SEDIMENTOLOGY OF THE HIGH FALLS SHALE (SILURIAN), ROSENDALE, NY

The Upper Silurian High Falls Shale (HFS) is predominantly a red to brown shale, often containing thin arenaceous components, which outcrops extensively in Rosendale, NY area. It overlies the Upper Silurian Shawangunk Conglomerate (SC), and unconformably overlies the Ordovician Hudson River Shale (HRS) where the Shawangunk Conglomerate is absent. A distinct angular unconformity between the HFS and the HRS is observed in the Rosendale area. However, in the southern part of the Rosendale area, the HFS rests conformably over the SC. Near the Williams Lake Hotel, the outcropping surface of the HFS shows evidence of Pleistocene glacial activity in the form of well-preserved striations and grooves. The HFS is highly deformed and shows pronounced development of slaty cleavage. The deformation is attributed to the Acadian orogenic event. Primary hydrodynamic sedimentary structures along with conspicuous development of penecontemporaneous slumping indicate a shallow water terrigenous environment with intermittent influx of sand in a predominantly low energy depositional setting. At least two calcitic horizons of varying thickness, up to 50 cm. at the maximum, are observed within the shaly units. The origin of these calcitic bands in Rosendale area is under investigation.