THE GEOLOGICAL SECTION OF MICHIGAN 405 



above the Sylvania, and it is not very easy, though it may be possible, 

 to separate off a part of the Monroe as Salina. The thicknesses given 

 by Grabau for the Monroe below the Sylvania add up 500 feet. 

 Salt occurs below the Sylvania usually within 450 feet. To the 

 southeast on the Cincinnati anticlinal the salt disappears. 



It is difficult to draw the upper line of the Salina in cases where 

 no salt exists, and that is the excuse for considering the Salina as 

 perhaps Lower Monroe. We have only lithological grounds to 

 identify it with the New York Salina, and it is altogether unlikely 

 that the top can be drawn consistently on such grounds. One can go 

 only 400 feet below the Sylvania sandstone if present and then take 

 the top of the nearest salt or gypsum bed. This gives fairly consistent 

 results. 



In the southwest part of the state, where no rock salt occurs, and 

 all the Dundee and Niagara together do not amount to the Upper 

 Monroe alone on the east side of the state, there was perhaps more 

 elevation and more exposure to erosion.' The samples from 1,490 

 feet to 1,730 feet at Kalamazoo represent the Upper and Middle 

 Ontarian and are dolomites with more or less anhydrite and quartz 

 and some red clay at 1,650 feet. 



Now if here was, part of the time, shore for land southwest, we 

 should expect to find still less deposition at Dowagiac. I am inclined, 

 therefore, now to raise the Niagara at Dowagiac even more than I did 

 over Wright in Vol. V, to wit, up to 1,100 or 1,135 ^^^t, taking in all 

 the light limestones. The Dowagiac Monroe would then be only 100 

 feet (1,000-1,100) dolomite with 10 to 30 per cent anhydrite and 

 quartz. If so, then the Niagara would come in the white limestone 

 at the base of the Niles well and the Monroe between 625 and 985. 



The outcrops near Milwaukee — the Waubakee dolomite of Alden, 

 Lower Helderberg of earlier writers — are probably higher than Salina. 

 At Ludington and Manistee, however, rock salt was struck, but 

 apparently there is but one layer. 



There is some question about a Ludington well put down by 

 J. S. Stearns, with samples suggesting the absence of the Dundee 

 there, and the presence of the Salina. But this agrees with Schu- 

 chert's Plate 75, and as we find over across the lake at Milwaukee 



I Schu chert, op. cit., PL 69. 



