BioDose
2015
ESRdatingoftoxodontoothfromUpperRibeiraValley,SãoPaulo,
Brazil
Angela Kinoshita1,2, Aline Marcele Ghilardi3, Maria Elina Bichuette4, Marcelo Adorna Fernandes4, Ana
Maria G Figueiredo5, Oswaldo Baffa1
1
Universidade de São Paulo (USP), Ribeirão Preto, São Paulo, Brazil
2
Universidade Sagrado Coração (USC), Bauru, São Paulo, Brazil
3
Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Rio de Janeiro, Brazil
4
Universidade Federal de São Carlos (UFSCar), São Carlos, São Paulo, Brazil
5
Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Paulo, São Paulo, Brazil
Study Goal: The objective of this study was to use ESR to date a tooth of Toxodon found in Ribeira Valley,
São Paulo, Brazil.
Abstract: Electron Spin Resonance (ESR) dating was applied to date a sample of fossil tooth found in
Ribeira Valley, São Paulo, Brazil. This region is characterized by abundant fossil records of PleistoceneHolocene South American megafauna belonging to different faunistic moments related to climate changes
during the Quaternary (1). However, the number of fossils dated is not large. Thus, the dating of materials
from this region will provide important information to better understand the events associated to the
presence and extinction of these species. For the ESR dating, enamel was properly prepared, separated in
aliquots and irradiated with doses ranging from 0 to 200 Gy. The spectrum of irradiated enamel was
recorded in a Jeol X-Band Spectrometer and the peak-to-peak intensity of dosimetric signal g was
associated with additive dose for construction of the dose-response curve. The Equivalent Dose (De) was
determined using exponential fitting (2) resulting in (24±1) Gy. The De was converted in age using ESR
Dating program ROSY program (3) using the concentration of radioisotopes present in the sample and soil,
determined through Neutron Activation Analysis. The model "Combination Uptake" has been set with the
models "Early Uptake" to dentin and "Linear Uptake" to enamel, due to differences in porosity. Usually the
age provided by this model is adopted as being the most likely. Taking into account the uncertainty of the
age results, the ages provided by these 3 models are close and covers the range of 25 to 33ka. This
information is important to contextualize other findings in the region from different sites and help to obtain
better information about the climate changes in this region. Conclusion: The ESR dating resulted in an age in the range of 25 to 33 ka for the Toxodon tooth sample
found in Ribeira Valley cave.
Acknowledgements: To São Paulo Research Foundation - FAPESP, National Council for Scientific and
Technological Development - CNPq, for financial support.