Three Middle Anisian carbonate platforms (Barnag, Tagyon and Kádárta Platforms) surrounded
by the hemipelagic Felsőörs Basin have been reconstructed in the Balaton Highland.
The truncated surface of all platforms is covered by basinal carbonates and volcanic
rocks of the Vászoly Formation. Based on conodont investigations these platforms were
subject to drowning at different times. The earliest drowning was recognized in the
late Pelsonian on the southern edge of the Barnag Platform (Paragondolella bulgarica
Zone). This date correlates well with the opening of a neptunian dyke encountered
near the southwestern margin of the Kádárta Platform and also with the age of the
dykes cutting through Pelsonian platforms in the Northern Calcareous Alps, Aggtelek
Hills, Dinarides and Dolomites. Drowning of the Tagyon Platform and the marginal area
of the Kádárta Platform occurred in the early Illyrian (Paragondolella bifurcata and
Neogondolella constricta Zones). However, the Kádárta Platform shows a trend of decreasing
age for the timing of the drowning from the edge towards the inner parts of the platform
during the late Illyrian. This can be explained by tectonically forced backstepping
of the downfaulted marginal blocks and/or by eustatic sea-level rise accompanied by
increasing volcanic activity that may have caused the decrease of transparency of
the sea-water. Later on, as a result of intensifying sea level rise bathyal environment
formed during the Ladinian that can be confirmed by the appearance and increasing
dominance of deep-water ‘psychrosphaeric’ forms in the ostracod assemblage.
