[schofield] rocky MOUNTAIN TRENCH 79 



in proportion to its length. All of these features suggest that there 

 has been scission and shifting, causing the horizontal movement of 

 the Rocky Mountain system past the Purcell-Selkirk-Columbia- 

 Cassiar Mountain group or vice versa. An analogy is found in the 

 600-mile San Andreas rift of California which was the locus of the 

 earth-shaking horizontal shift of 1906."^ 



Daly's estimate of the throw of about 20,000 feet along the great 

 fault in the trench cannot be considered as in any way accurate since 

 it is based on the assumption that the Cougar quartzites are Beltian, 

 whereas if they overlie the Laurie formation as Daly states, they must 

 be at least post-Carboniferous. Thus the fault brings the Upper 

 Cambrian and the upper Palaeozoic in juxtaposition. Also the 

 provisional determination that the Cougar quartzites are upper 

 Palaeozoic in age and not Beltian makes the downthrow side on the 

 east instead of the west. 



4. At Surprise Rapids, 40 Miles North of Golden. — From Donald 

 north to the Big Bend we are indebted to Coleman^ for geological obser- 

 vations on this portion of the trench. His description is as follows: 

 "The rocks exposed at Surprise Mount are typical mica and horn- 

 blendic schists dipping about 40 degrees to the south- southwest and 

 with a strike of east-southeast and north-northwest (Mag.) . In this 

 they differ from the mica schists at the rapids, the latter dipping 

 50 degrees to 70 degrees toward the south-southeast. The rocks 

 are probably Archaean in age, although they stand several hundred 

 feet higher than the (supposed) Palaeozoic slates and quartzites of 

 Lookout Point, less than 10 miles away. There must be a great 

 fault separating the two." This was confirmed by McConnelP in 

 1892. 



From Surprise Rapids to Lake Timbaskis according to Coleman 

 the Columbia follows the boundary between the (Archaean ?) schists 

 and the Palaeozoic limestones and the course of the river corresponds 

 to the usual strike of the rocks. From Lake Timbaskis northeastward 

 across the divide between the Columbia and the Fraser Rivers to 

 Tête Jaune no critical geological observations have been recorded, 

 but McEvoy* states that the valley seems to coincide with the 

 dividing line between the Archaean and Cambrian rocks. 



' The California Earthquake of April 18, 1906, published by the Carnegie 

 Institute of Washington, 1908, vol. 1, p. 48. 



2 Coleman, A. P., Trans. Roy. Soc, Can., vol. VII, 1889, sec. 4, p. 100. 

 'McConnell, R. G., Geo!. Surv., Can., Sum. Rept., 1892, p. IIA. 

 ♦ McEvoy, J.. Geol. Surv., Can., vol. XI, 1900, p. 40D. 



