W. A. Vervriebe — Berea Formation. 49 



nature of the material and a difference from the material below 

 when encountered by the drill. 



It has been suggested that the sandstone in the section along 

 Oil Creek is not the Corry but the Cnssewago sandstone.* 

 However, the presence of the Cnssewago limestone under it in 

 typical development and the excellent exposures of the Orange- 

 ville shale immediately above it point to the conclusion that it 

 is the Corry. 



Farther to the east, as shown in the sections at President and 

 Hunter, the Corry becomes still thicker and also rather coarser. 

 The superjacent Orangeville also undergoes much the same 

 change, becoming more arenaceous and containing more sand- 

 stone layers. At the base of the Corry, which may be traced 

 for miles along the Allegheny from President northward, the 

 Cnssewago limestone occurs. It may be seen to good advan- 

 tage at Baum (almost on the line between Forest and Venango 

 counties) where it is two feet thick and lies about 20 feet 

 above the railroad tracks. 



Northward, along the Allegheny River, the Corry sandstone 

 has been traced in excellent fashion by Butts ; however, from a 

 careful study of the stratigraphy of the region the writer is 

 unable to accept his correlation with the Venango first oil sand. 

 The evidence noted above to indicate that the formation is 

 equivalent to Butts' middle Cuyahoga sandstone is further 

 corroborated in a graphic manner in fig. 1. A section was 

 taken from Butts' diagram at a point about midway between 

 Tionesta and Hunter (section K in fig. 1). This is inserted 

 between sections M (Miller Farm ; 9 miles N.W.) and section 

 L (Oil City : 12 miles S.W.), first using the nomenclature of 

 Butts (section K'-), and again between the same two sections, 

 but considering his middle Cuyahoga sandstone as the Berea 

 (section K 2 ). The base of the Shenango sandstone is used as 

 the datum plane. It will now be seen that the interval between 

 the Shenango and the Corry is suddenly increased from 160 

 feet (section M) to 360 feet in a distance of less than 10 miles 

 if the section K 1 is correct. However, if the section be inter- 

 preted as at K 2 the base of the Shenango sandstone will be 

 seen to vary but slightly, and the interval between it and the 

 Corry will be practically the same as in sections L and M. 



A correct correlation of the Berea sandstone should have a 

 far-reaching effect in clarifying the stratigraphy of the whole 

 of western Pennsylvania, for it has been used as a key horizon 

 not only in the extensive oil and gas fields, but also in the diffi- 

 cult northern area underlain mostly by Devonian shales. The 

 oil and gas field extends roughly southwest from the district 

 studied into West Virginia, Ohio and Kentucky. It has been 

 ♦White, I. C, Pa. 2d Geol. Survey, vol. Q4, p. 93, 1881. 



Am. Jour. Sci.— Fourth Series, Vol. XLII, No. 247.— July, 1916. 

 4 



