Skip to main content Accessibility help
×
Home

Evolution of a machair landscape: pollen and related studies from Benbecula, Outer Hebrides, Scotland

  • Graeme Whittington (a1) and Kevin J. Edwards (a2)

Abstract

Low altitude sandy plains (machair) are a common feature of the Atlantic coasts of the Outer Hebrides. They formed as a result of shoreward movement of material consequent upon a rise in Holocene sea levels. A number of earlier, partially inconclusive, investigations into machair evolution proposed that fuller understanding could arise from an examination of inter-tidal organic deposits, in so far as these could provide a fossil proxy record of the processes involved in machair formation. Study of a series of inter-tidal peats sites located on a beach platform at Borve, island of Benbecula, provided both spatial and chronological evidence for sand movement as well as furnishing new data on vegetational and environmental history. The pollen diagrams show a flora in which Calluna vulgaris (heather) and Poaceae (grass) are frequent dominants, while such arbroeal taxa as Betula (birch) and Corylus avellana-type (cf. hazel) are notable. The existence of birch–hazel woodland for the period c. 8855–6190 BP might conceivably have had a retarding effect on sand movement. Later cycles of sand movement would not have met such obstruction with the consequence that sand mobility and machair plain evolution could have been faster. Sand arrival at the seaward site (Borve 3), is dated to c. 6735 BP and it continued until c. 6045 BP, after which it slowed before increasing again from around 5990 BP. This sand incursion produced a machair plain over the Borve sites as part of a continuous, but variously paced, marine and aeolian process. The presence of charcoal from c. 6860 BP, with a major increase in charcoal to pollen ratios by 6190 BP, may suggest that natural or intentional burning of the vegetation cover of the machair occurred in Mesolithic times; if the burning was anthropogenic in origin, then it pushes the possible involvement of humans in machair destabilisation to a time long before the previously proposed Neolithic period. A wet slack deposit, dated to 3400 ± 70 BP, indicates a time when sand movement overwhelmed the area around the landward site (Borve 1) and when the rate of sand movement was likely to have been impeded. The data from Borve suggest that evolution of machair landforms occurs at a slow, variable rate and that there is considerable long-term stability.

Copyright

References

Hide All
Basset, J. A. & Curtis, T. G. F. 1985. The nature and occurrence of sand dune-machair in Ireland. PROC R IR ACAD 85B, 126.
Bennett, K. D., Whittington, G. & Edwards, J. L 1994. Recent plant nomenclatural changes and pollen morphology in the British Isles. QUATERN NEWSL 73, 16.
Boyd, J. M. & Boyd, I. C. 1990. The Hebrides, a natural history. London: Collins.
Bryant, V. M. 1979. Late fullglacial and postglacial pollen analysis of Texas sediments. Unpublished PhD thesis. University of Texas, Austin.
Edwards, K. J. 1996. A Mesolithic of the Western and Northern Isles of Scotland? Evidence from pollen and charcoal. In Pollard, T. & Morrison, A. (eds) The early prehistory of Scotland. 2338. Edinburgh: Edinburgh University Press.
Edwards, K. J., Whittington, G. & Hirons, K. R. 1995. The relationship between fire and long-term wet heath development in South Uist. Outer Hebrides, Scotland. In Thompson, D. B. A., Hestor, A. J. & Usher, M. B. (eds) Heaths and moorland: cultural landscapes. 240–8. Edinburgh: H.M.S.O.
Faegri, K. & Iversen, J. 1989. Textbook of pollen analysis. 4th edition by Faegri, K., Kaland, P. E. & Krzywinski, K.. Chichester: John Wiley & Sons.
Gilbertson, D. D., Kent, M., Schweninger, J.-L., Wathern, P. A., Weaver, R. & Brayshay, B. A. 1995. The machair vegetation of South Uist and Barra in the Outer Hebrides of Scotland: its interacting ecological, geomorphic and historical dimensions. In Butlin, R. A. & Roberts, N. (eds) Ecological relations in historical times: human impact and adaptation, 1744. London. Blackwelll.
Gimingham, C. H. 1964. Maritime and sub-maritime communities. In Burnett, J. H. (ed.) The vegetation of Scotland. 67142. Edinburgh: Oliver & Boyd.
Grimm, E. 1987. CONISS: a FORTRAN 77 program for stratigraphically constrained cluster analysis by the method of incremental sum of squares. COMPUT & GEOSCI 13, 1335.
Grimm, E. C. 1991 TILIA and TILLIA·GRAPH. Springfield: Illinois State Museum.
Hudson, G. 1991. Geomorphology and soils of the Outer Hebrides. In Pankhurst, R. J. & Mullin, J. M. (eds) Flora of the Outer Hebrides, 1927. London: Natural History Museum Publications.
Mate, I. 1992. The theoretical development of machair in the Hebrides. SCOTT GEOG MAG 108, 35–8.
Mather, A. S. & Ritchie, W. 1977. The beaches of the Highlands and Islands of Scotland. Edinburgh: Countryside Commission of Scotland.
Patterson, W. A. III, Edwards, K. J. & Maguire, D. J. 1987. Microscopic charcoal as a fossil indicator of fire. QUATERN SCI REV 6, 323.
Ritchie, W. 1966. The physiography of the machair of South Uist. Unpublished PhD thesis, University of Glasgow, 2 volumes.
Ritchie, W. 1979. Machair chronology and development in the Uists. PROC R SOC EDINBURGH B77, 107–22.
Ritchie, W. 1985. Inter-tidal and sub-tidal organic deposits and sea level changes in the Uists, Outer Hebrides. SCOTT J GEOL 21, 161–76.
Ritchie, W. & Whittington, G. 1994. Non-synchronous aeolian sand movements in the Uists: the evidence of the intertidal organic and sand deposits at Cladach Mór, North Uist. SCOT GEOG MAG 110, 40–6.
Stace, C. 1991. New flora of the British Isles. Cambridge: Cambridge University Press.
Swain, A. M. 1973. A history of fire and vegetation in northeastern Minnesota as recorded in lake sediment. QUATERN RES 3, 383–96.
Whittington, G. & Edwards, K. J. 1993. Vegetation change on Papa Stour, Shetland, Scotland: a response to coastal evolution and human interference? THE HOLOCENE 3, 5462.
Whittington, G. & Ritchie, W. 1988. Flandrian environmental evolution on north-east Benbecula and southern Grimsay, Outer Hebrides, Scotland. O'Dell Memorial Monograph, Department of Geography, University of Aberdeen. 21.

Keywords

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed