SAYLES: THE SQUANTUM TILLITE. 153 
farthest east on the peninsula of Squantum there are found many ex- 
posures 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 
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. 
As 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 
