LITHOFACIES, STRUCTURE, AND GEOCHEMISTRY OF THE EXPOSED SEDIMENTARY ROCKS, ROSENDALE, NEW YORK

The lithostratigraphic units in Rosendale, Ulster County, New York, and vicinity, are of early-to-middle Paleozoic clastics, carbonates and, in places, mixed siliciclastic sequences. The shaley component, is the dominant lithology within the clastics; whereas the arenaceous clastics consistently maintain greater thickness than the conglomeratic unit. Minor chemical sedimentary deposits include chert and nodules found within the Port Ewen formation which have been reported to be phosphatic although this has been disputed; bedded chert is also associated with Kalkberg limestone and the Glenerie formation (a known ridge former). Exposed units, mostly deformed during the Devonian period by the Acadian Orogeny, are extensively thrust faulted, as well as folded, causing multiple repetitions of outcrop and increase the exposure as well as the effective thickness of the Upper Silurian through Lower Devonian units. Development of slaty cleavage, slickensides, and orthogonal joint-patterns in Hudson River shale and High Falls shale are observed in the outcrop. Many of the formations in the Rosendale area are highly fossiliferous and include both invertebrate and ichnofaunal assemblages. Other primary features observed in the exposed formations include ripple marks, mud cracks, cross bedding, sole marks, and penecontemporaneous slumping (in the High Falls shale). Depositional environments range from strictly continental to fluvio-deltaic to shallow marine with periodic incursions of the shallow transgressive sea. Representative geochemical data involving bulk oxides and trace elements point to both recycled orogen and active plate tectonic settings for the clastic units. Bulk oxide and trace element data were found to be useful for chemical fingerprinting of several successive carbonate units, particularly Rosendale dolostone, Whiteport dolostone, and the Manlius limestone; particularly based on Ca/Mg ratio, amount of Sr, Cu, Zn, V, and Ba. Tectonic overprinting and subsequent diagenetic events associated with both the Taconic and Acadian events, is believed to have resulted in vertical fractionation of trace elements such as Rb, Ba, Sr, Zr, Ti, Cr, La and Y within the various clastic units.