A DIGITAL GEOLOGIC MAP ILLUSTRATING THE STRATIGRAPHY AND STRUCTURAL GEOLOGY OF THE LOWER ORDOVICIAN THROUGH MISSISSIPPIAN SYSTEMS IN A PART OF THE ROCKMART NORTH, GEORGIA, 7.5-MINUTE QUADRANGLE

Geologic mapping of a part of the Rockmart North, Georgia, 7.5-minute quadrangle was conducted using traditional and digital mapping techniques. Field data were collected and recorded using the Digital Mapping Assistant developed by Kath (2003) and Global Positioning Receivers (GPS). Detailed stratigraphic and structural data were entered into a Personal Digital Assistant and compiled onto a Digital Raster Graphic (DRG) base map. Detailed stratigraphic and structural mapping of the area reveals a normal stratigraphic sequence, but with a complex stratigraphic and tectonic history. The main area of focus during this study has been in the southeastern and eastern parts of the quadrangle, east of Euharlee Creek. In this area, major rock units are the lower to middle Ordovician Newala and Lenoir Formations, overlain by the middle Ordovician Rockmart Formation. Locally, the Deaton Member of the Lenoir is present. The Rockmart Formation has been divided into two mappable units, a slate member and sandstone/conglomerate member. The sandstone/conglomerate member contains variable amounts of limestone, dolostone, chert, sandstone, and quartzite pebbles and cobbles in a clean quartz-rich sand matrix containing minor feldspar, calcite, and muscovite. Published maps by Cressler (1970) and Sibley (1983) show isolated remnants of Devonian Frog Mountain sandstone; however, current geologic mapping does not support this interpretation. In addition, we have identified several small areas of ferruginous-siltstone/sandstone beds interlayered with thin-bedded chert and chert breccia. Currently we interpret these as outliers of Devonian Armuchee Chert, unconformably overlying the Rockmart. The structural style of the Armuchee suggests that it was deformed with the Rockmart and underlying formations. Lithologies characterstic of the Mississippian Fort Payne Formation have been mapped as overlying an angular unconformity developed on the Rockmart Slate. The structural style of the Fort Payne suggest that it was not deformed during an earlier tectonic event recorded in lithologies of the Newala, Lenoir, Rockmart, and Armuchee.