RESEARCH· ·1970·

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VAN ALSTINE B45 FIGURE 3.-View west across late Tertiary trough to source area of slide blocks in the Sawatch Range, showing Dry Union sediments (Td) faulted against Precambrian gneisses ( p£). north of Poncha Springs, records various geologic events that occurred in this area in late Tertiary time. The formation is chiefly composed of unconsolidated gravel, sand, silt, clay, volcanic ash, and limestone deposited in alluvial-fan, mudflow, and pond environments, and it contains the detached Paleozoic blocks (fig. 4). The basal part is largely mud flow material consisting of unstratified gravel containing abundant clasts of vesicular basalt, andesite, and latite derived from lower Oligocene lava flows at the eastern and southwestern edges of the trough. Especially conspicuous at many weathered outcrops are agates and bluegray angular jasperoid fragments of intensely silicified volcanic rocks transported from the Bonanza volcanic center to the southwest (Burbank, 1932, p. 71-77; Cook, 1961, p. 289). Within the Tertiary sediments above the basal volcanic gravel, clasts of Paleozoic rocks are common among the debris. They have lithologies and ages similar to those of the adjacent detached Paleozoic blocks found at several stratigraphic horizons. On the ridge crest east of Little Cochetopa Creek, blocks of limestone (some fetid and containing black chert) and dolomite (witJhout chert) probably rure from tJhe Leadville Limestone of Mississippian age; fossils in similar limestone clasts in the adjacent debris were identified as ( 1) fragments of Ovatia cf. 0. laevicosta (White), known to occur in the Leadville Limestone, (2) echinoderm debris, and ( 3) fragments of a syringoporoid coral ( J. T. Dutro, Jr., written commun., Feb. 7, 1969). Precambrian debris containing gneiss, granite, and pegmatite boulders as much as 12 feet in diameter is predominant in the upper part of the trough fill. Thus, the stratigraphy of the Dry Union Formation locally reflects, in reveroo, the sequence of rocks in the adjoining source areas ; debris, first from Tertiary volcanic rocks and then from progressively older Paleozoic and Precambrian formations, was stripped, carried into the trough, and deposited. Mesozoic rock fragments from the Morrison Formation, Dakota Sandstone, and Mancos Shale were not observed among the clasts in the Dry Union Formation and evidently were not shed eastward into this trough. These three formations are exposed on the west edge of the Sawatch Range. Dings and Robinson (1957, p. 9, 18-19) suggested that possibly several thousand feet of Mesozoic sedimentary rock was removed from. the range by erosion. The apparent Jack of Mesozoic debris in the Tertiary trough deposits indicates that the three Mesozoic units may not have covered the base- and precious-metal district near Monarch and Garfield in Tertiary time when the mineralization occurred. In the area near Little Cochetopa Creek, the Dry Union Formation may be more than 10,000 feet thick, if the moderate westward dip persists to the fault at the werst edge of the trough. The "'estwrurd tiltJing possibly is related to late Pliocene uplift of the Sangre de Cristo Range to the east.
B46 STRUCTURAL GEOLOGY FIGURE 4.-View south along Little Oochetopa Creek, showing faulted Miocene and Pliocene sediments (Dry Union Formation, Td) containing blocks of Paleozoic rocks (ps); 'underlying Oligocene volcanic rocks (Tv) rest on Precambrian gneiss (p£) of Sangre de Cristo Range. The Pliocene age of some of the trough deposits now assigned to the Dry Union Formation was determined from fossil horse teeth and camel bones found to the east and north in the Arkansas Valley (Powel'S, 1935, p. 189 ; Van Alstine and Lewis, 1960) . The age, however, is now extended to late Miocene, for at vertebrate fossil locality D750 (fig. 2) several identifiable horse teeth were collected from locally gypsiferous greenish clays and silts. G. E. Lewis (written commun., Dec. 17, 1968) reported tJhe fossils .to be cheek teeth of A! erychippu8 cf. A!. calamariU.
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Page 3 and 4: CONTENTS GEOLOGIC STUDIES Petrology
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Page 7 and 8: B2 PETROLOGY AND PETROGRAPHY for bi
Page 9 and 10: B4 PETROLOGY AND PETROGRAPHY has be
Page 11 and 12: B6 PETROLOGY AND PETROGRAPHY. 32
Page 13 and 14: B8 PETROLOGY AND PETROGRAPHY TABLE
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Page 25 and 26: B20 PETROLOGY AND PETROGRAPHY Sigva
Page 27 and 28: B22 PETROLOGY AND PETROGRAPHY EXPLA
Page 29 and 30: B24 PE~ROLOGY AND PETROGRAPHY schis
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Page 41 and 42: B36 PETROLOGY AND PETROGRAPHY Post-
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Page 47 and 48: B42 PETROLOGY AND PETROGRAPHY Creta
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Page 55 and 56: B50 STRUCTURAL GEOLOGY clined slide
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Page 59 and 60: B54 GEOPHYSICS (1950), Domzalski (1
Page 61 and 62: B56 GEOPHYSICS STRATIGRAPHY AND LIT
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Page 65 and 66: B60 GEOPHYSICS value. A normal free
Page 67 and 68: B62 GEOPHYSICS Hammer, Sigmund, 193
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Page 73 and 74: B68 GEOPHYSICS A' San 0 p A c I F I
Page 75 and 76: B70 GEOPHYSICS lies occur over rela
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Page 79 and 80: B74 GEOPHYSICS igneous massif is co
Page 81 and 82: B76 GEOPHYSICS A 50 Bouguer gravity
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Page 85 and 86: B80 GEOPHYSICS FIGURE 1.-Bouguell'
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Page 89 and 90: B84 GEOPHYSICS B 600 B' 500 400 (/)
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Page 93 and 94: EXPLANATION Pikes Peak • batholit
Page 95 and 96: DISTRIBUTION OF URANIUM IN URANIUM-
Page 97 and 98: B92 GEOCHRONOLOGY Fleischer, R. L.,
Page 99 and 100: B94 ECONOMIC GEOLOGY 103° 35' w 1/
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'B96 ECONOMIC ·GEOLOGY 0 500 FEET
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B98 ECONOMIC GEOLOGY TABLE !.-Summa
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BlOO ECONOMIC GEOLOGY surface seems
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GE 1 0LOGICAL SURVEY RESEA·RCH 197
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B104 EJrucJh of the four samples wa
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B106 ECONOMIC GEOLOGY R. 56 E. R. 5
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B108 ECONOMIC GEOLOGY outcrop under
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BllO Brady, of the Museum of Northe
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Bll2 PALEONTOLOGY FIGURE 1.-ProtobZ
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B114 PALEONTOLOGY c .,;# I I ' ' lO
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B116 PALEONTOLOGY ments, the larges
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GErOLOGICAL SURVEY RESEA·RCH 1970
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B120 L xMH 'xE soo~~B_R~I __ T_I __
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B122 PALEONTOLOGY Tetrataxis sp. Te
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GE~OLOGICAL SURVEY RESEARCH 1970 TR
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Bl26 PALEONTOLOGY TABLE 2.-Ranges o
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B128 PALEONTOLOGY l
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BI30 PALEONTOLOGY Ocmt/rrence.-P. m
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Bl32 PALEONTOLOGY proximately 5.7 m
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Bl34 PALEONTOLOGY a b c d e f g - D
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Bl36 PALEONTOLOGY --- 1963. The ori
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B138 PALEONTOLOGY core are m1ssmg,
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B140 PALEONTOLOGY death assemblage:
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Bl42 STRATIGRAPHY EXPLANATION l:.\.
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B144 STRATIGRAPHY ver. We do not in
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B146 STRATIGRAPHY age. A stratigrap
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B148 5 10 15 20 X X Plntygonus Pla.
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GE~OLOGICAL SURVEY RESEARCH 1970 CL
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B152 STRATIGRAPHY at a depth of 58
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••••• 0 .... ••••
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B156 STRATIGRAPHY REFERENCES Brown,
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B158 STRATIGRAPHY In what follows,
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Bi60 STRATIGRAPHY TABLE !.-Stratigr
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B162 SEDIMENTATION with increasing
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llj ...... ~ TABLE 2.-Specific grav
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B166 TABLE 3.-Settling time for a 1
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Bl68 GEOMORPHOLOGY 74° 44° YERMON
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B170 GEOMORPHOLOGY have also been r
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B172 GEOMORPHOLOGY end of Long Isla
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GEOLOGICAL SURVEY RESEARCH 1970 DET
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~ooo ______________ B176 ANALYTICAL
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B178 terranes where the search for
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B180 Reproducibility Replicate anal
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B182 ANALYTICAL METHODS in the aque
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GEOLOGICAL SURVEY RESEARCH 1970 CHE
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B186 ANALYTICAL METHODS 3.31 percen
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Bl88 ANALYTICAL METHODS 3" 2%" Oute
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GEOLOGICAL SURVEY RESEA~RCH 1970 TR
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B192 GROUND-WATER RECHARGE I T I 14
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B194 GROUND-WATER RECHARGE Therefor
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GEOLOGICAL SURVEY RESEARCH 1970 PRE
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B198 GROUND-WATER RECHARGE the basi
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B200 GROUND-WATER RECHARGE t \ \)
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B202 GROUND-WATER RECHARGE Water is
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B204 GROUND-WATER CONTAMINATION rv
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B206 GROUND-WATER CONTAMINATION TAB
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B208. GROUND-WATER CONTAMINATION fa
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GEOLOGICAL SURVEY RESEARCH 1970 MEA
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B212 SURFACE WATER plotted, and the
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GEOLOGICAL SURVEY RESEA·RCH 1970 T
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B216 SURFACE WATER however, if the
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B218 SURFACE WATER TABLE 4.-Variati
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B220 RELATION· BETWEEN GROUND eral
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B222 -0.010 f -0.005 (i) RELATION B
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GEOLOGICAL SURVEY RESEARCH 1970 THE
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'B226 RELATION BETWEEN GROUND WATER
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B228 RELATION, BETWEEN GROUND WATER
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B230 RELATION BETWEEN GROUND WATER
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GEOLOGICAL SURVEY RESEARCH 1970 HYD
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B234 EROSION AND SEDIMENTATION side
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B236 EROSION AND SEDIMENTATION s·o
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B238 EROSION AND SEDIMENTATION Cont
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B240 EROSION AND SEDIMENTATION 2 3
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GEOLOGICAL SURVEY RESEARCH 1970 SPE
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B244 GEOCHEMISTRY OF WATER REFERENC
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B246 HYDROLOGIC TECHNIQUES The upla
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B248 HYDROLOGIC TECHNIQUES type in
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GEOLOGICAL SURVEY RESEARCH 1970 ,,.
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B252 formula may also be useful in
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GEO'LOGICAL SURVEY RESEARCH 1970 CO
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B256 randomly fluctuating component
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B258 HYDROLOGIC TECHNIQUES 1.0 ~ Qj
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~ B260 HYDROLOGIC TECHNIQUES 1-3, f
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I B262 HYDROLOGIC TECHNIQUES REFERE
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,' B264 Page Gravitational sliding,
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RESEARCH· ·1970·

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