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Severest crisis overlooked—Worst disruption of terrestrial environments postdates the Permian–Triassic mass extinction

机译:最严重的危机被忽略了—最糟糕的陆地环境破坏发生在二叠纪-三叠纪大灭绝之前

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摘要

Generally Early Triassic floras are believed to be depauperate, suffering from protracted recovery following the Permian–Triassic extinction event. Here we present palynological data of an expanded East Greenland section documenting recovered floras in the basal Triassic (Griesbachian) and a subsequent fundamental floral turnover, postdating the Permian–Triassic boundary extinction by about 500 kyrs. This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian. This turnover coincides with an extreme δ13Corg negative shift revealing a severe environmental crisis, probably induced by volcanic outbursts of the Siberian Traps, accompanied by a climatic turnover, changing from cool and dry in the Griesbachian to hot and humid in the Dienerian. Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years. Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis. Our results evidence the first profound disruption of the recovery of terrestrial environments about 500kyrs after the Permian–Triassic extinction event. It was followed by another crisis, about 1myrs later thus, the Early Triassic can be characterised as a time of successive environmental crises.
机译:通常,人们认为三叠纪早期植物区系已灭绝,二叠纪-三叠纪灭绝事件后恢复期延长。在这里,我们展示了扩大的东格陵兰部分的花粉数据,记录了基部三叠纪(格里斯巴赫)中已恢复的植物群以及随后的基本花卉更新,将二叠纪-三叠纪的边界灭绝推迟了约500秒。该事件的特征是主导花卉元素发生了互换,从格里斯巴赫(Griesbachian)的裸子植物花粉为主的协会转变为第纳尔(Dienerian)的以番茄红素孢子为主的组合。这一周转与一个极端的δ 13 Corg负移相吻合,揭示了一个严重的环境危机,可能是由西伯利亚圈套的火山爆发引起的,并伴随着气候周转,从格里斯巴赫山脉的干冷转变为高温和Dienerian潮湿。沉积速率的估计表明这种环境变化发生在大约1000多年之内。类似地,记录在北印度边缘(巴基斯坦)和鲍文盆地(澳大利亚)上的近代变化表明了这场危机的全球范围。我们的结果表明,在二叠纪-三叠纪灭绝事件发生之后,大约500凯尔的陆地环境恢复首次受到严重破坏。紧接着又是另一场危机,大约在1年后,因此三叠纪早期可被描述为连续不断的环境危机时期。

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