A distal record of the Middle Miocene silicic eruption of the Carpathian-Pannonian Region stored within the Dinaride Lake System : implications for tephrostratigraphy and emplacement of volcaniclastic deposits

Brlek, Mihovil and Trinajstić, Nina and Schindlbeck-Belo, Julie Christin and Kutterolf, Steffen and Vukovski, Matija and Guillong, Marcel and Marković, Sava and Šuica, Sanja and Wang, Kuo‑Lung and Lee, Hao‑Yang and Gaynor, Sean P. and Brčić, Vlatko and Mišur, Ivan and Grizelj, Anita and Kurečić, Tomislav and Lazar, Jasmina Martinčević and Milošević, Monika and Baranyi, Viktória and Kukoč, Duje and Gilg, H.Albert and Georgiev, Stoyan and Lukács, Réka (2024) A distal record of the Middle Miocene silicic eruption of the Carpathian-Pannonian Region stored within the Dinaride Lake System : implications for tephrostratigraphy and emplacement of volcaniclastic deposits. INTERNATIONAL JOURNAL OF EARTH SCIENCES, 113. pp. 1427-1455. ISSN 1437-3254 (print); 1437-3262 (online)

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Abstract

Reliable reconstructions of tephrostratigraphy and emplacement mechanisms of Early to Middle Miocene volcaniclastic deposits across the Alpine-Mediterranean region may yield important clues as to the nature, spread, volume, magnitude and frequency of large silicic eruptions of the Carpathian-Pannonian Region. Here we report on a sequence of Middle Miocene volcaniclastic deposits intercalated with lacustrine strata from the Livno-Tomislavgrad Basin, part of the Dinaride Lake System. We applied a multi-proxy approach to elucidate their source, decipher their emplacement mechanism, and evaluate their basin-scale and regional correlativity. New high-precision zircon geochronology (~ 14.32 Ma) reveals their simultaneity with numerous volcaniclastic deposits (and their alteration products) widely spread across the Alpine-Mediterranean region. Additionally, their correlativity is confirmed at the scale of the Livno-Tomislavgrad Basin, based on similar lithostratigraphy, mineralogy and volcanic glass geochemistry. Newly obtained zircon Hf isotope data imply that Livno-Tomislavgrad Basin distal volcaniclastic deposits and ~ 14.36 Ma Harsány ignimbrite of the Carpathian-Pannonian Region had shared a parental eruptive center. However, different volcanic glass geochemistry, bolstered by the high-precision geochronology, suggests distinct eruption events, implying more frequent explosive volcanism of the Carpathian-Pannonian Region during Middle Miocene than previously recognized. We suggest that the ~ 14.32 Ma fine fallout tephra, deposited in the distal basin in the Dinarides (> 400 km from the source), was likely re-mobilized by water-driven hillside erosion from the extensive paleo-relief, and further transported via land-derived gravity flows. Upon entering the lake, the gravity flows likely transformed into subaqueous sediment density flows. These deposited ~ 1 to 7-m-thick overall graded volcaniclastic turbidites, thinning away from the presumed source of tephra re-mobilization. Although over-thickened, the ~ 14.32 Ma Livno-Tomislavgrad Basin volcaniclastic deposits can still serve as a reliable tephro- and tectono-stratigraphic markers due to their rapid mode of accumulation.

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