Gradual onset of anoxia across the Permian-Triassic Boundary in Svalbard, Norway
Gradual onset of anoxia across the Permian-Triassic Boundary in Svalbard, Norway
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DOI：
10.1016/j.palaeo.2013.02.004
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发表时间：
2013-03-15
影响因子：
3
通讯作者：
Bond, David P. G.
中科院分区：
文献类型：
--
作者：
Dustira, Anna M.;Wignall, Paul B.;Bond, David P. G.
二叠纪-三叠纪生物灭绝事件被认为是中生代最具破坏性的环境危机。由于涉及许多巧合的因素，海洋缺氧在灭绝过程中的作用仍然知之甚少。在这项研究中，一个北方二叠纪三叠纪边界（PTB）从斯瓦尔巴群岛，挪威部分进行了调查，目的是更好地了解当地海洋缺氧发病和灭绝事件的时间和性质的PTB。该剖面包括Kapp Starostin和Vikinghogda地层; C-13（org）值表明PTB位于Vikinghogda地层的下部。在卡普Starostin组顶部的滞后沉积表明，在晚二叠世灭绝事件前不久，海洋间断和随之而来的海侵，这意味着同时发生的重大生态变化和海平面上升。黄铁矿framboid尺寸分布和总有机碳（TOC）被用来评估底层水的氧条件，并显示在底层水的氧化还原条件和灭绝的变化有明确的联系。在Kapp Starostin地层沉积物沉积过程中，缺氧至缺氧的底层水条件占主导地位，并在地层边界以上变为缺氧至缺氧的条件。缺氧的发生并不是突然的，而是在晚二叠世期间Kapp Starostin组内逐渐增加。底沃茨达到一个长期的缺氧状态，以euxinia的临界点与最后的灭绝事件相吻合，虽然在卡普Starostin形成的顶部生物组合的变化表明在此之前的海洋生态系统危机。正如我们的研究部分所看到的，与格陵兰岛和加拿大北极地区相关的北方地区的氧气消耗似乎一直比低纬度地区更严重。(C)2013爱思唯尔有限公司版权所有。
The Permian-Triassic extinction event is considered to be the most devastating environmental crisis of the Phanerozoic. With many coinciding factors involved, the role of marine anoxia during the extinction is still poorly understood. In this study a boreal Permian-Triassic Boundary (PTB) section from Svalbard, Norway has been investigated with the aim of better understanding the timing and nature of local marine anoxia onset and extinction events across the PTB. The section comprises the Kapp Starostin and Vikinghogda formations; delta C-13(org) values indicate the PTB is located within the lower part of the Vikinghogda Formation. Lag deposits at the top of the Kapp Starostin Formation indicate a marine hiatus and ensuing transgression during the Late Permian shortly before the extinction event, implying concurrence of major ecological changes and sea-level rise. Pyrite framboid size distributions and total organic carbon (TOC) were used to evaluate bottom water oxygen conditions, and show that changes in bottom water redox conditions and extinction are clearly linked. Oxic to dysoxic bottom water conditions prevailed during deposition of Kapp Starostin Formation sediments and changed to anoxic to euxinic conditions above the formation boundary. The onset of anoxia is not abrupt but rather shows a gradual increase within the Kapp Starostin Formation during the Late Permian. The tipping point where bottom waters reach a long-term state of anoxia to euxinia coincides with the final extinction event, though changes in biotic assemblages at the top of the Kapp Starostin Formation indicate a marine ecosystem crisis prior to this. Oxygen depletion in the boreal region, as seen in our study section and correlating to Greenland and Arctic Canada, seems to be consistently more severe than in lower latitude settings. (C) 2013 Elsevier B.V. All rights reserved.