AEOLIAN DEPOSITS ON A SCOTTISH MOUNTAIN SUMMIT - CHARACTERISTICS, PROVENANCE, HISTORY AND SIGNIFICANCE

The summit plateau of The Storr (719 m) in northern Skye is mantled by a sheet of aeolian sediment up to 2.9m thick, covering an area of 33 000 m(2) with a volume of 41 000 m(3). The deposits are of massive, po orly sorted sand with significant components of silt and fine gravel, and contain clasts up to 109mm in length. The thickness and coarseness of the deposits decline westwards and northwards away from the highes t cliffs, implying that the sediment comprises particles dislodged fro m rockwalls and blown upwards in an accelerating vertical or near-vert ical airflow, settling through a lower-velocity flow onto.the plateau surface where they are trapped by vegetation. Radiocarbon dating of so ils buried under and within the deposits suggests that accumulation be gan after 7.2-6.9 calendar ka sp but before 5.6-5.3 calendar ka sp, an d was probably initiated by exposure of the present rockwall by a mass ive landslide at c. 6.5 +/- 0.5 calendar ka sp. Pollen analyses of bur ied organic horizons suggest that a vegetation mat dominated by grasse s and sedges was present throughout the period of sediment deposition. Sediment accumulation over much of the plateau averaged 10-20mm per c entury throughout the late Holocene, but reached c. 60mm per century i n the area of the thickest deposits. the volume of the deposits implie s the removal of 420-480mm of rock (averaged over the face) during the late Holocene, and suggests that small-scale granular disaggregation and release of small clasts constitute a major component of rockwall r etreat under present conditions. The origin of the Storr deposits sugg ests that plateau-top aeolian sediments on other Scottish mountains ac cumulated in a similar way, but have been eroded and redeposited on le e slopes following breakage of vegetation cover. (C) 1998 John Wiley & Sons, Ltd.