Study of fossil bones by synchrotron radiation micro-spectroscopic techniques and scanning electron microscopy

Abstract

Earlymost Villafranchian fossil bones of an artiodactyl and a perissodactyl from the Milia excavation site in Grevena, Greece, were studied in order to evaluate diagenetic effects. Optical microscopy revealed the different bone types (fibro-lamellar and Haversian, respectively) of the two fragments and their good preservation state. The spatial distribution of bone apatite and soil-originating elements was studied using micro-X-ray fluorescence (µ-XRF) mapping and scanning electron microscopy. The approximate value of the Ca/P ratio was 2.2, as determined from scanning electron microscopy measurements. Bacterial boring was detected close to the periosteal region and Fe bearing oxides were found to fill bone cavities, e.g. Haversian canals and osteocyte lacunae. In the perissodactyl bone considerable amounts of Mn were detected close to cracks (the Mn/Fe weight ratio takes values up to 3.5). Goethite and pyrite were detected in both samples by means of metallographic microscopy. The local Ca/P ratio determined with µ-XRF varied significantly in metal-poor spots indicating spatial inhomogeneities in the ionic substitutions. XRF line scans that span the bone cross sections revealed that Fe and Mn contaminate the bones from both the periosteum and medullar cavity and aggregate around local maxima. The formation of goethite, irrespective of the local Fe concentration, was verified by the Fe K-edge X-ray absorption fine structure (XAFS) spectra. Finally, Sr K-edge extended XAFS (EXAFS) revealed that Sr substitutes for Ca in bone apatite without obvious preference to the Ca1 or Ca2 unit-cell site occupation.

Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite

“…The XRF spectra were fitted with the WinQXAS package (Vekemans et al 1994) after taking into account corrections for escape peaks. The weight ratio, C A /C B , for two elements, A and B, was determined as in previous studies (Zougrou et al 2014).…”

Detailed spectroscopic study of the role of Br and Sr in coloured parts of the Callinectes sapidus crab claw

“…Since EXAFS is an element-specific non-destructive technique, it is suitable for the study of the bonding configuration of elements incorporated in the exoskeleton either as traces or at larger amounts. Sr is an element that commonly substitutes for Ca in biominerals (Bigi et al, 2007;Brizna et al, 2013;Doubleday et al, 2013;Foster et al, 2009;Lavalli and Spanier, 2007;Tester et al, 2013;Zougrou et al, 2014). Although Sr plays an important role in the nucleation of aragonite vs. calcite (Siegel 1960;Sunagawa et al, 2007) and shows a preference for aragonite (Taft, 1967) most probably due to the larger volume that is available, substitution of Ca by Sr in both aragonite and calcite has been reported by Fins and Allison (2007).…”

What the skull and scapular morphology of the dugong (Dugong dugon) can tell us: sex, habitat and body length?

“…Body length in Sirenia is widely used for estimating body weight 33, 34 and maturation 22, 35 . A previous study demonstrated a correlation between skull measurements, body length and field weight in Florida manatees 36 .…”