Applicability of using portable luminescence reader for rapid age-assessments of dune accumulation in the Thar desert, India

Reconstructing dunefield-scale palaeoenvironmental histories is important, particularly in the context of understanding the complexity of dune development under future climate and land use changes in the densely populated Thar Desert, India. Dunefield-scale investigations with sufficient sampling resolution to provide insights into the spatio-temporal variations in dune accumulation history are time and resource intensive using traditional chronological techniques. For this reason, this study utilises rapid-age estimates derived from portable optically stimulated luminescence reader signals (POSL). POSL signal characteristics suggest a similar provenance for all samples, demonstrating the feasibility of using calibrated POSL signal counts for rapid age estimates. Calibration of POSL BSL signals carried out using ages of 40 samples with previously established OSL chronologies from central and northern Thar and 4 new OSL ages from western Thar shows a good fit (linear regression, R2 = 0.89, RMSE = 1427 years). We also explore the use of POSL IRSL in the calibration, as well as calibrating POSL signals against established sample De. Any dependence on dune type, vegetated linear versus parabolic is also explored, as well as any dependence of outliers on sediment characteristics, such as organic content and carbonate content. We find that bulk sediment moisture attenuates POSL signals up to a threshold of ~0.73% moisture by weight, corresponding to a 24% attenuation. Our calibration is used to investigate intra and inter-dune variability in accumulation on three vegetated linear dunes in arid western Thar (a further 118 samples). Eastern flanks of these dunes are younger and have a higher accumulation rate than the western flanks, suggesting an eastward migration of the dunes. This study demonstrates the utility of the POSL reader in undertaking large landscape scale studies where the volume of analysed samples can outweigh the reduced accuracy of the POSL based rapid-age estimates.