Structural Implications on the Deposition of the Upper Freeport Coal Bed in Eastern Greene County, Pennsylvania

Abstract

The orientation, geometry, thickness, and quality of the Upper Freeport coal bed suggests that syndepositional tectonic activity influenced the accumulation of peat and its laterally equivalent sediments. Both strike-parallel and strike-normal structures appear to influence the deposition of the Upper Freeport coal bed. Strike-parallel structures are faults that were active during the Carboniferous, but do not penetrate into the Carboniferous section. The Carboniferous rocks at the surface within the study area reflect deeper structures as a series of gentle synclines and anticlines. The Upper Freeport coal bed was deposited as a domed peat across the Belle Vernon anticline, which represents the upthrown side of a syndepositionally active deep fault. Laterally equivalent fluvial channel sediments were deposited on the downthrown side of the structure, represented at the surface by the Waynesburg syncline. The influence of syndepositionally active faults on the distribution, thickness, and quality of the Upper Freeport coal bed is similar to the previously reported influence of contemporaneous growth faults on the distribution and thickness of Carboniferous coal beds in Kentucky and Alabama. Strike-normal features also influence the position, geometry, and thickness of the Upper Freeport coal bed. The strike-normal features appear to be produced by deep strike-slip faulting. Amore » major no-coal zone within the Upper Freeport coal bed lies within and parallel to the trend of a cross-strike discontinuity within the study area.« less