24 Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records, Part I

This session welcomes submissions related to applications of geochronology (e.g., U-Pb, 40Ar/39Ar) in stratigraphic research, including topics such as eruption and maximum depositional age estimation, provenance analysis, numerical modeling of geochronological data, and multi-disciplinary chronostratigraphic characterization.

Sunday, 19 October 2025
8:00 AM - 12:00 PM
HBGCC, 304C

Evaluating the accuracy of maximum depositional age estimations using a tandem LA-ICP-MS and CA-TIMS dataset

Paper number: 24-2
Program: Technical Sessions
Time: 8:25 AM – 8:40 AM

Authors

Abstract

Detrital zircon U-Pb geochronology is frequently used to determine the maximum depositional age (MDA) of (meta)sedimentary deposits, as strata cannot be older than their youngest zircon. Multiple methods have been developed for calculating the MDA, with each differing in how the youngest grain(s) are identified and how the age is calculated. Given the variety of methods that can produce widely differing estimates of the MDA, it can be difficult to determine which MDA method should be used for interpretations. Furthermore, there is a growing recognition that it is possible for some MDA estimations to be younger than the true depositional age, a risk that increases for methods that rely upon comparatively fewer analyses (e.g., the youngest single grain) and/or for samples that have undergone Pb loss. Here, we present an analysis of MDAs calculated from a tandem dataset of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and chemical abrasion thermal ionization mass spectrometry (CA-TIMS) for 92 samples compiled from the literature. We show that MDAs calculated from LA-ICP-MS datasets are too young compared to CA-TIMS MDAs for some commonly used methods, including the youngest single grain, weighted means of the youngest clusters that overlap at 1σ or 2σ uncertainty, the youngest statistical population, and the maximum likelihood age. Other methods produced MDAs that were, on average, older than the CA-TIMS MDA, including the tau method, the youngest Gaussian fit, and the youngest probability peak. Although the accuracy of each MDA method will depend on the specific sample and geologic context, these results provide a benchmark for which methods are most successful, namely, more conservative methods such as the youngest statistical population and the youngest Gaussian fit. These results also suggest that more accurate LA-ICP-MS dating is necessary to improve the robustness of MDA calculations.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413429

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