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University of Leicester (2018)

The Influence of Complex Topography on Aeolian Sediment Accumulation and Preservation : An Investigation of Morphology and Process History (Mojave Desert, California, case study)

Hay, Alex Stephen

Titre : The Influence of Complex Topography on Aeolian Sediment Accumulation and Preservation : An Investigation of Morphology and Process History (Mojave Desert, California, case study)

Auteur : Hay, Alex Stephen

Université de soutenance : University of Leicester

Grade : Doctor of Philosophy (PhD) 2018

Résumé
It has long been understood that topography has an important influence over systems of aeolian sediment transport, accumulation and preservation. There has, however, been a comparative lack of investigation into how aeolian sediment accumulation and preservation responds to the influences of complex topography and variable sediment sources at a landscape (rather than landform) scale. Using the Mojave Desert, California, as a case study, this study demonstrates that the distribution and form of aeolian deposits is related to the topography of the mountain block and is manifest as deposits which represent three accommodation space types, each having a characteristic morphology (sand ramps, sand sheets and valley-fills). The observed aeolian morphologies cannot necessarily be delimited into a discrete patchwork of landforms because, in many cases, they lack distinct boundaries and because of the close association of the different accommodation space types within the landscape. Observed aeolian deposits range from thin veneers of sand to significant (>15m) deposits with visible sections. A series of ages derived from luminescence dating indicate that the aeolian system has operated across the majority of the last 80ka and can be associated with variations in sediment supply and availability. After deposition, topographically-anchored aeolian deposits can be (though are not necessarily) highly persistent features within the landscape, with their preservation potential also related to their accommodation space. Across this time, coarse-grained sediments appear as event-based and highly localised deposits which inter-finger with the predominantly aeolian sediments, indicating that the processes operated contemporaneously rather than switching between states of aeolian and hillslope process dominance.

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