LOWEE CRETACEOUS. 625 



ceous rocks are found, and in tliis part of the mountains we appear to enter upon the edge of the 

 area of deposit of the Lower Cretaceous, the beds here named the Kootanie series occupying 

 that horizon. The geological horizon of the Kootanie series is determined by its position 

 relatively to the higher members of the Cretaceous series, and by the fossil plants which it has 

 yielded. * * * 'pj^^g plants ' ' consist of ferns, cycads, and conifers, some of them identical 

 with or closely related to those of the Jurassic of the Amur country in Siberia, and others 

 similarly related to the Lower Cretaceous of Greenland, as these floras have been described 

 by Heer. This group undoubtedly represents the flora of the Lowest Cretaceous, which has 

 not hitherto been recognized in western America."- * * * That the series characterized by 

 these plants is a widespread and important one is shown by the fact that one of the species 

 {Pinus suskwaensis) had previously been found on Suskwa River, in northern British Columbia, 

 at a distance of 580 miles northwest of the most northern locality here referred to. 



No complete section can yet be given of the Cretaceous rocks of the mountain region, nor 

 of those of the adjacent foothills. * * * Two horizons appear, however, to be fixed with 

 considerable definiteness in the lower part of the Cretaceous of the mountains — that of the 

 most important and persistent coal seams and that of the volcanic intercalation. The first of 

 these is fixed in part by the similarity of appearance and character of the coal and beds near 

 them, but chiefly by the very similar group of fossil plants which is found in association with 

 these coal seams. 



The thickness of the rocks of the Kootanie series below this coal-bearing horizon was esti- 

 mated on the Crow Nest Pass and near the west summit of the North Kootanie Pass at about 

 7,000 feet, which may be taken as a minimum estimate of the greatest observed development 

 of this part of the series. The beds are chiefly shales and sandstones of very varied texture and 

 appearance. 



The volcanic ash beds and agglomerates of the Cretaceous, in this region, are evidently due 

 to local eruption, which had its center in the latitude of the Crow Nest Pass. These volcanic 

 rocks have, however, been traced north and south from this point over a total length of 45 

 miles, and may probably have at one time had as great an extension east and west, though this 

 has subsequently been diminished by the folding together of the beds. The volume of the strata 

 between the coal-bearing horizon and the base of the volcanic rocks on the Crow Nest Pass was 

 estimated approximately at 3,350 feet, on the South Kootanie Pass at 2,400. The mean of 

 these approximations, 2,750 feet, may for the present be adopted as a probable result. The 

 volcanic rocks themselves, on the Crow Nest Pass, where they attain their maximum, have a 

 volume of about 2,200 feet, but thin out very rapidly to the north and south. 



The summit of the Kootanie series is not yet precisely defined but is situated between the 

 apparently constant coal-bearing horizon and the base of the volcanic beds, as, on the Northwest 

 Branch of the North Fork, fossil plants believed to represent the horizon of the Dakota are 

 found a few hundred feet below these volcanic beds. 



(See also M 11, Chapter XIII, p. 574.) 



M 10, N 9-10, O 9. WESTERN BRITISH COLinytBIA. 



The Jackass Mountain group, so called by Selwyn from the locality of that 

 name on Fraser River (near the mouth of the Thompson?), is described in his 

 report ^^* as consisting of "hard, close-grained, and thick-bedded greenish sand- 

 stones or quartzites, green and black shales, and, above these, massive, thick-bedded 

 pebble conglomerates, dipping generally at low angles in various directions; some 

 of the inclosed pebbles are of rocks belonging to the Cache Creek series." 



In 1875 Dawson ^"* identified these rocks on Tatlayoco Lake (longitude 124° 

 30', latitude 51° 30'), where they have the character of the strata on Jackass Moun- 



48011°— 12 40 



