The Glade sand and Clarendon sand are Upper Devonian shoestring sands occurring at relatively shallow depth, in most places not exceeding 1,500 ft (457 m). Both are producers of Penn Grade crude oil, having been discovered before the turn of the century. Data for this study are derived from four independent sources, namely the petrographic microscope, image analysis instruments, the X-ray diffractometer, and geophysical (nuclear and electric) log data. Special emphasis is given to grain shapes, grain sizes, primary and secondary mineral compositions (including matrix constituents), rock textures, and the relationship of permeability and porosity in thin section to geophysical data. Compositionally, the Glade and the Clarendon are very-fine to medium-grained low-rank grayw ckes with variable amounts of muscovite, biotite, chert, plagioclase feldspar, orthoclase feldspar, and carbonates. The Clarendon, however, is predominantly more silty throughout. Porosity in thin section is measured on the basis of its ratio to the total area of the rock being examined. Permeability, however, is described in terms of the relative interconnectivity of pore space and its tortuosity. In the end, correlation of these petrographic features with geophysical data aids in interpreting the rocks' characteristics.

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