512 F. G. CLAPP GLACIAL PERIOD IN NEW ENGLAND 



to the rocky nature of the coasts and the less -settled condition of the 

 region, many difficulties are found in the solution of Pleistocene problems 

 that are not found farther south. In northeastern New England a care- 

 ful search for exposed sections is necessary, and most of those found are 

 poor. The nature of the writer's work did not permit him to spend 

 much time hunting for exposures, and tlie facts here presented are 

 therefore but a small part of the evidence which might be collected by 

 systematic field studies on this problem. Absolute correlations are not 

 yet possible, and such as are here presented should be considered merely 

 in the nature of suggestions, as showing what appears to be the most 

 probable age of the various deposits. The observations thus far made 

 and the conclusions derived from them are given with the hope that they 

 may be of some assistance to future investigators along this line. 



Classes of Evidence 



The evidences which indicate the complexit}^ and succession of Pleisto- 

 cene deposits in northeastern Massachusetts, southeastern New Hamp- 

 shire, and southern Maine are as follows : 



1. The occurrence of old tills differing in structure, relations, and com- 

 position from the more common and superficial types of till. 



2. Evidences for the differentiation and correlation of the so-called 

 "Leda clay." 



3. Differences in distribution and topography of the clays. 



4. Erosion unconformities representing time intervals. 



5. Till and morainal deposits overlying marine clay and stratified sand. 



6. Folding and erosion of stratified sand, clay, and gravel deposits 

 which must have been originally horizontal, and modification of clay sur- 

 faces by overriding ice. 



7. Different degrees of oxidation and weathering of the deposits. 



8. Buried soil zones. 



Pleistocene Succession 



In order to give a good idea of the relations of the different types of 

 deposits descriljed in the following pages, a tal^ulated summary is here 

 presented, with the possible correlations. The correlations with south- 

 eastern Massachusetts are probably correct, and those with the deposits 

 described by Fuller and Veatch on Long island are probably approxi- 

 mately correct, but those with the Mississippi valley are simply postulated. 

 In these latter oorrolatio7is tlio writer lias followed Fuller and Woodworlli, 



