210-LEAD DATING OF A MODERN PERIOD SALT-MARSH DEPOSIT FROM THE SEVERN ESTUARY (SOUTHWEST BRITAIN), AND ITS IMPLICATIONS

The Pb-210 dating of a saltmarsh section from the mid-Severn Estuary has facilitated the construction of a chronology based on the temporal variation of commonly occurring pollutants, namely particulate coal dust, copper, lead and zinc. The chronology identifies three significant datum levels at 1958 +/- 4 years, 1950 +/- 4 years and 1933 +/- 7 years, based on the temporal trends of pollutants within the sediment sequence. Based on the Pb-210 dates of the deposits at these levels, averaged vertical saltmarsh accretion rates for the studied section can be shown to be between 0.35 and 0.40 cm yr-1. It is therefore concluded that the marsh area studied is accreting vertically at a rate comparable to local sea-level rise.