OVERTHEUST PHENOMENA. 



27 



faults, there is no tendency of faulted blocks to ride over one another. It 

 can readily be understood that, inasmuch as this region has been subjected 

 to very extensive erosion, overthrusting which was preceded by the collapse 

 of the folds might have all the marks of its former existence destroyed by 

 the removal of the strata which were involved in the movement, 



An ideal section (fig. 2) drawn by Mr. Woodworth through the three 

 great synclines in which the Dighton group appears, including the Attleboro 

 syncline on the north, the Great Meadow Hill trough in the middle of the 

 basin, and the Swansea syncline on the south, exhibits a symmetry in the 

 cross section which is further evidence of the simplicity of the larger 

 features of structure of the central part of the basin. There is along this 

 line of section a great broad syncline in the middle of the basin. It has 

 nearly symmetrical slopes with relatively low dips The synclines parallel 



4tf/e6oro 

 sy/7c//he 



Gt. Meadow ///// 

 sy/?c/// 



Swansea 

 sync//ne 



etical plan of the 



with it on the north and south have their axial planes inclined away from 

 the middle syncline, or, in other words, the sides of the synclines facing 

 the middle area are nearly vertical. A plane lying in this region of 

 folding would have been deformed so as to give a cross section like 

 that in fig. 2. There is in this case no prevailing pitch of the axial 

 planes to or away from the ocean or an older land mass, but rather a 

 symmetrical deformation of beds with reference to the middle line and sides 

 of the basin as it now exists. 



DIKE ROCKS OF THE BASIN. 



Although, as before stated, the systematic study of the igneous rocks 

 of this area lias not been undertaken, there are certain features connected 

 with their distribution which deserve notice. These concern the areas in 

 which the intrusions occur and the portions of the great section which they 

 traverse. 



