[schofield] rocky MOUNTAIN TRENCH 77 



The geology of the trench in the vicinity of Golden is described 

 by Daly.i 



"Eastward from Beavermouth for a distance of about 2 miles, the 

 railway runs over the Cougar quartzites, which are suddenly replaced 

 in the rock-cuttings by shales with subordinate interbeds of limestone 

 (structure section in map-pocket.) These have entirely different 

 habits from any of the formations so far described, recalling the 

 Ordovician Goodsir beds of the Rocky Mountains across the valley. 

 The shales, often calcareous, vary in colour from grey to black. They 

 are friable, heavily jointed, and locally well cleaved across the bedding 

 planes. The limestones weather to a buff-grey and seem to be gener- 

 ally magnesian. 



"Beds of the same general character crop out along the line for 

 " the next 6 miles, to the eastern end of the local canyon of the Columbia. 

 Throughout this section, strike and dip change very rapidly, indicating 

 structural turmoil. So great is the disorder that no measurements of 

 the true thickness represented is possible nor w as the attempt > to 

 work out the exact sequence of strata any more successful. Between 

 Donald and Golden, a distance of 16 miles, bed-rock is exposed at 

 only two localities on the railway. At the crossing of Blaeberry River 

 the outcrop is large, showing shales of the Goodsir type. No other 

 notable outcrops were seen, during this reconnaissance, in the tîoor 

 of the Rocky Mountain trench between Donald and Golden, but it 

 is likely that most or all of it is underlain by the shale-limestone 

 series actually seen along the railway. Without borings it will remain 

 impossible to map in detail the bed-rocks underlying the trench, for 

 they are covered by a remarkably thick and continuous mantle of 

 glacial debris and terrace gravels. 



"Fossils were found in the cuttings at and immediately east of the 

 tunnel at the 54.6 mile-post, nearly 3 miles west of Donald. They 

 occur in the cores of small calcareous nodules which have been abund- 

 antly segregated in grey shale. On breaking the nodules open longi- 

 tudinally, fragments of trilobites were found in fair abundance. This 

 material was sent to Dr. C. D. Walcott who kindly examined it and 

 reported as follows: 'The fossils indicate the upper portion of the 

 Upper Cambrian and possibly would be placed in the base of the 

 "Ozarkian" by Ulrich. Two genera are clearly defined. The larger 

 species belong to a genus closely allied to Dicellocephalus and there is 

 one specimen of Illeniirus. There is also another form not yet clearly 

 identified.' At least 1,000 feet of beds are represented at this fossil- 

 bearing locality. 



' Daly, R. A., Gcol. Surv., Can., Mem. 68, p. 83. 



