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Abstract: High Resolution Sequence Stratigraphic Setting of Mississippian Eolianites, Appalachian and Illinois Basins, U.S.A.

AL-TAWIL, A., L.B. SMITH AND J. F. READ; Dept of Geol Sciences, Virginia Tech

Summary

Quartz-peloid eolianites are common in the Mississippian Chesterian succession, Appalachian and Illinois Basins. A high resolution sequence stratigraphic framework was generated using the available biostratgiraphy and close-spaced stratigraphic sections and core, and tracing regioal disconformities between the sections.

The eolianites are very fine to fine, quartz peloid grainstones of well rounded and abraded peloids, whole and broken ooids, skeletal fragments, and generally finer grained subangular quartz. Units are 1 to 8 m thick and from less than a kilometer to many kilometers wide. They have wedge sets of planar to tangential, pin-stripe, inversely graded laminae with dips of up to 20 degrees. Tops may be calichified. Some tops are intensely brecciated, and draped by green mudrock. Eolianite units backstep within the transgressive part of the Chesterian supersequence and are absent from the highstand part, which was siliclastie dominated and formed in a humid setting. Within the component sequences, the eolianites occur updip where parasequences are disconfomity-bounded. In the TST and early HST of sequences, the eolianites are transgressive, overlying the disconformity at the bases of the parasequences. In late HSTs, the eolianites are regressive, located downdip, overlie marine grainstone and are capped by regional disconformities. The abundance of these eolianites probably is due to the semi-arid setting and moderate amplitude eustasy reflecting onset of Carboniferous-Permian glaciation of Gondwana. Their reservoir potential of the eolianites is limited by tight packing and calcite cementation. Recognition of the eolianites is critical in developing the sequence stratigraphic framework because they indicate subaerial conditions as do the disconformities.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah