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.
The aim of the study is to evaluate the physical and chemical changes that occur on wood fragments submitted to different temperatures, verifying their influence on significant chemical characteristics in the forming process. Carbonization process in muffle associated to the techniques of Thermogravimetry, Fourier Transform Infrared Spectroscopy (FTIR) and multivariate analysis. The analyses were performed on 3 replicates for each burn temperature. The temperature of the thermal muffle process was in every 50 °C, from 200 °C to 600 °C. TGA were performed under nitrogen atmosphere, using a heating ramp from 25 °C min-1 to 995 °C. A range between 1900 to 650 cm-1 was used, with a resolution of 4 cm-1 and 64 scans. The PCA showed that it is possible to describe 95.73% of the data, grouping the samples into three main clusters. These clusters were used to build a SIMCA (Soft Independent Modeling of Class Analogy) model, enabling to predict with 100%. Results showed that technical associations, such as TGA, FTIR and multivariate analysis may help to characterize the natural carbonization process and, in future works, contribute to significant (paleo)environmental inferences.
Carvão vegetal macroscópico é amplamente aceito como um indicador direto da ocorrência de paleo-incêndios vegetacionais, sendo relativamente bem estudado e distribuído de forma homogênea em depósitos do Paleozoico Superior da Euramérica e Cataísia. Por outro lado, apenas alguns registros deste tipo de material foram publicados para o Paleozoico Superior do Gondwana e, somente recentemente foi demonstrado que carvão vegetal macroscópico (e, portanto, incêndios) também é comum no continente meridional. Os mais importantes registros do Gondwana se constituem em fragmentos carbonizados de lenhos gimnospérmicos e estão associados, principalmente, a depósitos de carvão mineral. Registros de macro-charcoal (carvão vegetal macroscópico) foram descritos para níveis do Paleozoico Superior da Bacia Damodar (Índia) e da Bacia do Paraná (Brasil), demonstrando que paleo-incêndios vegetacionais ocorriam em sequências e intervalos estratigráficos variados no Gondwana durante esse período. Com base nos registros publicados até o momento e em novos exemplares provenientes do nível de carvão Seam-IV, Formação Raniganj, Bacia Damodar (Lopingiano da Índia), uma revisão acerca dos registros indo-brasileiros de carvão vegetal macroscópico em níveis do Paleozoico Superior são apresentados. O material inédito foi analisado sob Microscópio Eletrônico de Varredura para a definição de características anatômicas, sendo estabelecida uma afinidade gimnospérmica para os fragmentos. Os dados apresentados reforçam a importância dos paleo-incêndios vegetacionais como elemento perturbador dos diferentes paleoambientes gondvânicos durante o Paleozoico Superior.
The reconstruction of past environments has been studied in several areas of science, aiming to help in understanding the several events that occurred on the planet. Plants are considered environmental markers and usually show structural adaptations that are characteristic of their habitat. Therefore, after passing through the charring process, they may not be completely consumed by the fire, being possible to find remnants of charcoal and other remaining materials. Based on this, the presence of charcoal is an evidence of the occurrence of current or past fires, contributing with a valuable source of (paleo) environmental proxy data. In this sense, the objective of this work is to assess the physical and chemical changes that occur on scraps of logs from Araucaria columnaris. It will be done during the charring process in muffle, at different temperatures, allowing us to assess important influences in relation to its forming process. The charring temperatures of the logs in natura were in a range of 50 to 1000 ° C, with ranging temperatures from 50 to 50 ° C, and heating ramp of 25 °C min-1. The analysis of this result seeks to allow the proposal of a methodology that assists in the characterization of the natural processes involved in the forming of this type of material, serving as a contribution to (paleo) environmental inferences.
Resumo:As análises arqueobotânicas compreendem uma vasta gama de atividades, sendo que dentre elas, o estudo de fragmentos de lenhos carbonizados é uma ferramenta importante para os estudos paleoambientais. Para entender o ambiente pretérito é importante conhecer a vegetação atual para reconstituir, fidedignamente, os paleoambientes. Dessa forma este trabalho visa contribuir para a construção de uma base de dados das características de carvões vegetais macroscópicos de espécies nativas da região do Vale do Taquari, Rio Grande do Sul. Para isso foram coletados exemplares atuais de 7 famílias, 9 gêneros e 9 espécies, cujos fragmentos foram envoltos em papel alumínio, colocados em cadinhos contendo areia e carbonizados artificialmente em forno mufla, em temperatura de 400ºC por 40 minutos. Após a carbonização, as amostras foram fotografadas e preparadas para análise em microscopia eletrônica de varredura para análise das estruturas celulares. Com as análises, foi possível perceber uma redução de, em média, 75,57% de massa das amostras após a carbonização em relação às amostras in natura. Os dados encontrados evidenciaram características anatômicas distintas entre as nove espécies estudadas. Para as duas espécies da família Moraceae, há diferença significativa para todos os parâmetros analisados, enquanto para as espécies de Myrtaceae, os parâmetros diâmetro das pontoações e altura de raios não foram significativos. Os resultados das medidas avaliadas demonstraram a necessidade de estudos detalhados de anatomia de carvão para a realização de comparações entre material atual e arqueológico para a reconstrução fiel da vegetação pretérita. Esses dados farão parte de um banco de dados antracológico regional, servindo de subsídio para estudos botânicos e arqueobotânicos. Os resultados advindos das análises comparativas futuras que utilizarem a base de dados lançada neste estudo, subsidiarão ações de gestão e planejamento ambiental que lidem com a recuperação da cobertura vegetal da região do Vale do Taquari.Palavras-chave: Paleobotânica. Antracologia. Rio Grande do Sul. Coleção de referência.
Abstract:Anthracological studies aim at the reconstruction of the paleoenvironment through the analysis and interpretation of macroremains of carbonized woods found in soils and archaeological sites that are related to previous human activities. The objective of this study was to compare the anthrocological and taphonomic data of the Archaeological Sites RS-T-101 and RS-T-114, located in the municipality of Marques de Souza, associated with pre-colonial occupancies of Guarani origin (archaeological sites RS-T-114 and RS-T-101, respectively, in 1,410-431 BP years and 1,411 -295 years BP, to build the environmental history of the Forqueta River basin based on taphonomic comparisons between these two sites. The traces analyzed were collected following methodology scaling and blasting, being conducted by the Archeology Section of the team's Museum of Natural Sciences of the UNIVATES University Center. In this work, the images of carbon obtained under SEM were analyzed from both sites, which were the object of previous anthrachological studies, being used to perform the taphonomic comparisons. From the images, it can be inferred that the recovered charcoals in
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