Coastal Stratigraphies as Indicators of Environmental Changes upon European Atlantic Coasts in the Late Holocene

Abstract

This paper is based upon work undertaken within contract EPOC-CT9000015, in the Environment Programme (Third Framework), Commission of European Communities, Brussels. Late Holocene (post c.4000 BP) stratigraphies from beach-barrier-lagoon environments are presented from five locations between northwest Spain (Galicia) and western Ireland. These meso - to macrotidal coasts are conditioned by high energy waves and storms. As such the coasts are sensitive potentially to the future impacts of rising sea-level and to climate-led controls on coastal behaviour. Consequently an objective of this study has been to establish the pattern of physical environmental changes recorded here, as a basis for helping assess the possible effects of future alterations in these coastal systems. The stratigraphies studied commonly show the occurrence of interleaved inorganic and organic sediments. The sedimentary sequences together evidence the importance of sand movements, alternating irregularly with periods of vegetation growth and relative environmental stability. Mechanisms of onshore sediment transfer appear to be linked to aeolian action, possibly most associated with storms, and to barrier overwashing. Repeated periods of sand movement are recorded particularly in barrier environments from about the fifteenth century AD onward. The nineteenth century to the present day also shows strong human influences upon coastal changes. Rates of relative sea-level rise on some coasts are placed at ~ 0.5-0.6mm yr ^-1 post c.2000 BP. Studies indicate that coastal barriers in Galicia appear to have been relatively stable, or even to have prograded, during this period. In Brittany and western Ireland similar systems record persistent retreat and barrier breakdown.