THE GEOLOGICAL SECTION OF MICHIGAN 399 



Island at Gore Bay report it 250 feet thick. I do not know any wel} 

 in the lower part of the state that has gone through it, but in wells 

 in northwestern Ohio it is said to be over 780 feet thick and in the 

 Carmen well at Petrolia, 602 feet. While called a limestone, in this 

 state it seems to be often dolomitic. 



13. Utica shale (Eden of Ohio). 50-80 feet.—In many parts of 

 the West geologists have consolidated all the shales over the Trenton 

 as Hudson River, Cincinnati, or Maquoketa. In Michigan we seem 

 well able to separate a black shale below, persistent and fairly uni- 

 form, varying in thickness from 50 feet at the north to about 200 feet 

 at the south. It does not seem to be separated by disconformity 

 above or below, and the conditions which produced it, widespread 

 as they were, we may well expect to be universal in the sea in which 

 it was formed. The correlations with the Utica or Eden of Ohio 

 and Utica of western New York seem perfectly satisfactory. The 

 base is well defined, but the line between it and the Lorraine above 

 is not sharp and probably not consistently drawn, and may some- 

 times have been carried up to the Waynesville, especially as none of 

 the wells are represented by samples every 25 feet or less. Generally 

 the Utica and Lorraine have been grouped together and mapped 

 with the Richmond, also as the Hudson River (Cincinnatian or 

 Maquoketa) . 



14. Lorraine or Maysville. — We must often include with Lorraine 

 the Richmond as well as the Maysville, which we cannot sharply 

 separate from this or the Medina. The beds are abundantly fossili- 

 ferous, and their correlation with the "blue limestone and marls" of the 

 Cincinnati and "upper beds of the Hudson River" is attested by 

 Hall, Winchell, and Rominger. The Wagner well shows for the 

 blue beds 150 feet and more, the Pickford well 215 feet, and the 

 breadth of the belt assigned to the Lorraine and the Utica on the 

 maps with a dip of 40 to 60 feet to the mile would indicate 350 to 

 450 feet. They probably thicken rapidly to the south at first, as 

 Cheboygan well would indicate over 343 feet, while on Manitoulin 

 Island there is but 285 feet between Niagara limestone and Trenton. 

 At the south end of the state the records indicate about 600 feet of 

 shaly beds to be divided between the Utica, Lorraine, Richmond 

 and Medina, say 200 feet Utica, 250 Lorraine, it^o Richmond and 



