Mg/Ca in the benthic foraminifera Cibicidoides wuellerstorfi and Cibicidoides mundulus: Temperature versus carbonate ion saturation
Mg/Ca in the benthic foraminifera Cibicidoides wuellerstorfi and Cibicidoides mundulus: Temperature versus carbonate ion saturation
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DOI：
10.1016/j.epsl.2008.09.015
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发表时间：
2008-11
影响因子：
5.3
通讯作者：
Jimin Yu;H. Elderfield
中科院分区：
文献类型：
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作者：
Jimin Yu;H. Elderfield
测量了从全球海洋核心顶部和北大西洋六个核心中采集的两种广泛使用的底栖有孔虫物种Cibicidoides wuellerstorfi和Cibicidoides mundulus（Cibicidoides kullenbergi）的镁/钙（Mg/Ca）比，以研究Mg/Ca变化、清洁效果以及底层水温（BWT）和深水碳酸根离子饱和度（Δ[CO 32-]）的影响。两种物质的重复测量显示Mg/Ca变异性为0.07±0.07 mmol/mol。与通过氧化清洗清洗的样品中的Mg/Ca相比，通过还原清洗清洗的样品中的Mg/Ca比显著降低0.10±0.09 mmol/mol，这可能是由于在还原清洗步骤期间的优先浸出。相对于冰川-间冰期Mg/Ca的变化（本研究为0.05-0.31 mmol/mol），清洁的影响很大。对大范围岩心顶部数据的回归分析表明，C。wuellerstorfi Mg/Ca受深水Δ[CO 32 −]的影响很大，灵敏度约为0.009 mmol/mol/µmol/kg。当BWT包括在回归中时，相关性稍微更显著，BWT对Mg/Ca的敏感性较弱，在0.03±0.01和0.07±0.02 mmol/mol/°C之间。由于大多数岩芯顶部样本的Δ[CO 32-]和BWT协变，因此通过比较北大西洋岩芯深度横断面的冰期与间冰期的Mg/Ca变化，制定了一种分离这两种影响的替代方法，其中BWT和碳酸根离子历史自末次冰期以来一直受到很好的限制。该样带的结果表明，BWT效应<0.03 mmol/mol/°C，弱于从核心顶部研究推断的结果。因此，从岩心上、下的资料可以看出，C。wuellerstorfi Mg/Ca对BWT变化不敏感。弱BWT效应，与自然变异相比，复杂的使用镁/钙在这个物种重建过去的BWT。考虑到各种环境下的所有测量样品，C。Mundulus Mg/Ca比值与BWT或深水Δ[CO 32 −]没有相关性。
Magnesium/calcium (Mg/Ca) ratios in two widely used benthic foraminiferal species, Cibicidoides wuellerstorfi and Cibicidoides mundulus (Cibicidoides kullenbergi), picked from global ocean core-tops and from six cores in the North Atlantic Ocean have been measured to investigate Mg/Ca variability, cleaning effect, and influences from bottom water temperature (BWT) and deep water carbonate ion saturation (Δ[CO32−]). Replicate measurements of the two species reveal Mg/Ca variability of 0.07±0.07 mmol/mol. Compared with Mg/Ca in samples cleaned by oxidative cleaning, Mg/Ca ratios are significantly lowered, by 0.10±0.09 mmol/mol, in samples cleaned by reductive cleaning, likely due to preferential leaching during the reductive cleaning step. The cleaning influence is large relative to glacial–interglacial Mg/Ca changes (0.05–0.31 mmol/mol by this study). Regression of core-top data from a wide range of locations show that C. wuellerstorfi Mg/Ca is strongly affected by deep water Δ[CO32−] with a sensitivity of ~0.009 mmol/mol per µmol/kg. When BWT is included in regressions, the correlation is slightly more significant with a weak BWT sensitivity on Mg/Ca of between 0.03±0.01 and 0.07±0.02 mmol/mol per °C. Because Δ[CO32−] and BWT co-vary for most core-top samples, an alternate method of separating the two effects was made by comparing glacial to interglacial changes in Mg/Ca from a depth transect of North Atlantic cores where the BWT and carbonate ion histories since the last glacial period have been well constrained. Results from this transect suggest that the BWT effect is <0.03 mmol/mol per °C, weaker than inferred from the core-top study. Therefore, core-top and down core data suggest that C. wuellerstorfi Mg/Ca is insensitive to BWT changes. The weak BWT effect, when compared with natural variability, complicates the use of Mg/Ca in this species to reconstruct past BWT. Taking all measured samples from various environments into account, C. mundulus Mg/Ca ratios show no correlation with BWT or deep water Δ[CO32−].