Measurement of 226 Ra activity concentrations is often used to estimate supported levels of 210 Pb for purposes of geochronology. However, the implicit assumption that supported 210 Pb and 226 Ra are in secular radioactive equilibrium may not always be true because of the migration of an intermediate product, gaseous 222 Rn. As a consequence, supported 210 Pb activity concentration might be lower than the measured 226 Ra value, which was the case in a core collected from the South Adriatic Pit. Here we present a new approach to improve the determination of supported 210 Pb, which is based on correction of 226 Ra activity concentrations using the average ( 210 Pb/ 226 Ra) activity ratio in deeper sediment layers. Using this approach, sedimentation rates for the South Adriatic Pit with a constant rate of supply model and a constant initial concentration model were 0.054 g/cm 2 /a and 0.070 g/cm 2 /a, respectively.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.