GEOCHEMICAL ANOMALIES IN CORAL SKELETONS AND THEIR POSSIBLE IMPLICATIONS FOR PALEOENVIRONMENTAL ANALYSES

Different features are visible when thin sections and fragments of cor al aragonite are examined by transmitted light and scanning electron m icroscopy. The geochemistry of these areas was investigated by ion mic roprobe analysis. Microborings and centres of calcification (the origi ns of crystal growth) contained significantly higher concentrations of Ba and of Ba, Sr and Mg, respectively, than the surrounding crystal a reas. Geochemical anomalies in microborings may be associated with an amorphous lining observed in several of the boreholes. Centres of calc ification are more porous than the surrounding material and may contai n increased concentrations of the coral organic matrix which is enrich ed in many metals compared to the skeleton. Geochemical anomalies in t hese areas may significantly increase estimates of the Ba skeletal con tent and may effectively overwrite palaeoenvironmental signals. Mg and Sr anomalies would not significantly effect bulk determinations of th ese metals.