Electron Spin Resonance dating of the southern Brazilian Pleistocene mammals from Touro Passo Formation, and remarks on the geochronology, fauna and palaeoenvironments

摘要

Quaternary mammals from Touro Passo Formation (southern Brazil, Rio Grande do Sul State) were studied in the 1970s and assigned to the Pleistocene/Holocene transition, approximately between 13,000 and 3500 BP. Subsequent dating by thermoluminescence indicated that the sediments of this formation are older, between 42 and 15 ka BP, and ages obtained by AMS in mollusks and 14C of charcoal ranged from 16 to 10 ka BP. However, none of these ages were obtained directly from vertebrates. In this work, four teeth samples of Artiodactyla indet., Gomphoteriidae indet. (2 samples, called Gl and G2) and Toxodon sp., from Ponte Velha I locality, Touro Passo Creek were dated by Electron Spin Resonance (ESR). The results are 34 ± 6 ka for Artiodactyla, 23 ± 5 ka for Gl, 28 ± 3 ka for G2 and 19 ± 3 ka for Toxodon sp. The variation in the ages of the materials corroborates the hypothesis that the fossils of Ponte Velha I locality have been reworked. The dating contributes to the chronology of the Brazilian Pleistocene mammals and corroborates the previous interpretations on the timing of deposition of Touro Passo Formation during the late Pleistocene.