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 Avere 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 



Fig. 2. — Hypothetical cross section of Squantum taken at right angles to 

 the strike at Squantum Southeast. 1, Cambridge slate; 2, TiUite 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 bodv of the tillite. Under the tillite at Atlantic there 



