title: Radioactivity distribution in some Permian sediments from the Iratí and Corumbataí Formations of the Paraná Basin, Southeastern Brazil.
abstract: In the city of Limeira, southeastern Brazil, an important exposure of Permian sediments of the Paraná basin was revealed by an open pit mine that exploits limestone for production of soil correction compounds and raw materials for the ceramic industry. The radioactivity of these sediments was investigated in some detail and the results provided a general view of the vertical distributions of uranium, thorium and potassium concentrations and of the element ratios U/K, U/Th and Th/K. In general, the concentrations of the main natural radioactive elements are low, with uranium being enriched in some limestone and shale levels. In addition the results showed that the 238U series is in radioactive disequilibrium in many of the analyzed samples. Although the origin of the observed disequilibrium has not been investigated, the results suggest that it is due to weathering processes and water interaction with the rock matrix.
authors.affiliation: Instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo, Departamento de Geofísica. Rua do Matão 1226, Butantã, 05508-090, São Paulo, SP, Brazil.
authors.forename: Dionísio Uendro
authors.initials: DU
authors.lastname: Carlos
authors.forename: Fernando Brenha
authors.initials: FB
authors.lastname: Ribeiro
authors.forename: Antonio Roberto
authors.initials: AR
authors.lastname: Saad
authors.forename: Silvia Helena de Araújo
authors.initials: SH
authors.lastname: Nicolai
mesh_terms: D001938:Brazil; D019015:Geologic Sediments / Q000032:analysis*; D008906:Mining; D011197:Potassium Radioisotopes / Q000032:analysis; D011834:Radiation Monitoring / Q000379:methods; D011851:Radioactivity; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D013051:Spectrometry, Gamma; D013910:Thorium / Q000032:analysis; D014501:Uranium / Q000032:analysis
chemical_list: D011197:Potassium Radioisotopes; D012990:Soil Pollutants, Radioactive; D014501:Uranium; D013910:Thorium