CAMBRIAN AND LOWER ORDOVICIAN. 85 



The Rome formation consists of thin-bedded, fine-grained sandstones and sandy shales. 

 Its most striking peculiarity is the brilliant coloring of its beds. The prevailing colors are 

 various shales of red, purple, green, yellow, and white. The changes in color are often very 

 abrupt and the exposures of the formation present a distinctly banded appearance. The base 

 of the formation, where it is found resting upon the underlying Beaver limestone, consists of 

 thin-bedded red sandstones, and the top of the formation is characterized by a rather heavy 

 bed- of white sandstone. Northeast of Rome the upper portion of the formation consists 

 chiefly of shale and is distinguished on the map as a lentil in the formation. In its type locality, 

 south of Some, the formation is between 700 and 1,000 feet in thickness. Its beds are always 

 more or less folded, so that it is impossible to make exact measurements of its thickness. The 

 formation is confined to a narrow belt crossing the quadrangle diagonally from northeast to 

 southwest at the eastern margin of the Coosa Valley. Its rocks are somewhat more resistant 

 than the limestones which occur above and below, and it forms a line of low ridges between the 

 lowlands on either side. 



The Conasauga formation presents a number of widely differing phases within the limits 

 of this quadrangle. At its type locality, in the Dalton quadrangle to the northeast, it consists 

 of a great thickness of fine clay shales with occasional beds of limestone. The latter vary in 

 thickness from a few inches to several hundred feet, and are always rather pure, blue limestone. 

 In the vicinity of Rome and northeastward to the margin of the quadrangle, the formation 

 consists at the base of several hundred feet of fine olive clay shale, then beds of oolitic limestone, 

 and finally 1,000 or more feet of calcareous shales, interbedded toward the top with blue lime- 

 stones. Southward from Rome the formation changes considerably by an increase in the 

 amount of limestone. A typical section is exposed on Big Cedar Creek, where it crosses Vans 

 Valley. The lower part of the 'formation consists of olive shales, above which are oolitic lime- 

 stones, the same as at Rome. The upper portion of the formation, however, consists largely 

 of heavy beds of limestone. Some of these limestone beds are gray and crystalline, closely 

 resembhng 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 masses of characteristic cellular chert. The 

 two phases of the Conasauga formation above described are confined to the strip of lowland 

 between the Rome sandstone ridges and the Knox dolomite plateau which occupies the south- 

 eastern half of the quadrangle. 



Northwest of the Rome sandstone ridges there is a much larger area of the Conasauga 

 formation, occupying the greater part of the Coosa VaUe}'. The formation here varies some- 

 what widely from the type' to the east,^ and is capable of subdivision into three rather distinct 

 phases. The upper portion of the formation, along the eastern margin of the Coosa Valley, 

 consists of characteristic greenish siliceous shales. These have been separately mapped and 

 are indicated on the sheet as a lentil in the formation. In some cases the shales are replaced 

 by greenish micaceous sandstone, which is always highly contorted and crushed into a series 

 of lenticular masses from a fraction of an inch to 4 or 5 inches in thickness. The sandstone is 

 always fiUed with cracks or fissures, which have the appearance of having been produced by 

 contraction of the bed. These cracks are partially filled with quartz, and where they are 

 unweathered the remaining space is occupied by calcite. The sandstone is confined to the 

 southeastern margin of the valley. Northwestward the sfiiceous beds become fewer, being 

 replaced by fine olive-green shales, and throughout the central portion of the valley this division 

 is represented by olive shales, in which occur numerous flat concretions composed of gray 

 sihceous rock intermediate in character between fine-grained quartzite and chert. Along the 

 northwestern border of the valley this division becomes very much more calcareous. The 

 concretions are similar in appearance to those above described, but are composed of siliceous 

 limestone. As the shale holding these siliceous concretions weathers they collect upon the 

 surface and resemble deposits of waterworn gravel. The intermediate division of the Conasauga 

 as it occurs in the Coosa Valley is composed of clay shales containing varying amounts of lime- 

 stone. The limestone appears in some places as a few thin beds scattered through the shales. 



