The Ocoee series is divided into four major units present from northern North Carolina to western Georgia and a fifth, younger, formation present only in southern North Carolina and Georgia. The units recognize dare as follows: The Ocoee series is a broad synclinal belt of resistant Great Smoky quartzite, which forms most of the Great Smoky Mountains and the Bald Mountains, with Nantahala slate and in places the Big Butt quartzite enclosed in synclines; the Hurricane graywacke is on the flanks of the main syncline. In the deeper Murphy syncline the Big Butt quartzite is overlain by the Valleytown formation. The Ocoee series is thrust northwestward on the Great Smoky overthrust over Paleozoic rocks of the Great Valley, and in Tennessee overrides unmetamorphosed sandstone, shale, limestone, and limestone conglomerate which previously were mapped as Wilhite slate and were included in the Ocoee series. These rocks in a few places contain Middle Ordovician fossils and are a newly recognized part of a clastic shore facies equivalent to an expanded Tellico sandstone of undetermined stratigraphic range. This part of the Ordovician shore facies is in the Pulaski block in Tennessee and is exposed also in windows in the Great Smoky overthrust block in Tennessee, North Carolina, and Georgia. The Ocoee series does not resemble the Lower Cambrian Chilhowee group, which it overrides, nor any other Lower Cambrian facies. Lower Cambrian quartzites overlie with erosional unconformity the Catoctin basalt, Swift Run tuff, and Mt. Rogers volcanic series, proving that these volcanic rocks are late pre-Cambrian. The Ocoee series resembles the Lynchburg gneiss, which is equivalent to the late pre-Cambrian Swift Run tuff. The Ocoee series is stratigraphically overlain by the Lower Cambrian Unicoi formation and is late pre-Cambrian. © 1949, The Geological Society of America, Inc.