Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration

Electron backscatter diffraction (EBSD) analysis enables a unique perspective of the internal microstructure of foraminiferal calcite. Specifically, EBSD provides crystallographic data from within the test, highlighting the highly organised “mesocrystal” structure of crystallographically aligned dom...

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Bibliographic Details
Published in:Biogeosciences
Main Authors: Procter, Frances A., Piazolo, Sandra, John, Eleanor H., Walshaw, Richard, Pearson, Paul N., Lear, Caroline H., Aze, Tracy
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2024
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article
Verlagsveröffentlichung
Planktonic foraminifera
Online Access:https://doi.org/10.5194/bg-21-1213-2024
https://noa.gwlb.de/receive/cop_mods_00072292
https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00070513/bg-21-1213-2024.pdf
https://bg.copernicus.org/articles/21/1213/2024/bg-21-1213-2024.pdf
Description
Summary:Electron backscatter diffraction (EBSD) analysis enables a unique perspective of the internal microstructure of foraminiferal calcite. Specifically, EBSD provides crystallographic data from within the test, highlighting the highly organised “mesocrystal” structure of crystallographically aligned domains throughout the test, formed by sequential deposits of microgranular calcite. We compared EBSD maps across the test walls of both poorly preserved and well-preserved specimens of the planktonic foraminifera species Globigerinoides ruber and Morozovella crater. The EBSD maps, paired with information about intra-test distributions of Mg/Ca ratios, allowed us to examine the effects of different diagenetic processes on the foraminifera test. In poorly preserved specimens EBSD data show extensive reorganisation of the biogenic crystal microstructure, indicating differing phases of dissolution, re-precipitation and overgrowth. The specimens with the greatest degree of microstructural reorganisation also show an absence of higher concentration magnesium bands, which are typical features of well-preserved specimens. These findings provide important insights into the extent of post-depositional changes, in both microstructure and geochemical signals that must be considered when utilising foraminifera to generate proxy archive data.

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