Simulation of Carbon Isotope Excursion Events at the Permian-Triassic Boundary Based on GEOCARB

The biggest Phanerozoic mass extinctionoccurred at the Permian-Triassic boundary and resulted in the loss of about 95% or more of all marine species. For quite some time, many kinds of abnormal environmental events were adopted to explain the abnormal reduction of carbon isotope at the Permian-Triassic boundary, however there still has not been a unified opinion. In this paper, based on the carbon cycle balance model of the earth under a long-period scale, the contributions of possible cataclysm events at the Permian-Triassic boundary to the carbon isotope records in carbonates were quantitatively simulated. The results proved that a single event, such as volcanism, terrestrial ecosystem collapse or another factor, was not strong enough to lead to the negative bias of carbon isotope at the Permian-Triassic boundary. Even though the release of methane hydrate can result in a comparably large negative excursion of inorganic carbon, this explanation becomes unsuitable when both the shifting Permian-Triassic boundary and the fluctuation record of other inorganic carbon isotopes in the early Triassic as a whole are considered. Therefore, it is suggested that the dynamic equilibrium between inorganic carbon reserves and organic carbon reserves was possibly disturbed by a superimposed effect of multiple events.