Middle Wisconsinan sediments and paleoecology of central British Columbia: sites at Necoslie and Nautley rivers

摘要

At two sites in central British Columbia, sediments with dispersed organic matter, underneath Fraser Glaciation deposits, are interpreted as nonglacial deposits of Middle Wisconsinan age (Olympia Nonglacial Interval). At Necoslie River, undated sand with dispersed organic matter, thought to be fluvial in origin, is overlain by Fraser drift. At Nautley River, similar sand contains plant detritus that has yielded C-14 ages of 38 230 +/- 410 BP (Beta-88557) and 42460 +/- 670 BP (Beta-88558). Pollen assemblages of the sediments with dispersed organic matter at the Necoslie River and Nautley River sites are similar: both assemblages are dominated by herb pollen, with a lesser amount of tree pollen. The pollen assemblages are thought to reflect a tundra-type vegetation. Because vegetation in the area is presently dominated by spruce and subalpine fir forest, climate during deposition probably was much cooler than today. Data presented here support the contention of other studies in western Canada that cooler climatic conditions existed for some time during the Middle Wisconsinan.