However, for the extraction of the Casubstituting
fraction, Shen and Boyle (1988) developed an intense
cleaning protocol consisting of a series of oxidation, reduction and
weak acid treatments, in order to eliminate trace elements, including
Ba, associated with the interchangeable, organic, and authigenic
fractions. Thus, the only trace elements that remained in samples
were those that substituted for Ca in the coral skeletal carbonate