THE HOLOCENE DEVELOPMENT OF A DEBRIS SLOPE IN SUB-ARCTIC QUEBEC, CANADA

The development of a debris-covered slope in subarctic Quebec was reco nstructed in relation to vegetation dynamics, fire history and local p ermafrost evolution. The slope consisted of a low-elevation rockwall a nd a rockwall-derived debris veneer overlying a sandy till deposit rew orked by gelifluction. The sedimentological and stratigraphical data a long with radiocarbon dating and dendroecological data indicated that: (1) the period around 5050 BP corresponded to the initial establishme nt of the forest cover probably after paraglacial rockfall activity fo llowing deglaciation; (2) it was followed by a period of stability unt il c. 3200-3000 BP when gelifluction occurred; (3) the period between c. 3000 BP and 900 BP was one of relative stability; until (4) a serie s of fires after 900 BP initiated a period of destabilization by mass movements and surficial weathering processes; (5) local permafrost for med during the last few centuries, especially under the forest fringe where Sphagnum peat developed. Results from this study indicate a stro ng connection between fire, slope destabilization and the intensificat ion of geomorphological slope processes during the last millennium at the study site.