THE GEOLOGICAL SECTION OF MICHIGAN 417 



There is good reason to suppose that during late Traverse there 

 was some emergence, while the hne between Dundee and Traverse 

 does not appear to be marked by a notable unconformity in Michigan. 

 We find also in New York the closest affihation in deposition between 

 Onondaga and Marcellus. The supposed unconformity at the top 

 and maximum depression at the base of the Traverse is in harmony 

 with the description by the Wisconsin Survey (ii, 397) of the beds there 

 as early Hamilton. 



27. Antrim shales. (Senecan, Genesee?, Portage and Chemung 

 of New York, Ohio) Huron, Chagrin, Cleveland, and Bedford. 

 480 to 140+ feet. — There is good reason in the thinning of the 

 formation and in the irregularity and reddening of the top to believe 

 in an elevation south of Michigan toward the close of the Traverse 

 (Hamilton). But in Iowa, too, the Upper Devonian is said to be 

 unconformable on the Middle. At the base of the Antrim shales on 

 Thunder Bay, Grabau found the Naples goniatite fauna which would 

 imply, perhaps, that the Antrim black shales though lithologically 

 like the Genesee were really somewhat later, and the Genesee miss- 

 ing. 



This horizon is struck very widely. The full thickness is not less 

 than 340 feet. In order to get consistent results and thickness one 

 must recognize that the transition to the Berea Grit is gradual and a 

 great thickness of Berea Grit or strata ascribed thereto is at the 

 expense of the Antrim. The Antrim consists mainly of shales, 

 black and bituminous at the bottom, then blue, and at top, where it 

 passes into the Berea Grit, or the horizon thereof, red or interstratified 

 with sandstones and gritty. 



To put the base of the Carboniferous at the base of the Bedford 

 we should have to split the Antrim in a very impracticable way, 

 though we could readily enough follow Ulrich's suggestion and place 

 it lower. It is noteworthy that just as the Sylvania is confined to 

 the east side of the basin along the Cincinnati anticlinal, so is the 

 Berea Grit, and when the Berea Grit does not appear, then the upper 

 strata of the Antrim have a red facies like the Bedford of Ohio, or 

 the Richmond top to the very similar Lorraine. This red facies is, 

 it seems to me, very likely due to exposure to the weather. Where 

 the Berea Grit is well developed it is, I believe, never found. It, 



