Integrated sedimentary, biotic, and paleoredox dynamics from multiple localities in southern Laurentia during the late Silurian (Ludfordian) extinction event
Integrated sedimentary, biotic, and paleoredox dynamics from multiple localities in southern Laurentia during the late Silurian (Ludfordian) extinction event
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DOI：
10.1016/j.palaeo.2020.109799
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
Chelsie N. Bowman;Anders Lindskog;Nevin P. Kozik;Claudia Gail Richbourg;J. Owens;Seth A. Young
中科院分区：
文献类型：
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作者：
Chelsie N. Bowman;Anders Lindskog;Nevin P. Kozik;Claudia Gail Richbourg;J. Owens;Seth A. Young
志留纪是一个重大的气候转型时期，其间不时出现多个生物危机和全球碳循环扰动。这些生物事件中最严重的是晚志留世（Ludfordian）Lau/Kozlowskii灭绝事件（LKE）和相关的Lau碳同位素漂移（CIE）。虽然灭绝事件和刘CIE是全球性的记录，唯一的记录，迄今为止的本地和全球海洋古氧化还原条件，通过这一间隔是从一个单一的地区在斯堪的纳维亚半岛。在这里，我们研究了四个部分沿着测深断面的混合碳酸盐-硅质沉积物从美国田纳西州西部。一种新的方法，使用多代理数据集相结合的高分辨率地球化学数据和微相分析，从多个地方探讨了在全球范围内广泛的环境剧变的时间局部/区域规模的氧化还原不均匀性的可能性。碳酸盐碳同位素和碳酸盐相关的硫酸盐硫同位素记录的成对的正偏移支持最近的工作从斯堪的纳维亚半岛的碳酸盐和硅质岩的继承，这表明全球增强有机碳和黄铁矿埋藏的euxinic（缺氧和硫化物水柱）的条件下，在中Ludfordian在海洋中的扩张。此外，有机碳同位素和黄铁矿硫同位素的正偏移反映了全球氧化还原的变化。I/Ca比值的地层学趋势意味着低氧条件的局部扩张，在CIE的上升翼和峰值期间具有低但非零的值。化石组合在整个大陆架和CIE间隔内各不相同。化石组合和I/Ca的地层变化与局部和全球的氧合和海平面的变化密切相关，在中Ludfordian。集体数据表明，随着海洋氧化还原条件的变化以及LKE期间海平面的变化，生物发生了显着的重组，但该地区目前详细的宏观生物多样性不受限制。
The Silurian was a time of major climatic transition punctuated by multiple biotic crises and global carbon cycle perturbations. The most severe of these biotic events was the late Silurian (Ludfordian) Lau/Kozlowskii extinction event (LKE) and the associated Lau carbon isotope excursion (CIE). Although the extinction event and Lau CIE are globally documented, the only records thus far of local and global marine paleoredox conditions through this interval are from a single region in Scandinavia. Here we examine four sections along a bathymetric transect of mixed carbonate-siliciclastic sediments from western Tennessee, USA. A novel approach using a multi-proxy dataset combining high-resolution geochemical data and microfacies analyses from multiple localities explores the possibilities of local/regional-scale redox heterogeneities during a time of widespread environmental upheaval on a global scale. Paired positive excursions recorded in carbonate carbon isotopes and carbonate-associated sulfate sulfur isotopes support recent work from carbonate and siliciclastic successions from Scandinavia, suggesting a global enhancement of organic carbon and pyrite burial driven by an expansion of euxinic (anoxic and sulfidic water column) conditions in the oceans during the mid-Ludfordian. Furthermore, positive excursions in organic carbon isotopes and pyrite sulfur isotopes reflect the global changes in redox. Stratigraphic trends in I/Ca ratios imply a local expansion of low-oxygen conditions, with low, but non-zero values during the rising limb and peak of the CIE. The fossil assemblages vary across the shelf and through the CIE interval. Stratigraphic changes in fossil assemblages and I/Ca are closely associated with local and global changes in oxygenation and sea level during the mid-Ludfordian. The collective data indicate significant biotic reorganization in response to changes in marine redox conditions and in conjunction with sea-level variation during the LKE interval, but detailed macroscopic biodiversity is currently unconstrained for this region.