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Title: Desert dune system response to Late Quaternary environmental change in the northeastern Rub’ al Khali : advances in the application of optically stimulated luminescence datasets
Author: Leighton, Carly L.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2014
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The application of optically stimulated luminescence (OSL) dating to desert sand dunes has allowed accumulation histories to be used as tools to infer past environmental change. In response to issues facing the interpretation of these records, two research questions are addressed in this thesis. (i) Are dune chronologies representative of dune stratigraphies? And (ii) how can we most appropriately interpret dune chronologies as records of Quaternary environmental conditions? Five dune profiles were sampled for OSL dating at two sites in the northeastern Rub’ al Khali in the southern Arabian Peninsula. The visible stratigraphy was used to guide sampling for three of the profiles and the effectiveness of this approach is assessed. A key finding is that bounding surfaces are not always identifiable as chronological hiatuses by OSL dating, given the level of precision that can be achieved. Using hierarchical relationships visible in two-dimensional exposures is therefore not guaranteed to identify the depositional units necessary to reconstruct dune histories. Comparison of the depositional records from three sampled profiles shows that there is significant variability in chronologies at both the dune and dunefield scales. In light of these findings, the use of ‘range-finder’ OSL dating was investigated as a method of increasing sample throughput in the laboratory. It is concluded that the use of partially prepared samples and shortened measurement techniques can be used to rapidly assess the chronological context of samples and target those units most useful in constructing dune profiles. A new method of presenting dunefield OSL datasets as net accumulation rates, incorporating accumulation thickness rather than relying on the frequency of ages, is presented. Within the last 30 ka, regional accumulation and preservation occurred at ~30-26, 22.5-18, 16-9, 6-2.7, 2.1-1.6, 1.1 and 0.7 ka. In conjunction with numerical model results and a review of other palaeoenvironmental archives, the regional aeolian record is interpreted as a response to changing forcing factors. High rates of net accumulation between ~16-9 ka are attributed to coeval increases in sediment supply and transport capacity. A hiatus in accumulation between ~9-6 ka is interpreted as a result of reduced sediment availability due to high moisture levels. The importance of both external forcing factors and local controls on dune accumulation processes is recognised, and therefore the importance of sampling at multiple locations to distinguish these factors is emphasised.
Supervisor: Thomas, David S. G.; Bailey, Richard M. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geography ; Middle East ; Dating ; Landscape ; Quaternary ; OSL dating ; Arabia ; dunes ; geomorphology