Biological mineral content in Iberian skeletal cremains for control of diagenetic factors employing multivariate statistics

Journal of Archaeological Science (Impact Factor: 2.2). 02/2013; 40(5). DOI: 10.1016/j.jas.2013.01.022


The aim of this study was to define a strategy for a correct selection of bone samples by employing inductively coupled plasma optical emission spectroscopy (ICP-OES) for reconstructing the biological mineral content in bones through the determination of major elements, trace elements and Rare Earth Elements (REE, lanthanides) in skeletal cremains of ancient Iberians (III–II B.C), discovered in the Necropolis of Corral de Saus (Moixent, Valencia) between 1972 and 1979. The biological mineral content was determined taking into account diagenetic factors. A control method for a better reading of results was applied. To explore large geochemical datasets and to reduce the number of variables, Principal Component Analysis (PCA) was used, thus, providing a deeper insight into the structure of the variance of the dataset. PCA shows that the elemental profiles of bone and soil samples are clearly different. Bone samples obtained from the outer bone layer were shown to have a different elemental composition; more similar to soil samples than samples of the inner bone layer. PCA scores and loadings plots were preferred to dendrograms obtained using Cluster Analysis, due to the limits of the latter one to appreciate the spatial ordering of samples. Partial least squares discriminant analysis (PLS-DA), a frequently used supervised classification method, was applied to differentiate between degradation states of bone samples. PLS-DA results obtained in this study confirmed that changes derived from different burning conditions were associated with transformations in the mineral part of the bones. Accordingly, carbonized bones can be differentiated from cremated bones. Class assignment of bone samples with uncertain thermal conditions in dependence on their elemental composition has shown to be feasible. Consequently, for biochemical-archaeological studies the analysis and statistical classification of carbonized and cremated archaeological bones, as well as those exposed to unknown thermal conditions together with experiments in modern bones, are recommended.

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Available from: Joan Bernabeu Auban, Feb 15, 2014
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    ABSTRACT: Abstract The aim of the present study was to define a methodological strategy for understanding how post- mortem degradation in bones caused by the environment affects different skeletal parts and for selecting better preserved bone samples, employing rare earth elements (REEs) analysis and multivariate statistics. To test our methodological proposal the samples selected belong to adult and young individuals and were obtained from the Late Roman Necropolis of c/Virgen de la Misericordia located in Valencia city centre (Comunidad Valenciana, Spain). Therefore, a method for the determination of major elements, trace elements and REEs in bone remains has been developed employing Inductively-Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) and ICP- Mass Spectrometry (MS). Bone samples, mainly rib and femur, from seventy-four individuals have been studied. Principal Component Analysis (PCA) was employed to facilitate the interpretation of the taphonomic processes. A multivariate classification model employing Partial Least Squares Discriminant Analysis (PLSDA) was used to identify bones with less soil contamination. These preliminary results show that statistical analysis can help to classify different bones according to their elemental profile at intraskeletal levels smoothing the way for the identification of better preserved samples. Zn/Ca and Sr/Ca parameters show that diet profiles of a population could change depending on the type of bones analyzed. The proposed method could be useful in forensic science investigations to select better preserved samples in different scenarios.