Characterization of Mg/Ca distributions in planktonic foraminifera species by electron microprobe mapping

Sadekov, A.Yu. and Eggins, S.M. and De Deckker, P. (2005) Characterization of Mg/Ca distributions in planktonic foraminifera species by electron microprobe mapping. Geochemistry Geophysics Geosystems, 6 (12). ISSN 1525-2027 DOI 10.1029/2005GC000973

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Abstract

The distribution of Mg/Ca within the tests of eight modern planktonic foraminifer species has been characterized using electron microprobe mapping. Species include several that are commonly used for estimation of past seawater temperatures (Globigerinoides ruber, G. sacculifer, Neogloboquadrina incompta (synonym of N. pachyderma dex.), N. dutertrei, and G. truncatulinoides). Each of the investigated species displays large variations in Mg/Ca composition within individual tests. However, the pattern of Mg/Ca variation is notably different between symbiont-bearing and symbiont-free species. In symbiotic species, cyclic Mg/Ca compositional banding occurs that is characterized by narrow (<1-3 μm), high-Mg/Ca (typically 8-11 mmol/mol) bands, intercalated between broader low Mg/Ca (typically 1-5 mmol/mol) bands. This factor of 2-3 difference equates to an apparent calcification temperature change of 10°C or more. Such temperature changes are considered highly improbable and suggest vital effects significantly modify the incorporation of Mg/Ca into the tests of symbiont-bearing species. These vital effects remain poorly understood and demand further careful evaluation as they may need to be accounted for when making reliable reconstructions of past oceanic temperatures. Symbiont-free species typically have fewer and broader compositional bands that may reflect more closely changes in calcification temperature as these species migrate within a water column. Copyright 2005 by the American Geophysical Union.

Item Type: Article
Uncontrolled Keywords: NILAREP
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Geochemistry Geophysics Geosystems
Volume: 6
Identification Number: 10.1029/2005GC000973
Depositing User: Sarah Humbert
Date Deposited: 02 Apr 2012 11:24
Last Modified: 23 Jul 2013 10:03
URI: http://eprints.esc.cam.ac.uk/id/eprint/2441

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