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University of Nottingham (2022)

A Multi-Approach Investigation of Late Quaternary Lacustrine Sediments in Southern Jordan

AlShdaifat, Ahmad

Titre : A Multi-Approach Investigation of Late Quaternary Lacustrine Sediments in Southern Jordan

Auteur : AlShdaifat, Ahmad

Université de soutenance : University of Nottingham

Grade : Doctor of Philosophy (PhD) 2022

Résumé partiel
Past lacustrine and wetland sediments from arid regions, sensitive to changes in precipitation and evaporation, are important archives of past environmental variability. This thesis presents new data that contribute to the Quaternary records of Jordan through multi-proxy analyses of sediment archives from two study sites in southern Jordan ; the Gharandal Valley and the Dead Sea Basin. Through detailed analyses of the sediments from the two study sites, the depositional environments, environmental conditions, and how these changed, and to some extent their timing were reconstructed.

Sediments from the Gharandal Valley were investigated and collected from five different sedimentary sections (> 30 m sediments) and analyzed for particle size distribution, organic and carbonate content (through LOI), and elemental (through XRF) and minerogenic (through magnetic susceptibility) composition. The results indicated complex tectonic/climate-driven depositional environments prevailed in the valley, during Marine Isotope Stage (MIS) 6, alternating from fluvial in-wash to fluvio-aeolian and wetland deposition following the proposed valley outlet damming.

The GH1 and GH2, the main sections in the valley, record the environmental aggradation from stream-fed wetland depositional conditions where thin wetland beds developed following in-wash events, in the lower parts, into more consistent wetland (wetter) conditions towards the top of the sections. These cycles were identified in 16 fining upward primary associations in the GH1 section and 8 fining upward primary associations in the GH2 section.

The age estimate (MIS6) is consistent with wet phases recorded elsewhere in the Levant and increased monsoon precipitation recorded in southern Arabia suggesting that an influence of the two systems (the northeastern Mediterranean Cyclones and the southern tropical monsoon), which do not reach the valley site today, may have contributed to maintaining the wetland conditions in the valley during glacial stadials and interstadials.

From the eastern side of the Dead Sea Basin (DSB), the lacustrine section DS1 was investigated. The section is primarily comprised of laminated pale and dark laminae and laminated detrital laminae with a thick gypsum-dominated bed. Considering the different nature of the sediments, the DS1 bulk sediments were first analysed using proxies mentioned earlier for the Gharandal Valley. In addition, the pale laminae were analysed for the carbonate isotope composition (δ13C and δ18O), mineralogy (through XRD) and carbonate crystal habit (through SEM EDS) analysis.

Mots clés  : Jordan, Gharandal Valley, Dead Sea Basin, Quaternary, sediments, Quaternary sedimentology

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Page publiée le 19 janvier 2023