lO NEW YORK STATE MUSEUM 



along the belt of contact between the old crystallines and the onlap- 

 ping Ordovicic sediments ; and during the development of the valley 

 the axis of the valley has shifted westward against the outcrop of 

 the sedimentaries. 



OUTLINE OF THE LAKE HISTORY 



This history is concerned with the waning and disappearance 

 from the region of the latest or Wisconsin ice sheet, though it is 

 Cjuite probable that this history may be a duplication of that of earlier 

 ice recessions. Some topographic features, like those in the Water- 

 town district (the Rutland Hollow valley for example), may be the 

 cumulative effect of multiple advances and recessions of the ice 

 sheets. 



The three broad elements in the history are: (i) the larger 

 features of the land relief (described above), or the topographic 

 control over the ice movement and the water flow ; (2) the waning 

 ice body on the north, acting as a receding dam and holding the 

 imprisoned waters up to certain outlets of escape; (3) the im- 

 pounded waters finding lower and lower escape in different direc- 

 tions, as shown by the outlet channels and the lake plains. 



The glacial waters of the Black valley had four main stages, deter- 

 mined by four principal directions of escape. The first and highest 

 stage was that of waters not limited to the Black valley but extend- 

 ing into the Mohawk area and controlled by outlets from the latter. 

 The second stage had overflow to the southeast, through Remsen 

 into the waters held in the Mohawk valley, the altitude of the chan- 

 nel heads being 1240 feet. The third outflow was at Boonville to 

 the southwest, cutting the Lansing kill gorge, with ultimate escape 

 to the Mohawk valley. The fourth and less simple stage was con- 

 trolled by westward escape around the north end of the great ridge 

 which separates the Black valley from the east end of the Ontario 

 basin, comprising water levels from 1200 down to the Lake Iroquois 

 plane, about 735 feet in the Carthage- Watertown district. The 

 complete history must include the Iroquois waters, which flooded 

 the lower end of the Black valley. 



FIRST stage: MOHAWK WATERS; HERKIMER LAKE 



There seems to have been a stage in the waning of the ice sheet 

 when the Ontarian lobe, pushing east over the district of Oneida 

 lake and Rome, thrust its front, with a northwest-southeast trend, 

 against the foothills of the southwest flank of the Adirondacks. 



