About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

Earth Science Bulletin (WGA)


Earth Science Bulletin
Vol. 18 (1985), No. 1. (Annual), Page 64a

Abstract: Previous HitDeltaicNext Hit Systems in the Early Cretaceous Fall River Formation, Southern Powder River Basin, Wyoming

Donald L. Rasmussen,1 Connie J. Jump,2 Katherine R. Wallace3

Early Cretaceous strata of the Fall River Formation in the southern Powder River Basin of northeast Wyoming contain Previous HitdeltaicNext Hit sandstones and shales which were deposited in a slowly subsiding coastal area of the epicontinental “Thermopolis sea”. The formation has been subdivided into five mappable units, with the lower four units related to specific Previous HitdeltaicNext Hit systems. The second-oldest Previous HitdeltaicNext Hit system is the largest and most complete in the study area, and is the focus of this paper.

Electric log patterns were used as an aid in determining the depositional Previous HitenvironmentsNext Hit of Fall River sandstones in the several thousand wells that penetrated the formation. Sandstone depositional Previous HitenvironmentsNext Hit recognized in the Fall River Previous HitdeltaicTop system include: delta plain facies (interdistributory bay and crevasse splay); distributary channel facies (channel fill bar, point bar, and clay plug; and crevasse splay channel fill); delta front facies (proximal and distal delta front sandstones); and prodelta facies (shaly prodelta sandstones and siltstones). Of significant importance in the exploration for petroleum in the Fall River Formation of the southern Powder River Basin is that specific sandstone facies and trends can be predicted by using available subsurface data.

Acknowledgments and Associated Footnotes

1 Donald L. Rasmussen: Intermontane Research, Inc., Pine, CO.

2 Connie J. Jump: Mobile Oil Corp., Denver, CO

3 Katherine R. Wallace: Apache Corp., Denver, CO.

© Wyoming Geological Association, 2015