CARBON-ISOTOPE AND IRIDIUM EVENT MARKERS NEAR THE PERMIAN TRIASSIC BOUNDARY IN THE MEISHAN SECTION, ZHEJIANG PROVINCE, CHINA

Systematic investigations for carbon isotopes and iridium of the Meishan section were carried out using very narrow sampling intervals. The high-resolution results demonstrate the following characteristics: (1) A large drop in deltaC-13 7 cm above the base of the Triassic with a magnitude of about 69 parts per thousand. (2) A sharp Ir peak of 2.02 ppb 10 cm above the base of the Triassic whereas the Ir mean of six samples equals 0.4 ppb. The large negative carbon-isotope shift, the Ir anomaly within a thin sublayer and microspherules all occur within a 20 cm thick section above the base of the Triassic which has been defined to coincide with an abrupt facies change from carbonate to clay. The geochemical results and the microspherules suggest that the Permian/Triassic boundary event was catastrophic and probably caused by an extraterrestrial impact.