CARBON ISOTOPE STRATIGRAPHY OF THE SANDBIAN STAGE IN THE CENTRAL APPALACHIAN BASIN

New stable carbon isotope (δ¹³C) curves of the Black River and Trenton Groups from Germany Valley (West Virginia) and Union Furnace (Pennsylvania) are presented here. These sections span the Sandbian Stage in the Central Appalachian Basin. This study aims to determine whether changes in the δ¹³C trends are driven by the global carbon cycle or a local perturbation in response to sea level fluctuations (i.e., aquafacies) related to local tectonics, as this period is characterized by active tectonism in the Appalachian Basin.

The Black River and Trenton Groups in the Central Appalachian Basin consist of peritidal to deep ramp carbonates, which broadly accumulated during the Sandbian. Our sequence stratigraphic analysis suggests a general deepening trend within the Black River Group exposed in the Union Furnace and Germany Valley sections, indicating that this sequence was deposited during an increase of accommodation space. A correlation of this transgressive sequence to sea level reconstructions from Oklahoma, Baltoscandia, and the Siberian Platform suggests a role for eustatic sea level rise. The Germany Valley section exhibits higher frequency relative sea level fluctuations within the Black River Group, that are interpreted as products of local tectonics as the Germany Valley section is located closer to the foreland basin edge.

We observe a general rising trend in δ¹³C data from both sections, from -0.60‰ at the base of the Hatter Formation in PA and -0.24‰ at the base of the New Market in WV to 0.80‰ at the top of the Nealmont Formation in both sections. We also observe higher frequency fluctuations in the carbon isotope curve from the Germany Valley section. A covariance between these higher frequency fluctuations of δ¹³C and changes in lithofacies and sequence boundary surfaces, suggests local processes (e.g., platform restriction and/or aquafacies) affected the carbon cycle in the distal region of the Central Appalachian Basin during Sandbian.