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J.A. Toni Simo1, Michelle L. Stoklosa2, Jen L. Beal3, Greg P. Wahlman4
(1) University of Wisconsin, Madison, WI
(2) Univ. Wisconsin, Madison, WI
(3) University of Texas, Austin, TX
(4) BP-Amoco, Houston, TX

Abstract: Wolfcampian Shelf Margin Architecture: Hueco Group, Hueco Mountains, West Texas

The Upper Wolfcampian Hueco Group exposed in outliers west of the main Hueco Mountain escarpment shows a strike and dip section of a shelf margin. The exposures extend approximately 40 km and show 200 m of section. The shelf margin was part of the leeward side of the Diablo Platform during the final sedimentary filling of the Late Paleozoic Orogrande Basin. These outliers are excellent outcrop analogs for subsurface Wolfcampian reservoirs in the adjacent Permian Basin. Ten different limestone lithofacies have been recognized and grouped into five associations, and each placed in a carbonate shelf depositional model. The succession consists of a lower shallowing-upward sequence, followed by an upper aggradational to landward-stepping sequence. Superimposed are higher-frequency sequences with landward- and seaward-stepping packages. Platform margin collapse and deposition of breccias and allodapic limestones represent sequence boundaries. Detailed study of these basinal deposits show successive deposition of transported sediment and in-place carbonate deposition. Platform margin geometry varies along strike following collapse features. Transgressions eroded and reworked strata containing sequence boundary characteristics on the shelf, with karst features preserved only in slumped blocks. Early platform progradation consists of grain-supported bioclastic limestones. As the succession shallows phylloid algae-Tubiphytes buildups become more abundant and form a narrow band that onlaps the successive collapsed margin. The buildups separate thick sequences of shelf-margin grain-supported bioclastic limestones from resedimented carbonates and down-slope buildups. Stratal patterns, unconformities, and facies successions appear to be largely influenced by large-amplitude, high frequency sea level variations characteristic of icehouse periods.

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