EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
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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

Heiðrikur Mortensen1, Rasmus Andreasen1, Stéphane Bodin1, Hamed Sanei1, Thomas Ulrich1, Sylvain Richoz2, Sofie Lindström3, Ambre Luguet4, Lawrence Tanner5, and Christian Tegner1
Heiðrikur Mortensen et al.
  • 1Aarhus University, Department of Geoscience, Aarhus, Denmark
  • 2Lund University, Department of Geology, Lund, Sweden
  • 3Copenhagen University, Department of Geosciences and Natural Resource Management, Copenhagen, Denmark
  • 4Bonn University, Insitute for Geosciences, Bonn, Germany
  • 5Le Moyne College, Department of Biological and Environmental Sciences, New York, USA

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 T-bed, this could show that the onset of CAMP weathering and mass extinction would have therefore coincided. However, further work is needed to identify the relative role of CAMP volatile emission during volcanic activity versus post-eruption weathering of basalts.

How to cite: Mortensen, H., Andreasen, R., Bodin, S., Sanei, H., Ulrich, T., Richoz, S., Lindström, S., Luguet, A., Tanner, L., and Tegner, C.: 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, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11171,, 2023.