Exploring the sensitivity of marine sediment luminescence as a new proxy for past changes in precipitation and dust supply

Marine sediment cores are key archives for reconstructing past environmental conditions, including continental precipitation amount and dust flux, which are essential drivers of climate variability. Commonly, precipitation is inferred from proxies such as plant-wax hydrogen isotopes (n-alkane δD) or elemental ratios (e.g., ln(Fe/Ca)). In contrast, dust supply variability is reconstructed from aeolian mass accumulation rates or normalized-constant flux (²³⁰Th or ³He_ET‐normalization) methods. Although these proxies are very powerful when the sedimentary context is favorable, they can be limited by numerous factors, including material availability, post-depositional alteration, and sea-level fluctuations. Here, we explore an alternative methodology: the study of the quartz Optically Stimulated Luminescence (OSL) sensitivity. We developed a novel luminescence scanner capable of analysing intact sediment cores without the need for subsampling. The system integrates an OSL reader equipped with infrared (850 nm) and blue (480 nm) LEDs, corresponding cutoff filters (780 nm and 420 nm), and a photomultiplier tube with an ultraviolet bandpass filter (Hoya U340). An X-ray source (60 kV) provides controlled irradiation. All components are managed by custom software, Vagalume, which enables real-time control and automatic calculation of key parameters such as BOSL₁s/BOSL_total and IRSL₁s/BOSL₁s ratios, as well as X-ray voltage and current. BOSL₁s (quartz) and IRSL₁s (feldspar) were derived from the first second of the respective decay curves, while BOSL_total was calculated from integrating the whole decay curve. These parameters allow tracking changes in terrestrial sediment sources that correlate with changes in precipitation or wind patterns. Method validation was conducted on two particularly well constrained marine sediment cores: (1) site MD23-3670Q (AMARYLLIS-AMAGAS II cruise) located off the Amazonian basin from which the Southern American monsoon precipiation amounts were reconstructed for the last 60ka and (2) site MD03-2705 (PICABIA cruise) located off West Africa from which the Saharan dust flux was reconstructed for the last 240ka (Skonieczny et al., 2019). Sediment cores were scanned at 1 cm resolution, with a 3-hour acquisition time per section (1,5m). For precipitation, the luminescence results were then compared with Fe/Ca ratios obtained via X-ray fluorescence (Avaatech) on the same sediments (MD23-3670Q). In contrast, the dust-flux estimates derived from luminescence were further compared with ²³⁰Th-normalized fluxes obtained from the same sediments (MD03-2705). Our findings demonstrate that the new scanner provides reliable, high-resolution data and represents a robust alternative for reconstructing past continental precipitation and dust flux using luminescence proxies in marine sediment archives.