Cerium isotope evidence for rapid redox shifts in shallow marine environments across the end-Permian mass extinction

The expansion of marine anoxia is widely regarded as a proximate driver of the end-Permian mass extinction (EPME, ca. 251.94 Ma). While the expansion of marine anoxia in deep waters prior to the EPME is well documented, redox evolution in shallow marine environments is less understood. We present the first paired cerium isotope (δ142Ce) and cerium anomaly (Ce/Ce*) records from shallow-marine carbonates in southern China, providing new insights into shallow-marine redox dynamics across the EPME in the eastern Paleo-Tethys Ocean. Our data show that, in the latest Changhsingian, δ142Ce values remained relatively stable at high values, indicating well-oxygenated, near-modern shallow marine conditions. A notable negative excursion in δ142Ce signals a rapid onset of shallow-water anoxia immediately prior to the major pulse of the EPME at the nadir of δ13Ccarb. Comparison of our δ142Ce data with published δ238U records reveals that the initiation of shallow-water anoxia lagged behind deep-water anoxia by 40 k.y. and extended into the earliest Triassic. By correlating these redox transitions with high-resolution biodiversity data spanning 1 m.y. across the EPME, we demonstrate that the expansion of shallow and deep anoxia, respectively, contribuited to the extinction of benthic and planktonic faunas and the untimate collapse of ecosystems in the Permian−Triassic oceans.