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Lateglacial and Holocene paleoenvironmental changes recorded in lake sediments, Brock Plateau (Melville Hills), Northwest Territories, Canada

Paleoecological Environmental Assessment and Research Laboratory (P.E.A.R.L.), Department of Biology, Queen's University, Kingston Ontario K7L 3N6, Canada, ruhlandk{at}queensu.ca

Jeannine-Marie St. Jacques

Prairie Adaptation Research Collaborative (P.A.R.C.), 120-2 Research Drive, University of Regina, Regina Saskatchewan S4S 7H9, Canada

Brandon D. Beierle

Department of Geography, Queen's University, Kingston Ontario K7L 3N6, Canada

Scott F. Lamoureux

Department of Geography, Queen's University, Kingston Ontario K7L 3N6, Canada

Arthur S. Dyke

Geological Survey of Canada, 601 Booth Street, Ottawa Ontario K1A 0E8, Canada

John P. Smol

Paleoecological Environmental Assessment and Research Laboratory (P.E.A.R.L.), Department of Biology, Queen's University, Kingston Ontario K7L 3N6, Canada

Sediments from South Lake, Brock Plateau (Melville Hills), Northwest Territories, provide one of the longest postglacial records from the mainland western Canadian Arctic, outside of eastern Beringia. Sedimentation commenced at least 13 900 cal. yr BP, and possibly as early as 16 000 cal. yr BP, in response to early deglaciation of the site. Pollen is present throughout the record, with an initial Artemisia-Salix assemblage indicative of very cold conditions, consistent with a locally severe Younger Dryas Stade or simply continued proximity of the Laurentide Ice Sheet margin (c. 12 700 to 11 500 cal. yr BP). At c. 11 000 cal. yr BP, abiotic proxies signal a transition to warmer conditions, corroborated by a pollen assemblage dominated by Betula and Cyperaceae. Although South Lake was biologically productive during the early Holocene (c. 11 000 to 7000 cal. yr BP), diatoms and other siliceous organisms are notably absent from the record, suggesting severe silica limitation. Rises in Alnus crispa and Picea mariana pollen at c. 7000 cal. yr BP suggest cooling and/or an increase in effective moisture. Wetter conditions and increased hydrological inputs and silica supply likely led to the establishment of a pioneering diatom community at c. 6500 cal. yr BP. Decreased organic sedimentation after c. 2000 cal. yr BP suggests cooler conditions. Additionally, changing niveo-eolian deposition of sand on lake ice varied with a c. 3000-year periodicity through the entire record. The South Lake multiproxy record supports the hypothesis that the Brock Plateau was one of the earliest deglaciated regions during the late Wisconsinan.

Key Words: Brock Plateau • early deglaciation • Holocene • lake sediment • Melville Hills • multiproxy.

The Holocene, Vol. 19, No. 7, 1005-1016 (2009)
DOI: 10.1177/0959683609340999


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