Radiometric dating of a tephra layer challenges the early Late Miocene biochronostratigraphy of Lake Pannon deposits

Establishing a chronostratigraphic framework for lacustrine sediments is a classic problem throughout Earth history, and pyroclastic deposits are essential for their correlation as they can provide numerical ages. Sediments of the Late Miocene–Pliocene brackish Lake Pannon in Central Europe accumulated over ~ 8 Ma, and a well-established biochronostratigraphic scheme using endemic biota has been developed and widely applied for their subdivision. Here, we describe a recently discovered unique tephra layer in the lacustrine succession from the Pécs–Danitzpuszta outcrop in SW Hungary, which, if found in other outcrops, can be an essential marker horizon in the region. Mineralogical and geochemical data suggest the Pásztori volcano, located 200 km to the north, as the most probable source of the tephra. Dating of the layer with several radiometric methods constrains the eruption to 11.3 ± 0.4 Ma, shortly after the beginning of the Pannonian age at ~ 11.6 Ma. This is slightly older than predicted by biostratigraphic considerations and challenges the accepted biochronostratigraphic system of Lake Pannon deposits. Here, we present an alternative calibration for the system, which should be tested by future investigations.