INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Diagenetic analysis of therapsid from the Upper Triassic (Puesto Viejo Group) Mendoza, Argentina
DE LA FUENTE MARCELO SAÚL; MANCUSO ADRIANA CECILIA; PREVITERA ELENA
Congreso; 11º Congreso de la Asociación Paleontológica Argentina; 2016
Asociación Paleontológica Argentina
Non-mammalian therapsids dominated in terrestrial ecosystems during the late Paleozoic and early Mesozoic. Although cynodonts and dicynodonts have been studied from several perspectives, the relation between the specimens and their sedimentary context has been scarcely documented. This study is aimed to elucidate bone diagenesis in therapsids inparticular for specimens collected from the Late Triassic Puesto Viejo Group (Mendoza,Argentina). Bone histology and diagenetic features were analyzed through thin sections to interpret the degree of taphonomic alteration. The studied materials correspond to ribs and appendicular bones of cynodonts (MHNSR-PV 1159; 1160; 1162; 1164) and dicynodonts(MHNSR-PV 1161; 1163). Particularly, bones of Diademodon tetragonus Seeley, 1894(MHNSR-Pv 1164) from the Museo de San Rafael (Mendoza) collection were also study althought, information about their sedimentary context was not available. This sample was used to test the utility of our diagenetic approach to identify the facies context (depositionalframework) where the specimen was buried. Histological examination revealed a predominance of fibrolamellar tissue, intense Haversian remodeling and growth marks, thus suggesting adult individuals. Diagenetic processes inferred include substitution, fracturing, deformation, and different permineralization stages of iron carbonate minerals. Combined analyses including scanning electron microscopy (SEM-EDX), X-ray diffractometry (XRD)and petrography reveal the substitution of hydroxyapatite by francolite in the bone microstructure. The presence of fluoride-bearing apatite in therapsid bones is an indicator of diagenetic ion exchange through interaction with ground water, therefore, suggests a close link between the elemental composition and the depositional environment.