https://scholars.lib.ntu.edu.tw/handle/123456789/624805
標題: | Benthic foraminifer Mg/Ca anomalies in South Atlantic core top sediments and their implications for paleothermometry | 作者: | Raitzsch M Kuhnert H Groeneveld J Bickert T. JEROEN GROENEVELD |
關鍵字: | Benthic foraminifera; Carbonate chemistry; Laser ablation; Mg/Ca paleothermometry; South Atlantic | 公開日期: | 2008 | 卷: | 9 | 期: | 5 | 來源出版物: | Geochemistry, Geophysics, Geosystems | 摘要: | We used modern epibenthic foraminifer tests of Cibicidoides mundulus and Planulina wuellerstorfi from South Atlantic core top sediments in order to establish Mg/Ca-temperature relationships for the temperature range from 0 to 15°C. We obtained the following calibrations: Mg/Ca (mmol/mol) = 0.830*exp(0.145*BWT (°C)) for P. wuellerstorfi, and Mg/Ca (mmol/mol) = 0.627*exp(0.143*BWT (°C)) for C. mundulus. However, a number of tests, especially those bathed in North Atlantic Deep Water, revealed higher Mg/Ca ratios than predicted from the calibration. Our data suggest that Δ[CO32-] of bottom water exerts a significant control on ΔMg/Ca (temperature-corrected) of C. mundulus (ΔMg/Ca = 0.017*Δ[CO32-] - 0.14), while ΔMg/Ca of P. wuellerstorfi is more likely to be governed by TCO 2 (ΔMg/ Ca = -0.007*TCO2 + 15). Since both Delta;[CO32-] and TCO2 are closely linked to [CO32-], it is inferred that carbonate ion acts as secondary control, after temperature, on benthic shell Mg/Ca below ∼4°C. A drop in [CO32-] by 25 μmol/kg at 4 km water depth, as suggested for the Last Glacial Maximum, would decrease Mg/Ca by up to 0.4 mmol/mol, which leads to an underestimation of bottom water temperature by ∼3.5°C. Therefore our results indicate that the Mg/Ca thermometer should be used cautiously for benthicforaminifers where changes in the carbonate chemistry are present in the paleoceanographic record. copyright 2008 by the American Geophysical Union. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-55549104102&doi=10.1029%2f2007GC001788&partnerID=40&md5=1282d7c6210d2f4e65512a5e8e0fa158 https://scholars.lib.ntu.edu.tw/handle/123456789/624805 |
ISSN: | 15252027 | DOI: | 10.1029/2007GC001788 |
顯示於: | 海洋研究所 |
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