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A two-phased end-triassic mass extinction
Earth-Science Reviews ( IF 12.1 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.earscirev.2020.103282
Paul B. Wignall , Jed W. Atkinson

Abstract The end-Triassic mass extinction was one of the big five crises of the fossil record. It affected diverse marine groups, including bivalves, brachiopods, ostracods, calcareous algae, radiolarians, and tetrapods and coincided with major changes in palynological assemblages. The rapidity of the event has long been debated and here we show that it can be resolved into two distinct, short-lived extinction pulses separated by a several hundred-thousand-year interlude phase. Detailed collecting in the British Isles shows the first extinction in the lower Cotham Member eliminated many bivalves and ostracods. This event has been previously considered as the end-Triassic mass extinction horizon, however a second extinction is also seen at the top of the Langport Member after a phase of recovery marked by diversity increase. This younger crisis caused the loss of further bivalves, ostracods and the last of the conodonts. The two phases of marine extinctions coincide with marked turnovers amongst palynofloral assemblages with the interlude phase manifest as a fern spore-dominated interval (the Polypodiisporites polymicroforatus abundance interval). Correlation of Triassic-Jurassic boundary sections (and their associated extinction record) in Europe has been controversial. The most parsimonious correlation scheme assumes that a brief, high amplitude negative excursion of δ13Corg values, seen at the level of the first extinction phase in the UK, is manifest in other European sections in the same way. Alternative correlation schemes require complex scenarios with extinction occurring in some areas as recovery is happening elsewhere. In Europe, the first extinction coincides with regression whilst the second occurs at a flooding surface marked by the spread of anoxia. The extinction history of the terminal Triassic crisis is remarkably similar to that seen during other extinction events (end-Ordovician, Permo-Triassic, Toarcian) and suggests that, if the ultimate driver of these crises – large igneous province eruptions – is the same, then they show the same “double-punch” eruption history separated by a more benign interval of a few hundred-thousand-year duration.

中文翻译:

一个两阶段的三叠纪末大灭绝

摘要 三叠纪末生物大灭绝是化石记录的五大危机之一。它影响了不同的海洋群体,包括双壳类、腕足类、介形类、钙质藻类、放射虫和四足类,同时也发生了孢粉组合的重大变化。该事件的快速性长期以来一直存在争议,在这里我们表明它可以分解为两个不同的、短暂的灭绝脉冲,由数十万年的间断阶段隔开。在不列颠群岛的详细收集表明,科塔姆下游的第一次灭绝消灭了许多双壳类动物和介形动物。这一事件以前被认为是三叠纪末大灭绝地平线,但是在以多样性增加为标志的恢复阶段之后,在朗波特段的顶部也看到了第二次灭绝。这场较年轻的危机导致更多的双壳类动物、介形动物和最后的牙形动物丧失。海洋灭绝的两个阶段与孢粉花组合之间的显着转变相吻合,中间阶段表现为蕨类孢子占主导地位的区间(Polypodiisporites polymicroforatus 丰度区间)。欧洲三叠纪-侏罗纪边界剖面(及其相关的灭绝记录)的相关性一直存在争议。最简约的相关方案假设 δ13Corg 值的短暂、高振幅负偏移,在英国第一次灭绝阶段的水平上看到,在其他欧洲部分也以相同的方式表现出来。替代相关方案需要复杂的场景,随着其他地方的恢复正在发生,某些地区会发生灭绝。在欧洲,第一次灭绝与回归同时发生,而第二次则发生在以缺氧蔓延为标志的泛滥表面。三叠纪末期危机的灭绝历史与其他灭绝事件(奥陶纪末、二叠纪-三叠纪、托阿尔纪)的灭绝历史非常相似,并表明,如果这些危机的最终驱动因素——大型火成岩省喷发——是相同的,然后它们显示出相同的“双冲”喷发历史,中间间隔了几十万年的更温和的间隔。
更新日期:2020-09-01
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