult<br />
to pin down.<br />
FIGURE 16.-Crosssectional evolution of the lndianola area. Refer to figure<br />
19 for stratigraphic abbreviations. (1) Section width (approximately<br />
120.7 km) across the Rocky Mountain geosyncline. Deposition through<br />
Cretaceous times near the eastern center of the downbuckling geocline.<br />
(2) Crosssection width (approximately 9.7 km) across the Indianola<br />
quadrangle (figures 2-7). Folding and subsequent deposition of Price<br />
River conglomerates ending the Sevier orogeny and beginning the Lara-<br />
mide orogeny. Deposition through Price River times. (3) End of Lara-<br />
mide orogeny. Intermittent diapiric axensLon. Deposition through<br />
North Horn times. (4) Diapiric growth and subsequent faulting. Depo-<br />
sition through Green River times. (5) Diapiric piercement at Little<br />
Clear Creek. Deposition through Tertiary volcanic times. (6) Collapse<br />
of diapir tops. Basin-Range faulting and subsequent overturning of<br />
South Flat and Price River rocks. (7) Uplift of Wasatch Plateau and<br />
present-day position of geology.
FIGURF 17 -Stream pattern analysts St~ppled ace?\ denote areac of controlled drainage<br />
INDlANOLA QUADRANGLE 77
The NNE fault, which runs east of the Ind~anola town- within the study area. those associated w~th d~apirism and<br />
site and divides the valley from the cuestas of Green River the large monoclinal flexure which forms the structural and<br />
and North Horn rocks. IS readilv notlced as one studies a topographic front of the Wasatch Plateau<br />
topographic map of the area. It has been speculated to be a Topographically the Wasatch monocline IS one of the<br />
Jurassic-age fault, a possible extension of the "anc~ent Eph- most lmpresslve features of the central Utah area. It was<br />
raim Fault" (Moulton 1975). Jurass~c age is only conjecture probably formed during the Late Eocene (Eardley 1963), but<br />
at th~s point because there is d~fficulcy physically traclng the ~ts tlming is difficult to pln down prec~sely. Spieker (1949b)<br />
fault in the field Had this problem not been suggested ver- reports that at one time the plateau was covered with Green<br />
bally to me, the age of faultlng would be assigned to post- River sediments and that they have slnce been stripped by<br />
Oligocene, the beginning of the Basin-Range taphrogeny. In- eroslon I feel that the monocline was a positive feature durdeed,<br />
even if it were in~tiated in the Jurassic, it does seem to lng deposit~on of the (Ollgo-M~ocene)) volcanics whlch were<br />
evidence significant Miocene movement. Although it is not deposited by streams parallel to the fold axls The reallzat~on<br />
connected on the attached map (fig. 19), th~s fault may con- of these facts leads me to conclude that foldlng began In<br />
tinue to the NE up Llttle Clear Creek and ultimately control Late Eocene and continued Into Early Oligocene tlmes.<br />
this faulted canyon at depth.<br />
The serles of two anticlines and two syncllnes whlch<br />
It is easy to envision that depos~tional control caused by seems to align in a rough en echelon pattern and plunge to<br />
a fault scarp in this posit~on during the deposition of the Ju- the SW, represents a complex Interaction between the diarasslc<br />
evaporltes prov~ded a plausible mechanism for the Iln- plrlc ascensions and possible folding durlng the Laramide<br />
ear d~ap~r whlch paralleled Little Clear Creek Canyon and epeirogeny Therefore, the~r tlmlng most l~kely ranges from<br />
subsequently overturned the Price River and South Flat latest Jurassic untll Recent times with the strongest Interstrata.<br />
Th~s is one of the criter~a for suggesting a Jurassic rift<br />
basin.<br />
The next oldest fault In the quadrangle is the curvlng<br />
mltten; action in Late Cretaceous-Early Tert~ary<br />
N-S fault which parallels and controls the base of the<br />
Wasatch Plateau. 1t' IS thought to have been lnit~ated during<br />
the Late Eocene at the incept~on of the Wasatch monoclinal<br />
flexure. Most likely th~s normal fault was a tens~onal fracture<br />
at the hlnee of the fold and ~rov~ded a zone of weakness for<br />
0<br />
the greater d~splacement whlch began to occur durlng the<br />
M~ocene. The fault is still actlve and is powered by the<br />
forces which are exhumlng the Colorado Plateau. It, too,<br />
may have prov~ded primary structural control for ascenslon of<br />
the c~rcular North San Pitch Rlver d~ap~r.<br />
The faultme d~rectlv associated w~th the Dlercements. es-<br />
0<br />
pecially the drag faults, are best explained by reference to the<br />
map and cross-sections (fig 19, A-A', B-B'). The movement<br />
probably began In Cretaceous tune and ranged to the present,<br />
with d~fferential movement dependent on ascension and<br />
collapse of the dlaplrs.<br />
The ~llustrated curved faults east of, and adjacent to,<br />
Blackhawk hogback are surface features produced by slump-<br />
TECTONIC HISTORY<br />
The tectonlc evolut~on of th~s central Utah area (fig. 16)<br />
has been a complex interplay of the Cord~lleran mlogeosyncline,<br />
the Nevadan orogeny, the Sev~er orogeny, the Rocky<br />
Mountaln geocllne, the Laram~de orogeny, the Flagstaff and<br />
Green River lakes, Tert~ary volcan~c eruptions, the Wasatch<br />
monocl~ne, Basln and Range taphrogeny, Recent reg~onal uplift<br />
and dlssectlon, and finally sporad~c, interm~ttent ascension<br />
and collapse of diaplrs<br />
This is a most impress~ve list of histor~c events, and it 1s<br />
certainly an understatement to mentlon that ~t is no wonder<br />
that the geology of the Indranola quadrangle has been mlsunderstood<br />
for a long per~od of tlme<br />
The following list IS intended to be a conclse, generalized<br />
chronologic outline of events which have dlrectly affected the<br />
surficial geology<br />
1. Paleozoic depos~t~on of Cordilleran m~ogeocl~nal sedllng<br />
and gravity sliding of the Flagstaff and Green River<br />
rocks on thin shale beds Relative horizontal translat~on IS at<br />
most a few hundred meters<br />
2<br />
ments. (Eo-Cambrian-Permian)<br />
Nevadan orogeny Uurass~c), producing the arch of<br />
the Sev~er geant~cline and reg~onal drainage shifts.<br />
The only other major fault 1s the ENE-trend~ng normal 3. Sevier orogeny (Cretaceous) caused by strong comfault<br />
whlch runs through the Indianola townslte. I first dis-<br />
pressive forces that produced a major thrust belt<br />
covered it whlle traclng the occurrence of numerous effluent stretching from southern Nevada to Idaho.<br />
warm sprlngs It also shows up on seism~c section and proves<br />
to d~splace the basement by several thousand meters (fig. 19,<br />
C-C').<br />
The rest of the small normal faults on the map are rel~ef<br />
adjustments to the block-faultlng patterns of the eastern<br />
Great Basln<br />
4. Rocky Mountain geosyncline (M<br />
Cretaceous-Paleocene), an asymmetric foredeep that<br />
collected a class~c "~nverted" strat~graphy shed from<br />
the frontal h~ghlands of the d~sturbed belt These extremely<br />
thlck (4,500 m) sed~ments could have been<br />
the necessary cr~tlcal overburden for lnltlatlon of d~aplrs<br />
Jo~n ts<br />
5 Laram~de epelrogeny (L. Cretaceous-Paleocene) caused<br />
The only surface jolnts of any slgnlficance are the two<br />
pervasive sets that affect the 1ndianola'-Price R~ver' rocks at<br />
the head of Hjork Creek. One set trends E-W and the other<br />
trends NNW-SSE. They were probably caused by the straln<br />
of standlng these massive conglomerates on end durrng the<br />
final stages of ascension of the Hjork Creek diap~r.<br />
by vertical upl~fts that produced local gravlty slidlng<br />
It produced the folding and unconform~ty that are<br />
rep;esented at the base of the Prlce ~ ~ v econ- r<br />
glomerates Th~s actlon may have a~ded the ascenslon<br />
of early d~ap~r~c movement<br />
6 Flagstaff Lake (Paleocene), really a unidlrect~onal<br />
transltlon of the fluv~al and lacustrlne deposits of the<br />
North Horn formarlon. The fluv~al clast~cs of the<br />
Folds<br />
North Horn (Cretaceous-Paleocene) probably repre-<br />
There are two s~gn~ficantly d~fferent types of folding<br />
srnt the dylng phases of the Laramide orogeny. Lake
Flagstaff may not have been one large body of water<br />
but rather a series of intermountain lakes.<br />
7. Green River Lake (Eocene), in this area the southern<br />
extension of ancient Uinta Lake. In this part of cen-<br />
tral Utah its nearness to highlands accounts for the<br />
abundance and coarseness of conglomerat~c units.<br />
8. Wasatch monocline (L. Eocene-E. Oligocene), a flex-<br />
ure that was post-Green River times and must have<br />
been a reaction between the evolving Great Basin<br />
and present "cratonal edge."<br />
9. Tertiary volcanics (Oligocene-Miocene) ignimbrites,<br />
andesites, and basalts, in this area all reworked and<br />
deposited by streams.<br />
10. Basin Range taphrogeny (M~ocene-Recent), fault<br />
blocks being tilted and uplifted by reg~onally ten-<br />
s~oned plate tectonlc forces.<br />
11. Recent regional uplift, a continuation of forces that<br />
created the Basin-Range features and entrenchment<br />
of the plateaus.<br />
12. Diapiric action (Jurassic?-Recent), interm~ttent reac-<br />
tlons caused by sedlment overloads, faulting, fold~ng,<br />
and reg~onal uplifting. The final stages of devel-<br />
opment have been affected by collapse due to having<br />
their tops removed by ground-water solution. These<br />
solubles have probably been a source for at least<br />
some of the Great Salt Lake evaporites.<br />
INDIANOLA QUADRANGLE 79<br />
are excellent. This is simply ~llustrated by figure 18, which<br />
demonstrates a model that reportedly can be seen in the Gulf<br />
Coast salt domes in Louisiana. The model has been proposed<br />
by Donald Kupfer (1975 pers. comm.) and was derlved from<br />
his studies of salt mlnes and seismic data in that part of the<br />
country. The uplifted dome or anticline beneath the diapir is<br />
created by isostatic adjustment due to the rise of low density<br />
eva~orites.<br />
1<br />
The subsurface stratigraphy beneath the Arap~en in this<br />
part of central Utah consists of Paleozo~c miogeosynclinal<br />
sediments of the Cordilleran and Mesozoic eol~an and fluvia-<br />
tile deposits These rocks provide a target for hydrocarbon<br />
source beds and reservoirs. Several formations could act as ei-<br />
ther, but the Jurassic Navajo should offer exceptional reser-<br />
volr qual~ties. Also the close proximity of warm springs near<br />
the Indianola townslre suggests a good temperature reglme<br />
for maturation and migrat~on of hydrocarbons<br />
It IS noteworthy to rnentlon that in addition to isostatic<br />
uplift beneath the diapiric ascension, Laramide tectonics may<br />
have aided the format~on of an amenable reservoir trap.<br />
For these general reasons I suggest that the Ind~anola antlcline<br />
is an excellent wildcat target.<br />
OVERVIEW<br />
The global plate tectonlc model is far from perfect to<br />
date, but it is an excellent working hypothes~s whlch functions<br />
well enough so that the burden of proof has been shed<br />
to the disbel~ever Its employment often generates new ideas,<br />
ECONOMIC GEOLOGY<br />
some good, some not so good, but ~t is important to pro-<br />
The area within the study quadrangle offers s~gnificant mote and develop these ideas so that the model can be execonomic<br />
potent~al in several categories With the exception panded and tested. I do not pretend that the small area of<br />
of gravel products, most of the resources could be developed the study quadrangle will provide vast expansion of the modwithout<br />
serious Impact on the present surface uses of farm- el or even that the presented observations will make a good<br />
ing and ranch~ng. Road gravel has already been stripped from fit to the model, but some thoughts which surfaced during<br />
some small foothills composed mostly of Tertiary alluv~um. this project do seem worth d~scussion.<br />
These depos~ts still offer limited quantities of gravel<br />
It was mentioned previously that the linear diap~r that<br />
Noncommerc~al quantities of peat have been surface- controls Little Clear Creek may have initially been a simple<br />
mined by local farmers. Peat-supplying units lie adjacent to salt deposit against a fault scarp in a restr~cted basin. Th~s IS<br />
Parley's Canyon and other canyons east of the Milburn a common mode of origin which oftentimes accompanies r~ft<br />
townslte and are contalned in the Cretaceous North Horn baslns. The Paradox Basln of southern Utah is an aborted<br />
Format~on The~r extent has not been thoroughly In- rift basin, and speculation suggests that the age of control<br />
vest~gated<br />
Bitter hallnes may be present in undetermined quantltles<br />
near Hjork Creek and Little Clear Creek diapirs. The success<br />
of Croton's mlne IS not reported, but supposedly ~ts Inceptlon<br />
was to retrieve sylvlte.<br />
When more IS learned about the relative stability of salt<br />
domes, those within the study area could possibly be used<br />
for underground storage of hydrocarbons or even radioactive<br />
waste. Th~s is a sensitive subject when one considers envlronmental<br />
and safety precautions There are many unknown var-<br />
~ables, but once these uncertainties are understood, the<br />
domes In this reglon could be considered for such storage facilitles<br />
Perhaps the greatest economlc potential withln the area<br />
lies beneath the salt domes In structural 011 and gas reservolrs.<br />
Walton (1974 pers. comm.) feels that the Clear Creek<br />
gas field may be a salt-controlled structure. Chr~st~ansen<br />
(1963) has for years recognized the powers of evaporite diaplrs<br />
In this area of Utah. Also noncommercial shows from<br />
mult~pay zones have been reported from the Paleozo~c rocks<br />
a Navajo<br />
Reservo~r<br />
3<br />
mother salt<br />
beneath the Wasatch Plateau several kilometers south of Ind~anola<br />
by Phlll~ps Petroleum Company. Well-control data IS<br />
extremely sparse in this region, but I belleve that cond~tions<br />
for maturation and mlgratlon of commerc~al hydrocarbons<br />
FIGLJR~ 18 -Schemat~c dlagram represenrlng the ascension of Hlork Creek dldplr<br />
The strucrure bcnearh the d~ap~r 1s creared bv lsosratlc rebound<br />
benearh rhe low.denslrY evaporlres The Navajo Sandsrone In rh~s pos1rlon<br />
makes an excellent target for a hydrocarbon reservoir
80 D M RUNYON<br />
posslbly is related to the salt deposlts of North Sanpete Val-<br />
ley. Is it coo far afield to suggest that the restricted Jurassic<br />
sea which occupied the vicin~ty of central Utah was an an-<br />
cient rift system? Could the present-day cratonal edge which<br />
underlies the Wasatch monocline (Schuey 1973, and Kenneth<br />
Cook 1973 pers comm.) be related to such an ancient sys-<br />
tem, or is it more closely associated with the Great Basln rlft<br />
which IS presently developing?<br />
The Laramide orogeny is another subject for speculat~on.<br />
Richard Wing (1975 pers. comm.) has recreated an inter-<br />
estlng cross-section across the Rocky Mountain geosyncline<br />
that shows a sequence of half-grabens with the down-dropped<br />
edge to a central "downbuckling" axis. This shows orogenic<br />
clastics shed from upthrusts durlng the Laramide orogeny to<br />
have been deposited in a reg~onal topographic low whlch<br />
may have been a plate attempt at subduction that failed for<br />
some reason. This topographic depression helps one to VIS-<br />
ualize the large basins necessary for North Horn, Flagstaff,<br />
and Uinta lake deposlts.<br />
The Sevier orogeny 1s one that supports an idea pro-<br />
moted by Hays and Pitman (1973) that the rapid worldwide<br />
spreading during the Cretaceous was accompanied by an ele-<br />
vation at the mldocean spreading center which created a vol-<br />
umetrlc reduction of the ocean basin and forced the seas<br />
onto the contlnents. This event then forced the final marine<br />
invas~on of central Utah. However, 30 million years 1s a long<br />
time without any marine transgressions. I think thls is one<br />
Indication that the contlnents are getting thlcker and riding<br />
higher on their respective plates.<br />
New questlons now anse. Was the Sevier thrusting due<br />
to this rapid spreading rate? Was the Cretaceous volcan~city<br />
record of another aborted subduction attempt? Is it colnci-<br />
dence that the termination of salt dlaplrs and Wasatch monocllne<br />
w~thln Indianola area lie at a triple intersection of the<br />
Great Basin, the Colorado Plateau, and the Central Rockies<br />
(composed of the anomalously thick Oqulrrh Basin sediments)?<br />
All these questlons and others which wlll arlse dur-<br />
ing the develop men^ of global geologlc hlstory present a tre-<br />
mendous challenge. I wish to express that thls challenge and<br />
the stratigraphy, structure, and tectonlc hlstory of the In-<br />
dianola quadrangle well represent class~c geologic principles<br />
It is an area that still demonstrates a promlse of revelation<br />
for the future and one that has been an excellent proving<br />
ground for students of the earth.<br />
APPENDIX<br />
Arap~en Formarlon<br />
Section tape-measured In Eabr Lake Fork, stream cur rrendlng ESE In sec-<br />
rlon 7, T 11 S, R 5 E<br />
Pnce R~ver Formarlon Faulr Contact<br />
7 Mostly so11 and vegetation covered Sandsrone, unl-<br />
form. I*, weakly bedded, mlnor shale<br />
streaks, g r a y ~ ~ n<br />
6 Mostly so11 covered Shale, l~ght grew-gny, forms<br />
dark so11 In places, hlnrs of gypsum Thln Interbeds<br />
of buff silty llmesrone<br />
5 Sandsrone, golden-brown, Ilmy, fa~r sorrlng, rned~um<br />
gralned<br />
Thickness<br />
Meters<br />
4 Mostly w11l covered Shale, glny 11 9<br />
3 Sandstone, rned~um gralned, red-bruu..w~th sparse.<br />
thln (2-15 cm) Ilrny bu!f -&, ox~llar~on r~pple<br />
marks, and d~~onrlnuous shale lenses<br />
2 Mostly covered Shale,<br />
- - .--<br />
I Sandstone, very fine gralned, wh~te, l~ght gray, quartz<br />
- -<br />
Weathers to bulbous ledges<br />
Faulr contact<br />
South Plat Formation<br />
Twlst Gulch Formarlon<br />
Total<br />
Section measured on traverse trendlng N55W in NW corner sectlon 18,<br />
T 11 S, R 5 E The outcrop 1s well exposed on stream cut and rrends N 50<br />
E 65 NW<br />
Unir<br />
No<br />
North Horn Formation<br />
Alluv~um-fault contact<br />
18 Sandstone, fine grarned, fair to good sorting, mosrly<br />
quartz w~th mlnor feldspars and rraces of dark heavy<br />
mlnerals and chert, subangular-subrounded,<br />
hex~~te stalG% whlch y~elds a red hue, fractunng<br />
healed w~rh calc~te, thlnly bedded w~h mlnor weak<br />
cross-beddlng, basal sand, lnterbedded w~rh thln<br />
maroon. I~ght green-gpx s~lty ghaks and sands whlch<br />
occur as a d~stinct cycl~c sequence<br />
17 Sandsrone s~rnllar to 18, cycllc sequence w~rh bulbous<br />
wearherlng basal sand<br />
16 Sandsrone slmllar to 18 only cycles more even In<br />
thrckness and spacing, m ~xlts and shales, h~ghly<br />
calcareous, basal sand approx 1 5 rn th~ck<br />
demonstntlng good graded beddlng, yhl~ s p d h i<br />
appearance derived from lrnbncare aligned feldspars<br />
altered to kaollnlte<br />
15 Slmllar ro unit 16, lenslng of wh~te speckled frag<br />
rnents (2 5-10 cm thick lenses) in the basal sand<br />
(fine-med~um), shale thln, cnnkled, dark red-brown<br />
14 Sandstone, cycllc unlt, white specks change ro crossbedded<br />
structures In the 2-m-thlck basal sand, unlts<br />
above base fine upward thln and lnterbed w~rh<br />
lam~nared shale and sllrs approx 1-2 m rh~ck<br />
13 Slm~lar ro unlr 14 Basal sand approx 2 5 m thlck<br />
and crossbedded, color changed from maroon to xd-<br />
cue, shales In upper part of unlr wearhered to a<br />
morrled appearance<br />
12 Less dlstlncrly cycllc although gram slze and color<br />
srmllar ro above, righr green.Rray calcareous unlts<br />
abundanr, lnterbedded w~rh &shah, basal sand<br />
mlsslng, glven way to evenly bedded masslve sands<br />
approx 6- 9 m rh~ck<br />
11 Shale, gre-r>.tnaL(l:)n, var~egated w~th a)me<br />
bulbous-ledge-forming lnrerbedded sandy unlrs<br />
approx 1 2 m rh~ck<br />
10 Sandsrone, massive bulbous, red.orange, quarrzose<br />
9 Shale, thin paper shales, llghr gray wtth mlnor fine<br />
sands approx 5-10 cm rh~ck, more prorn~nent at rhe<br />
base of the sectlon<br />
8 Sandsrone, very coarse to gnt, Immature, abundant<br />
calclte, some kaollnlte, very colorful rnatnx approx<br />
50% of whrch 1s subangular quartz and abundanr<br />
feldspars<br />
7 Shale, d& maroon, cnnkled, w~rh lnrerbedded gray<br />
silty calcareous units approx 2lh cm rh~ck<br />
6 Slit and fine sand, weathers fiss~le, r d evenly bedded.<br />
calcareous at base<br />
5 Shale, rd, some slit<br />
4 Sllr and fine sand, &mmosrIed, weathers In a ch~ppy,<br />
fine slabby nature, Interbedded red crlnkled shales<br />
Thckness<br />
Meters
INDIANOLA QUADRANGLE<br />
3 Covered, so11 22 3 4 So11 and vegetatron cover<br />
2 Cyclrc sequence of dark4 crinkled shale and sllts 15.6<br />
wrth minor l i ~ h ~ fine-medium d , well-sorted sands;<br />
basal sand medrum grained, r h n g e approx 46 cm<br />
thrck<br />
1 Shale, rgb 4 6<br />
Fault<br />
South Flat Formarlon<br />
1ndranola'-Pnce Rlver Formation,<br />
Sectron tapemeasured on a traverse trendrng N40W in NW sectlon cor-<br />
ner, sectlon 22, T 11 S, R 4 E<br />
North Hom Format~on<br />
Unconformable contact<br />
3 Poorly exposed, conglomerate, coarse, openwork with<br />
thrck lnterbeds (approx 6 m) of clay and algal balls,<br />
sandstone, b&, lrmy w~th occasronal lensatic shales<br />
2 Mostly covered; sandstone, red-orange, medrum to<br />
coarse grained wrth mlnor conglomerate (Ilmestone<br />
clasts) lenses and algal ball units<br />
Total 231 2 1 Sandstone, red-oranee. very calcareous, farr to poorly<br />
sorted; lnterbedded red silty shale approx 4 5 m<br />
thrck, kbandrng common-.near contact of Pnce<br />
Fllrcks<br />
Thickness<br />
Meters<br />
1 Conglomerate, massrve, coarse, weathers to bulbous 237 5<br />
pinnacles, color domrnantly gray to buff.mxh,mor<br />
red-orange surface_st_a"_in~, outcrop heavrly fractured<br />
w~th two major jornt sets, one trendrng N47W and<br />
the other N87E; clast cornposrtron (slzes up to 6 m<br />
&a ) domrnantly quartzrte wrth abundant sandstone<br />
clasts, most sandstone clasts have lrescgang banding,<br />
matnx gntty and poorly sorted suggesting a possrble<br />
source from the Twrst Gulch Formation, outcrop<br />
wrth promlnenr channeling near the base of the<br />
sectlon, sorne demonstrating a high degree of<br />
rmbncatron -<br />
11 Sandstone, poorly exposed, medrum to coarse grarned,<br />
poor to farr sortrng, occasronal thln algal-bal! beds,<br />
balls average 5-15 mm drameter, sorne clay galls<br />
~ncorporated, no fossils rn algal balls; alternating red-<br />
orange ro lreht buff on weathered surface<br />
10 Mostly so11 covered, sandstone slope wash<br />
9 S~mrlar to above, but slope wash arange and grrtty,<br />
some mrnor rnterbedded red shales at base approx 3<br />
m thrck<br />
8 Sandstone, calcareous, very coarse, grrtty, poorly sorted,<br />
I&h,gray, small conglomerate lenses w~th l~mestone<br />
clasts, sandstones occasionally mottled, changrng<br />
downward to sandy l~mestones wrth mrnor occurrence<br />
of algal balls<br />
7 Mostly x ~ covered, l sandstone, weathers bulbous,<br />
very calcareous, med~um-coarse gralned, oEn&m<br />
b_uff_yrlnr<br />
6 Sandstone, quartzose, ]&ray, fine-medrum gralned,<br />
good x>rtlng wrth dark chert fragments and sparse<br />
lrmesrone<br />
5 Mostly x>ll, vegeratron covered, sandstone, grltry,<br />
cross-bedded, lenslng of fine conglomerate and clay<br />
gall beds, red-oranee, top 9 m of secrlon gradlng<br />
downward Into fa~rly well-sorted calcareous sand, l~ght<br />
gray w~th mlnot rhln orang.l~m~uu~s, total sectlon<br />
laterally vanable, contalnlng some unexposed<br />
Interbedded red shales<br />
Unconformrty'<br />
Pnce Rlver Format~on<br />
Total<br />
Flagstaff Formation<br />
Sectron tape-measured In section 6, T 11 S, R 5 E on a line trendrng<br />
NW-SE.<br />
Green R~ver Format~on<br />
7 Mostly covered, shale, dark gray wrth thrn lenses of<br />
very l~ght buff chlppy weatherlng llmestone<br />
6 Limestone, l~ght brown, med~um dens~ty, thin lenses<br />
(15-45 cm), very dense nl~ceous fossrl~ferous<br />
Irmestone<br />
5 hmestone, fossll~ferous hash, gray, weatherlng chalky<br />
lrght gray-brown into small blocky chrps<br />
Thckness<br />
Meters<br />
Total 237 5 4 Shale, gray on weathered surface, dark gray brown on<br />
Unconformrty<br />
fresh broken surface,<br />
Ind~anola Group 3 Shale, gray brown, thrnly even bedded, weathering<br />
ch~ppy, rnterbedded w~th thln sandy llmestone lenses<br />
10.8<br />
North Horn Format~on<br />
Sect~on rape-measured rn secrrons 29 and 30, T 11 S, R 5 E on a lrne<br />
trendrng N40W from the SW comer of sectlon 29 to the SW comer of section<br />
30<br />
Un~t<br />
Tkckness<br />
2 Limestone, wh~te, chalky wlth some ash,, wnrherrng<br />
fissrle, medrum dens~ry, contarnrng fresh-water<br />
gastropods<br />
1 Mostly so11 covered, shale, gray<br />
3.3<br />
149<br />
No<br />
Meters<br />
Total 68 1<br />
Flagstaff Formatron'<br />
North Horn Formatron<br />
REFERENCES CITED<br />
Armstrong, R L, 1968, Sevrer orogenrc belt rn Nevada and Utah Geol Soc<br />
Amer Bull., v 79, p 429-58<br />
Atwater, T, 1970, lmpl~car~ons of plate rectonlcs for the Cenozo~c tectonic<br />
evolut~on of western North Amer~ca Geol Soc Amer Bull, v 81, p<br />
3513-36<br />
Baer, J. L., 1969, Paleoecology of the cyclrc sed~ments of the lower Green<br />
Rlver Formarlon, central Utah Brlgham <strong>Young</strong> Unlv Geol St, v 16,<br />
pr 1, p 3-95<br />
Baker, A A, Dane, C H , and Reesrde, J B, Jr., 1936, Correlar~on of the<br />
Jurassrc format~ons of parts of Utah, Arlzona, New Mex~co, and Colorado<br />
US Geol Surv Prof Paper 183<br />
Brssell. H J, 1952, Strar~graphy and structure of northeast Strawberry Valley<br />
quadrangle, Utah Amer Assoc Petrol Geol Bull, v 36, p 575-634<br />
Bradley, W H. 1930, The varves and clrmate of the Green Rrver epoch<br />
U S Geol Surv Prof Paper 158, p 87-110<br />
Burchfiel, B C, and Dav~s, G A, 1972, Structural framework and evolur~on<br />
of the southern part of the cordilleran orogen, western Unrted States<br />
Amer Jour SCI, v 272, p 97-118<br />
Burchfiel, B C, and Hlckcox, C W , 1972. Structural development of central<br />
Utah Utah Geol Assoc Pub1 2, p 55-66<br />
Burger, J A. 1963, The Cretaceous system of Utah Utah Geol and Mrneralog<br />
Sum, Bull 54. p. 123-40<br />
Buss. W R. 1963. The physrography of Utah Utah Geol and Mrneralog<br />
Surv, Bull 54, p 13-18<br />
Chnstransen, F W, 1963, 011 and gas possrbrlrt~es of the tnnsrtron zone In<br />
central Utah Utah Geol and Mlneralog Surv, Bull 54, p 237-338<br />
Clark. F R. 1914, Coal near Wales, Sanpere County, Utah US Geol Surv ,<br />
Bull 541, p 478-89
84 T. C. ANDERSON<br />
tain block, but did not recognize its effect on the landforms<br />
except in wineglass canyons (Davis 1925). However, in a la-<br />
ter paper (Davis 1938), he discussed recurrent uplift of pedi-<br />
ment surfaces and concluded that uplift is continuous rather<br />
than recurrent since "benched faces" are not observed. Never-<br />
theless, his work remains as the most significant geomorphic<br />
study of the Wasatch Range for several decades.<br />
General <strong>Geology</strong><br />
In addition to some of those mentioned above, several<br />
general studies were made previously for portions of the<br />
study area. The Traverse Mountains were studied by Marsell<br />
(1931) and Bullock (1958). The main mass of the Wasatch<br />
Range was examined by Calkins and Butler (1943); and Ba-<br />
ker (1959) described fault patterns near Provo. Eardley (1934)<br />
WEST<br />
MTN<br />
A LONE PEAK<br />
A MAHOGANY MTN @<br />
A PROVO PEAK<br />
\MAPLE FLAT<br />
a LOAFER M TN<br />
FIGURE 1.-Index map to study area and places named in text.<br />
ETHER PEAK<br />
studied the structure and physiography of the Wasatch<br />
Range adjacent to Juab Valley and later (Eardley 1939) pre-<br />
sented a synthesis of structural development of most of the<br />
range. Descriptive guides were authored by Rigby (1962,<br />
1968) and Rigby and Hintze (1968). Environmental geology<br />
was well discussed on a preliminary basis by several papers in<br />
Hilpurt (1971).<br />
A number of master's theses have considered various seg-<br />
ments of the area in terms of general geology or structure.<br />
Harris (1936) interpreted the structure of Rock Canyon;<br />
Gwynn (1948) studied Slate Canyon, and Mecham (1948)<br />
mapped Little Rock Canyon near Springville. Gaines (1950)<br />
studied the area from Provo Canyon to Rock Canyon, and<br />
the mouth of Spanish Fork Canyon was studied by Hodgson<br />
(1951). Perkins (1955) described the lower American Fork<br />
Canyon area, the Baldy area was discussed by Olsen (1955),<br />
and Rhodes (1955) dealt with the Buckley Mountain area.<br />
Peterson (1956) srudied Loafer Mountain and Payson Canyon<br />
areas, and the Lehi quadrangle was mapped and described by<br />
Bullock (1958).<br />
Several geologic maps are available in addition to and<br />
partly based upon the aforementioned thesis maps. Baer<br />
(1964, 1972, 1973) and Baker and Crittenden (1961) covered<br />
most of the area in quadrangle maps, and Hintze (1969b)<br />
mapped the area just east of Provo. All these maps show<br />
Wasatch Fault traces, step faults, and antithetic faults related<br />
to the svstem.<br />
Peculiar features and geology of Lake Bonneville were<br />
first described by Gilbert (1890) and were later discussed and<br />
mapped in detail by Hunt, Varnes, and Thomas (1954) for<br />
northern Utah Valley, and by Bissell (1963) for southern<br />
Utah Vallev.<br />
<strong>Studies</strong> of certain other areas either adjoining or with a<br />
similar history elsewhere have provided clues to interpreting<br />
the Wasatch Range in the study area. Eardley (1934) has al-<br />
ready been mentioned. Crittenden, Sharp, and Calkins (1952)<br />
described the rangefront east of Salt Lake Valley, and Critten-<br />
den (1964) discussed the general geology of Salt Lake Coun-<br />
ty. Ferh et al. (1966) briefly described compound facets near<br />
Ogden. Gilluly (1928) noted many similar features in the<br />
Oquirrh Range. In Sharp's (1939, 1940) studies of the Ruby-<br />
East Humboldt in Nevada, several significant observations<br />
were made. These studies have suggested the following: en<br />
echelon fault patrerns are common and may cause termi-<br />
nation of portions of a range, fault dips are 60' or higher<br />
and not equal to facet angles, recurrent uplift is likely, and<br />
uplift began in the mid-Tertiary.<br />
- The iime of initiation of block faulting is a subject at-<br />
tracting attention from many workers. Davis (1903) merely<br />
said it began in the Late Tertiary, and Gilbert (1928) said it<br />
was pre-Pliocene. Later stratigraphic studies allowed more ac-<br />
curate dating, and as Eardley (1934) stated, the faulting must<br />
be post-Wasatch Conglomerate (early Eocene) and post-<br />
volcanics. The volcanics he nlentioned in the southern<br />
Wasatch have subsequently been dated as Oligocene. Eardley<br />
(1934, 1939) however, also felt the faulting began after depo-<br />
sition of the Pliocene Salt Lake Formation, and cites Plio-<br />
Pleistocene initiation. Most have believed this projected age<br />
tb be too young. Schneider (1925) stated it as Mid-Miocene<br />
on stratigraphic evidence. Others variously cited initiation of<br />
block faulting as Late Oligocene to Early Pliocene (Gilluly<br />
1928, in the Oquirrh Range), Miocene (Sharp 1939, Ruby-<br />
East Humboldt Range), Early Oligocene (Nolan 1943, Basin<br />
and Range Province overall), Middle to Late Tertiary (Hunt<br />
et al.' 1954), Oligocene (Bissell 1959), and Late Oligocene, to
RECURRENT MOVEMENT IN THE WASATCH FAULT ZONE 85<br />
Early Miocene (Proffett 1977, western Nevada). Loring more recently Cluff, Brogan, and Glass (1973) mapped all<br />
(1976) plotted all reported times for the entire Great Basin young scarps as identified with low-sun-angle photography.<br />
on maps and concluded that block faulting was contempo- The fault trace through the present study area (fig. 1) begins<br />
raneous throughout, with no net geographic migration<br />
through time. She also noted an unexplained Late Mesozoic<br />
on the south as a major en echelon break in upper Payson<br />
Canyon, gaining greater displacement northward on the west<br />
to Early Tertiary period of extension in many areas. One re- side of Loafer Mountain (Eardley 1939, Peterson 1956, Hintze<br />
cent paper by Rowley and Anderson (1972) attempted to 1962, Bissell 1964), bending abruptly eastward with no en<br />
synthesize these dates, as d~d Loring, and concluded that all echelon break around the north end of Loafer Ridge and<br />
high-angle normal faulting began during the Miocene at the northward again at the mouth of Spanish Fork Canyon<br />
latest. It appears that the safest time to place this event is in (Hodgson 1951, Bissell 1964), and from there it follows the<br />
the Miocene.<br />
base of the range with broad bends north to the Alplne area.<br />
Another subject of special interest to the present study is At Dry Creek Canyon northeast of Alplne it abruptly bends<br />
prefaulting topography. It was first described at length by nearly due west over the groin between the Traverse Moun-<br />
Eardley (1933) when he stated that a surface with 900 m of tains and Lone Peak (Marsell 1931) and abruptly trends<br />
relief existed "prior to faulting." Th~s surface can be seen northward again at the mouth of Corner Canyon. Crittenden<br />
presently perched about 900 m above the valley floor and ex- et al. (1952) suggested that this west-trending segment at<br />
h~bits a more mature-appearing topography. He deduced thls the Traverse Mountains coincides with the Charleston anby<br />
notlng a discrepancy between overall physiograph~c relief dDeer Creek faults and the three become one surface. Alplus<br />
valley fill and stratigraphic displacement along the fault though Gilbert (1928) believed the Traverse Mountains were<br />
as measured in certain areas. The mature surface can be seen a spur bounded by faults, he did not see the evidence, and<br />
in several areas, often having hanging valleys, as noted earlier Marsell (1931) concluded there are no boundlng faults other<br />
by Hayes (1926). Eardley's model also included eastward tilt than the Wasatch. This trace, then, is seen to include bends,<br />
of the mountain block by three or four degrees, which ex- both gentle and abrupt, and discont~nuous en echelon breaks.<br />
plains the filling In of back-valleys such as Heber Valley. These same features have been noted in other areas such as<br />
Similar surfaces have been observed by Crittenden et al. the Oquirrh Range (Gilluly 1928), the Ruby-East Humboldt<br />
(1952) east of Salt Lake City, by Gilluly (1928) in the Range (Sharp 1939), and the Basln and Range Province in<br />
Oquirrh Range, and by Sharp (1940) in the Ruby-East Hum- general (Nolan 1943, Rowley and Anderson 1972). One final<br />
boldt Range.<br />
note: because of pediment format~on, slope retreat, and recur-<br />
Eardley's interpretations were challenged by Threet rent movement. often the recent scam traces lie vallevward of<br />
(1959), who said the surface was everywhere a strlpped bed- the foot of the mountain block by a considerable distance as<br />
rock bench where the Manning Canyon Shale has been noted by Pack (1926) and Crittenden et al. (1952).<br />
eroded. Conclus~ons on this subject will be made later in this The main trace of the Wasatch fault system actually reppaper.<br />
Support for eastward tilting, however, came from Pe- resents a multitude of individual breaks; in addltlon to thls,<br />
terson (1969), . . who used dramage reversals. Later, when<br />
studylng stream terraces along th; front, Eardley (1970) reoften<br />
parallel faults can be observed within the mountain<br />
block and are presumably present on the valley side of the<br />
futed his earlier conclusions about eastward tilt. Stokes main trace beneath the alluv~al fill. They may be termed step<br />
(1964) suggested that the prlmary rel~ef of the prefaulting faults and were discussed by Gilluly (1928), Rowley and Ansurface<br />
IS a result of orogenic thrusting. Eardley's (1933) con- derson (1972), Baker (1959), and Hintze (1968, 196%).<br />
clusions were especially significant for the present study. It DAVIS (1909) also observed them and stated that any movemay<br />
be that his prefaulting topography was itself produced ment along them must have ceased long ago as they exert<br />
by an earlier stage of faulting he failed to recognize and that no control on topography or facet development Th~s conthe<br />
mature surface represents pedimentation during a quies- clusion appears val~d, and they probably represent older subcent<br />
period of recurrent uplift. These speculations will be dls- s~diary branches of the Wasatch fault now ~nactive. These<br />
cussed in a later section.<br />
subsid~ary faults d~p nearly uniformly In the same direction<br />
as the main break at a lower angle than the frontal fault<br />
(Hintze, 196%, 1971). An analogous "mirror-image" system<br />
Wasarch Fault Geometry<br />
was recently discussed by Proffett (1977) for an area In west-<br />
An understanding of the geometry of the Wasatch fault ern Nevada. He noted successive generations of normal faults<br />
system and its several individual fault surfaces is an impor- with the older systems having lower dips than the more retant<br />
foundat~on on which to construct a model of phys- cently actlve breaks. He suggested this represents progressive<br />
iographlc evolution of the scarp. That the rangefront is a tilting of the upthrown block with contlnulng tectonlsm<br />
true fault scarp as opposed to a fault-line scarp was esrab- causing the younger breaks to have the same initial orientalished<br />
by Davis (1909), Schneider (1925), and Pack (1926) tlon that the older, now gentler, faults had. This may be the<br />
and can be proven by the criteria of Blackwelder (1928) and best explanation for the observed Wasatch features.<br />
Johnson (1939). . . Cotton (1950) also discusses features of fault<br />
scarps, including "composite scarps" produced by recurrent<br />
faulting, which are, however, not synonymous with compound<br />
faceted spurs as envisioned in the present context.<br />
The trace of the fault at the surface is of prime impor-<br />
Proffett (1977) also discussed antlthetic faults as part of<br />
the system, and they were described for the Wasatch Range<br />
by Hintze (1968, 1971). They occur in the valley alluvium,<br />
dipping toward the main break, and also w~thln the range,<br />
where they d~p Into, and are truncated by, one of the maln<br />
tance. Marsell (1964) showed a summary of historical devel- subsidiary or step faults just discussed. Thelr origin IS a reopment<br />
of the mapped trace beginning with Gilbert (1928), sult of fault curvature at depth and related extension as diswho<br />
mapped broad bends around various salients and no en cussed by Hamblin (1967, 1970) and reaffirmed by Proffett<br />
echelon breaks. Eardley (1939) revised this to include en ech- (1977).<br />
elon traces In southern Utah Valley. Baker (1959) showed a , The d~p of the main Wasatch fault at the surface was ofmore<br />
comprehens~ve map of all faults in the study area, and ten misinterpreted by early workers to be equal to the slope
86 T C ANDERSON<br />
angle of the triangular facets (Davis l!ilO9, Gilbert 1928, even<br />
Baker 1959). It was demonstrated early, however, by Pack<br />
(1926), Schneider (1925), and Stillman (1928) that this was<br />
untrue, and the true dip angle varied between 50' and 30".<br />
Later studies have supported these higher values (Eardley<br />
1934, 1939; Bissell 1959), and it appears to be the general<br />
case in other parts of the Basin and Range (Gilluly 1928,<br />
Sharp 1939, Nolan 1943, Cotton 1950). Similar values are<br />
also reported for the Hurricane fault (Hamblin 1970), which<br />
may represent the southern continuation of the Wasatch sys-<br />
tem. It is well established, then, that the facet slopes are not<br />
equal to the fault dip and are instead a product of slope re-<br />
treat, and that the fault dips are quite high and tend to de-<br />
crease at depth.<br />
A final geometric property of the Wasatch fault system<br />
to consider is the displacement along it. Post-Pleistocene dls-<br />
placement can be well established by offset of Lake Bonne-<br />
ville sediments, as was early noted by Gilbert (1890, 1928),<br />
Davis (lw), Pack (1926), and Marsell (1931). These scarps<br />
of up to 30 m were discussed in detail by Hunt et al. (1954)<br />
and Bissell (1959, 1963, 1964). Bissell (1959) cites 60 m of<br />
post-Bonneville uplift. A good summary of these scarps and<br />
other evidence of Recent activity is that of Cluff, Hintze,<br />
and Brogan (1975). Total displacement prior to the Pleisto-<br />
cene, however, is much more speculative and variable. Early<br />
workers based their estimates on physiograhic relief alone,<br />
not knowing the fill depth in the valleys, and suggested val-<br />
ues like 1800 to 3000 m (Davis 1303, Schneider 1925), 2100<br />
m or more (Gilbert 1928), or 1500 m (Stillman 1928).<br />
Hintze (1962, 1971) included estimated valley fill thickness<br />
and arrived at 3000 to 4500 m of displacement. In some areas<br />
identifiable beds are exposed on both sides of the fault, and<br />
true stratigraphic displacement can be measured; using this<br />
basis, Eardley (1933, 1934, 1939) puts the value at 1500 to<br />
1800 m at Santaquln Canyon; Hunt et al. (1954) say 1200 to<br />
2100 m at Mt. Timpanogos; Baker (1959) cites 1800 m at<br />
Spanish Fork Canyon and 1350 meters at American Fork<br />
Canyon; and Crittenden (1964) cites 1500 m or more at the<br />
Traverse Mountains and 3000 m at the Salt Lake salient.<br />
These stratigraphic determinations may not represent total<br />
displacement inasmuch as there are often multiple fault<br />
planes, folding, and variations along the front; a good,<br />
round, average figure in 3000 m.<br />
To summarize, the Wasatch fault is a zone of normal<br />
faults dipping steeply to the west, having an irregular main<br />
trace including en echelon offsets, step faults, and antithecic<br />
faults, and a total displacement of several thousand meters;<br />
thls system is expressed physiographically as a complex fault<br />
scarp exhibiting distinctive compound faceted spurs.<br />
A few geophysical surveys have been conducted along the<br />
Wasatch Front which may provide data on the thickness of<br />
valley fill, buned faults, and so forth. The valley fill thickness<br />
in Salt Lake Valley has been interpreted geophysically by<br />
Mattick (1968, 1970) and Amow, VanHorn, and LaPray<br />
(1970) Results suggest a surface of moderate relief buried by<br />
1000 m or more of unconsolidated alluvium. A gravity and<br />
seismic profile near Ogden (Cook and Berg 1961; Cook,<br />
Berg, and Lum 1967) suggests numerous buried step faults<br />
and a total fill depth of 2100 m. Crosby (1972) also did a<br />
se~smic survey which suggested burled step faults in Juab<br />
Valley.<br />
Current and historic seismicity of the Wasatch fault zone<br />
is discussed by Cook (1971), Smith (1971), Smith and Sbar<br />
(1974), and Cluff et al. (1975). The area is defined as part of<br />
the Intermountam Seismic Belt by Smith and Sbar (1974),<br />
which is a line of high actlvlty, except for a selsmic gap<br />
from Payson to Salt Lake City. Tectonic creep has not yet<br />
been established in this area.<br />
Ongrn of Pedrmena<br />
Essential to the conceptual model presented In this paper<br />
are the origin and evolution of pediments. How pediments<br />
form is a subject whlch has in the past Incited cons~derable<br />
controversy. To avoid going into great depth on thls subject,<br />
I refer the reader to excellent reviews by King (1953), Leopold,<br />
Wolman, and Miller (1964), and Hadley (1967), and to<br />
a bibliography by Lustig (1968). Pediments were first described<br />
by Gilbert (1877) and first named by McGee (1897);<br />
Maxson (1950) reviewed the nomenclature. From the beginning,<br />
two schools of thought developed: The first stated that<br />
lateral planation by streams was the or~gin of pediments and<br />
was subscribed to by Gilbert (1877), Paige (1912), Blackwelder<br />
(1929, 1931), Johnson (1932), Howard (1942), Miller<br />
(1950), Rahn (1966, 1967), and Mackin (1970); the other<br />
school held that a combination of weathering, backwearing,<br />
and transport by sheetfloods was the origin, and this group<br />
included McGee (1897), Davis (1930, 1938), Rich (1935),<br />
King (1953), and Schultz (1955). A few have maintained<br />
that both processes are active and significant, including<br />
Bryan (1923), Gilluly (1937), Sharp (1940), and Bullock<br />
(1951); they have generally favored backwearing over lateral<br />
planation, with Sharp (1940) assigning a ratio of 60 percent<br />
backwearing to 40 percent lateral planation in the Ruby-East<br />
Humboldt Range. Lustig (1969) states that drainage evolution<br />
and slo~e retreat are the cause and eliminates sheetfloods<br />
I<br />
as a factor. Most recent observers tend to discount the effect<br />
of lateral planation by streams, whlle recognizing it does occur.<br />
Whatever their origin, broad pediments have been observed<br />
throughout the Wasatch Front area (Bullock 1951;<br />
Pack 1926; Marsell 1964; Crittenden et al. 1952). The Importance<br />
of pediments and how they will be used and interpreted<br />
in the present study will be discussed in the next section.<br />
CONCEPTUAL MODEL<br />
The origin and development of compound faceted spurs<br />
and associated pediment remnants depend on a number of<br />
surficial processes all operating on a fault block experiencing<br />
recurrent uplift. Each of these processes and its effect on the<br />
system need to be understood for a viable conceptual model<br />
to be developed. The model presented here is shown by a<br />
series of diagrams in figure 2 and 1s an extension and modifi-<br />
cation of that suggested by Hamblin (1976). However, it<br />
differs considerably from Hamblin's model in that he did not<br />
include the concepts of erosion concurrent with uplift, une-<br />
ven stream spaang, facet aplces not related to pediments, or<br />
destruction of older facets. It represents the closest approx-<br />
imation to reality that can be envisioned at present. Before<br />
describing the sequential development as seen figure 2, the<br />
most significant factors and their effect on the development<br />
will be discussed, including pediment formation and preserva-<br />
tion, recurrent uplift, downcutting by streams, slope retreat,<br />
and structural control as expressed by differential eroslon on<br />
alternate resistant and nonresistant stiata.<br />
Pedlrnent Formation<br />
As noted by King (1953), pediment formation is a uni-<br />
versal process, occurring In all dimates. It is an end product
RECURRENT MOVEMENT IN THE WASATCH FAULT ZONE<br />
FIGURE<br />
2.-Conceptual model of compound faceted spur development and pediment preservation. See text for full d~scussion. Pediment levels are numbered 1-<br />
3 for identification through sequential development. Initiation of uplift activity shown in A, with the cycle concluding in B. Quiescence indicated from<br />
B to C, and uplift resumes in D. The second active cycle ends in E, beginning another quiescent period which ends in F. A third active uplift cycle be-<br />
gins in G and concludes in H. Two uplifted remnant pediments are seen, with a third in the making during the next period of quiescence.
88 T C ANDERSON<br />
of slope retreat The preclse processes of pediment formatlon<br />
and thelr relative Importance, a controversial and often dlscussed<br />
subject, 1s not an lssue here if we state only that pedlments<br />
do indeed form and have formed in the past It is certam<br />
that if a mountain block is tectonically stable for a long<br />
enough per~od of tlme, a pediment will be formed at ~ts base<br />
with a w~dth dlrectly proportional to the durat~on of stabll-<br />
ItY<br />
become obscured or lost whatever the processes of preserva-<br />
tion; and thls must happen for very old events.<br />
Downcutr~ng<br />
Prlor to initiat~on of uplift, lt must be assumed that a<br />
drainage system ex~sted, and that uneven rather than ordered<br />
spacing of channels is l~kely These preupllft dralnages were<br />
antecedent to the faulting and exerted strong control on later<br />
landform development, especially tr~angular facets. Downcuttlng,<br />
with assoc~ated slope retreat, by these streams 1s the<br />
prlmary orlgln of facets, as noted by Davls (1909). However,<br />
the simplified presentation of upl~ft on a large scale followed<br />
Recurrenr Uphft<br />
The conclusion that upl~ft results from Intermittent discrete<br />
events on the scale of single earthquakes wlth low<br />
scarps 1s a moot polnt. Few would deduce that escarpments<br />
thousands of meters hlgh were produced In a single event,<br />
~ndeed, the largest scarps from histor~c recorded earthquakes<br />
are on the order of tens of meters high Rather, the meanlng<br />
of recurrent upl~ft as envlsloned here is that cycles of relatlvely<br />
h~gh upl~ft activ~ty occur interspersed wlth perlods of<br />
relatively low activlty or quiescence. The active perlods represent<br />
a serles of dlscrete d~splacements and associated scarps<br />
whlch result In a cumulative d~splacement much greater than<br />
that of any slngle event. While short periods of eroslon certa~nly<br />
are Interspersed between the discrete events, the length<br />
of time 1s Insufficient to allow s~gn~ficant pedlment formatlon<br />
Between these active cycles are periods of quiescence<br />
when the amount of active upl~ft 1s relatively low or nonexistent.<br />
These periods have sufficient duratlon to allow pedlments<br />
to develop as expected In addltlon to pedlment generatlon,<br />
slope retreat mod~fies the range durlng qulescence as<br />
discussed in a later sectlon Recurrence 1s seen in the close of<br />
a quiescent period and lnltlatlon of a new active cycle At<br />
this onset of uplift, and contlnulng through the active period,<br />
the pedlment surface just produced is largely destroyed<br />
by downcutting, but a remnant tends to be preserved In the<br />
rldge between dralnages, often at the apex of newly formed<br />
facets.<br />
by downcuttlng as shown by Dav~s (1909), Hamblin (1976),<br />
and others tends to cloud the real developmental history, as<br />
downcutting is undoubtedly concurrent wlth upl~ft Therefore,<br />
any conceptual model-including the present oneshould<br />
allow for contemporaneous upl~ft and erosion in facet<br />
development<br />
In additlon to forming and modifying facets, the antecedent<br />
streams are in turn affected by recurrent upl~ft In two<br />
ways. During periods of quiescence these streams tend to approach<br />
a class~c graded profile with the valley floor as baselevel.<br />
Recurrent uplift lowers the baselevel relat~ve to the<br />
streams and causes entrenchment In the lower reaches of the<br />
stream as ~t tends to restore a graded profile to the new<br />
baselevel The lower graded section meets the upper at a<br />
knlckpolnt whlch ultimately mlgrates back until ~t d~sappears<br />
If there was lnsufficlent tlrne for th~s loss, or ~f the streams<br />
faded to keep pace ~ ~ the t h faulting (Davls 1909), the<br />
knlckpolnt may remain Multlple upl~fts will cause multrple<br />
graded reaches and knickpolnts, some or all of whlch may be<br />
preserved Besldes the multiple graded profiles, a second effect<br />
of recurrent upllft 1s formatlon of w~neglass canyons and<br />
hanglng valleys by the aforemencloned entrenchment and reentrenchment,<br />
as noted by Hayes (1926) and Eardley (1933).<br />
Downcutting and assoc~ated slope retreat by streams wlth<br />
a different or~gin is also an Important process These are the<br />
Pcdlrnenr Preservation<br />
streams whlch form on the face of the facets because of the<br />
It is assumed that pediment remnants are preserved as slope of the new surface, and are thus best termed connear-horizontal<br />
r~dge segments In one of two poss~ble ways. sequent streams They modlfy the larger facets In the manner<br />
First, horizontal rldge segments are assumed to not mlgrate noted by Davls (1909, p. 746)<br />
back but are partially removed during slope retreat Thus the<br />
initlal ped~ment wldth must be large enough that subsequent<br />
removal by slope retreat is insufficient to destroy ~t In the<br />
time slnce ~ts format~on. This poss~blllty implies that any<br />
pediment remnants preserved h~gher up on the escarpment<br />
The moderate dissection of the large facet by<br />
small ravlnes results in the development of several<br />
llttle basal facets along the fault line, where they<br />
form the truncating terminals of several l~ttle spurs<br />
must have been lnlt~ally wlder than those found lower, and Davls considered thls effect to be the sole orlgln of comtherefore<br />
that elther the hlstory has been one of progress~vely pound faceted spurs as he d ~d not recognlze the effects of reshorter<br />
qulescent perlods or that older shorter qulescent perl- current upl~ft on facets (although he d~d recognlze that reods<br />
have left no record<br />
current upllft IS likely) Whlle compound facets have an<br />
Alternat~vely ~t may be proposed that horizontal r~dge add~tional origin in recurrent movement as discussed here<br />
segments are carried back wlth slope retreat processes, and and by Hamblln (1976), the effect of consequent streams is<br />
even though initial ped~ment wldth may be small, llttle 1s an Important part of the model. Inasmuch as these conlost<br />
In backwearing. This poss~blllty allows total flexibility In sequent streams, 11ke the antecedent ones, are unevenly dlsped~ment<br />
wldth through time, and therefore duratlon of tributed, the small basal facets so produced will be of varying<br />
qulescence can take any value above the minimum needed to slzes S~nce these basal facets have no genetlc relation to the<br />
produce a pedlment ~n~t~ally It implies that backwearlng as upl~fted pedlment surface and their apex elevations will vary,<br />
proposed by Penck (1924) 1s the domlnant slope retreat pro- they would not be expecred to correlate as an lndlcatron of<br />
cess, and not downwearlng as suggested by Davls (1922) most recent upl~ft If, however, basal facets are present whlch<br />
Although the conceptual model could adopt elther of have a preserved pedlment remnant at or near thelr apex, and<br />
these hypotheses, the latter seems preferable to allow preser- these remnants correlate well, ~t 1s Ilkely that these facets are<br />
vation of pediments, a conclusion from the observed data 1s not merely a result of consequent stream development. Both<br />
made later to support thls preference Certainly it is perceived types are apparently seen In real~ty, and both types are exthat<br />
~f a suffic~ently long erosive perlod occurs, features will pected In the model.
Recurrent uplift and renewed downcutting will modify<br />
both consequent streams and facets. The consequent streams<br />
may continue across the pediment, cut through it, and re-<br />
main as a larger extended system still on the face of a now<br />
larger facet, or they may be dlverted into another drainage<br />
and eventually lost, while new consequent streams are in-<br />
titiated on the newly formed facets. As large facets are up-<br />
lifted, they tend to recede and lose character but may be pre-<br />
served. However, the small basal facets whlch form from<br />
consequent streams are generally lost during recurrent uplift<br />
owing to more vigorous downcuttlng and "sidewearing" by<br />
the larger antecedent streams. A considerat~on of these and<br />
previous conclusions suggests that through cycles of recur-<br />
rent uplift, preserved pedrment remnants should dominate<br />
over preserved facets in later stages<br />
Slope Retreat<br />
Slope retreat is a pervasrve process involved in all the<br />
foregoing d~scussions; certain specific effects, however, need<br />
mention. Two mechanrsms of slope retreat, or a combination<br />
of the two, may be involved backwearing (Penck 1924), or<br />
the near-parallel retreat of scarps, and downwearing (Dav~s<br />
19221, or the reduct~on of a surface to a penepla~n. The best<br />
concept for purposes of this model 1s stated thus: slope retreat<br />
causes a near-parallel backwearing of the escarpment<br />
with a reduction In slope angle with time. The result of this<br />
is that the longer a feature, slope, ridge, or facet has been<br />
exposed to weathering and eroslon, the more gentle ~ts slope<br />
angle will become.<br />
One significant deduction 1s therefore that the surface of<br />
triangular facets 1s a result of slope retreat to a stable slope<br />
angle and does not reflect the actual fault surface, which<br />
usually drps more than 60'. Th~s relation, discussed in a prior<br />
sectlon, has been observed by many workers, notably GIIluly<br />
(1928, p 1161, who stated.<br />
It seems wholly improbable that any scarp char-<br />
acterized by 'faceted spurs' of phys~ographically<br />
greater age should have retained the dip of its<br />
bounding fault.<br />
Nevertheless, for a unique actlve uplift period, the facet slope<br />
angles will be slmilar. Most basal facet angles range between<br />
20' and 40' as recorded by Dav~s (1909), Gilbert (19281,<br />
Gllluly (1928), Baker (1959), and others, with 35' a good<br />
average figure. Compound facets above the basal facets, inter-<br />
preted to be older, drp about 25' (Davis 1909)<br />
Structural Control<br />
One significant controlling parameter not expressed In<br />
the model of figure 2 is geologrc structure Where contrastlng<br />
resistance to eroslon is seen In the l~thologies making<br />
up the mountain block, rt should be expected that d~fferent~al<br />
erosion may In time cause less resrstant unrts to be<br />
stripped off of more resistant units formlng a stripped surface<br />
bench. These surfaces could be misinterpreted as uplrfted<br />
remnant pediments if rhe~r true orlgln were unknown; however,<br />
they can usually be identified as such In thrs region.<br />
It 1s important not to totally disregard any true stripped<br />
benches for the following reason since geologic structure<br />
here is not that of uniformly horrzontal beds (Baker 1964,<br />
1972, 1973), there will arise cases in which structural trends<br />
cross remnant pedrment levels. These pediment surfaces may<br />
cornc~de with str~pped bedrock surfaces at those points, Indeed,<br />
they may be more broad there than normal because of<br />
RECURRENT MOVEMENT IN THE WASATCH FAULT ZONE 89<br />
the lithology contrast. They can still be considered val~d<br />
pediment remnants if the overall correlation of pediments<br />
does not directly follow the structural trends. However, it<br />
must also be expected that in some areas structural control is<br />
so dominant that valid correlations of ambiguous data IS im-<br />
possible.<br />
Sequmr~al Development<br />
Each of these geologic controls has been consrdered in<br />
the preparation of the model shown in figure 2. The onset<br />
of uplift activity on a block with preexistent dramage is seen<br />
in A, with the active cycle concluding in B. Only a low<br />
scarp signals the initiation of activity, and downcutting be-<br />
gins at the same time. Downcutting is concurrent with up-<br />
lift from A to B, and the triangular facets produced by this<br />
are not all the same size as a result of unwen spaclng of the<br />
preexistent streams. The facet between closely spaced streams<br />
is much smaller as requrred by slope retreat, and the apex of<br />
that facet connects with the undlssected surface in a r~dgeline<br />
rather than meeting it directly B also represents the 6egln-<br />
nlng of a quiescent phase, whrch concludes In C with the<br />
formation of a broad pediment, compound facets, and a<br />
graded stream profile. Note that none of these facets are dl-<br />
rectly related to pedimentation. A new active cycle begrns In<br />
D and concludes in E, with corresponding modificatrons of<br />
drainage, valley form, facets, and ridges. Some of the origlnal<br />
consequent streams have been diverted and uplifted facets<br />
lost while others remain. The pediment IS preserved at an ac-<br />
cordant level, though not always at a facet apex. Incipient<br />
wineglass canyons and doubly graded drarnage wrth a<br />
knickpolnt are evident. A quiescent period then begins, and<br />
ends in F with a new pediment produced. The remnant up-<br />
lifted pedlrnent is preserved, and the. antecedent screams are<br />
still doubly graded w~th knickpornt. Another active phase begins<br />
in G and concludes in H, with two remnant pediments<br />
uplifted and preserved and a third in the making. Forms become<br />
more complex, as facets are created and destroyed, and<br />
antecedent streams now have three separately graded segments.<br />
Wineglass canyons are prominent. Some of the initial<br />
large facets remaln in compound systems, while others have<br />
been lost leavlng only most-recent-stage facets at the end of a<br />
long ridge. Multiple basal facets are unrelated to pediment<br />
uplift, resulting Instead from consequent stream dissection of<br />
larger facets which are related to a pediment. The cycle can<br />
contlnue through successrve generations, pedrment remants<br />
tending to be preserved and facet forms lost or mod~fied A<br />
comparison of the "final stage" seen in figure 2H with the<br />
features of Spanish Fork Peak (fig. 3) reveals many slmilaritres<br />
and supports the observations of the preceding drscussron.<br />
METHODS<br />
The prime objectrve of the study was to correlate the<br />
remnant pediment surfaces and construct a history of drs-<br />
placement. The first step, then, was to identify these features<br />
and observe their characteristrcs so they could be mapped on<br />
a topographic base and projected to a profile ready for corre-<br />
lation. The triangular facets have been well descrrbed by sev-<br />
eral workers, from the first identification by Davis (1909), to<br />
later work by Gilbert (1928), Gilluly (1928), Sharp (1939,<br />
1940), and others studying areal geology. Some have de-<br />
scrrbed the compound nature of the facets, such as Bissell<br />
(1964), Rigby (1962), Feth et al. (1966), and Rigby and<br />
Hrntze (1968), but the pediment remnants have been essen-
90 T. C. ANDERSON<br />
FIGURE 3.-Oblique aerial photograph of Spanish Fork Peak.<br />
FIGURE 4 -0blrque aerral photograph of selected facets on Spanrsh Fork<br />
Pak. See figure 6 for a topograph~c map of thrs area.<br />
&i2<br />
FIGURE >.-Oblique aerial photograph of area just north of Hobble Creek<br />
Canyon.<br />
tially undescribed. Davis (1309) expected recurrent uplift but<br />
did not recognize any features produced by it, and Sharp<br />
(1939, 1940) noticed horizontal ridge segments or "treads,"<br />
but did not describe these definitively as remnant pediments.<br />
It was not until the work of Hamblin (1976) that the pedi-<br />
ments were described and tentatively correlated.<br />
The remnant pediments consist of near-horizontal ridge<br />
segments often beginning at the apex of triangular facets as<br />
can be seen in figures 4 and 5. They usually dip towards the<br />
fault a few degrees, but occasionally have a backward dip as<br />
seen in figure 5, which may indicate eastward tilt on the<br />
mountain block (as suggested by Eardley 1933 and Peterson<br />
1969). The width of the pediment surface, as expressed by<br />
the length of the ridge segment, varies from zero up to 1200<br />
m, with the minimum identifiable size being about 30 m.<br />
They are best observed with vertical stereo aerial photos in<br />
conjunction with oblique aerial photos. As a planimetric plot<br />
was desired for correlation, the method consisted of identi-<br />
fication by aerial photography followed by mapping on a top-<br />
ographic base.<br />
Aerial Phorognphy<br />
Proper identification of both facets and pediment rem-<br />
nants requires critical lighting to enhance shadow detail and<br />
emphasize form. This is best done with low-sun-angle pho-<br />
tography, as described by Cluff and Slemmons (1971) and<br />
Cluff et al. (1973) in a project involving Recent scarp recog-<br />
nition for the Wasatch fault zone. The vertical photography<br />
they shot was examined for the study area of this report and<br />
found to be quite helpful. Their coverage, however, did not<br />
include much of the mountain front, and so additional verti-<br />
cal aerial photography was obtained at two scales (about<br />
1:60,000 and 1:28,000) to cover the study area. Fortunately,<br />
much of. this additional photography was taken at a low<br />
enough sun angle for the features to be well modeled. These<br />
vertical aerial photos were then viewed stereoscopically to aid<br />
in identification of facets and pediments, with the low-alti-<br />
tude coverage being most helpful.<br />
Oblique aerial photography also proved to be essential in<br />
feature identification. Three flights were taken to provide op-<br />
timum lighting conditions, one in late afternoon and two in<br />
the morning. It was found that the southern third of the.<br />
study area, from Springville south, was best photographed in<br />
the late afternoon; the Timpanogos and south Provo areas<br />
required early to midmorning light; and the central Provo<br />
and Alpine areas did not receive proper light until late morn-<br />
ing. This oblique aerial photography included both black-and-<br />
white prints and color transparencies, with the color slides<br />
proving to be most useful in observation and identification<br />
of pediments.<br />
Pediment Mapping<br />
With identification of the landforms from the photo-<br />
graphs, the next step was mapping, or plotting, these fea-<br />
tures on the topographic quadrangle maps. Nearly the entire<br />
study area is covered by maps at a scale of 1:24,000, the ex-<br />
ception being the extreme southern end near Payson Canyon,<br />
which has been mapped at 1:62,500 only. The facets and<br />
pediments are usually well expressed in the topographic con-<br />
tours, and there was little difficulty in locating positions and<br />
elevations to the nearest contour. A segment of the Spanish<br />
Fork Peak quadrangle which includes the same area seen in<br />
the photograph of figure 4 is shown in figure 6. The three<br />
prominent basal facets and pediments at their apices are easily
RECURRENT MOVEMENT IN THE WASATCH FAULT ZONE 91<br />
recognized in the contour map. For mapping purposes thin rose and fell gently to suggest hinge- or scissor-type move-<br />
lines represent facet outlines and ridgelines, and heavy lines ment. Strongly inclined correlations, however, were deemed<br />
represent remnant pediments, shown for this same area in unlikely and not allowed in the process. Pediment width data<br />
figure 7. As the minimum identifiable pediment width was assisted the correlation, but was not a controlling factor, as<br />
about 30 m, this was plotted as a heavy dot. Also plotted as the initial widths and degree of preservation were probably<br />
dots were all facet apices which did not already have a dis-<br />
tinct pediment remnant.<br />
After features were plotted in this manner on each of the<br />
quadrangle maps, the information from the separate quad-<br />
rangles was transferred to a large acetate overlay, including<br />
elevation values for all the pediment remnants and facet<br />
apices. The southern portion at the smaller scale was en-<br />
larged to match the rest of the area. In all, 1275 data points<br />