# A 13.06 Ma widespread ignimbrite in the Pannonian Basin captured a snapshot of shallow marine to coastal environment in Central Paratethys

## TL;DR

A 13.06 million-year-old volcanic deposit in Hungary reveals a coastal marine environment at the time of a massive eruption in the Central Paratethys region.

## Contribution

The study presents new geochemical and age data for the Dobi Ignimbrite, linking it to a marine-coastal setting during a major volcanic event.

## Key findings

- The Dobi Ignimbrite is dated to 13.06 Ma and has a volume consistent with a high-end VEI 7 eruption.
- The ignimbrite contains marine foraminifera and phreatomagmatic features, suggesting a coastal or marine eruption site.
- The presence of plant material correlates with known volcanic floras from the Badenian/Sarmatian boundary.

## Abstract

Voluminous Miocene silicic volcanism sourced mainly from the extensional Pannonian Basin played a major role in the evolution of the Central Paratethys. Here, we identify a widely distributed (> 3150 km2) member of the Upper Rhyolite Tuff in Hungary, called the Dobi Ignimbrite, with a precise sanidine/plagioclase 40Ar/39Ar age of 13.064 ± 0.065 Ma (~ Badenian/Sarmatian boundary in Central Paratethys chronology). It has distinctive glass geochemistry with wide compositional variations, which conforms with large-scale silicic explosive eruptions. In line with this, the calculated minimum volume (~ 200 km3) of the Dobi Ignimbrite is consistent with a high-end VEI 7 eruption, with possible ultradistal transport distance of over 300 km. Most of the pyroclastic succession, which erupted in two phases, was emplaced on land, as it contains leaves and tree trunks in the basal layer that we correlate with the Badenian/Sarmatian ‘volcanic floras’ of northern Hungary. At the same time, the ignimbrite has a strongly phreatomagmatic character, and, together with the presence of free-floating foraminifera, this suggest that the source vent was located in coastal waters of the Central Paratethys. These findings indicate either a late Badenian marine incursion prior to the eruption, or the shift of the eruption center toward the sea.