Dados sobre as mudanças do clima e da vegetação da Amazônia durante o Quaternário

Abstract

The palynological investigation is discussed for Holocene sediment cores from five different sites in the Amazon basin. It is interpreted that the changes In the vegetation registered in the diagrams were due mainly to local processes of sedimentation and changes of water level. The pollen diagrams show successions in Alchornea, Symmeria, Myrtaceae, and Miconia play an important role. This reflects changes in the várzea and igapó forests. Other successions seem to be from open water via floating meadows (mainly of arasses) and Cecropia stands to várzea forest (Terra Nova diagram). Apparently lower effective precipitation in the Amazon basin was dated around and shortly after 4000 B.P. and 2100 B.P. (apparently the culmination of a relatively dry period between c. 2700 and 2000 B.P.), and around 700 B.P. (A.D. 1200). In other parts of tropical South America evidences of these "drier" intervals have been found (and dated) and seem to be regional phenomena.