Geochemical and microstructural characterisation of two species of cool-water bivalves (<i>Fulvia tenuicostata</i> and <i>Soletellina biradiata</i>) from Western Australia
The shells of two marine bivalve species (<i>Fulvia tenuicostata</i> and <i>Soletellina biradiata</i>) endemic to south Western Australia have been characterised using a combined crystallographic, spectroscopic and geochemical approach. Both species have been described previo...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-03-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/14/1721/2017/bg-14-1721-2017.pdf |
| Summary: | The shells of two marine bivalve species (<i>Fulvia tenuicostata</i> and
<i>Soletellina biradiata</i>) endemic to south Western Australia have been
characterised using a combined crystallographic, spectroscopic and
geochemical approach. Both species have been described previously as purely
aragonitic; however, this study identified the presence of three phases,
namely aragonite, calcite and Mg-calcite, using XRD analysis. Data obtained
via confocal Raman spectroscopy, electron probe microanalysis and laser
ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) show
correlations between Mg ∕ S and Mg ∕ P in <i>F. tenuicostata</i>
and between Sr ∕ S and S ∕ Ba in <i>S. biradiata</i>. The
composition of the organic macromolecules that constitute the shell organic
matrix (i.e. the soluble phosphorus-dominated and/or insoluble
sulfur-dominated fraction) influences the incorporation of Mg, Sr and Ba into
the crystal lattice. Ionic substitution, particularly Ca<sup>2+</sup> by Mg<sup>2+</sup>
in calcite in <i>F. tenuicostata</i>, appears to have been promoted by the
combination of both S- and P-dominated organic macromolecules. The elemental
composition of these two marine bivalve shells is species specific and
influenced by many factors, such as crystallographic structure, organic
macromolecule composition and environmental setting. In order to reliably use
bivalve shells as proxies for paleoenvironmental reconstructions, both the
organic and inorganic crystalline material need to be characterised to
account for all influencing factors and accurately describe the <q>vital
effect</q>. |
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| ISSN: | 1726-4170 1726-4189 |