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The northern lobe of the White River Ash (WRAn) is part of a bilobate distribution of tephras that originated from the Wrangell Volcanic Field near the border of Alaska, USA, and Yukon, Canada. It is distributed across northeastern Alaska and the northwestern portion of the Yukon. The timing of this eruption has seen little critical analysis relative to the younger and more extensive eastern lobe eruption of the White River Ash. We compiled 38 radiocarbon (14C) dates from above and below the WRAn, and employed several statistical approaches to identify and eliminate or down-weight outliers, combine dates, and different Bayesian models, to provide a revised age estimate for the timing of the WRAn tephra deposition. Our results indicate that the most accurate modeled age estimate for the northern lobe of the White River Ash deposition is between 1689 and 1560 cal BP, with a mean and median of 1625 and 1623 cal BP, respectively. This age range is 90 to 200 years younger than previous age estimates.
A brief increase in wind intensity between ca. 11,100 and 10,700 yr B.P. is recorded by a sharp increase in sediment grain size at eolian sections along the Nenana River in central Alaska. This occurred at the same time as the Younger Dryas climatic reversal in northern Europe and an increase in the vigor of atmospheric circulation recorded by Greenland ice cores. Climatic fluctuations in high latitude areas during Younger Dryas time may reflect variations in the CO2 content of the atmosphere.
Between the Alaska Range to the south and the Brooks Range to the north, the Yukon River and its tributaries form an extensive network of waterways leading through the lowlands of interior Alaska deep into the North American continent (Fig 1). Despite the extremely cold winters of this arctic and subarctic landscape, much of the region remained unglaciated during the last 50,000 years. The central Alaskan lowlands are at the west end of the “ice-free corridor,” thought by most prehistorians to be the pathway to the Americas for Asian hunter-gatherers crossing the continental Beringian “landbridge.” Until recently, relatively little was known of the early human prehistory of Alaska's interior. Growing interest in the timing, nature and paleoecological context of the initial peopling of the Americas has prompted excavation at a number of early sites in central Alaska and the adjacent Yukon (see Powers & Hamilton 1978; West 1981; Fagan 1987: 119-134; Hamilton 1989; Powers & Hoffecker 1989).
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