MAJOR AND TRACE ELEMENT GEOCHEMISTRY OF THE MARCELLUS SHALE, OTSEGO COUNTY, NEW YORK

Similar to the Barnett Shale of Texas, the Marcellus Shale is currently of interest to gas companies around the country because of its unconventional natural gas potential. Developed as an onlap disconformity in the Appalachian Basin, the Marcellus Shale has four main members. Primarily of interest is its lowermost member, the Union Springs, which lies stratigraphically above the Onondaga Limestone. Above the Union Springs is a brown argillaceous limestone-shale unit called the Cherry Valley. The Cherry Valley separates the Union Springs from the Chittenango in the eastern portion of the state, and the Oakta Creek to the west of Syracuse. The Marcellus Formation is overlain by sandstones-shales the Skaneateles and Panther Mountain formations. The trace element geochemistry of the Middle Devonian Marcellus Shale has been determined by ICP-MS from drill cores from Otsego County (395`). Samples were taken at an interval of approximately every 10-15 feet and significant vertical geochemical changes were seen throughout each section. In Otsego County the Marcellus Shale shows increases in SiO2, Na2O, TiO2, P2O5, Hf, Nb, and Zr and decreases in Ag, As, Ba, C(total), Cu, Ni, Pb, S(total), Se, Sr, U, and V from bottom to top. While several trace element redox indicators suggest dysoxic to oxic conditions, ratios become progressively less oxic with depth, with anoxic values for V/Sc within the Union Springs Member. These trends are consistently with a reduction in water depth due to filling of the eastern part of the basin. The Union Springs Member shows trace element enrichments relative to the Upper Continental Crust similar, but less pronounced, to those in the center of the basin including up to: (Ag-5.66x; As-2.42x; Cd-31.1x; Cu-3.12x; Hg-4.60x; Mo-26.4x; Sb-3.25x; Se-58.9x; U-2.96x; V-2.51x; Zn-2.66x). The total carbon content of the samples is general small (<2.0% of much of the section) only reaching values above 2% in the Cherry Valley (2.21-2.28%) and Union Springs (2.93-7.79%) members. High total carbon values are strongly correlated with Ca, Sr, and LOI, as well as, Ag, Cd, Cu, Hg, Mo, Pb, Sb, and Se.