POCONO PALEOCURRENTS IN PENNSYLVANIA AND MARYLAND
A combined petrographic, stratigraphic and sedimentological study was made of the Pocono formation (Mississippian) of Pennsylvania and Maryland to determine the paleocurrent system, source area, and paleogeography of Pocono time. Measurement of 5000 cross-bedding attitudes at 254 localities and studies of other current structures showed transport direction was toward the northwest. The paleoslope, reconstructed by contouring the moving average of the largest diameter of the 10 largest quartz pebbles at each outcrop, dipped west and northwest across Maryland, Virginia, West Virginia, Pennsylvania, and western New York. Tilt-corrected trends of 325 oriented plant remains in the anthracite region of Pennsylvania are about perpendicular to the regional current direction. Extrapolation of the size-distance curve of the pebble diameters, after adjustment for crustal shortening, indicated the vicinity of Atlantic City, New Jersey, as a probable source area. Stratigraphic studies, petrographic analyses, the paleocurrent pattern, and numerous current structures indicate that the Pocono formation was fluviatile and derived from clastic sediments and low-rank metamorphic rocks. Measurements of cross-bedding in Upper Devonian, Mississippian Mauch Chunk, and Lower Pennsylvanian strata at 35 localities showed that the current pattern is essentially the same as that of the Pocono. Calculations based upon the southeastward increase in pebble size, corrected for crustal shortening, showed the Pottsville (Lower Pennsylvanian) source area was a few miles south of Philadelphia and about 100 miles northwest of that of the Pocono. The source region had migrated toward the northwest.