182 



CAPE COD GEOLOGY 



Age. — The position of the Herod gravel, which lies above the Jacob sand 

 and below the Montauk till, shows that it is one of a series of beds that are 

 connected with the advance of the Montauk ice. These beds, including the 

 later Hempstead gravel, all form a larger unit. On Long Island these beds, 

 which compose the Manhasset formation, are regarded as equivalent to the 

 Illinoian by Fuller, 1 whose view seems to be supported by the evidence on 

 Marthas Vineyard. 



sw 







m 





NE 



— - -^fF^ 



-"""^ B 







A 





C c _^^L--^^ 







1 A ^- — ~~ 



Fig. 15. — Section at Stonewall Beach cliffs. A, Montauk till; B, Herod 

 gravel; C, Wisconsin till; D, clayey phase of Montauk till. 



Montauk Till Member 



Name. — The Montauk till was named from Montauk Point, Long Island, 

 where it is well exposed. The name is applied to the middle of the three sub- 

 divisions of the Manhasset formation. 



Character. — The Montauk till is the most conspicuous of the Pleistocene 

 deposits, and it differs greatly from all the others. It is made up of a mixture 

 of clay, sand, pebbles, and boulders, which form a very compact tough bed of 

 unmistakable till. (See Plates 24 and 25, fig. 1). Its composition on the whole is 

 fairly uniform, but in places it is very clayey, particularly near the Gardiners 

 clay, where it is composed of material reworked from that bed. In some of its 



sw 



20 FT 



100 YDS. 



Fig. 16. — Section exposed southwest of Cedar Tree Neck. A, Herod gravel; B, 

 Montauk till; C, gravelly phase of Montauk till; D, either Wisconsin or 

 Hempstead sand. 



exposures the Montauk is banded, in others it is massive. Its toughness, which 

 is one of its most notable features, is undoubtedly due to compression and 

 partial cementation, which have produced a bed of hard pan that cannot be 

 penetrated with a shovel. A secondary feature is its mode of erosion. "Where it 

 has been eroded by rain it has been cut into steep-sided gullies separated by pin- 

 nacles. (See Plate 25, fig. 1). Some areas of eroded Montauk resemble badlands. 



1 Fuller, M. L., op. tit., p. 132. 



