[Krastel] Bathymetric Survey of Lake Van (BathyVan), Turkey - finding answers to objectives not directly addressed by ICDP drilling at Lake Van
German Title: Bathymetric Survey of Lake Van (BathyVan), Turkey - finding answers to objectives not directly addressed by ICDP drilling at Lake Van
Current Status: completed with report
Main Applicant:Prof. Dr. Sebastian Krastel
Dr. Deniz Cukur
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. Preliminarily first core analyses show that the drilled sediments contain 500,000 years of paleo-environmental and volcanic/geodynamic history. Due to financial 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, tectonics, and the interactions between man and environment. First results from the drilling campaign, such as tephra deposits formed underwater and contrasting pore water profiles from the drilled sites, bring up new questions, including the occurrence of sub-aquatic volcanic activity and the hydro-geological evolution of individual basins. We propose to address these questions (tectonics, sub-aquatic volcanology, geo-hazards, lake level history, seepage, and sub-aquatic archeology) by collecting a high resolution bathymetric data set of Lake Van. The work should be complemented by seismic data acquisition in selected areas and gravity coring of specific features, such as historic slides and sediments around faults and volcanic edifices. The new data in combination with the drilling and other already available data will allow addressing several questions of the original ICDP proposal, hence, contributing significantly to the overall success of the entire drilling campaign.
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.
Schmincke, Hans-Ulrich, Sumita, Mari, Cukur, Deniz (2018). "Large-volume basaltic hyaloclastite eruption along a propagating land/lake lithosphere fracture at Lake Van (Eastern Anatolia): impact of volcanism on the evolution of Lake Van V" Bulletin of Volcanology 80: 82 p1-23
Cukur, Deniz, Krastel, Sebastian, Tomonaga, Yama, Schmincke, Hans-Ulrich, Sumita, Mari, Meydan, Ayşegül Feray, Çağatay, M Namık, Toker, Mustafa, Kim, Seong-Pil, Kong, Gee-Soo (2017). "Structural characteristics of the Lake Van Basin, eastern Turkey, from high-resolution seismic reflection profiles and multibeam echosounder data: geologic and tectonic implications" International Journal of Earth Sciences (Geologische Rundschau) 106 p239-253
Toker, Mustafa, Sengor, AM Celal, Schluter, Filiz Demirel, Demirbag, Emin, Cukur, Deniz, Imren, Caner, Niessen, Frank, PaleoVan-Working Group (2017). "The structural elements and tectonics of the Lake Van basin (Eastern Anatolia) from multi-channel seismic reflection profiles" Journal of African Earth Sciences 129 p165-178
Cukur, Deniz, Krastel, Sebastian, Çağatay, M. Namık, Damcı, Emre, Meydan, Aysegül Feray, Kim, Seong-Pil (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 35 p329-340
Cukur, Deniz, Krastel, Sebastian, Schmincke, Hans-Ulrich, Sumita, Mari, Çağatay, M. Namık, Meydan, Aysegül Feray, Damcı, Emre, Stockhecke, Mona (2014). "Seismic stratigraphy of Lake Van, eastern Turkey" Quaternary Science Reviews 104 p63-84
Cukur, Deniz, Krastel, Sebastian, Schmincke, Hans Ulrich, Sumita, Mari, Tomonaga, Yama, Namık Çağatay, M. (2014). "Water level changes in Lake Van, Turkey, during the past ca. 600 ka: climatic, volcanic and tectonic controls" Journal of Paleolimnology p201-214