52 



W. A. Vcru'lcbt — Iifrat Formation. 



If this is done it will soon appear that there is a considerable 

 difference in the correlation of the Berea on the one hand and 

 the limits of the Pocono (which is nearly universally accepted as 

 the basal member of the Mississippian in eastern Pennsylvania) 

 as a re.-ult of this on the other. Years ago Carll* established 

 the equivalence of the 1st Venango oil sand and the Hundred- 

 foot or Butler 2d sand. This correlation is still accepted by all 

 who have worked on the problem. Therefore, in the stratig- 

 raphy of the quadrangles more recently described and pub- 

 lished since Butts' article appeared, his conclusions regarding 



Fig. 2. 



Fig. 2. Map of northeastern Ohio and northwestern Pennsylvania, show- 

 ing the location of sections plotted in fig. 1. 



the correlation of the Yenango 1st oil sand with the Berea 

 have largely been accepted. For example, in the Foxburg and 

 Clarion quadrangles, which lie immediately south of the region 

 discussed in the preceding pages, the Hundred-foot sand is con- 

 sidered equivalent to the Berea sandstone,f whereas the sand- 

 stone, which in the estimation of the author is the true Berea, 

 is called the Sharpsville sandstone.;}: 



In the Sewicldey quadrangle Munn makes the same correla- 

 tion, and places the base of the Pocono at the base of the 

 Hundred-foot, thus giving it a thickness of approximately 800 



* Pa. 2d Geol. Survey, vol. i 3 , pp. 178 and 272. 

 t U. S. Geol. Survey, Folio No. 178, p. 4, 1911. 

 X U. S. Geol. Survey, Bull. No. 454, p. 18, 1911. 



