CAMBRIAN AND LOWEE ORDOVICIAN. 87 



cases making it a calcareous sandstone. This sand increases in abundance toward the east, in 

 which direction, therefore, its source probably lays. 



The KJnox dolomite occurs in a number of belts, from 1 to 3 miles in breadth, in the north- 

 western portion of the quadrangle, and also forms the surface in a much broader area which 

 occupies nearly the whole of the southeastern third of the quadrangle. These areas are charac- 

 terized by a hilly surface which is usually several hundred feet above the adjoining lowlands. 

 Since exposures of the dolomite are rare, the extent of the formation is determined by means 

 of the residual chert which covers its outcrops. In the vicinity of faults the chert is frequently 

 altered by partial recrystallization of the silica and converted into a white granular rock which 

 readily crumbles on exposure to the air. Hence, those portions of the formation which have 

 undergone this alteration weather to a red siliceous clay soil. This can not be easily distinguished 

 from the soil derived from the Beaver limestone and from portions of the Conasauga formation. 

 Considerable uncertainty, therefore, pertains to the mapping of these three formations, particu- 

 larlj^n a much faulted region, as in the vicinity of Indian Mountain." 



The Ocoee group of Safford, which comprises a great thickness of coarsely 

 clastic strata, together with some finer sediments, is very widely developed in Ala- 

 bama and Georgia. The strata are in general much metamorphosed. Hayes *^*'' 

 states : 



The Ocoee series, whose age is not definitely known, was deposited for the most part near 

 the margin of the sea, where the supply of land waste was abundant but subject to great 

 fluctuations. Fine sediments alternate with coarse material, and few of the formations retain 

 the same characteristics for long distances, except in a very general way. During a part of the 

 Ocoee epoch there were in this region several granite islands, whose waste was deposited about 

 them as basal conglomerates. Later these islands were entirely covered by the sea and by 

 the sediments derived from more distant lands and spread over the sea bottom. The extreme 

 metamorphism which the rocks of this series have undergone toward the east renders it difficult 

 to determine their original limit in that direction or their relation to the older rocks beyond. 



Hayes and Eckel *^* give the following more detailed account of certain aspects 

 and relations of Safford's Ocoee in Bartow County, Ga. : 



The rocks on the opposite side of the CartersviUe fault, occupying the eastern half of the 

 district, present considerable variety in composition and age. A large area, extending from 

 Stamp Creek southward across the Etowah River, to the Atlantic & Western Railroad, is occupied 

 by the Corbin granite, which is, for the most part, a massive coarse-grained rock, containing 

 large porphyritic crystals of feldspar (microcUne), in a groundmass of plagioclase feldspar, 

 muscovite mica, and blue quartz. Some portions of the rock have undergone considerable 

 alteration, by which it has been converted into an augen gneiss. This area of Corbin granite 

 at one time probably formed an island, since it is surrounded, in part at least, by rocks derived 

 from its waste. These are feldspathic conglomerates in which the blue quartz and the por- 

 phyritic crystals of microcline, which characterize the granite, can be readily distinguished. 

 In some places the transition from granite to conglomerate is so gradual that it is difi&cult to 

 determine the exact boundary between the two formations. The development of the gneissoid 

 structure in the granite evidently took place after it was deeply buried by sediment, for the alter- 

 ation of the latter is even more marked than that of the granite itself. Wherever the granite 

 is not bordered by coarse conglomerate or quartzite it is in contact with black graphitic slates, 

 which generally overlie the coarser sediments. 



These conglomerates and slates associated with the granite belong to the Ocoee series, 

 which reaches its greatest development in eastern Tennessee and western North Carolina. No 

 fossils have yet been found in the rocks of this series, although many of them are only sUghtly 

 altered. They contain limestones and slates similar to portions of the adjacent vaUey forma- 



"■ See also quotation from report on the Birmingham district, pp. 164-165. 



