Change from shallow to deep-water environment on an isolated carbonate platform in the Middle Triassic of the Transdanubian Range (Hungary)

The stratigraphic and paleoecologic investigations of the Middle Triassic K ' ad ' arta section of the western part of the Transdanubian Range (Hungary) let an insight to the drowning of an isolated carbonate platform and the deposition of the following pelagic successions in deep neritic and bathyal environment. The biostratigraphic and radiometric ages revealed the presence of a gap between the Pelsonian (Middle Anisian) shallow-marine carbonates and the overlying deep-water succession, since the onset of pelagic sedimentation was dated as late Illyrian (latest Anisian). This suggests that the study area was located on a relatively high paleotopographic position after the break-up of the Neotethys in the late Pelsonian. Correlation with other localities of the western Neotethys indicates that some sections were located either on rapidly subsiding blocks (e.g., Klisura - Dinarides, Schreierkogel - Northern Calcareous Alps, Baradla Cave - Aggtelek-Rudab ' anya Unit) or on more emerged highs (Rid - Dinarides). The integrated ammonoid and conodont biostratigraphy accompanied by U-Pb ages provided a good opportunity for correlations with Ladinian key sections (Bagolino, Monte San Giorgio, Rio Nigra) from the Southern Alps.

Automated summary

The study of the Middle Triassic K 'ad'arta section in the western Transdanubian Range of Hungary provides insights into the drowning of an isolated carbonate platform and the subsequent pelagic sedimentation. Biostratigraphic and radiometric ages reveal a gap between shallow-marine carbonates and deep-water successions, indicating the area's paleotopographic changes after the late Pelsonian period.