DID A TECTONIC UPLIFT AND BASALTIC WEATHERING ENHANCE NUTRIENT DELIVERY TO THE MIDDLE ORDOVICIAN OCEANS?
In the Appalachian basin, the MDICE at Clear Spring occurs within shallow tidal flat facies with peak δ13C values (+1‰) that span a lithologic shift from peritidal carbonates of the Pinesburg Station Dolomite (‘Knox-Beekmantown Group’) to gastropod-bearing fenestral limestones of the overlying Row Park Formation (St. Paul Group). The Row Park transitions into restricted lagoonal facies of the New Market Formation, and the entire Clear Spring MDICE section appears conformable based on conodont-apatite based 87Sr/86Sr and facies succession. Further south, an erosional surface known as the Knox Unconformity is observed at the Collierstown and Rocky Gap sections and the MDICE is not present. Missing time is indicated not only by δ13C and physical stratigraphy but also by rapid shifts in the εNd and 87Sr/86Sr curves. Furthermore, our εNd and 87Sr/86Sr data show a correlation between the MDICE and a significant continental weathering shift toward ‘juvenile’/basaltic values. These correlations suggest a potential link between the MDICE, change in relative sea level, and increase in basaltic weathering, possibly due to the Taconic uplift. We aim to use a carbon cycle box model to further test the hypothesis that weathering of basaltic rocks with high phosphorus content could invigorate primary productivity during Ordovician biodiversification events.