TY - JOUR

T1 - Technical note

T2 - Single-shell δ11B analysis of Cibicidoides wuellerstorfi using femtosecond laser ablation MC-ICPMS and secondary ion mass spectrometry

AU - Raitzsch, Markus

AU - Rollion-Bard, Claire

AU - Horn, Ingo

AU - Steinhoefel, Grit

AU - Benthien, Albert

AU - Richter, Klaus Uwe

AU - Buisson, Matthieu

AU - Louvat, Pascale

AU - Bijma, Jelle

N1 - Funding Information: Financial support. This research has been supported by the Funding Information: Acknowledgements. This research was carried out in the frame-work of the joint French/German project “B2SeaCarb” and was supported by the Deutsche Forschungsgemeinschaft (DFG) grant number BI 432/10-1 to Jelle Bijma and DFG grant number HO 3257/5- 1 to Ingo Horn. On the French side, the project was supported by the French National Research Agency (ANR) grant number ANR-16-CE92-0010 to Claire Rollion-Bard. Claire Rollion-Bard thanks Nordine Bouden (CRPG) for his technical help, and the MARUM GeoB core repository is acknowledged for providing sediment samples. Kaoru Kubota as well as the referees Dennis Mayk and Lu-bos Polerecky are thanked for their help in improving the paper.

PY - 2020/11/10

Y1 - 2020/11/10

N2 - 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 highresolution paleoreconstructions, or for investigating ontogenetic trends in δ11B.

AB - 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 highresolution paleoreconstructions, or for investigating ontogenetic trends in δ11B.

UR - http://www.scopus.com/inward/record.url?scp=85096086328&partnerID=8YFLogxK

U2 - 10.5194/bg-17-5365-2020

DO - 10.5194/bg-17-5365-2020

M3 - Article

AN - SCOPUS:85096086328

VL - 17

SP - 5365

EP - 5375

JO - BIOGEOSCIENCES

JF - BIOGEOSCIENCES

SN - 1726-4170

IS - 21

ER -