A new model for the Kellwasser Anoxia Events (Late Devonian): Shallow water anoxia in an open oceanic setting in the Central Asian Orogenic Belt
A new model for the Kellwasser Anoxia Events (Late Devonian): Shallow water anoxia in an open oceanic setting in the Central Asian Orogenic Belt
复制标题
DOI：
10.1016/j.palaeo.2014.02.016
复制
发表时间：
2014-04-01
影响因子：
3
通讯作者：
DeReuil, Aubry A.
中科院分区：
文献类型：
--
作者：
Carmichael, Sarah K.;Waters, Johnny A.;DeReuil, Aubry A.
Frasnian-Famennian大规模灭绝事件摧毁了热带海洋生态系统，在分类和生态严重性方面排名前六。灭绝和Kellwasser缺氧事件之间的密切地层联系支持海洋缺氧和灭绝之间的联系。上凯尔瓦瑟层和下凯尔瓦瑟层已在劳鲁西亚、冈瓦纳、西伯利亚和华南的陆缘和盆地环境中被识别出来。中国新疆西北部的红古勒楞组（晚泥盆世）既包含弗拉斯期-法门期界线，也包含弗拉斯期-法门期灭绝事件的反弹，该事件发生在与泥盆纪海洋岛弧杂岩（中亚造山带的一部分，或CAOB）相关的高含盐浅海环境中。本文通过多种地球化学指标的分析，表明红古勒楞组也记录了上凯尔瓦瑟缺氧事件。与以往认为Kellwasser事件仅限于陆表海道和海盆的研究不同，我们的研究结果表明，Kellwasser事件不仅发生沿着封闭的Rheic洋的浅陆缘，也发生在古特提斯开放洋部分的浅水区。以前的解释Kellwasser事件从陆缘和盆地呼吁深缺氧底层水迁移到浅水环境作为一种杀死机制，为浅海生态系统或归因于海平面上升和随后的停滞。没有证据表明泥盆纪的海洋在凯尔瓦瑟事件中完全翻转;同样，泥盆纪的许多海侵事件与黑色页岩无关。因此，我们提出了一个替代机制的Kellwasser事件的基础上，从CAOB，缺氧的新证据是由表层沃茨的富营养化驱动。(C)2014爱思唯尔有限公司版权所有。
The Frasnian-Famennian mass extinction event devastated tropical marine ecosystems and ranks in the top six in taxonomic and ecological severity. The close stratigraphic association between the extinction and the Kellwasser Anoxia Events support a link between oceanographic anoxia and extinction. The Upper and Lower Kellwasser horizons have been identified in epicontinental and basinal settings in Laurussia, Gondwana, Siberia, and South China. The Hongguleleng Formation (Late Devonian) in northwestern Xinjiang, China, contains both the Frasnian-Famennian boundary and the rebound from the Frasnian-Famennian extinction event in a highly fossiliferous shallow marine setting associated with a Devonian oceanic island arc complex (part of the Central Asian Orogenic Belt, or CAOB). Here we show that the Hongguleleng Formation also records the Upper Kellwasser Anoxia Event through analysis of multiple geochemical proxies. In contrast to previous studies asserting that the Kellwasser Events were restricted to epicontinental seaways and basins, our results indicate that it occurred not only along the shallow continental margins of the closing Rheic Ocean, but also in shallow water in the open oceanic part of Paleotethys. Previous explanations for the Kellwasser Events from epicontinental margins and basins call for the migration of deep anoxic bottom water into shallow water environments as a kill mechanism for shallow marine ecosystems or attribute it to sea level rise and subsequent stagnation. There is no evidence that the Devonian oceans completely overturned during the Kellwasser Events; similarly, many transgressive events in the Devonian are not associated with black shales. We therefore suggest an alternative mechanism for the Kellwasser Events based on new evidence from the CAOB, where anoxia is driven by episodic eutrophication of surface waters. (C) 2014 Elsevier B.V. All rights reserved.