Carbon Cycle Perturbation from the middle Permian to Late Triassic - A Southern Hemisphere Perspective

Abstract

The middle Permian to Late Triassic was subject to major disturbances to the global carbon cycle, associated with the emplacement of several large igneous provinces (LIPs) and an extraterrestrial bolide impact. These perturbations are recorded in the carbon-isotope composition of terrestrial and marine organic matter and carbonate as carbon-isotope excursions. Glacio-marine middle Permian and terrestrial Late Triassic (Carnian to Norian) sediments, deposited in the Paleo-Antarctic Circle (paleo-latitudes of 78° to 69°S, respectively), show records of significant carbon cycle and environmental perturbations. Evidence of these anomalies is presented through a high-resolution study involving sedimentology and stratigraphy, organic carbon isotope (δ13CTOC), and additional geochemical analyses combined with geochronological and palynological data, across the middle Permian to Upper Triassic successions recovered from the BIC-5 core (300 m) in eastern Tasmania, Australia. Significant differences in depositional environments, climate, and the carbon cycle are evident through the successions, and three distinct carbon isotope excursions (CIEs), characterized by negative shifts of up to -6‰ were identified; the Late Permian Guadalupian Carbon Isotope Excursion (G-CIE), the Carnian Pluvial Event (CPE), and the middle Norian Event (MNE). These excursions correspond to other δ 13CTOC records from the paleo-Pacific Ocean (Panthalassa), Southwest England, and South China, highlighting the global and precisely polar record of the Carnian Pluvial Event and the middle Norian Event, which are typically poorly documented in the Southern Hemisphere. Analyses of some elemental proxy ratios and mercury reveal the relationship between carbon cycle perturbations and the resulting environmental response in marine and continental regions as well as the possible cause of the carbon cycle perturbation within the paleo-Antarctic circle. This study provides new evidence from the Southern Hemisphere that reveals the global nature of the events.

Date of Award	19 Dec 2023
Original language	American English
Supervisor	Aisha Alsuwaidi (Supervisor)