CAPE COD GEOLOGY 



259 



clays at North Cambridge at a horizon that is presumably equivalent to the 

 Gardiners clay. No boulders have been found in the clay at Highland Light 

 and in the third cliff at Scituate in sections that are similar to those of the 

 Gardiners formation on the islands, so that the clay at Barnstable and in the 

 valleys of the Charles and Mystic rivers may lie either at the horizon of the 

 Montauk boulder clay or at a lower horizon than the Gardiners clay. They 

 may be the equivalent of one of the stony blue clays near the base of the Pleis- 

 tocene section. 



JACOB (?) SAND 



The assumption that the clay at Highland Light represents the Gardiners 

 clay involves the correlation of the overlying beds of yellowish fine sand with 

 the Jacob sand on the islands to the southwest. Sandy beds also overlie the beds 

 of clay about Pleasant Bay and in the brick-pits at West Barnstable. If, how- 

 ever, the boulder-bearing clays along the shore of the Bay represented the 

 Montauk till these beds of sand should be regarded as Hempstead beds. Large 

 tracts of sand and gravel overlie the clay along the south coast of Cape Cod 

 Bay. These tracts lie beneath the veneer of frontal moraine which covers the 

 district. Some reasons for regarding both the sand and the gravel as newer than 

 the Jacob sand are set forth below. 



MANHASSET FORMATION (?) 

 Herod Gravel Member (?) 



On /the islands the Herod gravel underlies the Montauk till or boulder 

 clay, occurring very much as the Jameco gravel occurs beneath the Gardiners 

 clay. The Herod normally overlies the Jacob sand, which may in places be 

 gravelly. If the boulder clay in Barnstable is the Gardiners clay the overly- 

 ing beds of gravel in the tabular hills along the coast of the Bay at the foot 

 of the moraine represent the Herod member; but if the beds of clay are re- 

 garded as the equivalent of the Montauk till, the Herod would be found below 

 sea level, and the gravel lying above the clay must be the equivalent of the 

 Hempstead gravel. South of the frontal moraine, which consists mainly of sand, 

 there is a broad expanse of sand and gravel that is evidently older than the 

 outwash from the Falmouth moraine. 



Montauk Till Member (?) 



Along the south shore of the Bay from Barnstable westward to the Cape 

 Cod Canal there are beds of clay that are said to contain large boulders, such as 



