The demise of an icehouse: Calibrating the end of the LPIA

Earth has experienced three complete icehouse-greenhouse turnovers in the Phanerozoic, with the Late Paleozoic Ice Age (LPIA) recognized as the last and most extreme icehouse. The nature, scale and dynamics of the LPIA are characterized by periods of intense glaciation, which are often interrupted by short-lived (1–2 Myrs) intervals associated with ice-free or distal from ice conditions. In this study, we focus on constraining the icehouse-greenhouse turnover across southcentral Gondwana (SCG) reporting new high-resolution UPb zircon CA-ID-TIMS ages from immediate postglacial facies in the Kalahari and Karoo basins. We integrate these ages with published UPb zircon CA-ID-TIMS ages (n = 20) to build a stratigraphic framework for SCG, to investigate the duration and nature of the demise of the LPIA. We confirm the stepwise deglaciation of Gondwana over a ca. 20 Myr period, with deglaciation occurring first in the Paraná Basin at ca. 300 Ma and in the Karoo Basin by 282 Ma. Low-latitude marine carbonates deposited contemporaneously with the final demise of ice is characterized by a major shift towards isotopically depleted δ¹³C and δ¹⁸O values. We interpret the perturbations in stable isotopes records to be driven by either mantle outgassing or the release of methane and the addition of glacial melt water to the paleo-ocean during warming. The presented stratigraphic framework is built in intracratonic basins, far from any syn- tectonic affects, suggesting a largely climatic driver behind deglaciation events.