325 



general northwest-southeast strike, and the prevailing 

 dip is to the northeast. At the northern rim of the basin 

 in the vicinity of Departure bay, the general strike turns 

 from northeast to east, while the dip is to the southeast 

 and south. The largest fold, with the exception of the 

 major fold which outlines the basin, occurs on Gabriola 

 island. It is a syncline, which is divided into two parts 

 by a transverse anticlinal roll at the northern end of the 

 island. 



A large portion of the region about Nanaimo is covered 

 by superficial deposits of various kinds, which are, however, 

 almost entirely referable to the Glacial period. This period 

 was characterized by two epochs of glacial occupation, 

 the Admiralty and the Vashon, separated by an inter- 

 glacial epoch, the Puyallup. Little or nothing remains of 

 the glacial till, which must have mantled a large part of 

 the area on the retreat of the earlier and larger Admiralty 

 glaciers. During the Puyallup inter-glacial epoch, a large 

 part of the lowland must have been covered by stratified 

 sands and clays, partly, if not entirely, of marine origin. 

 These inter-glacial deposits were largely eroded during 

 the Vashon glaciation, but now occur mantled by a 

 more or less persistant covering of Vashon drift, to the 

 northwest of Nanaimo and in the broad low area adjoining 

 the lower part of the Nanaimo river, to the south of 

 Nanaimo. On the retreat of the Vashon glaciers, large 

 delta deposits, composed chiefly of sand and gravel, were 

 built at the mouths of the large valleys, which extend 

 eastward from the Vancouver Island upland, and were at 

 that time presumably occupied by retreating valley glaciers. 

 The deposits have a maximum elevation of about 400 feet 

 (120 m.). The islands are not covered by these deposits 

 but merely by debris of the immediately underlying 

 rocks mixed with more or less glacial till and sometimes 

 overlying or closely associated with stratified sand and clay 

 of the inter-glacial deposits. It thus appears as if during 

 the deposition of the delta deposits the islands were still 

 covered by the piedmont Strait of Georgia glacier. It may 

 be that the deltas were deposited in lakes dammed by the 

 Strait of Georgia glacier, but, since it is positively known 

 by the occurrence of marine fossils in the vicinity (on 

 Texada island and near Vancouver) at elevations near 

 400 feet (120 m.) that a recent uplift of about 400 feet 

 35069— 4|b 



