Paper No. 25
Presentation Time: 8:00 AM-12:00 PM
1:24000-SCALE GEOLOGIC MAPPING OF THE OUR TOWN AND DADEVILLE, ALABAMA QUADRANGLES IN THE SOUTHERNMOST APPALACHIANS
Geologic mapping of the southernmost exposures of the Appalachian Mountains in Alabama is aimed at characterizing rocks and structures of the eastern Blue Ridge and Inner Piedmont terranes, and their relations to those in the Pine Mountain basement-cover terrane. Ongoing 1:24k mapping is focused on the Our Town and Dadeville quadrangles which contain rather exceptional exposures along the shores of Lake Martin. Eastern Blue Ridge units exposed on the Our Town and Dadeville quadrangles are of the Wedowee Group, Elkahatchee Quartz Diorite, Emuckfaw Group and various granitic intrusions. Inner Piedmont units include the Waresville Schist, Agricola Schist, Ropes Creek Amphibolite, and mafic/ultramafic bodies of the Dadeville Complex. The Brevard fault zone lies between these two terranes and in this area lithologic units defining the Brevard zone are of the Jacksons Gap Group. We report results of our latest mapping efforts, and 40Ar/39Ar muscovite cooling ages from the Kowaliga Gneiss and Zana Granite; bulk geochemical analyses and U-Pb age dating of zircons from these intrusives were underway as this abstract was written and we plan to report those results as well. Some surprising findings in the Our Town quadrangle include NW-trending-tops-SW brittle normal faults, several varieties of Kowaliga Gneiss defined by the presence or absence of K-feldspar megacrysts (up to 10 cm in length), late-stage cross-cutting aplite dikes, and previously unmapped NE-trending dextral mylonite zones. Findings from the Dadeville Quadrangle include xenoliths of Ropes Creek amphibolite incorporated within metagabbros, well-layered metavolcaniclastics within the Waresville Schist, and a major ~10 m wide, NW-trending, NE-dipping mylonite zone near Blue Creek Marina with kinematics currently being investigated. Results will contribute to our growing database aimed at understanding the teconostratigraphic relationships between the eastern Blue Ridge, Inner Piedmont, and Pine Mountain terranes and how and when they were amalgamated.