ICE-RETREAT IN GLACIAL LAKE NEPONSET 187 



At the time the deposits were laid down the ice probably presented 

 a fairly definite face to the lake, the position being not far from the 

 crest of the pass possibly near A. Later, however, the margin 

 became broken up into detached blocks at its edge, the location of 

 these blocks being represented by the imperfect planes and kettles 

 lying just north of the crest. Continuing to the north, the deposits 

 of stratified material end rather abruptly, the lower portions of the 

 northward-leading valley, through which the ice drew back, being 

 practically free from them. This would seem to indicate, either that 

 the glacial streams had been diverted at some point farther north, or 

 that they no longer carried any material quantities of sediments. 

 Otherwise the deposits would have continued to accumulate in the 

 lakelet which, in the later stages, must have reached some distance 

 to the north of the deposits previously noted. The waters passing 

 out from the lake to the south, being no longer overloaded with 

 materials carried in suspension, began the work of eroding out the 

 deposits laid down in the earlier stages, with the result that a thick- 

 ness of ten feet of sand and gravel was removed throughout nearly 

 the entire width of the valley leading south from the pass, the original 

 level being represented only by an occasional terrace remnant stand- 

 ing about ten feet above the present valley floor. Imbedded in the 

 silt, which here constitutes the floor, is a granitic bowlder, nearly 

 fifteen feet in diameter, probably stranded on the rock or till sur- 

 face underlying the silts during the melting of the ice and surrounded 

 by subsequent deposits of sand. 



East Sharon lakelet. — This name is applied to the body of water 

 which lay between the granitic hills, one and one-half miles south of 

 East Sharon, and the ice-front after the latter had shrunk back from 

 the valley sides. The lakelet had a total length of approximately 

 two and one-half miles. The greatest extent of open water was south 

 of East Sharon (southwest of West Stoughton), where the lake meas- 

 ured a mile or more across. A mile southwest of West Stoughton 

 the lake became contracted into what must have been simply a rather 

 broad and sluggish lateral stream,which, however, opened up again to 

 the southward into a marginal body, one-quarter of a mile or more in 

 width, which continued to the north base of Rattlesnake Hill. 



In this compound lakelet the deposits of the East Sharon stage 



