AGE OF THE EMEISHAN FLOOD MAGMATISM AND RELATIONS TO PERMIAN-TRIASSIC BOUNDARY EVENTS

Abstract

The Permian–Triassic (P–T) mass extinction, the greatest biological mortality event in the Earth’s history, was probably caused by dramatic and global forcing mechanisms such as the Siberian flood volcanism. Here we present the first set of high-precision 40Ar/39Ar dating results of volcanic and intrusive rocks from the Emeishan Traps, South China, which define a main stage of the flood magmatism at ∼251–253 Ma and a subordinate precursory activity at ∼255 Ma. This time span is generally coeval with, or slightly older than, the age of the P–T boundary estimated by the ash beds in the Meishan stratotype section and the main eruption of the Siberian Traps. Our data reinforces the notion that the eruption of the Emeishan Traps, rather than eruption of the Siberian Traps, accounted for the formation of the P–T boundary ash beds in South China. The Emeishan flood magmatism, which occurred in the continental margin comprising thick marine limestone formations, moreover, may have triggered rapid release of large volumes of methane and carbon dioxide that could have been responsible for the global δ13C excursion and associated environmental crisis leading to the mass extinction at the P–T boundary.