198 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



Archean land, and to enter sparingly into the composition of the generally- 

 calcareous sediments lying still farther eastward. Where these sediments 

 now appear, in the eastern part of the Laramide range they are chiefly 

 limestone, indicating marine deposition at a considerable distance from 

 any land.'* 



McEvoy has described the Bow River series as occurring in the moun- 

 tains just east of the Rocky Mountain Trench at the divide between the Canoe 

 and Fraser rivers, latitude 53° north.*" He maps the Shuswap (Archean) 

 aeries on the west of the great trench, showing a spatial relation between the 

 Cambrian-Belt rocks to the Archean which is similar to that which Dawson 

 had discerned farther south. On this ground and allowing for some overlap 

 to the westward, the rim of the geosyncline may be provisionally placed some 

 distance to the west of the Rocky Mountain Trench in latitude 53° north. 



According to Dawson a parallel relation exists between the Bow River 

 (Misinchinoa schists) and the Archean on the Parsnip river, which also flows 

 in the Rocky Mountain Trench. + Again, the zone of old shore-lines off which 

 these Camibrian-Belt sediments were deposited, may be placed, here at 55° 

 north latitude, to the westward of the trench. How far to the westward of the 

 Parsnip river it should be placed it is now impossible to state but probably 

 not more than fifty miles. 



McConnell found the Bow River-Castle Mountain rocks on the east side 

 of the Rocky Mountain Trench at the Finlay river 57° 30' north latitude. 

 He also discovered crystalline rocks, referred to the Archean on the west side 

 of the trench. The relatively small thickness of the Bow River (4,000 feet) 

 and its conglomeratic character point once more to proximity to the old shore- 

 line zone. The zone probably lay not many miles to the westward of the 

 trench.:}: Dawson and McConnell have followed the continuation of the Castle 

 Mountain series to the Kachika and Liard rivers at 60° north latitude. They 

 also describe a large area of Archean to the westward and it is* not improbable 

 *hat the rim of the geosyncline here lay west of the Kachika river.§ 



The enormous length and singular straightness of the Rocky Mountain 

 Trench suggests that it is a line of dislocation. Detailed study at the Forty- 

 ninth Parallel and at a few other points to the north corroborate this idea. 

 It is, therefore, probable that the occurrence of Archean and Bow River-Castle 

 Mountain rocks, respectively on the west and east sides of the trench, may 

 simply show that the uplift has been greater on the west side of the line of 

 dislocation and that erosion has removed the sedimentary veneer on that 

 uplifted side, while it has not been able to destroy the veneer on the eastern, 

 down-thrown side. This conclusion is undoubtedly just, and it is certain that 



*G. M. Dawson, Bull. Geol. Soc. America, Vol. 12, 1901, p. 84. 



** J. McEvoy, Ann. Report, Geol. Surv. Canada, Vol. 11, 1900, Part D. 



t Report of Progress, Geol. Sur. of Can., 1879-80, Part B, p. 108. 



JR. G. McConnell, Ann. Report Geol. Surv. Canada, Vol. 7, 1894, Pt. C. 



§R. G. McConnell, Ann. Report, Geol. Surv. Canada, Vol. 4, 1888-9, Pt. D, pp. 

 13-14; and G. M. Dawson, Ann. Report Geol. Surv. Canada, Vol. 3, 1887-8, Pt. B, pp. 

 81-4. 



