Three decades of dating recent sediments by fallout radionuclides: a review

This paper reviews the 210 Pb dating programme carried out at the University of Liverpool over a period of three decades since its inception by Frank Oldfield in the mid-1970s. The work at Liverpool has included studies of the basic processes controlling the supply of 210 Pb to the various natural archives, as well as the development of a detailed and systematic methodology for dating the environmental records in these archives. The assumption that 210 Pb fallout at any given location is constant when measured on timescales of a year or more has been tested using data on 210 Pb concentrations in UK rainwater spanning more than 40 years, and a simple atmospheric model developed to account for observed spatial variations in the flux over large land masses. The basic assumptions of the CRS dating model have been tested in detail using mass balance studies of fallout radionuclides in catchment/lake systems, and in general using data from a large number of separate studies. The Liverpool data base is used to illustrate the wide ranging applicability of the 210 Pb dating method. Results are shown from lakes varying in size from the very small to the very large, and with sedimentation rates ranging from the very fast to the very slow. The particular difficulties of dating sediment records from Desert Lakes and Polar Regions with very low atmospheric fluxes are discussed, with unexpected results in some cases.