0000000000165788
AUTHOR
Zengjie Zhang
Sr/Ca and Mg/Ca ratios of ontogenetically old, long-lived bivalve shells (Arctica islandica) and their function as paleotemperature proxies
International audience; The Sr/Ca and Mg/Ca ratios of many biogenic skeletons provide useful paleotemperature estimates. As yet however, it has remained largely impossible to obtain such information from bivalve shells. In the present study, metal-to-calcium values in the hinge plate (aragonite, outer shell layer) of four ontogenetically old (85 to 374 year-old) specimens of the long-lived bivalve, Arctica islandica, were measured on a LA-ICP-MS. The shells were collected alive in 1868, 1986 and 2003 from three different localities around Iceland. With increasing ontogenetic age and decreasing growth rate, a distinct trend toward increasing Sr/Ca (max. 5.17 mmol/mol) and Mg/Ca values (max. …
Crystal fabrics and element impurities (Sr/Ca, Mg/Ca, and Ba/Ca) in shells of Arctica islandica—Implications for paleoclimate reconstructions
Sr/Ca, Mg/Ca and Ba/Ca values are heterogeneously distributed in shells of Arctica islandica. These patterns are largely associated with crystal fabrics (size, habit and orientation of crystals) or the processes controlling them. The outer sublayer of the outer shell layer (oOSL; homogenous and irregular simple prismatic crystal fabrics,) contained element/Ca values up to 62% higher than the inner sublayer (iOSL; crossed-acicular, crossed-lamellar, fine crossed-lamellar and irregular simple prismatic crystal fabrics). A gradual decrease in Sr/Ca and Mg/Ca values was observed from the outer portions of the oOSL toward the oOSL/iOSL transition zone. This chemical shift was accompanied by a gr…
Effect of organic matrices on the determination of the trace element chemistry (Mg, Sr, Mg/Ca, Sr/Ca) of aragonitic bivalve shells (<i>Arctica islandica</i>)&mdash;Comparison of ICP-OES and LA-ICP-MS data
The element chemistry of biogenic carbonates can provide important data on past environments. However, the Sr/Ca and Mg/Ca ratios as well as the Mg and Sr concentrations of biological carbonates, especially aragonitic bivalves often depart from apparent thermodynamic equilibrium. When measured in situ by means of LA-ICP-MS, the Mg concentration is often substantially enriched (two- to threefold) near the organic-rich, annual growth lines. To test the hypothesis that some organic components exert a major influence on the skeletal metal content, the element chemistry of different shell components (insoluble organic matrix, IOM; dissolved CaCO3 and soluble organics, SOM) of Arctica islandica w…