No abstract

Fossil charcoal has been discovered in the Faxinal Coalfield, Early Permian, Rio Bonito Formation, in the southernmost portion of the Paraná Basin, Brazil. Three types of pycnoxylic gymnosperm woods recovered from a single tonstein layer are described and confirm the occurrence of paleowildfire in this area. A decrease of the charcoal concentration from the base to the top within the tonstein layer indicates that the amount of fuel declined during the deposition probably due to the consumption of vegetation by the fire. The presence of inertinite in coals overlying and underlying the tonstein layer indicates that fire-events were not restricted to the ash fall interval. The integration of the new data presented in the current study with previously published data for the Faxinal Coalfield demonstrates that volcanic events that occurred in the surrounding areas can be identified as one potential source of ignition for the wildfires. The presence of charcoal in Permian sediments associated with coal levels at different localities demonstrates that wildfires have been relatively common events in the peat-forming environments in which the coal formation took place in the Paraná Basin.

Resumo: Neste artigo foram analisadas as relações espaciais e temporais da ocupação Guarani pré-colonial na Bacia do RioTaquari/Antas a partir da delimitação do perímetro da ocupação e seu estabelecimento na paisagem, da cronologia intrasítio e regional e de discussões referentes às movimentações espaciais. A partir dos resultados foram mapeados 121 sítios Guarani na porção centro-sul da Bacia, em um perímetro de várzeas que circundou as terras altas do Planalto das Araucárias, demonstrando tratar-se de uma ocupação regional longa, entre os séculos XIV e XVIII. O estabelecimento teria ocorrido a partir da conexão entre o Rio Jacuí e o Rio Taquari/Antas, em uma expansão compulsória do sul para o norte, observando-se assentamentos contemporâneos em todo o perímetro e sítios com fatores de alta permanência. Tal dinâmica justificar-se-ia a partir de um controle consciente do ambiente, permitindo, por um lado, a manutenção das aldeias, e, por outro, o crescimento demográfico e novas expansões. Além da motivação demográfica, inferiu-se a possibilidade de que os limites da ocupação Guarani na região tenham sido estabelecidos de forma igualmente consciente a partir de um pulso de expansão inicial e posterior estabilidade, configurando-se a ocupação compulsória como uma estratégia de manutenção política do território.Palavras-chave: Arqueologia Guarani. Terras baixas da América do Sul. Bacia do Rio Taquari/Antas. Análise espacial. Cronologia. Abstract:This study examines spatial and temporal relations of pre-colonial Guarani occupation in the Taquari/Antas River Basin.The perimeter of occupation and itsestablishment inthe landscapeare discussedas well as local and regional chronology and migrations. The data wereused to map 121 Guarani sites in the center-south portion of the river basin, in a perimeter of lowlands surrounding the highlands of the Plateau of the Araucarias.Results show that therewas a long regional occupation between the 14 th and 18 th centuries. The Guarani settlementsin this region occurred at the confluenceof the Jacuí and Taquari/Antasrivers, in a forcedexpansion from south to north, where contemporary settlements can be observed throughout the perimeter, and sites show evidence of longpermanence. Such dynamics can be understood as forms ofenvironmentmanagement, enabling village maintenance , allowing demographic growth and furtherexpansion. Apart fromdemographic motivation, the regional limits of the Guarani occupation were probably defined consciously, after an initial expansion impulse and ensuingstability, which must have defined forcedoccupation as a strategy of territorial politics.

Charcoal is widely accepted as evidence of the occurrence of palaeo-wildfi re. Although fossil charcoal remains have been used in many studies, investigation into the anatomical changes occurring during charring are few. Th e present study analyses changes in selected anatomical characters during artifi cial charring of modern wood of three species of the genus Araucaria (i.e. Araucaria angustifolia, Araucaria bidwillii and Araucaria columnaris). Wood samples of the studied species were charred under controlled conditions at varying temperatures. Measurements of anatomical features of uncharred wood and artifi cial charcoal were statistically analysed. Th e anatomical changes were statistically correlated with charring temperatures and most of the parameters showed marked decreases with increasing charring temperature. Compared to the intrinsic variability in anatomical features, both within and between growth rings of an individual plant, the changes induced by temperature account only for a comparatively small percentage of the observed variability. Regarding Araucaria charcoal, it seems possible that at least general taxonomic and palaeoenvironmental implications can be drawn from such material. However, it is not clear so far whether these results and interpretations based on only three taxa, can be generalized for the entire family and anatomically similar fossil taxa or not.