STRATIGRAPHY AND SEDIMENTOLOGY OF THE HUDSON RIVER SHALE (ORDOVICIAN), ROSENDALE, NY

The Ordovician Hudson River Shale (HRS) is the oldest exposed rock unit in Rosendale, NY area, and consists mostly of black to dark gray, very thinly laminated shale, ranging from purely argillaceous to slightly arenaceous. The HRS is unconformably overlain by Silurian Shawangunk Conglomerate (SC). However, in places; particularly in the northern part of the study area, the SC is absent and the HRS is unconformably overlain by the High Falls Shale (Silurian). Well-developed slaty cleavage along with highly deformed strata characterizes the HRS. A highly fossiliferous, slightly calcareous zone, mostly with Brachiopods, has been observed near the Williams Lake Hotel, Rosendale, NY. For the most part, however, the HRS represents a deep water environment, with an intermittent influx of coarser clastics. The overall lithological characteristics associated with the HRS suggest that it correlates to the Martinsburg Formation outcropping to the south and west. Pronounced development of the slaty cleavage and deformed strata in the HRS is attributed to the Taconic Orogenic Event as well as the subsequent Acadian Orogenic Event which refolded the HRS.