Interpretações paleoambientais e paleoecológicas para o Cretáceo da Bacia do Tacutu com base em Lenhos

• Autor(a) principal: Santos, Ângela Cristine Scaramuzza dos
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFRR
• Texto Completo: http://repositorio.ufrr.br:8080/jspui/handle/prefix/123
• topic: Paleobotânica; Gimnospermas; Bacia do Tacutu; Paleoecologia; Paleobotany; Gimnosperms; Tacutu Basin; Paleoecological; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::PALEOBOTANICA

The paleobotany studies fossil plants, including the wood, which in turn provide important information about the evolution of life on Earth, as well as assist in paleoecological interpretations, paleoenvironmental, paleoclimatic and biostratigraphic. This study aims to identify and draw inferences about the paleoecology of fossil wood of the Tacutu Basin, and its stratigraphic context. Seven specimens were analyzed, six coming from the Tacutu River and founded the Morro do Tiro in the Serra do Tucano. For the analysis of the samples, flat sections and thin sections were prepared in three sections (transverse, radial longitudinal and tangential longitudinal) of the specimens studied. The wood of both locations showed affinity with the group of gymnosperms, possibly of the order Coniferales. Only one specimen of the Tacutu River was possible to identify precisely the order Coniferales, Cheirolepidiaceae Family, Brachyoxylon genre. Growth rings true and false rings were found in a specimen Tacutu River, however, the predominance were wood with continued growth, found in both locations. Also observed were small gaps along the cross section as well as the presence of black spots within the lumens of the tracheids, these features here assigned to the plant response to phytophagous attacks. The wood previously described as coming from Tacutu Formation were found deposited in a paleopaviment the banks of the Tacutu River and are hereby assigned to the Boa Vista Formation of Cenozoic age. The taxonomic identification, however, suggests that the logs are of Cretaceous age, indicating that possibly they were reworked and deposited at a younger unit, a fact corroborated by taphonomic features. Regarding the pattern of growth rings with predominance of type "O”, it was possible to suggest for specimens of Tacutu River an equatorial / tropical paleoclimate. However, the occurrence of a specimen with pattern of type "D" indicates characteristics of a paleoclimates dry with wet summers. The only specimen of the Serra do Tucano also presents growth pattern of type "O” suggests an equatorial / tropical paleoclimate. The gaps caused by fungi indicate the presence of humidity, but the attack may have been given after burial of the wood and not during their lifetime and therefore can humidity be related to their depositional environment and not necessarily their habitat.