202 BRIGHAM—TOPOGRAPHY AND DEPOSITS OF MOHAWK VALLEY. 
above. If the barrier were below Little Falls, the corresponding water 
levels should be found below that place. Such have not been noted, 
though it has not been possible to make a careful study of the higher 
slopes. It would seem that powerful rapids led down to a lower water- 
plane, yet to be described, on the east. The gradual withdrawal of a 
tongue of ice from the upper Mohawk valley, as described by Chamber- 
lin, would have left a local lake, in whose quiet waters the fine clays, 
with glaciated pebbles, between Utica and Little Falls, were deposited. 
Later the Mohawk channel opened to the drainage from the west and a 
vast body of fine sands, with varying gravels, were laid down in the great 
lake-like river which swept eastward. The sediments from the main flow _ 
were commingled with delta and terrace material from local sources. 
- Any earlier or higher outflows to the east were probably temporary, leav- 
ing little record, until the 600-foot horizon is reached. Gradually the 
barrier was breached and the waters came down to the Iroquois level. 
Lake waters still extended eastward to Little Falls, owing to the presence 
of the gneissic barrier, and probably were maintained at that level through 
the lower valley for a considerable period. 
LOWER MOHAWK VALLEY 
East Creek delta.—This is a triangular area whose parts are symmet- 
rically disposed on either side of the creek above its entrance upon the 
Mohawk. It has not been mapped, and was but partially studied. It 
extends northward about a mile and a half. Westward it 1s prolonged 
into a narrow, somewhat morainic shoulder toward Little Falls. Hast- 
ward it breaks into a decidedly morainic belt which extends to Saint 
Johnsville. The height at the front is 110 feet above the Mohawk flood- 
plain, or 440 feet above the sea. It is bounded along the valley by a 
steep erosion bluff. 
Saint Johnsville bench.—At this village on either side of a local stream 
from the north is a somewhat morainic bench sloping toward the river 
and rising about 110 feet above the floodplain, or 480 feet above tide. 
A good section by the creek offers an exposure of 60 feet. 
Feet 
Fine, horizontally bedded sand, top................ DY 
Fine, thinly laminated black clay, without pebbles.. 8 
NVenyastonyeoluet till raere reenter rrnne arcs 25 
Fort Plain bench.—This extends, with uneven top, ina fairly continuous 
manner, nearly to Saint Johnsville on the west and eastward toward 
Canajoharie. It is bisected by the valley of Otsquago creek, but is only 
slightly related to it in origin. The Clinton Liberal Institute stands con- 
. 
