During Earth’s history, geosphere-biosphere interactions were often determined by momentary, catastrophic changes such as large explosive volcanic eruptions. The Miocene ignimbrite flare-up in the Pannonian Basin, which is located along a complex convergent plate boundary between Europe and Africa, provides a superb example of this interaction. In North Hungary, the famous Ipolytarnóc Fossil Site, often referred to as “ancient Pompeii”, records a snapshot of rich Early Miocene life buried under thick ignimbrite cover. Here, we use a multi-technique approach to constrain the successive phases of a catastrophic silicic eruption (VEI ≥ 7) dated at 17.2 Ma. An event-scale reconstruction shows that the initial PDC phase was phreatomagmatic, affecting ≥ 1500 km2 and causing the destruction of an interfingering terrestrial–intertidal environment at Ipolytarnóc. This was followed by pumice fall, and finally the emplacement of up to 40 m-thick ignimbrite that completely buried the site. However, unlike the seemingly similar AD 79 Vesuvius eruption that buried Pompeii by hot pyroclastic density currents, the presence of fallen but uncharred tree trunks, branches, and intact leaves in the basal pyroclastic deposits at Ipolytarnóc as well as rock paleomagnetic properties indicate a low-temperature pyroclastic event, that superbly preserved the coastal habitat, including unique fossil tracks.
In this paper the first quantitative description and volcanological interpretation is given of the Badacsony Hill, the latter being the most well-known butte of the Bakony-Balaton Highland Volcanic Field (BBHVF). The pyroclast/lithics ratio of the pyroclastics was investigated by using point-counting image analysis methodology on the surfaces of handcut specimens. The isometrical shape of different grains allowed the obtained 2D data to be converted to 3D volume data. By using this methodology it was possible to infer the relative depth of explosions with respect to the synvolcanic surface and the syneruptive morphology; moreover, the effusive and explosive phases of the volcanism could be identified.The results of point-counting image analysis and the position and extent of the phreatomagmatic sequence on the Badacsony Hill imply that the Badacsony volcano was a monogenetic (probably polycyclic) tuff ring or shallow maar volcano. Such volcanism is associated with the interaction of hot, molten material with groundwater, and this triggers shallow explosions. The low amount of accidental lithics within the deposits confirms the tuff ring scenario; however, such a low amount of accidental lithics could also be observed within deposits from shallow maars when these were formed on a soft, unconsolidated basement. Such an alternative model is envisaged for Badacsony.The development of the volcanism can be divided into explosive and effusive phases, based on the different composition and on the relative stratigraphic position of the respective phreatomagmatic sequences. Based on these results the present study proposes a volcanic evolution model. Given the scarcity of volcanological data on the Badacsony Hill, the results presented here could give a basis for further regional volcanological investigations.Keywords: Badacsony, Bakony-Balaton Highland Volcanic Field, image analysis, maar, monogenetic, phreatomagmatic eruption, tuff ring Összefoglalás A tanulmányban a Bakony-Balaton-felvidéki vulkáni terület (BBVT) legismertebb tanúhegyén, a Badacsonyon kibukkanó freatomagmás piroklasztit-összlet első kvantitatív leírását és vulkanológiai értelmezését mutatjuk be. A piroklasztitok juvenilis/litikus törmelékeinek arányát pontszámlálásos módszerrel vizsgáltuk vágott kézipéldány-fel színe -ken. A felület%-ban kapott eredményeket a kőzetminták teljes térfogatára vonatkozónak vettük. E módszer segít ségével meghatároztuk a freatomagmás robbanások relatív mélységét a szinvulkáni felszínhez képest, következ tetéseket vontunk le a lehetséges szineruptív vulkánmorfológiára, valamint a terepi megfigyelések és korábbi tanulmányok alapján rekonst ruáltuk a vulkán működésének teljes fejlődéstörténetét.A képelemzés során megállapítottuk a litikus elegyrészek minimális arányát. Ebből, valamint a piroklasztitok térbeli elter jedéséből és rétegtani helyzetéből valószínűsíthető, hogy a Badacsony egy monogenetikus (esetleg policiklikus) tufagyűrű vagy sekély maar vulkán volt, amelynek kialakulásában a víz-magma kölcsönhatás követke...
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