132 G. K. GILBERT DISLOCATION AT THTIITYMILK POINT, NEW YORK 



from the shore as tlie bottom could be observed witliout the aid of a 

 boat. 



Where the dislocation reappears toward the southeast in the lake cliff 

 there is no anticline, but instead a mouoclinal flexure, descending from 

 the uplifted mass at the northeast to tlie undisturljed mass at the south- 

 west. 



Above the cliff the general slopes of the land are gentle, presenting the 

 subdued contours of a ground moraine. From this even surface there 







— — ^ — ^^ Aa^ 



^^o 







■/ 



/ 





\ \ 





\ \ 





% X 





% X 





^■"^ \ 





% \ 





"%., 





"% 



O lOO 200 p|. p-^ 







Figure \. — Sketch Map of Thirtyviile Point. 



Sliowing relations of anticline and assoeiated ridge or terrace to the shore and shore cliff of lake 



Ontario. 



rises a low but unmistakable hill coincident in position with the anti- 

 cline (see figure 2). This indicates that the dislocation occurred after 

 the deposition of the till, for a ground moraine does not ordinarily' reflect 

 such topographic details on its surface. 



As already mentioned, the upper part of the anticline is overturned 

 toward the southwest. In the natural section its outlines are somewhat 

 indefinite, l^ecause the fractured rock is not readily discriminated from 

 the surrounding till, composed chiefly of the same material; but it is 



