212 K. M. hi lull* — S(r<((i<jr<(j)hic Relations of (he 



It is important to note, in seeking to determine the age of the 

 Huron shale, that the shale immediately underlying it, the 

 Olentangv of northern Ohio, is without question of Hamilton 

 age.* Evidence has been offered elsewhere in this paper indi- 

 cating the conformability of the Olentangy and the Huron. 

 It is, therefore; not surprising to find, as has been pointed out, 

 that the fossils of the Huron all find their equivalents or near- 

 est allies in the fauna of the Hamilton or Genesee. This 

 alignment of the Huron fauna affords unequivocal evidence 

 against the assumption of its Carboniferous age involved in the 

 overlap hypothesis, and consequently against this hypothesis 

 itself. 



Upper limit of the Devonian shales. — The diverse opinions 

 which have prevailed on this question among geologists are 

 well known. Professor Newberry, it will be remembered, 

 even placed the Chemung of New York in the Carboniferous 

 system. With his unique views regarding the place of the 

 Chemung in the general time scale, it is not surprising that he 

 should have at one time placed the Cleveland and " Erie " 

 (Chagrin) shales of Ohio both in the Carboniferous. f In recent 

 years geologists with few exceptions have discarded Newberry's 

 classification and agreed in placing the Devonian-Carboniferous 

 boundaiw above the Cleveland shale, either at the base or the 

 top of the Bedford shale. The official reports of the Ohio Sur- 

 vey since 1887 have generally placed it at the base of the Bed- 

 ford. Two recent papers^ on northern Ohio geology have 

 .placed this boundary at the top of the Bedford shale. The 

 faunal evidence for this assignment of the boundary has been 

 fully presented in the paper by Dr. Girty, to which the reader 

 is referred. There has recently become available through the 

 work of Prosser,§ Burroughs,! and Cnshing^f conclusive evi- 

 dence of an important unconformity at the top of the Bedford 

 shale which, in the judgment of the writer, strongly supports 

 from the physical side the evidence from the biological side 

 presented by Girty for placing the boundary between the 

 Devonian and Carboniferous sj'stems at the contact of the 

 Bedford shale and the Berea sandstone. This is the only strati- 

 graphic break which has been demonstrated to exist between 



*Stauffer, C. E. : The Hamilton in Ohio, Jour. Geology, vol. xv, p. 596, 

 1907. 



f Rep. Geol. Surv., Ohio, vol. iii, pt. 1, 1878, p. 18. 



\ Branson, E. B. : Notes on the Ohio shales and their faunas. Bull. Uni- 

 versity of Missouri, vol. ii, p. 28, 1912. Girty, G. H. : The geologic age of 

 the Bedford shale of Ohio, Annals N. Y. Acad. Sci., vol. xxi. 1912. 

 (In press.) 



S, Prosser, C. S. : Manuscript, reference in Jour. Geology, vol. xix, p. 257, 

 1911. 



|| Burroughs : The unconformity between the Bedford and Berea formations 

 of northern Ohio, Jour. Geol., vol. xix, pp. 655, 659, 1911. 



"} Gushing, H. P. : Manuscript. 



