Bathymetric Survey of Lake Van (BathyVan), Turkey - finding answers to objectives not directly addressed by ICDP drilling at Lake Van
Zusammenfassung der Projektergebnisse
Lake Van in Eastern Anatolia (Turkey) is the fourth largest terminal lake in the world with a surface area of 3,574 km², a volume of 607 km³, a maximum depth of 450 m, and a maximal length of 130 km WSW-ENE. As Lake Van (Eastern Anatolia) can act as a key site for the investigation of the Quaternary climatic evolution of the Near East, an ICDP drilling campaign was successfully conducted in summer 2010. Due to finical limitations, only 2 out of 5 primary proposed sites were drilled leaving some of the key questions of the drilling proposal nearly untouched including lake-level history and tectonics. Hence, we collected new seismic and bathymetric data in order to address several questions of the original ICDP proposal. The new seismic data show that the major sub-basins (the Tatvan Basin and the Northern Basin) of Lake Van, are bound by NE-trending oblique faults with major dip-slip components. They formed during the past ~600 ka in response to extension during northward collision of the Arabian plate with the Eurasian plate. Rapid extension and subsidence during early lake formation lead to the graben and half-graben opening of the respective basins. Seismic data in combination with the drill sites allowed to reconstruct a detailed lake level curve. The minimum lake level occurred at about ca. 600 ka when the lake level was about 610 m below the current lake level (mbll). This period marks the initiation of modern Lake Van, which exists as permanent water body since then. A delta clinoform observed at 210 mbll is associated with Last Glacial Maximum (LGM) lowstand. All other major lowstand periods in Lake Van occurred during glacial periods, suggesting climatic control on water level changes, i.e. greatly reduced precipitation led to lower lake levels. The lake level lowstand during the LGM is clearly documented by several sublacustrine channels and a dendritic network of small incisions. These features are mainly found down to water depths of 200 m. The lake level fall to this depth during the LGM exposed the shelf and led to the river incision and fluvial network development on the shelves. The subsequent rapid transgression of the lake drowned these valleys causing channel abandonment. The new map of the Northern Ridge clearly proofs that lake level drops of ~ 150 m separates the Tatvan and Northern Basins. This nicely explains the contrasting pore water data from these to basins measured during the drilling campaign. The new multibeam data delineates hundreds of topographic mounds in the northern part of the lake, on the shelf off Adilcevaz. These mounds represent microbialites, which were already described during previous investigations. Our new data show, for the first time, that the distribution of microbialites is mainly controlled by tectonics as evidenced by their alignment along faults and/or cracks. The faults are probably acting as pathways for Ca-rich groundwaters from the Miocene Adilcevaz Limestone below the lake floor.
Projektbezogene Publikationen (Auswahl)
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(2013) Sedimentary evolution of Lake Van (Eastern Turkey) reconstructed from high resolution seismic investigations. International Journal of Earth Sciences,102 (2), 571–585
Cukur, D., Krastel, S., Schlüter, F.D., Demirbağ, E., Imren, C., Niessen, F., Toker, M., PaleoVan-Working Group
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(2013) Seismic evidence of shallow gas from Lake Van, eastern Turkey. Marine and Petroleum Geology, 48, 341-353
Cukur, D., Krastel, S., Tomonaga, Y., Çağatay, N., Meydan, A.F., The PaleoVan Science Team
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(2014) Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years. Sedimentology, 61, 1830-1861
Stockhecke, M., Sturm, M., Brunner, I., Schmincke, H.-U., Sumita, M., Kipfer, R., Cukur, D., Kwiecien, O., Anselmetti, F.S.
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(2014) Seismic stratigraphy of Lake Van, eastern Turkey. Quaternary Science Reviews, 104, 63-84
Cukur, D., Krastel, S., Schmincke, H.-U., Sumita, M., Çağatay, N., Meydan, A.F., Damci, E., Stockhecke, M.
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(2014) Water level changes in Lake Van, Turkey, during the past ca. 600 ka: climatic, volcanic and tectonic controls. Journal of Paleolimnology, 52, 201-214
Cukur, D., Krastel, S., Schmincke, H.-U., Sumita, M., Tomonaga, Y., M.N. Çağatay
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(2015) Evidence of extensive carbonate mounds and sublacustrine channels in shallow waters of Lake Van, eastern Turkey, based on high-resolution chirp subbottom profiler and multibeam echosounder data. Geo-Marine Letters
Cukur, D., Krastel, S., Çağatay, N., Damci, E., Meydan, A.F., Kim, S.P.
