Reavaliação deposicional da Bacia de São José de Itaboraí com base em dados geológicos e geofísicos

Abstract

São José de Itaboraí Basin is located in Itaboraí, Rio de Janeiro State. It was discovered in 1928 by Carlos Euler, an engineer who after analysing a supposed kaolin, found on São José farm by its owner in those days, Mr. Ernesto Coube, realized it was limestone. The Professors Rui Lima e Silva and Othon H. Leonardos, sent to the site to study it, found great quantity of fossils of continental gastropods, triggering scientific interest in the region. The earlier site studies and chemical analyses made evident the good prospects to explore limestone to make the Portland cement type. The quarry was explored for more than fifty years by Companhia Nacional de Cimento Portland Mauá (CNCPM). Since its discovery São José Basin alongside with the mining activities, served as a scientific research object for geologists, palaeontologists and archaeologists. In the early 1980s, Cia. de Cimento Mauá decided to give up the area owing to the economic exhaustion of the ore reserve. With the withdrawal of the pumps which prevented the flooding of the quarry, a lagoon was formed and thus prevented the free access to the outcrops. Since then, the researches on the Basin remained focused on the material collected during the time of limestone exploration. Such material has been distributed among Museu Nacional (MN) National Museum, Departamento Nacional da Produção Mineral (DNPM) National Department of Mineral Production, Institute de Geociências da UFRJ - Institute of Geosciences of UFRJ among others. In 1990, CNCPM lost the ownership over the area under the pressure made by the scientific community. The ownership was then bestowed to the city of Itaboraí, which created the Parque Paleontológico de São José de Itaboraí (Palentolocial Park of São José de Itaboraí), through Law number 1.346, on the 12 December, 1995. The objective of this study was to generate new data through the geophysical method known as magnetometry. To that purpose site studies were carried out using a portable magnetometre and GPS navigation data, data was analysed and corrected using specific softwares, models were designed and profiles were created from descriptions and sounding testament. The obtained results aim at a possible new interpretation of geology and of the stratigraphy of the basin, making possible an updating of the knowledge related to the region, after almost half a century of mining activity.