CAPE COD GEOLOGY 65 



DEFORMATION AND DISLOCATION OF BEDS BY GLACIAL THRUST 

 The folding and overthrusting seen in the Cretaceous, Tertiary, and older 

 Pleistocene beds, so well shown at Gay Head, on Marthas Vineyard, is char- 

 acteristic of the beds in all the New England Islands, from Long Island to Nan- 

 tucket. The equivalent beds of the coastal plain in New Jersey and farther 

 south on the Atlantic border exhibit no such widespread distortion. Small dis- 

 placements and distortion of soft beds are seen at places along the "fall line," 



Fig. 3.— Sketch map showing approximately the area of glacial dislocation off the south coast of New England. 

 The heavy dotted line shows the southernmost limit of the Wisconsin ice front. 



at the contact of the beds of the coastal plain with the crystalline rocks of the 

 Piedmont plateau, as at Richmond, Virginia, where the Miocene is faulted down 

 against the granite. Folding is seen at some places in the coastal plain, as in the 

 eroded anticline traversed by the Tombigbee River, in Alabama, and dislocation 

 is found at Muscle Shoals, on the Tennessee River. None of these disturbances 

 of the beds on the coastal plain south of the terminal moraine on Staten Island, 

 however, have the breadth of exposure and the peculiar association with glacial 

 deposits that are seen in the New England Islands. 



