Holocene coastal change in East Norfolk, UK: palaeoenvironmental data from Somerton and Winterton Holmes, near Horsey

Abstract

We present palaeoenvironmental results from two cores, Winterton Holmes (GY2) and Somerton Holmes (GY3), south of Horsey, East Norfolk. The upper transgressive contact of the peat of cores GY2 and GY3 is dated to 2355–2742 cal. years bp and 2761–2949 cal. years bp, respectively. The litho- and biostratigraphical data show that both these peat contacts represent sea-level index points formed around mean high water spring tides during a positive tendency of sea-level movement, as saltmarsh indicators near the top of, and immediately above the peat show its deposition within intertidal environments. These sea-level index points when combined with other sea-level observations and predictions from East Norfolk, confirm an upward trend of Holocene relative sea-level change typical of an area at, or beyond, the margins of the last British ice sheet; rapid in the early Holocene then at a much reduced rate in the mid- and late Holocene. Late Holocene rates of relative uplift or subsidence are calculated for East Norfolk by subtracting a model of relative sea level from each index point and then calculating the best-fit linear trend. The late Holocene rate of relative sea-level rise (or land subsidence) is 0.67 ± 0.06 mm −1 which is c . 1 mm a −1 less than the twentieth-century mean sea-level trend estimated from Lowestoft tidal station, thus agreeing with the consensus of opinion that global sea levels have risen between 10 and 20 cm over the past century.