WISCONSIN TILL 549 



of Great Boars head, Xew Hampshire, where a chff 20 feet high is well 

 exposed on a small drnmlin-like hill. The lower 10 to 12 feet is a hard 

 claye3rtill (Montauk) containing boulders up to 2 feet in diameter. The 

 upper surface of this till is yellowed to a depth of 2 to 5 feet. On top of 

 this rests a looser, heterogenous deposit consisting of sand mixed with 

 gravel and boulders up to 5 feet in diameter. The two types of deposit 

 are separated by a sharp line of demarkation, Avhich is somewhat irregular, 

 but slopes westward with the surface of the hill. Part of this cliff is 40 

 feet high, but this part is not well exposed. 



The exposures on Great Boars head and Little Boars head (figure 4) 

 are examples of a veneering of rather gravelly till which forms the sur- 

 face of most drumlins, although the coating is seldom so well marked and 

 never so well exposed elsewhere. In many cases the two types of till can 

 not be distinguished. In other cases the upper one is distinctly banded. 



In a railroad cut at the eastern end of a drumlin one-half mile north of 

 Revere station, on the Boston and Maine railroad, in Massachusetts, a 

 section was seen where a superficial gravelly till rests on an underlying 



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Figure 8. — Section of liuilroad Cat tJirouyh end of Drumlin, Revere, MassacJiusetts. 



Showing dike of Wisconsin till in Montauk till. A. concealed ; B, bouldery, clayey till ; 

 C, more gravelly and less clayey till. 



cla3'ey till, and the upper till forms a dike about 3 feet deep and several 

 inches Avide in the older till. The contact between the Uvo tills is very 

 sharp (see figure 8). 



Other cases of veneering of more recent till over older till were seen on 

 North ridge, Ipswich, Massachusetts, and on several drumlins south of 

 Boston. 



Drumlins are helieved to antedate pre-Wisconsin clay. — The veneering 

 of gravelly till is believed to explain certain peculiar relations of the 

 clavs to drumlins in northeastern Massachusetts. These relations are : 

 That although the marine brick clays have been seen to rest on till of 

 Montauk or drumlin tyj^e at many points, the clays ai-e just as sertainly 

 overlain by till in certain places which have been observed. Marbut and 

 Woodworth* have described many cases in Cambridge, Somerville, Saugus, 

 Eevere, and IMedford where till has been seen to overlie stratified clay. 



* Op. clt., pp. 995 et seq. 



