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Technische Universität Dresden (2015)

Fluvial dynamics in Spain - Significance for palaeoenvironmental reconstructions and landscape evolution in the Western Mediterranean

Wolf Daniel

Titre  : Fluvial dynamics in Spain - Significance for palaeoenvironmental reconstructions and landscape evolution in the Western Mediterranean

Auteur : Wolf Daniel

Université de soutenance : Technische Universität Dresden

Grade : Doctor rerum naturalium (Dr. rer. nat.) 2015

Résumé
In this dissertation, 36 profile sections have been worked out intensively. Furthermore, 13 percussion drillings were conducted in floodplain positions with insufficient exposure conditions. For the chronological frame 70 radiocarbon samples have been dated. The obtained results show a significant pattern of sedimentation periods and phases of stability associated with soil formation for each river system. The sedimentation history of the Guadalete and Guadalquivir Rivers could be reconstructed for the last 15 ka, while conclusions with regard to sedimentation dynamics of the Jarama River could be drawn for a period of 43 ka. Thanks to an abundance of available studies on other terrestrial archives with climatic or environmental relevance, it was possible to assess the influence of different parameters such as climate, vegetation, humankind, tectonics, and base-level changes on fluvial sedimentation dynamics. It emerged that, first and foremost, rapid climate changes had significant impact on the mobilization of sediments in the catchment area as well as their deposition in floodplain positions. On the other hand prolonged periods of climatic amelioration caused floodplain stability along with soil formation, as documented for the time spans between 13.3 and 12.7 ka, 7 and 5.1 ka, 2.8 and 2.3 ka, 1.4 and 1.2 ka, as well as 0.8 and 0.5 ka cal. BP in several river systems. Periods of increased sedimentation were initiated by phases of climatic aridification that affected fluvial systems through the weakening of the vegetation cover and the accentuation of the hydrological discharge regime. Corresponding patterns have been found for the time intervals between 8 and 7 ka, 5 and 3.8 ka, 2.2 and 1.5 ka, as well as around 1 ka and 0.4 ka cal. BP. The supra-regional effectiveness of the factor climate is contrasted by a strong regional individuality of the river catchments that is expressed by further, regionally limited phases of fluvial activity.
Crucial to this development – apart from regional climate differences – are, inter alia, tectonic movements as evidenced for the Jarama River system in central Spain, or late Pleistocene and Holocene sea-level fluctuations that primarily affected fluvial dynamics along the lower course of the Guadalete River in southwestern Spain. Furthermore, it can be shown that variations in time and duration of fluvial system response are attributable to differing buffer capacities of river catchments towards external influences. The increase of human impact during the late Holocene apparently provoked a reinforcement of the effects of climatic impulses. There are clear evidences for the participation of humans in the mobilization of sediments ; however, concerning the degree of influence it is hardly possible to differentiate between the factors humans and climate.

Mots clés  : Spanien, fluviale Dynamik, Rio Jarama, Rio Guadalete, Rio Guadalquivir, Westlicher Mediterranraum, Paläoumweltbedingungen, fluviale Archive, Klimawandel, Landschaftsentwicklung — Spain, fluvial dynamics, Jarama River, Guadalete River, Guadalquivir River, palaeoenvironmental conditions, Western Mediterranean, Fluvial archives, Climate change, Landscape evolution

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Page publiée le 22 décembre 2015, mise à jour le 10 mai 2019