Evolução do relevo da região do planalto de Poços de Caldas

Correlações entre níveis planálticos e termocronologia por Traços de Fissão em Apatitas

Abstract

Research about the geomorphological evolution of southeast of Brazil has been done in a couple of years with the support of new technologies and more precise datations. Indeed it is possible to observe that erosional surfaces, specially the Sul-Americana and Japi, are being again target of research and discussions, mainly, about the issue of the age. Therefore, on the Poços de Caldas Alkaline Massif region there are evidences of those erosional surfaces, as pointed out by King (1956), Almeida, (1964), Melo & Ponçano (1993), which motivated to correlate geomorphological data with low temperature thermochronology, as apatite fission tracks (AFT) with the main of having effective results that allow to confirm the earliest age of the erosional surfaces that exist in this area. Tree levels of surfaces were established in the area, using geomorphological methods where it was possible associate two of them with the ages and the thermal histories obtained by the Fission Track Analysis. The samples collected in the Low Level (900-560m) and in the Intermediate Level (1200-900m) are from the Juro-Cretaceous period, and the ages obtained in the Upper Level (up to 1200m) are from the Late Cretaceous and Paleocene. Although the AFT method register the ages when the rock passed through the 120ºC isotherm, which means, in ~3km of deep, so that age registered is not the absolute age and the maximum age of the surface.