Assessing the preservation of biogenic strontium in fossil bones and tooth enamel

Analyses of the strontium isotope ratio (Sr-86/Sr-87) of vertebrate fossils can provide information about palaeobiological attributes such as habitat use and movement patterns. Diagenetic contaminants can alter the Sr-87/Sr-86 ratio of fossils, however, complicating palaeobiological interpretations. Several pretreatment protocols have been developed to separate diagenetic contaminants from biogenic Sr. While the methods can remove some diagenetic Sr, it has not been shown that any technique removes all contamination. The extent to which pretreatment removes diagenetic Sr can be quantified through analysis of the (87)/Sr/Sr-86 ratios of fossil marine mammal bones and teeth buried in sediments with non-marine diagenetic Sr-87/Sr-86 signatures. To do this, we examined Holocene seals recovered from archaeological sites in Greenland and California, as well as a Miocene whale from Maryland. Our results demonstrate that although pretreatment eliminated some contaminants from bone, a large percentage (up to 80%) of diagenetic Sr remained after treatment. In contrast, pretreatment does appear to remove nearly all (greater than or equal to similar to 95%) diagenetic Sr from tooth enamel.