High-precision U-Pb geochronology and Bayesian age-depth modeling of the glacial-postglacial transition of the southern Parana Basin: Detailing the terminal phase of the Late Paleozoic Ice Age on Gondwana

The timing of the terminal deglaciation of the Late Paleozoic Ice Age - LPIA in the Parana Basin has been under investigation. However, the low availability of high-precision radioisotopic ages prevents the construction of a detailed chronostratigraphic framework necessary to constrain the demise of the glaciation and perform corre-lation with contemporaneous records across neighboring basins and within the extensive Parana Basin. This study aims to contribute to the chronostratigraphic detailing of the Carboniferous-Permian succession of the southern Parana Basin, interval preserving LPIA glacial-postglacial transition. Therefore, we document new high-precision U-Pb radioisotopic ages and reexamine previously published samples through single crystal chemical abrasion, isotope dilution-thermal ionization mass spectrometry (CA-IDTIMS). We integrate all high -precision radioisotopic ages into the first Bayesian age-depth models for the late Carboniferous-early Permian succession recorded in the southern Parana Basin. Age-depth models were performed on DU-08-RS and HN-120-RS drill cores, located in the Capane and Candiota paleovalleys, respectively. The weighted mean 206Pb/238U date for the Rio Bonito Formation are 297.914 +/- 0.10 (T6), 297.495 +/- 0.11 (HN), 296.796 +/- 0.114 (T1), 296.293 +/- 0.098 (T1.5), 296.252 +/- 0.117 (T2), and 296.148 +/- 0.136 Ma (RB). For the Itarare Group sample, the weighted mean date is 301.809 +/- 0.224 Ma (ITA). T1 and T2 high-precision ages turned out to be older than LA-ICP-MS ages published before (Cagliari et al., 2014), and RB and ITA ages younger (Cagliari et al., 2016). Age -depth models constraints the Rio Bonito Formation between Gzhelian and Sakmarian stages, encompassing-6.9 and-1.6 Myr in cores DU-08-RS and HN-120-RS, respectively. The results demonstrate that the successions of the Rio Bonito Formation recorded in Capane and Candiota paleovalleys are contemporaneous. They also corrob-orate to assign the final glaciation to the early Gzhelian (Late Pennsylvanian) and to place the Carboniferous -Permian boundary within the Rio Bonito Formation, in the study area.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

This study aims to provide detailed chronostratigraphic information about the terminal deglaciation of the Late Paleozoic Ice Age in the Parana Basin. By using high-precision radioisotopic ages and Bayesian age-depth models, the researchers determine the timing of the glacial-postglacial transition and the Carboniferous-Permian boundary in the study area.