ASTROCHRONOLOGY OF THE ANISIAN STAGE (MIDDLE TRIASSIC) IN SOUTH CHINA: IMPLICATIONS FOR BIOTIC RECOVERY FOLLOWING THE END-PERMIAN MASS EXTINCTION

High-precision age modeling of the Early-Middle Triassic is the key to understanding the nature and pattern of biotic recovery following the end-Permian mass extinction. In a new contribution we present high-resolution gamma ray (GR) and magnetic susceptibility (MS) series of the Anisian stage at Guandao section in Guizhou, South China. GR and MS variations show Milankovitch signals that support the prediction of astronomical solutions. Astronomical tuning of the GR and MS series to interpreted 405-kyr long orbital eccentricity cycles yields a 5.6 Myr astrochronology for the Anisian Stage. Together with a previous Early Triassic astrochronology study in South China, this provides a continuous 11 Myr timescale for repeated biotic crisis and recovery after the end-Permian dying. This new timescale enables us to examine the rates of biotic evolution during the Early-Middle Triassic and provides time constraints for other key geological events, including global sea-level change, marine carbon isotope excursions, and the geomagnetic polarity timescale.