THE GEOLOGICAL SECTION OF MICHIGAN 421 



Alma has sandstone, black shale, and limestone between 1,575 ^^^ 

 1,740 feet, i.e., 560 feet below the top of the Marshall, corresponding 

 to Bay City 1,630 feet in the well of Vol. V (Atlantic Mill), 750 feet 

 in the South Bay City well. This we may strongly suspect includes 

 the upper part of the Coldwater down to Herrick's conglomerate i, 

 the Black Hand and Raccoon. 



In the Charlotte well from 570-680 feet is sandrock, from 680- 

 1,150 appearing to be shaly limestone, if the samples are representative. 

 There are 350 feet below down to the Berea horizon. So at Jackson 

 is a salty rock at 660 which, in Vol. V, I took to be the Napoleon, but 

 I am quite sure that I was mistaken. This would seem to be an 

 •appearance of the Michigan series, or rather a Kinderhook facies 

 and an incursion of the western Carboniferous during the Coldwater. 

 It looks as though at about this time (that of the Coldwater and Mar- 

 shall) the eastern side went up, the western side down, and that 

 corresponds with what is known of the continent in a large way.^ 



The abundance of goniatites in the sandy beach-like beds of the 

 Lower Marshall suggests that they were open to the western ocean, 

 and we should expect an even more Kinderhook facies in the Upper 

 Coldwater and Lower Marshall of the western part of the state. 

 Unfortunately there is not the slightest chance of outcrops of this 

 calcareous Lower Marshall or Upper Coldwater, but possibly some 

 fragments of the fauna might be identified in the drift back of 

 Ludington. 



The Coldwater is an emergent formation and gradually passes 

 into the sandier facies of the Lower Marshall; where to draw the 

 hne will be discussed in connection with the Marshall. The Cold- 

 water appears to be nearly as thick even if more calcareous to the 

 west, the total for Lower Marshall and Coldwater being always a 

 little over 1,000 feet. 



30. Marshall sandstone (Raccoon possibly. Black Hand and 

 Logan of Ohio in part). — This formation was extensively studied by 

 Professor A. Winchell who, in distinction from earlier writers, recog- 

 nized the Carboniferous type of its fauna, when he first introduced 

 the term (report for i860). He made a heavy sandstone which he 

 called the Napoleon the base of the Carboniferous, and called the 



I Compare Schuchert, Pis. 78 and 79. 



