DISTRIBUTION AND ANALYSIS OF HOLOCENIC PEATY SEDIMENTS AT UPPER TIBAGI ALLUVIAL PLAIN, CAMPOS GERAIS, PARANÁ.

Abstract

Paleoenvironmental conditions resulting from Quaternary paleoclimatic and paleohydrological changes allowed the formation of peaty sediments in at upper Tibagi alluvial plain in the Late Holocene. We analyzed the distribution and fuel potential, and inferences about the paleoenvironmental conditions responsible for the deposition of these sediments. The peaty sediments tend to concentrate between altimetric quotas 775 and 780 m for about 12 km from the confluence of Gabiroba River and Tibagi River. The deposits showed ages between 3,220, 2,770 and 1,340 years BP (¹⁴C) and are distributed into approximately 10 km² through the alluvial plain. The sediments deposition occurred with the Tibagi River local base level about 2 to 4 meters higher than the current at 3,220 years BP under climatic conditions slightly drier than the present. Based on the extent and thickness of the deposit, it is estimated that paleomass would reach about 14.000.000 m³. The deposits presented high decomposition degree (H9 and H10) and ombrotrophic and mineralotrophic features. The low average levels of carbon and high mineral content made it impossible to be used as fuel. It is estimated that the burial of these deposits and incision occurred after 1,340 years BP., under wet climate, similar or close to the present conditions of temperature and humidity.