DELINEATING THE CENTRAL PIEDMONT SUTURE IN UNION COUNTY, SOUTH CAROLINA

The geologic history of the southern Piedmont is a complex story of accreted terranes, nappe tectonics and metamorphism. In order to understand the history of these environments, it has been stated that "arguably, the most important elements to consider regarding the accretion of outboard terranes are the structural positions of terranes, relative metamorphic grade between adjacent terranes, and timing of peak metamorphic events" (Huebner et al., 2017). Despite this, much of the region has not undergone detailed geologic mapping, and terrane boundaries are still not precisely known. The present study sought to resolve the terrane boundary between the Cat Square and Charlotte terranes called the Central Piedmont Suture in Union County, South Carolina which is host to the Calhoun Critical Zone Observatory. This boundary is interpreted as the contact between the Laurentian margin and a peri-Gondwanan volcanic island called Carolinia that was accreted during the formation of Pangea. Detailed geologic mapping and petrography was performed along the suspected boundary. Initial results indicate both mafic to ultramafic meta-volcanics consistent with the Charlotte terrane and meta-greywackes consistent with the Cat Square terrane. In addition, the terrane boundary lays farther west than previously reported on larger scale reconnaissance maps. Geochemical data suggests granitic rocks are similar in composition to other peraluminous Paleozoic plutons found in the area. Finally, this work has important implications for ongoing work at the nearby Calhoun Critical Zone Observatory which seeks to understand how the landscape has evolved through time as the map produced in the present study provides starting conditions for ongoing work.

Huebner, M. T., et al. (2017). "Confirmation of the southwest continuation of the Cat Square terrane, southern Appalachian Inner Piedmont, with implications for middle Paleozoic collisional orogenesis." American Journal of Science 317(2): 95-176.