Radiolarian biostratigraphy of the Otuk Formation in and near the National Petroleum Reserve in Alaska
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 foreshortening 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. Biostratigraphic control in this study was inadequate to refine many of the earlier paleontologic syntheses. 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 have yielded few useful megafossils. This study includes radiolarian faunas from lithostratigraphic sections through the Otuk Formation that include shale, chert, and limestone of Triassic through Early Jurassic age. This 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.
- OSTI ID:
- 6844105
- Journal Information:
- United States Geological Survey, Professional Paper; (USA), Journal Name: United States Geological Survey, Professional Paper; (USA)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALASKA
STRATEGIC PETROLEUM RESERVE
PALEONTOLOGY
STRATIGRAPHY
AGE ESTIMATION
CARBONIFEROUS PERIOD
CHERT
DEFORMATION
FOSSILS
GEOLOGIC FORMATIONS
GEOLOGIC STRATA
JURASSIC PERIOD
LIMESTONE
MOLLUSCS
MOUNTAINS
PROTOZOA
RESERVOIR ROCK
SEDIMENTARY ROCKS
SHALES
ANIMALS
AQUATIC ORGANISMS
CARBONATE ROCKS
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOLOGY
INVERTEBRATES
MESOZOIC ERA
MICROORGANISMS
NORTH AMERICA
PALEOZOIC ERA
RESERVES
RESOURCES
ROCKS
USA
020200* - Petroleum- Reserves
Geology
& Exploration