--> Abstract: Architecture of a Tide-Influenced Delta in the Frontier Formation of Central Wyoming, USA, by B. J. Willis, J. P. Bhattacharya, S. L. Gabel, and C. D. White; #90937 (1998).

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Abstract: Architecture of a Tide-Influenced Delta in the Frontier Formation of Central Wyoming, USA

WILLIS, B. J., J.P. BHATTACHARYA, S. L. GABEL, and C. D. WHITE, Bureau of Economic Geology, The University of Texas at Austin

Summary

The Upper Cretaceous Frewens Castle Sandstone in the lower Belle Fourche Member of the Frontier Formation in central Wyoming, USA, is composed of two elongate deltaic sandstones that overlap along a southeasterly trend. These are interpreted to be deposits of tidal ridges formed on the front of a prograding delta. These sandstones are superbly exposed in large cliffs. Sandstone bodies coarsen upward and fine away from their axes, have gradational bases and margins, and have eroded tops overlain abruptly by marine shales. The deposits change upward from thinly interbedded sandstones and mudstones, to meter-thick heterolithic cross bedsets, and finally to meters-thick sandstone-dominated cross-strata. Internal bedding within sandstones, dipping steeply seaward, has more gradual dips along strike away from the sandstone-body axis. The facies show abundant evidence of tidal modulation of depositional flows. Detailed mapping of stratal geometry and facies across these outcrop walls shows a complex heterolithic internal architecture that would complicate hydrocarbon production from similar tidal reservoirs.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah