THE EARLY-TRIASSIC NITROGEN CYCLE AND MARINE ECOSYSTEM RECOVERY AS SEEN IN CHAOHU, ANHUI PROVINCE, SOUTH CHINA

The Early Triassic is characterized by the most protracted marine ecosystem recovery of the Phanerozoic, following the earth’s most severe biotic crisis, the end-Permian mass extinction. The delayed recovery has been attributed to repeated episodes of climatic warming—which triggered terrestrial weathering, increased primary productivity and reducing conditions. The aim of this study is to track the recovery of nutrient cycling and primary productivity in the first 5 Myr following the end-Permian biotic crisis, through analysis of sections in Chaohu, Anhui Province, South China. We obtained samples from two primary locations: West Pingdingshan (which is the global stratotype section for the Induan-Olenekian boundary) and South Majiashan. These sections were deposited in a deep ramp setting, are stratigraphically continuous, easily accessible, and can provide high resolution chronology. West Pingdingshan spans from immediately prior to the Permian-Triassic boundary to the Induan-Olenekian boundary, and mostly consists of shale with thinly interbedded mudstone. South Majiashan spans from the Smithian to the Spathian, and is characterized by massive mudstone. Nitrogen isotope ratios of sedimentary organic matter can provide key information about changes in nitrogen cycling and the degree of nitrogen limitation experienced by marine environments. Similarly, trace element proxies can provide information on redox conditions, primary productivity, and biogeochemical cycling—all of which point to the nature of marine ecosystem recovery following the mass extinction. We used isotope ratio mass spectrometry to analyze organic N isotopes and X-ray fluorescence spectroscopy (XRF) for analysis of the productivity-sensitive elements Ba and P. Our results will provide new insights into nutrient cycling on the South China craton and nature of environmental perturbations that characterized the Early Triassic.