| الملخص: | <p>Sand dunes in the Thar Desert, owing to their location in the Indian summer monsoonal (ISM) regime, are rich archives of past geomorphological and palaeoenvironmental changes. However, existing dune records are not robust enough to allow their assessment and integration with a growing multiproxy framework of palaeoenvironmental change. Therefore, with an aim to <em>investigate the timing of dune activity in the Thar</em>, three research questions are answered in this thesis: (i) what are the key phases of dune activity; (ii) what is the effect of anthropogenic influences on the landscape; and (iii) how can dune chronologies be interpreted most effectively to reconstruct late Quaternary environmental changes? To answer these, systematic sampling of multiple dunes was carried out in the dunefields in the central and northern Thar, and luminescence dating was used to provide a detailed chronological framework.</p>
<p>Results demonstrate that the Thar dunes are >58 ka old, with preserved accumulation phases throughout the Holocene at ~11.6-8.5, 4-3, 2-1, 0.6-0.2 and 0.07 ka. First records of modern net accumulation are presented, with rates varying between 2-5 m/year, attributable to anthropogenic disturbances. Dune accumulation intensity methodology, in conjunction with available highly-resolved marine and terrestrial datasets, is used to infer palaeoenvironmental changes in the Thar. Whilst the strengthening of the ISM has been evidently shown to have a significant influence on widespread dune accumulation in the early Holocene, equivocal relationships between both lake levels/dune accumulation and monsoon variability during later Holocene suggest a complex interplay of regional and more local drivers like sediment supply, lowered sea levels etc. The study concludes with emphasis on the importance of recognising external and local controls on dune systems, and demonstrates that diverse responses to same environmental stimuli should be expected in palaeoenvironmental reconstructions.</p>
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