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The AAPG/Datapages Combined Publications Database

Earth Science Bulletin (WGA)

Abstract


Earth Science Bulletin
Vol. 15 (1982), No. 1. (Annual), Page 132

Abstract: Subsurface Stratigraphic Correlations of Some Upper Cretaceous and Lower Tertiary Rocks, Northern Green River Basin, Wyoming

B. E. Law,1 D. J. Nichols2

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

Subsurface studies of some Upper Cretaceous and lower Tertiary rocks in the northern Green River Basin, including Hoback Basin, indicate that major stratigraphic revisions may be necessary. In the Merna area of the northern part of the basin, the Upper Cretaceous Bacon Ridge Sandstone and overlying Cretaceous rocks are about 12,000 ft (3,658 m) thick and range in age from late Coniacian—early Santonian to late Maestrichtian. This sequence of rocks thins in a southeast direction to about 4,500 ft (1,372 m) near the Rock Springs uplift where it ranges in age from late Santonian to middle Maestrichtian. The most useful stratigraphic marker in this predominantly nonmarine sequence is the Ericson Sandstone. The Ericson is easily recognized in cores by a distinctive combination of mineralogy, grain size, texture, sedimentary structure, and color. In well logs, the Ericson can be traced from the Rock Springs uplift to the Hoback Basin, where it appears to be lithologically equivalent to rocks that some have called the “Mesaverde sandstone”

Well-log correlations and palynological data from cores show that the Cretaceous-Tertiary contact is unconformable and is as much as 3,000 ft (914 m) stratigraphically higher in the sequence than previously published work has indicated. In the structurally deeper parts of the basin, the oldest Tertiary rock unit is a 1,300 ft (396 m) thick unnamed sequence of interbedded sandstones, siltstones, and mudstones that contains Paleocene palynomorphs. This unnamed unit is conformably overlain by the Paleocene Fort Union Formation in the deeper parts of the basin, but near the perimeter of the basin, the contact is unconformable and the unnamed unit is truncated, and is, therefore, not exposed.

Acknowledgments and Associated Footnotes

1 B. E. Law: U.S. Geological Survey, Denver, Colorado

2 D. J. Nichols: U.S. Geological Survey, Denver, Colorado

© Wyoming Geological Association, 2015