SAYLES: THE SQUANTUM TILLITE. 157 
above and below the folds have not been deformed, it is difficult to 
see how the folds could have been formed by simple gravity, especially 
when it is noted that the folding and deposition were nearly contem- 
poraneous. 
There is some difference of opinion among geologists who have 
visited Squantum Head as to whether the tillite bed is doubled by 
folding and part of the exposure inverted. Dr. La Forge thinks that 
the strata on the north of the Head are inverted, and that the slate 
found both north and south of the tillite is the same bed. From a 
nile 
Ht 
® 
sy 
Fie. 2.— Hypothetical cross section of Squantum taken at right angles to 
the strike at Squantum Southeast. 1, Cambridge slate; 2, Tillite beds: 3, 
Lower slate; 4, Roxbury conglomerate. 
study of the Atlantic locality and a comparison of the beds there 
with those at Squantum Head I have come to a different conclusion. 
It is necessary to recall the order of the beds at Atlantic. In the midst 
of the tillite at Atlantic there is an intercalated bed of gravel of 
small thickness. Near the middle of the main tillite at Squantum 
Head there is an intercalated bed of gravel from 15 to 30 feet thick. 
Under the main tillite formation at Atlantic there is a bed of sandstone 
about twenty-five feet thick. There is a bed of sandstone of about 
the same thickness on the north side of Squantum Head in contact 
with the main body of the tillite. Under the tillite at Atlantic there 
