--> --> Abstract: The Upper Cretaceous Lewis Shale of South-Central Wyoming: An Analog to Deep-Water Gulf of Mexico Turbidite Reservoirs, by David R. Pyles and Roger M. Slatt; #90914(2000)

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David R. Pyles1, Roger M. Slatt2
(1) Colorado School of Mines, Golden, CO
(2) Colorado School of Mines

Abstract: The Upper Cretaceous Lewis Shale of south-central Wyoming: An analog to deep-water Gulf of Mexico turbidite reservoirs

A detailed study of outcrops, cores, and well-logs in the Upper Cretaceous Lewis Shale of south-central Wyoming indicate that unconfined sheet sandstones, confined channel sandstones, and associated thin-bedded turbidites are comparable to some of those in the deep-water Gulf of Mexico.

A high-frequency sequence stratigraphic framework was constructed for the Lewis Shale on regional (50 mile long) cross sections. Fourth-order lowstand systems tracts within the Lewis can be divided into basin floor fans, slope fans, and prograding complexes. The basin floor fans comprise continuous thick-bedded sandstones and thin-bedded mudstones that bi-directionally downlap the basin floor. The sandstones are mostly composed of complete to amalgamated Bouma sequences with thick Ta intervals. Slope fans comprise channelized, discontinuous sandstones, thin-bedded continuous sandstones, and continuous mudstones that downlap the basin floor fan and onlap the slope. The channels are filled by debris flow beds and Bouma sequences with thick Tc intervals and shale rip-up clasts. Prograding complexes comprise thin-bedded, continuous sandstones and mudstones that downlap the slope fan and basin floor fan and onlap the upper slope and shelf. The sandstones comprise thin, base-absent Bouma sequences containing Tb-Tc intervals.

Outcrops of the Lewis Shale provide a rare opportunity to study stratigraphic features useful for characterizing some deep-water deposits in the Gulf of Mexico.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana