GEOLOGY OF LAKE PLEASANT QUADRANGLE 



47 



ridge just to the west, the shales showing a distinct updrag effect 

 close to the fault. See figures i, 2 and 3 and plate 9. 



[rr_r;d Ordovicic strata 



fig 3 

 Cambric strata 



gyjJGran.t.c syenite [gJI ^y-'^^ 

 1 ?"Horizon1'al scale 



MH 



' 1^ A 



Mixed gneisses 



Precambric rock 



Fig. 2 Structure section (along line AA) passsing through Hamilton 

 Mountain, Mt Orrey and Wells. 



Fig. 3 Structure section (along line BB) passing through Mt Rouge, 

 Wells and to Murphy lake on the Stony Creek sheet. 



Within the map limits the greatest throw (vertical displacement) 

 is alongside the Wells outlier and where the structure section lines 

 cross it (see map). The altitude of the fault line there is 1200 feet, 

 while summit of Mount Orrey lies at 2646 feet. This gives a dif- 

 ference of elevation of 1446 feet, but to this must be added 500 

 feet which represents the approximate thickness of the Paleozoic 

 strata just east of the fault. This gives 1946 feet which is the total 

 amount of displacement now represented in the topography. In 

 order to get the actual amount of displacement, the thickness of 

 material removed from the summit of Mount Orrey, since the 

 faulting began, must be added. We have no good reason to think 

 that this figure would be very materially increased on this account. 

 Thus, all things considered, the actual amount of displacement along 

 the fault here is no less than 2000 feet. This throw diminishes 

 rapidly both northward and southward. Thus, at the base of Elbow 

 mountain it is probably not much over 1000 feet, while between 

 Mount Dunham and West hill it can not be much over 1500 feet. 



