【摘要】 重庆凉风垭二叠-三叠系界线剖面64个碳酸盐样品碳同位素值测试结果显示,在界线附近碳同位素值出现3次负异常,第1次负异常出现在第37层,考虑到该层是灰岩透镜体与黏土岩的混合层,此次异常有待进一步验证;第2次负异常出现在第40层,此次异常是δ(13C)值偏移幅度最大的1次(1.5‰),在该层大量生物灭绝;第3次负异常出现在第44层。凉风垭界线剖面碳同位素值的3次负异常与生物变化的对比表明,碳循环的多次变化与生物危机相伴,生物危机期间环境处于不稳定状态。更多还原

【Abstract】 Great progress has been made on bio-stratigraphy in the Liangfengya Permian-Triassic boundary section,but very few studies focus upon high-resolution carbon isotope.The results of δ13Ccarb analysis of 64 samples show that there are two or three negative excursions near the PTB.This reflects several variations of carbon cycle with biotic crisis.The first shift that needs further validation is in the 37 bed,because the sediments are mixed by clay and lens limestone;the second where most organisms died out is in the 40 bed;the third is in the 44 bed.The rapid drop of the sea level in the Late Permian caused the oxidation of a great amount of sedimentary organic carbon,leading to the primary productivity reduction and decrease of burial carbon.This broke the carbon cycle and gave rise to several negative excursions of the carbon isotope,which reflected the instability of environment during the life crisis period.更多还原