THE PANGEAN TRANSCURRENT FAULT ZONE

Recent analysis of geological and geophysical data from the southeastern U.S. suggests that a linear, ENE-WSW trending, southeast-dipping, crustal-scale boundary (1) can be traced along strike for more than 1,400 km, (2) truncates all known pre-Mesozoic structure and stratigraphy, (3) forms the principal boundary between crust of formerly Laurentian and that of Gondwanan affinity, (4) coincides with the Carolina-Mississippi fault of Higgins and Zietz (1983), and (5) supports the Pangea B interpretation of paleomagnetic data involving 1,200-3,000 km of Late-Alleghanian dextral slip within the Pangean supercontinent. Here we propose the name “Pangean Transcurrent Fault Zone” (PTFZ) for this boundary, as expressed in the southeastern U.S. Features to the north of and truncated by the PTFZ (from NW to SE) include (1) the Appalachian foreland basin, (2) the New York-Alabama lineament, (3) the Appalachian foreland fold and thrust belt, (4) the Brevard zone, (5) the Central Piedmont shear zone, and (6) the Eastern Piedmont fault zone. Features to the south of and truncated by the PTFZ (from SW to NE) include (1) the Late Neoproterozoic Osceola arc (Boote et al, 2018), (2) the Late Neoproterozoic Brunswick suture zone and (3) associated Brunswick magnetic anomaly, and (4) the overlying Early to Mid-Paleozoic Suwannee basin stratigraphic sequence. Images on legacy crustal-scale seismic reflection data imply this zone of deformation overprints, and was previously confused with, crustal-scale structures associated with the Late Neoproterozoic Brunswick suture zone (coincident with the Brunswick magnetic anomaly low) and contractional structures of the Alleghanian collision between Gondwana and Laurentia. In southern Alabama and eastern North Carolina, the PTFZ is constrained to be no wider than ~10 km within the shallow crust. Through central South Carolina and Georgia, the PTFZ appears to include large blocks of inferred Gondwanan and Laurentian affinity, based on magnetic anomaly patterns and well control. At present, no common pre-Mesozoic structures, stratigraphy, or lithotectonic units can be correlated across the PTFZ along its entire inferred extent. We postulate that the Gondwanan crust south of the PTFZ in the southeastern U.S. (1) was not proximal to, and was largely unaffected by, the Alleghanian collision, and (2) was translated through large-scale Late-Alleghanian dextral slip to its present position.