Nelson Vicente Lovatto Gasparetto

DISTRIBUIÇÃO E ANÁLISE DE SEDIMENTOS TURFOSOS HOLOCÊNICOS NA PLANÍCIE DO ALTO TIBAGI, CAMPOS GERAIS, PARANÁ.

Condicoes paleoambientais resultantes de mudancas paleohidrologicas e paleoclimaticas quaternarias propiciaram a formacao de depositos turfosos na planicie aluvial do alto Tibagi no Holoceno Inferior. Foram analisadas a distribuicao e o potencial combustivel, alem de inferencias sobre as condicoes paleoambientais responsaveis pela deposicao desses sedimentos. Os sedimentos turfosos tendem a se concentrar entre as cotas 775 e 780 m, por cerca de 12 km a partir da confluencia do rio Gabiroba com o rio Tibagi. Os depositos apresentaram idades entre 3.220, 2.770 e 1.340 anos AP (14C) e distribuem-se por cerca de 10 km² pela planicie aluvial. A deposicao desses sedimentos se deu com o nivel de base local do rio Tibagi cerca de 2 a 4 metros mais elevados que o atual, ha cerca de 3.220 anos AP, sob condicoes climaticas ligeiramente mais secas que as atuais. Com base na extensao e na espessura media do deposito, calcula-se que o volume chegaria a 14.000.000 m³ no passado. Os depositos apresentaram elevado grau de decomposicao (H9 e H10) e caracteristicas ombrotroficas e mineralotroficas. Os baixos teores medios de carbono e o elevado conteudo mineralogico inviabilizam o uso como combustivel. Estima-se que o soterramento e o entalhe desses depositos foram posteriores, ha 1.340 anos AP, sob clima umido, semelhante ou proximo das condicoes climaticas atuais de temperatura e umidade. Palavras-chave: mudancas paleoambientais; sedimentos turfosos; Holoceno Inferior ABSTRACT Distribution and analysis of holocenic peaty sediments at upper Tibagi alluvial plain, Campos Gerais, Parana. 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. Key words : paleoenvironmental change, peaty sediments, Lower Holocene

O Emprego de Minerais Pesados como Indicador da Proveniência da Cobertura Pedológica do Arenito Caiuá na Região Noroeste do Paraná

This paper aims the identification of the translucent heavy minerals that occur in the pedological covering at the northwestern region Parana state (Brazil), and compare them to the minerals observed in the Caiua sandstone that orverlies it. The origin of the pedological covering is controversial because many researches consider it to be colluvium, originated during a semi-arid climate that occurred in the Quaternary. To reach the proposed goals, morphological descriptions along the top sequences were done and samples from different profiles of the trenches were collected. A slight mineralogical diversity was observed at the pedological covering and at the Caiua sandstone, where the main minerals are staurolite, rutile, tourmaline and zircon, followed by lower amounts of garnet, kyanite and dumortierite. This assemblage of minerals suggests a high textural and mineral maturity of the studied materials. It is an important argument concerning the origin of the pedological covering, suggesting that it was derived from the alteration processes of the overlaying sandstone, thus, confirming the residual characteristics of said materials in northwestern Parana state