Análise estratigráfica e paleomagnética da Bacia de Lavras da Mangabeira

• Autor(a) principal: Cerqueira, João Carlos
• Data de Publicação: 2021
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/213979
• topic: Stratigraphy; Paleomagnetism; Mesozoic; Lavras da Mangabeira Basin; Estratigrafia; Paleomagnetismo; Mesozoico; Bacia de Lavras da Mangabeira

The Lavras da Mangabeira Basin, located in the State of Ceará, is a set of small sedimentary basins developed during the Gondwana mesozoic evolution. It belongs to the group of Interior Basins in the Northeast, which have increased detailing to understand the rifting event in the Cretaceous. Despite this, the Lavras da Mangabeira Basin has its stratigraphy and tectonic-sedimentary evolution little investigated, resulting from the scarcity of literature and publications focused on it. The present work of completion of course aims to supply the lack of stratigraphic knowledge and of the tectonic-sedimentary evolution of the basin, through stratigraphic and paleomagnetic analysis, in addition to a brief discussion on its structural geology. The stratigraphic analysis was based on fieldwork, facies description and association, columnar surveys, paleocurrent measurements and measurement of the thickness of the sedimentary packages. The paleomagnetic analysis made a comparison between paleomagnetic poles and virtual geomagnetic poles of the basin units with the apparent path of the paleomagnetic pole of the Amazonian Craton. The stratigraphic surveys collaborated in the revision of the Iborepi Formation, Serrote do Limoeiro Formation, diabase Lavras da Mangabeira and the establishment of a new one, named Mescla Formation. The Iborepi Formation is the basal unit, it is found on a lithological discordance with the basement, it has an sand conglomeratic character of an interlaced river and it has an average paleocurrent vector for NNW. The Serrote do Limoeiro Formation has layers of fine lake facies at the base, with intercalation between these and sandy facies from meandering river to the top, in addition to some eolic sandstone, presenting very scattered paleocurrents. The Mescla Formation is in erosive contact at the base and is composed of conglomeratic sandstones and interglomerate river sandstones, with paleocurrent indicating a flow to the NW and intense deformation at the top. Diabase Lavras da Mangabeira was reinterpreted as intrusive, due to its placement in sedimentary packages. The formations are much thicker than the literature studies, reaching up to five times greater. The basin was also divided into sectors, term indicating that they were previously a single basin, as it presented the same evolution and vertical stacking. The paleomagnetism resulted in ages of the Iborepi (PermianTriassic), Serrote do Limoeiro (Jurassic-Cretaceous) and Mescla (JurassicCretaceous) formations, in addition, through the diabase's paleomagnetic pole, to identifying a clockwise rotation of 20º of the basin, younger than 200 Ma (diabase radiometric age) and older than the Cretaceous. The tectonic-sedimentary evolution of the basin had a first phase of sedimentation linked to the local Afro-Brazilian Depression and with the opening of the neo-Triassic-Atlantic Jurassic Central Atlantic. A second phase of sedimentation is linked to the pre-rift phases of the Gondwana break up, with the tilting of the layers and dismemberment of the basin in the post-rift