Late Cenozoic tephrochronology and glass fission-track dating

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Big volcanic eruptions shed widespread blankets of tephra (volcanic ash) on the landscape, sometimes more than 1000 km from the source. If a tephra beds is distinctive and its age known, it serves as a marker bed, noting wherever it is preserved, the age of that sedimentary horizon. Tephra beds, therefore, help to link in a temporal framework, the numerous, separate exposures of sediments, which bear the evidence, albeit fragmentary, of Earth's past conditions. This field of endeavour is known as "tephrochronology". Our tephrochronological studies are focused on the late Cenozoic (<3Ma) sediments of eastern Beringia (Alaska and Yukon), where tephra beds are abundant. Detailed studies have been done in the Fairbanks area, bluffs of the Yukon River in east-central Alaska, and the Klondike goldfields near Dawson City, Yukon. Current research concentrates on tephra-bearing sites in the Old Crow Basin and Thistle Creek in Yukon as well as at Chicken, The Palisades along the Yukon River, and Fort Yukon in Alaska. We anticipate the results will facilitate connection of Ice-Age records across eastern Beringia and improve the temporal calibration of climate/environmental change in this region during the last 3 million years. Efforts will also be made to determine the significance of compositional complexity and eruptive history of the late Holocene White River Ash beds and an attempt will be made to devise a classification scheme for all the tephra beds of eastern Beringia. Other projects include: (1) Miocene tephrochronology of southern Saskactchewan and Montana, where very thick tephra beds occur and are undoubtedly derived from volcanoes of the Yellowstone hotspot track. (2) Composition, source, and glass-ft age of Eocene tephra beds in a sedimentary core recovered from lacustrine sediments above a kimberlite pipe in NWT. (3) Glass-ft age of tephra beds in cores of lacustrine sediments that infill an old meteorite crater in Siberia - cores that represent the longest, most time-continuous record of late Cenozoic Arctic climate evolution. (5) Age of Homo floresiensis in Indonesia.