Dépôts et phénomènes éoliens sur l'île de Banks, territoires du Nord-ouest, Canada.

At the present time, eolian processes are active in many localities on Banks Island. Sediments of alluvial and outwash plains, as well as previously stabilized areas of eolian sands and areas where sandy Mesozoic and Tertiary deposits crop out, are subject to deflation. Locally ventifacts have been faceted. The vegetation cover of surfaces subject to eolian activity is described, as well as the main species oberved on these surfaces. The eolian deposits of lower Thomsen River are described in detail. The study of a section has shown that ice-wedge polygons developed during periods of sand accumulation. The formation of segregation ice at the top of the permafrost, when it is raised because of the accumulation of eolian sands on the surface, is outlined. Two radiocarbon age determinations from different sites along Thomsen River show that the deposition of eolian sands began 3790 plus or minus 90 years BP (GSC-2119) and 3460 plus or minus 80 years BP (GSC 2124). Ages of 5800 plus or minus 180 years BP (GSC-2242) and 8430 plus or minus 120 years BP (GSC-2419) were obtained, respectively, for the start of eolian sedimentation along Bernard River and on the outwash surface situated southeast of Sachs Harbour. The hypothesis that the initiation of eolian activity around 4000 years ago may have been the result of a drier and cooler climate on banks Island is put forward.