EVALUATING THE PROVENANCE FOR THE SHARP MOUNTAIN MEMBER OF THE PENNSYLVANIAN POTTSVILLE FORMATION, APPALACHIAN BASIN

The Pottsville Formation (Fm.) of the Appalachian Basin is a Pennsylvanian-aged siliciclastic deposit with lesser amounts of coal and limestone. It is subdivided into three members: Tumbling Run, Schuylkill, and Sharp Mountain (in ascending order). The Tumbling Run and Schuylkill Members are present in the southern anthracite field of Pennsylvania. The Sharp Mountain Member (SMM) occurs in the southern and northern anthracite fields, as well as in isolated patches throughout the Allegheny Plateau towards the west. The Pottsville Fm. is thought to be generally derived from an orogenic source to the modern-day southeast. However, previous studies of paleo-flow indicators within the fluvial deposits of the Pottsville Fm. demonstrate that the SMM was alternatively sourced from the cratonic interior to the north. In this study, 21 samples from the Pottsville Fm. were collected from conglomerate-bearing outcrops across eastern and central Pennsylvania for provenance analysis in an attempt to evaluate the influence from these two source areas on the different members. Hand samples were slabbed with a tabletop wet saw and examined with a Dino-Lite Edge, 5MP digital microscope with polarizing lens. Randomized point counting (n>500) for each sample was conducted on grains to determine the relative proportions of quartz, feldspar, and lithic fragments (QFL; n=9975). Results indicate that clasts within the SMM are predominantly composed of quartz (~97%), whereas the other members have relatively higher proportions of lithic fragments (~31%). These findings independently support the previous hypothesis of the SMM being derived from the stable cratonic interior, as opposed to the tectonically active orogenic source. This study has implications for understanding the evolutionary history of the Appalachian Basin during the Pennsylvanian.