Analytical and sampling constraints in 210Pb dating

210Pb dating provides a valuable, widely used means of establishing recent chronologies for sediments and other accumulating natural deposits. The Constant Rate of Supply (CRS) model is the most versatile and widely used method for establishing 210Pb chronologies but, when using this model, care must be taken to account for limitations imposed by sampling and analytical factors. In particular, incompatibility of finite values for empirical data, which are constrained by detection limit and core length, with terms in the age calculation, which represent integrations to infinity, can generate erroneously old ages for deeper sections of cores. The bias in calculated ages increases with poorer limit of detection and the magnitude of the disparity increases with age. The origin and magnitude of this effect are considered below, firstly for an idealised, theoretical 210Pb profile and secondly for a freshwater lake sediment core. A brief consideration is presented of the implications of this potential artefact for sampling and analysis.

Research Highlights
► CRS 210Pb dating provides a valuable means of establishing peat and sediment chronologies.
► Equating empirical data to terms in the CRS equation can generate erroneous chronologies.
► The disparity increases with age.
► Disparity is negligible with an unsupported 210Pb limit of detection of 1 Bq kg–1 or better.