EVIDENCE FOR A SHALLOW WATER APPALACHIAN BASIN, NEW YORK STATE

Developed along the western margin of the uplifting Taconic Mountains; the Appalachian Basin (AB) is a depressional feature of eastern North America that extends from the NE tip of Alabama, to its northern extremes in Quebec and Ontario. The AB remained the depositional center for eroded sediment from the Taconic Highlands and surrounding areas throughout much of the Paleozoic. Commonly believed to mimic classical deepwater depositional environments, geochemical and textural features of the Ordovician Utica Shale and Devonian Marcellus Shale of New York., are suggestive of a shallow-oxygenated water deposition within the AB, intermittent with periods of anoxic conditions. ICP-MS analysis of drill cores and cuttings reveal a general depletion in major and trace elements within the Utica Shale, while the Marcellus Shale yields a common enrichment in trace elemental values; when normalized to UCC estimates. Concentrations of CaO are enriched within the Utica and Marcellus Shale save the oldest member of the Marcellus, which shows lower concentrations of CaO. REE abundances differ between the two units; the Utica Shale shows lesser REE values, while Marcellus averages show a general enrichment in REE values, when normalized to PAAS estimates. However, a negative Ce anomaly exists within both formations, indicative of a shallow water setting (Alibo, 1998). Paleo-redox indicators U/Th, Ni/Co, and Mo of both units suggest that each formation was deposited in oxic conditions; excluding the Union Springs member. Microfabric analysis of each formation reveals random orientation of clay flakes caused by bioturbation within the Marcellus, and the calcareous composition of the Utica. The presence of authigenic calcite/dolomite rhombs, fecal pellets, palynomorphs, and extensive bioturbation are all indicative of shallow water deposition. The occurrence of pyrite framboids and preferred orientation of clay flakes within the Union Springs imply an anoxic depositional environment. Geochemical and textural features of the Utica and Marcellus Shales suggest that both units were deposited in a shallow-oxic depositional environment within the AB. The features of the Union Springs illustrate deepening of the basin and interruption of oxic conditions prevalent in the basin throughout much of the Devonian.