i6o 



now deposited in the Western Belt, which for the most 

 part had so long remained above sea. The exact sources 

 of supply for this fragmental detritus can not be fully 

 determined. It is possible that islands of the Shuswap 

 rocks still remained, and probable that parts of the Rocky 

 Mountain Geosynclinal were upwarped, so as to suffer 

 erosion during the Pennsylvanian. We know more de- 

 finitely that some of the sedimentary matter in these rocks 

 of the Western Belt was derived from the erosion of 

 contemporaneous volcanoes. Great eruptions of basalt 

 and basic andesite were widespread in the Western Belt 

 during this period. 



The Permian period has left no record of rock formation 

 in the Western Belt but seems to be represented by con- 

 tinued deposition in the Eastern Belt (Upper Banff shale, 

 1,400 feet; 427 m. thick). 



West of the Shuswap Lakes region the Pennsylvanian 

 strata were at least locally subjected to moderate defor- 

 mation, followed by erosion. These events anticipated 

 the deposition of the Triassic shales and limestones, among 

 which exceptionally heavy flows and pyroclastic masses 

 of basalt were erupted. This vulcanism was widespread 

 in the Western Belt, from Alaska to California. In 

 British Columbia it took the form of heavy fissure erup- 

 tions with subordinate central eruptions. Few lava 

 formations are as massive as the extensive and very thick 

 basalts of the Nicola group. It is not certain that Jurassic 

 sediments are represented anywhere in the railway section 

 of the Western Belt. Hence the history of the Jurassic 

 period is here obscure. From the analogy of other regions, 

 particularly California, it is concluded that this part of 

 the belt was strongly folded during the closing stage of the 

 Jurassic. 



In the Eastern Belt the Paleozoic era was closed by a 

 broad upwarping, by which the sea was largely withdrawn 

 from the Rocky Mountain geosyncline. It is probable 

 that at least the western half of this belt in our section 

 has been out of water ever since and that conditions of 

 erosion there prevailed in the early Mesozoic. The 

 upper Jurassic of the eastern foot-hills is conformable with 

 the Cretaceous of the Great Plains and, like the latter, 

 was probably in piedmont relation to the Cordillera 

 Eastern Belt The late Jurassic orogeny, so powerful 

 in the Western Belt, did not seriously deform the Paleozoic 



