252-11 Geochemical Proxy Records of Middle-Late Permian Environmental Change in the Sydney Basin, Australia

Session: Climate Transitions in the Paleozoic

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Abstract:

Proxy records of past environmental crises can help contextualize Earth system perturbations and their potential causes. Using sedimentology and paleoenvironmental proxies, this study aims to assess the high-latitude response to environmental crises through the mid-late Permian, including purported biocrises in the mid- (~262 Ma) and end-Guadalupian (~259 Ma), the end-Permian Event (~252 Ma), and eastern Australian glacial intervals P3 and P4. Drillcores from the Sydney Basin, NSW Australia extend through a near-continuous succession of strata that records marine to coastal plain depositional environments. U-Pb CA-IDTIMS dating of tuffaceous beds within these cores establishes a chronostratigraphic framework. High-resolution proxy records of paleoweathering from these cores, including the Chemical Index of Alteration (CIA), reveal stepwise shifts in the intensity of chemical weathering. Baseline CIA values through the Guadalupian are relatively low (~60-65). Transient shifts to lower values through the P3 and P4 glacial intervals is consistent with cooling and a reduction in chemical weathering.  A brief shift to higher CIA values near the termination of the P3 glaciation may correspond to warming associated with the mid-Guadalupian Event. Near the end of glacial P4 (top of the Guadalupian), CIA values show a sharp-based positive excursion to values of 80-85 that persists for c. 50m of section. This excursion, which coincides with the end-Guadalupian Event, is consistent with warming and enhanced chemical weathering. A new baseline with CIA values of 70-75 is established in overlying strata, suggesting a rebound to cooler climate conditions following an interval of rapid warming. A subsequent sharp excursion to CIA values of 85-90 corresponds to intensification of chemical weathering during the end-Permian Event. Carbon isotopic records show analogous changes, corroborating a record of abrupt climate shifts atop a long-term trend of warming climate. This study provides new paleoenvironmental proxies in an understudied region increasing the scope of available paleoclimate data through the mid-late Permian, allowing for a more robust record to contextualize environmental perturbations with respect to potential climate drivers.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6387

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