Abstract

Larger benthic foraminifera (LBF) contribute significantly to the modern reef carbonates. They were also the major producers of carbonate in the shallow marine environments of the Paleogene. It is thus imperative to investigate their potential as a paleotemperature proxy. It is common to calculate past seawater temperatures using trace elements and stable isotope proxies on foraminiferal calcite. The various LBF genera comprise tests with different MgCO₃% and exhibit vital effects, making it important to carry out genus-specific temperature calibration studies. For the present study, live specimens of Baculogypsina sphaerulata were collected over seven months from reef flats of Akajima (Okinawa, Japan). The whole-shells of B. sphaerulata from each of the seven sampling months were analyzed using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) and IRMS (Isotope Ratio Mass Spectrometer) techniques. The relationship between Mg/Ca and δ¹⁸O with seawater temperature is established, and thus its potentiality for temperature calibration is discussed. The following proxy-temperature calibrations are proposed in this study: (i) Mg/Ca (mmol/mol) = 0.0267e^0.3389T and (ii) T (^oC) = 19.0–2.94 (δ¹⁸O_f−δ¹⁸O_w).

Research Highlights

1. 1.

   The geochemical composition of Baculogypsina sphaerulata was studied to understand its potentiality for paleotemperature calibration.

2. 2.

   The regression should be always over the complete range of growth temperatures experienced by the foraminifer for better correlation.

3. 3.

   A genus-specific temperature calibration is important in the case of larger benthic foraminifera.

4. 4.

   The proxy-temperature calibrations for Baculogypsina sphaerulata are proposed in this study.

中文翻译：

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大型底栖有孔虫Baculogypsina sphaerulata中的微量元素和稳定的同位素变化：海水温度的潜在代表。

摘要

较大的底栖有孔虫（LBF）对现代礁碳酸盐有很大贡献。他们还是古近纪浅海环境中碳酸盐的主要生产者。因此，有必要研究它们作为古温度替代物的潜力。通常使用有孔虫方解石上的微量元素和稳定的同位素近似值来计算过去的海水温度。各种LBF属均包含含₃％MgCO的测试，并且显示出重要的影响，因此进行属属温度校准研究非常重要。对于本研究，在七个月的时间里从赤岛（日本冲绳）的礁滩上收集了球形芽孢杆菌的活体标本。球形芽孢杆菌的全壳使用ICP-AES（电感耦合等离子体原子发射光谱法）和IRMS（同位素比质谱仪）技术对七个采样月中的每个采样月的样品进行分析。镁/钙之间和的关系δ ¹⁸ ö与海水温度被建立，并且因此其对温度校准潜力进行了讨论。以下代理-温度校准都提出了本研究：（ⅰ）镁/钙（毫摩尔/摩尔）= 0.0267e ^{0.3389 Ť}和（ii）ţ（^Ô C）= 19.0-2.94（δ ¹⁸ ö _˚F - δ ¹⁸ ö _w）。

研究重点

1. 1。

   研究了Baculogypsina sphaerulata的地球化学组成，以了解其用于古温度标定的潜力。

2. 2。

   回归应始终在有孔虫经历的整个生长温度范围内，以实现更好的相关性。

3. 3。

   在较大的底栖有孔虫的情况下，属特定温度的校准很重要。

4. 4，

   在这项研究中提出了球状杆菌的代用温度校准。