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Les variations de niveau du lac de Van (Turquie) : Indicateurs morphosédimentaires, Implications paléoclimatiques et paléohydrologiques

Abstract : The Lake Van (1648 m) is a palaeoclimatic and palaeoenvironmental reference for the Middle East. According to previous studies, its evolution since the last 20000 years appears close-related to post-Glacial climatic changes. Our PhD thesis aimed at reconstructing the ancient lake levels during more than 100 000 years, a period corresponding to the end of the Upper Pleistocene. We adopted a geomorphological approach including sedimentary facies and stratigraphic analysis, altimetric measurements on field, dating, allowed to interpret sedimentary and morphological records still preserved in the three studied valleys (rivers Bendimahi, Karasu and Engil) in the eastern part of the lake basin. Our results show that the Lake Van has known high amplitude variations of its volume, with three transgressions, each one followed by important regressions. The highest lake level recorded (≥1750 m, i.e. more than 100 m above the present lake level) seems to belong to the end of the previous Interglacial, as suggested by an OSL dating (>117 ka) and post-dated by a plinian fall and a travertine (110 ka). This transgression does not respond to climate forcing, but to palaeohydrographical changes related to volcanic activity in the south-west part of the lake. Between this old transgression and the Late Glacial Maximum, the Lake Van experienced two other large transgressions (cycles II and III) separated by a marked regression. This latter induced an incision of the former lacustrine sediments and the development of erosional terraces. These transgressions (cycles II and III) respond to climate forcing. The cycle II (estimated age of 40-30 ka) reached the maximum elevation controlled by the 1735 m topographical threshold. The cycle III is subdivided into two transgressions belonging to the LGM (26-25 ky cal BP and 21-20 ky cal. BP) with a first peak at ≥1700 m and a second at ≥1706 m. After the cycle III, a low level regression (15 ka, <1648 m) was followed by the cycle IV transgression which has reached levels close to the present lake level.
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Submitted on : Thursday, September 15, 2011 - 4:40:38 PM
Last modification on : Tuesday, January 19, 2021 - 11:08:17 AM
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Aurelien Christol. Les variations de niveau du lac de Van (Turquie) : Indicateurs morphosédimentaires, Implications paléoclimatiques et paléohydrologiques. Géographie. Université Paris-Diderot - Paris VII, 2011. Français. ⟨tel-00624067⟩

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