PROBABLE REPRESENTATIVES OF PRE-WISCONSIN 

 TILL IN SOUTHEASTERN MASSACHUSETTS 



INTRODUCTION 



In the central portion of the country, where the glacial deposits 

 are spread out in a general northward retreating series of sheets, 

 the tills of the various ice invasions have long been differentiated 

 and classified chronologically with a considerable degree of cer- 

 tainty. In New England, however, each of the prominent 

 advances reached nearly or quite to the southern limit of the 

 area. The repeated passage of the ice over the region, and the 

 consequent severe glaciation to which it has been subjected, has 

 served to remove far more thoroughly than in the region further 

 west the evidences of pre-Pleistocene conditions and of early 

 Pleistocene tills. Under such conditions of glaciation, the pres- 

 ervation of remnants of the early tills would be very excep- 

 ional, and it is not strange, therefore, that deposits of these early 

 tills have not previously been found. 



While severe glaciation is the rule in New England, the action 

 has by no means been of the same severity throughout the area. 

 The area may be divided into three parts: (i) a northern belt 

 characterized by severe and almost universal erosion with cor- 

 respondingly little deposition; (2) a middle belt with generally 

 moderate, though sometimes locally severe glaciation, but char- 

 acterized as a whole by a marked deposition of subglacial till as 

 attested by its drumlins ; and (3) a southern belt of generally 

 weak erosion, except in the more exposed localities, accompa- 

 nied by a comparatively slight deposition of till. This southern 

 belt, the northern limit of which in eastern Massachusetts is a few 

 miles south of Boston, is nearly or quite destitute of drumlins, 

 rarely shows any evidences of severe glaciation such as charac- 

 terizes the northern belt, and is marked by the occurrence of 

 numerous instances of pre-glacially decayed rock surfaces. 



It was while engaged in field work on the surface geology of 



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