radiolaria - Marum

Radiolaria 14 Bibliography - 1989
taken place on the flanks of the guyot during transit across the
western Pacific, or on the trench slope during or after subduction
and offscraping about 0.5 Ma.
Bechennec, F., Le Métour, J., Rabu, D., Beurrier,
M., Bourdillon-Jeudy de Grissac, C., De Wever,
P., Tegyey, M. & Villey, M. 1989. Géologie d'une
chaîne issue de la Téthys: Les montagnes d'Oman. Bull. Soc.
géol. France, 5/2, 167-188.
The Oman mountains are a composite orogenic belt that was
built during two major orogenic cycles: the Eo-Alpine cycle, that
terminated with the overthrusting of the Hawasina nappes and the
obduction of a part of the Tethyan oceanic crust onto the Arabian
platform, and the Alpine cycle, during which the present mountain
range was uplifted. The basement to the Oman mountains itself
consists of two parts, one part that was deformed and
metamorphosed during an old Panafrican cycle, and a sedimentary
and volcanic part (autochthonous unit A) that was weakly deformed
during a younger Panafrican and the Hercynian cycle. The Eo-Alpine
cycle began in the late Permian with the transgression of the
fusulinid sea onto the northern edge of Gondwana, and crustal
extension within Gondwana that gave rise to the Hamrat Duru basin.
Renewed extension during the Triassic led to the formation of the
Umar basin, Misfah horst and Aridh trough on the internal side of the
Hamrat Duru basin, these four structures together constituting the
Hawasina basin. The Jurassic was a period of quiescence, preceding
a further phase of extensional tectonism during the late Tithonian-
Berriasian, which provoked the foundering of the northeastern edge
of the Arabian platform, the westward retreat of the continental
slope and subsidence of the Hawasina basin. Majolica facies
sediments were deposited on the former platform, and the Hawasina
basin, most of which was below the CCD, was characterized by the
deposition of siliceous pelagic sediments. During the early
Cretaceous the process was reversed, the submerged parts of the
platform being covered by a regressive mega-sequence and in the
Hawasina basin carbonate turbidites reappared. During the late
Albian-early Cenomanian times, the oceanic Samail basin opened on
the southern margin of the newly-formed Tethys. In the late
Cretaceous the Eo-Alpine Oman mountain belt was built on the
northeast edge of the Arabian platform. The Eo-Alpine orogeny was
characterized by two main events. One was the subduction of the
northeastern promontory of the Arabian platform, commencing
during the Turonian, which was accompanied by the development of
oceanward-verging tangential shears, and, on the internal edge of
the platform (the Saih Hatat area), by HP-LT metamorphism The
other main event was the closure of the Samail oceanic basin, that
started during the late Turonian-Coniacian times, and resulted in the
thrusting of the Samail ophiolite nappe together with the
sedimentary Hawasina nappes onto the foreland. Obduction was
followed by uplift of the Eo-Alpine mountains whose erosion began
during the Maastrichtian. The Eo-Alpine phase was succeeded by an
Alpine cycle between Maastrichtian and Burdigalian times
characterized by unstable platform sedimentation and giving the
Oman mountains their present-day architecture.
Blome, C.D., Reed, K.M. & Tailleur, I.L. 1989.
Radiolarian biostratigraphy of the Otuk Formation in and
near the National Petroleum Reserve in Alaska. In: Geology
and exploration of the National Petroleum Reserve in Alaska,
1974 to 1982. (Gryc, G., Ed.), vol. 1399. United States
geological Survey, professional Paper, Report, pp. 725-776.
Bedded chert is a common rock type in the Brooks Range orogen
of northern Alaska and is locally abundant in all parts of the orogen
except the northeast brooks Range. Pennsylvanian to Jurassic
radiolarian chert is especially widespread in the west, in and
adjacent to the De Long Mountains. The Cretaceous Brookian
orogeny superposed and disordered the bedded chert sequences.
Initial fore shortening and subsequent Laramide-style deformation
created a complex of Carboniferous to Jurassic sedimentary
deposits that has been rearranged into a stack of thrust sheets,
each distinguished by its own physical, paleontologic, and tectonic
characteristics (Mayfield and others, chapter 7, 1983b).
Biostratigraphic control in our study was inadequate to refine many
of the earlier paleontologic syntheses (Tailleur and others, 1966;
Brosgé and Tailleur, 1970). Verification of the ages for radiolarian
cherts was particularly difficult because the only age diagnostic
megafossils were found in the younger horizons. The older parts of
the Otuk Formation (Mull and others, 1982) have yielded few useful
megafossils.
Renewed investigations of the National Petroleum Reserve in
Alaska (NPRA) in the middle and late 1970's corresponded closely
with development of a land-based Mesozoic radiolarian zonal scheme
pioneered by Pessagno (1976, 1977a, b). Nearly a thousand chert
samples from various field projects and from one well were
processed for radiolarians during an 8-yr period in the hope that the
radiolarian biostratigraphy might refine the ages of the various chert
sequences. Investigations of resources other than hydrocarbons in
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1977 and 1978 by Michael Churkin, Jr., Inyo Ellersieck, Carl Huie,
D.L. Jones, C.F. Mayfield, W.J. Nokleberg, I.L. Tailleur, D.L. Vickery,
and G.R. Winkler produced a set of mostly uncontrolled samples from
the southern part of the NPRA and the foothills belt eastward to
Tiglukpuk Creek (fig. 33.1A). During large-scale mapping in 1978,
1979, and 1981 by D.C. Blanchard, S.M. Curtis, Ellersieck, Mayfield,
and Tailleur, a large set of chert samples was collected from the De
Long Mountains, Misheguk Mountain, and Noatak 1:250,000 scale
quadrangles in the western Brooks Range. In 1978, R.J. Witmer and
Tailleur collected samples from sections near the Lisburne well in
the southern part of the NPRA. W.W. Chamberlain, B.L. Murchey, P.B.
Swain, and Witmer systematically sampled several locations in the
same area during the 1979 field season (Murchey and others,
1981). During the 1980 field season, Murchey and Tailleur
collected samples from reference sections in the lowest allochthon,
on the Kiruktagiak River (lat 68°44'15'' N., long 152°20'00'' W.); on
Tiglukpulc Creek, 150 km east of the NPRA; and from Agate Rock on
the Lisburne Peninsula, 175 km west of the NPRA. J.S. Kelley
sampled several sections in the lowest thrust sheet between the
NPRA and Tiglukpuk Creek in 1982. Some of Tailleur's 1982
samples were collected at sections near Mount Annette (100 km
east of Chandler Lake quadrangle). K.M. Reed and Tailleur collected
radiolarian chert on the Lisburne Peninsula in 1982. Projects headed
by C.G. Mull (Alaska Division of Geological and Geophysical Surveys)
and Kelley continued to supply Brooks Range cherts for age analysis
(see also Bodnar, 1984). The success of radiolarian biostratigraphy,
together with endothyroid and molluscan dating, has greatly aided
recent geological mapping (Mayfield and others, chapter 8; Curtis
and others, 1982, 1983, 1984; Ellersieck and others, 1982, 1983,
1984; Mayfield and others, 1982, 1983a, b, 1984a, b, 19~7).
This study includes radiolarian faunas from lithostratigraphic
sections through the Otuk Formation (fig. 33.2) that include shale,
chert, and limestone of Triassic through Early Jurassic age. Our
biostratigraphic scheme for the Otuk Formation is based on
radiolarian and molluscan faunal assemblages from measured
sections, as well as correlation with radiolarian faunas described in
recent reports (through 1987) concerning Triassic faunas from Baja
California, Oregon, British Columbia and Japan.
Blueford, J.R. 1989. Radiolarian evidence: Late
Cretaceous through Eocene ocean circulation patterns. In:
Siliceous Deposits of the Tethys and Pacific Regions. (Hein,
J.R. & Obradovic, J., Eds.). Springer-Verlag, New York. pp.
19-29.
Radiolarian assemblages, in Late Cretaceous through Eocene
biosiliceous sediments, can help trace major paleocirculation
patterns. Abundant radiolarians today indicate normal saline,
oceanic conditions, so their presence in the fossil record documents
seaways analogous to areas of presentday radiolarian deposition.
The circulation patterns indicated by radiolarian distributions
support and slightly modify previous paleoceanographic models.
During the Late Cretaceous, circulation in the equatorial belt was
continuous from the Pacific through the regions of the present-day
Atlantic and into the Caspian Sea-Ural Mountains of the Soviet
Union. Seaways connecting the Arctic and North Pacific Ocean
enabled a wide distribution of radiolarian fauna. Paleocene
radiolarian deposits are not abundant, and may indicate a circulation
pattern that became restricted. Oceanographic conditions that
prevent siliceous deposition are many, including regressions,
weakened upwelling, lack of dissolved silica, temperature, and other
biological or physical conditions. The distribution of Eocene
radiolarians indicates renewed wide circulation in the Paleogene
oceans. Radiolarian distribution needs to be considered with other
fossil assemblages and with paleomagnetic data to accurately
reconstruct the positions of the continents and the oceanic
circulation patterns.
Bohrman, G. & Stein, R. 1989. Biogenic silica at ODP
Site 647 in the Southern Labrador Sea: occurrence,
diagenesis, and paleoceanographic implications. In:
Proceedings of the Ocean Drilling Program, Scientific
Results. (Srivastava, S.P., Arthur, M.A., Clement, B. et al.,
Eds.), vol. 105. College Station, TX (Ocean Drilling
Program), pp. 155-170.
Eocene to Holocene sediments from Ocean Drilling Program
(ODP) Site 647 (Leg 105) in the southern Labrador Sea,
approximately 200 km south of the Gloria Drift deposits, were
investigated for their biogenic silica composition. Three sections of
different diagenetic alteration products of primary siliceous
components could be distinguished: (I) opal-A was recorded in the
Miocene and the early Oligocene time intervals with strongly
corroded siliceous skeletons in the Miocene and mostly well
preserved biogenic opal in the early Oligocene; (2) opal-CT
precipitation occurs between 250-440 meters below seafloor
(mbsf) (earliest Oligocene to late Eocene); (3) between 620-650
mbsf (early/middle Eocene), biogenic opal was transformed to clay
minerals by authigenesis of smectites. Using accumulation rates of