2012

Van Gölü’nde Sedimantasyon Hızının Fizyografik Değişimi, Doğu Anadolu/Türkiye

Gölsel çökel istifler geçmişte olmuş iklimsel, tektonik, volkanik, su seviyesi değişimleri ve sedimantasyon hızıgibi değişikliklerin kayıtlarının tutulduğu önemli arşivlerdir. Van Gölü dip çökelleri karasal olarak uzun birgeçmişi simgelemesi nedeni ile bu tip çalışmalar için karakteristik bir örneği temsil etmektedir. Gölsel çökel istiflerfarklı disiplinlerde çalışılırken kronolojik olarak yaşlandırılması gerekmektedir. Bu açıdan farklı birçokyaşlandırma metodu mevcuttur. Bu çalışma kapsamında, Van Gölü’nün farklı fizyografik bölgelerinden alınan altıadet kısa karot üzerinde dengeüstü 210Pb aktiviteleri hesaplanmış ve CRS modeline göre ortalama sedimantasyonhızı belirlenmiştir. 137Cs aktivitesi bu çalışma kapsamında kronostratigrafik referans (1963, 1986) olarak kabuledilmiş ve hesaplanan sedimantasyon oranları ile uyumlu bulunmuştur. Hesaplanan sedimantasyon hızları 0.5mm/yıl ile 1.3 mm/yıl arasında değişmektedir. Sedimantasyon hızlarındaki farklılığın sadece su derinliği ve drenajhavzası kontrollü olmadığı bununla birlikte göl tabanındaki morfolojik unsurların kontrolü altında olduğu ortayakonmuştur.

Physiographic Variations of Sedimentation Rate in Lake Van, Eastern Anatolia/Turkey

Lacustrine sedimentary sequences are important archives that keep records of past climatic, tectonic, volcanic, lake level and sedimentation rate changes. Lake Van sediments represent a characteristic example of this type research because it represents a long terrestrial history. The lacustrine sediments should be dated chronologically while working in different disciplines. There are many different dating methods. In this study, on the six cores taken from the different physiographic regions of Lake Van, unsupported 210Pb activities were calculated and the average sedimentation rate was determined according to the CRS model. 137Cs activity was accepted as chronostratigraphic marker (1963, 1986) and it was found that the dates are compatible with the calculated sedimentation rates. The calculated sedimentation rates are between 0.5 mm/year and 1.3 mm/year. The differences in sedimentation rates were not only controlled by water depth and drainage basin, but also by the morphological elements at the lake basin.

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[1] Appleby P.G. 2008. Three decades of dating recent sediments by fallout radionuclides: a review. Holocene, 18 (1): 83-93.
[2] Appleby P.G., Oldfield F. 1978. The calculation of lead-219 dates assuming a constant rate of supply of unsupported 210Pb to the sediment. Catena, 5 (1): 1-8.
[3] Cukur D., Krastel S., Tomonaga Y., Cagatay M.N., Meydan A.F. 2013. Seismic evidence of shallow gas from Lake Van, eastern Turkey. Marine and Petroleum Geology, 48: 341-3 53.
[4] Cukur D., Krastel S., Schmincke H.U., Sumita M., Cagatay M.N., Meydan A.F., Damcı E., Stockehecke M. 2014. Seismic stratigraphy of Lake Van, eastern Turkey. Quaternary Science Reviews, 104: 63-84.
[5] Cukur D., Krastel S., Tomonaga Y., Schmincke H.U., Sumita M., Meydan A.F., Çağatay M.N., Toker M., Kim S.P., Kong G.S., Horozal Ş. 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 Science, 106 (1): 239-253.
[6] Kempe S., Kazmierczak J., Landmann G., Konuk T., Reimer A., Lipp A. 1991. Largest Known Microbialites Discovered in Lake Van, Turkey. Nature, 349 (6310): 605-608.
[7] Reimer A., Landmann G., Kempe S. 2009. Lake Van, Eastern Anatolia, Hydrochemistry and History. Aquatic Geochemistry,15 (1-2): 195-222.
[8] Degens E.T., Wong H.K., Kempe S., Kurtman F.A. 1984. Geological Study of Lake Van, Eastern Turkey. Geologische Rundschau, 73 (2): 701-734.
[9] Lemcke G., Sturm M. 1997. delta O-18 and trace element measurements as proxy for the reconstruction of climate changes at Lake Van (Turkey): Preliminary results. Nato Asi Ser Ser I., 49: 653-678.
[10] Keskin M. 2003. Magma generation by slab steepening and breakoff beneath a subductionaccretion complex: An alternative model for collision-related volcanism in Eastern Anatolia, Turkey. Geophysical Research Letters, 30 (24): 1-4.
[11] Sengor A.M.C., Ozeren S., Genc T., Zor E. 2003. East Anatolian high plateau as a mantlesupported, north-south shortened domal structure. Geophysical Research Letters, 30 (24).
[12] Sumita M., Schmincke HU. 2013. Impact of volcanism on the evolution of Lake Van I: evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past > 400,000 years. Bulletin of Volcanology, 75 (5).
[13] Sumita M., Schmincke H.U. 2013. Impact of volcanism on the evolution of Lake Van II: Temporal evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past ca. 0.4 Ma. Journal of Volcanology Geothermal Research, 253: 15-34.
[14] Litt T., Anselmetti F.S. 2014. Lake Van deep drilling project PALEOVAN. Quaternary Science Reviews, 104: 1-7.
[15] Wong H.K, Degens E.T. 1978. The bathymetry of Lake Van: a preliminary report. In: Degens ET, Kurtman F, editors. Geology of Lake Van169. Anakara: M.T.A Press, 20-7.
[16] Litt T., Krastel S., Sturm M., Kipfer R., Orcen S, Heumann G., Franz S.O., Ülgen U.B., Neissen F. 2009. 'PALEOVAN', International Continental Scientific Drilling Program (ICDP): site survey results and perspectives. Quaternary Science Reviews, 28 (15-16): 1555-1567.
[17] Krishnaswamy S., Lal D., Martin J.M., Meybeck M. 1971. Geochronolgy of lake sediments. Earth Planet Science Letters, 11 (1-5): 407-414.
[18] Stockhecke M., Sturm M., Brunner I., Schmincke H.U., Sumita M., Kipfer R., Cukur D., Kwiecien O., Anselmetti F.S. 2014. Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years. Sedimentology, 61 (6): 1830-1861.
[19] Landmann G., Reimer A., Lemcke G., Kempe S. 1996. Dating Late Glacial abrupt climate changes in the 14,570 yr long continuous varve record of Lake Van, Turkey. Palaeogeography Palaeoclimatology Palaeoecology, 122 (1-4): 107-118.
[20] Landmann G., Reimer A., Kempe S. 1996. Climatically induced lake level changes at Lake Van, Turkey, during the Pleistocene/Holocene transition. Global Biogeochemical Cycles, 10 (4): 797- 808.