Cretaceous biostratigraphy in the Wyoming thrust belt
- U.S. Geological Survey, Denver, CO
Biostratigraphy is essential to exploration for oil and gas in the Wyoming thrust belt because fossils provide a temporal framework for interpretation of events of faulting, erosion, sedimentation, and the development of hydrocarbon traps and migration pathways. In the Cretaceous section, fossils are especially useful for dating and correlating repetitive facies of different ages in structurally complex terrain. The biostratigraphic zonation for the region is based on megafossils (chiefly ammonites), which permit accurate dating and correlation of outcrop sections, and which have been calibrated with the radiometric time scale for the Western Interior. Molluscan and vertebrate zone fossils are difficult to obtain from the subsurface, however, and ammonities are restricted to rocks of margin origin. Palynomorphs (plant microfossils) have proven to be the most valuable fossils in investigations of stratigraphy and structures in the subsurface of the thrust belt because palynomorphs can be recovered from drill cuttings. Palynomorphs also are found in both marine and nonmarine rocks and can be used for correlation between facies. In this paper, stratigraphic ranges of selected Cretaceous marine and nonmarine palynomorphs in previously designated reference sections in Fossil Basin, Wyoming, are correlated with the occurrence of ammonities and other zone fossils in the same sections. These correlations can be related to known isotopic ages, and they contribute to the calibration of palynomorph ranges in the Cretaceous of the Western Interior.
- OSTI ID:
- 6413708
- Journal Information:
- Mt. Geol.; (United States), Vol. 19:3
- Country of Publication:
- United States
- Language:
- English
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03 NATURAL GAS
GEOLOGIC STRUCTURES
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AGE ESTIMATION
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CRETACEOUS PERIOD
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GEOLOGIC TRAPS
MAPPING
NATURAL GAS
PALEONTOLOGY
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FEDERAL REGION VIII
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030200 - Natural Gas- Reserves
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