THE DOG RIVER WINDOW--A MAJOR FEATURE OF THE BLUE RIDGE IN WESTERN GEORGIA AND THE PIEDMONT IN ALABAMA

Geologic mapping by ourselves and previous workers has shown that the Blue Ridge in western Georgia consists of a large synformal area composed of felsic and mafic rocks that probably originally was the basal area of an island arc, and of locally pillowed, metamorphosed mafic volcanic rocks of the Ropes Creek Formation, seafloor sediments mostly belonging to the Stonewalll Formation, and chemical sediments derived from black smokers, banded iron formations called Cedar Lake Quartzite. All together, these units make up the “New Georgia Group,” of some workers, and constitute what we believe (following V.J. Hurst) is the Allatoona allochthon, constituting the eastern Blue Ridge exposed from beneath the allochthon in western Georgia. The Allatoona allochthon has been thrust on the Allatoona fault upon rocks of the western Blue Ridge, consisting of the flysch of the Emuckfaw Formation and its northern equivalent the Lay Dam Formation. Where the Allatoona thrust fault has been folded over the Emuckfaw/Lay Dam Formation in the Austell-Frolona antiform, the Emuckfaw/Lay Dam Formations of the Great Smoky Group and rocks correlated with the Chilhowee Group are exposed from beneath the thrust in what we have named the Dog River window. In western Georgia the rocks of the Lay Dam/Emuckfaw Formations have been intruded along the Allatoona thrust fault by the Ordovician and Early Silurian(?) synfaulting granites of the Mulberry Rock and Austell Gneisses. As shown in our companion abstract/presentation (Steltenpohl, Higgins and Crawford, this volume), the window bends to the southeast and east into the Alabama Piedmont.