Calibrating Mg/Ca ratios of multiple planktonic foraminiferal species with δ18O-calcification temperatures: paleothermometry for the upper water column.

Regenberg, Marcus, Steph, Silke, Nürnberg, Dirk , Tiedemann, Ralf and Garbe-Schönberg, C.-Dieter (2009) Calibrating Mg/Ca ratios of multiple planktonic foraminiferal species with δ18O-calcification temperatures: paleothermometry for the upper water column. Earth and Planetary Science Letters, 278 . pp. 324-336. DOI 10.1016/j.epsl.2008.12.019.

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Supplementary data:

Abstract

In order to consistently approximate the thermal vertical structure of past upper water columns, Mg/Ca ratios of eight planktonic foraminiferal species with different preferential calcification depths selected from 76 tropical Atlantic and Caribbean sediment-surface samples were calibrated with δ18O-derived calcification temperatures with an overall range of ≈ 8–28 °C. Extending the broad number of species-specific calibrations, which agree well especially with our shallow-dweller calibrations, this study presents new bulk calcite Mg/Ca vs. calcification temperature relationships for shallow-dwelling Globigerinoides ruber pink, thermocline-dwelling Globorotalia menardii, and deep-dwelling Globorotalia truncatulinoides dextral and Globorotalia crassaformis not separately calibrated before. The species-specific temperature sensitivities are relatively similar (≈ 7–11% increase in Mg/Ca per 1 °C), yet y-axis intercepts vary from 0.23–0.65 for the shallow and thermocline dwellers to 0.83–1.32 for the deep dwellers. Based on these differences, we established a ‘warm water’ calibration for temperatures > 19 °C (Mg/Ca = 0.29·exp(0.101·T); r = 0.90; shallow and thermocline dwellers) and a ‘cold water’ calibration for temperatures < 15 °C (Mg/Ca = 0.84·exp(0.083·T); r = 0.85; deep dwellers). These calibrations are offset by ≈ 8 °C. This may be significant for paleotemperature reconstructions, which are afflicted with the problem that similar Mg/Ca offsets are probably characteristic of extinct species used to calculate past temperatures.

Document Type: Article
Keywords: Mg/Ca, stable oxygen isotope, Planktonic Foraminifera, calcification-temperature calibration, core-top sample, tropical atlantic
Research affiliation: AWI
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.epsl.2008.12.019
ISSN: 0012-821X
Projects: Future Ocean
Date Deposited: 07 Apr 2009 14:19
Last Modified: 03 Jul 2019 12:52
URI: http://oceanrep.geomar.de/id/eprint/464

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