BLOSSBURG REVISITED: PALEOENVIRONMENTAL VARIATION OF AN ESPECIALLY FOSSILIFEROUS LATE DEVONIAN ALLUVIAL PLAIN DEPOSIT IN THE CATSKILL FORMATION OF NORTH-CENTRAL PENNSYLVANIA

Discovery of vertebrate fossils in the Upper Devonian Catskill Formation of north-central Pennsylvania began in the mid-19^th century along railroad outcrops near the towns of Blossburg and Covington. Recent highway widening along US 15 near these 19^th Century sites has produced a nearly continuous Catskill Formation exposure with abundant fossils and sedimentary features, making it well-suited for linking Devonian terrestrial ecologies and sedimentary processes. Red floodplain mudrock with evidence for desiccation and pedogenic overprinting (rootlets, desiccation cracks, and sparse caliche nodules) transitions into lithofacies that include >1-7 m thick lenticular sandstone bodies and inclined heterolithic strata interpreted as fluvial channel-bar complexes, and <1-m thick, sharp-based sandstones capped by desiccation cracks and rootlets interpreted as temporary channel-bar complexes (i.e. crevasse splays). Fossils occur in several discrete stratigraphic horizons spanning ~240 m of stratigraphic thickness. Invertebrate taxa include clusters of post-mortem, hydrodynamically transported Archanodon bivalve shell impressions preserved along sandstone channel bases. Vertebrate taxa include two genera of placoderms (Bothriolepis, Phyllolepis), an unidentified acanthodian, several taxa of sarcopterygian fishes, including a lungfish (Dipnoi indet.), Holoptychius, Sauripterus, a tristichopterid, cosmine-covered fragments of an osteolepid, and a palaeoniscid actinopterygian. Bothriolepis and Holoptychius were the most common taxa identified within each fossiliferous layer. Most vertebrate fossils are preserved as disarticulated and abraded plates, scales, and bone fragments in sandstone channel lags. Partly articulated, unabraded remains are preserved along channel-margins. Blossburg outcrops provide a useful reference section for regionally linking Catskill environments and ecologies. To the northwest near Tioga, Catskill outcrops record more distal, transitional marine environments with articulate brachiopods, Lingula, and fishes. To the southeast near Liberty/Steam Valley, Catskill strata reflect more proximal fluvial habitats with better drained floodplains and deeper channels and diverse fishes and terrestrial plants.