LOWER MOHAWK VALLEY DELTAS AND BENCHES. 203 
gpicuously on it, and the higher parts of the town both east and west. 
The height may be averaged at 125 feet, or 431 feet above sealevel. The 
chief and basal constituent of the mass is very stony till. This is usually 
overlain by a moderate though variable thickness of sands and gravels. 
Many exposures are afforded by the cuts of the West Shore railway. 
The high bluff facing the creek on the east side gives the following 
section : 
Feet. 
Till, moderately stony, oxidized, scratches obscure, contains sandy layer.... 10-15 
Waterlaid material, light sands below, sandy clay above..................- 15-20 
Base, very tough, stony blue clay, stones freshly scratched............. .. 25-30 
Cayadutta (Fonda) delta. —The term is used with qualification. In and 
about Fonda are massive stony tills, extending up the creek one and a 
half miles, the edges of the till showing ice contact rather than erosion. 
Rising out of the creek valley to the west a level tract stretches westward 
toward Yosts and the Noses fault scarp at an altitude of 440 feet. This 
area is well shown upon the Fonda sheet. The surface is sandy, free 
from stone, smooth as a floor, and rises gently to the lower slopes north- 
ward. ‘The general section, as learned from a resident, is sand, 6 to 15 
or 20 feet, then often gravel, followed sometimes by fine clay without 
stones. Ata greater depth the till would doubtless be entered. 
The deposits represent a lacustrine expansion of the river, when held 
at this level, aggrading to a uniform surface above the till. Some stone 
fences were seen, but it was learned that all the material was brought 
from the hills to the northwest. 
Schoharie Creek deltan—The conditions are similar to those at Fonda, 
with massive till at the mouth of the valley, a slight bench on the east, 
anda large triangular area stretching westward, extending by Auries- 
ville to near Fultonville, at altitudes ranging from 420 to 440 feet. The 
proportion of true delta material is not well determined, nor were good 
structure sections found. ‘The Mohawk floodplain is very broad where 
the creek enters, and no doubt extensive deposits have been swept away. 
At the top of the drift bluff about Auriesville lacustrine clays and sands 
were found, apparently in the same relations as at Saint Johnsville and 
near Donen 
Amsterdam benches.—At Aiken, 3 miles to the west, boulder-clay is over- 
lain by highly inclined beds of sand and gravel. North of Spring street, 
in Amsterdam, and at the cemetery and “Cork hill” a very tumultuous 
assemblage of sands, gravels, and clays is found. The sections were 
somewhat obscured, but, without much doubt, till is overlain by strati- 
fied beds. Thealtitude is 420 to 440 feet. Atthe top ofasimilar shoulder 
on the south side 5 feet of pebbly loam are underlain by lacustrine clay 
