Late Pleistocene - early Holocene plant macrofossils and pollen from the Yukon Flats, central Alaska

Dramatic climate changes and expansion of new biomes characterize the late Pleistocene - early Holocene of eastern Beringia. Analysis of plant macrofossils and pollen from three different sites in the Yukon Flats, central Alaska, record the past vegetation during the late Pleistocene - early Holocene (ca. 11,500--6,900 14C yrs BP) transition. The first paper deals with plant macrofossils associated with one of the earliest post glacial beaver dams (ca. 9,300 14C yrs BP) found in central Alaska. Vegetation reconstruction suggests a warmer than modern climate during the early Holocene. The second paper examines eight paleosols and their associated plant macrofossils and pollen within eolian deposits at two sites ranging from 11,500--6,900 14C yrs BP in the Yukon Flats. Spruce macrofossils were found in a paleosol dated at 10,700 14C yrs BP. High spruce pollen percentages (26%) were also recorded near the paleosol. This is the earliest post-LGM evidence for spruce in Alaska. Comparison with other post-glacial spruce records in Alaska, Yukon Territory and the Northwest Territories suggests a spruce refugium during the late Wisconsinan glaciation, perhaps in northwestern Canada.