Atlantic cooling associated with a marine biotic crisis during the mid-Cretaceous period
Atlantic cooling associated with a marine biotic crisis during the mid-Cretaceous period
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DOI：
10.1038/ngeo1850
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发表时间：
2013-07-01
影响因子：
18.3
通讯作者：
Wagner, T.
中科院分区：
文献类型：
--
作者：
McAnena, A.;Floegel, S.;Wagner, T.
在炎热的中生代发生的大多数海洋生物危机都与极端温暖的时期有关(1，2)。然而，其他的可能发生在白垩纪温室变暖中断的较凉爽的时间段(3-5)。在阿普提亚晚期(6-8)(116-114Myr前)有一些冷却的迹象，但还没有确定地与生物危机有关。在这里，我们使用一套来自北大西洋海洋沉积物岩心的地球化学和微古生物学评估以及全球生物地球化学模拟来评估阿普提亚晚期冷却的时间和规模及其与生物危机的关系。从TEX86替代数据得出的海洋表面温度表明，在200万年的时间里，表层海水冷却了约5摄氏度，与碳酸盐和有机碳中约千分之二的正增量C-13漂移一致。在此期间，表层生产力得到了提高，但浮游有孔虫和超微锥浮游植物的丰度有所下降。我们用生物地球化学模型进行的模拟表明，与冷却相关的增量C-13漂移可以通过250万年来埋藏约812,000亿吨碳来解释。大约50%的碳埋藏发生在大西洋、南部和特提斯洋盆。我们的结论是，温室条件下的全球变冷可能会对海洋生态系统和生物地球化学循环造成扰动，其规模可与全球变暖相媲美。
Most of the marine biotic crises that occurred during the hot Mesozoic era have been linked to episodes of extreme warmth(1,2). Others, however, may have occurred during cooler intervals that interrupted Cretaceous greenhouse warmth(3-5). There are some indications of cooling in the late Aptian(6-8) (116-114 Myr ago), but it has not been definitively linked to biotic crisis. Here we assess the timing and magnitude of late Aptian cooling and its association with biotic crises using a suite of geochemical and micropalaeontological assessments from a marine sediment core from the North Atlantic Ocean as well as global biogeochemical modelling. Sea surface temperatures derived from the TEX86 proxy suggest that surface waters cooled by about 5 degrees C during the two million years, coincident with a positive delta C-13 excursion of approximately 2 parts per thousand in carbonates and organic carbon. Surface productivity was enhanced during this period, but the abundance of planktonic foraminifera and nannoconid phytoplankton declined. Our simulations with a biogeochemical model indicate that the delta C-13 excursion associated with the cooling could be explained by the burial of about 812,000 gigatons of carbon over 2.5 million years. About 50% of the this carbon burial occurred in the Atlantic, Southern and Tethys ocean basins. We conclude that global cooling during greenhouse conditions can cause perturbations to marine ecosystems and biogeochemical cycles at scales comparable to those associated with globalwarming.