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The batholithic rocks are chiefly granodiorite with marginal 

 facies of diorite, but in the southeastern part of the island 

 there is a large batholith of gabbro-diorite and quartz- 

 diorite gneisses. All of the batholithic rocks are closely 

 related and appear to have been irrupted during the same 

 general period of intrusion. Nevertheless they may be 

 subdivided into four types that were irrupted in a definite 

 sequence, apparently as follows: — Wark gabbro-diorite 

 gneiss, Colquitz quartz-diorite gneiss, Beale diorite, and 

 Saanich granodiorite. It is probable that all the 'minor 

 intrusives' also, salic and femic porphyrites, were irrupted 

 during the same general period. 



Unconformable upon an erosion surface of the metamor- 

 phic and granitic rocks, and confined for the greater part 

 to the east coast of the island, is a thick conformable 

 series of fragmental sediments, the Nanaimo series, largely 

 of upper Cretaceous age. It consists of conglomerates, 

 sandstones, and shales, with some coal. In general, it 

 has been deformed, into broad open folds with a northwest- 

 southeast strike, and a general northeast dip, but in places 

 it has been closely folded, overturned to the southwest 

 and broken by reversed and overthrust faults. 



The deformation of the Nanaimo series probably occurred 

 in post-Eocene times. Previous to it, during upper-Eocene 

 times, a thick formation of volcanic rocks, the Metchosin 

 volcanics which are chiefly basalts, was accumulated in 

 the southern part of the island. These volcanics were 

 involved in the post-Eocene deformation, and at the same 

 time were intruded by stocks of gabbro, the Sooke 

 gabbro, which ranges from a femic to a salic gabbro and 

 even to true anorthosite. 



In later Tertiary time during the erosion cycle initiated 

 by the post-Eocene deformation, the Vancouver range was 

 reduced to a subdued surface, which in its southern part 

 was a peneplain with a few monadnocks remaining a few 

 hundred feet above the general level. In its central part, 

 however, the surface was one of considerable relief, with 

 larger and higher monadnocks and small ranges of mountains. 

 During this cycle a large part of the detritus was deposited 

 off the southern and western coasts of the island against a 

 submerged mountainous slope, and formed a coastal plain, 

 composed largely of coarse conglomerates and sandstones, 

 the Sooke and Carmanah formations. The subdued and 

 peneplained Tertiary erosion surface and the coastal plain 



