Morphometric and geological features of karstic depressions in gypsum (Sivas,Turkey)     

İnan Keskin  Işık Yılmaz 《Environmental Earth Sciences》2016,75(12):1040

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Estimation of the local financial costs of flood damage with different methodologies in Unye (Ordu), Turkey     

Beden  Neslihan  Ulke Keskin  Asli 《Natural Hazards》2021,108(3):2835-2854

The aim of this study was to conduct flood analysis with digital modeling systems and estimate the total flood damage in a built-up area. The Ceviz Stream basin, which is located in Unye (Ordu) district in the Eastern Black Sea region of Turkey, was selected as the study area. A 1D/2D coupled flood modeling software MIKE FLOOD was used in flood analysis. According to the modeling results, water depth and velocity maps are produced for maximum Q₅₀, Q₁₀₀, Q₅₀₀ and Q₁₀₀₀ discharge scenarios in the most downstream section of the Ceviz Stream. At the projected Q_50, Q₁₀₀, Q₅₀₀ and Q₁₀₀₀ maximum flow rates, approximately 9.75%, 23.0%, 30.0% and 32.25% of that section of the study area were estimated to be negatively affected by floodwaters. In order to examine the financial magnitude of the effects of flooding, the Huizinga, van Eck and Kok, ICBR and Pistrika and Jonkman damage estimation methodologies were applied, with the highest financial costs estimated with the Pistrika and Jonkman method.

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Early Miocene adakite-like volcanism in the Balkuyumcu region, central Anatolia, Turkey: Petrology and geochemistry   总被引：1，自引：0，他引：1  

Elif Varol  Abidin Temel  Alain Gourgaud  Herve Bellon 《Journal of Asian Earth Sciences》2007,30(5-6):613-628

The Balkuyumcu region, located in the southwestern part of Ankara in the Izmir-Ankara suture zone (central Anatolia, Turkey), consists of basic andesitic, andesitic, dacitic and rhyolitic rocks extruded during the Early Miocene (20–22 Ma) as a result of post-collisional volcanism. Balkuyumcu volcanic rocks can be divided into two groups on the basis of their mineralogy and composition: The basic andesitic (BA) and andesitic, dacitic and rhyolitic (ADR) groups. The ADR and BA group of rocks have adakite-like and calc-alkaline characteristics, respectively. The ADR group has higher SiO₂ content, Sr/Y and La/Yb ratios and low MgO, Mg#, Y and Yb contents than the BA group. Both groups have nearly the same Sr, Nd isotopic compositions and display similar normalized multi-element patterns with enrichments in LILE and LREE, depletions in Nb, Ti, Zr, P and a lack of Eu anomalies. Major, trace element and Sr, Nd isotopic data indicate that both groups of rocks were derived from the same source but affected by different magmatic processes during ascent. The adakite-like rocks may have been produced by partial melting of thickened lower continental crust. Fractional crystallization also played a major role in their formation. However, the BA group rocks were derived from partial melting of lower continental crust that was probably delaminated. These rocks appear to have had limited interaction with mantle peridodite during ascent to the surface.  相似文献   

Erratum: Geochronology of Late Cenozoic volcanism in the area of Lake Van,Turkey: An example of developmental dynamics for magmatic processes [Doklady earth sciences, 433(2), pp. 1031–1037]     

Lebedev  V. A.  Sharkov  E. V.  Keskin  M.  Oyan  V. 《Doklady Earth Sciences》2010,435(1):1548-1554

An isotope-geochronological study has been performed to examine the products of Late Cenozoic collision volcanism on the northern coast of Lake Van, Turkey. We obtained 45 new K—Ar dates, based on which the principal time characteristics of volcanic activity in the region have been determined. Volcanic activity in the northern coast of Lake Van has lasted ∼15 myr; it has had an expressed discrete nature, when periods of intense volcanic activity alternated with long-lasting pose periods. Four stages of Neogene—Quaternary volcanism have been identified: Middle Miocene (15.0—13.5 Ma), Late Miocene (10—9 Ma), Pliocene (5.8—3.7 Ma), and Quaternary (1.0—0.4 Ma). The average duration of the stages was 1—2 myr; the stages were separated from each other with periods of inactivity of approximately equal lengths (∼3 myr). For each of the Pliocene and Quaternary stages, three additional phases of volcanism have been identified, which were separated from each other with short time intervals (a few hundred thousand years). The last burst of volcanic activity in the study area occurred ∼400 ka; similar to Quaternary volcanism in general, it was not characterized by a high intensity. An important result of the studies performed was to confirm the existence of a separate Middle Miocene stage of collision volcanism for the Caucasian—Anatolian Segment of the Alpine Fold Belt. New geochronological data generated presented in this paper indicate that Neogene—Quaternary volcanism in this portion of the belt started much earlier (∼15 Ma) than assumed by the majority of the previous researchers.  相似文献   

Light variations and flares on V471 tauri     

Z. Tunca  V. Keskin  S. Evren  C. Ibanoglu  M. C. Akan 《Astrophysics and Space Science》1993,204(2):297-304

Two-colour photometric observations of the white-dwarf and K-dwarf eclipsing binary V471 Tau were made during the last four years. The resulting light curves and thirteen timings of mid-eclipse are presented. During the observations two flares were obtained on September 23 and December23, 1992. Both events occurred just after the fourth contact. The increment in the brightness was measured as 0 _. ^m 067. The energy liberated by the flare was computed to be 5.43 × 10³² erg s^–1 in the JohnsonB band, which amounts 1.13 times that of the total radiation of the K-dwarf.  相似文献   

Hydrogeochemistry and reservoir characterization of the Konya geothermal fields,Central Anatolia/Turkey     

Ayşen Davraz  M. Tahir Nalbantçılar  Simge Varol  İsmail Önden 《Chemie der Erde / Geochemistry》2022,82(2):125867

A conceptual model with water samples from ten geothermal fields (?smil, Ilg?n (Çavu?cugöl), Tuzlukçu-Ak?ehir, Seydi?ehir and Kavakköy, Hüyük, Ere?li-Akhüyük, Kad?nhan?, Cihanbeyli, Karap?nar and Bey?ehir) in the province of Konya defined the geothermal system. Carbonates, quartzite and marbles of Paleozoic metamorphics are the reservoir rocks and the heating sources are igneous rock intrusions and geothermal gradient. The variable thermal water (CaMgHCO₃, CaSO₄, NaSO₄, CaHCO₃, CaNaHCO₃, NaCl and CaNaClHCO₃) had EC and temperature between 177.8 and 56,100 μS/cm and between 18.3 and 44 °C, respectively. Ca²⁺ in geothermal fluids are associated with marble and carbonate rocks and the high chloride shows direct connection with deep geothermal system, and prolonged contact with evaporite rocks. Sulphate originates from dissolution of and oxidation of sulphate and sulphur-bearing minerals. The high As, B, F and Mn concentration in some thermal water samples were determined as 85 μg/l, 148.56 mg/l, 3.01 mg/l and 208.13 mg/l, respectively. Reservoir temperatures computed by Na/K geothermometers were between 85.37–158.89 °C for Ak?ehir thermal waters and 58.78–90.45 °C for Ere?li thermal waters. The maximum reservoir temperature of other geothermal waters was 75 °C by the silica geothermometers.  相似文献   

Recent photoelectric photometry of the newly discovered eclipsing system BD + 13o4708     

Varol Keskin  M. Can Akan 《Astrophysics and Space Science》1989,155(1):113-123

Two-colour photoelectric photometry of the eclipsing binary BD + 13^o4708 was carried out. Several features such as asymmetry in the branches, light difference between the maxima, an eccentric orbit, a dip around phase 0.2 are distinctive. The new light elements of the system were computed using also the previous times of primary minima given by Walker (1988).  相似文献   

The occurrence and significance of beekite in Palaeocene alluvial-fan deposits in central Anatolia,Turkey     

Nizamettin Kazanci  Baki Varol 《地学学报》1993,5(1):36-39

The Palaeocene alluvial-fan succession in central Anatolia, Turkey, contains three isolated zones of beekite-encrusted clasts. Each zone is 3–5 m thick and c. 1 km long. Beekite is developed as thin (1–5 mm), concentric silica rings formed by replacement and encrustation of carbonate clasts. The formation of beekites requires a relatively long time, with non-deposition and fluctuating arid/semiarid conditions. The significance of beekite is thus analogous to that of silcrete. The presence of beekite encrustation within the Palaeocene alluvial-fan succession indicates considerable breaks in sedimentation in the eastern part of the basin, and this inference is supported by the lower thickness of the alluvium in the east.  相似文献   

The geochronology and origin of mantle sources for late cenozoic intraplate volcanism in the frontal part of the Arabian plate in the Karacadağ neovolcanic area of Turkey. Part 1. The results of isotope-geochronological studies     

M. Keskin  A. V. Chugaev  V. A. Lebedev  E. V. Sharkov  V. Oyan  O. Kavak 《Journal of Volcanology and Seismology》2012,6(6):352-360

This paper considers results from isotope-geochronological (K-Ar) studies of the products of Neogene-Quaternary volcanism in the Karacada? area, which is situated within the northern frontal part of the Arabian plate. It was found that magmatic activity has been evolving at this location for at least the last 11–10 Myr and was distinctly discrete in character. Three stages of volcanism have been identified: (I) Early or Miocene, ～11–6.7 Ma; (II) Middle or Pliocene-Early Quaternary, 4–1 Ma; and (III) Late or Late Quaternary, 0.4–0.1 Ma. The most recent manifestations of magmatic activity in the region date back to about 100000 years ago. An analysis of the spatial distribution of volcanic centers of different ages in the Karacada? neovolcanic area shows that the magmatism of that region involved a lateral migration of activity from northwest to southeast along a major regional tectonic fault. The migration was caused by the movement of local tension zones where the lithosphere was thinner and deep-seated mantle magmas were ascending.  相似文献   

Heavy metal pollution in the surrounding ore deposits and mining activity: a case study from Koyulhisar (Sivas-Turkey)   总被引：1，自引：1，他引：0  

Tülay Ekemen Keskin  Sonay Topta? 《Environmental Earth Sciences》2012,67(3):859-866

The oxidation of sulfide minerals generates acidic waters containing high levels of SO₄ and Fe. The study area has active Pb?CZn?CCu mining. It is thought that the surface/subsurface/underground sulfide minerals in the region generally contribute to the acidification of groundwater. Low pH values are also responsible for dissolved metals (Al, Fe, Mn, SO₄, Pb, Zn) in the groundwater and river. Furthermore, current mining wastes have affected concentrations of trace elements in the water. High Fe and Mn concentrations are generally found in the spring which has acidic and low Eh values, while Al, Fe and Mn concentrations in the acidic waters show notable increases with the maximum values reaching 8,829, 19,084 and 1,708?ppb, respectively. These values exceed the Turkish drinking water standard of 200, 200 and 50?ppb, respectively.  相似文献