A case for a comet impact trigger for the Paleocene/Eocene thermal maximum and carbon isotope excursion
A case for a comet impact trigger for the Paleocene/Eocene thermal maximum and carbon isotope excursion
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DOI：
10.1016/s0012-821x(03)00188-2
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发表时间：
2003-06-15
影响因子：
5.3
通讯作者：
Van der Voo, R
中科院分区：
文献类型：
--
作者：
Kent, DV;Cramer, BS;Van der Voo, R
我们假设古新世/始新世边界（类似于 55 Ma）碳同位素偏移（CIE）的快速发生可能是由于类似 10 公里彗星的撞击而积累了大量富含 C-12 的碳，这一事件也将引发温室变暖，导致古新世/始新世热最大值，并可能导致海底甲烷水合物的热解离。影响的间接证据是富含高岭石的陆架沉积物中异常丰富的磁性纳米粒子，这些沉积物与大西洋海岸平原三个钻探点的 CIE 的开始和最低点密切相关。在考虑了可能产生磁性纳米粒子组合的各种替代机制之后，并通过与报道的白垩纪/第三纪边界处富铁纳米相材料的检测进行类比，我们认为 CIE 的发生源于撞击羽流凝结物。因此，高岭石的突然增加被认为代表快速风化的撞击喷射尘埃覆盖层在海洋架上的重新沉积。已发表的关于古新世/始新世边界处或附近存在小型但重要的铱异常的报告为撞击提供了支持证据。 (C) 2003 Elsevier Science B.V. 保留所有权利。
We hypothesize that the rapid onset of the carbon isotope excursion (CIE) at the Paleocene/Eocene boundary (similar to55 Ma) may have resulted from the accretion of a significant amount of C-12-enriched carbon from the impact of a similar to10 km comet, an event that would also trigger greenhouse warming leading to the Paleocene/Eocene thermal maximum and, possibly, thermal dissociation of seafloor methane hydrate. Indirect evidence of an impact is the unusual abundance of magnetic nanoparticles in kaolinite-rich shelf sediments that closely coincide with the onset and nadir of the CIE at three drill sites on the Atlantic Coastal Plain. After considering various alternative mechanisms that could have produced the magnetic nanoparticle assemblage and by analogy with the reported detection of iron-rich nanophase material at the Cretaceous/Tertiary boundary, we suggest that the CIE occurrence was derived from an impact plume condensate. The sudden increase in kaolinite is thus thought to represent the redeposition on the marine shelf of a rapidly weathered impact ejecta dust blanket. Published reports of a small but significant iridium anomaly at or close to the Paleocene/Eocene boundary provide supportive evidence for an impact. (C) 2003 Elsevier Science B.V. All rights reserved.