The palynology and palaeoclimatic significance of a dated core of Holocene peat, Okanagan Valley, southern British Columbia

Abstract

Holocene vegetation and climatic changes of the Okanagan Valley, British Columbia, are inferred from fossil pollen assemblages recovered from Kelowna Bog in the central part of the valley. Broad climatic changes inferred from relict postglacial landforms in the valley are correlated with the above changes.The Okanagan Valley was ice-free and Glacial Lake Penticton drained before 8900 yr BP. A forest consisting mainly of pine (Pinus) and stands of spruce (Picea) had colonized the valley sides prior to draining of the lake. Soon after 8400 yr BP, moist conditions gave way to aridity during which grass (Gramineae) and sagebrush (Artemisia) predominated. This warm, dry interval is correlated with the Hypsithermal. Bare areas in the valley bottom were exposed to wind erosion; sand dunes formed in some areas, whereas in others, a veneer of aeolian sediment was laid down. At approximately 6600 yr BP, the climate became cooler and moister, aeolian activity diminished, and the dunes became stabilized by vegetation. During the ensuing latest climatic interval, three moister phases affected Kelowna Bog and were characterized by large increases in birch (Betula), alder (Alnus), and hazel (Corylus). These phases, which were related to increased runoff from the adjacent uplands, are tentatively correlated with the stades of the Neoglaciation recognized in southcentral British Columbia and neighbouring United States.