Paper No. 18
Presentation Time: 8:00 AM-5:30 PM
PRELIMINARY GEOLOGIC MAP OF THE MURPHY MARBLE BELT IN GEORGIA
Our geologic mapping in the Murphy marble belt over the past 33 years has been compiled into ESRI's ArcMap 9.2 at a scale of 1:24,000 and presented at a scale to fit the poster boards. The geologic mapping ranges from detailed in most of the 7.5-minute quadrangles covering the marble belt in the Cartersville 1:100,000-scale quadrangle to detailed reconnaissance in some of the quadrangles in the Dalton 1:100,000-scale quadrangle. The mapping and many new exposures show that thrust faults, duplexes, and map-scale isoclinal folds are common within the belt, that the graphitic rocks of the Nantahala Formation (Chilhowee Group), including its sheared derivative, the Padgett Falls Formation, are repeated as many as four times, and are the site of thrusts that carry the Neoproterozoic Emuckfaw/Lay Dam Formation of the Great Smoky Group over other outcrop belts of Emuckfaw/Lay Dam. In the Tate-Marble Hill area, marble (Long Swamp Creek marble), a metavolcaniclastic amphibolite unit (Marble Hill amphibolite), and an unnamed biotite gneiss identical to basement rocks to the northeast are unique in the marble belt and may belong with the eastern Blue Ridge. The Tate-Marble Hill area is a culmination in the Whitestone thrust. In the Whitestone-Ellijay segment of the belt, where the marble-amphibolite-biotite gneiss triplet is not present, marble is overthrust on the east by the Whitestone thrust that has brought Nantahala Formation in the staurolite zone over the marble. Common to all segments of the marble belt is a unit containing coarse-grained staurolite-cross-biotite schist and metaconglomerate. In most areas the marble belt rocks are at higher metamorphic grade than the Great Smoky Group rocks on the western flank of the belt, constituting a metamorphic inversion. However, there are some rocks in the belt that are in the chlorite zone that are flanked on both sides by rocks in the staurolite zone. Our mapping does not show isograds crossing the marble belt at an angle, as previous workers have shown it, but rather the isograds approximately conform to the structural trend of the belt.