42 Paleozoic Events and Processes: Sedimentary Geology, Paleontology, and Geochemistry (Posters)

The focus of this session is short- to long-term geologic, paleobiologic, and geochemical events and processes, recorded in Paleozoic sedimentary rocks.

Tuesday, 24 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Assessing Climate Response Through Middle Permian Extinction Events in the Sydney Basin, Australia

Paper number: 42-12
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The Guadalupian epoch (Middle Permian) records two purported extinction events: the mid-Capitanian event (MCE; ~262 Ma) and end-Guadalupian event (EGE; ~259 Ma). Previous work highlights biological and ecological disruptions, particularly in the low paleolatitudes, but there remains debate on this event’s existence, severity, extent, and ultimate cause(s). This study combines paleoweathering proxies, carbon isotopic data, and sedimentology to assess the high-latitude response to these Guadalupian environmental crises. Drillcores from the Sydney Basin in NSW Australia extend through a near-continuous stratigraphic succession that shifts through time from marine to coastal plain depositional environments. The stratigraphic interval encompasses eastern Australian glacials P3 and P4 and coincides with local arc-related volcanism and the Emeishan Large Igneous Province. The chronostratigraphic framework is constrained through U-Pb CA-ID-TIMS dating of zircons in tuff beds. High-resolution Chemical Index of Alteration (CIA) paleoweathering records show stepwise shifts in the chemical weathering intensity, which are variably associated with carbon isotope shifts and carbon cycle perturbations. Baseline CIA values through the Guadalupian are relatively low (~65). Transient shifts to lower values through the P3 glacial coincide with a reduction in chemical weathering intensity expected during cooler climate conditions. A gradual shift to higher CIA values (~70) near the termination of the P3 glaciation corresponds to weathering intensification through the MCE. By contrast, δ13C values remain uniform, averaging -24‰ VPDB, indicating carbon cycle stability through the MCE. A return to lower CIA values (~65) is consistent with the onset of glacial P4. A subsequent shift to higher CIA values (80-85) through the Guadalupian-Lopingian boundary interval is matched by a 1‰ increase in δ13C values, recording complex relationships between chemical weathering intensity and shifts in the carbon cycle that align with the timing of the EGE. In overlying lower Lopingian strata, δ13C and CIA values stabilize to new baselines of ~-24.8‰ and 70-75, respectively.  In sum, the mid-Capitanian and end-Guadalupian events produced distinct, scale-dependent responses, with locally driven CIA weathering signals variably expressed relative to globally integrated δ¹³C carbon cycle records. Results highlight the complexity of Guadalupian environmental change and offer a high-latitude perspective that informs ongoing debate about the global significance and drivers of Guadalupian extinction events.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411225

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