SCHIEBER, JURGEN
Department of Geology, Univ. Texas at Arlington, Arlington, TX ([email protected])

Abstract: Sequence Stratigraphy in the Chattanooga Shale: Unraveling the Depositional History of a Black Shale Succession

The Late Devonian Chattanooga Shale of Tennessee and Kentucky constitutes the distal end of the Catskill Delta clastic wedge. Although conventionally thought of as deposited in deep stagnant waters, in the study area it was deposited within the reach of storm waves and contains evidence of benthic life.

Detailed examination of outcrops and drill cores has revealed a series of areally extensive erosion surfaces within the Chattanooga Shale. These erosion surfaces are sequence boundaries and reflect drops of sea level accompanied by erosion of parts of the underlying black shale succession. New black shale blankets were deposited during subsequent sea level rises. Tracing these erosion surfaces and the enclosed black shale sequences across the study area provides the foundation for a 14-fold stratigraphic subdivision. Correlation of sequences and sequence boundaries was accomplished through detailed outcrop and core descriptions, matching of lithologic and sedimentary features, and gamma ray spectrometry.

The currently studied part of the succession was deposited along the comparatively shallow Cincinnati Arch region. There, erosion at sequence boundaries provides for lithologic, sedimentologic, and compositional contrasts (gamma ray spectrometry) that facilitate their recognition. In the deeper water areas east (Appalachian Basin) and west (Illinois Basin) of the Cincinnati Arch, sequence boundaries are most likely not marked by erosive features. Their recognition in these deeper water settings is a remaining challenge before we can arrive at a comprehensive sequence stratigraphic framework for the Late Devonian black shale complex of the eastern US.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas