A MULTI-PROXY INTERPRETATION OF BOTTOM WATER OXYGEN CONDITIONS THROUGH THE FRASNIAN-FAMENNIAN BIOEVENT IN NEW YORK STATE

A dynamic record of bottom water oxygen conditions through Frasnian Famennian (F-F) bioevent, identified in western New York State, can be recognized through ichnological, sedimentological and geochemical proxies. The F-F boundary is preserved within the Hanover Formation and at four localities is examined in detail at high resolution to reveal a complex oxygen history below, within and stratigraphically above the unit of the Upper Kellwasser Event. Within these intervals, a surprising ichnogeneric diversity is recognized. Variation in burrow size and relative burrowing intensity, quantified using inchnofabric index values, allows relative oxygen levels to be inferred. From these data, coupled with trace metal and pyrite framboid data, bottom water oxygen levels appear to have shifted very rapidly from oxic to anoxic and back several times leading into the Kellwasser Event. The redox signal through the Upper Kellwasser black shale interval is quite variable despite its seemingly homogeneous lithologic composition. Several black shale intervals stratigraphically above the Upper Kellwasser event also record rapidly fluctuating and variable redox conditions.