Análise paleomagnética da Formação Cerro Negro, Grupo La Providencia (Ediacarano, Argentina)

• Autor(a) principal: Papel, Manoela Machado [UNESP]
• Data de Publicação: 2018
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/203394; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2019-05-14/000914985.pdf
• topic: Paleomagnetismo; Rochas sedimentares; Paleografia; Argentina

The Neoproterozoic area in Argentina is relatively restricted and there is a considerable lack of data on the accuracy of the age of the local sedimentary rocks and the paleogeography of the depositional environments. The apparent migration of the magnetic poles, which defines the position of the plates in time, is well documented for Gondwana in the period between 550-500 Ma, but there is a scarcity of such data in the interval between 600-550 Ma. A paleomagnetic analysis of the Cerro Negro Formation, La Providencia Group, Argentina, Ediacaran, can contribute to the paleomagnetic knowledge of this interval. Three rock collections, one outcrop (CA) and two cores (TSE-13 and TA-21) were studied. Three components were isolated in each set of samples, named A, B and C. The low stability A component of the three collections shows a large dispersion of data and, therefore, unreliable statistical results with high errors. The B componente, very widespread, is considered secondary, resulting from remagnetization processes between Permian and Triassic. In CA collection, the B component, unlocked at temperatures around 350 °C, shows mean direction Dec: 356.2, Inc: -9.7 (n: 17 and α95: 9.3). In TSE-13 collection, component B reveal demagnetizing temperatures ≤350 °C, with mean direction Dec: 8.9, Inc: -37.4 (n: 21 and α95: 10.4). In TA-21, dual-polarity component B, with unblocking temperatures ≤625 °C, shows mean direction Dec: 8.1, Inc: -50.7 (n: 46 and α95: 6.3). The C component of the TA-21 core, also establish secondary, with dual-polarity and demagnetization temperatures ≤675 °C, shows Dec: 12.2, Inc: -38.7 (n: 61 and α95: 4.7). The C component of the TSE-13 collection was the only isolated component that carries the characteristic magnetization of the rocks, transported by hematite (temperatures between 600-675 °C), with Dec: 40.4, Inc: 45.0 (n: 9 and α95: 12.3). The results of remagnetized samples can not be used in paleolatitude...