[en] The vertical distribution of "2"1"0Pb is commonly used to date peat deposits accumulated over the last 100–150 years. However, several studies have questioned this method because of an apparent post-depositional mobility of "2"1"0Pb within some peat profiles. In this study, we introduce the Initial Penetration–Constant Rate of Supply (IP-CRS) model for calculating ages derived from "2"1"0Pb profiles that are altered by an initial migration of the radionuclide. This new, two-phased, model describes the distribution of atmospheric-derived "2"1"0Pb ("2"1"0Pb_x_s) in peat taking into account both incorporation of "2"1"0Pb into the accumulating peat matrix as well as an initial flushing of "2"1"0Pb through the uppermost peat layers. The validity of the IP-CRS model is tested in four anomalous "2"1"0Pb peat records that showed some deviations from the typical exponential decay profile not explained by variations in peat accumulation rates. Unlike the most commonly used "2"1"0Pb-dating model (Constant Rate of Supply (CRS)), the IP-CRS model estimates peat accumulation rates consistent with typical growth rates for peatlands from the same areas. Confidence in the IP-CRS chronology is also provided by the good agreement with independent chronological markers (i.e. "2"4"1Am and "1"3"7Cs). Our results showed that the IP-CRS can provide chronologies from peat records where "2"1"0Pb mobility is evident, being a valuable tool for studies reconstructing past environmental changes using peat archives during the Anthropocene. - Highlights: • Accurate age dating of peat and sediment cores is critical for evaluating change. • A new "2"1"0Pb dating model that includes vertical transport of "2"1"0Pb was developed. • The IP-CRS model provided consistent peat accumulation rates. • The IP-CRS ages were consistent with independent chronological markers. • The IP-CRS model derives peat ages where downward "2"1"0Pb transport is evidenced.