GLACIAL LAKE CHICAGO. 351 



SOUTH END OF BASIN. 



The altitude of the beach at the southern end of the Lake Michigan basin, as found by 

 Goldthwait's levels in Cook and Lake counties, 111., and Kenosha County, Wis., is not over 638 

 feet above sea level and was determined apparently by the level of the Chicago outlet at the 

 time it was forming. The Glenwood beach in the Chicago district and northward to Racine is 

 in places split up into three or more distinct crests, and it is probable that the outlet was lowered 

 slightly during the development of the beach. 



In the Illinois part of the Glenwood beach cut banks are more common than ridges of gravel 

 or sand thrown up by the waves. The gravel ridges are chiefly at embayments where bars were 

 projected out into tbe water by currents working along the shore. But from Waukegan north 

 to Eacine a gravel ridge prevails, as noted by Goldthwait. From Glenwood eastward about 

 to Chesterton, Ind., deposits of gravel and sand are conspicuous and the beach is in places com- 

 posed of a series of parallel ridges separated by narrow sags. Where sandy and subject to wind 

 action the beach is thrown up to a height of 25 or 30 feet, but where gravelly it in few places rises 

 10 feet above the bordering plains. The ridges are somewhat disjointed and have a tendency to 

 overlap. 



The shallow waters of the lake apparently extended in places into bays or up valleys in 

 which the wave action was insufficient to develop the beach thoroughly. From one of these 

 extensions in Deep River valley near Hobart the water perhaps extended along Turkey Creek to 

 the main beach a few miles west of Hobart. A bay in Salt Creek valley extended 3 or 4 miles 

 south of the main beach, and still another extended up Calumet Valley about to the east line of 

 Porter County, Ind. Much of the area covered by this last bay is thinly coated with sand. 

 East of Hobart the sand is slightly ridged, but generally it is flat surfaced. 



A bay also occupied East and West Trail Creek valleys on the southeast or outer border of 

 a till ridge of the Lake Border morainic system, connecting with Lake Chicago through a gap in 

 the till ridge now utilized by Trail Creek below the junction of the two forks. Another bay occu- 

 pied the lower courses of the forks of Galien River in southern Berrien County, Mich., back of the 

 Covert till ridge. This bay and the one in the Trail Creek drainage basin stand in the line of 

 drainage of the small glacial lake that occupied the lower course of the St. Joseph and Paw Paw 

 valleys and discharged southwestward to the incipient Lake Chicago at Chesterton (pp. 226-227). 

 Deposits of sand several feet deep along the line of these pools may be in part the deposit of this 

 drainage, and thus antedate the Glenwood beach. The small lake in the St. Joseph and Paw 

 Paw valleys stood somewhat higher than the Glenwood beach and probably each of the pools 

 through which it discharged was a little above the level of that beach, for they were too low 

 to be connected by a stream but opened severally through gaps in the till ridge to the west to 

 Lake Chicago. 



Another small bay near the confluence of Paw Paw and St. Joseph rivers opened into Lake 

 Chicago at the present mouth of St. Joseph River. The portion of the Covert till ridge immedi- 

 ately south of St. Joseph was nearly submerged, so that the waters of Lake Chicago may have 

 rolled over it into the bay back of the ridge. The portion of the till ridge north of St. Joseph 

 River rose considerably above the level of the lake and bay. 



Still another bay lay back of Covert till ridge at the junction of the several forks of Black 

 River east of South Haven, and opened into the lake near the site of that city. The lake 

 rolled over the crest of the Covert till ridge into this bay for a short distance in the vicinity 

 of South Haven. A definite beach was found east of the bay for 4 or 5 mdes south of Kibbe 

 station. 



At Kalamazoo Valley the till ridge runs back from the shore of Lake Michigan to New 

 Richmond, causing a sharp embayment in Lake Chicago itself west of the ridge. The sub- 

 mergence extended east of the ridge but covered an area very much smaller than that of the 

 glacial lake that covered the same region while the ridge was in process of formation, the water 

 standing 35 or 40 feet lower than at the earlier stage. 



