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Accueil du site → Doctorat → Royaume-Uni → 1997 → Aeolian activity and environmental change in the Central Mega Kalahari : implications for the timing, nature and causes of late Quaternary aridity.

University of Sheffield (1997)

Aeolian activity and environmental change in the Central Mega Kalahari : implications for the timing, nature and causes of late Quaternary aridity.

O’Connor, Peter W.

Titre : Aeolian activity and environmental change in the Central Mega Kalahari : implications for the timing, nature and causes of late Quaternary aridity.

Auteur : O’Connor, Peter W.

Université de soutenance : University of Sheffield

Grade : Doctor of Philosophy (Ph.D.) : 1997

Résumé
Extensive systems of fossilised aeolian landforms dominate many parts of the Central Mega Kalahari, forming impressive pieces of evidence for the widespread nature of late Quaternary climatic change. Despite their palaeoenvironmental and palaeoclimatic significance these forms have not been directly dated, with phases of aridity and dune development inferred from gaps within subcontinental humid chronologies. Previous research emphasising the importance of aeolian activity in southern Africa between 20-18 ka BP supports the widely cited view that the last glacial maximum (LGM, 20-18 radiocarbon ka BP, c. 23-21 ka BP) was the peak of late Quaternary aridity and dunefield construction in global desert basins.By applying the optically stimulated luminescence (OSL) method to samples collected from the fossilised dunefields of Western Zambia and the Caprivi Strip, northern Namibia, a number of questions relating to the timing and nature of dune dynamics have been assessed. 33 OSL dates indicate six periods of linear dune building between c. 48-41, 35-28, 23-21, 16-13, 10-8 and 5-4 ka. 11 OSL dates indicate that lunette dune accumulation was most extensive in Western Zambia at c. 29-27 ka and 10-8 ka. OSL ages from the vertical sections of linear and lunette dunes indicate that these forms evolved from multiple phases of reworking and/or accretion. The spatial scale of linear dune activity has varied significantly throughout the periods identified by this investigation. In particular, the environmental controls on linear dune activity and the sensitivity of linear dune reactivation to climate change has exhibited spatial and temporal variability. The period corresponding to the LGM is not specifically identified as the most critical period of enhanced aeolian deposition. As a result, it should be recognised that aridity in southern African is not exclusively a function of glacial climate. Causal linkages have been made between dune activity, glacial-boundary conditions, insolation changes and fluctuations in sea surface temperature. These suggested relationships have highlighted the complexity of environmental and climatic factors controlling dune activity.

Annonce : EThOS (UK)

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