Synchronicity between carbon cycle perturbation and the “Carnian Pluvial Event” in the Austrian Upper Triassic Polzberg using multi-proxy record

In the early Late Triassic, the Carnian Pluvial Event (CPE) marked a significant climatic shift characterized by increased rainfall, leading to major lithological changes in both continental and marine environments globally. This study investigates the correlation between carbon cycle perturbations and the CPE in the Upper Triassic Polzberg section in Austria using a multi-proxy approach. The CPE's climatic fluctuations, primarily driven by volcanic activity in the Wrangellia large igneous province, resulted in warmer and more humid conditions. These climatic changes are closely associated with a negative carbon isotope excursion, reflecting a global perturbation of the carbon cycle. The research site, located in Polzberg, northeast of Lunz am See, was analyzed bed-by-bed, utilizing both cores and outcrops. Carbonate carbon and oxygen isotopic analyses were conducted using mass spectrometry, ensuring high precision and reproducibility of δ18O and δ13C measurements. For δ13CTOC analysis, samples were treated with hydrochloric acid to remove carbonates, followed by combustion and chromatographic separation before mass spectrometric analysis. Scanning electron microscopy and carbonate petrography provided additional insights into the crystalline structure and origins of the carbonates, supporting the geochemical data. Previous studies have recorded a negative 2–4‰ δ13C shift, coinciding with similar features in other global records. We anticipate similar results from our analyses, which would further support the hypothesis of a global carbon cycle perturbation during the CPE. This expected isotopic shift reflects the significant changes in the isotopic composition of exchangeable carbon reservoirs, driven by the extensive volcanic activity that released large amounts of 13C-depleted CO2 into the atmosphere. This injection likely intensified Pangaean mega-monsoon activity, leading to increased rainfall, continental weathering, and erosion. The study also focuses on sedimentological changes in the Reifling Formation, Gostling Member, and Reingraben Shales, seeking evidence of synchronous occurrences with the carbon cycle perturbation. The integration of lithological, paleontological, and geochemical data aims to reconstruct the environmental conditions during the onset of the CPE. The research characterizes carbonate production in nearby platforms by distinguishing between pelagic and neritic sources, inferred from the abundance of calcareous nannofossils. These findings are expected to elucidate the contributions of different carbonate sources during this period. The increased rainfall and continental weathering associated with the CPE led to the transfer of large amounts of siliciclastics into marine basins. This influx of siliciclastics likely filled basins rapidly and triggered local anoxia due to the increased nutrient flux. The enhanced nutrient availability could have supported high primary productivity, which, coupled with restricted water circulation, may have led to oxygen depletion in bottom waters. These anoxic conditions would have further influenced the burial of organic carbon, contributing to the observed isotopic shifts. This research aims to provide a comprehensive dataset that enhances our understanding of the paleoclimate during the Carnian period. By integrating multiple proxies and detailed geochemical analyses, this study seeks to establish a reliable reference for future investigations into the Late Triassic environmental changes. The insights gained from this work will contribute to a deeper understanding of the complex interplay between volcanic activity, climate change, and biotic responses during this critical interval of Earth's history. The findings will have broader implications for understanding the drivers and consequences of climate change, both in the geological past and in the context of current and future climatic shifts.