TRUNCATION OF THE IAPETAN RIFTED MARGIN ON THE ALABAMA PROMONTORY BY THE SUWANNEE-WIGGINS SUTURE

The Suwannee-Wiggins suture in the Alabama-Georgia subsurface marks continent-continent collision of Laurentia with the African sector of Gondwana. In palinspastic reconstruction of the Appalachian sedimentary thrust belt, the trailing thrust sheets (footwall of the Talladega fault) restore near the present location of the Pine Mountain internal basement massif. COCORP seismic data show relatively shallow basement dipping gently southeastward beneath the foreland and Piedmont metamorphic terranes to the Pine Mountain massif, indicating that the Cambrian-Ordovician passive-margin shelf deposits originally covered the area of the present shallow basement. Similar stratigraphy indicates that the Talladega slate belt is part of the passive-margin shelf; minimum palinspastic reconstruction places the Talladega belt at and southeast of present Pine Mountain, indicating originally greater extent of the shallow basement. The Pine Mountain basement is covered by a transgressive quartzite-marble passive-margin succession, and in part by discontinuous post-rift meta-clastic deposits. If Pine Mountain is a parautochthonous Laurentian basement uplift, it could have originated either northwest or southeast of the Talladega restoration.

COCORP seismic layered reflectors, dipping southeast from near the Coastal Plain onlap to the Moho, project to the surface near the traces of the Alleghanian Goat Rock and Bartletts Ferry fault zones (GR/BFFZ), indicating the structure and leading trace of the Suwannee-Wiggins suture zone. Southeast of the GR/BFFZ mylonite zones, the peri-Gondwanan Uchee arc terrane correlates to Carolinia and/or the Suwannee terrane. Alleghanian overprint on Uchee metamorphic rocks is broadly synchronous with movement along the GR/BFFZ, consistent with Alleghanian continent-continent collision along the Suwannee-Wiggins suture. The present trace of the GR/BFFZ, along with minimum palinspastic reconstruction of the sedimentary thrust belt, Talladega belt, and Pine Mountain massif, shows that the leading edge of the Suwannee-Wiggins suture truncated Laurentian continental crust on the corner of the Alabama promontory at a minimum of 80 km inboard from the Iapetan rifted margin (the margin of full-thickness continental crust inboard from rift-extended transitional crust).