Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis

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doi: 10.1016/j.epsl.2006.07.041
Authors:Elderfield, H.; Yu, J.; Anand, P.; Kiefer, T.; Nyland, B.
Author Affiliations:Primary:
University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Other:
Vrije Universiteit, Netherlands
PAGES International Project Office, Switzerland
University of Bergen, Norway
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 250(3-4), p.633-649. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:2006
Note:In English. 43 refs.; illus., incl. 1 table, sketch map
Summary:Benthic foraminiferal magnesium/calcium ratios were determined on one hundred and forty core-top samples from the Atlantic Ocean, the Norwegian Sea, the Indian Ocean, the Arabian Sea and the Pacific Ocean, mostly at sites with bottom water temperatures below 5°C. Mg/Ca ratios are consistently lower, by ∼0.2 mmol/mol, in samples cleaned using oxidative and reductive steps than using oxidative cleaning. Differences between Cibicidoides species have been identified: Mg/Ca of Cibicidoides robertsonianus > Cibicidoides kullenbergi > Cibicidoides wuellerstorfi. Comparison with bottom water temperatures support observations of lowered Mg/Ca of C. wuellerstorfi at temperature below ∼3°C compared with values predicted by published calibrations and from other Cibicidoides species. Hydrographic data shows that carbonate ion saturation (Δ[CO32-]) decreases rapidly below this temperature. An empirical sensitivity of Δ[CO32-] on Mg/Ca has been established for C. wuellerstorfi of 0.0086 ± 0.0006 mmol/mol/µmol/kg. A novel application using modern temperatures and Last Glacial Maximum temperatures derived via pore fluid modelling supports a carbonate ion saturation state effect on Mg incorporation. This may significantly affect calculated δ18Oseawater obtained from foraminiferal δ18O and Mg/Ca temperature. Abstract Copyright (2006) Elsevier, B.V.
Sections:Geochemistry
Subsections:Sedimentary rocks
Subjects:Alkaline earth metals; Anomalinidae; Benthic taxa; Bottom water; Buliminacea; Calcium; Carbonate ion; Cassidulinacea; Cenozoic; Chemical ratios; Cibicidoides; Cibicidoides wuellerstorfi; Foraminifera; Geologic thermometry; Isotope ratios; Isotopes; Last glacial maximum; Magnesium; Metals; Mg/Ca; Microfossils; O-18/O-16; Oxygen; Paleo-oceanography; Paleotemperature; Partitioning; Quaternary; Rotaliina; Stable isotopes; Temperature; Uvigerina; Uvigerinidae; Invertebrata; Protista
Abstract Numbers:06M/4709
Record ID:2007058683
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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