of the Hudson River Valley. 461 



tad j is the Mohawk delta, and the terraces of the Mohawk 

 valley are stream terraces. 



Recently Mr. J. "W*. Spencer- has advocated the hypothesis 

 that the raised beaches of the Ontario basin were formed at 

 sea-level. In this case the Mohawk valley terraces would be 

 estuary terraces homologous with those of the Hudson valley. 

 An examination of these terraces is necessary to determine the 

 point at issue. 



The delta of the Hudson River torrent has not yet been 

 studied by the writer, but it will probably be found in the 

 neighborhood of Sandy Hill. A general description of the 

 estuary deposits of the Champlain Period in this region has 

 been given by Professor W. W. Mather (Geol. 1st Dist. N. Y., 

 pp. 148, 149). 



Between Poughkeepsie and New York the following streams 

 have formed extensive delta deposits : "Wappinger's Creek 

 near New Hamburg, Fishkill Creek, Quassaic Creek at New- 

 btirgh, Moodna River at Cornwall, Indian Creek at Cold Spring, 

 Peek's Kill, Cedar Pond Brook and Minisceong Creek at Hav- 

 erstraw, Croton River, Pocantico River at Tarrytown, Sawmill 

 River at Yonkers and Tibbit's Brook at Yan Courtlandt Park, 

 New York City. 



The deposits of Peek's Kill or Annsville Cove, as it is now 

 called, are of considerable interest. These names designate the 

 basin which receives the waters of Annsville Creek, Sprout 

 Brook, and Peekskill Hollow Creek, the last of which carries 

 the drainage of several long and deep valleys trending to the 

 northeast through Putnam County. About the margin of the 

 basin are several terraces about 120 feet high showing charac- 

 teristic delta structure and on the west bank of the Hudson 

 opposite the village of Peekskill and immediately south of 

 Jones' Point is a terrace of coarse gravel which has the same 

 altitude as those on the east bank and which was, at one time, 

 regarded by the writer as a portion of the Peek's Kill delta 

 deposit. The coarseness of its material, however, would seem 

 to preclude the possibility of this and to suggest that it origi- 

 nated as a moraine or a kame and was subsequently terraced in 

 the waters of the estuary. On the flank of Crow's Nest Moun- 

 tain near West Point the base of the terrace exposed in the 

 railroad cutting is formed of bowlders of considerable size and 

 it is suggested by Mr. Gr. K. Gilbert that this deposit was 

 formed by a lobe of the retreating glacier. 



The estuary deposits of the Hudson River at New York 

 indicate a post-Glacial depression of more than 70 feet. The 

 terraces which border the west shore of Manhattan Island from 



* This Journal, vol. xl, p. 443 et seq. 

 Am. Joue. Sci.— Third Series, Yol. XLI, No. 246.— June, 1891. 

 31 



