352 PLEISTOCENE OF INDIANA AND MICHIGAN. 



EAST SIDE OF BASIN. 



The Glenwood beach from northern Indiana northward to Holland, Mich., is rather sandy 

 as a whole, though gravelly in numerous places. Cut banks are yery uncommon. The grav- 

 elly portions of the beach are the most definite and easiest to follow, for the sandy ones are 

 liable to be confused by sand drifting to higher altitudes. A most conspicuous sand ridge, 

 lying above the Glenwood beach a few miles south of St. Joseph, in the vicinity of Bridgman, 

 follows the crest of the Covert till ridge for a few miles and then passes down the outer slope 

 and runs some distance on the plain at its back. Its continuity is remarkable, especially since 

 it lies in places a mile or more east of the beach. That it was formed not by water but by wind 

 is clear from the fact that it reaches in places an altitude 50 or 60 feet higher than the Glen- 

 wood beach and has a range of fully 60 feet in altitude. 



Immediately south and east of Holland the Glenwood beach has exceptional strength, 

 shore deposits 25 feet or more in depth being banked against the inner or northwest slope of 

 the Covert till ridge. The beach is a sandy gravel which becomes in places nearly clear sand. 

 At the northeast this beach connects with a large delta formed by one of the distributary chan- 

 nels of the Grand River outlet, which separates from the present course of Grand River just 

 below Grand Rapids. Its delta covers 2 or 3 square miles in the vicinity of Zeeland and fills in 

 the space between two till ridges which lead northward from the old outlet. The gravel, 

 which is 25 feet or more in depth, is somewhat coarser than that of the beach south of Holland. 

 It was cut into and much of it removed by the Grand River outlet at a later and lower stage 

 of Lake Chicago, but its original level is preserved not only on the borders of the channel but in 

 island-like remnants in the midst of the channel. 



North of this delta Lake Chicago washed against the west side of the western till ridge, 

 but it deposited very little gravel, and the limits of the lake are not clear at all points. From 

 the northern end of this till ridge near Crisp the lake extended eastward about 10 miles across 

 Blendon into the edge of Georgetown Township, Ottawa County, to the eastern of the two till 

 ridges. On the western slope of the till ridge a somewhat definite gravelly beach connects at 

 the north with a large delta formed by the northern branch of the Grand River outlet. 



The delta of the northern branch of the Grand River outlet lies mainly in Allendale Town- 

 ship, Ottawa County, covering an area of about 30 square miles, roughly bounded by the 

 eastern till ridge on the southeast, by Bass River on the south and west, and by Grand River 

 on the north. The material is a fine gravel and its depth is 15 to 30 feet. The delta has been 

 trenched in its northern portion by the Grand River outlet, which has formed channels about 

 25 feet in depth and nearly a half mile in width which run entirely across the delta. This 

 trenching is an adjustment of the bed of the channel to a lower stage of Lake Chicago than 

 that marked by the Glenwood beach. 



North of Grand River the Glenwood beach sets in at Eastmanville and runs northward 

 along the western slope of the western till ridge, passing about a half mile east and north of 

 Dennison and coming to the valley of Crockery Creek at the line of Muskegon and Ottawa 

 counties. This portion of the beach is sandy and the precise level of the lake is in places 

 difficult to determine. 



In the sandy district that extends from Crockery Creek northward past Muskegon River 

 the limits of the lake are not easy to determine. The most definite line which the present writer 

 was able to follow lies along the eastern edge of a swampy tract about a mile west of the crest 

 of the western till ridge in sees. 20, 17, and 8, Ravenna Township. From sec. 8 the swamp 

 border bears westward across the south edge of sec. 6 and the northeast corner of Sullivan 

 Township to the western end of the west arm of the till ridge in the south part of sec. 35, 

 Eggleston Township, about 10 miles east of the main part of Muskegon. Farther north no 

 definite line was discovered, though the surface is a little more broken by ridges and ravines 

 east of a line passing from the west end of this tiU ridge to Wolf Lake in sec. 16, Eggleston 

 Township, than it is west of that line, and this change in topography may mark the lake border. 

 Some uncertainty, however, arises from the apparently higher altitude of the division line. 



