Optical dating of young deltaic deposits on a decadal time scale

摘要

Modern Mississippi Delta sediments were analyzed to investigate quartz OSL signal resetting in large river deltas and test the accuracy of OSL dating on a decadal time scale with the early background subtraction and a recently proposed burial dose estimation procedure. Both fine silt-sized and sand-sized quartz were measured with a modified single-aliquot regenerative dose (SAR) protocol and equivalent dose (D _e) was calculated using different background subtraction methods. Evidence of insufficient bleaching was observed, but the residual signal is equivalent to ～100a on average for both sandy quartz and fine silt-sized quartz. It is shown that dose distributions of sandy quartz are affected by the background subtraction. The proportion of aliquots that have D _e in agreement with expectation is significantly larger when an early background is subtracted compared to the late background subtraction. This is, in contrast, not observed for fine silt-sized quartz. Accurate OSL ages were obtained by employing the unlogged minimum age model to D _es of sandy quartz obtained with the early background subtraction method.