Restoration of reef ecosystems following the Guadalupian-Lopingian boundary mass extinction: Evidence from the Laibin area, South China

The Guadalupian-Lopingian boundary (GLB), also Middle-Late Permian boundary, mass extinction severely destroyed metazoan reef ecosystems, although some studies argued that both biotic and environmental turnover across the GLB are not so obvious. When compared with prolifically developed reefs in the Capitanian, the Wuchiapingian reef examples appear depauperate and almost 89% of the carbonate production in these bio-constructions was lost. Here, we report a typical sponge reef from the Wuchiapingian stage in the Tieqiao section, central Guangxi Province, South China. The Tiegiao reef might represent the only example of a Wuchiapingian metazoan reef in the eastern Palaeo-Tethys region. It provides insight into ecosystem restoration following the GLB extinction. Major constructors of the Tiegiao reef are sponges (Peronidella, Parauvanella, Sollasia, Tabulozoa, and Amblysiphonella), algae (Anthracoporella, Archaeolithporella, Permocalculus, Gymnocodium) and Tubiphytes. This reef is well constrained as middle-late Wuchiapingian in age by the Clarkina orientalis conodont zone. Carbonate carbon isotope excursions experienced negative spikes near the GLB and multiple perturbations in the early-middle Wuchiapingian, and remained relatively stable during re-establishment of metazoan reefs in middle-late Wuchiapingian. Conodont oxygen isotopes showed that the sea surface temperature (SST) was extremely high, > 30 degrees C during late Capitanian time, punctuated by a short cooling event and global regression associated with the GLB extinction, and followed by high SST and rapid rise in sea level in the early Wuchiapingian. The reemergence of the Tiegiao reef coincided with the initial cooling in surface oceans and sea-level fall during the middle-late Wuchiapingian. Accordingly, reef ecosystems experienced a long-term depletion worldwide in early-middle Wuchiapingian time and then recovered similar to 2.5 Myr after the GLB extinction based on estimate in integration of both conodont biostratigraphy and radiometric ages.