OSL dating of flood sediments in the North China Plain

Abstract

Partial bleaching is a major challenge in OSL (Optically Stimulated Luminescence) dating of flood sediments. Here we investigated both modern and palaeoflood sediments in the North China Plain. It demonstrates that most of the OSL ages for either coarse-grained (CG) or fine-grained (FG) quartz were overestimated in different levels. In the clay-dominated flood deposits, OSL signals of FG quartz from samples at the top of each layer can be bleached to a lower level and therefore give relatively accurate ages. While in silt-dominated flood sediments, the ages of FG quartz are significantly older than those of CG quartz. Ages obtained using the Minimum Age Model (MAM) for CG quartz are the closest to the burial ages of sediments, and the overestimation is mostly in the range of 0.5–1 ka. Although the FG quartz in silt sediments are not suitable for OSL dating the flood events, the OSL ages of FG quartz changes accordingly to the particle-size changes within each silt-dominated layer. The lager the particle sizes are; the older the OSL ages of FG quartz are. The OSL ages of CG quartz are corresponds in an opposite way. It can help to identify floods deposits. Furthermore, the differences of residual OSL ages of FG quartz in different layers in flood sediments may provide more depositional information.