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The Shannon Shelf-Ridge Sandstone Complex, Salt Creek Anticline Area, Powder River Basin, Wyoming

By
R. W. Tillman
R. W. Tillman
Energy Resources Group Exploration and Production Research Laboratory Tulsa, Oklahoma
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R. S. Martinsen
R. S. Martinsen
Consultant Laramie, Wyoming
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Published:
January 01, 1985

Abstract

Two vertically stacked shelf-ridge (bar) complexes in the Shannon Sandstone member of the Cody Shale (designated upper and lower sandstones) crop out in the Salt Creek anticline of the Powder River Basin, Wyoming. The shelf-ridge complexes are composed primarily of moderately to highly glauconitic, fine-to medium-grained lithic sandstone and attain thicknesses of over 70 feet. The shelf-ridge complexes were deposited at least 70 miles from shore at middle to inner shelf depths by south to southwest-flowing shore-parallel currents intensified periodically and frequently by storms. Ridges in each sequence trend north-south, slightly oblique to current flow. A possible source of sediments for the shelf ridges was the Eagle Sandstone shoreline and deltaic deposits of southern Montana 200 miles to the northwest.

Eleven facies were defined in outcrop on the basis of physical and biologic sedimentary structures and lithology. Vertical and lateral changes in facies are relatively abrupt where observed in closely spaced outcrop sections, and, in general, facies are stacked in coarsening-upward sequences with Central Bar Facies commonly immediately overlying Interbar Sandstone Facies. Porous and permeable potential reservoir facies include: Central Bar Facies, a clean, cross-bedded sandstone; Bar Margin Facies (Type 1), a highly glauconitic, cross-bedded sandstone containing abundant shale and limonite (after siderite) rip-up clasts and lenses; and Bar Margin Facies (Type 2), a cross-bedded to rippled sandstone. These facies were formed by sediment transported and deposited in the form of medium- to large-scale troughs and sand waves on and across the tops of ridges by moderate to high energy

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Contents

SEPM Short Course Notes

Shelf Sands and Sandstone Reservoirs

R. W. Tillman
R. W. Tillman
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D. J. P. Swift
D. J. P. Swift
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R. G. Walker
R. G. Walker
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SEPM Society for Sedimentary Geology
Volume
13
ISBN electronic:
9781565762428
Publication date:
January 01, 1985

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