TERTIARY HISTORY OF THE TENNESSEE RIVER 227 



have been developed under the conditions imposed by the theory 

 of capture. 



Hayes and Campbell report the occurrence of the Tertiary river 

 gravels on remnants of the Tertiary peneplain about Chattanooga, 

 250 feet above the present river, and in the Sequatchie valley, 150 

 feet above the river. If this difference of 100 feet in the relative 

 elevation of the gravels were correct, it might be advanced as evidence 

 in favor of the theory of capture; for on the basis of the alternative 

 theory we should expect to find the gravels about as high above 

 the river on one side of the ridge as on the other. On the contrary, 

 if these gravels should be found 250 feet above the river in the Se- 

 quatchie valley, that in itself would be practically conclusive against 

 the proposed capture, as it would show the former presence of the 

 river at an elevation incompatible with the theory advanced. 



North of Shellmound, in the Sequatchie valley, is a series of hills 

 which rise well above the present valley floor. The contour lines 

 show the summits of these hills to be something over 200 feet above 

 the river. The Tertiary gravels, of material that could have been 

 brought from far to the northeast by the Tennessee River alone, 

 are abundantly developed on these hills, completely cloaking the 

 summit in one case. Barometric readings showed that the gravels 

 occur up to 265 feet above the level of the river itself, or about 230 

 feet above the river floodplain. 



Absence of Tertiary gravels south of Chattanooga. — The Tertiary 

 river gravels are abundantly represented about Chattanooga and in 

 that portion of the longitudinal valley to the northward of the city. 

 These gravels occur capping remnants of the Tertiary peneplain 

 and widely distributed over lower levels. Their presence in the 

 valley west of the ridge and southward from the gorge has been also 

 noted. Therefore, if the river flowed southward into the Coosa- 

 Alabama system until the close of the Tertiary cycle, we should 

 find ample evidence of that fact in the distribution along this former 

 southward course of the gravels which are so abundant along the 

 present course of the river. These gravels cannot be confused with 

 any that might be derived from sandstones or conglomerates locally 

 represented, but, as has been pointed out by Hayes and Campbell, 

 must have been brought from far to the eastward. And since these 



