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Lacustrine Environments |
1 Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309, USA
2 NOAA Paleoclimatology Program, NGDC, Boulder, Colorado 80303, USA
3 Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA
Tidewater lakes on Baffin Island in the eastern Canadian Arctic offer an excellent opportunity to study interannual to century-scale Arctic climatic change. Freeze-cores were analysed from three lakes in southeastern Baffin Island: Upper Soper Lake, Ogac Lake and Winton Bay Lake. The sediment record in each lake consists of massive sediments overlain by an organic-rich, finely laminated section which continues to the surface. The laminae in Ogac Lake were studied in detail and consist of two types. The light layers are composed almost entirely of intact diatom frustules, primarily Chaetoceros spp. The darker layers are dominated by clay and silt-sized terrigenous mineral grains, including abundant quartz and feldspars. These couplets are probably deposited as the result of diatom blooms in the late spring/summer growing season followed by settling of grains introduced by summer runoff. Sedimentation rates based on 210Pb dates agree well with rates based on laminae counts in both Ogac and Winton Bay Lakes, indicating that the laminae couplets are annually deposited varves. Our experience suggests that shallow-silled tidewater lakes with varved sediments may be relatively common along the coast of Baffin Island. It should thus be possible to create a network of sites with annually dated palaeoclimate records.
