Increasing our understanding of Holocene dune activity in the Thar Desert, India using a portable luminescence reader

Description

Understanding future changes to dune activity in the densely populated Thar Desert, India will be aided by a comprehensive understanding of its complex dune developmental history. This requires a dunefield-scale investigation with sufficient sampling resolution to provide in-sights into the spatio-temporal variations in dune accumulation history. However, establishing dune accumulation histories using traditional chronological techniques is time and resource intensive. For this reason, this study utilises rapid-age estimates, derived from portable lumines-cence reader signals (port-OSL), calibrated via a regression against existing laboratory-based luminescence ages. 222 samples were collected from ten linear dunes on a 100 km transect in western Thar, a hyperarid region that lacks robust dune chronologies. Port-OSL (IRSL: BSL signal ratios of 0.29 to 0.35), along with particle size analysis (moderately–well-sorted medium to fine sand) suggests a similar provenance for all samples, which demonstrates the feasibility of using calibrated port-OSL measurements for rapid age estimates. Additionally, the influence of bulk sample moisture content on port-OSL signals was investigated, showing an attenuation of 30% up to a threshold of 1% moisture by weight.

Calibration of port-OSL measurements was carried out using ages of samples with previ-ously established chronologies from central Thar (n=40)[1] as well as newly dated samples col-lected as part of this study (n=4) and showed a good fit using a linear regression model ap-proach[2] (R2=0.84). Based on calibration, all 222 samples were within the Holocene, ranging between 150 and 11000 years old and corresponding to port-OSL BSL totals of 0.2 million and 14 million counts. The spatio-temporal patterns of dune accumulation seen are that eastern flanks are younger and have a higher accumulation rate than the western flanks, suggesting an eastward migration of the dunes. A period of high accumulation between ~ 8 ka and 6 ka in six of the dunes, corresponds to the Holocene warm period during which the Indian summer mon-soon winds were stronger[3]. This study demonstrates the utility of the port-OSL technique for determining the spatial variability in dune accumulation at large spatial scales (~100km) within the Thar desert.

Period	26 Sept 2022
Event title	6th Asia-Pacific Conference on Luminescence and Electron Spin Resonance Dating – APLED 2022
Event type	Conference
Location	Ankara, TurkeyShow on map
Degree of Recognition	International