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Universität zu Köln (2018)

Northeastern Iranian loess and its palaeoclimatic implications

Vlaminck, Stefan

Titre : Northeastern Iranian loess and its palaeoclimatic implications

Auteur : Vlaminck, Stefan

Université de soutenance : Universität zu Köln.

Grade : Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultät der Universität zu Köln 2018

Résumé partiel
Loess-palaeosol sequences (LPS) are valuable terrestrial archives for the characterization and reconstruction of late Pleistocene climate dynamics over wide areas. Within the Eurasian loess belt most scientific attention was attributed to the loess successions of southeastern Europe and Central Asia. Thus, considerable knowledge gaps remain to be closed for other regions. The loess deposits and LPS of northern Iran represent an important link between these two areas. However, previous investigations were based on coarse-meshed sampling and analyses and therefore provided only limited insights into the lithological properties of loess deposits, intercalated palaeosols and the resulting pedostratigraphy. This applies also to the provenance of loess, the degree of weathering and the genetic interpretation of palaeosols. Consequently, insights into palaeoclimate of northeastern Iran and its last interglacial-glacial landscape evolution are limited, impeding regional as well as supraregional correlations with palaeoclimatic archives and LPS from western and central Asia. The present dissertation aims at elaborating new records of lithological and palaeopedological properties of northeastern Iranian loess. Relative wind velocities during the periods of loess formation and the distance from the dust source are inferred from highly resolved grain-size analyses. The dust source itself is tentatively localized by means of immobile major elements. Moreover, palaeosols are to be identified and characterized in order to establish a regional pedostratigraphy of northeastern Iran. One focus is put on the detection of weakly developed palaeosols, as little is known about their existence and potential correlations with interstadials of MIS 3. A second focus is put on the thorough characterization of the MIS 5 pedo-complex. These foci provide evidence in order to distinguish between syngenetic and post-sedimentary palaeosols. Furthermore, marker horizons are identified and supplemented by luminescence dating results to establish a chronostratigraphic scheme and regional correlation of the LPS. Based on the results of the present dissertation the northeastern Iranian LPS are compared with palaeoclimatic archives from western and central Asia. This requires improved stratigraphical investigations and high-resolution sampling of three newly discovered loess exposures. The studied loess deposits are found along a modern precipitation gradient, since the profiles of Neka-Abelou and Toshan are located in the subhumid foreland of the Alborz Mountain range, whereas the Agh Band (Agh 1/2) profile is located in the so called Iranian loess plateau (ILP). The considerable number of sediment samples ( 4500) was used to provide new records on grain-size (laser-diffractometry), soil color (VIS spectrometry), carbonate content (MIRS) and rock magnetics (magnetic susceptibility) which are combined with micromorphological and geochemical findings.

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