| Abstract: |
In experiments on marine animal fossils that had been buried in terrestrial sediments, Nelsonet al.(1986,Geochimica et Cosmochimica Acta50:1941-1949) reported that the strontium (Sr) of prehistoric bone had nearly completely exchanged with that of the burial environment, and therefore cannot be used for paleodietary reconstruction. However, Sealyet al.(1991,Journal of Archaeological Science18:399-416), using a solubility profile procedure, reported that it was possible to remove diagenetic Sr and obtain biologically meaningful Sr. Nevertheless, the Nelsonet al.study is often cited as evidence that a biological signal is irretrievable. Here infra-red spectrometry, XRD spectrometry and elemental analyses were used to compare the effects of the Nelsonet al.protocol with the solubility profile protocol on the crystal structure and crystallinity of the bone and fossil specimens. The results show that the procedures used by Nelsonet al., which include a preliminary ashing step, result in severe recrystallization of apatite both before and during the leaching step, which deleteriously affects any attempt to recover biological Sr. By contrast no observable recrystallization takes place in the solubility profile procedure. The results imply that the conclusions reached by Nelsonet al.are primarily artefacts of the specific methods used in their study, rather than due to any inherent mechanism of diagenesis. Spectrometry and elemental analysis were used to compare the effects of the Nelson <i>et al. (1966)</i> protocol with the solunbility profile protocol on the crystal structure and crystallinity of the bone and fossil specimens. The results imply that the conclusions reached by Nelson et al. are primarily artifacts of the specific methods used in their study, rather than due to any inherent mechansim of diagenesis. Nelson et al used a leaching process of 50:50 Glacial aceic acid: water while Sealey et al. used a Acetate buffer, pH 4.5) The procedures used in Nelson et al (1986) leaching experiment result in severe alerations in the crystallinity and crystal structure of fossil bones \ibefore and during\i the leaching experiment.
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