Stratigraphic Framework and Regional Subsurface Geology of Upper Cretaceous Through Lower Eocene Rocks in Wind River Basin, Wyoming

Dianna Gentry Hogle, Richard W. Jones

A detailed stratigraphic study of over 6,000 m of Upper Cretaceous through lower Eocene sedimentary rocks in the Wind River basin, Wyoming, has refined and expanded previous work and conclusions. A much larger data base than previously available was assembled to include a correlation net of 325 geophysical well logs, 36 drill holes with palynological dates, lithology logs of drill holes, and limited surface exposures. The most significant results and conclusions from this study are summarized below. (1) The lower part of the Mesaverde Formation intertongues with marine sandstones and shales of the upper Cody Shale to the east and with marine sandstones of the lower Mesaverde Formation in the Big Horn basin to the north. (2) An unconformity between the Mesaverde and Fort Union Formatio s in the southwestern part of the basin can be traced into the subsurface. (3) During the latest Cretaceous and Paleocene, over 2,100 m of Lance Formation and over 2,700 m of Fort Union Formation were deposited in the northeastern part of the basin. Ponding during the Paleocene is demonstrated by correlation and subsurface mapping of over 900 m of shale and siltstone in the Waltman Shale Member of the Fort Union Formation. (4) The Lance and Fort Union Formations can be mapped in the subsurface throughout much of the basin. The Lance Formation pinches out in the western part of the basin. (5) Coal beds can be traced for short distances in the subsurface; coal bed occurrence is documented for the Mesaverde, lower Fort Union, and Meeteetse Formations in the southwestern, northern and centra , and northwestern parts of the basin, respectively.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.