SAYLES: THE SQUANTUM TILLITE. 



153 



farthest east on the peninsula of Squantum there are found many ex- 

 posvn-es of the tillite, and these different exposures range from near 

 the bottom to the very top of the tillite, with transition-beds to the 

 overlying slate. The strike of the slate here is N 63° E, and the dip 

 68° S. The thickness of the tillite is probably about 600 feet. The 

 matrix near the bottom is argillaceous, while higher up and at the top 

 it is a gritty argillite, and in one place is arenaceous. Boulders of 

 many kinds may be found, but the largest and most numerous are of 

 granite. The pebbles are angular, subangular, and rounded, and many 

 have blunt ends and concave fractures. Prof. J. B. Woodworth 



v:-::>'-.?^::::-v 



"M /•«'!i^'>*C* •• 

 •:..W:--:..r:-.--:/-.: 

 •"^K .'•jii' •'■•'•■#" • - 



••■«••>.■••■•:.•.'.••:..:•:>:•■.•?•**.: 



., • ,.-...•• .»,•• .•■■•. Of ... 



Fig. 1. — Disrupted sandstone in tillite: Squantum Southeast. 



found a striated pebble at this locality. The striae are very faint, 

 but with the aid of a pocket-lens appear perfectly characteristic. 



x\s stated above, the tillite here has a probable thickness of about 

 600 feet. There is no good evidence that the bed is doubled by fold- 

 ing and from the most northerly exposure to the upper transition-beds 

 the thickness is about as given. The lower contact with transition- 

 beds is probably hidden beneath drift and beach-shingle. I believe 

 that these lower transition-beds and a part of the Roxbury conglomer- 

 ate underlie the tillite here and have not been faulted out. At the 

 most northerly exposure and hence the lowest part of the tillite there 



