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Lithofacies architecture of andesitic-rhyolitic lava dome complex: insights into multiple growth and submarine-subaerial transition, Som Hill, Tokaj Mts, Carpathian-Pannonian region

János Szepesi1,2 Kata Molnár1,2, Zsolt Benkó1,3, Andrea Di Capua4, Máté Szemerédi5, Elemér Pál-Molnár5, Szabolcs Harangi2,6, Réka Lukács2

  • Affiliations: 1HUN-REN Institute for Nuclear Research, Debrecen, Hungary 2MTA--HUN-REN CSFK Lendület "Momentum" PannonianVolcano Research Group, Institute for Geological and Geochemical Research, HUN-REN Research Centre for Astronomy and Earth Sciences, Budapest, Hungary 3Department of Mineralogy and Geology, University of Debrecen, Debrecen, Hungary 4CNR -- IGAG, R. Cozzi 53, 20125, Milan, Italy 5Department of Geology, "Vulcano" Petrology and Geochemistry Research Group, University of Szeged, Szeged, Hungary 6Eötvös Loránd University, Department of Petrology and Geochemistry, Budapest, Hungary 

  • Presentation type: Poster

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

  • Poster Board Number: 20

  • Programme No: 3.7.27

  • Theme 3 > Session 7

Abstract

Well-preserved examples of volcanic formations comprising submarine to subaerial emergences are rare in the geological record. The present work explores the volcano-sedimentary stratigraphy of Som Hill succession (>200m), which composed of a Miocene (12.4-11.2 Ma) andesitic-rhyolitic effusives interbedded with sedimentary and pyroclastic deposits. Aiming this, over 100 boreholes were revised. Additional fieldwork was conducted on the active quarry and surface exposures. Effusive lithofacies comprises rhyolite and andesite lavas, consisting of an inner coherent core that grades outward into clast supported breccias (autoclastic, hyaloclastite and peperite). Volcano-sedimentary lithofacies comprise pyroclastic deposits including diverse lapilli tuffs with varying lithic enrichment, secondary volcaniclastic deposits including monomictic breccias and tuff-matrix breccias, volcanogenic sandstones and mudstones. Together, these lithofacies describes (1) submarine andesitic lava domes and flows (2) volcaniclastic - sedimentary units (3) submarine rhyolitic cryptodomes (4) pyroclastic deposits and (5) subaerial andesitic-rhyolitic domes and flows. During the eruptive period, two significant effusive events took place with a similar cyclic pattern. The initial effusive activity was characterized by andesitic composition followed by emplacement of silicic lavas. This pattern suggests that magma batches of varying compositions were being excavated. Sedimentation occurred before and at the onset of the volcanism, while explosive products were deposited after the initial cycle. The change in the fragmentation style of the lavas towards the top of the succession, along with the pyroclastic deposits, indicates a transition from shallow submarine to subaerial environment. Acknowledgements.  Funds. National Research, Development and Innovation Office (No. 145905) and MTA--HUN-REN CSFK Lendület "Momentum" PannonianVolcano Research Group.