A COMPARISON OF KATIAN-SANDBIAN (UPPER ORDOVICIAN) NORTH AMERICA AND BALTOSCANDIA USING HIGH-RESOLUTION NEODYMIUM ISOTOPES DERIVED FROM CONODONTS

During the late Sandbian-early Katian, Eastern North America experienced a significant lithological and faunal shift from warm-water, epicontinental sea conditions to cool-water, open-ocean conditions. The prevailing hypothesis that has been proposed to explain this change is known as the “tectonic forcing” hypothesis. This hypothesis states the Taconic Orogeny formed high relief areas that experienced rapid weathering rates, which led to lithospheric loading and dilution of the biogenic carbonate input within the basin. Lithospheric loading resulted in basinal deepening, which allowed cooler oceanic waters to invade the epicontinental sea.

This research tests if regional tectonics due to the Taconic Orogeny played a significant role in changing the water masses from warm to cool water conditions by comparing high-resolution Neodymium isotope data derived from conodont samples collected from Fort Payne, Alabama and the Siljan District, Sweden. We will present the field studies conducted at the two sampling sites with an emphasis on explaining the importance of each site, comparing the regional geology of the two sites, correlating coeval stratigraphic intervals, and outlining how future Neodymium analysis will benefit this research project. The comparison and correlation between the two sites will provide a valuable global context to the role that tectonics played during the late middle Ordovician based on how much it affected the regional geology of each site. Furthermore, these comparisons will reveal the utility of Neodymium studies towards solving the uncertainties regarding tectonics role in the lithological and faunal changes observed in Eastern North America through the late middle Ordovician.