WHO IS THE FERROUS OF THEM ALL?: USING IRON SPECIATION AND OTHER PROXIES TO CONSTRAIN THE ROLE OF ANOXIA IN PRESERVING SOFT-BODIED FOSSILS FROM THE GIVETIAN OF UPSTATE NEW YORK

Previous work supports a link between fluctuating redox conditions and the Late Devonian Mass Extinction. Reduced oxygen availability can lead to increased preservation potential of soft-bodied organisms. Several occurrences of soft-bodied fossils are known during this time, however, potential links between exceptional preservation and redox conditions have not been studied. Here we consider previously undescribed soft-bodied discoidal fossils the Givetian of upstate New York. Interestingly, the typical Phanerozoic shelled taxa that dominate the intervals above and below these fossils are almost entirely absent alongside these enigmatic disks . fossils are generally preserved as cast and molds and occur in both negative relief on bed bottoms and in positive relief on bed tops. We see these fossils occurring primarily at two localities, Sampson State Park (SSP) and Butlers Hollow (BH), which are directly correlative. Fossil samples were collected both from float and with constrained stratigraphic heights to facilitate correlation with geochemical data. Geochemical samples were collected prior to, during, and after intervals of soft-bodied preservation, with higher sampling resolution in areas of fossil occurrence. These fossils are preserved in finely laminated shales which are ideal for geochemical analysis, using proxies such as iron speciation and redox-sensitive trace metal concentrations (i.e. Mo, Mn, V). Our inorganic geochemistry data from SSP suggests the interval of soft-bodied fossil preservation is concurrent with bottom water and/or pore water non-sulfidic anoxia, while the areas where soft-bodied preservation is absent are more reducing. Recently generated data from BH will examine the spatial extent of these changes. Taphonomic comparisons between these two localities suggest a discrepancy in the quality of the preserved specimens. Combined fossil and geochemical data suggest variable redox conditions likely contributed to the anomalous occurrence of soft-bodied preservation during this interval. This data provides support for hypotheses suggesting a link between oxygen availability and exceptional preservation as well as an association between fluctuating redox conditions and biotic turnover in the Middle and Late Devonian.