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The AAPG/Datapages Combined Publications Database

Earth Science Bulletin (WGA)


Earth Science Bulletin
Vol. 15 (1982), No. 1. (Annual), Page 128

Abstract: Regional Unconformity at Base First Frontier Sandstone, Central Wyoming

William H. Curry, III1

Joint Meeting: University of Wyoming Department of Geology and Geophysics Wyoming Geological Association Geological Survey of Wyoming: April 2-4, 1982 Laramie, Wyoming: Subsurface Practices in Geology and Geophysics Abstracts of Papers - Compiled by James R. Steidtmann

An unconformity at the base of the First Frontier sandstone in central Wyoming was initially inferred from chert pebble conglomerates mapped on outcrops. The westward increase in the number of missing ammonite zones, identified in the literature from U.S. Geological Survey outcrop studies, was attributed to erosion and non-deposition associated with the unconformity.

The unconformity has been mapped in the subsurface from well logs and shows westward erosion of 450 ft of section from the southwestern Powder River Basin to the eastern Wind River Basin. This is the strongest angular unconformity known in the Cretaceous of central Wyoming and is interpreted as evidence of a relatively strong period of paleostructural uplift and erosion in western Wyoming.

Shoreline and nearshore sandstones deposited on the unconformity by marine seas which transgressed westward may have stratigraphic oil and gas potential in some areas.

Acknowledgments and Associated Footnotes

1 William H. Curry, III: Consulting Geologist, Casper, Wyoming

© Wyoming Geological Association, 2015