MAJOR THRUST-FAULTS. 475 



stratigraphic conditions of the region. For a long distance north of In- 

 dian mountain the Cambrian rocks consist of soft shales and limestones 

 Avhich afford little resistance to folding, while toward the south they con- 

 tain great masses of conglomerate and quartzite. These massive strata 

 themselves resisted folding and acted as immovable buttresses, against 

 which the less rigid rocks were thrust ; hence the effect of great com- 

 pression w^as concentrated within a narrow belt west of Indian mountain, 

 while the broad Cedartown syncline lying to the eastward of this buttress 

 was so protected from the compression that its strata remain nearl}^ hori- 

 zontal. The eastward flow of strata past the northern end of this but- 

 tress necessitated a certain amount of rotation in the strata of this region, 

 and this rotation determined the position of the minor thrusts transverse 

 to the main structure lines. The rotation is especially marked in the 

 monoclinal blocks of Knox dolomite between Cave Spring and Weisner 

 mountain, and this also accounts for the group of minor thrusts south of 

 Rome. 



Major Thrust-faults. — Two or three faults of this type occur within the 

 region under consideration. The most remarkable of these, the Rome 

 thrust-fault, has already l)een described.^ (Jwing to peculiarly favorable 

 conditions, certain portions of the overthrust rocks have been preserved 

 from erosion and afford unmistakable evidence of horizontal displace- 

 ment of the strata as well as a minimum measure of its amount. 



The second example of this type, the Coosa fault, has been already 

 referred to above. As showni on the accompanying map, it extends from 

 Rome south westward on the border of the Coosa valley along the north- 

 ern base of Weisner mountain, turning south and then southeast around 

 its western end. The diversity of formations adjacent to different por- 

 tions of this fault is very much less than in the case of the Rome fault. 

 Chiefly for this reason it Avas overlooked in the early study of the region, 

 and until the entire belt was carefully mapped it was regarded as a 

 normal contact between adjacent formations. Upon the northern side 

 of the fault througliout its entire length, with the exception of a mile or 

 two near Rome, occur the green silicious Cambrian sandstone and shale 

 above described. On the.southern side of the fault there is not quite so 

 great unifonnit3\ Throughout a little more than half its length the 

 Rome sandstone lies immediately superjacent to the fault plane. Be- 

 tween Rome and Cedar creek a narrow strip of Beaver limestone occurs 

 at intervals beneath the Rome sandstone and next to the fault. From 

 Forney to the eastern end of Weisner mountain the Rome sandstone 

 almost entirely disappears, or if present is not in contact with the fault, 

 being replaced l)y the Connasauga. 



*The Overthrust Faults of the Southern Appalachians: Bull. Geol. Soc. Am., vol. 2, 1891, pp. 141- 

 154. 



