Abstract: High Resolution Surface/Subsurface Correlation of Late Mississippian Carbonate Sequences in The Appalachian Basin

AL-TAWIL, AUS, and J. FRED READ

Up to six Late Mississippian carbonate sequences in the Appalachian foreland basin were deposited during the transition from early Mississippian greenhouse to late Paleozoic glaciation. Index fossils, regional cycle bounding disconformities, and shale markers form the basis for high-resolution correlation of closely spaced detailed measured outcrop and core sections. Gamma-ray and density logs from numerous closely spaced wells are used to extend this high resolution correlation into the subsurface. Clay-draped paleosols, red-beds, and shale markers give a distinctive signal on the well-logs, which allows for the regional mapping of these sequence boundaries across the basin.

Up-dip along the Cincinnati Arch in Kentucky shoal water oolitic grainstone and restricted carbonate mud facies dominate the lower three sequences, where depositional cycles are disconformably-bounded by paleosols. Open marine skeletal packstone facies transgress over the arch in the upper sequences.

In the Appalachian basin in West Virginia open marine skeletal packstone and shoal water grainstone dominate the depositional cycles. Sequences are bounded by regional red-beds equivalent to the major paleosols developed on the Cincinnati Arch. Tidal flat facies are locally well developed down-dip.

Differential subsidence in this active foreland basin along with the increased amplitude of eustatic fluctuations controlled the development of these depositional sequences, their component cycles, and the regional distribution and compartmentalization of facies within. Shoal water oolitic grainstone and restricted dolomite form the major reservoir facies in the basin.

AAPG Search and Discovery Article #90939©1997 AAPG Eastern Section and TSOP, Lexington, Kentucky