Mid- and late-Holocene evolution of the Dungeness foreland, UK

Abstract

The Dungeness foreland is located in the eastern part of the English Channel, and consists of over 500 gravel beaches which have accumulated since the mid-Holocene. The south coast of the foreland, between Jury's Gut and Galloway's Lookout, is characterised by alternating areas of marsh sediments and gravel which have previously been interpreted as evidence for several oscillations in sea level. Stratigraphic and diatom data from the marsh sediments in this area indicate that they accumulated under marine/ brackish and brackish tidal channel conditions, while pollen data from a peat bed recorded in the base of Wickmaryholm Pit show a removal and return of the marine influence at ca. 2038 ± 97 yrs B.P. and ca. 1000-700 yrs B.P., respectively. An established age/altitude graph of sea-level changes for the region shows that sea level changed little during the period of gravel deposition in the study area (ca. 4000-2000 yrs B.P.). It is therefore argued that the alternating gravel and marsh sediments of the study area probably accumulated as a result of changes in storm incidence and gravel supply, and not oscillations in long-term sea level. Under periods of high storm incidence, increased northward distal extension of the beach ridges in the study area has occurred, while under calmer conditions reduced distal extension has taken place. No clear relationship is apparent between long-term time/altitude changes in sea level and episodes of foreland development during the last ca. 4000 years. However, evidence for a regional episode of increased storm incidence at ca. 700–800 yrs B.P. may be recorded by the return of marine conditions to Wickmaryholm Pit, breaching of the Dungeness foreland at Rye, and a sudden increase in the altitude of the gravel beaches in Denge Beach. Identifying the importance of local and regional controls on foreland evolution is difficult, though, as the sensitivity of the foreland to processes operating at different spatial scales may well have changed through time.