82 ICE RECESSION IX NEW ENGLAND 



section at the bottom of a hill shows the following layers, 

 beginning at the top : 



2 feet till, mostly blocks. 



4-8 feet silty and sandy disturbed clay. Varves M to 4 inches (1 to 

 10 cm.) thick. Varve limits difficult to distinguish. 



3-4 feet stratified sand. 



^3—3 feet disturbed varve clay. 



Thick varve clay with several disturbed zones and here and there 

 morainic material. The clay consists of sand or silt and of thick, 

 greasy clay la\-ers, but the varve limits, in many cases, cannot be 

 determined. At the bottom of the section the varves are sandy and 

 6 to 8 inches (15 to 20 cm.) thick, probably indicating inconsiderable 

 depth to the base of the deposit. 



The covering till may have been deposited by the land ice, 

 judging from Upham's statement that on the top of the hill, 

 the sides of which show till at the surface, a well 27 feet deep 

 encountered only varve clay. The consistency of the clay seems 

 also to show that it was deposited off a practically stationary 

 ice edge. The sand bed may mark a readvance almost to the 

 spot. After a short renewed retreat the ice overrode the clay 

 and deposited the till cover. 



This halt is not registered in the normal curve, because I did 

 not succeed in getting varve series so long that they bridged it 

 and could be connected with profiles north of the zone. In the 

 Connecticut Valley the Bellows Falls lake was filled up with 

 sediments probably about 300 years before the ice uncovered 

 localities 61 to 63 north of the zone of retardation. Not even 

 localities 41 and 43 can be connected with those south of them. 

 Nor is the halt recorded in the Merrimac Valley. The lake at 

 Concord also was filled up with sediments too early, though 

 certainly 75 years later than the Bellows Falls lake. As the ice 

 retired and began to uncover the outlet of the Winnepesaukee 

 basin, the drainage area, tributary to the Merrimac, became 

 very large, and the volume of water passing through very 

 considerable. The increase of the current was followed by 

 increase of the critical depth of clay sedimentation in the course 

 of the current. At points swept by the current sand was deposited 



