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CAPE COD GEOLOGY 



and by me in 1899 l have not been identified lithologically in the field, and 

 their lithological character is not shown on the geological map of the State. 

 The complex of rocks described above corresponds apparently with the sup- 

 posed Devonian igneous rocks of Emerson. 2 The hornblendic granitite is probably 

 the same as his Dedham granodiorite and Milford granite. The granite-gneiss 

 would thus become the correlative of the Northbridge granite-gneiss of Emerson, 

 which is referred to the Archean and lies below an Algonkian (?) quartzite. 

 The aplite becomes the associate of the Milford granite, and the fine-grained 

 dioritic rock, although it is subject to further examination under the microscope, 

 would appear to be the equivalent to the Ironstone quartz diorite of Emerson. 

 The area about New Bedford is shown on Emerson's map as an extension of 

 the Dedham granodiorite, whose various phases, which grade toward aplite on 

 one hand and diorite on the other, include local sheared strips of the rock form- 

 ing "gneiss." 



Many large boulders may be seen in the interior of Naushon. Koons 

 measured two erratics, each 27 feet long. A large, roundish boulder about 30 

 feet long, surrounded by small boulders, lies on the crest of the island, in the 

 middle one of three strong ridges, northeast of Tarpaulin Cove. 



Many boulders lie along the shore of Kettle Cove. A large boulder of 

 gneiss on the beach on the east side of Ram's Head, at the west point of the 

 Cove, bears on its western sloping surface glacial grooves running N. 20° W. by 

 the compass, or N. 33° W. by true bearing. This boulder may therefore bear 

 the marks of the ice that ran over it during the last stages of the ice on the 

 island. On Ram's Plead also there is a large boulder that has split along a 

 joint plane, so that its upper half has slid down to form a small rock shelter, 

 which is invaded by the sea at high tide. 



About half a mile west of French Watering Place and a third of a mile inland 

 from the shore there are two large boulders about 30 feet long, one of which 

 is broken into three blocks. 



A large boulder on the beach at the base of the 80-foot hill about a quarter 

 of a mile northeast of the east chop of Tarpaulin Cove stands out several yards 

 from the present bluff. It is inclined landward as if it had slid down the bluff 

 from the surface when the coast stood farther out. This boulder is rather too 

 large to have been thrown back by sea waves. 



Somewhat east of the central point of Nonamesset there is a boulder 24 feet 



1 U. S. Geological Survey, Monograph XXXIII. 



2 Emerson, B. K., Geology of Massachusetts and Rhode Island, U. S. Geol- Survey, Bull, 597, pp. 

 164-185, 1917. 



