320 



the flank of Mt. Benson. It appears as if the eastern 

 part of the Nanaimo basin had been depressed below sea 

 level, and the valleys drowned to form the long, wide 

 channels, passes, and harbours of the region. The hard 

 rock ridges remain above sea level as long points and islands. 

 During the Glacial period the region was glaciated, and the 

 rock surfaces were smoothed, and the valleys deepened. 

 Upon the retreat of the glaciers the region apparently 

 stood a few hundred feet lower than at present, for up to 

 an elevation of 400 feet (120 m) occur stratified sands and 

 gravels, in part of marine or estuarine origin. A recent 

 uplift has brought the land into its present position, and 

 initiated the present erosion cycle, during which the 

 revived streams have terraced the superficial deposits, 

 and have cut narrow canyons in the indurated rocks, 

 while the superficial deposits fronting on the coast have 

 been retrograded to form cliffs up to 100 feet (30 m.) in 

 height. 



General geology. 



The crystalline rocks, upon which the coal bearing 

 sediments of the Nanaimo series rest unconformably, are 

 the Vancouver meta-andesites. The volcanic rocks were 

 greatly deformed, metamorphosed and intruded by granitic 

 rocks, probably in late Jurassic time. The granitic rocks 

 were subsequently exposed, since boulders and pebbles 

 of them occur in the sediments of the Nanaimo series. 

 However, the crystalline rocks were apparently not worn 

 down to a lowland, because the surface upon which the 

 sedimentary rocks were deposited is seen to be one of 

 considerable relief. Small irregularities are directly ob- 

 servable in exposed unconformities, and the contacts of the 

 Nanaimo series with the underlying rocks, where not dis- 

 turbed by intense folding and faulting, follow very closely 

 the contours of present elevations, which must have been 

 elevations at the time of deposition also, unless far more 

 irregular and complex folding than is elsewhere observed is 

 supposed. 



The Nanaimo series, as shown by its fauna, is partly 

 of marine origin, probably estuarine, since it was deposited 



