ABINITIO DERIVATION OF FORMULATIONS FOR PB-210 DATING OF SEDIMENTS

Basic formulations used in the sedimentary Pb-210 dating technique are derived from fundamental considerations. The formulations are applicable to models that assume either a constant rate of supply (CRS) of unsupported Pb-210 to the sediments or a constant initial concentration (CIC) of this Pb-210 in the sediments. A previously proposed expression linking age discrepancy to mass sedimentation rates afforded by the two models is found to be inadequate in explaining the observed discrepancy between the CIC and CRS ages of segments of an undisturbed sediment core. It is noted that this age discrepancy is attributable to the mathematical treatment of data in the two models. A new expression, relating age discrepancy to the fluxes of unsupported Pb-210 obtainable by the two models, is derived and found to give more accurate and consistent results.