252-10 Permian Persistence of the late Paleozoic Ice Age in eastern Australia

Session: Climate Transitions in the Paleozoic

Presenting Author:

Authors:

Abstract:

The increasingly popular view as to the close of the late Paleozoic Ice Age is that it coincides with the “Artinskian Warming Event” (AWE). Nonetheless, records of glacial and cold conditions persist beyond that time, notably in eastern Australia. There, the P2 glaciation (287-280 Ma) is recorded by ice-proximal marine proglacial diamictites and preserves evidence for isostatic loading of the shallow marine seafloor. This event is also recorded in Western Australia and southern Africa. Following a lengthy nonglacial interval, the P3 (270.5 – 262 Ma) and P4 (260-254.5 Ma) glaciations are recorded by mainly glaciomarine, mixed sand/mudstones with dispersed gravel and glendonites. P3 and P4 are recorded only in eastern Australia, and possibly in Siberia. Modified clast shapes (bullet, striated, faceted), gravel and sand clusters, and punctured lamination (dropstone textures) attest to glacial influence on sediment transport and deposition. Some clasts reach >2 m in diameter, and most are composed of crystalline basement lithologies from outside the basin. Most of these lithologies are fossiliferous, preserving both body and trace fossils of marine origin. Whereas the P3 is recorded by thick (<100s of m), continuous intervals of glaciomarine lithologies, P4 is manifested as a series of thinner stratal intervals (<10s of m) separated by intervals with no evidence of glacial conditions or cold climate. Following the end of P4 at 254.5 Ma, climate remained cool until approximately 253 Ma when there was a gradual warming, leading up to the end-Permian crisis.

Glaciations P2-P4 are recorded in all eastern Australian basins, spanning paleolatitudes from 45 to 75 degrees south (north Queensland to Tasmania). Whereas evidence suggests that glacier termini were proximal to marine basins during P2, a lack of proximal proglacial or glacial facies in P3 and P4 suggests that glaciers were confined to mountainous topography outside the basins during those times, and/or that frigid conditions allowed formation of sea/shore ice and rafting of debris into the marine environment. Processes responsible for beginning and ending post-AWE glaciations are still debated. A range of sedimentological and geochemical proxy records point to complex interplay among volcanically-derived greenhouse gas emissions, variable rates of carbon sequestration via chemical weathering of silicate minerals, and storage of organic carbon in coal-bearing successions and marine shales.

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

doi: 10.1130/abs/2025AM-6895

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.