Pb-based dating of recent sediments with the χ-mapping version of the Constant Sediment Accumulation Rate (CSAR) model.

The Pb-based method aims at determining the absolute age of recent sediments on the centennial scale. A family of models assumes that at the sediment-water interface the flux of unsupported Pb (Pb), F, relates to its initial activity concentration, A, and the mass sedimentation rate, w, as: F=Aw. Additional specific assumptions that allow for analytical formulations of the models are: i) constant A (CIC), constant F (CF), and constant F with constant w (CFCS). A model with constant w (CSAR) was suggested for completeness but never used because of the lack of a suitable analytical formulation. The TERESA model assumes random and independent variability for A and w, described by normal distributions. It systematically generates a large number (∼10) of potential solutions, whose performance for fitting the empirical Pb profile is quantified through the χ-function. This work aims to adapt the above methodology to formulate the χ-mapping version of the CSAR model. The performance of the model is evaluated with a set of synthetic and real cores for which an independent chronology is available. CSAR is able to capture the mean sedimentation rate from the Pb data and provides reliable chronologies and paleorecords of A, useful for tracking past changes in sedimentary conditions. CSAR provides an interesting different perspective for researchers working with Pb-based dating of recent sediments.