198 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



section (B. C. D on map), as the Devonian limestones were present 

 not only on the eastern and western sides of the trough, but also for 

 a long distance in Mounts Murchison and Sedgwick of the central 

 portion. 



During the field season of 1924 I had the opportunity of studying 

 the formations of the Beaverfoot-Brisco-Stanford Range and of 

 passing in rapid review the entire Kicking Horse River section. This 

 caused me to question my view of 1923 but it was not until the 

 summer of 1926 that I concluded that while the 1923 view might be 

 generally correct for the Glacier Lake-Saskatchewan section, it did 

 not correctly record the history of the deposition of the Bow-Kicking 

 Horse section. 



PRE-DEVONIAN UNCONFORMITY AND INTERVAL IN THE 

 CORDILLERAN PROVINCES 



Many sections in the Cordilleran Provinces clearly prove that there 

 was a great stratigraphic break at the base of the Devonian limestones 

 which are so strongly developed over the eastern section of the Rocky 

 Mountains and less so in the area east and west of the " Rocky 

 Mountain Trench." This unconformity in western Canada extends 

 from the F"orty-ninth Parallel on the south to Yellowhead Pass and 

 far beyond to the north. That the Devonian limestones were deposited 

 entirely across the Cordilleran Geosyncline by the transgressing De- 

 vonian sea on the line of the Bow-Kicking Horse Rivers is not prob- 

 able, but in my paper of 1923 (published in 1924),^ I assumed that 

 they were, being largely influenced by the Glacier Lake- Saskatchewan 

 River section (B, C, D on map, pi. 26), where the Devonian lime- 

 stones are present on the eastern and western sides of the geosyncline 

 and also in the central portion in Mounts Murchison and Sedgwick. 

 Near the shore line on the eastern and western sides of the geosyn- 

 cline, the deposition of pre-Devonian sediment was usually irregular 

 and thinner than in the central parts, and often the beds disappeared 

 entirely. This great unconformity I first recognized on the Rocky 

 Mountain front, west of and above Ghost River and named it the 

 Ghost River Interval. In most instances I have used this as the upper 

 limit of the study of the stratigraphic sections, the Clearwater River 

 Canyon, where the Devonian is included, being an exception. 



* Walcott, La Discordance de Stratification et la Lacune Stratigraphique 

 Pre-Devonienne dans les provinces Cordilleres d' Alberta et de Colombie Britan- 

 nique, Canada. Libre Jubilaire, Soc. Geo!, de Belgique, 1924, pp. 1 19-123, 

 pis. i-iii. Section on p. 121. 



