Limnologische Untersuchung Einiger Anatolischer Seen

Nümann, Wilhelm

doi:10.1002/iroh.19600450103

Cited by 9 publications

(4 citation statements)

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“…(2012) give for the southern block of the northern branch of the NAF (NNAF) an average tectonic uplift rate of 0.3 ± 0.05 mm/yr for the last 200 ka. Several authors suggest that the changes in lake level have more influence on the elevation of the terraces, than the faults observed around the lake ( Öztürk et al, 2009;Nümann, 1960). Moreover, the geological history of the basin and its connection with the Marmara Sea are intensely debated.…”

Section: Impact Of Tectonics In the Iznik Basinmentioning

confidence: 99%

Paléosismologie lacustre et géophysique appliquées au lac d'Iznik (Turquie) : contribution à l'étude de la branche médiane de la Faille Nord-Anatolienne

Gastineau¹

2022

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In Turkey, the North Anatolian Fault (NAF), which accommodates the westward movement of Anatolia with respect to Eurasia, is one of the most active faults in the world.A series of earthquakes (M>6.8) have propagated from east to west during the last century. The next rupture seems to be expected in the Marmara region, south of Istanbul.However, the geometry of this fault becomes more complex in this region. It splits into three branches, one of which borders the southern Marmara Sea and Lake Iznik. This median segment of the NAF (MNAF) has very low seismicity today, and low displacements are recorded by GPS, which leads to considering it inactive. However, the city of Iznik, the cradle of Christianity, has preserved valuable historical evidence in contrast to its observations. Six destructive earthquakes have been mentioned since antiquity. To better understand the seismic hazard in this area, it is necessary to catalogue the seismic activity and locate past ruptures.The use of lakes as natural seismometers has already proved its worth. This thesis has identified two active faults after different geophysical and coring campaigns in Lake Iznik.The first part of this work focuses on the antic period. The study of short (<4m) sediment cores sampled on both sides of the E-W fault passing near the Iznik city shows that the last rupture, dating from 1065 CE, corresponds to a devastating historical earthquake.In addition to this localised rupture, numerous other event deposits are present in the sediments (laterally and temporally). This thesis has (1) differentiated between flood deposits and deposits related to slope destabilisation, most of which are associated with high confidence with historical earthquakes; (2) shown that different types of deposits are recorded for the same earthquake. At the lake scale, the difference in depositional type depends on the source-core distance. One type of deposition is only observed for the 1065 CE earthquake, which takes place in the lake, unlike the others, suggesting that this type of deposition may depend on ground motion parameters. This thesis also presents a compilation of marine and lake palaeoseismological work carried out at the scale of the northwestern part of the NAF, allowing discussion of the limitations of this method. Thus, the concept of basin sensitivity (relationship between the sedimentation rate and the triggering of a slope destabilisation due to an earthquake) does not work in the marine environment, contrary to the lacustrine environment. It is also shown that Lake Iznik records earthquakes from both the NNAF and the MNAF, while the Sea of Marmara seems to record only earthquakes from the NNAF. We also show that contrary to what was previously thought, no earthquakes of Mw>5 have been recorded on the MNAF since the 11 th century, suggesting a significant accumulation of stress on this fault since then. The last part of this thesis focuses on the long term (>2000 years) using seismic and core data. Significant lake level variations have been revealed for mo...

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Section: Impact Of Tectonics In the Iznik Basinmentioning

confidence: 99%

Paléosismologie lacustre et géophysique appliquées au lac d'Iznik (Turquie) : contribution à l'étude de la branche médiane de la Faille Nord-Anatolienne

Gastineau¹

2022

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“…Regional average temperatures vary between 7°C in winter and 25°C in summer (Fig. ), with extremes of ca 5°C and 30°C (Nümann, ; Viehberg et al ., ). At the catchment scale, water loss is dominated by surface discharge (50%) and evapotranspiration (40%), while less than 10% of rainfall feeds groundwater (Eisenlohr, ).…”

Section: Introductionmentioning

confidence: 99%

“…The low permeability and high topographic gradients of the catchment lead to rapid surface water runoff towards the lake from approximately 30 ephemeral streams. Even the Kara River, the main river inflow to Lake Iznik, nearly dries out during the summer (Nümann, ; Wester, ; Franz et al ., ). In conclusion, fast surface and subsurface discharges during the cold season dominate the water inflow and primary solute input to Lake Iznik (Eisenlohr et al ., ; Pasvanoglu et al ., ; Simsek et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Aragonite and calcite preservation in sediments from Lake Iznik related to bottom lake oxygenation and water column depth

2016

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This study examines the forcing mechanisms driving long‐term carbonate accumulation and preservation in lacustrine sediments in Lake Iznik (north‐western Turkey) since the last glacial. Currently, carbonates precipitate during summer from the alkaline water column, and the sediments preserve aragonite and calcite. Based on X‐ray diffraction data, carbonate accumulation has changed significantly and striking reversals in the abundance of the two carbonate polymorphs have occurred on a decadal time scale, during the last 31 ka cal bp. Different lines of evidence, such as grain size, organic matter and redox sensitive elements, indicate that reversals in carbonate polymorph abundance arise due to physical changes in the lacustrine setting, for example, water column depth and lake mixing. The aragonite concentrations are remarkably sensitive to climate, and exhibit millennial‐scale oscillations. Extending observations from modern lakes, the Iznik record shows that the aerobic decomposition of organic matter and sulphate reduction are also substantial factors in carbonate preservation over long time periods. Lower lake levels favour aragonite precipitation from supersaturated waters. Prolonged periods of stratification and, consequently, enhanced sulphate reduction favour aragonite preservation. In contrast, prolonged or repeated exposure of the sediment–water interface to oxygen results in in situ aerobic organic matter decomposition, eventually leading to carbonate dissolution. Notably, the Iznik sediment profile raises the hypothesis that different states of lacustrine mixing lead to selective preservation of different carbonate polymorphs. Thus, a change in the entire lake water chemistry is not strictly necessary to favour the preservation of one polymorph over another. Therefore, this investigation is a novel contribution to the carbon cycle in lacustrine systems.

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“…Although no official record or publication exist, it seems that P. handlirschi became extinct in the early 1970s for the same reason as A. akili namely the predatory effect of S. lucioperca that was introduced in Lake Eğirdir in 1955 (Numann 1960(Numann : 40, 1961. The extinction process of P. handlirschi took approximately 25 years, that of A. akili nearly 15 years.…”

Section: Introductionmentioning

confidence: 99%

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Küçük¹

2012

Turk. J. Fish. Aquat. Sci.

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The extinction process of the endemic inland fishes of Turkey, Alburnus akili (gövce) and Pseudophoxinus handlirschi (kavinne) is studied. The assessment is based on the field studies and observations during the last two decades , along with a survey of the literature. The piscivorous effect of Sander lucioperca introduced into lakes Eğirdir and Beyşehir has been concluded to be the major factor in the disappearance of Pseudophoxinus handlirschi in the early 1970s and of Alburnus akili after 1985.

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Limnologische Untersuchung Einiger Anatolischer Seen

Cited by 9 publications

References 1 publication

Paléosismologie lacustre et géophysique appliquées au lac d'Iznik (Turquie) : contribution à l'étude de la branche médiane de la Faille Nord-Anatolienne

Paléosismologie lacustre et géophysique appliquées au lac d'Iznik (Turquie) : contribution à l'étude de la branche médiane de la Faille Nord-Anatolienne

Aragonite and calcite preservation in sediments from Lake Iznik related to bottom lake oxygenation and water column depth

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