Insights from playing with portable luminescence readers in two continents and four laboratories.

Description

Portable luminescence (port-OSL) readers are powerful tools within trapped charge dating (Munyikwa et al., 2021). High-resolution profiles with depth can contextualise sediment stratigraphy, with insights into (i) relative age, including the position of depositional unconformities, and also: (ii) variations in sediment composition (owing to provenance and/or weathering), (iii) variations in the completeness of luminescence signal bleaching (signal resetting before transport). In simple sedimentary systems, with broadly homogenous sediment provenance, it is possible to produce generalised chronologies that approximate sediment burial age.

Our approach is to compare port-OSL signals with established ages using standard luminescence dating protocols and construct calibration curves (Stone et al., 2019). Dryland dunefields have well-bleached aeolian sediments, making them an ideal testing ground. In southern Africa, we have found these port-OSL calibrations are region specific, with consistent and coherent grouping of samples from the Namib Sand Sea (n=26) and for three different parts of the Kalahari (n=66, n=38 and n=18) (Stone et al., 2019). The calibration approach also shows promise in the Thar Desert, India (n=44) (Nitundil et al., 2022). A change to the approaches taken in the port-OSL sequences and data processing during our investigations means the available portion of the southern African samples are being re-measured to facilitate an intercontinental comparison. We aim to present this intercontinental comparison.

Our experiences with port-OSL measurements on lake shoreline sediments in the middle Kalahari show weaker correlations than for dunefields and suggest sediment characteristics other than burial age drive differences in port-OSL signals in this setting. To test this, we have made measurements on a range of the subsamples from southern Africa to establish the response of bulk sands to a known 4 Gy dose in order to examine whether samples between regions have different inherent luminescence sensitivity. This may also give insights into sand provenance and sediment pathways.

Period	17 Jul 2023
Event title	XXI INQUA Congress: Time for Change
Event type	Conference
Location	Rome, ItalyShow on map
Degree of Recognition	International