Brazilian aeolian sediments dating using tl, osl and esr

Abstract

In this work, a dunefield known as Dama Branca (Brazil) has been dated using the following techniques: Optically Stimulated Luminescence (OSL), Thermoluminescence (TL) and Electronic Spin Resonance (ESR). They are part of what is called “trapped charge dating technique”. Sediments have been collected from several points to study age distribution throughout Dama Branca. These ages are related to events of sediment transportation and stabilization. For Dama Branca specifically, variables related to weather such as rainfall and wind power are suspected to be responsible for its formation. OSL results were obtained applying the SAR protocol. TL and ESR results were obtained using the Multiple Aliquot Additive Dose protocol (MAAD). With respect to ESR measurements, the Ti-Li center was chosen for dating since it can be completely bleached by sun light exposure , which makes it suitable for aeolian sediment dating. The Ti-Li center is strongly dependent upon preheat, its stability has been assessed and a preheat temperature of 180 °C was selected. OSL ages are within 0.05 kyears and 2.05 x kyears. TL ages agree with OSL ages for samples collected from the dune base, however there are discrepancies between OSL and TL ages for the DBM2BASE sample, suggesting that it underwent a quicker burial process. ESR results are satisfactory for two samples, 2DB10 and 2DB11 (they follow OSL and TL results). The ages were compared to a simplified morphological study. In recent works about the weather in the Cabo Frio region it has been seen that the studied areas were formed under influence of arid conditions and cold water, variables that control sediment transportation in the region. Keywords (max. 5): TL, ESR, OSL, quartz, sediments dating.