Extreme continental weathering in the northwestern Tethys during the end-Triassic mass extinction

Tetsuji Onoue, Jozef Michalík, Hideko Shirozu, Misa Yamashita, Katsuyuki Yamashita, Soichiro Kusaka, Katsuhito Soda

Research output: Contribution to journalArticlepeer-review

Abstract

The end-Triassic mass extinction (ETE) is thought to have been triggered by widespread eruption and emissions of volcanic and contact metamorphic carbon and sulfur gases from the Central Atlantic Magmatic Province (CAMP) flood basalts. Although palynological studies of shallow marine deposits in the basins of Denmark and Germany suggest that deforestation and catastrophic soil loss occurred during the CAMP volcanism and ETE interval, the intensity and timing of continental weathering in the region of northwestern Tethys Ocean remain unclear. Here we present Sr, C, and O isotope data, as well as multivariate statistical analyses of major element contents, for carbonate–clastic deposits in the Kardolína section, Slovakia, to develop a continental weathering record in the NW Tethys during the ETE event. This section consists of a shallow marine carbonate sequence in the Rhaetian Fatra Formation and the overlying Hettangian Kopieniec Formation. The Fatra Formation represents ramp facies deposits that formed in a restricted pull-apart basin of the Fatric Zone along the southern margin of the Bohemian Massif in the region of northwestern Tethys. Carbon isotope analysis of the limestones revealed two negative carbon isotope excursions (NCIEs) in the uppermost Fatra Formation. These two NCIEs occurred in the latest Rhaetian and can be compared to the “precursor” and “initial” NCIEs reported for the northwestern Tethys. Strontium isotope analysis of the limestones revealed an abrupt increase in Sr isotope ratios between the precursor and initial NCIEs, which indicates that continental weathering of the Bohemian Massif increased rapidly in the latest Rhaetian. Multivariate analysis of major element contents in the carbonate rocks also shows that intense chemical weathering of the hinterland was accelerated after the precursor NCIE, supporting the inferences drawn from Sr isotopes. Furthermore, our study reveals that the carbonate depositional environments of the Fatra Formation changed to the formation of specific Fe-rich oolites with increased continental weathering after the precursor NCIE. The concentrations of redox-sensitive major elements (e.g., Mn and Fe) and multivariate analysis of the major element data suggest that the Fe-rich oolites were formed by an influx of O-depleted water into the shallow water depositional environment of the Fatra Formation. A possible origin for this O-depleted water is the oxygen minimum zone (OMZ) that formed at intermediate water depths in European basins (e.g., the German and Eiberg basins) during the latest Rhaetian. Our results suggest that the marine environment in the European basins may have developed an OMZ due to the increase in continental weathering during the latest Rhaetian, and these environmental changes may have had an important role in the marine ETE event.

Original languageEnglish
Article number110934
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume594
DOIs
Publication statusPublished - May 15 2022

Keywords

  • C isotopes
  • Multivariate analysis
  • Rhaetian
  • Slovakia
  • Sr isotopes
  • Triassic–Jurassic boundary

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

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