PROOFS OF SUBMERGENCE 



^89 



and at least the west end of Long Island. The reader will admit that if 

 it can be clearly shown that the lower Hudson Valley at the time of the 

 removal of the latest ice-sheet stood at least 100 feet below its present 

 attitude, then at least the west portion of Long Island must have been 

 involved in the submergence and subsequent uplift. And the proofs for 

 the Hudson Valley are incontrovertible. AM students of the rost-Glacial 

 deposits of the valley agree that they are estaurine. We will listen to the 

 testimony of several eminent authorities. 



In 1891 F. J. II. Merrill wrote as follows (11,, pages 103-106) : 



"These deposits are of two geuer.il types: estuary formations of stratilied 

 clay and fine sand deposited in still water and cross-bedded delta deposits of 

 coarser material. They fringe the river shores in terraces between New York 

 and Albany and indicate a long period of submergence, their present altitude 

 above tide showing that the land has been elevated with respect to sealevel 

 since their formation. Their materials were apparently brought into the 

 estuary by tributary streams which dropped the coarsest particles near their 

 mouths, while the finer rock-flour was carried on in a state of suspension, and 

 was finally precipitated to form beds of clay, 



"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 Seventy-fifth street northward have a maxi- 

 mum height of 70 to 75 feet, and on the New Jersey shore of the river ter- 

 races of about the same altitude occur at frequent intervals. One of the most 

 prominent of these is at Fort Lee, south of the steamboat landing. The sur- 

 face material of these terraces is a fine sand or silt easily transported by the 

 wind. It is evidently not a material which could be laid down in running 

 water, for it would be carried in suspension by a river current and could only 

 be precipitated in the still water of an estuary. . . . 



"On the Long Island shore of Westchester County, New York, the till which 

 covers the metamorphic rocks has apparently been leveled off by wave action 

 at an altitude of 75 to 85 feet. Plains of this character occur at fi-equent 

 intervals, being separated by river valleys, and were probably formed during 

 the depression which occasioned the estuary deposits of the Hudson River 

 valley. These plains are composed of a modified till, obscurely stratified, 

 somewhat sandy near the surface and comparatively free from boulders, but 

 unaltered boulder-clay or till occurs a few feet below their surface. On one 

 of the most extensive of them the village of New Rochelle is built. . . . 



"From the evidence quoted the amount of the post-glacial depression at New 

 York is estimated at about 80 feet. . . . 



"In the estuary which occupied the Hudson River valley during the depres- 

 sion there was deposited a great depth of plastic clay, evidently a sediment 

 of aluminous rock-flour produced by glacial attrition, and held in suspension 

 by the post-glacial streams, and resting on this clay is a deposit of fine strati- 

 fied sand." . . . 



In his book on the clays of New York^ Ries introduces his description 

 of the clays in the Hudson A^ alley as follows (15^ page 576) : 



