ICE-RETREAT IN GLACIAL LAKE NEPONSET 191 



ordinary fore-set slopes, and probably representing deposits along 

 the subaqueous ice- wedge, afterward let down as irregular gradational 

 masses, as explained in the case of the East Sharon plains. 



The altitudes of the upper limit of the flat-top deposits indicates 

 that the Rattlesnake Hill outlet had been abandoned, and that a 

 newer and lower outlet to the south had been opened up through the 

 valley occupied by Ames Pond at a level of about 210 feet. The 

 ice had not entirely left the valley, a narrow tongue still remaining in 

 the center, along both sides of which, as indicated by terraces with 

 ice-contact slopes toward the valley, outflows took place. On the 

 west side the water followed straight through the valley, but on the 

 east side a portion passed off to the eastward by sub-outlets through 

 notches located respectively near where the highway crosses the pond 

 and just above the south end of the pond. 



West Stoughton lakelet. — The West Stoughton lakelet was a body 

 of water one and one-half miles long and one-half a mile wide, extend- 

 ing from Springdale on the north to a point about a mile west of 

 Stoughton on the south. The plain which now marks its position, 

 though fairly flat in places, is much more broken than most of the 

 other plains described, presenting in many places rolling and kettle 

 topography characteristic of deposition open and around more or 

 less detached sheets or blocks of ice. Fine ice-contact slopes extend 

 all the way around the edge from West Stoughton to Springdale, 

 marking the margin of the ice, still occupying the center of the valley. 



The elevation of the surface of the West Stoughton plains is from 

 190 to 200 feet. It seems to have been formed at a slightly later 

 period than the Elm Street plain. The lower altitude of its surface 

 is probably due to the fact that the ice in the depression now occupied 

 by Ames Pond (artificial) had finally disappeared, opening up an 

 outlet a few feet lower than that existing at the time the Elm Street 

 plain was formed. The surplus waters probably escaped through 

 the main and two sub-outlets in the vicinity of Ames Pond as in the 

 case of the Elm Street plain. 



Closing stages. — Within the limits of the Stoughton Bay area 

 there are no records of Lake Neponset later than the stage marked 

 by the deposition of the low level plains just described, unless certain 

 unimportant irregular deposits occurring in the center of the valley 



