Permian outliers in western Kentucky

Two small, fault-bounded outliers of Lower Permian rocks occur in western Kentucky, midway between the Dunkard Basin and Midcontinent Permian outcrops, representing the only Permian rocks within a 600-km radius. The Kentucky Geological Survey drilled a continuous core into the outlier at Cap Mauzy Lake in 1975. Permian fusulinids (Triticites) occur at 59 m depth and the youngest Pennsylvanian spores at 119 m. Permian rocks comprise greenish gray shale and siltstone interbedded with micritic, argillaceous limestone that may be largely of fresh-water origin. Cyclicity prominent in Upper Pennsylvanian rocks is weakly developed. Lithology suggests a semi-arid, seasonal climate not conducive to peat formation. Oil-test drilling indicates a second Permian outlier in the Grove Center quadrangle about 13 km west of Cap Mauzy Lake. Log correlation indicates a thicker Permian succession, as much as 128 m. Although both outliers occur in grabens, evidence for concurrent tectonism is missing. These apparently are fortuitous remnants of a much larger deposit, and represent our only stepping stone between the Dunkard Basin and Midcontinent Permian rocks.