EVOLUTION OF TERTIARY MARINE SEDIMENTARY BASINS IN BRITISH COLUMBIA.

Tertiary marine sediments of terrigenous origin are present on the west coast of Canada. For the Upper Eocene to Pliocene time interval the sediments have a volume which amounts to 10 percent or less of that which might be expected from the erosional history of the land mass. An attempt is made to explain this apparent deficiency. Subduction can explain why only a small part of Upper Eocene and younger sediments are preserved south of Vancouver Island; it also may be the reason why the older part of the sequence is missing to the north of the island. However, most of the younger beds were probably preserved, but are largely absent in the area today because they were moved toward the north by spreading oceanic crust on the west side of an ancestral Fairweather - Queen Charlotte fault system.