A Python implementation of the upgraded χ-mapping TERESA model for ²¹⁰Pb dating of recent sediments: Software and...

The ²¹⁰Pb dating method enables the absolute age determination of recent sediments on a centennial scale. The Time Estimates from Random Entries of Sediments and Activities (TERESA) model addresses common sedimentary scenarios characterized by ideal deposition, absence of post-depositional redistribution, and simultaneous but independent variability in sedimentation rates and initial activity concentrations. TERESA is a χ-mapping model-a novel methodological approach that uses numerical computations across a large set (∼10⁶) of potential solvers, representing diverse sedimentary conditions, to identify the one that minimizes a χ² function. Although the model's fundamentals and numerous applications, including validations with varved sediments, have been previously presented, the lack of user-friendly and freely available software has limited its broader adoption by the scientific community. This work aims to present an upgraded version of TERESA supported by numerical codes written in Python and freely available on GitHub and Zenodo. It includes an updated treatment of confidence intervals, the use of normal and lognormal distributions, and objective functions that incorporate reference dates. Model performance is demonstrated using a set of cores from the literature with independent chronologies or time markers. The main advantages over classical models are discussed. The work provides novel numerical tools that enable fresh insight into the ²¹⁰Pb-based dating of recent sediments.