308 



CAPE COD GEOLOGY 



age and to have been formed by erosion and somewhat modified later by the 

 action of ice. Deposition of morainal drift, however, is more evident than glacial 

 scouring, though here and there the effects of the action of running water may be 

 seen in winding creases that lead away from old ice fronts marked by morainal 

 ridges. 



The chain of islands has a strong morainal cast and conforms in trend with 

 the lobate margin of a protrusion of the ice sheet in the Buzzards Bay depression 

 and in the main owes its origin to the crowding up of the underlying coastal plain 

 deposits and older Pleistocene gravel, sand, and clay, yet the stage of Pleistocene 

 glaciation at which the deformation was accomplished is not clearly indicated. 

 Here, probably, as on Marthas Vineyard, several successive ice thrusts were 

 effective in the shaping of the islands. 



A small exposure of Cretaceous and Tertiary beds lies at the east end of 

 the group. These beds are tilted and show a strong deformation. Such beds 

 have not been recognized as the southwest end of the group, where a well boring 

 goes over 200 feet below sea level. 



The absence of outwash plains of gravel and sand on the south side of the 

 islands is evidently not to be explained by supposing their erosion and removal 

 by the sea. It may mean that the stream flow was not sufficiently strong to carry 

 sand and gravel to a great distance from the ice front. Soundings in Vineyard 

 Sound and in the adjacent waters between Gay Head and Block Island do not 

 show the presence of such deposits. 



NAUSHON 



Salient Features 



Naushon, the largest island of the Elizabeth group, is 8| miles long and 

 between 1 mile and li miles wide. It extends southwestward and is separated 

 from Pasque Island, on the southwest, by Robinsons Hole, a narrow tidal pas- 

 sage having a minimum depth of 13 feet at mean low tide, and from several 

 small islets — Uncatena, Nonamesset, Rams Head Island, East Buck Island, 

 Monohansett Island, and three islets unnamed on the Coast Survey chart — by 

 shallow tidal ways due to depressions in the moraine. Woods Hole, a tidal 

 passage navigable for small steamers, separates Naushon and its dependent isles 

 from the heel of Cape Cod at the port of Woods Hole. 



The topography of Naushon and the adjacent islands is morainal. The higher 

 hills in the interior of the Naushon rise to elevations ranging from 100 to 168 



