GEOLOGY OF WEST BLOCTON EAST QUADRANGLE, ALABAMA

We have conducted a detailed geologic mapping project of the 1:24,000 scale West Blocton East Quadrangle, Alabama with funds from the USGS EDMAP program. The quadrangle is located at the southern extent of the Appalachian Valley and Ridge province, encompasses Paleozoic sedimentary units containing economically important resources and information for timing and kinematics for Alleghenian structural development. Cambrian-Pennsylvanian strata in the quadrangle are contained in the Jones Valley and overlying Montevallo thrust sheets.

The Montevallo thrust sheet has been well mapped in the adjacent areas, but its geometry and structural features remained in question in the West Blocton East area. The thrust fault cuts through the area from southwest to northeast, bringing Pennsylvanian rocks over the Cambrian rocks. This indicates the Cahaba synclinorium and associated strata and structures are truncated by the Montevallo fault. The structures present through the area include a tight 35^o southwest-plunging anticline, synclines, and minor thrust faults that formed during the Alleghenian orogeny. The structures and bedding planes trend near-parallel to the thrust, averaging N30E. This provides new data on the nature of Appalachian thrusting in southern Alabama and units of economic interest. The rock units in the quadrangle and their importance include: Pennsylvanian Pottsville formation for coal, Cambrian Knox Group for limestone, and Cambrian Conasauga formation for natural gas production. The West Blocton East Quadrangle is located along the I-20/59 development corridor. Mapping of this quadrangle gives the Geological Survey of Alabama and the United States Geological Survey a detailed, 1:24,000 scale geologic map to improve future mining and infrastructure development planning involving these units.

The study area contains an unconformity between the Pennsylvanian Pottsville Formation and Cretaceous Coker Formation. The Coker Formation is a part of the Gulf Coastal Plain province which thickens to the southwest and thins to the northeast at its intersection with the Valley and Ridge province. We have measured a stratigraphic section of the Coker Formation and will conduct backstripping calculations to determine depositional and loading history of the Appalachian Basin in the study area.