A deep-water Rencunping sequence response to astronomical forcing during the late Permian in South China

The timing of the end-Permian mass extinction can be established from astronomically controlled climate cycles recorded in continuous marine sedimentary sections. The high-resolution cyclostratigraphic analysis is carried out on the deep-water Permian-Triassic boundary (PTB) sequence at the Rencunping section, Sangzhi County, South China. Physical and chemical proxy records reveal the presence of the complete suite of orbital frequencies in the Milankovitch bands, providing strong evidence for 405-kyr and 100-kyr eccentricity forcing throughout the Permian-Triassic boundary intervals. Floating astronomical time scales (ATS) are established for the discussion and comparison on the late Permian mass extinction and crisis between deep-water and shallow-water sections. Here we estimate durations of 2268 kyr for Changhsingian stage, 609 kyr for the Changhsingian conodont Clarkina yini Zone, and 1316 kyr for the ammonoid Pseudotirolites-Rotodiscoceras Zone, based on 405-kyr astronomical eccentricity tuning. Previous studies revealed that the biotic and environmental depletion began in deep waters earlier than the crisis in shallow waters. This study suggests that the extinction and environmental deterioration in deep waters started at least about 270 kyr before the PTB and 66–101 kyr earlier than the counterpart in shallow water. The deterioration is primarily explained as associated with frequent volcanism and its induced cascade of negative environmental and ecological effects. The volcanism was triggered by the subduction of Paleotethyan Ocean in South China.