THE EIFELIAN-GIVETIAN BOUNDARY IN THE OATKA CREEK FORMATION, MARCELLUS SHALE OF WESTERN NEW YORK, BASED ON MAGNETIC SUSCEPTIBILITY

The Eifelian-Givetian (E-G) boundary (Middle Devonian) is defined by the appearance of the conodont Polygnathus hemiansatus and associated with the Kacák-otomari events; this horizon at the global section and stratigraphic point at Jebel Mech Irdane, Morocco, is above a black shale interval (otomari-shale) and the Late Eifelian Magnetic Susceptibility Event. The E-G boundary has not been well constrained in New York due to a lack of biostratigraphical control. Magnetic susceptibility (MS) of core and outcrop from the Marcellus Shale in western and central New York shows a rapid and significant rise above the base of the East Berne Member (top of the Cherry Valley Limestone) of the Oatka Creek Formation, which is similar to the MS shift seen in Morocco at the GSSP and other locations in Europe. We suggest that the E-G boundary is where this shift stabilizes, which is below the occurrences of Givetian shelly faunas in the David Elliot Bed and Halihan Hill Bed higher in the Oatka Creek Formation. The position of the MS shift at the base of the East Berne Member or higher suggests variable preservation of strata of the lower Oatka Creek Formation in the Appalachian Basin.