The boron isotopic composition (δ¹¹B) of benthic foraminifera provides a valuable tool to reconstruct past deep-water pH. As the abundance of monospecific species might be limited in sediments, microanalytical techniques can help to overcome this problem, but such studies on benthic foraminiferal δ¹¹B are sparse. In addition, microanalytics provide information on the distribution of δ¹¹B at high spatial resolution to increase the knowledge of biomineralization processes, for example. For this study, we investigated the intra- and inter-shell δ¹¹B variability of the epibenthic species Cibicidoides wuellerstorfi, which is widely used in paleoceanography, by secondary ion mass spectrometry (SIMS) and femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS). While the average δ¹¹B values obtained from these different techniques agree remarkably well with bulk solution values to within ±0.1 ‰, a relatively large intra-shell variability was observed. Based on multiple measurements within single shells, the SIMS and LA data suggest median variations of 4.8 ‰ and 1.3 ‰ (2σ), respectively, while the larger spread for SIMS is attributed to the smaller volume of calcite being analyzed in each run. When analytical uncertainties and volume-dependent differences in δ¹¹B variations are taken into account for these methods, the intra-shell variability is estimated to be on the order of ∼3 ‰ and ∼0.4 ‰ (2σ) on a ∼20 and 100 µm scale, respectively. In comparison, the δ¹¹B variability between shells exhibits a total range of ∼3 ‰ for both techniques, suggesting that several shells need to be analyzed for accurate mean δ¹¹B values. Based on a simple resampling method, we conclude that ∼12 shells of C. wuellerstorfi must be analyzed using LA-MC-ICPMS to obtain an accurate average value within ±0.5 ‰ (2σ) to resolve pH variations of ∼0.1. Based on our findings, we suggest preferring the conventional bulk solution MC-ICPMS over the in situ methods for paleo-pH studies, for example. However, SIMS and LA provide powerful tools for high-resolution paleoreconstructions, or for investigating ontogenetic trends in δ¹¹B.

中文翻译：

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技术说明：单壳δ ¹¹的乙分析Cibicidoides wuellerstorfi使用飞秒激光烧蚀MC-ICPMS和二次离子质谱分析

硼同位素组合物（δ ¹¹乙底栖有孔虫的）提供了重建过去深水pH值的宝贵工具。作为单特异性的丰度可能在沉积物中被限制，微量分析技术可以帮助解决这个问题，但对底栖有孔虫这种研究δ ¹¹乙是稀疏。此外，microanalytics提供的分布信息δ ¹¹乙以高的空间分辨率，以增加生物矿化过程的知识，例如。在这项研究中，我们调查了内部和相互之间壳δ ¹¹乙的底栖物种的变异Cibicidoides wuellerstorfi通过二次离子质谱（SIMS）和飞秒激光消融多收集器电感耦合等离子体质谱（LA-MC-ICPMS）在古海洋学中得到广泛应用。而平均δ ¹¹乙从这些不同的技术而获得的值与内本体溶液值吻合得非常好于±0.1  ‰，观察到相对较大的内壳的可变性。基于单壳内的多个测量，SIMS和LA的数据表明的4.8‰和1.3‰（中位数变化2 σ），分别，而SIMS的价差较大归因于方解石的小体积中的每个运行被分析。当分析不确定性和在体积依赖性差异δ ¹¹乙变化被考虑用于这些方法中，帧内-壳变异性估计为数量级〜3  ‰和〜0.4‰ （2 σ）上的约20和100 微米尺度，分别。相比较而言， δ ¹¹乙壳之间的可变性显示出的总范围〜3  ‰，这两种技术，这表明几个壳需要分析准确平均 δ ¹¹乙值。基于一个简单的重采样方法，我们得出这样的结论〜12个 的弹C. wuellerstorfi必须使用LA-MC-ICPMS，以获得内准确的平均值进行分析±0.5  ‰（2 σ）到的决心的pH变化〜0.1。根据我们的发现，例如，对于古pH研究，我们建议使用传统的本体溶液MC-ICPMS而不是原位方法。然而，SIMS和LA提供强大的工具，对于高分辨率paleoreconstructions，或在调查个体发育趋势 δ ¹¹乙。