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Changing Views of Lower Mississippian Stratigraphy of the Central Appalachians – Identification and Stratigraphic Expression of a Previously Unrecognized Early Mississippian Lowstand

Matchen, David L.
Concord University, Athens, WV

Interpretation of the Mississippian Black Hand Sandstone of central Ohio as incised valley fill requires reconsideration of the existing depositional models, and stratigraphic framework for the Lower Mississippian section of the Appalachians. These models support an overall pattern of southwestward progradation and are constrained by biostratigraphic data. Detailed examination of the Black Hand suggests that it was deposited in an incised valley by a north-flowing, braided-stream system. This, in turn, requires that the Lower Mississippian should be subdivided into two depositional sequences: Lower Mississippian 1 (LM1) and Lower Mississippian 2 (LM2).

Relative sea level (RSL) would have to drop a minimum of 145 feet to accommodate the Black Hand. A drop of this magnitude should produce a recognizable sedimentological signature throughout the basin. The Mississippian Burgoon and Big Injun sandstones are the eastern equivalents of the Black Hand. In some areas they overlie redbeds that may represent the highstand systems tract of sequence LM1. The Big Injun and Burgoon represent the lowstand and transgressive systems tracts of LM2. The RSL drop can be observed in Mercer County, West Virginia. The Lower Mississippian in this area is comprised of the marine Price Formation and the terrestrial Maccrady Formation. The contact between these two formations represents the sea level drop. Evidence for this sea level drop can be found throughout the central Appalachian basin. This requires that previous interpretations of a homogenous highstand throughout the Early Mississippian must be reconsidered.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004