8UBGARB0NIFER0V8 FORMATIONS. 77 



SUB-CARBONIFEROUS FORMATION. 



In the Sub-carboniferous formation of Wills' Val- 

 ley is found the best known deposit of pure white 

 clay of this section. 



This clay occurs chiefly in the lower strata of the 

 formation;^ generally very close above the Devonian 

 Black Shale. The deposits which have, up to the pre- 

 sent time, been pretty well proven, are to be found in 

 the upper or northeastern end of Wills' Valley, near 

 the Georgia line, and on both sides of the valley. The 

 most important of them, however, occur on the easit- 

 ern side of the valley. They have been described 

 somewhajt in detail by McCalley in Part II of his Val- 

 ley Regions report, pages 175 to 182, from which the 

 following details are compiled : 



The Red Mountain ridges, made up of the strata 

 of the Clinton, Devonian (Black Shale), and Sub- 

 capbcmiferous format}ionsi, occur here as elsewhere 

 in the State, on both sides of the valley. The ridge 

 on the western side is, in general, lower and less con- 

 tinuous than thalt on the eastern side. The clay 

 occurs in the lower strata of the Sub-carboniferous, 

 not far above the Black Shale, and it has been "pro- 

 spected" and found to be present in the ridges on 

 both sides of the valley for some ten or twelve miles 

 from the State line southward. 



In the northwest corner of S. 3, T. 6, R. 9 E., on the 

 west side of the valley, a test pit exposes the following 

 section : 



Section on west side of Wills' Valley, DeKalb Co. 



Chert ledge weathered into a sandy rock of yellow color 8 to 12 inches. 



Strata hidden by debris 2 to 3 feet. 



White clay, without grit, in places like halloysite 3 feet . 



Bluish colored clay 3 feet. 



Strata not exposed 25 *" 30 feet. 



Devonian Black Shale 



