AN OVERVIEW OF THE EXPOSED ORDOVICIAN-DEVONIAN SEDIMENTARY SUCCESSIONS IN ROSENDALE, ULSTER COUNTY, UP-STATE NEW YORK

The unique depositional conditions that formed the various sedimentary formations in Rosendale, NY have been subject to intense scientific scrutiny for the last decades. Interestingly, a variety of well-exposed lithological formations manifest a rich physical, chemical, and fossiliferous attributes both locally and regionally. Consequently, it is possible to infer that regional-scale processes such as sea-level variances could have affected the geological development of the sedimentary basin and subsequent lithofacies variation along the regional depositional trend. Undoubtedly, such processes resulted in the formation of the structural identity of the different rock formations present in Rosendale. Furthermore, the chronological formation of the Rosendale lithology encompassed Ordovician, Silurian, and Devonian time periods; which concords with current dating models for sedimentary bodies. However, the concrete circumstances in which these lithological formations were originated remain debatable. In particular, the behavioral influence of the Panthalassan Ocean over the paleo-Eastern seaboard remains unclear. Therefore, the formation of the macro and micro geological constituents of Rosendale could have been due to sea-level fluctuations in the region. Furthermore, at least two tectonic episodes namely the Taconic and Acadian orogeny deformed several units as evidenced by complex folding, faulting and development of pronounced angular unconformity between Ordovician Hudson River Shale (mostly dark-colored) and Silurian High Falls Shale (mostly reddish to brownish red). The basal contact of the High Falls Shale is generally considered to be situated near the base of the first red bed above the uppermost conglomerate containing quartz pebbles of the Shawangunk Formation. The upper contact of the High Falls Shale is gradational with the overlying Binnewater Sandstone. It is possible that the Panthalassan Ocean experienced transgression and regression events and provided major constraint to develop characteristic lithofacies associated with lower to mid-Paleozoic stratigraphy in Rosendale.