474 C.W.HAYES — COOSA VALLEY IN GEORGIA AND ALABAMA. 



extends from near Cave Spring toward the southwest, lying north of 

 Indian and south of Weisner mountains. This belt of dolomite is inter- 

 sected by a series of nearl}^ parallel thrust-faults which cut diagonally 

 across, separating it into irregular monoclinal blocks. The faults dis- 

 appear in the belt of Connasauga shale on the north, while their throw 

 is greatest at the northern edge of the dolomite, decreasing southward, 

 and in some cases disappearing wdthin the dolomite area. These faults 

 give rise to the narrow belts of shale which branch from the northern 

 belt and extend varying distances toward the south, forming narrow 

 valleys among the dolomite hills. 



One of these faults, beginning on the state line, turns w^estw^ard along 

 the northern base of Indian mountain, passing through Rock Run. It 

 is specially interesting on account of its connection with the Rock Run 

 limonite and bauxite deposits. 



FROG MT 



Figure 1.— Section through Frog Mountain, south of the Coosa Valley. 

 T T= Major thrast-fault; t t t = Minoi' thrust-faults ,00^ Upper Silurian overlaps. 



The fault which begins about two miles southwest of Forney is shown 

 on the map as passing around the southwestern end of Frog mountain 

 and turning back toward the northeast as far as Rock Run, the two por- 

 tions of the fault being thus approximately parallel. To produce the 

 observed distribution of the formations the two parallel limbs of this 

 fault must hade in opposite directions. The northern limb is precisely 

 similar to the other thrust-faults of this series, the younger rocks are 

 upon its northern side and the fault-plane dips toward the south. The 

 relation of the formations along the southern limb is different. From 

 Hurricane creek to the northeastern end of Frog mountain the rocks on 

 the northern side of the fault are the younger, while from that point to 

 Rock Run they are the older. The latter is the normal relation for a 

 northward dipping fault-plane, as this is believed to be. The abnormal 

 relation along the southern border of Frog mountain is brought about 

 by the presence of the plane of overlap, indicated by in the structure 

 section, figure 1. The fault branching from the one just described west 

 of Rock Run and extending nearly to Forney is quite distinct and has 

 the normal southeastern hade. 



The very marked differences between these folds and faults and those 

 further north in Tennessee and Virginia are due chiefly to the peculiar 



