Cause of Upper Triassic climate crisis revealed by Re–Os geochemistry of Boreal black shales
Cause of Upper Triassic climate crisis revealed by Re–Os geochemistry of Boreal black shales
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DOI：
10.1016/j.palaeo.2013.12.027
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发表时间：
2014-02
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影响因子：
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通讯作者：
Guangping Xu;J. Hannah;H. Stein;A. Mørk;J. Vigran;B. Bingen;D. Schutt;B. A. Lundschien
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文献类型：
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作者：
Guangping Xu;J. Hannah;H. Stein;A. Mørk;J. Vigran;B. Bingen;D. Schutt;B. A. Lundschien
三叠纪被两次显生目动物大灭绝所包围。尽管长期以来一直被视为气候稳定的时期，但新出现的数据表明，气候出现了多次波动，至少出现了一次严重的生态危机。将这些气候不稳定与可能的原因联系起来，是因为三叠纪时间尺度内的年龄控制不力。在这里，我们提出了横跨中上三叠统阶段界线的页岩剖面的新的Re-Os年龄。拉丁纪顶部和底部的名义Re-Os等时线年龄分别为236.6 Ma和239.3 Ma，将绝对时间纳入有争议的三叠纪时间范围，并将晚三叠世的开始时间定为12 Ma左右。比之前分配的时间要早。上拉丁纪页岩的初始187Os/188Os显著减少，记录了来自Wrangellian洪水玄武岩的输入，后者是卡尼亚(晚三叠世)洪水事件的起始者，并伴随着关键化石群(如恐龙和钙质纳米浮游生物)的辐射。在Re-Os地质年代学的基础上，提出了安尼辛-拉丁-卡尼期界线的绝对时间标度。
The Triassic Period is bracketed by two of the ‘big five’ Phanerozoic mass extinctions. Though long viewed as a period of climatic stability, emerging data suggest multiple climatic swings and at least one severe ecological crisis. Linking these climatic instabilities with probable causes is hampered by poor age control within the Triassic time scale. Here we present new Re–Os ages for shale sections straddling Middle–Upper Triassic stage boundaries. Nominal Re–Os isochron ages of 236.6 and 239.3 Ma for the top and base of the Ladinian (upper Middle Triassic) bring absolute time into the contentious Triassic time scale, and place the beginning of the Late Triassic about 12 m.y. earlier than previously assigned. A marked decrease in initial187Os/188Os in Upper Ladinian shale records input from Wrangellian flood basalts — an instigator in the Carnian (Late Triassic) Pluvial Event and accompanying radiation of key fossil groups (e.g., dinosaurs and calcareous nanoplankton). An absolute time scale is proposed for the Anisian–Ladinian–Carnian boundaries based on Re–Os geochronology.