Paleoclimatic reconstitution of River Caí valley, northeastern Rio Grande do Sul, with emphasis on human occupation

Abstract

Palynological analysis of a core from Caí River Valley, northeastern Rio Grande do Sul (Brazil) has shown the record of environmental changes. Samples were treated with HCL, KOH, HF and acetolysis. For each sample a minimum of 300 grains of pollen was counted. The results show at around 1,260 years BP the region occupied by grassland under a dry climate, with a later increase in forest areas at around 1,000 to 600 years BP, when fires occurred, probably originating from human activities. From 600 years BP to the present humidity and temperature increased, and climate became similar to today. Paleoenvironmental data suggest that both grassland and forest areas have been exploited by pre-colonial human population.