Serra de André Lopes Tufa (SP): distribution, genesis and paleoclimatic record

Abstract

Tufa deposits, possibly of quaternary age, occur in Serra do André Lopes, in the Ribeira Valley (São Paulo State), associated with karst system developed upon proterozoic carbonate rocks. The origin of tufa deposition is due to association between the high content of calcium carbonate dissolved in water and the biological activity. In Brazil the deposition of ancient and active tufa is uncommon and often the deposits are exploited economically. In Serra do André Lopes are known two occurrences of tufa, described briefly in geological mapping projects, which indicated a quaternary age without absolute dating. It is intended to this project get support for the geological studies of tufa, the geological mapping, proposition of the unit, the study of the origin of tufa, the palaeoenvironmental conditions, the relationship with the kasrt system, the age of the deposits, correlations with other deposits and the patterns of paleoclimatic variations for the period of deposition. For the study of tufa deposits will be realized field works, with collection of samples, construction of sections and geological mapping, and laboratory studies, such as textural, mineralogy and geochemistry analysis and radiocarbon absolute dating. Given the few studies about the tufa of Serra de André Lopes, the major results of this project will be to obtain paleoclimatic and palaeoenvironmental informations especially using isotopic and geochemical data, besides fossils and geochronology. (AU)