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Insights into the build-up to the early Permian Gargazzone super-eruption (Southern Alps) from high-precision zircon petrochronology

María Paula Marroquín-Gómez 1, Dawid Szymanowski1, Lorenzo Tavazzani1, Corrado Morelli2, Francesca Forni3, Peter Brack1, Evelyn Kustatscher4.

  • Affiliations: 1Department of Earth and Planetary Sciences ETH Zürich, Switzerland; 2Servizio Geologico Provincia Autonoma di Bolzano; 3University of Milan, Italy; 4Naturmuseum Südtirol, Italy

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 213

  • Programme No: 1.9.20

  • Theme 1 > Session 9

Abstract

The Athesian Volcanic District of the Southern Alps (Northern Italy) preserves an exceptional record of voluminous, evolved, early Permian magmatism developed in an extensional tectonic period between the Variscan Orogeny and the onset of Pangea's breakup. Volcanism began around 280 Ma, lasted at least 4 Myr[1], and produced eruptive materials spread over more than 4500 km². This magmatic activity is characterized by at least two caldera-forming super-eruptions. Efforts to reconstruct the magmatic history of this district have included detailed stratigraphic and mapping studies, as well as geochemical and geochronological analyses[2]. However, to better understand compositional, spatial, and temporal patterns in eruptive activity---and their correlation with recognized changes in the terrestrial ecosystem[3]---state-of-the-art, high-precision zircon U-Pb geochronology (i.e. CA-ID-TIMS) is required. In this contribution, we focus on the older of the two recognized caldera cycles, leading to the first collapse of pre-caldera volcanic edifices and the formation of the up-to-900-meter-thick Gargazzone Ignimbrite. Extensive sampling of the Gargazzone Ignimbrite across geographically and stratigraphically distributed outcrops was conducted to improve estimates of eruption volume. Zircon geochemistry and high-precision geochronology of these samples and volcanic units predating this event will be used to evaluate temporal and compositional changes of the Athesian magmatic system as it built up to the climactic event. [1] Boscaini, A. et al., Contrib. Mineral Petrol., (2025) 180, 10. [2] Marocchi, M. et al., J Geol., (2008) 116, 480. [3] Valle, F. et al., Riv. Ital. Paleontolog. Stratigr., (2023) 129.