Sea-level changes in south east England and northern France

Abstract

The aim of the research was to provide new sea-level index points,with the intention of identifying any cross-channel similarities and comparing the results to geophysical models of relative sea-level change. The research successfully provided new sea-level index points from the Pevensey levels, East Sussex; the Canche Estuary, Pas de Calais and the Somme Estuary, Picardie, which were validated using stratigraphic pollen,diatom,foraminiferal snd AMS radiocarbon dating analysis. The results pointed to the presence of a coastal barrier thoughout the mid-Holocene at Pevensey and the Somme which complicated the pattern of coastal sedimentation observed at these sites.A clear pattern of barrier de-stabilisation can be seen to take place either side of the Channel c.3000 years cal BP. A cross-channel comparison identified three similar transgressive events either side of the English Channel, c. 5500, 3000 and 2200 cal years BP. The observed results from each site were then compared to the predicted data( Lambeck pers.comm) .in order to determine whether the observational data could be used to validate the modelled data.The comparisons showed that for the sites in south east England the modelled data tended to over-predict sea-level rise for the mid-t o late- Holocene whereas the model tended to under-predict sea-level rise for the sites in northern France. The new observational data which the research provided could be used to further validate Lambeck's (1990,1997) geophysical model. The effects of local coastal processes, such as tidal range, crustal subsidence and barrier-dynamics were used to aid the comparisons between the pattern of sediment deposition and thus the sea-level signals.These findings suggested that reconstructions should be restricted to sites at an estuary-sized scale.