Structural analysis of the Carolina‐Inner Piedmont terrane boundary: Implications for the age and kinematics of the central Piedmont suture, a terrane boundary that records Paleozoic Laurentia‐Gondwana interactions

Abstract

New field mapping along the Carolina‐Inner Piedmont terrane boundary in South Carolina and eastern Georgia reveals preaccretionary, synaccretionary, and postaccretionary faults. The dextral strike‐slip Lowndesville shear zone is adjacent to a ∼50‐km‐long segment of the terrane boundary. However, the Lowndesville shear zone is correlated eastward with the dextral strike‐slip Beaver Creek shear zone, which is within the Carolina terrane and predates ∼415 Ma. The Lowndesville shear zone is overprinted by a dextral strike‐slip phyllonite zone, named the Deal Creek shear zone. The Deal Creek shear zone is correlated eastward with the Gold Hill‐Silver Hill shear zone which is also within the Carolina terrane and records dextral strike‐slip motion between ∼400 and ∼325 Ma. The Cross Anchor and Mulberry Creek faults both truncate the Lowndesville and the Deal Creek shear zones and form the terrane boundary. The Mulberry Creek fault, probably of Triassic‐Jurassic age, juxtaposes the Lowndesville shear zone adjacent to the Carolina‐Inner Piedmont terrane boundary west of Waterloo, South Carolina. The Cross Anchor fault is the terrane boundary east of Waterloo, South Carolina, and forms the southeastern boundary of the Whitmire reentrant. Crosscutting relationships indicate that the Cross Anchor fault is the oldest fault which juxtaposes the Carolina and Inner Piedmont terranes in the study area. These structural interpretations and available geochronological data indicate that the Cross Anchor fault is a ∼325 Ma thrust fault and may be the central Piedmont suture. An early Alleghanian suture resolves the problem of inserting the Carolina terrane into the western Iapetus Ocean.