High-Resolution Sequence Stratigraphy of Late Mississippian Carbonates in the Appalachian Basin, Implications for Compartmentalization of Reservoir Facies
Aus Al-Tawil and J. Fred Read
The Late Mississippian Newman/Greenbrier carbonates were deposited in the Appalachian foreland basin whose depocenter lay to the south and east of Kentucky, West Virginia and Virginia. Over 50 closely spaced detailed measured sections along with numerous wireline logs, biostratigraphic data, and lithologic markers are used to construct detailed facies cross-sections.
In the Newman limestone along the Cincinnati Arch, four sequences bounded by regional unconformities can be recognized. The lower three sequences contain one to eight oolite bearing disconformity bounded parasequences. Parasequences within sequences one to three, progressively onlap the Waverly and Cincinnati arches. These are dominated by shoal water ooid grainstone and lagoonal skeletal wackestone/mudstone facies, while eolianite quartzose peloidal grainstone facies are restricted to the lower two sequences. Sequence four is thicker and capped by a disconformity, but is internally conformable. It contains thick oolite units in the lower part (up to 10 m), open ramp skeletal packstone and shale (2nd order maximum flooding of the studied interval).
In the much thicker foreland basin sections in West Virginia, four sequences also can be defined. The lowstand deposits are characterized by red beds up-dip, locally thickened tidal flat facies down-dip, and thin grainstone tongues extending into the slope/basin facies. Within the sequences, parasequences lack bounding disconformities, and are dominated by open ramp skeletal packstone and shoal water ooid grainstone facies. Eolianite facies are common in landward parts of the lower two sequences.
The complex regional distribution and vertical compartmentalization of these multilateral oolitic reservoirs in both areas on this tropical ramp reflect tidal bar morphologies, differential regional subsidence patterns, coupled with 4th order moderate amplitude eustacy.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California