High benthic methane flux in low sulfate oceans: Evidence from carbon isotopes in Late Cretaceous Antarctic bivalves
High benthic methane flux in low sulfate oceans: Evidence from carbon isotopes in Late Cretaceous Antarctic bivalves
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低硫酸盐海洋中的高底栖甲烷通量：来自晚白垩世南极双壳类碳同位素的证据
DOI：
10.1016/j.epsl.2018.06.014
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发表时间：
2018
影响因子：
5.3
通讯作者：
Hall J
中科院分区：
文献类型：
--
作者：
Hall J
海洋底栖双壳类贝壳材料在沉积物-水界面上方提供了一个敏感的水化学档案，而沉积物-水界面又受到沉积地球化学和氧化还原反应的影响。硫酸盐对沉积碳循环有重要的控制作用，特别是甲烷的生成和氧化过程，较低的硫酸盐浓度可能导致沉积甲烷产量的增加。虽然海洋硫酸盐在显生界有明显的差异，但到目前为止还没有证据表明沉积物中甲烷的产量发生了变化。沉积甲烷的氧化产物有可能在海洋化石中被保存和检测到。本文介绍了从南极西摩岛白垩纪-古近纪(K-PG)界线的陆架序列中采集的两个保存完好的浅海双壳类(Lahillia和Cucullaea)的高分辨率碳酸盐同位素记录结果。这一序列具有先前存在的甲烷含量更丰富的微妙迹象，而这段时间的特点是海洋硫酸盐浓度比现代低得多。这些贝壳碳酸盐碳同位素记录差异很大：在一个极端，贝壳具有典型的平均值和与同期海洋溶解无机碳(DIC)来源和现代沉积碳循环相适应的小范围。另一方面，贝壳在一年的生长中具有高达23.8‰的碳同位素年际变化的大幅度周期，贝壳碳酸盐δ13C组成与−34‰一样负。具有这些增大范围和异常负值的贝壳以离散的间隔和在两个双壳类分类群中被发现。甲烷对解释双壳类贝壳中最负的碳酸盐-碳同位素值所需的甲烷贡献极高(根据质量平衡计算，在底水DIC中占30%至85%)。同一序列的有机碳同位素记录始终保持在−26.1至−21.7‰之间，表明甲烷的影响仅限于底层水域。该剖面中缺乏自生碳酸盐，表明甲烷氧化是在有氧条件下进行的，可能为底水瞬间脱氧提供了重要的驱动因素。在表明甲烷添加的情况下，季节性敏感性排除了甲烷水合物的控制。我们认为，这些数据表明，由于晚白垩世较低的海洋硫酸盐浓度，沉积物中甲烷生成的重要性和敏感性都增加了。海洋甲烷生产和氧化更具活力的趋势可能适用于地球历史上其他海洋硫酸盐含量较低的时期。
The shell material of marine benthic bivalves provides a sensitive archive of water chemistry immediately above the sediment–water interface, which in turn is affected by sedimentary geochemistry and redox reactions. Sulfate has a major controlling effect on sedimentary carbon cycling, particularly the processes of methane production and oxidation, with lower concentrations of sulfate likely resulting in an increase in sedimentary methane production. Whilst it is accepted that ocean sulfate varied markedly across the Phanerozoic, evidence of changes in methane production in sediments has so far been lacking. There is potential for the oxidation products of sedimentary methane to be preserved and detected in marine fossils. Here we present the results of high resolution carbonate isotope records from two taxa of well-preserved shallow-infaunal bivalve (Lahillia and Cucullaea) collected from the marine shelf succession across the Cretaceous–Paleogene (K–Pg) boundary in Seymour Island, Antarctica. The succession has pre-existing subtle indications of more abundant methane, and the time period is characterized by much lower marine sulfate concentrations than modern. These shell carbonate–carbon isotope records vary widely: at one extreme, shells have typical average values and small ranges compatible with a contemporaneous marine dissolved inorganic carbon (DIC) source and modern-style sedimentary carbon cycling. At the other, the shells have large-amplitude annual cycles of carbon isotopic variability of up to 23.8‰ within a single year of growth and shell carbonate δ 13 C compositions as negative as− 34‰. Shells with these increased ranges and unusually negative values are found at discrete intervals and across both bivalve taxa. The contribution of methane required to explain the most negative carbonate–carbon isotopic values in the bivalve shells is extremely high (between 30 to 85% of bottom-water DIC based on mass balance calculations). Records of organic-carbon isotopes from the same succession remained between− 26.1 and− 21.7‰ throughout, suggesting that methane influence was restricted to bottom-waters. A lack of authigenic carbonate in the section indicates that methane oxidation progressed aerobically and may have provided a significant driver for transient bottom water de-oxygenation. Where methane addition is indicated, the seasonal sensitivity precludes control by methane hydrates. We argue that these data represent the increased importance and sensitivity of methanogenesis in the sediments, enabled by lower ocean sulfate concentrations during the Late Cretaceous. The tendency towards a more dynamic role for marine methane production and oxidation is likely to apply to other times of low marine sulfate in Earth's history.
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影响因子：
3.7
作者：
Crame JA;Beu AG;Ineson JR;Francis JE;Whittle RJ;Bowman VC
通讯作者：
Bowman VC
影响因子：
1.9
作者：
Bowman, Vanessa C.;Francis, Jane E.;Haywood, Alan M.
通讯作者：
Haywood, Alan M.
DOI：
10.1016/j.palaeo.2015.03.034
发表时间：
2015-06
期刊：
Palaeogeography, Palaeoclimatology, Palaeoecology
影响因子：
--
作者：
T. Tobin;P. Ward
通讯作者：
T. Tobin;P. Ward
丹麦和南极洲 K/T 边界序列的锶同位素剖面
DOI：
--
发表时间：
1998
期刊：
影响因子：
--
作者：
J. McArthur;M. Thirlwall;M. Engkilde;W. Zinsmeister;R. Howarth
通讯作者：
R. Howarth
通过激光烧蚀 ICP-MS 进行硬化年代学研究
DOI：
10.1039/b002014l
发表时间：
2000
期刊：
Scopus
影响因子：
--
作者：
H. Toland;Bill Perkins;N. Pearce;Fergus Keenan;M. Leng
通讯作者：
M. Leng