218 PLEISTOCENE OF INDIANA AND MICHIGAN. 



uncommon, though most of them contain a little till. The marked differences are probably 

 referable in part to drainage conditions attending the deposition of the drift and in part to 

 original sandiness of the material embedded in the ice. Mr. Taylor 1 has caUed attention to 

 the fact that the gravelly and sandy portion of the morainic system coincides in extent with 

 the belt of prominent dunes along the shore of Lake Michigan and has suggested that the great 

 abundance of sand in this portion of the moraine may be due to its blowing in from lake dunes 

 during an interglacial interval. Probably, however, the principal factor has been the glacial 

 drainage, which was exceptionally vigorous in the region. Furthermore, the sandy and gravelly 

 character of the drift extends eastward over several counties hi southern Michigan beyond the 

 reach of the Lake Michigan dunes. 



Well records setting forth the structure of the drift along this morainic system have already 

 appeared in other publications. 2 



BOWLDERS. 



Bowlders in moderate number strew the surface of the moraine, but are on the whole less 

 abundant than in the Kalamazoo morainic system. The great majority are crystalline rocks of 

 Canadian derivation 3 feet or less in diameter. A few immense bowlders of limestone and sand- 

 stone were noted in western Van Buren County. 



In western Bangor Township sandstone bowlders are scattered over a tract about 1 J miles 

 from north to south and scarcely one-half mile in width, but are most abundant in sees. 16 and 

 17, and especially on a prominent knoll on the section line. One bowlder on this knoll supplied 

 stone to build a large house in Hartford. Two others still remain, one measuring 24 by 21 by 

 21 feet on the sides, and the other 30 by 18 by 15 feet; each stands 6 or 8 feet above the 

 surface and extends to an undetermined depth — one of them to at least 6 feet. Similar bowl- 

 ders are scattered over Bloommgdale Township, in a belt nearly 3 miles in length and about one- 

 fourth mile in 'width, extending from near the base line in sec. 4 south into sec. 17, about half a 

 mile west of Bloommgdale station. They appear on the most prominent points along this line, 

 but are scarce on the lowland between the knolls. They are embedded in the ground at various 

 angles, some standing nearly on edge. The largest measure 15 to 20 feet and stand 6 to 8 feet 

 above the surface. Similar large sandstone bowlders are reported from sec. 33, Blo'omingdale 

 Township, but were not visited by the writer. These sandstones are mainly red or pink or 

 more rarely brown. They have some of the characteristics of the Potsdam sandstone, but their 

 geologic horizon has not yet been fuUy settled. 



A large limestone block in sec. 11, Hartford Township, had been uncovered at the time of 

 the writer's visit over about 16 feet square and had been quarried to a depth of about 3 feet, 

 yet neither its lateral limits nor its bottom had been reached. A bowlder of the same kind of 

 limestone occurs on the base line between Bloommgdale and Cheshire townships less than a 

 mile west of the north end of the sandstone bowlder belt above noted. It, however, is only 

 about 5 feet cube. A large limestone bowlder in Van Buren County was examined by Alexander 

 WincheU and was referred by him to the "Corniferous." Winchell supposed the bowlder to 

 have been transported from the western end of Lake Erie, but the Erie ice movement can 

 scarcely have extended to Van Buren County. It is more probable that it was derived from 

 ledges to the north of Van Buren County. 



OUTWASH. 



The drift is gravelly or sandy aU along the outer border of the Valparaiso morainic system 

 from its junction with the correlative moraine of the Saginaw lobe in southern Kent County, 

 Mich., southward to the edge of the Kankakee Marsh in Porter County, Ind. Characteristic 

 pitted plains, forming outwash aprons along a considerable part of the border, slope rapidly 

 away toward the lower land along the inner border of the Kalamazoo morainic system. It is 



1 Personal communication. 



2 For wells in Illinois and southwestern Michigan see Mon. U. S. Geol. Survey, vol. 3S; for wells in northern Indiana see Water-Supply Paper 

 U.S. Geol. Survey No. 21; for records of flowing wells in the lowlands among the morainic knolls and ridges of this system see Water-Supply Paper 

 U. S. Geol. Survey No. 182. 



