M.M Coimbra

The antiquity of the prehistoric settlement of the central-south Brazilian coast

We discus here the prehistoric settlement of the central-south Brazilian coast, and, more specifically, 1 old radiocarbon date obtained for a coastal shellmound, as well as its implications concerning the chronology attributed to the settlement process. The accelerator mass spectrometry (AMS) technique was used to determine the (super 14) C age of charcoal from a shellmound on the southern coast of Rio de Janeiro. The resulting age was 7860+ or -80 BP, an unexpected result that reinforces 2 similar previously obtained dates for the same region. Brazilian archaeologists, however, have questioned those 2 dates, because they would predate by some 2000 yr the antiquity consensually accepted for the settlement of the central-south Brazilian littoral.

AMS dating of early shellmounds of the southeastern Brazilian coast

This paper discusses the chronology of prehistoric settlements of the central-south Brazilian coast. A charcoal sample from a coastal shellmound of Rio de Janeiro State was dated by 14C-AMS to 7; 860§ 80 years BP as part of an interdisciplinary project between physicists and archaeologists. This is an unexpected result that reinforces two similar previous early dates for the same region, which were questioned by Brazilian archaeologists because they implied in pulling back by some two thousand years the antiquity consensually accepted for the settlement of that region.

Brazilian accelerator mass spectrometry program

Abstract The present status of the Brazilian AMS program, based on the University of Sao Paulo 8UD tandem accelerator, is described. Results of tests and developments on voltage stability, focusing, automatic system for changing beams and detection system are presented. 36Cl and 26Al beams have already been successfully accelerated and detected.

The Brazilian Bragg curve detector built for AMS studies

A Bragg curve detector (BCD) has been designed and built to be used for AMS purposes. Its design is described and its performance, obtained in tests at the Australian National University (ANU), is reported. At a 36 Cl energy of 154 MeV, the energy resolution was found to be 0.38%, and the charge resolution 1.3%. The 36 Cl and 36 S are completely discriminated. Good separation was also achieved at 64 MeV, and a measurement at this energy of the 36 Cl/Cl ratio of a sample measured previously at 154 MeV with the standard ANU ionization detector agreed well with the earlier value. This very simple detector has been shown to be suitable for use in AMS programs. ” 2000 Elsevier Science B.V. All rights reserved.

Current status of the Brazilian AMS program

The status and the near future plans for the Brazilian AMS program are described. The 8 MV Tandem accelerator at the University of Sao Paulo (USP) is ready to measure standard AMS samples. A recently installed 1.7 MV Tandem at the University of Rio de Janeiro will have a 14C AMS line. Together with external laboratories, we developed some projects on paleoclimatic and maritime geology. During these studies we have also learned sample preparation procedures.