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Calcium isotopes support spatial redox gradients on the Tethys European margin across the Triassic-Jurassic boundary
Chemical Geology ( IF 3.6 ) Pub Date : 2024-12-05 , DOI: 10.1016/j.chemgeo.2024.122530 Ashley N. Prow-Fleischer, Zunli Lu, Clara L. Blättler, Tianchen He, Pulkit Singh, Preston Cosslett Kemeny, Jordan P. Todes, Alexandre Pohl, Tripti Bhattacharya, Bas van de Schootbrugge, Paul B. Wignall, Simona Todaro, Jonathan L. Payne
Chemical Geology ( IF 3.6 ) Pub Date : 2024-12-05 , DOI: 10.1016/j.chemgeo.2024.122530 Ashley N. Prow-Fleischer, Zunli Lu, Clara L. Blättler, Tianchen He, Pulkit Singh, Preston Cosslett Kemeny, Jordan P. Todes, Alexandre Pohl, Tripti Bhattacharya, Bas van de Schootbrugge, Paul B. Wignall, Simona Todaro, Jonathan L. Payne
The end-Triassic mass extinction was among the most severe biotic crises of the Phanerozoic. It has been linked with the global expansion of marine anoxia, and the prolongation of these conditions within epeiric seas has been proposed as a cause for the suppression of biodiversity during the early Jurassic Hettangian Stage. Testing this interpretation is complicated by spatially heterogeneous patterns of local marine redox conditions within the western Tethys European Epicontinental Shelf. In this study, we assess the redox state within this region by focusing on two carbonate successions in Italy, a peritidal platform at Mount Sparagio, Sicily, and an offshore ramp deposit at Val Adrara in the Southern Alps. Based on previously published I/Ca ratios, these locations record distinct local background redox conditions, with Val Adrara showing a notably lower pre-extinction oxygen saturation state than Mount Sparagio. Here, we measure δ13 C and δ18 O at Mount Sparagio and δ44 Ca and trace element ratios at both sites to identify the roles of mineralogical and diagenetic effects on the preservation of primary redox signals. A numerical framework of multiple elemental (Sr, Mg, Mn, I) and isotopic (δ13 C, δ18 O, δ44 Ca, δ238 U, and δ34 SCAS ) ratios was constructed to recognize modes of carbonate diagenesis and source-mixing in the data. While diagenesis is impossible to completely rule out, our state-of-the-art approach provides robust evidence against common forms of diagenetic alteration as the main drivers of the overall paleoredox proxy trends.
更新日期：2024-12-05
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