PALEOECOLOGICAL ANALYSIS OF FURNACE GAP, A NEW UPPER ORDOVICIAN OPHIUROID LOCALITY IN PENNSYLVANIA

The Upper Ordovician Reedsville Shale is largely understudied in central Pennsylvania, although discussed at a larger scale by Bretsky in his extensive publications on Upper Ordovician ecology of the Central Appalachians. However, a new locality (Furnace Gap) near State College, Pennsylvania shows excellent preservation of species not commonly described, including conularids and ophiuroids. Also present are diverse species of brachiopods, bivalves, gastropods, trilobites, crinoids, trepostome bryozoans, and graptolites. Two lithofacies are present across 30 meters of exposure. The lower stratigraphic facies is a thinly bedded sandy siltstone, interbedded with mudstone. The majority of the fossil species are found in this facies. Preservation ranges from articulated ophiuroid and crinoid columnals to molds and casts of bryozoans and brachiopods. The upper stratigraphic facies is a medium-bedded sandstone interbedded with mudstone. Diversity in this facies is lower, but includes brachiopods and crinoids. The depositional environment is likely storm or turbidite dominated, with water depth decreasing over time. A locality in the correlative Martinsburg shale in Swatara Gap Pennsylvania was the subject of study by Lehman and Pope, who published an extensive list (75 species) of the fauna found. Preliminary comparisons between the two sites suggest compositional differences in the invertebrate community, with fewer species at Furnace Gap (approximately 10-20 species). Dalmanellid and sowerbyellid brachiopods, multiple crinoid species, and the trepostome bryozoan Amplexopora dominate the fauna at Furnace Gap. This faunal assemblage is distinctly different from Swatara Gap, where the trilobite genus Cryptolithus and sowerbyellid brachiopods are the most common taxa. The new Ordovician locality described serves to expand the comprehensive understanding of the Reedsville Shale in central Pennsylvania, as well as providing an opportunity to compare the fauna of a well-studied but previously unrivaled locality.