BRACHIOPODS FROM THE RICKARD HILL FACIES OF THE SAUGERTIES MEMBER OF THE SCHOHARIE FORMATION (LOWER DEVONIAN), HELDERBERG MOUNTAINS, NEW YORK: A CASE STUDY FROM GLACIAL ERRATICS

Glacial erratics belonging to the Rickard Hill Facies of the Saugerties Member of the Schoharie Formation (Lower Devonian Period, Upper Emsian Stage) occur scattered throughout the Piedmont of New Jersey and Lower Hudson Valley of New York. These glacial erratics contain a diverse benthic and nektonic assemblage of well-preserved invertebrate taxa from this interval. Examination of taxa at outcrop exposures is difficult due to the very hard nature of this unit. A unique sequence of physical and chemical weathering during glacial erosion, transportation and deposition provides an excellent opportunity for a reevaluation of the fauna of this unit in high detail from the >150 erratics collected thus far (ranging in size from fist-sized cobbles to blocks up to over a meter on a side). Current studies underway include examination of nautiloid cephalopods and trilobites. Brachiopods, the most abundant and diverse group of fossils in the erratics, are summarized here.

The distinct lithology and fossil assemblage identifies the source region of these glacial erratics as a narrow outcrop belt within the Schoharie Valley and Helderberg Mountains southeast of Albany, NY. This outcrop belt is a maximum distance of 200 kilometers from where the southern-most brachiopod-rich erratics were recovered. The Rickard Hill brachiopod assemblage consists predominately of internal and external molds of brachiopods that were concentrated as a highly time-averaged, post-mortem storm bed assemblage transported by wave and current activity prior to final burial and fossilization.

Boucot and Johnson (1968) list presence/absence-level data for 31 species of brachiopods from the Schoharie Fm. in eastern NYS, with an additional 5 more from the correlative Bois Blanc Fm. in west-central NYS, bringing the total to 36 species for the Upper Emsian interval in the area. We have to date identified ~20 species from the NJ Rickard Hill erratics. Examination of >150 erratics allows for not only presence/absence-level data, but for estimations of abundance of the various brachiopod species as well. Devonatrypa reticularis is the most abundant brachiopod in the assemblage, often occurring as multiple specimens per erratic. This is followed in decreasing abundance by a suite of strophomenid, spiriferid, and pentamerid taxa.