SECTIONS OF THE CAMBRIAN ROCKS. 467 



to the southern border of the Coosa valley. It will be fully described in 

 a subsequent j^art of this paper, and is mentioned here only because it 

 forms the boundary between two widely different phases of the Cambrian 

 rocks. The formations south of the fault will be first described, then 

 those of the Coosa valley, and finally probable correlations between the 

 two regions will be pointed out. 



Three tyjDical sections of the Cambrian rocks south of the Coosa fault 

 will be described briefly : 



The first, measured in the vicinity of Rome, shows a gray silicious 

 limestone at the base. This has" as j^et yielded no fossils, but has been 

 provisionally correlated with the Beaver limestone, which occupies a 

 similar position in the stratigraphic section of east Tennessee, and has 

 been there determined as Lower Cambrian. Above this limestone are 

 from 700 to 1,000 feet of thin-bedded sandstone and sand}^ shales, with a 

 characteristic bed of white sandstone at the top. These beds constitute 

 the Rome sandstone. Above the sandstone are several hundred feet of 

 olive shales, then beds of oolitic limestone, and finally 1,000 or more feet 

 of calcareous shales, interbedded toward the top with blue limestones. 



The second section, measured on Big Cedar creek, shows the Beaver 

 limestone and the Rome sandstone, similar in character and thickness to 

 the same formations in the section at Rome. Here also the lower por- 

 tion of the Connasauga is composed of fine olive shales, above which are 

 a few beds of oolitic limestone. The upper portion of this formation, 

 however, differs widely in the two sections. The fine calcareous shales 

 of the Rome section are replaced on the Big Cedar b}^ heav}^ beds of 

 limestone. Some of these beds are gray and crystalline, closeh^ resem- 

 bling the Knox dolomite, but free from the compact nodular chert of 

 the latter formation. Other beds contain considerable earthy matter 

 which often retains the form of the rock after the calcareous matter 

 has been removed, and also some chert having a characteristic porous 

 structure. 



The third section, constructed from numerous measurements in the 

 vicinity of Indian mountain, shows wide differences from the two pre- 

 ceding, especially in its lower portion. The Beaver limestone has not 

 been found here and the Rome sandstone is replaced by a formation of 

 much greater thickness and wholly different in character, the Weisner 

 quartzite. This consists at the base of a heavy bed of quartzitic con- 

 glomerate (700 feet), then a great thickness of micaceous shales (1,800 

 feet), and finally a series of interbedded quartzites, shales and coarse 

 conglomerates (3,000 feet±:). In the upper part of this variable series the 

 shale predominates and the conglomerate occurs as thin lenses. Above 

 this series are greenish silicious shales, having a very considerable though 



