REPORT OF THE CHIEF ASTRONOMER 353 



SESSIONAL PAPER No. 25a 



Sheet of the Canadian Geological Survey (1904). It reads as follows: — 

 1 These rocks consist of beds of andesites, tuffs and ash-rock, which overlie the 

 surrounding Rossland volcanics. Their age is not definitely known, they 

 appear to be comparatively recent. . . . The andesites of Record and Old 

 Glory mountains may be of the same age, though these have not been differen- 

 tiated from the Rossland volcanics on the map. The Beaver Mountain volcanic 

 rocks are occasionally mineralized to some extent.' Mr. Brock makes no men- 

 tion of associated sedimentary rocks. 



In 1902, the present writer, without the knowledge that Mr. Brock had tra- 

 versed these mountains, made an independent examination. Like Mr. Brock 

 he was struck with the relatively recent appearance of the lavas and pyroclastic 

 rocks about Beaver mountain and became convinced that they are considerably 

 younger than many of those composing the typical Rossland group. This 

 repeated recognition of a possible subdivision of the volcanic complex is believed 

 to be quite justified, and Mr. Brock's nomenclature is adopted in the present 

 report. To future workers in the district it may be proposed that the name 

 ' Beaver Mountain volcanic group ' be extended to all the lavas and pyroclastics 

 of the complex which are contemporaneous with those shown typically on and 

 in the vicinity of Beaver mountain. The area ascribed to the rocks of the 

 Rossland volcanic group, within the ten-mile belt, would thus in the future 

 be diminished as the various patches of the Beaver Mountain rocks are 

 separated. It will take several seasons of special work to bring about a satis- 

 factory delimitation of the younger and older members of the complex, even if 

 the dense forest cover and the almost infinitely involved structural difficulties 

 do not forever prevent this desired mapping. 



The Beaver Mountain group is shown on the map as covering about 

 twenty square miles in the northern part of the ten-mile belt. It is to be 

 understood that the boundaries are very roughly drawn, for it is often impos- 

 sible to tell when one passes from the younger rocks either to the latitic masses 

 or to the older porphyrites and other volcanics of greenstone-like facies. 



Sediments. — In this area two patches of water-laid elastics contemporaneous 

 with the volcanics, are mapped. A small outcrop of them also occurs on the 

 railway near the water-tank at Beaver. These strata may be called the Beaver 

 Mountain sediments. They consist of black to dark gray and brown thin- 

 bedded shales, and gray and greenish, thin-bedded to quite massive sandstones. 

 A massive conglomerate (granite, quartz, and slaty pebbles) crops out just 

 west of Champion station. The sandstones often graduate into typical, thick 

 masses of ash-beds and coarse agglomerates, alternating with vesicular flows 

 of basalt and augite andesite. The shales and sandstones bear fragments of 

 plant stems and leaves but no fossil of diagnostic value has been found. More 

 than 1,000 feet of the sediments are exposed in a section running from Cham- 

 X-don station eastward into Beaver mountain. There the dips are always to the 

 south and vary from 12-° to 32°, steepening as the mountain is ascended. 

 Toward the top of the stratified series heavy flows of porous andesite and much 

 25a — vol. ii — 23 



