Devonian Shales of Ohio and Pennsylvania. 41 



\)e considered " either as a Chemung group, or as a Portage 

 group, or as a transition group, or as an independent intermedi- 

 a,te group." It appears to the writer after careful study of its 

 stratigraphy and lithology that its true relation lies with the 

 Chemung of New York, 



This takes us only a short distance into the state though, and 

 further east Warren county geology obliges us to wrestle with 

 a totally different nomenclature. Carll did some excellent 

 work as shown in V of the publications of the Second Geo- 

 logical Survey. However, it is evident from the first that he 

 was not aware of the pronounced unconformity at the base of 

 the Glean and hence is severely troubled by the non-agreement 

 of horizons which he traces by his rule of " parallelism of 

 strata." He w^rongly correlates the sub-Glean with the She- 

 nango sandstone and tries to lit in the numerous conglomerates 

 below this according to the interval between them. The credit 

 for clearing up a good deal of this confusion belongs to Chas. 

 jButts who has done much excellent work in western Pennsyl- 

 vania recently. 



Conewango formation : This name was proposed by Chas. 

 Butts'^ for the interval between the Chemung rocks and the 

 Knapp formation of Glenn. He describes the Conewango as 

 consisting of " greenish sandy shale, with thin layers of very 

 fine-grained greenish micaceous and argillaceous sandstone." 

 In the middle is a persistent conglomerate, 20 feet thick, called 

 the Salamanca and considered the equivalent of the third 

 Yenango oil sand. The total thickness is given as about 550 

 feet. In correlating these rocks Butts inclines to the belief 

 that they are " the equivalent of some part of the Catskill 

 formation." This is quite probably correct. In tracing the 

 formations from the Ghio line toward the Alleghany Biver the 

 writer reached the conclusion that the Conewango (including 

 the Knapp) is essentially equivalent to the Yenango oil group, 

 which would imply the same correlation. 



Gn this basis also, the Salamanca is considered the probable 

 equivalent of the second Yenango oil sand instead of the third. 

 All who have worked on the problem will admit that the 

 identification and tracing of the oil sands on the outcrop is a 

 difficult matter ; however, a careful study of the Tidioute region 

 where the Salamanca first appears above ground and a compari- 

 son of the well records to the south, point strongly to that con- 

 clusion. Accepting this correlation it would seem but logical 

 to conclude that the " Wolf Creek " conglomeratef is the repre- 



* U. S. G. S. Folio 172, p. 25. 



f Glenn, L. C, Devonic and Carbonic Formations of southwestern New 

 York : 56tli Ann. Eept. N. Y. State Mus. for 1902, vol. 2, 1904, pp. 971 and 

 972. 



