Resetting of quartz and feldspar luminescence signals under water

Quantifying luminescence signal resetting of sand grains in turbid waters is essential for both sediment dating and tracing, yet direct measurement under natural subaqueous conditions remain scarce. Here, we present the first depth-resolved experiment that combines in-situ luminescence resetting, subaqueous light spectra and suspended sediment concentration in a tidal inlet. Sand-sized quartz and feldspar grains were exposed to daylight at multiple depths during a one-day deployment, while optical and sediment conditions were continuously monitored. Single-grain luminescence measurements reveal depth-dependent resetting with a bleaching front below which no significant signal resetting occurs within a day. The position of this bleaching front depends on signal bleachability and agrees with predictions based on spectral irradiance and mineral-specific photo-ionization cross sections. By directly linking subaqueous light conditions, sediment concentration, and mineral-specific bleaching behaviour, our findings provide empirical quantification that can inform luminescence dating, provenance studies, and tracing of sediment transport in dynamic coastal systems.