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Abstract :
[en] Numerous fundamental events in the history of life on Earth took place during the Cambrian Period, including the Cambrian Explosion, the Cambrian Substrate Revolution, and onset of the Ordovician Planktonic Revolution. Despite the importance of these evolutionary milestones, determination of the timing and driving mechanisms of these events has been impeded by limited time constraints coupled with widespread endemism, leading to unclear biostratigraphic correlations among key localities.
In the Geologic Time Scale 2020 (GTS2020), the time calibration of the Cambrian Period relies on 16 radioisotope ages. Information about age uncertainties is not included in GTS2020 or in the International Chronostratigraphic Chart v. 2024/12 (ICC 2024/12), with the exception of the Ediacaran/Cambrian and Cambrian/Ordovician boundaries. Since 2020, 43 new radioisotope ages and 5 cyclostratigraphic sections covering 15 biozones have been identified. Combined with the GTS2020 and modelled using the Bayesian “ModifiedBchron” R package (Trayler et al., 2020), these data substantially refine the Cambrian Time Scale and provide continuous uncertainty estimates.
This new Bayesian Time Scale (BTS) provides ages and uncertainties for stage boundaries (and all points inbetween) that closely align with the GTS2020 and ICC 2024/12 estimates. The only major difference between the previous estimates and this new Cambrian BTS is at the base of the Wuliuan Stage, which is approximately 2.5 Myr younger than in GTS2020 or ICC 2024/12. This 2.5 Myr offset reflects the incorporation of new radioisotope ages, which are precisely located in biozones that bracket the base of the Wuliuan Stage. The new Cambrian BTS also clearly identifies those stratigraphic intervals with limited or no numerical age constraints (e.g., the middle Fortunian to Stage 3, and Wuliuan to Jiangshanian stages).
