No / Small-scale heterogeneity of biogenic carbonate
elemental composition can be a significant source of error in
the accurate use of element/Ca ratios as geochemical proxies.
In this study ion microprobe (SIMS) profiles showed significant
small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca
ratios in new shell calcite of the marine bivalves Pecten
maximus and Mytilus edulis that was precipitated during a
constant-temperature culturing experiment. Elevated Mg/Ca,
Sr/Ca and Mn/Ca ratios were found to be associated with the
deposition of elaborate shell features, i.e. a shell surface stria
in P. maximus and surface shell disturbance marks in both
species, the latter a common occurrence in bivalve shells. In
both species the observed small-scale elemental heterogeneity
most likely was not controlled by variable transport of
ions to the extra-pallial fluid, but by factors such as the influence
of shell organic content and/or crystal size and orientation,
the latter reflecting conditions at the shell crystalsolution
interface. In the mid and innermost regions of the
P. maximus shell the lack of significant small-scale variation
of Mg/Ca ratios, which is consistent with growth at constant
temperature, suggest a potential application as a palaeotemperature
proxy. Cross-growth band element/Ca ratio profiles
in the interior of bivalve shells may provide more promising
palaeo-environmental tools than sampling from the outer
region of bivalve shells.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/4767 |
| Date | January 2009 |
| Creators | Clarke, Leon J., Kennedy, H.A., Richardson, C.A., Freitas, P.S. |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Article, No full-text in the repository |
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