Late Quaternary vegetation and climate change at Moraine Bog, Tiedemann Glacier, Coast Mountains, British Columbia, Canada

Moraine Bog lies outside a middle Neoglacial moraine at Tiedemann Glacier in the southern Coast Mountains, British Columbia. Palynology, magnetic susceptibility, loss on ignition, and radiocarbon dating were used to analyse the sediment core, with the objective of reconstructing changes in vegetation and climate during the late Holocene. There is little evidence of vegetation change prior to ca. 2400 14C yr BP. A period of disturbance, reflecting cooler moister conditions, coincides with the most extensive Tiedemann advance between 2530 +/- 50 and 2280 +/- 50 14C yr BP. A period of warm dry conditions, at ca. 1900 +/- 1500 14C yr BP, is marked by an increase in Pseudotsuga pollen and an increase in Nuphar sclereids, suggesting a fall in water levels. This period coincides with a time of drought and increased fire frequency in the southernmost Coast Mountains. By ca. 1300 14C yr BP, the forest acquires a more coastal composition, with abundant Tsuga heterophylla and Abies. An increase in Tsuga mertensiana pollen suggests the onset of cool and wet conditions by ca. 500 14C yr BP, coincident with the Little Ice Age. Changes in the intensity of North Pacific atmospheric circulation patterns may provide a forcing mechanism for changes in temperature and precipitation in the region.