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LATE QUATERNARY VEGETATION HISTORY AND CLIMATE RECONSTRUCTION INFERRED FROM WESTERN ALASKA AND NORTHERN YUKON LAKES

KUREK, JOSHUA  Department of Biology, University of New Brunswick.
Cwynar, Les C.  Department of Biology, University of New Brunswick.

Late Quaternary Beringian ecological communities are unique, representing the totality of biotic response to large-scale fluctuations of environmental factors. In this study, three lake sediment records (Zagoskin Lake [western Alaska], Hanging Lake and Trout Lake [both northern Yukon]) believed to span approximately the last 30, 000(?) 14C yrs B.P. will be examined to elucidate fluctuations in regional climate and the response of the sub-arctic flora. The paleoclimatic reconstruction will consist of inferred mean July air temperatures from subfossil midge (Chironomidae, Chaoboridae, and Ceratopogonidae) assemblages (Walker et al., 2003). Sub-arctic vegetation change will be examined using detailed pollen, stomate, and aquatic plant macrofossil analyses. The pollen stratigraphy of a 15.2 m sediment core from Zagoskin Lake has been divided into five distinct zones with a basal age of >30, 000 14C yrs B.P. (Ager, 2003). Preliminary analyses of 26 midge assemblages (0 4.35 m of sediment) from Zagoskin Lake suggests a dynamic midge response to Late Quaternary climate change with notable differences in midge stratigraphy throughout the last ~12, 000 14C yrs B.P.. Late Holocene samples are dominated by the Tribe Pentaneurini, Stictochironomus, and Paracladius, suggesting a cool arctic-tundra environment. Early Holocene assemblages are mainly comprised of Mesocrictopus thienemanni, Chironomus, and Subtribe Tanytarsina. Midge diversity is highest during the early Holocene (3 4 m of sediment) with a greater abundance and diversity of Chironominae compared to Orthocladiinae.

REFERENCES
Ager, T.A. , 2003, Late Quaternary vegetation and climate history of the central Bering land bridge from St. Michael Island, western Alaska: Quaternary Research, v. 60, p. 19-32.



Walker, I.R., Levesque, A.J., Pienitz, R., & Smol, J.P., 2003, Freshwater midges of the Yukon and adjacent Northwest Territories: a new tool for reconstructing Beringian paleoenvironments?: Journal of the North American Benthological Society, v. 22, p. 323-337.


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