REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1902 r35 



Deposits in the valley. Lake plains 



The valley deposits are somewhat complicated and can not be 

 completely differentiated without detailed study. The ice sheet 

 undoubtedly left considerable drift in the valley bottom and 

 along the sides, both till and kame. The drainage from a stretch 

 of the glacier front was concentrated in the valley to make 

 kames, moraine terraces and glacial deltas. The streams from 

 the side valleys spread their detritus on or alongside the ice lobe 

 or built deltas in the open lakes in front of the ice. When the ice 

 lobe had receded to near Utica, the waters were greatly augmented 

 by the inflow of the floods past the ice front which cut the 

 many channels described earlier in this paper. But the volume 

 of drift was correspondingly increased and it seems likely that a 

 lower section of the valley may have been entirely filled with 

 detritus to the level of the Little Falls barrier. 



In 1892 Taylor referred to the broad detrital plains at the 

 mouths of the larger creeks as deltas, indicating standing water 

 in the valley. Brigham described the deposits briefly in 1898 

 [see reference p. 22]. The writer's judgment, based on consider- 

 able study, is as follows regarding a few localities. The irregu- 

 lar gravel plains stretching 3 miles east of Herkimer and 

 some distance west are the eroded delta of West Canada creek, 

 the largest tributary of the Mohawk in the section under dis- 

 cussion. The area southeast of Ilion, showing the crinkled con- 

 tours, is not a kame area but eroded silts. The surface has free 

 drainage and no kettles [see pi. 26]. It might be a slack water 

 deposit accumulated in an embayment behind the Herkimer 

 delta; but its altitude is high. The suggestion is offered here 

 that possibly some deposits like this may represent lacustrine 

 beds of interglacial epochs, or deposits made in lakes of ice 

 advance. 1 Any deposit in water impounded by the first on- 

 coming of the ice sheet, and derived from the land wash, should 

 consist of fully oxidized material of atmospheric decay, and 

 with no material from the northward (unless some rare ice- 

 rafted inclusions). To diagnose such deposits will require care- 



Geol. Soc. Am. Bui. 1899. 7:430, 10:30. 



