THE SIGNIFICANCE OF THE EXTENSION OF THE MOTTS GNEISS FROM EASTERN ALABAMA INTO THE UCHEE BELT OF WESTERN GEORGIA

Similarities in lithologies suggest that the Moffitts Mill Schist (MMS), a lithologically complex unit separating the amphibolite-rich Phenix City gneiss (PCG) from the migmatitic felsic and amphibolitic gneiss of the North Columbus complex (NCC), extends from Alabama into Georgia where it helps outline the southern limb of the Lake Oliver synform. The Motts Gneiss (MG), a lineated rock which varies from metagranodiorite to metagranite and which contains deformed meta-aplite dikes, occurs as large elongate bodies within the MMS. The MMS and MG trend into the Goat Rock fault, which forms the southeast dipping northern limb of the Lake Oliver synform. The MMS, GRF and BFF rocks are locally rich in fine-grained biotite and muscovite and contain both plagioclase augens and garnet. They also contain meter scale and smaller masses of amphibolite, tightly folded masses of felsic gneiss and scarce small pods of calcsilicate. These similarities suggest that the MMS is a protolith of the GRF and BFF mylonites and that the block-in-matrix character of the mylonites predates mylonitization. The nature of the NCC, its relationship to the PCG and the relationship of the Uchee Belt to rocks of the Inner Piedmont are still under investigation.