THICKNESS AND FACIES VARIATIONS IN PALEOZOIC HOST STRATIGRAPHY OF THE BESSEMER TRANSVERSE ZONE, ALABAMA APPALACHIANS: POSSIBLE CONTROLS ON KINEMATIC EVOLUTION

The Bessemer transverse zone, the southernmost transverse zone in the Appalachian allochthon, occurs near the junction of the Appalachian-Ouachita orogenic systems. The northwest-southeast trending transverse zone encompasses an area approximately 16 km wide by 77 km long, extending from the Appalachian Plateau southeastward into the Piedmont Physiographic Province. The Paleozoic stratigraphy of the Bessemer transverse zone has been the subject of decades of investigation.

Current research involves the compilation of previous stratigraphic work and the palinspastic restoration of the stratigraphy into pre-orogenic configurations. Palinspastic restoration of the Bessemer allochthon permits three-dimensional stratigraphic modeling of Appalachian-Ouachita continental margins and foreland basins. Syn- and post-deposition stratigraphic controls on the kinematic evolution of the Bessemer transverse zone may be elucidated through the use of palinspastically-restored stratigraphic data.

Stratigraphic compilation revealed three-dimensional thickness and facies variations throughout the Paleozoic succession, in each thrust sheet of the Bessemer transverse zone. Thickness and facies changes in the Silurian Red Mountain Formation occur near fault terminations and displacement transfer zones in the Opossum Valley, Jones Valley and Helena thrust sheets. The Devonian Chattanooga Shale exhibits facies changes near a displacement transfer zone in the Opossum Valley hanging wall, while facies and thickness variations occur near a Jones Valley thrust displacement transfer. Thickness changes in the Mississippian Fort Payne Chert occur proximal to terminations in the Jones Valley and Helena thrust sheets. Continuing analysis may reveal crosscutting relationships establishing timing of sedimentation vs. thrust initiation and hence, possible stratigraphic controls on thrust development.