INTRODUCTION 



This report relates to an area whose Pleistocene history, though 

 among the earliest to attract attention in this country, has re- 

 mained but vaguely known and has been often interpreted as 

 supporting contradictory views. The prevalence of clays in the 

 Hudson valley and the occurrence of terraces early led to the 

 general conception of its having been a marine strait connecting 

 the St Lawrence valley with the Atlantic on the south during the 

 Champlain period of Dana's chronology, and of its elevation and 

 denudation during the succeeding Terrace epoch of that geologist. 

 Of late years the very considerable enlargement of our knowledge 

 concerning the diversity of the glacial period and the recognition 

 of the manner in which gravels, s:\mls and clays associated with 

 retreating ice sheets have been laid down have so far modified 

 earlier opinions concerning the history of other fields, that the 

 state geologist, Dr F. J. H. Merrill, decided to undertake a survey 

 of the glacial deposits of This region for the purpose of obtaining 

 the information which it might give. One of the most important 

 questions which it seemed the region might be expected definitely 

 to determine is that of the extent of the marine submergence 

 which followed the withdrawal of the ice sheet from the Hudson 

 and Champlain valleys; to the solution of this question the data 

 set forth in this report are mainly contributory. 



For the better understanding of the conditions of deposition- of 

 the glacial deposits the physical geography of the region anterior 

 to the last ice advance is briefly set forth, so far as it is "at present 

 understood. To a limited extent the phenomena of the adjacent 

 regions in Xew England, New Jersey and Canada have been taken 

 into consideration where they appeared to throw light on the 

 problems of this district. 



The investigation has been carried on for the most part as a 

 reconnaissance of varying degrees of detail with reference to the 

 main problem in hand, points being sought for examination which 

 promised to be of critical value. It will thus appear when the 

 areas are mapped in detail that many interesting and perhaps 

 important facts have not been seen. It should be stated that the 



