--> Late Mississippian Carbonate/Clastic Reservoirs, Appalachian and Eastern Illinois Basins: Response to 4th Order Eustasy, by A. Al-Tawil, L. B. Smith, and J. F. Read; #90986 (1994).

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Abstract: Late Mississippian Carbonate/Clastic Reservoirs, Appalachian and Eastern Illinois Basins: Response to 4th Order Eustasy

A. Al-Tawil, L. B. Smith, J. F. Read

Upper Mississippian reservoir facies of West Virginia, Kentucky and Indiana developed on a south-facing carbonate ramp influenced by the rapidly subsiding Appalachian and Illinois basins, and the Cincinnati and Waverly arches which separated them.

Renfro peritidal dolomites and St. Louis open marine muddy carbonates are overlain by lowstand redbeds in the northeast, a major caliche/karstic surface over the Waverly Arch in eastern Kentucky and a correlative conformity in western Kentucky.

The overlying Ste. Genevieve to Hardinsburg interval consists of depositional cycles that are 3 to 20 m thick. In West Virginia, cycles are composed of skeletal pelletal wackestone/mudstone overlain by ooid grainstone and some updip quartzose eolianite, and they are bundled into depositional sequences bounded by low stand redbeds. In Kentucky (over the arches) clastic units are minor, and major breaks are marked by caliche/breccia horizons. In the eastern Illinois Basin, dominantly carbonate cycles at the base become progressively mixed with siliciclastics toward the top of the interval. The seclastic-carbonate cycles are characterized by lowstand erosional disconformities, transgressive marine clastics, eolianites or dolomitic mudstone, and highstand ooid-peloid-skeletal grainstone. hese cycles do not show any obvious bundling into larger scale depositional sequences.

Regional variation in subsidence and clastic input, coupled with increasingly larger 4th order (100-400 k.y.) eustatic sea-level fluctuations, have influenced distribution of reservoir facies and masked 3rd order depositional sequences. This strong 4th order eustasy probably reflects the buildup of Gondwana ice-sheets.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994