100 THE ROYAL SOCIETY OF CANADA 



is only locally interrupted by unconformities" (12,d). Evidence that 

 there was an interval of erosion between the Precambrian and the 

 Palœozoic is given by Schofield. At Elko, British Columbia, he found 

 the lowest middle Cambrian Burton formation lying without angular 

 discordance on rocks which he assigns to the Precambrian (36, a), 

 (5, a). Further evidence of a break in sedimentation is given from 

 the North Kootenay pass by Adams and Dick (l,a); and Rose also 

 recognizes a disconformity at the base of the Palaeozoic. In the 

 summer of 1921 Schofield discovered a conglomerate at the base of 

 the Cambrian containing Olenelliis and resting on Beltian rocks (55). 



The Palaeozoic era in this region was a time of marine sedimen- 

 tation resulting in the accumulation of fossiliferous limestones, shales, 

 and sandstones. While sedimentation was general during this era 

 it was not continuous, and disconformities have been recognized even 

 in the comparatively few sections studied (36,b), (6, a), (32,a). Rocks 

 representative of the time from the lower Pennsylvanian to the lower 

 Jurassic are absent in the region, except possibly for a formation to 

 be described presently. This break in the record is interpreted as 

 meaning that near the close of the Palaeozoic era the Rocky Mountain 

 géosynclinal was broadly uplifted without appreciable deformation. 

 In the region under consideration the uplift was later than the lower 

 Pennsylvanian, as indicated by the fossils found in the Flathead 

 valley (26, a), and tentatively it may be assigned to the Permian. It 

 is at any rate of a later date than that assigned to it by Daly, whose 

 fossil record did not carry him beyond the upper Mississippian 

 (12,c). It is supposed that from the beginning of the Permian to 

 the lower Jurassic this region was land— a terrane of low relief, mainly 

 of limestones, but with some sandstones — ^undergoing subaerial 

 weathering with probably but little loss of the products of rock dis- 

 integration. The rock record for this stretch of time is here a blank, 

 with but one known exception as noted above, but is at least partly 

 represented in the region near Banff, Alberta (39,a). The exception 

 is a white sandstone formation, which, on inconclusive evidence, has 

 been assigned to the Triassic (26,b). This formation has been 

 interpreted as the result of the disintegration and reconcentration of 

 quartz sandstones, so it may be supposed that the sandstone interbeds 

 of the limestone terrane were exposed as ledges, disintegrated, and 

 their constituents accumulated and re-sorted both by wind and streams 

 and perhaps local lakes, for the sandstone possesses properties of both 

 aeolian and aqueous deposits. 



The third era of sedimentation, the Mesozoic, was initiated by 

 a subsidence previous to the lower Jurassic, and which may have taken 



