Non‐synchronous aeolian sand movements in the Uists: The evidence of the intertidal organic and sand deposits at Cladach Mor, North Uist

Abstract

The coastal wind‐blown sands of the Outer Hebrides, known as machair, are derived from sands of glacial and biogenic origins. These sands were swept onshore in the postglacial marine transgression. The early sands developed as a series of overlapping landform suites, often burying existing soils, marshes and lacustrine deposits. Today, fragments of these terrestrial organic materials with intercalated sand layers outcrop on a few protected intertidal zones where they provide evidence for both coastline erosion and machair transgression. One such deposit at Cladach Mor in North Uist is over one metre thick and extends to low water mark. It has been analysed sedimentologically and palynologically. 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 site has prompted a revision of the existing hypothesis of sand movements on to the coastal plains of the Uists.

Key words:

• Machair
• Palynology
• Sedimentology
• Outer Hebrides
• Coastline erosion