THE ILLINOIAN ICE INVASION 321 



In Bay County a number of coal shafts penetrate several tills and inter- 

 glacial deposits. 167 These are tabulated below : 



Near Amelith. Shaft of Pittsburg Coal Co. 



Soil deposit at 110 feet, underlaid by beds of sand and gravel and overlaid by clay drift 



of Wisconsin age. 

 Shaft of Hecla mine, northeastern part of Frankenlust Township. 



Fragments of trees in beds of sand just above the bed rock, at a depth of 85 feet. This 



vegetal deposit is probably contemporaneous in age with the 110 foot bed near Amelith, 



which may be Sangamon. 

 Section 19, Bangor Township. 



Vegetation at 80 feet, underlaid by 37 feet of boulder clay. 



In the old Monitor shaft (S.E. i^ Sect. 28, T. 14 N, R. 4 E.) at a depth of 

 45 feet a vegetal deposit was found. 



Section of Monitor Shaft 



1. Clay 45 feet 



2. Upper Monitor soil 4J^ " 



3. Clay 31}^ " 



4. Sand, lower Monitor soil 10 inches 



The upper Monitor soil contains impressions of leaves, twigs, etc. Just 

 what relation the two clays and the two soils bear to the intervals beyond the 

 Wisconsin is not clear. If there was an lowan drift in Michigan number 3 

 might be this one; or it might be early Wisconsin drift. The stratigraphical 

 position of these deposits is not yet clear. 



At two localities in the Upper Peninsular, one near Hessel and the other 

 in the region about Isabella, to the north of Big Bay de Noc, there are deposits 

 of fine, pink, thinly laminated, highly plastic clay which as shown by its fine- 

 ness and evenness of bedding was laid down in a large water body. 168 Similar 

 clay is perhaps present at other localities in the same general region, concealed 

 beneath deposits of sand and possibly of till, but evidence in this connection 

 is at present wanting. Of these deposits Russell says, "The deposits of clay 

 briefly described above, are of the same character as much larger deposits 

 exposed near Sault Ste. Marie and occurring widely on the Lake Superior shore 

 of Michigan. Judging from the pronounced physical characteristics of the 

 clay at these several localities and its known relation to other and associated 

 deposits, it seems evident that it was laid down in a single widely extended 

 water body. No fossils have been found in it to show whether it is of marine or 

 lacustrine origin, but the presumption is that it was deposited in a lake. As 

 to the date at which this lake existed no good evidence has as yet been obtained 

 in Northern Michigan, but during the past summer similar clay previously 

 known to exist in the northern portion of southern Michigan has been shown 



187 Cooper, Rep. State Board Geol. Surv., 1905, pp. 152, 340, 341. 

 '«» Russell, Rep. Geol. Surv. Mich., 1904, pp. 93-94. 



