EARLY POSTGLACIAL SEDIMENTATION OF LOWER SEYMOUR-VALLEY, SOUTHWESTERNBRITISH-COLUMBIA

In lower Seymour Valley, much of the sediment derived from the erosion of valley-side drift (paraglacial sediments) remains in storage in th e form of alluvial fans and aprons. Fluvial incision into these featur es has exposed sections for lithostratigraphic and chronological study . Radiocarbon dating of organic-rich beds within these deposits indica te that paraglacial sedimentation of lower Seymour Valley commenced be fore 11.4 ka, was periodic, and was essentially complete by about 9 ka ; Seymour River had incised to its present vertical position by about 5 ka. Furthermore, our radiocarbon ages indicate that, although paragl acial sedimentation commenced shortly following deglaciation when the climate was cool and moist, a significant amount of sedimentation occu rred during a transition from wet and moist climate to warm and dry (x erothermic) conditions (ca. 10 ka). Charcoal-rich beds indicate that s ome erosional events may have been a result of slope instability cause d by fire.