GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 4I 



the strikes are nearly east-west, with northerly dips ; and within the 

 western portion of the strip the strikes are northeast-southwest, 

 with dips to the northwest. The dips seem to radiate from a center 

 not far south of the middle of the southern boundary of the map or 

 apparently from the great Panther-Snowy mountain mass of the 

 Indian Lake sheet. A series of flattened elliptical curves drawn 

 from the center just mentioned would approximately parallel the 

 strikes as shown on the southern side of the Blue Mountain quad- 

 rangle. It would be interesting to know how the strikes and dips 

 run across the northern few miles of the Indian Lake quadrangle. 

 The significance of this symmetric arrangement of strikes and dips 

 is not precisely know^n, though the presence of the belt of Grenville 

 some distance out (along Cedar river) with strike practically 

 parallel to the curving strike of the igneous rock may imply some- 

 thing. This belt of Grenville on the east is known to continue from 

 the vicinity of Indian Lake village across the southeastern corner 

 of the Newcomb sheet and for at least several miles southward 

 on the Thirteenth Lake sheet. On the west this same Grenville belt 

 quite certainly continues southward for some miles through the 

 Cedar river valley in the northw^estern part of the Indian Lake 

 sheet. Thus the great Panther-Snowy mountain mass of igneous 

 rock is known to be completely bounded on the west, north and 

 northeast by this belt of Grenville strata whose strikes and dips 

 show it to lap upon the flanks of the great igneous mass. The 

 writer is inclined to believe that we have here a large scale radial 

 development of strikes and dips produced in the syenite as a kind of 

 flow structure when the magma was being intruded, and if we con- 

 sider the Grenville to have been more or less raised or domed over 

 the surface of the invading magma, this readily accounts for the 

 existing circumferential belt of Grenville whose dips show it to lap 

 upon the flanks of the syenite, the general cover of Grenville having 

 been removed from the dome by erosion. In other words, we here 

 appear to be dealing with som.ething of the nature of a laccolithic 

 intrusion. 



Folds 

 The general change from southerly dips in the northern portion 

 of the quadrangle to northerly dips in the southern portion may 

 possibly indicate a great synclinal fold in the foliation with axis 

 passing from the northern base of Blue Ridge through Dun Brook 

 mountain. This may, however, be interpreted simply as due to 

 differences in flowage of the great masses of intruding magma. 



