36 W. A. Ve?nviehe — Correlation of the 



sides of the state line, which makes it difficult to trace the 

 formations stratigraphically. Still when the lower formations 

 are traced from both directions it appears that the Bedford 

 should be correlated with the Yen an go oil sand group of 

 White. These in turn are clearly equivalent to a portion of 

 the Catskill formation of New York state. 



Cleveland : In the Report of Progress of the Ohio Geologi- 

 cal Sm'vey for 1869 JSiCwberry first suggested this name. It 

 applies to black shale which has a considerable thickness on its 

 westernmost outcrop but i^apidly thins to but 16 feet in its 

 easternmost exposure."^ This thinning suggested the same 

 conclusion that was mentioned in regard to the Bedford, i. e., 

 overlap toward the east. In this case the fallacy of such a 

 conclusion can be seen even more clearly, for in many places 

 evidence is presented showing that the Cleveland is simply a. 

 horizontal variation of the bluish grey shales known as Chagrin 

 sliales. Section Ko. Y in figure 1 has 18 feet of black shale, 

 beneath this is 7 feet of alternating black and bluish shale and 

 beneath this again is the typical bluish shale of the Chagrin 

 formation. Otlier sections which might be cited show this 

 transition from black to blue equally plainly. In fact it 

 appears that the name suggested by Cushingf applies to just 

 such transition rocks in the region west of Cleveland. He 

 describes the Olmstead shales as blackish and soft (instead of 

 slaty as the typical Cleveland shale) and interbedded with thin 

 bands of blue shale. 



It seems therefore that conditions favorable for the forma- 

 tion of black shales existed in the central part of Ohio much 

 earlier than in the eastern part, but that these conditions did 

 become so widespread that they affected deposition in eastern 

 Ohio toward the close of Chemung time. 



Chagrin: This term was suggested by Frosser because of 

 the excellent exposures of the formation of the Chagrin Biver 

 above Willoughby, Ohio. It is intended to supplant the older 

 term Erie of Newberry because this was preoccupied by 

 Yanuxem. It consists of argillaceous and arenaceous shales,, 

 blue, grey and green in color. Dr. Newberry and in fact all 

 who worked on the problem down to the present thought that 

 it thinned down to a wedge from the east and that it was there- 

 fore bounded by the Cleveland shale above and the Huron shale 

 beneath. This misconception has given rise to many erroneous 

 conclusions and correlations. The fact is that the preponder- 

 ance of black shale over blue and grey shale is so great west of 

 the Yermillion Biver that it is quite impossible to pick out the 

 particular zone which forms the continuation of the typical 

 Chagrin. 



♦Consult figure 1 in this connection. 



f Age of Cleveland Shale, this Jour., xxxiii, p. 581, 1912, 



