PAPERS PRESENTED AT GENERAL SESSIONS 69 



a territory in which pitted outwash plains show a most 

 remarkable development. East of McHenry on the east 

 side of Fox Eiver there is an outwash plain dotted with 

 numerous pits, yet made up entirely of gravel which has 

 a uniform summit level. 



THE FOX ETTER VALLEY 



• Fox River Valley appears to have had its inception 

 in the period following the deposition of the high out- 

 wash plain at Crystal Lake. Carpentersville and Dundee. 

 This is well shown northeast of Algonquin where 160 



r e the present river the outwash deposits lie at the 

 summit of both valley bluffs, the valley itself being 

 sharply entrenched. It is very clear from these relation- 

 ships that the Fox Eiver Valley was cut subsequent to 

 the deposition of the Crystal outwash plain. It also ap- 

 pears from the contour of the valley walls that the cutting 

 of this valley was rapid and was accomplished by a large 

 volume of water. \Ve do not know the source of this 

 water, because the later moraines to the east obscure the 

 topographic conditions which prevailed at that time, but 

 it is conjectured that the Fox River was an outlet of the 

 Great Lakes, similar to the old Chicago outlet but before 

 the deposition of the Valparaiso moraine. 



Following this period of valley cutting, there was a re- 

 advance of the Wisconsin ice, and it is to this advance 

 that the Valparaiso system of moraines is due. The ice 

 appears to have advanced as far as \Vest Chicago and 

 within two infhrs of Elgin, and two miles of Algonquin, a 

 notable moraine known as the v moraine 



marking its limit. Two miles northeasl *onquin this 



moraine descends into the Fox River Valley within about 

 set of the valley floor, which fixes the age of this mo- 

 raine as later than the carving of the valley. From the 

 front of this ice and subsequently from the ice which 

 built the Cary moraine, water poured down the Fox 

 River loaded with sand and gravel greater than the 

 transporting power of the stream, resulting in a partial 

 filling of the valley to a height of 80 to 90 feet, near Cary. 

 a valley train which may be traced with de- 

 creasing height down the Fox River to Ottawa at its 



