Continental margin molybdenum isotope signatures from the early Eocene
Continental margin molybdenum isotope signatures from the early Eocene
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DOI：
10.1016/j.epsl.2014.08.004
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发表时间：
2014-10-15
影响因子：
5.3
通讯作者：
Coe, Angela L.
中科院分区：
文献类型：
--
作者：
Dickson, Alexander J.;Cohen, Anthony S.;Coe, Angela L.
本文报道了两个特提斯洋（塔吉克斯坦的古鲁法蒂玛和格鲁吉亚的克乌河）中跨越古新世-始新世热盛期（PETM，约56 Ma）的海相沉积物的钼（Mo）同位素组成。当地的氧化还原指标表明，这两个地点经历了缺氧和间隔的euxinia（与硫化氢存在于海水中）在早期的部分PETM。然而，每个站点的钼同位素组成（表示为Δ Mo-98/95）差异很大。当地的氧化还原条件非常稳定，在古鲁法蒂玛，三角洲Mo-98/95达到最高的千分之0.96，这是类似的千分之0.7比最近推断的始新世早期海水从缺氧北冰洋存款。这一观察结果支持了这样一种论点，即在今天记录的海水和缺氧大陆边缘海洋沉积物之间可能也会在古记录中发现类似于千分之0.7的差异。相比之下，当地的氧化还原条件在Kheu河是不稳定的研究间隔，三角洲Mo-98/95远低于在古鲁法蒂玛。低三角洲Mo-98/95值在Kheu河是由于沉积后的再活化的影响，反复吸附和溶解的铁锰氧化物在短暂的时间间隔的底层水氧化。这些数据突出的重要性，获得多代理约束当地的氧化还原和古海洋环境之前，沉积矿床的钼同位素组成可以准确地解释。(C)2014爱思唯尔有限公司版权所有。
Molybdenum (Mo) isotope compositions of marine sedimentary deposits that span the Paleocene-Eocene Thermal Maximum (PETM, approximately 56 Ma) are presented from two Tethys Ocean sites (Guru Fatima, Tajikistan and Kheu River, Georgia). Local redox indicators suggest that both locations experienced anoxia and intervals of euxinia (with hydrogen sulphide present in seawater) during the early part of the PETM. However, the Mo-isotope compositions (expressed as delta Mo-98/95) for each site differ significantly. Local redox conditions were very stable at Guru Fatima, where delta Mo-98/95 reached a maximum of 0.96 parts per thousand, which is similar to 0.7 parts per thousand lower than for early Eocene seawater as recently inferred from euxinic Arctic Ocean deposits. This observation supports the argument that a similar to 0.7 parts per thousand difference between seawater and anoxic continental margin marine sediments documented at the present day might also be found in the paleorecord. In contrast, local redox conditions at Kheu River were not stable over the study interval, and delta Mo-98/95 were much lower than at Guru Fatima. The low delta Mo-98/95 values at Kheu River are attributed to the influence of post-depositional remobilization of Mo by repeated adsorption and dissolution of Fe-Mn oxides during brief intervals of bottom water oxidation. The data highlight the importance of obtaining multi-proxy constraints on both local redox and paleoceanographic setting before the Mo-isotope compositions of sedimentary deposits can be interpreted accurately. (C) 2014 Elsevier B.V. All rights reserved.