NONSYNCHRONOUS AEOLIAN SAND MOVEMENTS IN THE UISTS - THE EVIDENCE OF THE INTERTIDAL ORGANIC AND SAND DEPOSITS AT CLADACH-MOR, NORTH-UIST

The coastal wind-blown sands of the Outer Hebrides, known as machair, are derived from sands of glacial and biogenic origins. These sands we re swept onshore in the postglacial marine transgression. The early sa nds developed as a series of overlapping landform suites, often buryin g existing soils, marshes and lacustrine deposits. Today, fragments of these terrestrial organic materials with intercalated sand layers out crop on a few protected intertidal zones where they provide evidence f or both coastline erosion and machair transgression. One such deposit at Cladach Mor in North Uist is over one metre thick and extends to lo w water mark. It has been analysed sedimentologically and palynologica lly. The results give a chronology for, and show the complex nature of , the inland movement of sand across a loch basin which lay originally landward of the transgressive coastal sand body. Research at this sit e has prompted a revision of the existing hypothesis of sand movements on to the coastal plains of the Uists.