BLA CK SHALES OF OHIO— GENESEE SHALES OF NE W- YORK. 6 5 



Marshall group, and, subsequently, from studying the Waverly 

 group of Ohio, he recognized the identity of his Marshall group 

 with the Waverly group. 



Between these fossiliferous Marshall sandstones and the black 

 shales, in Michigan, nearly one thousand feet of rock beds of 

 prevalently shaly, partially sandy, and sometimes calcareous 

 character, are intercalated, which are claimed, by Professor Win- 

 chell as representatives of the Devonian fauna, with the same 

 emphasis as he asserts the carboniferous character of the 

 other. He combines them with the black shales into a sepa- 

 rate group, which he names Huron Shales. We will subse- 

 quently have occasion to learn that the shales, above the black 

 shale and below the Marshall sandstones of Michigan, inclose 

 absolutely the same fossils as are found in the Cuyahoga shales 

 of the Ohio geologists, and which by Winchell himself are con- 

 sidered as of a marked carboniferous faunal type, and as intimately 

 connected with the fossiliferous sandstones of Marshall. The 

 differences in the faunas are certainly not existing in this special 

 case, and viewing the question from a general standpoint, the 

 contrast between the fauna of the Chemung group and the fauna 

 of the Waverly group is by no means so striking, that for the one 

 a positively Devonian type can be claimed, and for the other a car- 

 boniferous. 



The group of the Huron Shales, according to this view, shrinks 

 back to the small basal portion of them, the black shales, which 

 have been long known under this name, and are likely to continue 

 to bear it for some time to come. 



Another objection to the adoption of this name is its similarity 

 to the name Huron groiip, in well-established use for the lower 

 metamorphic rock series of the Lake Superior district, which 

 would unavoidably cause much confusion. 



A belt of the black shale formation intersects the north part of 

 the peninsula. Its northern limits have already been delineated 

 in describing the southern limits of the Hamilton group, extend- 

 ing in an arch from Partridge Point, in Thunder Bay, to Nor- 

 wood, in Big Traverse Bay. The southern extension of this belt is 

 all hidden under drift deposits. Approximately, the slate belt is 

 supposed to extend on the west side to the neighborhood of 

 Frankfort, in the central part of the peninsula to Otsego Lake, and 

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