The pattern and timing of biotic recovery from the end-Permian mass extinction

Microfacies analysis and point counts of thin sections from 608 hand samples were used to track changes in the abun-dance and diversity of fossil grains through the extended re-covery interval following end-Permian mass extinction on the Great Bank of Guizhou (GBG)Ðan isolated Late Perm-ian to Late Triassic carbonate platform in south China. Ex-posure of a two-dimensional cross-section of the platform permits the comparison of faunal patterns along an envi-ronmental gradient from shallow to deep water. The diverse Late Permian biota was dominated by calcareous sponges, crinoids, articulate brachiopods, foraminifera, and calcar-eous algae. In contrast, Early Triassic communities were dominated by mollusks, with increasing abundance of cri-noids beginning in the Spathian. Increase in the diversity and abundance of fossils on the GBG was con®ned to a brief interval near the Spathian±Anisian boundary and concen-trated along the platform margin. Later Middle Triassic di-versi®cation, the return of calcareous algae and calcareous sponges, and the appearance of scleractinian corals did not substantially alter the mollusk-crinoid-Tubiphytes assem-blage before the end of the Middle Triassic. The low abun-dance of skeletal grains in Lower Triassic strata implies: (1) similarities in the relative contributions of micrite, micro-bialites, and oolites to Neoproterozoic carbonates result, at least in part, from the temporary removal of skeletal sinks for calcium carbonate; and (2) animals with hard skeletons remained at low abundance from the time of the end-Perm-ian extinction through much of the Early Triassic