Deterministic approach to the seismic hazard of dam sites in Kızılırmak basin,Turkey

Dams constructed on the seismically active regions have a high-risk potential for downstream life and property. Strong ground motion can result in instability of the dam and strength loss of foundation. Active faults within the foundation of dam have the potential to cause damaging displacement of the structures. Appropriate design measures should be considered to obtain rational solution to the problem of catastrophic release of water from the reservoir, and especially to resist earthquake loads. Safety concerns for dams under the earthquake loads involve the seismic hazard evaluation of dam site for the overall stability of structure. Various types of analyses can be used, ranging from a simplified analysis to more complex procedures based on ground motion parameters and response spectra. This paper briefly evaluates seismic hazard analyses for dam structures, and introduces the analyses for thirty-six dams with height ranging from 15 to 195 m in Kızılırmak basin, Turkey. The seismic hazard analyses have indicated that peak ground acceleration varies within a wide range (0.09–0.45 g) for the dam sites of the basin.     

Kinematics of the Malatya–Ovacık Fault Zone

We investigate the left-lateral slip on the 240-km-long, NE–SW-trending, Malatya–Ovacık fault zone in eastern Turkey. This fault zone splays southwestward from the North Anatolian fault zone near Erzincan, then follows the WSW-trending Ovacık valley between the Munzur and Yılan mountain ranges. It bends back to a SW orientation near Arapkir, from where we trace its main strand SSW beneath the Plio-Quaternary sediment of the Malatya basin. We propose that this fault zone was active during ∼5–3 Ma, when it took up 29 km of relative motion between the Turkish and Arabian plates; it ceased to be active when the East Anatolian fault zone formed at ∼3 Ma. The geometry of the former Erzincan triple junction, which differs from the modern Karlıova triple junction, where the North and East Anatolian fault zones intersect, suggests a possible explanation for why slip on the Malatya–Ovacık fault zone was unable to continue. We interpret the SW- and SSW-trending segments of the Malatya–Ovacık fault zone as transform faults, which define an Euler pole ∼1 400 km to the southeast. Its central part along the Ovacık valley, which is ∼30° oblique to the adjoining transform faults, is interpreted as the internal fault of a stepover. The adjoining mountain ranges, which now rise up to ∼3 300 m, ∼2 000 m above the surrounding land surface, are largely the result of the surface uplift which accompanied the components of shortening and thickening of the upper crustal brittle layer that occurred around this stepover while the left-lateral faulting was active.     

Estimation of environmental impacts on the water quality of the Tahtalıdam watershed in İzmir, Turkey

Water pollution is a widespread problem in different areas of the world. Some of these problems originated from point contamination sources and widespread contaminant outlet sources which are observed in every country. The major elements and chemical loads of surface water have been dominated by constituents derived directly or indirectly from human activities and/or industrial practices that have increased additives in the last several decades. The point sources of contamination may result from the direct wastewater discharges to the dam sites, which are considered to be the most commonly encountered water pollution problems. One of these problems is the eutrophication process which usually occurs in the static water mass of lakes and other surface water reservoirs. This process may be caused by the continuous increase of nitrogen and phosphorus contents and decrease of O₂ level in water causing an anaerobic condition which may stimulate algae-growth flow in these water bodies, consequently reducing the quality of water. Of course, there are many research methods for determining the various kinds of water pollution. In this research, the hydrochemical parameters were evaluated to estimate the types of pollution sources, the level of pollution, and its environmental impacts on the Tahtal dam reservoir.     

Origin,petrogenesis and geodynamic implications of the early Eocene Altınpınar adakitic andesites in the eastern Sakarya Zone,northeastern Turkey

Early Cenozoic magmatism in the eastern Sakarya Zone (NE Turkey) provides an important constraint on the regional tectono-magmatic evolution of the region. Early Eocene syn-collisional adakitic rocks are observed as small stocks with outcropping areas commonly less than 10 km². This study presents petrography, whole-rock geochemistry and Sr-Nd-Pb isotope data, as well as in-situ ⁴⁰Ar/³⁹Ar age constraints on one of these adakitic andesites in the Altınpınar area of Gümüşhane, and discusses source region, petrological processes and geodynamic setting prevailed during their genesis. Andesites commonly show microlitic porphyric and vitrophyric porphyric textures, and include significant amounts of mafic microgranular enclaves (MMEs). Plagioclase, hornblende, Fe-Ti oxides and minor pyroxene are the main mineral phases. In-situ ⁴⁰Ar-³⁹Ar amphibole dating constrains the cooling age of andesites into a time span from 52.8 ± 1.3–48.8 ± 1.9 Ma. Andesites are medium to high-K calc-alkaline and display most of the signatures typical of those of the adakites. They are characterized by moderate MgO (1.7–4.1 wt%), low Y (9−14 ppm), Yb (0.9–1.5 ppm), and HREE and high Sr (325−964 ppm) contents, and high Sr/Y (36–76) ratios. ⁸⁷Sr/⁸⁶Sr_(t) (0.704948−0.705100) and ¹⁴³Nd/¹⁴⁴Nd_(t) (0.512588−0.512628) ratios are in the isotopic range of the adakites. All these geochemical and isotopic data suggest that the parental magma of adakitic andesites has been produced by partial melting of oceanic basalts under amphibole-eclogite facies conditions during the breakoff of the northern Neotethyan oceanic slab.     

A study on the bio-hydro mechanical effects of the tree roots on the Agaclı coal reclaimed – forested land

The research area that is in the north of Istanbul (Turkey) and it is a land of open pit coal mining residuals reclaimed and turned to forest in 1988–1989. The materials that are open pit mine spoils are formed by sandy loam, sandy clay loam, heavy loam and clay (noncalcareous Pliocene I sediments). Pseudoacacia (Robinia pseudoacacia), Maritima Pine (Pinus pinaster) and Stone Pine (Pinus pinea) are planted on these materials. The aims of this research were to determine the strength of the material provided by tree roots and evaluate the performance of the forestation practices at lands especially where open pit coal mining spoil (residual) materials piled up. The research has been performed at two stages. The first one was hydro-mechanical effect concerned about material moisture depletion as a result of transpiration and the second one was bio-mechanical effects due to strength parameters of the roots and their growth pattern within the material. All results were evaluated in relation to tensile strength and displacement curves due to pre and post failure behaviors of materials and root systems. The results showed the increase of the displacement of the material was the significant indicator of the bio-mechanics tensile strength of the material provided by the tree roots. The fast growing type of tree roots have stabilized the material up to a depth for 80–100 cm by covering the coal residual materials within 12 years.     

Geochemistry and Nd,Sr isotopes of the Pohrenk fluorites (Kırsehir-Turkey)

The Pohrenk fluorite mineralisation which makes up Central Anatolia’s most extensive fluorite region is Lutetian aged, and hosted in carbonate rocks that have undergone occasional karstification and silicification along a N–S fault trend. Fluid inclusion values and the position of fluorites in the Tb/La–Tb/Ca diagram show that mineralisation occurred in a hydrothermal environment with homogenisation temperatures ranging from 78.1–363°C. The presence of fluorite as a space filler in carbonate rocks and its association with silicification indicates that the solutions contained considerable amounts of Si alongside F (fluorine). The Pohrenk fluorite samples have ¹⁴³Nd/¹⁴⁴Nd values of between 0.512349 and 0.512497, whilst ⁸⁷Sr/⁸⁶Sr values vary between 0.708161 and 0.708772. These values indicate a mantle origin where continental contamination could occur. When the Nd–Sr values are compared to magmatic and young volcanics, the Pohrenk fluorites are seen to be enriched and exhibit similar isotopic signatures to Upper Cretaceous aged magmatics, Early-Middle Miocene volcanics and Mio-Quaternary volcanics.     

Performance of structures in the rural area during the March 8, 2010 Elazığ-Kovancılar earthquake

Numerous studies demonstrated the possibility of utilizing fly ash in the construction of embankments, road subgrades and stabilization of a wide range of soils. The present investigation aims at determining the optimum fly ash (OFA) for mechanical stabilization of expansive soils. Four different soils were tested for compaction characteristics and unconfined compressive strength with and without the addition of fly ash to determine the OFA. The liquid limit (LL) and the fraction coarser than 425 μ (CF) of these soils range from 50 to 120 and 25 to 70%, respectively. An experimental strategy called two-factor factorial design was adopted in the conducting experiments. LL and CF present in the soil are the two factors considered to influence the OFA content. Factorial experimentation enables relative quantification of the effect of each factor as well as their interaction with the OFA. The OFA was found to range from 5 to 40% depending upon the two factors. The LL and the CF were found to have dominating influence on OFA content in that order, whereas the interaction effect of these two factors was marginal to fair. A statistical regression model was developed for determination of the OFA in terms of the influencing factors. The validity of the model developed was verified by conducting laboratory tests on two more soils that were not used in the development of the model. Swell potential and swelling pressure of expansive soils were reduced to non-critical levels when treated with OFA.     

Assessment of water quality and pollution of the Lake Seyfe basin, Kırşehir, Turkey

Lake Seyfe is located in a closed basin near K?r?ehir in the central Anatolian region, Turkey. The aim of this study is to evaluate the groundwater quality and effects of lithogenic contamination carried out in the Lake Seyfe basin, which is represented by various lithologies and groundwater types. Seyfe, Horla and Akp?nar springs are recharged through marbles at the western and southwestern of the basin are ultimately and discharged into the K?z?l?rmak Formation and Lake Seyfe. The waters of deep wells drilled into the marbles are of bicarbonate type (type I) in the Ca²⁺–Mg²⁺–HCO₃ ^? and Ca²⁺–HCO₃ ^? facies. Özlühüyük spring and waters from most of trenches and shallow wells, which are fed by the K?z?l?rmak Formation, have a mixed (type II) composition in the Ca²⁺–Mg²⁺–HCO₃ ^?–Cl^? facies. Groundwater in the alluvium and K?z?l?rmak Formation along Lake Seyfe has a salty (type III) character in the Na⁺–Cl^? facies. The main reasons of formation and change of the groundwater salinity and hydrochemical facies in the Seyfe basin are causing the various (a) lithogenic pollution and heterogeneity of the K?z?l?rmak Formation, (b) salinity of the upper soil zones, and (c) evaporation of the trench and channel waters open to the atmosphere. Considering parameters such as sodium hazard, specific conductivity, bicarbonate and carbonate hazards, waters in the study area are generally suitable for agricultural usage.     

Planktonic foraminiferal biostratigraphy of the Coniacian-Maastrichtian sequences of the Bey Dağları Autochthon,western Taurides,Turkey: thin-section zonation

Planktonic foraminifer distributions in seventeen stratigraphic sections of Upper Cretaceous hemipelagic and pelagic sequences of northern Bey Da?lar? Autochthon (western Taurides) yield six biozones such as, Dicarinella concavata Interval Zone, Dicarinella asymetrica Range Zone, Radotruncana calcarata Range Zone, Globotruncana falsostuarti Partial Range Zone, Gansserina gansseri Interval Zone, and Abathomphalus mayaroensis Concurrent Range Zone. Two of the zones, Dicarinella concavata Zone and Dicarinella asymetrica Zone, are identified in the massive hemipelagic limestones of the Bey Da?lar? Formation, of Coniacian-Santonian age. They are characterized by scarce planktonic foraminifera and abundant calcisphaerulids. The other four biozones are determined from the cherty pelagic limestones of the Akda? Formation and indicate a late Campanian-late Maastrichtian time interval. The planktonic foraminifera observed in these four biozones are diverse, complex morphotypes (K-selection), suggesting open oceans. The assemblage of the Abathomphalus mayaroensis Zone shows that the latest Maastrichtian record is absent throughout the northern part of the autochthon. Two main sedimentary hiatuses are recognized within the Upper Cretaceous pelagic sequence. Early to middle Campanian and latest Maastrichtian-middle Paleocene planktonic foraminifera are absent in all measured stratigraphic sections. Hiatus durations differ between sections as a result of diachronism of onset of the hemipelagic and pelagic deposition and the post-Santonian and post-Maastrichtian erosional phases. Drowning event and the early-middle Campanian and latest Maastrichtian-middle Paleocene hiatuses in the pelagic sequence are attributed to regional tectonics during the Late Cretaceous.     

Natural and induced sinkholes of the Obruk Plateau and Karapınar-Hotamış Plain,Turkey

The number of sinkholes (locally known as obruks) has increased rapidly in recent years near Karap?nar, located in the semi-arid Konya Closed Basin in Central Anatolia. Nineteen sinkholes have formed in the last 33 years (1977–2009) as a result of the collapse of cavity roofs in the Neogene lacustrine limestone in the Obruk Plateau and beneath Quaternary lake sediments in the Karap?nar-Hotam?? Plain. Of these, 13 have formed within the past 4 years (2006–2009). The Obruk Plateau takes its name from the presence of several hundred paleo-sinkholes which formed as a result of natural processes during the Quaternary period. More recently, human activity has induced the formation of new sinkholes, which presents a hazard to life and property. Changing agricultural patterns have led to the opening of thousands of deep wells in recent years, and increased water pumping currently exceeds the sustainable yield of the aquifer. Thus the formation of sinkholes has been triggered by a combination of natural and human causes. The groundwater level has dropped almost 24 m in the vicinity of Karap?nar during the last 26 years (1983–2008). Approximately 8 m of this drop occurred within the 4 years prior to the study (2005–2008). Legally-binding precautions must be taken to prevent further water table decline, in order to decrease sinkhole formation within the basin in the years to come.     

Palaeoseismology of the Havran-Balıkesir Fault Zone: evidence for past earthquakes in the strike-slip-dominated contractional deformation along the southern branches of the North Anatolian fault in northwest Turkey

The Havran-Bal?kesir Fault Zone (HBFZ) is one of the major active structures of the Southern Marmara Region, which has been shaped by the southern branch of North Anatolian fault since the Pliocene. HBFZ is a 10–12 km wide, 120 km long, right-lateral strike-slip fault zone that consists of two ENE-striking main faults, namely, the Havran-Balya and Bal?kesir faults. The 90-km-long Havran-Balya fault exhibits right-stepping en echelon geometry and is made up of (1) Havran, (2) Osmanlar, (3) Turplu and (4) Ovac?k fault segments. On the eastern part, the 70-km-long Bal?kesir fault is divided into two fault segments; (1) Gökçeyaz? and (2) Kepsut. We estimated the long-term slip rate between 3.59 and 3.78 mm/yr using river offset. The Kepsut, Gökçeyaz? and Ovac?k fault segments are capable of generating an earthquake with a moment magnitude of up to 7.2. Detailed palaeoseismological studies show that the HBFZ is responsible for some surface faulting earthquakes with an average recurrence interval of 1000–2000 years during the late Holocene. Considering the fact that there was no evidence of a surface-ruptured earthquake for 2000 years, it can be stated that there is a seismic gap on the Gökçeyaz? fault segment.     

Geochemical constraints on the genesis of the Sarıcakaya intrusive rocks,Turkey: Late Paleozoic crustal melting in the central Sakarya Zone

The Sakarya Zone is intruded by several Late Paleozoic granitoids, of which the Sar?cakaya intrusive rocks in the central Sakarya (Eski?ehir) region, is the least-studied. The Sar?cakaya intrusive rocks consist mainly of quartz diorite-granodiorite, granodiorite and granite. They are, geochemically, divided into two groups: diorites and granites. The former is medium-K and calc-alkaline (mainly I-type), whereas the latter is high-K to shoshonite and calcic (I-type). Typical minerals for both rock types are plagioclase, K-feldspar, quartz, biotite, hornblende and Fe–Ti oxides. Chondrite-normalized REE patterns for the Sar?cakaya intrusive rocks are moderately fractionated and have small negative Eu anomalies. They are enriched in LILE and LREE relative to HFSE showing characteristics of arc-related granitoids. Geochemical characteristics of the Sar?cakaya intrusive rocks indicate a hybrid origin through partial melting of lower crustal source rocks.     

Hydrochemistry and environmental isotope study of the geothermal water around Beypazarı granitoids,Ankara, Turkey

Hydrochemical analysis results suggest four different water types: bicarbonate dominant water (facies-I), sulfate dominant cold brine water (facies-II), sodium-bicarbonate dominant thermal water and thermal and mineralized water (facies-III), and sulfate–chloride dominant thermal and mineralized water (facies-IV). The mineral content/salinity of the water is related to the ions that these waters dissolve from the minerals on the rocks during infiltration and circulation in the saturated zone. Gypsum cover units that exist on the granitoids in the region is the main factor for the ion increase in the facies III geothermal water similar to the cold brine water (facies II). Isotopic analyses indicate that the thermal springs (Dutlu bath spring, Aya? bath well, Çoban bath well and Kapullu bath spring) are of meteoric origin and receive recharge from precipitation in the Beypazar? granitoids and around gypseous formations with elevations of about 950–1,150 m. Karakaya bath well and Il?ca bath spring thermal water points are recharged from the Bilecik limestone hills, Tekke volcanics and ?ncedoruk Formations. Karakoca mineral spring of thermal and mineralized water is recharged from out of the study area. According to oxygen-18 (SO₄^2?) and sulfur-34 (SO₄^2?) contents, sulfate in water samples from Aya? and Dutlu resorts as well as Çoban bath is derived from the gypsum of Kirmir Formation as the primary source. Sulfates of the Kapullu bath water and Karakoca mineral water originate from secondary sources such as pyrite oxidation and bacteriological reduction.     

Geochemical, mineralogical and isotopic signatures of the Semikan, West Kasrık “Turkish” phosphorites from the Derik–Mazıdağı–Mardin area, SE Anatolia

The geochemistry and mineralogy of a condensed section, ~6 m thick of the West Kasrik member (Coniacian–Santonian) near the uplifted northern flank of the Mardin–Derik anticline (south-eastern Turkey) was studied. The only deposit exploited in Turkey is found in this area. The sediment textures as well as the mineralogical and the geochemical results collectively suggest that these recycled phosphorites accumulated in areas of intensive very early diagenesis of the sediments in highly oxic bottom waters, and almost no detrital apport. The total concentration of redox-sensitive trace metals is very low (<600 μg/g); in addition the structural CO₂ and F/P₂O₅ are unusually high (~5 wt % and 0.14, respectively). REE distribution shows a clear “seawater” pattern with a strongly negative Ce-anomaly (0.20 ± 0.02) and heavy REE enrichment (Lu_N/La_N = 1.50 ± 0.12), however their total concentration is very low. The low REE contents, quite unexpected in recycled phosphorites, are explained by the scarcity of terrigenous components which leads to minimal incorporation of REEs from detrital clastic phases in the CFA fraction. Weathering previously suggested as responsible for the high P enrichment of the Mazidagi phosphorites is rather improbable in the samples we studied, in view of their high structural CO₂, high F/P₂O₅, high (La/Nd)_N and (La/Sm)_N ratios, and high Sr/P and Ca/P of separated CFA fractions that all negate post-depositional weathering. More likely, the high P enrichment of some rocks (P₂O₅ content reaches 34%) was produced by sedimentary and early diagenetic processes acting in oxygenated areas of starved sedimentation on and around tectonic highs.     

Geochemical characteristics of Kırka (Sarıkaya) borate deposit,northwestern Anatolia,Turkey

The K?rka borate deposit was deposited in a Miocene lacustrine basin which is closely associated with volcanic activity which lasted from Paleogene to the beginning of Quaternary. Borate mineralization alternates with claystone, mudstone, tuff and fine-layered limestone and mostly shows a lenticular structure. The mineral paragenesis is composed of borax, tincalconite, ulexite, kurnakovite, probertite, tunellite, colemanite, dolomite, smectite group minerals, illite and some firstly reported minerals for the K?rka deposit including hydrochloroborite, brianroulstonite, hilgardite-4M and searlesite minerals. In comparison to average values of earth crust, concentrations of Cs, Sr, Li, As and Se were significantly enriched with respective rates of 21, 15, 14, 3 and 188 folds. Regarding KY, KS1 and KS2 locations, there are differences in both element abundances and their geochemical tendencies which are attributed to variations in discharge regime and physico-chemical conditions of the depositional environment. Independent behaviour of B₂O₃ might indicate that boron is not associated with clays and carbonates and, therefore, most part of boron must be derived from volcanic activity (hydrothermal solutions, gases). REE data indicate that the K?rka borate deposit was formed in a sedimentary environment where highly alkaline (high pH) hydrothermal solutions also took part in borate precipitation process.     

The rodent fauna from the Adapazarı pull-apart basin (NW Anatolia): its bearings on the age of the North Anatolian fault

To the east of the Sea of Marmara, the North Anatolian fault (NAF) branches into two strands, namely the northern and the southern strands. The Adapazarı pull-apart basin is located in the overlapping zone of the Dokurcun and the İzmit–Adapazarı segments of the northern strand. The combined temporal ranges of the arvicolids from the Karapürçek formation (the first unit of the basin fill), deposited in the primary morphology of the Adapazarı pull-apart basin, cover the latest Villanyian (latest Pliocene) and the Biharian (Early Pleistocene) time interval. The Değirmendere fauna collected from the lowermost sediments of this formation suggests that the Adapazarı pull-apart basin started to form in the latest Pliocene. This, in turn, suggests that the dextral movement along the northern strand of the NAF commenced during the latest Pliocene. A new species, Tibericola sakaryaensis is also described.     

Geothermometry applications for the Balıkesir thermal waters,Turkey

In this study, reservoir temperatures of Balıkesir geothermal waters in northwestern Turkey are estimated with various geochemical models. The geothermal fluids in the region are represented by Na–SO₄, Na–HCO₃ and Ca–HCO₃ type waters with discharge temperatures up to 98°C. It was determined that the solubility of silica in most of the waters is controlled by the chalcedony phase. Equilibrium states of the Balıkesir thermal waters studied by means of Na–K–Mg–Ca diagram, mineral saturation calculations and activity diagrams in the system composed of Na₂O–CaO–K₂O–Al₂O₃–SiO₂–H₂O phases approximate a reservoir temperature of about 120°C. Most of the waters are found to be equilibrated with calcite, chalcedony ± quartz and muscovite at predicted temperature ranges, similar to those calculated from the chemical geothermometers.