Pine pollen in intertidal sediments from Poole Harbour, UK; implications for late-Holocene sediment accretion rates and sea-level rise

Abstract

Abstract Marked differences exist between long- and short-term estimates of sea-level rise in southern England. Crucial to resolving these differences is the development of dating techniques capable of bridging the gap between the late-Holocene radiocarbon chronology and the more recent 210 Pb and observational records of sediment accretion and sea-level change. In this paper we identify an increase in Pinus pollen in a sediment core collected from a saltmarsh in Poole Harbour, Dorset. This has been dated to ca. 1750 AD and reflects the historically documented spread of coniferous plantations across the region. This biostratigraphic age horizon, together with other pollen and radiocarbon data, is used to analyse long- and short-term rates of sediment accretion and sea-level change. A basal radiocarbon date indicates a rise in relative sea-level since 1510–1260 cal. yr BC (3130±60 14 C yr BP) of 1.99 m, at a rate of approximately 0.59 mm a -1 . Between ca. 1750 AD and ca. 1890 AD sediment accretion rates rose from 0.29 mm a -1 to 1.14 mm a -1 , perhaps reflecting an acceleration in relative sea-level rise. These rates increased further to 7.17 mm a -1 after ca. 1890 AD, following the development of a Spartina anglica dominated saltmarsh in Poole Harbour. These data demonstrate that caution should be exercised when using sediment accretion rates from saltmarshes recently colonised by S. anglica as proxy data for sea-level rise.