Sinistral transpression along previously existing faults, Appalachian Basin, Ohio

Abstract

Recent mapping of Silurian and Devonian strata in Ohio shows a large-scale, regional structure pattern roughly parallel to the Cambridge cross-strike structural discontinuity (CCSD) south of the Akron-Suffield-Smith Township fault system and east of the CCSD. This pattern is counterintuitive to the apparent strike of the Appalachian Basin slope, suggesting movement of previously existing faults.

Interpretation of two speculative seismic surveys in Ohio shows two prominent features in Belmont and Harrison Counties. These structural features illustrate a history of Cambrian extension followed by compression, similar to Killbuck Dome in Holmes County. The area in Belmont County shows down-to-the-east extension faulting followed by compression shortly after deposition of the Ordovician Trenton Limestone. Trenton fold reflector patterns do not continue high into the overlying Cincinnati Group while reflector patterns in the overlying Silurian horizons appear as a sag. In Harrison County, the Cadiz anticline is clearly illustrated as a feature that initiated as a graben during Cambrian extension and then reactivated as a compressional feature during the Appalachian orogeny. The Cadiz anticline uplift is evident on the Pennsylvanian Lower Freeport coal structure map.

The faults identified from seismic lines and the structural trends from the recent Paleozoic mapping suggest sinistral transpression along previously existing faults which are subparallel to the CCSD. Antithetic, roughly east–west faults were reactivated as well. Most of these reactivated faults do not propagate high into the Paleozoic section, but they produced folds and highly fractured zones within the Paleozoic section.

AAPG Datapages/Search and Discovery Article #90258 © 2016 AAPG Eastern Section Meeting, Lexington, Kentucky, September 25-27, 2016