1 32 GEOLOGY OF THE NARRAGANSETT BASIN. 



It is to be noted that the faults along this border are of the normal 

 Basin Range type, the downthrow being in blocks on the east and west 

 of a relatively uplifted block in Easton. The northward recession of the 

 boundary east and west of this block is in accordance with this structure. 

 The system of faults is, moreover, transverse to the Wrentham-Hingham 

 uplift of igneous rocks. So far, however, these fractures have not been 

 traced into the Norfolk County Basin. The throw of these faults is not 

 necessarily great. The dip of the strata near Brockton and Abington is 

 generally low, not exceeding 15°, and the surface is level, so that a ver- 

 tical downthrow of 1,420 feet would account for the displacement of the 

 boundary 1 mile on a horizontal plane at the latter place. 



The date of the faults is not in most instances determinable. They 

 are clearly post-Carboniferous, but their correlation with the dislocations 

 which deformed the Newark basins along the Atlantic coast in middle 

 Mesozoic times has not been proved. 



