Late Holocene permafrost dynamics in two subarctic peatlands of the Hudson Bay Lowlands (Manitoba, Canada).

摘要

Gross stratigraphical, palaeobotanical, and radiometric analyses of four peat sequences from the Hudson Bay Lowlands (NE Manitoba, Canada) provide evidence for Late Holocene permafrost dynamics. Two peat sequences are from a palsa complex, one froma palsa bog, and the other from an adjacent permafrost-free fen. The other two peat sequences are from a peat plateau area, one from the plateau itself, and one from an adjacent permafrost-free fen along the margin of a small lake. Radiocarbon dates andgross stratigraphical observations suggest that permafrost aggradation both at the palsa site and at the peat plateau site took place 2200 years ago. Palaeobotanical analyses of the adjacent fen sites indicate permafrost-free conditions throughout. Theseresults suggest that in the past 2200 years permafrost distribution at the study sites has remained constant with no evidence for temporary permafrost aggradation and subsequent collapse in the presently permafrost-free fen sites.