Palaeobotanical Evidence Of Wildfires In The Late Palaeozoic Of South America - Early Permian, Rio Bonito Formation, Parana Basin, Rio Grande Do Sul, Brazil

摘要

marginais à turfeira, até formas representativas de condições de solo mais bem drenado, com origem alóc-tone. Com base nas características litológicas e petrográficas das facies em que ocorrem os charcoal e também pelas características desses fragmentos preservados, foi possível definir que os incêndios que ocorreram na área de estudo restringiram-se ao dossel, sendo bastante intensos. Além disso, fica confirmado que incêndios vegetacionais ocorriam de modo bem mais freqüente do que se supunha até recentemente durante o Paleozóico Superior no continente Gondwana Ocidental, sendo que os dados aqui apresentados corroboram estudos anteriores os quais relatam a ocorrência de paleo-incêndios nesta porção de Gondwana durante este período, com base em estudos petrográficos de camadas de carvão.%Fossil charcoal, as direct evidence of palaeowildfires, has repeatedly been reported from several plant-bearing deposits from the Late Palaeozoic of the Northern Hemisphere. In contrast charcoal reports from the Late Palaeozoic deposits of the Southern Hemisphere are relatively rare in comparison to the Northern Hemisphere. Although the presence of pyrogenic coal macerals has repeatedly been reported from Late Palaeozoic coals from South America, no detailed anatomical investigations of such material have been published so far. Here is presented an anatomical analysis of charcoal originating from Early Permian sediments of the Quiteria Outcrop, Rio Bonito Formation, Parana Basin, located in the central-eastern portion of Rio Grande do Sul, Brazil. This charcoal comes from two different coaly facies, and it was possible to scrutinize between three types, based on anatomical characters of the charcoal. Two of these charcoal types can be correlated to gymnosperm woods, and the other type corresponds to strongly permineralized bark with characteristic features of lycopsids. The presence of charcoal in different facies, ranging from parautochtonous to allochtonous origin, indicates that different vegetation types, i.e. plants which grew under wet conditions in the lowland as well as in the more dry hinterland, have experienced wildfires. Taking into account previous petrographic and lithological analyses from the facies in which the charcoal occurs and from the conditions of the wood and bark fragments, it was possible to speculate that the intensity of such wildfires most probably corresponds to forest-crown fires. Moreover, it is possible to state that wildfires have been a more or less common element in distinct Late Palaeozoic terrestrial ecosystems in the South American part of Gondwana. The data support previous assumptions on the occurrence of wildfires in the Early Permian of the Parana Basin which were based solely on coal-petrographic data.