@InProceedings{TatumiRoss:2018:AgMoAp,
               author = "Tatumi, Sonia Hatsue and Rossetti, Dilce de F{\'a}tima",
          affiliation = "{Universidade Federal de S{\~a}o Paulo (UNIFESP)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)}",
                title = "Age models applied to Amazon fluvial sediments",
                 year = "2018",
         organization = "Encontro Nacional de F{\'{\i}}sica da Mat{\'e}ria Condensada 
                         (ENFMC)",
             abstract = "Sediment samples were collected from the State of Amazonas to be 
                         dated by the method of Optically Stimulated Luminescence (OSL). 
                         OSL shine down curves of quartz grains were measured with blue 
                         excitation and detecting the emission in the UV region. When 
                         quartz is exposed to sunlight, its OSL intensity is bleached. 
                         During subsequent burial, ionizing radiation strikes the grain 
                         surfaces and the energy is eventually transfer to the crystal 
                         releasing charge carriers, which can be trapped in defects and 
                         impurities locate in the crystalline lattice forming metastable 
                         states. The concentration of these states increases with burial 
                         time. If the grain is optically excited, the charges are released 
                         and can recombine to emit light (OSL). OSL intensity is 
                         proportional to burial time and provide the sample age. In this 
                         case, the ionizing radiation flux is generated by natural 
                         radioactive isotopes from the U-235/U-238, Th-232 and K-40 series 
                         present in the sediment, as well as, the cosmic radiation incident 
                         in the depositional site. In this work, 10 samples were collected 
                         at various depths using aluminum tubes. Parcels of each sample 
                         were separated for OSL and gamma spectroscopy analyses. OSL 
                         measurements were performed according to the single aliquot 
                         regeneration (SAR) protocol. The age model was applied to 
                         determine the equivalent doses (De) of quartz grains. Gamma-ray 
                         spectra were carried out to determine the radioactive content of 
                         the samples. Values of the radioactive isotopes concentrations 
                         were used to calculate annual dose rates (DA) of the sediments. 
                         The ages (I) of the samples were determined by the equation I = De 
                         DA . The results showed age dispersions between 13 to 29%. Ages of 
                         samples with dispersion less than 20% were calculated using the 
                         central age model (CAM) and the finite mixture age model (FMM). 
                         Samples with dispersion greater than 20% had their ages determined 
                         by the minimum age model (MAM) and FMM. The ages results obtained 
                         ranged from 5,600 to 142,700 years, which is consistent with 
                         sediment deposition during the latest Mid-Late Pleistocene to 
                         mid-Holocene. We conclude that the methodology and the models 
                         adopted were satisfactory for age determination. These results are 
                         valuable to approach issues concerning paleoenvironmental and 
                         paleoclimatic reconstructions before the establishment of the 
                         modern drainage systems.",
  conference-location = "Foz do Igua{\c{c}}u, PR",
      conference-year = "06-11 maio",
             language = "en",
        urlaccessdate = "27 abr. 2024"
}