PREVIOUS INVESTIGATIONS ON DRIFT DEPOSITS. 195 
discussing the clays and sands of the Hudson valley,* and cites the views 
of Gilbert and Spencer as to their nature. 
Taylor gives a short account of these accumulations and notes that they 
are deltas rather than true river terraces.t ‘ 
‘The drift of the Mohawk, as might be expected from difference of posi- 
- tion and greater complexity of relations, contrasts with the drift of the 
Chenango valley. The former has massive tills, few kames or kame ter- 
races, and affords lacustrine clays above the level of the floodplain. The 
latter has numerous masses of kame with frontal terraces, many kame 
terraces, no massive tills, and all its lacustrine clays are buried beneath 
the floodplain. 
The subsidence of glacial waters from the Warren to the Iroquois plane 
is as yet imperfectly understood. Gilbert refers to a baselevel higher 
than the Iroquois plane, “probably determined by an ice-dam in the 
lower Mohawk valley.”§ Fairchild has made known one important stage 
in this subsidence by his discovery of the Geneva beach, which he has 
described in detail and of which he gives this summarized account : 
“A well defined beach lying at an elevation of about 700 feet has been traced for 
30 miles along the western side of Seneca Lake valley and westward to Shortsville, 
while evidences of the same static water have been noted farther west. It is sup- 
posed that these phenomena belong to a long pause in the irregular fall of the 
Laurentian glacial waters from the Warren level to the Iroquois level,” || 
It is believed that the studies which follow throw light upon one addi- 
tional stage of thissubsidence. The bodies of drift lying between Wester- 
ville and Little Falls will be taken up in order. 
UPPER MOHAWK VALLEY 
Upper Mohawk delta.—This is the deposit made by the upper Mohawk 
at its entrance into the Iroquois basin. Only the southern portion, about 
Rome, has been mapped, and the study has Leen but partial. The slightly 
generalized map (plate 15, page 183) shows the principal relations at 
the head of the delta. At Westernville, 8 miles northward from Rome, 
the river leaves its deep trench in the northern plateau and makes a broad 
swing to the west past the village of Delta, returns to the east, bends 
sharply to the south, and passes through a gorge in the shales 80 feet 
*«F. J. H. Merrill: On the postglacial history of the Hudson River valley. Am. Jour. Sci., vol. xli, 
1891, p. 460. 
7See communications by F. B. Taylor and Warren Upham in the American Geologist, May and 
June, 1892. 
tA. P. Brigham: Glacial flood deposits in Chenango yalley. Bull. Geol. Soc. Am., vol. 8. 
_ @G. K. Gilbert: Old tracks of Erian drainage in western New York. Bull. Geol. Soc. Am., yol. 8, 
p. 286. 
| H. L. Fairchild: Glacial geology of western New York, Geological Magazine, December, 1897, 
Pp. 529-537, See also Bull, Geol, Soc, Am., vol, 8, p. 271. 
