Skip to Main content Skip to Navigation
Journal articles

Chemical Heterogeneity of Mg, Mn, Na, S, and Sr in Benthic Foraminiferal Calcite

Abstract : The chemical composition of fossil foraminiferal shells (tests) is widely used as tracers for past ocean chemistry. It is, therefore, important to understand how different (trace) elements are transported and incorporated into these tests from adjacent seawater. The elemental distribution within the walls of foraminiferal tests might be used to differentiate between proposed transport mechanisms. Here, the microdistribution of Mg, Mn, Na, S, and Sr in tests of three species of foraminifera, known to have contrasting test chemistry, is investigated by a combination of electron probe microanalysis (EPMA) and nanoscale secondary ion mass spectrometry (nanoSIMS), micro-X-ray fluorescence (µXRF), and micro-X-ray absorption near-edge structure (µXANES) analyses. The three investigated species are the symbiont-barren Ammonia sp. T6 and Bulimina marginata, which precipitate a low-Mg calcite test, and the symbiont-bearing species Amphistegina lessonii, which produces a test with intermediate Mg content. Because all analyzed tests were formed under controlled and identical laboratory conditions, the observed distributions of elements are not due to environmental variability but are a direct consequence of the processes involved in calcification or, in the case of A. lessonii, possibly symbiont activity. Despite some variability in elemental microdistribution between specimens from a given species, our combined dataset shows species-specific distributions of the elements (e.g., peak heights and/or band-widths) and also a systematic colocation of Mg, Na, S, and Sr for all three species, suggesting a coupled or simultaneous uptake, transport, and incorporation of these elements during chamber addition. The observed trace element patterns generally reflect a laminar calcification model, suggesting that heterogeneity of these elements is intrinsically linked to chamber addition. Although the incorporation of redox-sensitive Mn depends on the Mn concentration of the culture medium, the Mn distribution observed in Ammonia sp. suggests that Mn transport is similarly linked to laminar calcification dynamics. However, for B. marginata, Mn banding was sometimes anticorrelated with Mg banding, suggesting that (bio)availability, uptake, and transport of Mn differ from those forAmmonia sp. Our results from symbiont-bearing A. lessonii suggest that the activity of symbionts (i.e., photosynthesis/respiration) may influence the incorporation of Mn owing to alternation of the chemistry in the microenvironment of the foraminifera, an iimportant consideration in the development of this potential proxy for past oxygenation of the oceans.
Document type :
Journal articles
Complete list of metadatas

Cited literature [94 references]  Display  Hide  Download

https://hal.sorbonne-universite.fr/hal-02409107
Contributor : Hal Sorbonne Université Gestionnaire <>
Submitted on : Friday, December 13, 2019 - 12:00:46 PM
Last modification on : Saturday, October 24, 2020 - 4:12:02 PM

File

feart-07-00281.pdf
Publication funded by an institution

Identifiers

Citation

Inge van Dijk, Aurélia Mouret, Marine Cotte, Sandrine Le Houedec, S. Oron, et al.. Chemical Heterogeneity of Mg, Mn, Na, S, and Sr in Benthic Foraminiferal Calcite. Frontiers in Earth Science, Frontiers Media, 2019, 1, ⟨10.3389/feart.2019.00281⟩. ⟨hal-02409107⟩

Share

Metrics

Record views

143

Files downloads

193