Optically stimulated luminescence and isothermal thermoluminescence dating of high sensitivity and well bleached quartz from Brazilian sediments: From Late Holocene to beyond the Quaternary?
Carregando...
Data
2016-06-01
Autores
Sawakuchi, André Oliveira
Mendes, Vinicius Ribau
Do Nascimento Pupim, Fabiano
Mineli, Thays Desiree
Ribeiro, Ligia Maria Almeida Leite
Zular, Andre
Guedes, Carlos Conforti Ferreira
Giannini, Paulo César Fonseca
Nogueira, Luciana
Filho, William Sallun
Título da Revista
ISSN da Revista
Título de Volume
Editor
Resumo
The development of optically stimulated luminescence (OSL) dating of sediments has led to considerable advance in the geochronology of the Quaternary. OSL dating is a well established technique to determine sediment burial ages from tens of years to few hundred thousand years. Recent studies have shown that Quaternary sediments of Brazil are dominated by quartz grains with high luminescence sensitivity, allowing the determination of precise and reliable OSL burial ages. In this paper, we show examples of OSL dating of quartz aliquots and single grains from different regions in Brazil, including young coastal-eolian Late Holocene (< 100 years) to Late Pleistocene (∼ 150 ka) fluvial sediments. We discuss the OSL data and ages of sediments from carbonate and terrigenous (distributary and tributary systems) fluvial depositional contexts in Brazil. Most of the studied fluvial sediments show equivalent dose distributions with low to moderate dispersion, suggesting well bleached sediments. The comparison between aliquot and single grain data suggests that high overdispersion in equivalent dose distributions of some samples is more related with sediment mixture due to bioturbation than with incomplete bleaching during transport. Well bleached fluvial sediments contrast with the poor bleached pattern usually described for fluvial sediments in the literature. A large part of the fluvial sedimentary record in Brazil is older than the age limit for quartz OSL dating using blue light stimulation. Thus, isothermal thermoluminescence (ITL) dating protocols were tested for dating of fluvial sands from the Xingu River (eastern Amazonia). The studied sample can recover reliable equivalent doses up to 1600 Gy using the ITL 310°C signal. Therefore, this signal would be suitable to extend the age limit of quartz luminescence to the whole Quaternary or beyond (> 2 Ma) in the low dose rate (0.5-1.0 Gy/ka) environments typical for Brazilian sediments.
Descrição
Palavras-chave
Brazilian sediments, OSL dating, Quartz, Quaternary geochronology
Como citar
Brazilian Journal of Geology, v. 46, p. 209-226.