Pushing the frontiers of age control for dune activity and migration in the Thar Desert, India.

The Thar Desert of India is one of the world’s most densely populated drylands where reactivation of currently stable dunefields can cause damage to life and property. Appropriate hazard mitigation strategies must be informed by an understanding of the response of these sedimentary systems to climatic forcing (such as the Indian Summer Monsoon) and land-use change (such as the expansion in agriculture, facilitated by irrigation from growing canal networks). Chronologies for dune activity and migration provide the basis for that understanding over 100-1000s of year timescales. The spatial-temporal variability to forcing at the landscape scale means that high-resolution sampling (across space and through depth) is needed. However, establishing dune chronologies using traditional laboratory approaches is costly, laborious and resource intensive (e.g. a decade of work and ~10 PhD studies for current understanding in the Kalahari, southern Africa), making it difficult to explore dunefield level responses. The history of dune activity in the Thar has only received the attention of one detailed PhD study (Srivastava et al., 2020).

This project aims to overcome these limitations of time and budget by employing a novel methodological approach to rapidly estimate dune ages. This combines portable luminescence (port-OSL) measurements with laboratory-based chronologies (Stone et al., 2019), requiring a population of samples to have undergone both analyses. 122 samples have already been collected in the field in 2022, from the western reaches of the Thar, near Ghotaru, by Shashank Nitundil, as part of his MSc dissertation research, with the port-OSL signals analysed. We propose obtain luminescence ages (at St Andrew’s luminescence laboratory) for eight of these samples, spanning the range of portable reader signal sizes. We also plan another short field campaign in 2023 with a hand-auger to access deeper, and therefore, older samples. The eight new luminescence ages, and the estimated luminescence ages from both the existing 112 samples, and the ~100 sample from the new field campaign (using the regression model for calibration that we will build), will be used to address our key research questions:
1) What is the record of dune activity and migration over the past 10,000 years in the western Thar, and how does this vary across a 100 km transect, and between neighbouring dunes?
2) How does the dune accumulation record relate to independent proxies for windiness and moisture availability in the Thar, and records of human land-use change, and how do we relate this pattern of forcing and response to predictions of future climate change?

The scientific discoveries into shifting sands in peri-urban areas informs resilient futures within the sustainable futures research platform. Our novel methodological approach to calibrating the field-instrument (port-OSL reader) to provide age control for sedimentary deposits lays the ground for a range of other geographical locations where dune migration is a geohazard and other geomorphological, Quaternary Science and geoarchaeology applications. This opens up a range of future collaborative opportunities for Geography and MERI at the University of Manchester.