AEROMAGNETIC CLUES TO THE FINAL ASSEMBLY OF PANGEA: WAS FLORIDA THE LAST ADDITION?

Supercontinent Pangea formed at the end of the Paleozoic Era during the Alleghanian and Variscan (including Uralian) orogenies as a product of continent-continent collision. We know a great deal about the products of the collision in the exposed Appalachians and European orogens and have gained insights into their buried components via aeromagnetic and gravity maps. Our knowledge of the kinematics of the final collision, however, is less complete in the segments buried beneath the Atlantic and Gulf Coastal Plains. The dextral Eastern Piedmont fault system (EPFS) and its kinematics in the southeastern Appalachians are well documented from surface exposures and aeromagnetic maps as a fault system that displaced crustal blocks southward as Gondwana (including Africa) collided obliquely north-to-south with Laurentia, zippering closed the last Theic ocean segment. The well-known Brevard fault forms the most continuous western limit of the domain of southern Appalachian Alleghanian strike-slip faults. EPFS and blocks of the Brunswick (Charleston) terrane (BCt) converge and thin into a narrow zone between the Florida block (Suwannee terrane) and Laurentia beneath the Coastal Plain of AL and GA along the Suwannee-Wiggins suture (S–Ws). All but a few faults of the EPFS were cut out as the entire Appalachians and older crustal elements to the W also were truncated along the S–Ws. A major pre-Mesozoic(?) sinistral fault located in GA and SC (here named the Estill fault) appears to offset large magnetic highs in the BCt, with the east side displaced northward, as if to escape the collision zone. We hypothesize that Florida may have been the last block accreted to Laurentia during the assembly of Pangea, truncating the EPFS and other Laurentian elements of the Appalachians, and older crust to the west, creating the highly curved southern part of the EPFS, and forming the Estill fault that displaced crustal blocks of the BCt out from the collision zone.