GEOLOGY OF LAKE PLEASANT QUADRANGLE 6/ 



Extinct glacial lakes and their deposits 



Wells lake. There are several fine examples of extinct glacial 

 lakes within the quadrangle, all being here described for the first 

 time. One of these lakes occupied the bottom of the valley at Wells 

 as proved by a number of perfect delta deposits. The surface of 

 the lake stood at an altitude just a little over 1020 feet.^ The 

 finest flat-topped delta terrace extends from about one-fourth to 

 three-fourths of a mile north of the north end of the village and 

 is well shown on the map. Occasionally a low mound of boulder 

 morainic material projects above the surface of the delta deposit. 

 Where the main road to Lake Pleasant crosses its southern end, 

 the delta material is seen to be stratified coarse gravel and sand, with 

 lower level minor terraces developed by Postglacial stream cutting. 

 The boulder-free delta terrace at many places comes sharply against 

 the heavy boulder morainic deposits. Continuing northward beyond 

 the terrace for fully a mile, water-laid gravel may be seen along 

 the river road. 



A smaller though fine, flat-topped terrace of gravel one-half of a 

 mile long lies at 1020 feet just northeast of the mouth of Mill creek. 



The northern portion of the village rests upon a good terrace con- 

 sisting mostly of sand with some gravel at 1020 feet. This is too 

 narrow to be shown on the map. 



Another very distinct sand terrace one-fourth of a mile long 

 lies on the west side of the river at about one-fourth of a mile south 

 of the bridge at the lower end of the village. It is not shown on 

 the map. 



This lake was formed by a blockade of glacial drift or ice across 

 the Sacandaga river channel somewhere within a mile south of 

 the lower end of the village. The only possible' outlet of this lake 

 was over this drift or ice and the lake must have been short-lived, 

 due to a combination of rapid filling by delta deposits and rapid 

 downcutting through the dam. Much of the lake deposit has been 

 removed by the Sacandaga river since the existence of the lake. 

 The length of the lake was 3]^ miles with an average width of 

 from one-half to two-thirds of a mile. As would be expected, 

 the coarsest materials (largely gravels) are found in the northern 

 portion of the old lake bed, because the swift debris-laden ice there 



lit should of course be remembered that at the time of the existence of 

 this and other similar lakes of the quadrangle, the whole Adirondack region 

 stood several hundred feet lower than at present so that all lake levels were 

 correspondingly lower. 



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