Abstract
The entrainment, transport and deposition of wind-blown (aeolian) sediments is vital to our understanding of the links between the resulting depositional landforms and climate dynamics in a region. The nature of aeolian processes has varied over Quaternary timescales, and is dependent on changing sediment supply, existing topography and climatic parameters such as wind strength and moisture availability, at local to supra-regional spatial scales [1]. Hence, in order to understand long-term interactions between aeolian-dominated landscapes and climate, there is a need to investigate the mechanisms driving wind-blown processes. In this context, the Ili basin of southeast Kazakhstan, with its extensive piedmont loess deposits and desert dunefields, provides an excellent case study for investigating aeolian earth-surface processes and their links to climate. Quartz is one of the most abundant and robust minerals on the earth’s surface. The lattice defects and impurities in quartz provides a potential provenancing tool, which can be probed by luminescence and electron spin resonance (ESR) techniques [2,3]. Here we investigate the luminescence sensitivity and ESR signature of various paramagnetic centres (E’, peroxy and [AlO4]0) in quartz of different grain sizes from Pleistocene loess, as well as from surface sediments and rocks collected from various depositional and potential source contexts across the Ili basin. We observe significant difference between fine and coarse grain quartz samples from various depositional settings which highlights the difference in entrainment and transport processes for different grain sizes. Our observations allow us to assess the validity of hypothesised aeolian depositional models as well as the more recent back-trajectory models for dust transport [1] in the region, thus, establishing an empirical understanding of modern aeolian earth-surface processes. Based on these results, we extend our understanding of modern processes to investigate past aeolian dynamics. Our data provides first empirical insights into the origin of fine-grained sediments along the piedmont and what these can tell us about climate dynamics in Central Asia. References: [1] Fitzsimmons, K.E., Nowatski, M., Dave, A.K., Harder, H., 2019. Intersections between wind regimes, topography and sediment supply: perspectives from aeolian landforms in Central Asia. Palaeogeography, Palaeoclimatology, Palaeoecology 540, 109-531. [2] Gray., H.J., Jain, M., Sawakuchi, A.O, Mahan, S.A., Tucker, G.E. 2019. Luminescence as a Sediment Tracer and Provenance Tool. Reviews of Geophysics 57 (3), 987-1017 [3] Toyoda, S., Nagashima, K., Yamamoto, Y., 2016. ESR signals in quartz: Applications to provenance research – A review. Quaternary International 397, 258-266.