02304nas a2200205 4500008004100000245013600041210006900177300001200246490000800258520164800266653001401914653002001928653002001948653001501968653001201983100002001995700001602015700001602031856005102047 2006 eng d00aSnake Hill - Reconstructing Eastern Taconic Foreland Basin Litho- and Biofacies from a Giant Melange Block in Eastern New York, USA0 aSnake Hill Reconstructing Eastern Taconic Foreland Basin Litho a a201-2130 v2423 a

Exotic lithofacies and faunas have long been known from Snake Hill, eastern New York, USA. The faunally diverse, sandstone-dominated Upper Ordovician succession at Snake Hill sharply contrasts with surrounding tectonized sparsely fossiliferous distal shale. Re-examination of the Snake Hill section shows that it is a storm- and wave-dominated near-shore facies with a benthic fauna analogous to that of the younger Lorraine Group (Ashgillian) of central New York, and to that of the upper Martinsburg Group (upper Caradocian) of eastern Pennsylvania. Orthograptus ruedemanni Chron graptolites indicate that the Snake Hill succession is older than the surrounding tectonized, deep-water shale (Climacograptus spiniferous Chron). Snake Hill is best interpreted as a parautochthonous block in mélange originally deposited close to the shoreline of the emergent Taconic accretionary prism. Because the Snake Hill succession is sandstone-dominated, it is inappropriate to refer mudstone-dominated facies that underlie the western margin of the Taconic allochthon in the Hudson River valley region to the Snake Hill “Shale,” as has been done in the past. The thick (ca. 150 m), lithologically distinct succession at Snake Hill is therefore referred to as the “Snake Hill Formation.” The Snake Hill Formation is the only known example of proximal, near-shore facies deposited on the western side of the outer Taconic arc, and represents easternmost deposition in the Taconic foreland basin. The Snake Hill Formation is a unique occurrence, and thus is restricted to its type locality at Snake Hill, New York.

10aBiofacies10aBiostratigraphy10aLate Ordovician10aSnake Hill10aTaconic1 aEnglish, A., M.1 aLanding, E.1 aBaird, G.C. uhttp://dx.doi.org/10.1016/j.palaeo.2006.05.014