144 C. W. HAYES — OVERTHRUST FAULTS OF THE APPALACHIANS. 



tion of the Chickamauga limestone, which is only less massive than the 

 dolomite itself, there are approximately 5,000 feet of strata with indistinct 

 bedding and entirely without beds of shale. The dominating influence which 

 this mass of maximum rigidity has exerted on the structural forms resulting 

 from lateral compression will be pointed out later. 



The Connasauga, which is composed of alternating beds of limestone and 

 calcareous shale, together with the Rome sandstone, form a group of strata 

 with intermediate rigidity which lies below the Knox dolomite and is similar 

 to the group above that formation. 



Finally, below the Rome sandstone are the Coosa shales, having an un- 

 known but very great thickness and a minimum rigidity. Some consider- 

 able beds of limestone occur in these shales, but they form too small a pro- 

 portion of the mass to add appreciably to its rigidity. 



General Structure of the Region. , 



In following the great Appalachian valley to the southwest, a marked 

 change in structure is observed at the Tennessee-Georgia line. In place of 

 the narrow, faulted synclinals which prevail throughout east Tennessee, a 

 single broad, gently undulating synclinal occupies the whole of the eastern 

 portion of the valley, while in the western part the structure resembles that 

 of Virginia. The strata are rather closely compressed into unsymmetrical 

 folds with occasional faults of slight displacement on the steeper side of the 

 anticlinals. 



The broad synclinal above mentioned as occupying the eastern portion of 

 the valley extends from the metamorphic rocks on the east to the Oostanaula 

 and Coosa rivers on the west. On either side is a thrust fault ; that on the 

 west may conveniently be called the Rome fault and that on the east the 

 Cartersville fault. These will now be described in detail. 



Rome Thrust Fault. 



Characteristics 7iorth of Dalton. — The Rome fault is the southern prolon- 

 gation of one of the main lines of Appalachian displacement. Willis and 

 Keith ^ have traced it to the northwest entirely across Tennessee and into 

 Virginia, where it has been described by Stevenson under the name of the 

 *' Saltville fault." f Thus its length from Dalton, Georgia, to its northern 

 extremity in Virginia is at least 275 miles. Throughout this distance it 

 differs from a dozen or more faults of the same region only in its greater per- 

 sistence and perhaps by a somewhat greater average vertical displacement. 



* Unpublished Atlas Sheets, Appalachian Division of Geology, U. S. Geological Survey; by Bailey 

 Willis and Arthur Keith. 



t Notes on the Geological Structure of Tazewell, Russell, Wise, Smythe and Washington counties 

 of Virginia; John J, Stevenson, Proc. Am. Phil. Soc, vol. XXII, Philadelphia, 1884. 



