Geochemical anomalies in coral skeletons and their possible implications for palaeoenvironmental analyses

Different features are visible when thin sections and fragments of coral aragonite are examined by transmitted light and scanning electron microscopy. The geochemistry of these areas was investigated by ion microprobe analysis. Microborings and centres of calcification (the origins of crystal growth) contained significantly higher concentrations of Ba and of Ba, Sr and Mg, respectively, than the surrounding crystal areas. Geochemical anomalies in microborings may be associated with an amorphous lining observed in several of the boreholes. Centres of calcification are more porous than the surrounding material and may contain increased concentrations of the coral organic matrix which is enriched in many metals compared to the skeleton. Geochemical anomalies in these areas may significantly increase estimates of the Ba skeletal content and may effectively overwrite palaeoenvironmental signals. Mg and Sr anomalies would not significantly effect bulk determinations of these metals.