October 30, 1890] 



NATURE 



651 



or had only occasional and brief connection with it, and in 

 which red beds with occasional layers of gypsum and salt were 

 being deposited.^ Rocks which represent a portion of the bed 

 of this inland sea enter into the composition of the Rocky 

 Mountain Range near the forty-ninth parallel, but are not 

 known to occur to the north of that parallel for a distance of 

 more than thirty or forty miles. To the west, they are not 

 found in the Selkirk or Purcell Mountains. We appear, in 

 fact, to discover in this vicinity the northern end of the inland 

 Iriassic sea. To the west of the Gold Ranges (under which 

 ierm it will be remembered that the Selkirk, Purcell, and other 

 mountains are grouped), deposits, also referable to the Triassic 

 period, and more particularly to its upper part, are again found. 

 These occur both on the mainland of what is now British 

 Columbia and on Vancouver Island and the Queen Charlotte 

 Islands. They contain truly marine fossils, and consist largely 

 of materials of volcanic origin, which give evidence of con- 

 temporaneous volcanic activity on a great scale. To the north, 

 in the Peace River country, and to the east of the present posi- 

 tion of the Rocky Mountains, rocks holding the same marine 

 fornts are found, and they have quite recently again been dis- 

 covered by Mr. McConnell in a similar position, still further 

 north, on the Tiard River. 



"It would thus appear that in Triassic times the eastern 

 border of the Pacific washed the western slopes of the Gold 

 Ranges, and that where this mountain-system became inter- 

 rupted, in its northern part, the sea was continued across its 

 line, and covered a large tract of country to the east of the present 

 position of the Cordillera belt. 



" Precisely how far to the east the shore of this northern ex- 

 pansion of the Pacific was situated has not yet been determined. 

 The region between it and the northern end of the inland sea 

 previously referred to must have been a land area, which separated 

 the open ocean of the north from the Mediterranean on the south. 

 The Rocky Mountains proper had not yet been formed, nor is 

 there any evidence of mountain ranges in the region of the Coast 

 and Vancouver systems of to-day, though the volcanic action 

 there in progress may have produced insular volcanic peaks. 

 The deposits of the inland Triassic sea, including as they do 

 beds of salt and gypsum, appear to prove the existence of a very 

 dry climate in the area occupied by it ; and as the land barrier 

 separating it from the moisture-bearing westerly winds of the 

 Pacific cannot have been wide, it must have been high. It is 

 thus probable that the mountains of the Gold system formed at 

 this time a lofty sierra, which was continued to the south of the 

 forty-ninth parallel by the Cabinet, Cour D'Alaine, Bitter Root, 

 and other mountains at least as far as the Wahsatch Range in 

 Utah. 



" The Triassic period was closed by one of those epochs of 

 folding and dislocation of strata which are found to be recurrent 

 in geological time, and which are generally attributed to the 

 secular contraction of the earth's crust. The evidence of this 

 time of change has been examined in greatest detail in the 

 vicinity of the present coast-line, where it resulted apparently 

 in outlining the Vancouver and Coast Ranges, and was accom- 

 panied by the production or extrav.isation of great masses of 

 granitic rocks.- It is highly probable that some corrugation 

 along the line of the Rocky Mountains occurred at the same 

 period, as, in the next succeeding Earlier Cretaceous strata, 

 without further evidence of disturbance, conglomerates are 

 found to be composed of fragments of many varieties of the 

 older rocks, which could scarcely otherwise have been rendered 

 subject to denudation. Though much remains to be discovered 

 respecting this post-Triassic epoch of disturbance, it was evi- 

 dently an important one, and its results were wide-spread in the 

 Cordillera region. It is quite possible that it was accompanied 

 by, or resulted in producing, a general elevatioo of this entire 

 region above the sea-level, as no rocks distinctly referable to the 

 Jurassic or next succeeding period have yet been distinctly re- 

 cognized either in British Columbia or in its bordering regions. ^ 

 It must be borne in mind, however, that a portion of the red 



' Cf. " Note on the Triassic of the Rocky Mountains and British Colura- 

 .■,," Transactions of the Royal Society of Canada, vol. i , Section iv., 



Cf. "Report of Progress, Geological Survey of Canada," 1878-79. pp. 

 }!, 48 B ; '• Report of Progress, Geological Survey of Canada," 1886, 

 15 B. 



Certain rocks, from which fossils supposed at the time to be Jurassic 



re described, have since been found to belong 10 the Earlier Cretaceous. 



:. " Report of Progress, Geological Survey of Canada," 1876-77, p. 150; 



' -Mesozoic Fossils," vol. i. p. 258. I 



NO. 1096, VOL. 42] 



beds of the inland sea, described as Triassic, may extend upward 

 into the Jurassic period, and that the marine Triassic fossils of 

 the western and northern sea are referable to the later stages of 

 the Triassic, or ' Alpine Trios ' of the Cordillera region, com- 

 parable with the St. Cassian and Hallstadt beds of the Alps in 

 Europe ; while the beds of the Cretaceous next found are, 

 according to European analogies, near the base of that forma- 

 tion." 



" The next distinct record of the physical conditions of the 

 region under discussion is afforded by the Earlier Cretaceous 

 rocks. These, on the evidence of contained molluscan fossils, 

 are regarded as about equivalent to the Gault of England, 

 though the associated remains of plants are such as to admit 

 their assignment to a somewhat older date. At this time, the 

 immediately post-Triassic elevation had been followed by a sub- 

 sidence of the land, resulting in the re-occupation by the open 

 sea of the great area which had been similarly characterized in 

 the Triassic. As in Triassic times, we find that this Earlier Cre- 

 taceous extension of the Pacific, to the north of the fifty-fourth 

 parallel, spread eastward in a more or less connected manner 

 completely across the present position of the Cordillera belt, 

 while the Gold Ranges, and probably also other insular areas, 

 continued to exist as dry land. In this case, as in that of the 

 Triassic, it has not yet been found possible to outline exactly 

 the eastern limit of the sea, in consequence of the want of 

 sections cutting down to the base of the Cretaceous in the area 

 of the Great Plains. There are, however, reasons for believing 

 that it did not extend far beyond the line of the present foot- 

 hills of the Rocky Mountains. 



" In one important particular, the conditions in this Earliei 

 Cretaceous period differed from those of the Triassic. There 

 was at this time no isolated inland sea, and waters in connection 

 with the main ocean stretched southward to the east of the Gold 

 Pvanges as far as the forty-ninth parallel and beyond it to a 

 further distance which is as yet undetermined. This extension 

 of the open sea thus actually overlapped, to a considerable 

 extent, the area formerly occupied by the Triassic medi- 

 terranean." 



This was followed, however, in Middle and Later Cretaceous 

 times, by a great depression in which the marine beds of the 

 Neobrava and Pierre Groups were deposited. This submergence 

 was succeeded by some measure of elevation or folding, leading 

 to the existence of vast swampy and lacustrine flats, in which the 

 lacustrine and peat deposits of the Laramie formation of the 

 great plains were formed. These deposits may be regarded as 

 closing the Cretaceous era, or as transitional between it and the 

 Eocene. 



" This state of affairs was brought to a close by another of 

 the recurrent epochs of folding and dislocation of the earth's 

 crust, which was one of the greatest of those of which we find 

 the results in the region under discussion, as well as the last of 

 an important character to which this region was subjected. 

 Under the influence of enormous pressure acting from the 

 Pacific side, the nearly horizontal strata, which bordered the 

 Gold Ranges on the north-east, were folded together and thrown 

 up into a dominant ridge of Alps, which finally outlined the 

 Cordilleran belt on this side. A similar folding and upthrust 

 affected also the western marginal mountains which have been 

 referred to as the Vancouver Range, but the action was there 

 probably less violent and certainly affected a narrower zone. A 

 portion of the crumpling to which the rocks of the Coast Ranges 

 have been subjected was doubtless also produced at or about the 

 same time, and certain granitic extrusions which cut the earlier 

 Cretaceous rocks on its eastern flanks, as well as much of the 

 flexure of these Cretaceous rocks, are also attributed to this 

 period of disturbance. 



"There is really no means of ascertaining what effect this 

 disturbance produced in the region of the Gold Ranges, but it is 

 more than probable that the whole width of the Cordillera then 

 suffered changes and deformation of such a character that little 

 if any trace of its surface contour of an older date can be found 

 to-day.^ It does not, however, necessarily follow that the 



' In respect to this great epoch of oragraphic movement, as evidenced 

 particularly in the more southern part of the Cordillera, which has now 

 been somewhat clasely studied, Mr. S. F. Emmons may be quoted as 

 follows: — "It is unquestionably one of the most important events in the 

 orographic history of the entire Cordilleran system. With the exception of 

 the great unconformity between the Archsean and all overlying sediments, 

 which is a phenomenon sui generis and altogether exceptional, no mavement 

 has left such definite evidence as that which follows the deposition of the 

 coal-bearing rocks to which the name Laramie has by universal consent 

 been applied." — Bulletin Geol. Sac. Anter., vol. i. p. 285. 



