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Micro‐ to nanostructure and geochemistry of extant crinoidal echinoderm skeletons
Author(s) -
Gorzelak P.,
Stolarski J.,
Mazur M.,
Meibom A.
Publication year - 2013
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12012
Subject(s) - echinoderm , extant taxon , geology , paleontology , nanostructure , geochemistry , evolutionary biology , biology , materials science , nanotechnology
This paper reports the results of micro‐ to nanostructural and geochemical analyses of calcitic skeletons from extant deep‐sea stalked crinoids. Fine‐scale ( SEM , FESEM , AFM ) observations show that the crinoid skeleton is composed of carbonate nanograins, about 20–100 nm in diameter, which are partly separated by what appears to be a few nm thick organic layers. Sub‐micrometre‐scale geochemical mapping of crinoid ossicles using a N ano SIMS ion microprobe, combined with synchrotron high‐spatial‐resolution X ‐ray micro‐fluorescence (μ‐ XRF ) maps and X ‐ray absorption near‐edge structure spectroscopy ( XANES ) show that high Mg concentration in the central region of the stereom bars correlates with the distribution of S ‐sulphate, which is often associated with sulphated polysaccharides in biocarbonates. These data are consistent with biomineralization models suggesting a close association between organic components (including sulphated polysaccharides) and Mg ions. Additionally, geochemical analyses ( N ano SIMS , energy dispersive spectroscopy ) reveal that significant variations in Mg occur at many levels: within a single stereom trabecula, within a single ossicle and within a skeleton of a single animal. Together, these data suggest that physiological factors play an important role in controlling Mg content in crinoid skeletons and that great care should be taken when using their skeletons to reconstruct, for example, palaeotemperatures and Mg/Ca palaeo‐variations of the ocean.