The Norian Record of Climatic and Environmental Change in the Paleo-Antarctic

Late Triassic Norian records from high-latitude localities and the Paleo-Antarctic circle are extremely limited and relatively understudied. Here, we present new geochemical proxy data measured on samples representing fluvial-lacustrine sediments of the Parmeener Supergroup, Unit 4 from Tasmania, Australia, of Early-Mid Norian age (~216-223 Ma). These records offer a unique opportunity to reconstruct the Norian climate and environmental conditions close to the paleo-South Pole and during an interval of major global climatic and ecological condition transitions following the arid conditions of the Early–Middle Triassic and Carnian Pluvial Episode. The TOC values for these Norian age sediments were found to be generally low (0.1-4%). However, steep increases in the TOC values of up to 30-40% were observed, corresponding to the deposition of several coal seams. XRF and Hylogging data from this part of the core show a rapid increase in kaolinite, smectite, and other clay minerals, suggesting an elevated weathering pattern. Preliminary stable isotope results from this study show δ¹³C_org values varying from -27.5‰ to -23‰ (vs. VPDB). One steep negative δ¹³C_org excursion, with values reaching as low as -27.5‰, was observed in the upper part of the core. This negative excursion also coincides with the occurrence of two volcanic tuff layers, likely from the proto-Pacific convergent margin along the Antarctic Peninsula. Previous studies of cores from nearby localities have dated stratigraphically equivalent tuffs to 217.84±0.19 Ma (Calver et al. 2021; DOI: 10.1080/08120099.2021.1888804). Hg/TOC values also show a relative increase associated with the volcanics. δ¹³C_org data from the core is comparable to other global records (e.g. Sakahogi, Japan;  Pignola-Abriola, Italy; and Kennecott Point, British Columbia), which show similar trends of δ¹³C_org profile, though somewhat lighter values for the Norian.

This multiproxy analysis from Tasmania provides a distinctive and continuous record of climate change in the high-latitude Southern Hemisphere during the Norian, shedding light on the significant climatic and environmental changes that occurred during this time.