PALEOCEANOGRAPHIC CONTROLS ON THE DISTRIBUTION OF CONODONTS IN A PENNSYLVANIAN EPICONTINENTAL BLACK SHALE
Neodymium isotopes of conodont apatite and sedimentary geochemistry (nitrogen isotopes and molybdenum and uranium enrichment factors) suggest that an interplay of open-ocean upwelling and continental runoff led to distinct spatial and secular variations in watermass properties within the shallow Late Pennsylvanian Midcontinent Sea of North America. In particular, the intensity of terrestrial runoff influenced the flux of bulk organic matter to the sediment. Concurrent changes in watermass redox conditions not only drove authigenic enrichment of redox-sensitive trace elements across the basin, but also had a strong effect on the spatial distribution of various conodont taxa. The strongest influence on the distribution of conodont taxa appears not to have been water depth per se but, rather, watermass chemistry in the form of nutrients, turbidity, and/or dissolved oxygen levels.