https://doi.org/10.1016/j.epsl.2021.116956
https://doi.org/10.1016/j.epsl.2021.116956
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https://doi.org/10.1016/j.epsl.2021.116956
DOI：
10.1016/j.epsl.2021.116956
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发表时间：
2021
影响因子：
5.3
通讯作者：
Nelson, L.L.
中科院分区：
文献类型：
--
作者：
Nelson, L.L.
新元古代碳同位素偏移通常归因于与气候不稳定和/或氧化相关的全球有机碳埋藏部分的变化。在这里，我们展示了碳酸盐沉积物在大约661–< 651 Ma Sturtian 和 Marinoan 冰川之间的成冰期非冰川间质表现出碳酸盐-碳同位素值与同时代单位的横向偏移高达 10。在美国加利福尼亚州帕纳明特山脉的成冰期序列的 Thorndike 亚段中，碳酸盐-碳同位素值可以与横向不连续的白云石化前缘联系起来：石灰岩表现出δ13Ccarb 值为～+ 4 至+ 9，而地层等效白云岩的值始终较低，在～-4 和+ 4 之间。对上覆马里诺冰川混积岩碎屑的现场观察和分析表明，δ13Ccarb 值的偏移是由前马里诺白云石化到同马里诺白云石化造成的。此外，δ44/40Ca 和 δ26Mg 数据表明，这种同位素变异是由沉积物缓冲成岩作用造成的。我们认为，极其正的 δ13Ccarb 值记录了受限台地表水和/或含氧孔隙流体内的局部初级生产力，负值反映了沉积物孔隙水中有机碳的厌氧再矿化。在这种情况下，桑代克亚段的原始方解石/文石和随后的白云石沉淀物都没有记录代表全球成冰期海水的 δ13Ccarb 值，而是记录了当地溶解无机碳库的演化。© 2021 Elsevier BV 保留所有权利。
Neoproterozoic carbon isotope excursions are commonly attributed to changes in the global fraction of organic carbon burial associated with climate instability and/or oxygenation. Here we show that carbonate sediment deposited during the ca. 661–< 651 Ma Cryogenian non-glacial interlude between the Sturtian and Marinoan glaciations exhibit lateral offsets in carbonate-carbon isotope values from coeval units by as much as 10. Within the Thorndike submember of the Cryogenian succession in the Panamint Range, California, USA, carbonate-carbon isotope values can be linked to a laterally discontinuous dolomitization front: limestones exhibit δ13Ccarb values of∼+ 4 to+ 9, whereas values of stratigraphically equivalent dolostones are consistently lower, between∼-4 and+ 4. Field observations and analyses of clasts from the overlying Marinoan glacial diamictite show that the offset in δ13Ccarb values resulted from pre-to syn-Marinoan dolomitization. Further, δ44/40Ca and δ26Mg data indicate that this isotopic variability resulted from sediment-buffered diagenesis. We propose that extremely positive δ13Ccarb values record local primary productivity within restricted platform surface waters and/or oxygenated pore fluids and negative values reflect anaerobic remineralization of organic carbon within sediment pore waters. In this scenario, neither the original calcite/aragonite nor subsequent dolomite precipitates of the Thorndike submember record δ13Ccarb values that are representative of global Cryogenian seawater, and instead they archive the evolution of local dissolved inorganic carbon pools.© 2021 Elsevier BV All rights reserved.