A framework for ecosystem impacts assessment using an indicator approach   总被引：2，自引：1，他引：2  

Livingston  P.A.; Aydin  K.; Boldt  J.; Ianelli  J.; Jurado-Molina  J. 《ICES Journal of Marine Science》2005,62(3):592-597

  相似文献   

Geochemical and Sr–Nd–Pb isotopic compositions of the Eocene Dölek and Sariçiçek Plutons, Eastern Turkey: Implications for magma interaction in the genesis of high-K calc-alkaline granitoids in a post-collision extensional setting     

Orhan Karsli  Bin Chen  Faruk Aydin  Cüneyt en 《Lithos》2007,98(1-4):67-96

The major and trace elements and Sr–Nd–Pb isotopes of the host rocks and the mafic microgranular enclaves (MME) gathered from the Dölek and Sariçiçek plutons, Eastern Turkey, were studied to understand the underlying petrogenesis and geodynamic setting. The plutons were emplaced at  43 Ma at shallow depths ( 5 to 9 km) as estimated from Al-in hornblende geobarometry. The host rocks consist of a variety of rock types ranging from diorite to granite (SiO₂ = 56.98–72.67 wt.%; Mg# = 36.8–50.0) populated by MMEs of gabbroic diorite to monzodiorite in composition (SiO₂ = 53.21–60.94 wt.%; Mg# = 44.4–53.5). All the rocks show a high-K calc-alkaline differentiation trend. Chondrite-normalized REE patterns are moderately fractionated and relatively flat [(La/Yb)_N = 5.11 to 8.51]. They display small negative Eu anomalies (Eu/Eu = 0.62 to 0.88), with enrichment of LILE and depletion of HFSE. Initial Nd–Sr isotopic compositions for the host rocks are ε_Nd(43 Ma) = − 0.6 to 0.8 and mostly I_Sr = 0.70482–0.70548. The Nd model ages (T_DM) vary from 0.84 to 0.99 Ga. The Pb isotopic ratios are (²⁰⁶Pb/²⁰⁴Pb) = 18.60–18.65, (²⁰⁷Pb/²⁰⁴Pb) = 15.61–15.66 and (²⁰⁸Pb/²⁰⁴Pb) = 38.69–38.85. Compared with the host rocks, the MMEs are relatively homogeneous in isotopic composition, with I_Sr ranging from 0.70485 to 0.70517, ε_Nd(43 Ma) − 0.1 to 0.8 and with Pb isotopic ratios of (²⁰⁶Pb/²⁰⁴Pb) = 18.58–18.64, (²⁰⁷Pb/²⁰⁴Pb) = 15.60–15.66 and (²⁰⁸Pb/²⁰⁴Pb) = 38.64–38.77. The MMEs have T_DM ranging from 0.86 to 1.36 Ga. The geochemical and isotopic similarities between the MMEs and their host rocks indicate that the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust- and mantle-derived magmas. All the geochemical data, in conjunction with the geodynamic evidence, suggest that a basic magma derived from an enriched subcontinental lithospheric mantle, probably triggered by the upwelling of the asthenophere, and interacted with a crustal melt that originated from the dehydration melting of the mafic lower crust at deep crustal levels. Modeling based on the Sr–Nd isotope data indicates that  77–83% of the subcontinental lithospheric mantle involved in the genesis. Consequently, the interaction process played an important role in the genesis of the hybrid granitoid bodies, which subsequently underwent a fractional crystallization process along with minor amounts of crustal assimilation, en route to the upper crustal levels generating a wide variety of rock types ranging from diorite to granite in an extensional regime.  相似文献   

Reply to the comments by G. Bertotti and V. Picotti on: “Uplift and contractional deformation along a segmented strike-slip fault system: the Gargano Promontory, southern Italy”     

Charles M. Brankman  Atilla Aydin 《Journal of Structural Geology》2004,26(12):2327-2329

  相似文献   

Microstructural study of a natural slip zone: quantification and deformation history   总被引：4，自引：0，他引：4  

B. P. Wen  A. Aydin 《Engineering Geology》2003,68(3-4):289-317

Microstructure of a natural slip zone was comprehensively examined using a combination of images captured systematically by optical microscopy (OPM) and backscattered electron microscopy (BEM) techniques. Microstructural features identified on these images were processed and evaluated using an advanced image analysis system, which proved that quantitative analyses could considerably enhance the understanding of shear behavior of slip zones. It was found that variations of porosity, abundance of platy clay particles and alignments of particles are significant indicators revealing nature of deformation processes. These indicators show that global mechanical behavior of the investigated slip zone can be conceptualized as that of normally consolidated clayey soils under drained conditions.

The geometric patterns of the microstructure of the slip zone are similar to the S–C fabrics seen in tectonic shear zones. It is suggested that combined progressive bulk simple shear and pure shear modes enable to realistically reconstruct the kinematic history of the slip zone, through which particle movements and microstructural evolution were accomplished via various types of particulate flows. The results of this study show that clay mineralogy plays a more important role in the development of the slip zone than abundance of clay-size particles, while both clay mineralogy and relative proportions of each particle size fraction control the response of particles to shear deformation. Among the fractions present in the slip zone, fine silts are the strongest indicator of global shear stress characterized by their highest degree of alignment, whereas clay particles are the weakest. Highest degree of shape preferred orientation is also found within fine silt domains.  相似文献   

Investigating the transition between the 1967 Mudurnu Valley and 1999 Izmit earthquakes along the North Anatolian fault with static stress changes   总被引：1，自引：0，他引：1  

Jordan R. Muller  Atilla Aydin  Frantz Maerten 《Geophysical Journal International》2003,154(2):471-482

  相似文献   

Development of faults as zones of deformation bands and as slip surfaces in sandstone   总被引：10，自引：0，他引：10  

Atilla Aydin  Arvid M. Johnson 《Pure and Applied Geophysics》1978,116(4-5):931-942

Three forms of fault are recognized in Entrada and Navajo Sandstones in the San Rafael Desert, southeastern Utah; deformation bands, zones of deformation bands, and slip surfaces. Small faults occur asdeformation bands, about one millimeter thick, in which pores collapse and sand grains fracture, and along which there are shear displacements on the order of a few millimeters or centimeters. Two or more deformation bands adjacent to each other, which share the same average strike and dip, form azone of deformation bands. A zone becomes thicker by addition of new bands, side by side. Displacement across a zone is the sum of displacements on each individual band. The thickest zones are about 0.5 m and total displacement across a thick zone rarely exceeds 30 cm. Finally,slip surfaces, which are through-going surfaces of discontinuity in displacement, form at either edge of zones of highly concentrated deformation bands. In contrast with individual deformation bands and zones of deformation bands, slip surfaces accommodate large displacements, on the order of several meters in the San Rafael Desert.The sequence of development is from individual deformation bands, to zones, to slip surfaces, and each type of faulting apparently is controlled by somewhat different processes. The formation of zones apparently involves strain hardening, whereas the formation of slip surfaces probably involves strain softening of crushed sandstone.  相似文献   

Small faults formed as deformation bands in sandstone   总被引：13，自引：0，他引：13  

Atilla Aydin 《Pure and Applied Geophysics》1978,116(4-5):913-930

Small faults with displacements of a few millimeters or centimeters are abundant in the Entrada and Navajo Sandstones, in the San Rafael Desert, Utah, where they are important primary structures, preceding the development of large faults with displacements of several meters or tens of meters. The small faults contain no surfaces of discontinuity, rather they occur asdeformation bands about one millimeter and tens or hundreds of meters long, and across which the displacements are distributed. Two zones with different modes of deformation can be distinguished within a deformation band: an outer zone where the matrix, including pores and matrix material, deforms; and an inner zone, about 0.5 mm thick, where the sand grains fracture and further consolidation takes place. Fracturing of the grains is controlled by contact geometry; the grains tend to split into subgrains along lines connecting contact points between the grains. Then the angular subgrains, which are readily fractured, are further granulated and mixed with the matrix. The final product is the deformation band, with much smaller grain size, poorer sorting, and lower porosity than the original parent sandstone. The sandstone on either side of a deformation band is almost undisturbed-fractures are rare there — so that deformation is highly localized within the band. The material within a deformation band apparently strain hardens as a result of the deformation; perhaps this is why the shear displacement across a deformation band is at most a few centimeters.  相似文献   

Seismic hazard studies for Gaziantep city in South Anatolia of Turkey     

Hamza Güllü  Atilla M. Ansal  Aydin Özbay 《Natural Hazards》2008,44(1):19-50

Seismic hazard studies were conducted for Gaziantep city in the South Anatolia of Turkey. For this purpose, a new attenuation relationship was developed using the data of Zaré and Bard and accelerations were predicted employing this new equation. Deterministic approach, total probability theorem and GIS methodology were all together utilized for the seismic assessments. Seismic hazard maps with 0.25° grid intervals considering the site conditions were produced by the GIS technique. The results indicated that the acceleration values by the GIS hazard modelings were matched with the ones from the deterministic approach, however, they were underestimated comparing with the total probability theorem. In addition, the GIS based seismic hazard maps showed that the current seismic map of Turkey fairly yields conservative acceleration values for the Gaziantep region. Therefore, the constructed GIS hazard models are offered as a base map for a further modification of the current seismic hazard map.  相似文献   

Determination of the Crustal and Thermal Structure of the Erzurum-Horasan-Pasinler Basins (Eastern Türkiye) Using Gravity and Magnetic Data     

Nafiz Maden  Ali Aydin  Fakhraddin Kadirov 《Pure and Applied Geophysics》2015,172(6):1599-1614

  相似文献   

Observation of excess heavy metal concentrations in water resources to infer surface water influences on shallow groundwater: a typical example of the Porsuk River (Eskisehir-Turkey)     

Alptekin  Candan  Yuce  Galip 《Water Resources》2016,43(1):184-199

Water Resources - The Eskisehir province is well-known due to its industrial and agricultural activities, which are a threat for the aquatic environment. Hence, monitoring of water quality in the...  相似文献