STRATIGRAPHIC SUMMARY. 631 



Group of northern Michigan. This comprises Upper Traverse or 

 Thunder Bay series, the middle Traverse or Alpena limestone 

 series and the lower Traverse or Presqiie Isle seriesr"^ In central 

 Ohio the Delazvare limestone and the Prout limestone represent a 

 part of the lower Hamilton, being followed after a hiatus by the 

 Upper Devonic Ohio shale. The Upper Devonic of Michigan is 

 represented by the black Antrim shale, including in its base the 

 Naples fauna. In Ohio the Ohio shale rests disconformably upon 

 lower Hamilton, upon Dundee (Columbus) or upon Siluric forma- 

 tions. In northern Ohio it can be subdivided in descending order 

 into Cleveland shale, Chagrin formation and Huron shale. The 

 Chagrin formation was called by Newberry the Erie shale, and is 

 represented, in part, by the Girard shale of northwestern Pennsyl- 

 vania. The Olentangy shale of central Ohio is regarded as a part 

 of the Ohio shale. In southern Indiana and Kentucky, the New 

 Albany black shale, representing late Devonic or younger horizon, 

 rests disconformably upon the Seller sburg beds, which represent 

 the Hamilton phase of the Middle Devonic, and are preceded by the 

 Jeffersonville limestone, commonly correlated with the Onondaga. 

 This rests disconformably upon the limestone of Lower Siluric 

 (Niagaran) age (Louisville). The whole of the Lower Devonic 

 and the Upper and Middle Siluric are wanting. 



In Wisconsin, the Milwaukee dolomite represents the middle 

 Hamilton and rests disconformably upon Monroan, or upon late 

 Niagaran. Its closest affinities lie with the Traverse group of the 

 Traverse Bay region. 



In Iowa, the subdivision of the Devonic is as follows (Calvin) : 



SUPERFORMATION. 



Carbonic. 



(Disconformity and hiatus.) 

 Upper Devonic. 



State quarry beds 40 ft. 



Lime Creek shales 120 ft. 



Owen beds. 

 Hackberry beds. 



Sweetland Creek shales 20 ft. 



(Hiatus and disconformity.) 



** Grabau, A. W., " The Traverse Group of Michigan," Geol. Sur. Mich. 



