Acknowledgements

The authors are grateful for support provided by FAPESP (grant numbers 96/4403-5, 97/06544-8, 97/1397-7, 93/4550-0, 01/04420 –7, 99/00358-3 and 00/03960-5) and CNPq (grant numbers 52.2388/95-7, 400490/94-3, 522386/95-4) to make this research possible, and to Artur Takashi Onoe of the Institute of Geosciences at USP for analyzing the 40Ar/39Ar samples for this study and to Daniel Godoy and Marli C. Ribeiro of the Institute of Geosciences at UNESP for drafting the figures. We thank Robert Ancskiewicz, Bruce Schaefer and Roberto Weinberg for detailed and careful review.