Platinum-group elements of the Kuhjoch section (Austria) link the onsets of weathering of the Central Atlantic Magmatic Province and the end-Triassic mass extinction

• Main Authors: Mortensen, Heiðrikur, Andreasen, Rasmus, Bodin, Stéphane, Sanei, Hamed, Ulrich, Thomas, Richoz, Sylvain, Lindström, Sofie, Luguet, Ambre, Tanner, Lawrence, Tegner, Christian
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: /dk/atira/pure/core/keywords/TheFacultyOfScience; Faculty of Science; end-Triassic crisis; mass extinction; large igneous province; Platinum group elements; Ocean acidification
• Online Access: https://curis.ku.dk/portal/da/publications/platinumgroup-elements-of-the-kuhjoch-section-austria-link-the-onsets-of-weathering-of-the-central-atlantic-magmatic-province-and-the-endtriassic-mass-extinction(2bb58d8a-d97e-44ff-beec-d091e9bc9b3a).html; https://doi.org/10.5194/egusphere-egu23-11171; https://curis.ku.dk/ws/files/357688938/Platinum_group_elements_of_the_Kuhjoch_section_Austria_link_the_onsets_of_weathering.pdf

The end-Triassic mass extinction (ETME; c. 201.6 Ma), one of the so-called “big-five” mass extinctions in the Phanerozoic era, is associated with widespread marine anoxia, ocean acidification, global warming, carbon cycle perturbations (δ13C) and an extinction of diverse marine and terrestrial groups. This extinction is frequently linked to the volcanic activity in the Central Atlantic Magmatic Province (CAMP) which is often cited to explain e.g., the correlative negative carbon excursions across many sections, mutagenesis of land plants by Hg-toxicity, and enrichment of Hg/TOC. Despite this, the exact identification of a volcanic signal in many of these sections is not well constrained. In this study we present high-precision platinum group element (PGE: Ir, Ru, Pt, Pd) and Re data for the Triassic-Jurassic boundary succession at the Kuhjoch section (Austria). These are the first results from our new analytical setup using high-pressure asher digestion, isotope dilution and multi-collector inductively-coupled plasma mass spectrometry for precise determination in low concentration (e.g. ppt) samples such as sediments. The PGE and Re concentrations and patterns vary significantly with stratigraphy. The c. 13 m of clayey sediments above the onset of the extinction (marked by the c. 16 cm thick T-bed) show pronounced enrichment in Pt, Pd and Ir concentrations relative to the under- and overlying carbonate dominated stratigraphy. Their PGE patterns are non-chondritic with Pd/Ir and Pt/Ir similar to CAMP basalts. Normalised for lithology (Al2O3), however, there are no significant variations in Pt, Pd and Ir values below, within and above the clayey sediments. Re and Ru are, however, depleted compared to the other PGEs in the clayey interval, something also observed in some CAMP basalts. One possibility is therefore to interpret the PGE-rich, clayey sediments, including the main extinction interval in the basal portion, as recording increased weathering of CAMP basalts. As the PGE enrichment increases up through the ...