AN UPDATED GEOLOGIC MAP OF THE SOUTHERNMOST APPALACHIANS OF ALABAMA AND GEORGIA: A SYNTHESIS OF RECENT ADVANCES IN MAPPING, GEOCHEMISTRY, GEOCHRONOLOGY, AND TECTONIC INTERPRETATION

Rocks of the southern Appalachians record a tectonic history that spans the Mesoproterozoic Grenville orogeny, Neoproterozoic breakup of the Rodinian supercontinent and development of the Early Paleozoic Laurentian passive margin, through Paleozoic orogenesis and the culminating assembly of Pangea – a full Wilson cycle. Generations of geologists working in the southernmost Appalachians of Alabama and Georgia have created a tapestry of geologic maps, stratigraphic units, bounding faults, geological histories, and tectonic interpretations that can appear bewildering in their complexity, and often contradictory in their conclusions. Here, we synthesize the most recent published and unpublished data – including structural, stratigraphic, lithologic, geochemical, and geochronologic information – from a myriad of workers into a coherent geologic and tectonic framework that accommodates this comprehensive dataset. The map focuses on Neoproterozoic to Lower Ordovician Laurentian margin units of the foreland, western-eastern Blue Ridge provinces, and Inner Piedmont, as well as the eastern Blue Ridge and western Inner Piedmont paired arc (Dadeville Complex) and backarc (Wedowee-Emuckfaw-Dahlonega basin) system that formed on the Ordovician seaward margin of the Laurentian-plate. Additionally, the map includes younger Middle and Upper Paleozoic Laurentian shelf units of the Talladega belt-western Blue Ridge province that developed inboard of the evolving Acadian to Alleghanian orogenic systems and their accompanying voluminous silicic magmatism (eastern Blue Ridge, western Inner Piedmont) and peak dynamothermal metamorphism. The map updates the extent and nature of major internal and terrane bounding faults associated with tectonic shortening along the Laurentian margin, and emplacement of exotic lithotectonic terranes during the assembly of Pangea. Using modern geochronology and other age relationships, we include a series of tectonic “time slices” depicting the Neoproterozoic to Paleozoic evolution of the Laurentian margin in this segment of the orogenic belt.