二叠纪-三叠纪野火间断事件对生物灭绝的响应——以浙江煤山剖面为例

Permian-Triassic Wildfire Gap Responses to the Mass Extinction-An Example Study in the Meishan Section,Zhejiang Province

二叠纪末期地球气候环境发生重大变化,导致陆地和海洋生态系统崩溃,发生了地质历史上最大规模的生物灭绝事件。大火(亦称野火)作为陆地生态系统的关键影响因子,以及气候环境变化的重要指标,在第四纪以前的历史研究中很少有报道。剖析了煤山二叠纪-三叠纪界线521 ka黑碳和燃烧源多环芳烃的沉积记录,恢复了生物灭绝前后的大火历史。研究显示,生物灭绝前的163 ka内大火频繁,在生物灭绝时则发生了最大规模的大火事件;生物灭绝线以上早三叠世地层中未发现燃烧的记录,出现了大火事件间断(时间持续约358 ka)。对比全球多个剖面,这种大火间断事件可能不是局部现象,而是全球性气候环境变化的响应。陆地植被为大火燃烧的原料,伴随着陆地植被的大规模消失和大气氧含量的快速下降,大火燃烧事件也将消失。因此,煤山剖面二叠纪-三叠纪界线的大火间断能用来指示生物的大规模灭绝事件。

Great changes occurred in the earth’s surrounding environments during the Permian-Triassic （P-Tr）transition and resulted in the collapse of land and marine ecosystems.Thus,the most severe mass extinction in the earth’s history appeared across the P-Tr boundary.Wildfire,as a key ecosystem driver and climate change indicator,is seldom reported in the documents of the pre-Quaternary researches.In this study,a 521 ka record of wildfire during the P-Tr mass extinction was recurred through the black car-bon （BC）and combustion-derived polycyclic aromatic hydrocarbons （PAHs）records in the GSSP section of Meishan.There were frequent wildfires in the 163 ka of history just before the P-Tr mass extinction and the most intensive one occurred in the mass extinction event beds.No combustion records were found in the beds above mass extinction line and a wildfire gap （lasting 358 ka）was recognized in the Early Trias-sic.Wildfire gap may be not a local phenomenon,but a response of global climatic and environmental changes.Wildfire would vanish accompanied by the destruction of land vegetation and abrupt drop of at-mospheric oxygen.Therefore,Meishan P-Tr wildfire gap can be used as an indicator of the mass extinction.