EOCENE MICROTHERMAL HIGHLAND PLANT COMMUNITIES FROM THE OKANAGAN HIGHLANDS (BRITISH COLUMBIA/WASHINGTON)

The Eocene Okanagan Highlands was an upland region of southern British Columbia and northern Washington State spanning ~1000 km north-south and a range of elevation. Early to Middle Eocene fossiliferous sediments in the Okanagan Highlands contain extensive and well preserved pollen, and plant and insect megafossils. These fossil biotas provide evidence of thermophilic-temperate associations, with occurrences of 'subtropical' or mesothermal biota (including diverse Taxodiaceae, and dicots such as Eucommia and Gordonia), mixed with microthermal or 'temperate' biota (e.g. Abies, other Pinaceae; Alnus, other Betulaceae). Initial palynological analyses had stressed the importance of Pinaceae in these Eocene forests, contrasted with the rare presence of palm pollen, leading to interpretation of a conifer-dominated landscape similar in some respects to the present day British Columbian and Washington landscape. In contrast to Early Eocene floras in the Puget Group of Washington State, and in the US western interior, which reflect mesothermal to perhaps megathermal forests, the Okanagan Highlands fossil biotas appear to reflect upper microthermal (MAT <13°C) equable environments supporting mixed conifer and deciduous broadleaved forest. New palynological analyses are presented based on recent sampling from several late Early Eocene to early Middle Eocence sites from the region, including Republic in Washington State, and the southern British Columbia sites of Princeton (One-Mile Creek), Hat Creek, McAbee, Falkland, Horsefly and Driftwood Canyon. The pollen analyses provide a regional record of early Eocene environments across a highlands landscape spanning over 700 km2 that is compared with existing plant and insect megafossil collections from these sites.