DETRITAL HISTORY OF THE CONGLOMERATE MEASURES OF THE POTTSVILLE FORMATION IN THE CAHABA SYNCLINORIUM, SOUTHERN APPALACHIANS, ALABAMA
Clasts within the conglomerate units consist mainly of chert, sedimentary and metamorphic lithoclasts and lesser amount of volcanic lithoclasts. Medium-to-high grade metamorphic lithic fragments are dominant. Carbonate clasts are present, along with large fragments of chert that appear to be derived principally from the Cambrian-Ordovician Knox Group. Both rhyolite and basalt clasts are present in the conglomerate, as are argillaceous lithic fragments. Clast composition indicates a proximal orogenic source that includes elements of the Appalachian thrust belt and the crystalline core of the Appalachians. The low abundance of heavy minerals and abundance of ultra-stable minerals in the upper Pottsville sandstone reflects intense chemical weathering, which is consistent with an equatorial paleolatitude. The presence of rutile and garnet further suggests a medium- to high-grade regionally metamorphosed source in the southern Appalachians. Ongoing research on detrital geochronology and mineral chemistry will provide additional information on provenance of the upper Pottsville Formation.