Electron Spin Resonance dating of the Late Quaternary megafauna fossils from Baixa Grande, Bahia, Brazil

摘要

Electron Spin Resonance (ESR) spectroscopy was applied to date megafauna fossil teeth of Stegomastodon waringi and Toxodontinae (two teeth) found in Baixa Grande, Bahia, Brazil. The CO_2 signal with spec-troscopic features g_⊥ = 2.0018 and g_‖ = 1.9973 used for ESR dating was detected in all fossil enamel. The additive method was employed to construct the dose response curve and to calculate the Equivalent Dose (D_e). Neutron Activation Analysis of enamel, dentine and soil where the samples were buried was used to determine the main radioisotopes concentration. These data were used in the conversion of D_e into age, using the ROSY ESR dating software. The results of age obtained were 50 ± 10 ka for S. waringi, and 43 ± 8 ka and 9 ± 2 ka for Toxodontinae teeth. Although Late Quaternary fossils from the extinct South American megafauna are relatively common in Brazilian's Northeast region, few geochronological studies were conducted. Thus dating samples found in this region will allow a better time and space understanding of that fauna.