﻿GEOLOGY OF THOUSAND ISLANDS REGION 151 



stream erosion of the clays which constitute the bulk of the drift. 

 The existence of the Redwood lakes in the northern district is an 

 evidence of lack of drift filling. 



The normal and common form of drift in regions of glaciation, 

 the stony clay or clayey mixture of rock rubbish known as " till," 

 is widely found but in relatively small amount. The larger drift 

 masses are of three kinds: sandy or " kame " areas; boulder mo- 

 raines ; and pitted clay plains. The extensive plains of water-laid 

 clay are regarded as glacio-aqueous deposits, and are described in 

 a later chapter. 



Till. In the northern portion of the area, where the rocks are 

 Potsdam and crystallines and arenaceous materials prevail, the 

 scanty till is sandy and stony. In the southern district where the 

 strata are wholly limestone these give a clayey texture to the drift 

 sheet. 



The superficial till is usually incoherent and yellow or yellowish 

 gray in color. In a few places a compact, -hard, blue or blue gray 

 till may be found which is regarded as the product of ice action 

 earlier than the Wisconsin. The most massive exposures of the blue 

 till are found south of our area, at Watertown [p. 166]. 



No drift masses that could be definitely recognized as drumlin 

 have been noted in our territory, though they do occur over the 

 line on the south, north and south of Watertown. Some molding 

 of the till surfaces suggest drumlinizing of the drift, but appar- 

 ently the till was too scanty to be rubbed into definite drumlin 

 masses. 



Moraines. One heavy moraine lies in the southeast corner of 

 our area, between Black River and Evans Mills, mapped in plate 

 41. This is the only mass of drift of notable size in the limestone 

 district. In the northern part of the area, where the Potsdam sand- 

 stone and the knobby crystallines give irregular surface and rather 

 sharp relief, patches of rough and stony drift that may be re- 

 garded as morainal are quite frequent; but the only grouping 

 which merits the name of moraine belt lies about Clayton and east- 

 ward north of Lafargeville, shown in plate 46. In general it may 

 be said that the peripheral or morainal. drift is not collected in well 

 marked lines but is scattering, patchy and indefinite. In districts 

 where the Potsdam prevails at the surface, with scarps and ledges 

 that supplied very coarse material the ice-piled blocks are liable to be 

 confused with the postglacial debris from frost fracturing of the 

 jointed sandstone. As the Gilbert waters have rinsed away the 

 lighter drift from the higher masses it is not easy to readily dis- 



