MODERN SUPERFICIAL DEPOSITS. 
345 
In the vicinity of Portage village, \vc find an immense deposit of coarse sand and gravel, 
piled upon an older deposit of sand and clay ; showing, subsequent to the period of the ancient 
drift, and after the great deposits of clay and sand following it — indeed apparently subsequent 
to the boulder period — a condition of things producing this immense local accumulation. 
The lower deposit is regularly stratified, and consists in part of materials of northern origin. 
This appears to have been partially excavated, and another deposit spread over it, of materials 
from the south, consisting of flat masses of sandstone and scarcely worn pebbles, with loam 
and gravel.* It is entirely distinct from the formation below, and proceeded from a long 
subsequent operation. It will be farther alluded to in connection with the recent production 
of valleys and river channels. 
The excavation of the Genesee Valley canal has given an opportunity of examining these 
deposits in a very satisfactory manner, and many facts have been brought to light. The 
surface alone, or the natural banks of the river, offer no opportunities of investigation. 
In the broad indentation on the eastern side of the river, opposite the middle falls, the canal 
passes along the slope of the hill, which rises nearly two hundred feet higher. The lowest 
deposit excavated at this point consists of alternating layers of clay and quicksand, which, 
about one hundred feet lower, rest upon the rocks of the Portage group, as illustrated in the 
following section : 
167. 
Section of the hill at Portage tunnel. 
1. Shales and sandstones of the Portage group. 
2 & 3. Regularly stratified deposit of clay and quicksand. 
4. Materials similar to those below, with fragments of trunks of trees in the lower part. 
5. Gravel and sand, having a large proportion of its materials of southern origin. 
a b, c. A superficial deposit, formed by the undermining of the hill above. 
a. The point at which the Genesee Valley canal is carried around the hill. 
* See Annual Report of 1840, pp. 439 and 440. 
44 
[Geol. 4th Dist.J 
