Machair development and chronology in the Uists and adjacent islands

Several types of machair landforms are found in the Uists (Outer Hebrides) but the most distinctive are low altitude plains. Morphological and stratigraphical evidence suggests that both erosional and depositional processes, operating over a long period of time, have produced these sand plains and other landforms. A vast but relatively finite (partly shell-derived) sand supply was swept landwards across the gentle offshore rock platform assisted by a rising sea level to provide the initial pre-machair coastal accumulation. Phases of development can be dated using archaeological evidence, and 14C dating of offshore peat suggests that initiation probably took place before 5700 BP. Although the evidence is fragmentary, machair development appears to have consisted of long periods of stability, interrupted by episodes of major environmental disturbances. There is also evidence of coastal erosion and associated physiographic changes