Mineralogical Studies On Bone Apatite and Their Implications for Radiocarbon Dating

Abstract

ABSTRACT. Infrared (IR) spectrophotometry and X-ray diffraction (XRD) were conducted on modern and fossil bone material from archaeological sites in the U S to determine post-mortem changes in bone apatite and to evaluate the effect of these changes on radiocarbon dating. IR absorption bands, XRD peak-broadening parameters, and XRD unit cell measurements indicated that during fossilization, bone apatite, a mineral similar to dahllite, was partially or completely recrystallized to francolite. Post-mortem changes involved then removal of some of the endogenous crystal carbonate both at surfaces and at internal OH-sites and introduction of exogenous carbonate into internal crystal P04 sites. Increased fluorine content accompanied carbonate substitution.Both the carbon isotopic composition and the amount of exogenous carbonate introduced into the apatite structure will affect the radiocarbon dating of bone apatite. Special sample pre-treatment may remove most of the substituted carbonate in some cases. Simulated experiments are suggested for a better understanding of the nature and mechanism of carbonate substitution in bone apatite for the removal of the exogenously substituted carbon and the improvement of radiocarbon dates.

Pre-Neolithic wild boar management and introduction to Cyprus more than 11,400 years ago

“…Bioapatite contains about 1 wt % carbon in the form of carbonate ions, which substitute for phosphate and can be used for 14 C dating. The suitability of this inorganic carbon for radiocarbon dating was suggested a long time ago (35), and it was successfully applied to bones found in sub-Saharan environments (36,37). In the absence of tooth enamel, calcined bones are the best candidate for 14 C dating (22).…”

Radiocarbon Dating of Bone Apatite Using Thermal Release of CO2

“…The procedures recommended by Termine and others (1973) and by Hassan (1976) Figure 1 indicate that a small sample of CO2 gas can be collected above 800° which stems mainly from original bone apatite. Thus, it should yield the most reliable age date obtainable with this material.…”

“…It is assumed that early reactions remove residual calcite and weakened bone structure with exchanged carbon content. The last carbon dioxide fraction is most likely to yield the most reliable age date (Haynes, 1968;Hassan, 1976). Satisfactory results from this dating process can be expected only with the assumption of simultaneous exposure of all surfaces of the internal bone structure to the acid solutions utilized.…”

“…The size of these crystals has been estimated to be less than 1000 A (Hassan,538 Dating Various Materials Termine, and Haynes, 1977;Eanes, 1973). Obviously, hydrolysis by layers along the surface of individual crystals is not possible; instead, the reaction proceeds along the surfaces created in the grinding process.…”

14C Dating of Cremated Bones: The Issue of Sample Contamination

“…It has long been common knowledge in 14 C dating laboratories that bone apatite is not a good dating material because of sample contamination (Berger et al 1964;Tamers and Pearson 1965;Hassan et al 1977). This comes from direct contact by the bone with the total dissolved inorganic carbon (TDIC) from groundwater.…”