480 C. W. HAYES- —COOSA VALLEY IN GEORGIA AND ALABAMA. 



and Weisner mountains, while the main summits of those mountains 

 were not reduced quite to the level of the Cretaceous peneplain. 



The second or Tertiary peneplain was developed only on areas of com- 

 paratively soft rocks, but has been more perfectly preserved, so that 

 considerable remnants are found in the region mapped. This peneplain, 

 like the preceding, was warped as it was elevated, and now slopes gently 

 toward the northwest, decreasing in altitude from more than 900 feet in 

 the vicinity of Cedartown to about 750 at the Coosa river. The broad 

 dolomite area between Rome and Cedartown was nearly reduced to base- 

 level, though the more silicious portions remained as low hills from 100 

 to 150 feet above the peneplain. 



During the closing epoch of the Tertiary, erosion was active upon the 

 surface of this peneplain, and the Coosa valley was lowered about 140 

 feet on the underlying soft shales, only a few low hills, as the one on 

 which Center is located, escaping degradation. Following the formation 

 both of the Tertiary peneplain and the subsequent baseleveled valley 

 came a slight depression of the surface probably nearly or quite to sea- 

 level. At the same time the carrying capacity of the upper portion of 

 the streams was increased either by steeper slope or greater volume, so 

 that they brought down vast quantities of gravel which they deposited 

 along their slackened lower courses. These are the high and low-level 

 deposits of silt and gravel already described. 



Finally, the region has very recently been slightly elevated, and the 

 Coosa river is at present lowering its channel in the last formed baselevel 

 valley. Its sinuous course is inherited directly from the conditions 

 which prevailed during the deposition of the low-level gravels when the 

 stream was overloaded and wandered from side to side of a broad deposi- 

 tion plain. 



United States Geological Survey, 



Washington, D. C, April 9, 189Jf. 



