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

Viktor Karádi,Attila Vörös,Emőke Tóth,Tamás Budai,Olga Piros,István Dunkl,János Haas

doi:10.1016/j.palaeo.2021.110793

Abstract

The stratigraphic and paleoecologic investigations of the Middle Triassic Kádárta 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-Rudabánya Unit) or on more emerged highs (Rid – Dinarides). The integrated ammonoid and conodont biostratigraphy accompanied by UPb ages provided a good opportunity for correlations with Ladinian key sections (Bagolino, Monte San Giorgio, Rio Nigra) from the Southern Alps.

Highlights

During the Middle Anisian the passive margin of the western Neo tethys was affected by extensional tectonic activity due to the westward opening of the ocean (Bertotti et al, 1993; Gaetani, 2010; Gawlick et al, 2012, 2021 and further references therein)
The aim of the present study is to investigate the development of the depositional regime of an emerged horst from the middle Anisian to the late Ladinian based on the recently exposed section in the Kadarta quarry
Accurate correlations of the Kadarta section with other successions from various regions of the western Neothetys are performed through ammonoid and conodont biostratigraphy supple mented with zircon U–Pb geochronology, and ostracod paleoecology is used for comparison of the depositional environments of different

Summary

Introduction

During the Middle Anisian the passive margin of the western Neo tethys was affected by extensional tectonic activity due to the westward opening of the ocean (Bertotti et al, 1993; Gaetani, 2010; Gawlick et al, 2012, 2021 and further references therein). With the overall flooding of these horsts in the middle-late Illyrian (Late Anisian) (Gawlick et al, 2021) deep-marine depositional environment domi nated in large part of the Alpine region of the western Tethys shelf during the Ladinian. The aim of the present study is to investigate the development of the depositional regime of an emerged horst from the middle Anisian to the late Ladinian based on the recently exposed section in the Kadarta quarry. Accurate correlations of the Kadarta section with other successions from various regions of the western Neothetys are performed through ammonoid and conodont biostratigraphy supple mented with zircon U–Pb geochronology, and ostracod paleoecology is used for comparison of the depositional environments of different

Objectives

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Discussion

Conclusion