Calibrating the late Smithian (Early Triassic) crisis: New insights from the Nanpanjiang Basin, South China

The biotic recovery following the Permian/Triassic boundary mass extinction was influenced by several secondary extinctions during Early Triassic, of which late Smithian crisis is most severe known for some nekto-pelagic organisms such as ammonoids. Smithian-Spathian transition characterized successive global and environmental changes, including a dramatic positive carbon isotopic excursion, oceanic anoxia cooling event beginning in Smithian. However, tempo, modalities causal relationships among these various events remain poorly constrained. Here we synthesized paleontological, sedimentological, geochemical data from three sections (Motianling, Nafang, Shanggang) within Nanpanjiang Basin, representing platform slop to basinal deposits spanning Smithian/Spathian boundary. High-resolution analyses thin show sudden decrease richness abundance fossil grains at middle/upper all sections, coinciding with onset shift ?13Ccarb. It also slightly precedes cooling. At Shanggang, change dominance bivalve-rich ostracod-rich strata recorded Overall, our results therefore indicate that first major turnover happened rather than around Complementary on pyrite framboid size observed changes are concurrent oxygen depletion studied supporting hypothesis played an important role combination climate acidification.