Palynological data on a holocene peat deposit in tropical Brasil: preliminary paleoclimatic and paleoecological interpretations

Abstract

In the Campos do Jordão Plateau, the slopes show at least three generations of erosion amphitheaters. Amphitheater genesis would reflect a succession of deep mass movements related to Pleistocene incision phases of tectonic character and to climatic fluctuations - probably during the transition to drier climates contemporaneous of the last two glaciations of the northem hemisphere. In the Holocene, climatic fluctuations and uplift rhythm lessened; colluvia on slopes point to less intense erosive phenomena. Pleistocene evolution of slopes, resulting in marked environmental contrasts, determined the distribution of vegetation on slopes and the organization of the forest-grassland mosaic. Palynology of a Holocene peat deposit shows changes in the plateau vegetation from 4,170 years BP, probably linked to climatic variations. Adjustment of plant formations to variable temperature and moisture conditions would have modified the composition of forest and grassland communities. These modifications would reflect the transition from warmer and perhaps drier Middle Holocene climates to the present climate of the plateau, characterized by lower temperatures and more homogeneous rainfall distribution.