深水底栖有孔虫的氧同位素偏移

IF 0.9 4区 地球科学 Q4 PALEONTOLOGY
Janika Jöhnck, A. Holbourn, W. Kuhnt, N. Andersen
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引用次数: 4

摘要

尽管广泛使用海底有孔虫氧同位素组成(δ18O)作为古气候重建的代表,但物种间偏移的一致性和控制18O分馏的环境因素仍存在不确定性。我们研究了南中国海、望加锡海峡和帝汶海峡/东印度洋不同水文和沉积制度的岩芯顶部样本中一些常用的乌维捷琳娜、布利米纳和西比奇代物种的δ18O偏移。表动物群Cibicidoides mundulus和Cibicidiides wuellerstorfi的δ18O值在所有研究区域都没有显示出显著的偏移,而浅表动物群的Cibicidaides物种表现出更高的变异性,可靠性较差。我们没有发现Uvigerina和Bulimina物种之间的偏移,并假设这些属可以一起测量和/或替换。我们的研究结果表明,表动物群与环境海水接近平衡,因此比表动物群更可靠地记录了过去的冰量和/或底层水温变化。平衡方解石、表动物群和海底类群之间的偏移并不是恒定的“重要影响”,而是受到底部至孔隙水pH和碳酸盐离子浓度变化梯度的影响,这些变化取决于深水通风和颗粒碳酸盐和有机碳的输出通量。表层动物群和底层动物群之间的偏移量在0.58‰至0.73‰之间,这取决于区域底层和孔隙水条件。我们的发现强调了有机碳通量/降解和方解石溶解的区域和时间变化的重要性,这可能导致δ18O波动幅度的轻微低估或高估,特别是在底层和孔隙水的方解石饱和度快速变化的时期。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Oxygen Isotope Offsets in Deep-Water Benthic Foraminifera
Despite the extensive use of the benthic foraminiferal oxygen isotope composition (δ18O) as a proxy for paleoclimatic reconstructions, uncertainties remain regarding the consistency of interspecies offsets and the environmental factors controlling 18O fractionation. We investigated δ18O offsets of some frequently used Uvigerina, Bulimina, and Cibicidoides species in core top samples from different hydrographic and sedimentary regimes in the South China Sea, Makassar Strait, and Timor Strait/Eastern Indian Ocean. The δ18O values of the epifaunal taxa Cibicidoides mundulus and Cibicidoides wuellerstorfi showed no significant offset in all investigated regions, whereas shallow infaunal Cibicidoides species exhibited higher variability and were less reliable. We found no offsets between species of Uvigerina and Bulimina and assume that these genera can be measured together and/or substituted. Our results show that epifaunal taxa are close to equilibrium with ambient seawater and thus provide more reliable records of past ice volume and/or bottom water temperature variations than infaunal taxa. Offsets among equilibrium calcite, epifaunal taxa, and infaunal taxa are not constant “vital effects” but are influenced by changing gradients in bottom to pore water pH and carbonate ion concentrations that depend on deep-water ventilation and export flux of particulate carbonate and organic carbon. Offsets between epifaunal and infaunal taxa varied between 0.58 and 0.73‰, depending on regional bottom and pore water conditions. Our findings highlight the importance of regional and temporal variations in organic carbon flux/degradation and dissolution of calcite that may lead to slight under- or overestimates of the amplitude of δ18O fluctuations, especially during times of rapidly changing calcite-saturation of bottom and pore water.
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来源期刊
Journal of Foraminiferal Research
Journal of Foraminiferal Research 地学-古生物学
CiteScore
2.10
自引率
9.10%
发文量
32
审稿时长
>12 weeks
期刊介绍: JFR publishes original papers of international interest dealing with the Foraminifera and allied groups of organisms. Review articles are encouraged.
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