INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
PRELIMINARY CHEMOMETRIC STUDY OF BONE DIAGENESIS OF EARLY TRIASSIC CYNODONTS FROM MENDOZA, ARGENTINA.
PREVITERA ELENA; D'ANGELO JOSE; MANCUSO ADRIANA
ASOCIACION PALEONTOLOGICA ARGENTINA
Lugar: Buenos Aires; Año: 2013 p. 460 - 460
The non-mammalian therapsids dominated the terrestrial ecosystems during the Late Paleozoic-Early Mesozoic. The cynodonts have been studied from a taxonomic, osteologic, and morphology perspective. However, taphonomy using chemometrics has been poorly researched. This report includes a rib and an appendicular bone of cynodonts from the Puesto Viejo Group (Mendoza, Argentina). These fossils are studied for the first time using SEM-EDX. Semi-quantitative data derived from SEM-EDX spectra is evaluated by principal component analysis to gain new insights regarding the differing diagenetic pathways the bone microstructure. The multivariate model supports the distinction of different sample areas (bone, transition zone and rock matrix), in terms of chemical parameters. Differentiation is based mainly on varying contents of Ca, P, F, Si, Al, K, O, Mn and Fe. Variable concentrations of Fe and Mn could be related to different facies (floodplain and crevasse splay). These results along with thin section petrographical analysis confirm in one of the cases the substitution of hydroxyapatite by fluorapatite into the bone microstructure. Fossildiagenetic processes observed herein include substitution, fracturing, brittle deformation and different permineralization events. Permineralization stages include infilling of hematite, manganite and calcite, in vascular canals, trabeculae and fractures, during the burial history. The presence of calcite and iron enrichment indicates local reducing conditions under the water table during precipitation. This chemometric approach to the study of Triassic cynodont remains proved useful to value the chemical pathways changing the bone microstructure.