COARSE CLIFF-TOP AEOLIAN SEDIMENTATION IN NORTHERN GASPESIE, QUEBEC (CANADA)

This paper deals with the effects of wind on rockwall dynamics. On 5 and 6 January, 1988 very strong northwest winds (blizzard) were blowing onto the rockwall of Mount Saint-Pierre (alt.: 424 m), Gaspesie, Quebec (Canada). The most violent recorded squall reached 99.4 km h-1. During this event, the summit plateau received a large amount of aeolian sediments originating from the shale rockwall that forms the mountain's northwest side. In the 15 to 20 m wide by 75 m long belt located along the top of the rockwall, over a 1200 m2 area, a continuous layer of debris completely covered the snow. This layer of debris had a mean thickness of 11.4 mm, which represents an accumulated volume in the order of 13 m3. Largely dominated by sand and granules (2-4 mm), the 28 samples collected for grain-size analysis also contained numerous thin shale flakes, many of which were longer than 10 mm. The largest flake measured had a width of 134 mm and a weight of 164.3 g. Six available C-14 dates provide information concerning mean cliff-top aeolian sedimentation rate for the last thousand years (c. 1.8 mm yr-1).