Dynamic Analysis of Deformational Structures of the Xiannüshan Fault Zone in the Three Gorges of the Yangtze River

Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannüshan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of (1 is N-S in direction with differential stresses of 150(250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.     

Dynamic Analysis of Deformational Structures of the Xiannüshan Fault Zone in the Three Gorges of the Yangtze River

Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannüshan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of (1 is N-S in direction with differential stresses of 150(250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.     

Investigation of the quality and physical-geochemical characteristics of the drinking water in Gümüşhane (Turkey) city central

The physical (turbidity, color, smell, taste, pH, and conductivity) and geochemical properties (Ca, Mg, Na, Fe, Mn, Al, K, Cl^?, HCO₃ ^?, SO₄ ^2?, Fe, Cu, Co, Ni, Zn, Cd, Pb, and Cr) of the drinking water in Gümü?hane city center were determined. This city center constitutes the study area. The pH levels of the water samples ranged from 6.3 to 8.2, and their conductivities ranged between 240 and 900 μS. These findings were concordant with the drinking water standards of the Turkey Standard Institute and the World Health Organization. The hardness of the water samples in the study area was between 18.1 and 115.1 °Fr. These samples were classified as extremely hard, hard, and quite hard. In addition, an assessment using the criteria for Inland Surface Water Classification indicated that considering certain parameters (pH levels, amount of Na, SO₄ ^2?, Fe, Mn, Al, Co, Ni, Cu, and Cr), the samples belonged to class I (high quality) water. When Cl^? amount and conductivity were considered, the samples belonged to the first and second classes (less polluted) of water. The water in the study area was generally classified as carbonated and sulfated (Ca + Mg > Na + K) water classes. This water contained more weak acids than strong acids (HCO₃ ^? + CO₃ ^2? > Cl^? + SO₄ ^2?). The pH levels (6.3–8.2) of the water in the study area were unrelated to the varying concentrations of metals in the water. Elements such as Fe, Ni, Cd, Pb, Zn, and Cu increase in the water through the water–rock interaction in the area in which water rises or through the mixture of water with either mine or industrial wastes. In addition, several water samples belonged to an acceptable water class for drinking and usage.     

Ground-penetrating radar for monitoring the distribution of near-surface soil water content in the Gurbantünggüt Desert

In the Gurbantünggüt Desert, snowmelt-induced high soil water contents briefly create favorable conditions for the germination and growth of plants every spring. Monitoring the rapidly changing conditions in this time period demands fast and efficient methods for measuring soil water contents at the field scale. For this study, a series of ground-penetrating radar (GPR) measurements were carried out on sites characterized by semi-vegetated dunes both in April 2010 and 2011. We compare water contents calculated from the GPR direct ground wave signal to both point scale validation measurements by time-domain reflectometry (TDR) and gravimetric sampling. Our results show that GPR is an effective method to rapidly obtain a detailed image of the field scale soil water content distribution in the Gurbantünggüt Desert with an accuracy similar to TDR. Observed large scale soil water content variations are dominated by dune topography: During snow melting, melt water was found to trickle slowly from the dune ridges to interdune valleys, increasing the soil water content there while the dune ridges quickly started to dry down. In dune valleys, smaller scale near-surface soil water content changes were dominated by variations in the vegetation coverage, leading to snowmelt funnels at distinct locations: The snowmelt initially occurred around the stems and branches of plants, forming funnel-shaped melt water induced holes through the snow cover and leading to an increasing amount of melt water collected around these plant roots. Our comparison of data from 2010 to 2011 furthermore suggests a temporally stable distribution of near-surface soil water content. This has important ecological significance for controlling desertification and for restoring and reconstructing vegetation in the Gurbantünggüt Desert.     

Tertiary Volcanic and Tectonic Evolution of the Ayas-Güdül-Celtikci Region,Turkey

Volcanic activity in the Ayas-Güdül-Celtikci region began by Oligocene (?)-early Miocene time and persisted until the end of early Pliocene time. It commenced with andesitic breccias and lavas at the base of the series and evolved through the deposition of ignimbritic and laharic volcanic material toward intermediate levels of the succession. Caldera formation followed this period of volcanic activity. Ephemeral lakes covering the region caused the subaqueous extrusion of the latest lavas during this period of activity. Afterward, limnic and fluvial sedimentation Occurred in the region during a period of volcanic quiescence. This mid-late Miocene deposition was followed by new basaltic activity. The volcanism was controlled by conjugate fault sets, N45W and N15E, representing pure-shear stress in a N20W direction, from the late Oligocene to the end of the early Pliocene. Normal dip-slip faults having a N55E trend were created by local N25W tension, presumably because of the North Anatolian fault, after early Pliocene time.     

Plio-Quaternary evolution of the Küçük Menderes Graben Southwestern Anatolia,Turkey

The Küçük Menderes Graben (KMG) is part of the horst-graben system of southwestern Anatolia (Turkey), bounded by the Bozda? horst in the north and the Ayd?n horst in the south. The Plio-Quaternary evolution of the KMG has been evaluated using the nature of the Miocene-Quaternary fill sediments and palaeostress analysis of slip data measured in different parts of the graben.

The graben is composed of five subbasins—the Kiraz, Ödemi?, Bay?nd?r, Da?k?z?lca-Torbal? and Selçuk—that are connected to each other through narrow Quaternary troughs. The Da?k?z?lca, Kiraz and Selçuk basins bear Miocene and younger sequences whereas the other subbasins are largely filled by Quaternary sediments. The maximum thickness of the Quaternary fill reaches about 270 m in the Ödemi? and Bay?nd?r subbasins.

The calculated slip results indicate multidirectional extension, three successive deformational periods, and possible counterclockwise rotation in the KMG during the post-Miocene period. The first phase was a strike-slip regime under N-S compression, followed by a second phase of deformation which resulted in ENE-WSW extension with strike-slip components. The final phase of deformation was NE-SW extension which constituted the final evolution of the KMG.

The graben gained its present morphological configuration via the onset of E-W-trending, high-angle normal faulting imposed on the regionwide synformal structure during the Plio-Quaternary. The KMG evolved as a result of rifting during the Plio-Quaternary which followed Late Miocene unroofing of the Menderes Massif and the evolution of the Büyük Menderes and Gediz grabens.     

Lithostratigraphy,facies, and deposition environment of the lower Jurassic Ammonitico Rosso type sediments (ARTS) in the Gümüşhane area,NE Turkey: Implications for the opening of the northern branch of the Neo-Tethys Ocean

Ammonitico Rosso type sediments (ARTS) form the bottom level of the ?enköy Formation in the Gümü?hane area. The formation accumulated in the rift-related basins triggered by extensional tectonic regimes in the Early Jurassic times. Six different sections were studied in this area in order to interpret the lithostratigraphy, facies, and deposition environments of the ARTS. Two basic lithofacies were distinguished, nodular-marly and nodular-calcareous. These facies provide useful information regarding depositional conditions in the area and environmental energy. These factors were mainly related to the relative sea-level that in turn was controlled by tectonic and eustasy conditions. In addition, seven different types of microfacies were recognized and described as a result of the detailed analysis of the sections. The results of the analysis show that these sediments in the Gümü?hane area were developed in transgressive phases/events. These sediments share characteristics with other peri-Mediterranean regions and sea-level curves, and show a similarity to the major transgressive pulse during the Pliensbachian stage. Deposition of ARTS was controlled by syn-depositional extensional movements, leading to their accumulation on top of tilted blocks, slopes and horsts in an open marine environment. The ARTS were developed during the rifting of the continental margins pointing up the phases of the Tethys opening. Neptunian dykes verifying this opening developed at different levels of the ARTS and were filled with overlying sediments. These results support the hypothesis that the ARTS were formed in tectonically active environments where extensional tectonic movements were continuously improved during the deposition of the ARTS.     

Timing of low-temperature metamorphism and cooling of the Paleozoic and Mesozoic formations of the Bükkium,innermost Western Carpathians,Hungary

K-Ar ages of illite-muscovite and fission track ages of zircon and apatite were determined from various lithotypes of the Bükkium, which forms the innermost segment of the Western Carpathians. The stratigraphic ages of these Dinaric type formations cover a wide range from the Late Ordovician up to the Late Jurassic. The grade of the orogenic dynamo-thermal metamorphism varies from the late diagenetic zone through the anchizone up to the epizone (chlorite, maximally biotite isograd of the greenschist facies). The K-Ar system of the illite-muscovite in the < 2 m grain-size fraction approached equilibrium only in epizonal and high-temperature anchizonal conditions. The orogenic metamorphism culminated between the eo-Hellenic (160-120 Ma) phase connected to the beginning of the subduction in the Dinarides, and the Austrian (100-95 Ma) phase characterized by compressional crustal thickening. No isotope geochronological evidence was found for proving any Hercynian recrystallization. The stability field of fission tracks in zircon was approached using the thermal histories of the different tectonic units. A temperature less than 250°C and effective heating time of 20–30 Ma had only negligible effects on the tracks, whereas total annealing was reached between 250 and 300°C. Apatite fission track ages from the Paleozoic and Mesozoic formations show that the uplift of the Bükk Mountains occurred only in the Tertiary (not earlier than ca. 40 Ma ago). Thermal modeling based on apatite fission track length spectra and preserved Paleogene sediment thickness data proved that the Late Neogene burial of the recently exhumed plateau of the Bükk Mountains exceeded 1 km.     

Mineral chemical investigation on sulfide mineralization of the Istala deposit,Gümüşhane,NE-Turkey

The mineralogy of the Istala deposit, Gümüşhane, northeastern Turkey, was studied in detail, and a geochemical investigation was carried out using electron probe micro-analysis (EPMA). Sphalerite, galena, chalcopyrite and pyrite are the major sulfide minerals found in the Istala deposit, with minor amounts of bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite. In addition to these, barite and a small quantity of quartz occur as gangue minerals. Based on the textural relations and mineral assemblages, five different stages of crystallization have been recognized. Mineral paragenesis of the first four stages has been found to be similar, whereas clear enrichment has been observed in the modal abundance of the copper sulfide mineral assemblage at the fifth-stage ore formation. Whole-rock geochemical analyses of the Istala ore show an enrichment of Ag content up to 3328 ppm. Optical observations and EPMA study indicated that abundant silver mineralization was found in the Istala ore, especially during the later-stage ore deposition. Repetition to the presence of native silver in the samples, a significant amount of silver was incorporated in bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite, whereas a trace amount of silver has been detected in sphalerite, galena, chalcopyrite and pyrite. The homogenization temperatures (T_h) of the primary fluid inclusions were measured between 98 and 284 °C, with frequency peaks around 140 °C, 190 °C and 240 °C. All data obtained support the theory that later stage copper-rich sulfides, formed under the low temperature conditions, are responsible for the large amounts of silver content in the Istala mine.     

Late Quaternary evolution of the Gediz and Büyük Menderes grabens,Western Anatolia,Turkey

The Gediz and the Büyük Menderes Graben basins, two of the most important structural elements of western Anatolia, markedly differ in their palaeogeographic evolution during the Holocene. On the basis of the study of the facies and the geomorphological characteristics of the youngest sedimentary fills it is suggested that the evolution of the Büyük Menderes basin has a simple progradational history while the Gediz River basin has shown a complex evolution mainly controlled by intense tectonic periods. Comparison between the palaeogeographic evolution of these basins points to the fact that tectonism has been more effective in the Gediz basin during the Holocene.     

Pyritized mudstone and associated facies in the Permian–Triassic boundary of the Çürük Dağ section,Southern Turkey

This paper is the first study of pyritized mudstones (PM) in the Permian–Triassic (P–T) boundary section of the Çürük Da? (Taurus, Antalya Nappes, Turkey). The mudstones were generally formed as lensoidal-shaped layers or infill materials within nodular platform limestones (hardground). Normal marine fauna is diminished in the pyritized limestones, whereas tube-like microorganisms are apparently increased with the association of pyrite crystals consisting of both framboidal and cubic crystals. The total rock volumes are up to 50–60% clay minerals and are mainly made up of in situ kaolinite and subordinate mixed layer clays (illite–vermiculite). Kaolinite preferentially developed on feldspar crystals, sometimes covering ostracoda bivalves together with gypsum micronodules composed of fan-shaped gypsum crystals. The origin of the kaolinite is, in situ, directly related to feldspar dissolution via heterotrophic bacteria. Thus, kaolinite is found along with bacterial structures. Other mineralogical compositions include established quartz (mostly β-quartz), gypsum crystals (100–200 μm) glauconite and magnetite. Magnetite grains comprise a minor amount (1–2%) and show some bacterial-induced crystal orientations. Glauconite is formed as an accessory mineral that occurs as infill material in biogenic grains. On the other hand, some microspheres represented by a silica-dominated composition are only observed in scanning electron microscopes (SEM) studies under high magnification. Isotope values (d34S) obtained from the pyritized mudstones show an isotopic heterogeneity that suggests that the pyritized mudstone consists of at least two components, with different sulphur-concentrations and d34S values.     

Lake Müggelsee —the use of lake water and its consequences

Lake Müggelsee (Groer Müggelsee) — the largest lake in the area of Berlin — is the main drinking water reservoir for Berlin (East), but also a center of numerous recreational activities and fishing. The use of the lake and its catchment area has continuously increase during the past decase and has caused a substantail deterioration of the lake water quality. Mass development of algae has become a limiting factor to all future utilizations of the lake. Since the beginning of this century up to the seventies the lake water has shown signs of a permanently growing eutrophication, e.g. the content of particulate matter in the lake water has nearly doubled. During and after World War II the lake quality (Secchi depth and seston content) improved remarkably due to a reduced input of nutrients.According to time series analyses of buoyant seston and meterologica elements the development of blue-green algae seems to depend more on weather conditions than on the nutrient content of the lake water.Therefore, a certain probability of blue-green algae blooms will remain, also in the case of reduced nutrient input. Phosphorous is the main cause for eutrophication. It was responsible for distinctly higher mass developments of algae during spring and autumn in the past two decades. As a consequence, comprehensive measures are to be taken to reduce phosphorus inputs into the Spree river and lake Müggelsee, e.g. by the substitution of P in detergents, construction of tertiary sewage treatment plants and a substantially reduced application of fertilizers in agriculture.     

Geochemical and Petrological Characteristics of the Kale (Gümüshane) Volcanic Rocks: Implications for the Eocene Evolution of Eastern Pontide Arc Volcanism,Northeast Turkey

The Kale (Gumushane) volcanic rocks crop out in the southern zone of the eastern Pontide arc, and consist mainly of agglomerate, andesite, minor basalt, and tuff associated with sediments (limestone, marl, siltstone, sandstone) deposited in a shallow basin environment. The volcanites show mainly porphyritic, hyalo-porphyritic, and rare fluidal and glomeroporphyritic textures. These volcanic rocks consist predominantly of plagioclase, augite, hornblende, and lesser biotite, magnetite, and quartz, and secondary products of chloritization, carbonation, sericitization, and epidotization. In general, they show disequilibrium textures, possibly reflecting magma-mixing processes.

The volcanic rocks are mainly calc-alkaline in composition, and show moderate potassium enrichment. Most of the major- and trace-element variations reflect the significant role of fractional crystallization during the evolution of the volcanic suite. The fractionating phases are dominantly hornblende and augite, minor plagioclase, and magnetite. The rocks have high LILE and LREE enrichments, but are relatively depleted in HFSE relative to MORB. Moreover, incompatible trace-element distributions show similarities to those of an E-type MORB source. The rocks have moderately fractionated REE patterns with (La/Lu)_N = 2–12. Geochemical data suggest that the volcanites evolved by shallow-level fractional crystallization and magma-mixing contamination of a parental magma derived from metasomatized upper mantle by partial melting after thickening of the Pontide arc during the Paleocene-Eocene. Furthermore, differentiation took place in a magma chamber situated in the thickened arc crust within an extensional tectonic regime.     

Effect of Construction Material on Dam Type Selection of the Büyük Karaçay Dam (Hatay, Turkey)

This paper covers the investigation of construction materials and selection of the dam type for the Büyük Karaçay Dam, which was planned to be constructed on Büyük Karaçay River 20 km to the SW of Hatay (Southern Turkey). The purposes of the dam are irrigation, domestic water supply, and producing energy. Auxiliary structures locations have been determined during the study of detailed geological maps of the dam axis and reservoir area. Quality, quantity and hauling distance of natural construction materials were effective to select different dam types. For engineering geological studies exploration boreholes were drilled at the dam site; pressuremeter tests were performed in order to determine bearing capacity and elasticity properties of rocks; pressured water tests were also performed to determine permeability of the dam site. Moreover, physical and mechanical properties of rocks were determined by the laboratory test. In the feasibility stage, the dam type was chosen as the central core rock-fill dam, depending on state of natural construction materials. In design stage dam type was changed as faced symmetrical hardfill dam. Finally, the dam type was revised again during the design stage as concrete face rockfill dam.     

Organic geochemistry and depositional environment of the Aptian bituminous limestone in the Kale Gümüşhane area (NE-Turkey): An example of lacustrine deposits on the platform carbonate sequence

The Jurassic–Lower Cretaceous aged carbonate sequence is widely exposed in the southern zone of Eastern Pontides. Aptian black bituminous limestone is found in the upper part of this sequence in the Kale area (Gümüşhane). This limestone contains faunal remains (e.g., gastropod, ostracod, characean stems and miliolid type benthic foraminifera) that indicate a freshwater, lacustrine depositional environment.The total organic carbon (TOC) values of the bituminous limestone samples range from 0.11–1.30% with an average TOC value of 0.54%. The hydrogen index (HI) varies from 119–448 mg HC/g TOC (average HI 298 mg HC/g TOC) indicating that the limestone contains gas prone as well as oil prone organic matter. Pyrolysis data prove that the organic matter content in the bituminous limestone consists of Type II kerogen. The average T_max value for bituminous limestone samples is 438 °C (434–448 °C). Bitumen/TOC ratios for bituminous limestone are 0.05 and 0.04. The T_max values and the ratios indicate that the bituminous limestone samples contain early mature to mature organic matter.Analysis of solvent extracts from the two richest bituminous limestones show a predominance of high carbon number (C₂₆–C₃₀) n-alkanes. The Pr/Ph ratio and CPI value are 1.34 and 0.96, respectively. C₂₉ is the dominant sterane, with C₂₉ > C₂₇ > C₂₈. The bituminous limestone samples have low C₂₂/C₂₁ ratios, high C₂₄/C₂₃ tricyclic terpane ratios and very low C₃₁R/C₃₀ hopane ratios (<0.25). These data are consistent with the bituminous limestones being deposited in a lacustrine environment.     

Natural and artificial radioactivity levels and hazards of soils in the Kücük Menderes Basin,Turkey

In this study, natural and artificial radionuclide activity concentrations in surface soils of Kücük Menderes Basin have been measured using gamma spectroscopy. The soil samples were collected from agricultural lands in the Kücük Menderes Basin in Turkey. The activity concentrations of ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs in the soils were found to be range of 12.63 ± 2.28–72.51 ± 11.23, 11.45 ± 2.4–58.12 ± 4.76, 234.8 ± 14.85–1058.52 ± 24 Bq kg^?1 dw and 2.31 ± 0.18–7.75 ± 1.14 Bq kg^?1, respectively. The natural gamma radioactivity of the terrestrial radionuclides in soil samples and the gamma absorbed dose rate, the annual effective dose equivalent, the radium equivalent activity, the external hazard index, were calculated and compared with the international recommended values.     

A new pair of coexisting amphiboles : the grünerite and ferropargasite pair

A new coexisting amphibole pair was recently found in the Jianshan iron deposit, Loufan of Shanxi Province, China. Electron microprobe analysis shows that the coexisting pair is composed of grünerite K_0.001 (Na_0.027 Ca_0.073 Mn_0.031 Fe _1.801 ²⁺ )_1.932 (Fe _2.948 ²⁺ Mg_1.964 Ti_0.002 Al_0.087)₅Si_8.069 O_22.10(OH)₂ and ferropargasite (K_0.135 Na_0.461)_0.596 (Na_0.088 Ca_1.853 Mn_0.005 Fe _0.072 ²⁺ )₂(Mn_0.005Fe _2.789 ²⁺ Mg_0.875Ti_0.021Fe _0.499 ³⁺ Al_0.812)₅(Si_6.103Al_1.897)₈O_22.00(OH)₂. The two kinds of amphiboles occur in amphibole schist not only as separate phenocrysts, but also are combined to form “single-crystal” phenocrysts in the form of topotactic intergrowths with the common c- and b-axes. The boundary between topotactic grünerite and ferropargasite is optically and chemically sharp. In comparison with the coexisting ferromagnesian amphibole and calcic amphibole pair discovered by predecessors, the newly discovered pair has lower Mg/Fe ratios and wider miscibility gaps.     

Heterogeneous response of hydrogeological systems to the Izmit and Düzce (Turkey) earthquakes of 1999

At four sites in Turkey and Armenia the physico-chemical properties of thermal and mineral waters were monitored continuously during the Izmit and Düzce earthquakes that occurred along the North Anatolian fault in August and November 1999. The epicentral distances between the moment magnitude (M_w) 7.6 Izmit earthquake and the monitoring locations were 313, 488, 1,161, and 1,395 km. At the most distant site, the specific electrical conductivity of mineral water from a flowing artesian well dropped co-seismically and postseismically by 7%. No changes were observed at the other sites, although the estimated earthquake strains and peak ground accelerations are much higher. A similar pattern was observed after the Düzce earthquake, which happened three months after the Izmit event. The response of a hydrogeological system seems to depend on the site characteristics rather than on the nature of the earthquake. A hydrogeological model for the sensitive observation site farthest from the Izmit earthquake explains the observations in terms of a changed mixing ratio between two fluid components. Passing seismic waves may trigger a local pore-pressure increase according to the mechanism of advective overpressure. The preconditions for this mechanism, free gas bubbles in the aquifer in combination with a trap for rising bubbles, is probably not fulfilled by the other groundwater systems. Electronic Publication     

Reciprocal influence of Kürtün Dam and wastewaters from the settlements on water quality in the stream Harşit,NE Turkey

This paper aims to reveal the reciprocal influence of Kürtün Dam and wastewaters from the settlements on the water quality in the stream Har?it, NE Turkey. Several key water-quality indicators were measured: water temperature (T), pH, dissolved oxygen (DO), electrical conductivity, water hardness, chemical oxygen demand (COD), ammonium nitrogen (NH₄ ⁺–N), nitrite nitrogen (NO₂ ^?–N), nitrate nitrogen (NO₃ ^?–N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), orthophosphate phosphorus (PO₄ ^3?–P), and methylene blue active substances (MBAS). The monitoring and sampling studies were conducted every 15 days from March 2009 to February 2010 at two stations selected in the upstream and downstream of the Kürtün Dam. It was concluded that the Kürtün Dam Lake had a high-quality water in terms of T, pH, DO, COD, NH₄ ⁺–N, NO₂ ^?–N and NO₃ ^?–N values, but slightly polluted water with respect to TKN, PO₄ ^3?–P, and MBAS according to the Turkish Water Pollution Control Regulation. The dam improved the stream water quality by increasing the DO concentration, and decreasing the NO₂ ^?–N and PO₄ ^3?–P concentrations thanks to its hydraulic residence time despite the wastewater discharge by the nearby settlements. However, the wastewater discharge deteriorated the stream water quality increasing the COD, NH₄ ⁺–N, NO₃ ^––N, and TN concentrations.     

Hydrogeochemistry and Water Quality Evaluation along the Flow Path in the Unconfined Aquifer of the Düzce Plain,North-western Turkey

The Düzce Plain has a multi-aquifer system, which consists of a near surface unconfined aquifer, along with first and second deeper confined aquifers. Hydrochemical evolution and water quality are related to infiltration of the precipitation, recharge from the formations surrounding the plain, flow path of groundwater and the relationship between surface and groundwater. The groundwater in the unconfined aquifer flows towards the Efteni Lake and the Büyük Melen River. Surface waters are divided into two main hydrochemical facies in the study area: (a) Ca2+–HCO3?; and (b) Ca2+, Mg2+–HCO3-, SO42-. The groundwater has generally three main hydrochemical facies: (a) Ca2+–HCO3-; (b) Ca2+, Mg2+–HCO3-; and (c) Ca2+, Mg2+–HCO3-, Cl-. The hydrochemical facies "a" and "b" dominate within shallow depths in recharge areas under rapid flow conditions, while hydrochemical facies "c" characterizes shallow and mixed groundwater, which dominate intermediate or discharge areas (near Efteni Lake and Büyük Melen River) during low flow conditions and agricultural contamination. Calcium and bicarbonate ions, total hardness and electrical conductivity of total dissolved solids (EC–TDS) values increase along the groundwater flow path; but these parameters remain within the limits specified by the standards set for industrial and agricultural usages.