ABSTRACT

In the area of investigation, T. 15-20 N., R. 2 E.-3 W., the Hunton Group consists almost entirely of limestone and dolomite; minor amounts of sand and shale are included. Areal extent of the Hunton was determined by erosion before deposition of the overlying Woodford Shale. Only Silurian rocks of the Hunton Group are present, and the Hunton was eroded from the northern parts of the study area. The Hunton Group apparently is conformable upon the Sylvan Shale.

At many places the Hunton was eroded to a karstose topography, in conjunction with evolution of a dendritic stream drainage system. Solution porosity and dolomitization seem to be particularly well developed where stream valley "heads" were cut into the karst surface.

Folding and faulting, as illustrated by structure of the top of the Sylvan Shale, were determinants in development of porosity and entrapment of hydrocarbons within the Hunton Group. Dolomitization apparently is associated with ground water that migrated through faults and fractures.

Four types of hydrocarbon-trapping mechanisms can be described from the Hunton. Traps are closely related to (1) folding, (2) faulting, (3) stratigraphic changes in lithology, and (4) a combination of folding and stratigraphic changes. No production has been discovered to be related directly to "pinchouts" at the subcropping edge of the Hunton.