Two pulses of increasing terrestrial input to marine environment during the Permian–Triassic transition

The destruction of both terrestrial and marine ecosystems generally shows a process of rapid extinction followed by the wipe out of the Permian-type relics in the Permian–Triassic mass extinction, but the relationship between the terrestrial and marine ecosystem collapses is not clear until now. The terrestrial input from the land to marine system is an important link between them. Previous study has demonstrated a substantial increase of terrestrial influx to the marine water most likely corresponding to the Permian–Triassic mass extinction. Our new geochemical data from the Laolongdong section in the shallow marine carbonate platform of South China, reveal that the elevated terrestrial input nearby the Permian–Triassic Boundary (PTB) is actually marked by a two-pulse scenario. The first pulse represents a ~ 3- to ~ 6-fold increase of the terrestrial flux. The onset of the increase took place in the extinction horizon at the basal part of microbialites at Laolongdong, basically corresponding to Bed 24a of Meishan section and prior to the end-Permian mass extinction zenith; then the increase continued and spanned the extinction zenith. The second pulse is characterized a ~ 21- to ~ 35-fold increase in the terrestrial flux, equivalent to the widespread, abundant presence of mudstones in the earliest Triassic and roughly corresponding to the stage where the Permian-type survivors were thoroughly wiped out. A two-pulse terrestrial input is also clearly recorded at Cili, Shangsi and Meishan of South China, western Australia and Arctic Canada. Two episodes of the enhanced terrestrial input provide strong evidence for the devastation of the terrestrial ecosystem and insights into the reasonable explanation for the relationship between terrestrial and marine ecosystem collapses nearby the PTB.