INTEGRATING FOSSILDIAGENESIS AND GEOCHEMISTRY IN THE PALEOENVIRONMENTAL RECONSTRUCTION OF A TANK DEPOSIT BEARING QUATERNARY VERTEBRATES IN NORTHEASTERN BRAZIL

Abstract

In this work, we studied the fossil diagenesis of vertebrates recovered from a quaternary tank deposit at Taperoá, Paraíba State, northeastern Brazil. The samples were classified based on the staining pattern and examined using petrography, fluorescence (XRF), and X-ray diffraction (XRD) analyses. A principal component analysis (PCA) was used to verify the relationship between the staining and chemical composition of the fossils. Microfractures, microcrackins, permineralization, and replacement were observed, although the bone microstructure was well-preserved. The XRF analysis showed that the specimens with the highest percentage of manganese and iron appeared darkest (black and red shades, respectively), which the PCA confirmed. The variation in rare earth elements (REE) values indicates the occurrence of temporal mixing. The XRd analysis showed a predominance of hydroxyapatite; therefore, fossils may preserve the original mineral composition. Root marks and sun exposure bleaching were also observed, which suggested reworking and temporal mixing. Thus, we conclude that the tank deposit of Taperoá underwent different environmental conditions, from oxidising to reducing and wet to dry conditions, which caused diagenetic differences and represent a typical setting for tank deposits. This confirms the seasonality of the semi-arid climate of the Brazilian Intertropical Region (RIB) during the Pleistocene epoch.