Hello Matthew
Wim is quite right in saying that otoliths are chemically different from bone tissue. Otoliths are almost completely inorganic and do not contain proteins like collagene as bones do. The inorganic part is calcium carbonate in crystalline form, here as aragonite. Bones have calcium phosfate.
One site I have investigated on the Swedish west coast (called Huseby klev) was situated on a natural shellbearing sediment and the cultural layer also contained oysters and other molluscs (including terrestrial snails of genus Cepaea). The layer also contained thin strata of humic soil formed soon after the abanndonment of the settlement. When we excavated this site we could see that the quality of preservation varied very much and the distributions of bone, tooth enamel, otoliths and land snails were very patchy. Where otoliths occurred in high numbers bones were badly preserved. We found tooth rows of roe deer mandibles, teeth in anatomical order (only the enamel) but no cheek bone). In the same context otoliths were frequent. In layers with much fish bone and mammal bone otoliths were poorly represented. My belief is that there had been some sort of bacterial activity connected to the humic soil that had formed on top of the cultural layer degrading the proteins in bone rather than crystalline calcium carbonate in the otoliths.
Regards
Leif Jonsson
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