Application of luminescence dating and geomorphological analysis to the study of landscape evolution, settlement and climate change on the Channel Island of Herm

The optically stimulated luminescence (OSL) dating of sands and palaeosol horizons, sampled as part of an archaeological investigation and supported by geomorphological analysis, has been applied to identify critical stages in the development of the landscape on Herm, one of the Channel Islands that lies off the coast of Guernsey, on which megalithic monuments were constructed during the Neolithic period. In particular, there were three phases of significant aeolian activity during the prehistoric period, the onsets dated by OSL in this study to ca 4, 3 and 2.3 ka ago, where the first phase marked a significant change in the long term trend of aggradation of soils that persisted during the next two millennia. OSL ages were also obtained for palaeosols in which there was evidence of ploughing, placing this activity in the late 2nd millennium BC and the 4th and 13th centuries AD. The OSL ages for basal deposits of dune sands that cover the northern part of the island indicate that they were formed by phases of intense aeolian activity during the medieval period, commencing in the 13th century AD and continuing for several hundred years, which can be correlated with documented high intensity storms in the North Atlantic within the period 13th-15th centuries AD. The phases of significant aeolian activity dated by OSL to ca 4 and 2 ka ago can be linked with those detected in different regions of the North Atlantic coastal areas. The availability of chronologies for aeolian horizons provides a valuable tool in the study of the evolution of coastal landscape and how past coastal communities responded to climate change.