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Palynology of Tertiary rocks of the Whatcom Basin, Southwestern British Columbia and Northwestern Washington. Hopkins, William Stephen


Lower and Middle Tertiary continental sedimentary rocks comprise the fill in a large structural basin adjacent to the Georgia Depression in southwestern British Columbia and northwestern Washington. Upper Cretaceous continental sedimentary rocks apparently underlie the entire basin. Outcrops of Tertiary rocks are restricted to the north, south and east margins where they are dipping into the basin and overlying older rocks rimming the basin. Relationships to the west are obscured by the Strait of Georgia, but apparently the Whatcom basin is part of, and contiguous with, the Georgia depression. Over most of the area, surface cover is Pleistocene and Recent sediments. Investigations of plant microfossils from two deep basin wells indicate three distinct floras in pre-Pleistocene rocks. Basal portions contain a relatively small Upper Cretaceous floral assemblage. Above this are Middle and probably Upper Eocene assemblages. Upper parts of the section contain a predominantly dicotyledonous Miocene assemblage. Palynological study of the outcrops indicates a Middle to Upper Eocene age for all except the Brothers Creek outcrop on the north side of Burrard Inlet, which appears to be Upper Cretaceous. Miocene rocks are found only in the wells, and apparently do not crop out. Eocene assemblages contain Pistillipollenites and Platycarya together with significant numbers of Cactricosisporites and Anemia spores, and suggest a warm temperate to subtropical climate. Miocene assemblages are generally characterized by Glyptostrobus, Pterocarya, Ulmus-Zelkoya and Fagus and several other dicotyledonous pollen. Miocene assemblages indicate a more temperate aspect than those of the Eocene.

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