TRILOBITES 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 occur scattered throughout the Piedmont of New Jersey and Lower Hudson Valley of New York. These glacial erratics contain an assemblage of well-preserved trilobites belonging to: Burtonops cristatus (Hall 1861a), Anchiops anchiops (Green 1832), Calymene platys (Green 1832), Terataspis grandis Hall 1836b, Trypaulites erinus (Hall 1861a) and Coniproetus angustifrons (Hall 1861). The distinct lithology and trilobite assemblage identifies the source region of these glacial erratics as a narrow outcrop belt within the Schoharie Valley and Helderberg Mountains. This outcrop belt is a maximum distance of 200 kilometers from where the southern-most trilobite specimens were recovered. The Rickard Hill trilobite assemblage consists predominately of disarticulated cephala and thoraxes that were originally preserved as a post-mortem storm bed assemblage transported by wave and current activity prior to final burial and fossilization. A unique sequence of physical and chemical weathering during glacial erosion, transportation and deposition has preserved some anatomical elements of the Rickard Hill trilobites in high detail. These anatomical details provide an opportunity to reassess earlier taxonomic assignments of Lower Devonian trilobites currently known from the Schoharie Formation of New York State and stratigraphic equivalents in nearby regions. Because the source outcrop and recovery locations can be identified, the Rickard Hill trilobite erratics provide an excellent proxy to model Wisconsinan glacial ice advance and retreat through the Lower Hudson Valley of New York and New Jersey Piedmont.