Variscan orogeny in the Black Sea region     

Okay  Aral I.  Topuz  Gültekin 《International Journal of Earth Sciences》2017,106(2):569-592

International Journal of Earth Sciences - Two Gondwana-derived Paleozoic belts rim the Archean/Paleoproterozoic nucleus of the East European Platform in the Black Sea region. In the north is a belt...  相似文献   

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction   总被引：1，自引：0，他引：1  

A. I. Okay  O. Monod  P. Moni 《Lithos》2002,64(3-4):155-178

Triassic eclogite and blueschist facies rocks occur as a thrust sheet, 25-km long and over 2-km thick, in an Eocene fold-and-thrust belt in northwest Turkey along the zmir–Ankara suture. The thrust sheet consists mainly of metabasites with minor marble, phyllite and metachert, and rare lenses of serpentinite. The common blueschist facies mineral assemblage in the metabasites is sodic amphibole+epidote+albite+chlorite+phengite±garnet. Sodic amphibole commonly shows replacement by barroisite, and there is continuous petrographic transition from blueschist–metabasites to barroisite-bearing epidote–amphibolites. Eclogite with the mineral assemblage of garnet+sodic pyroxene+sodic–calcic amphibole+epidote is found only in one locality. P–T conditions of the epidote–blueschist facies metamorphism are estimated as 450±50 °C and 11±2 kbar. The blueschist formation was followed by a decrease in pressure and increase in temperature, leading to the development of barroisite-bearing epidote–amphibolites. Phengite, sodic amphibole and barroisite Ar/Ar ages from three metabasic rocks range between 215 and 205 Ma, and indicate Late Triassic high-pressure metamorphism. The Triassic blueschists in northwest Turkey constitute part of a much larger allochthonous tectonic unit of Triassic mafic volcanic rocks. They probably represent the upper layers of a Triassic oceanic plateau, which was accreted to the Laurasian margin during the latest Triassic. The close spatial association of the Triassic and Cretaceous blueschists along the zmir–Ankara suture suggests that the suture represents a long-lived plate boundary of Late Palaeozoic to early Tertiary age.  相似文献   

From transpression to transtension: changes in morphology and structure around a bend on the North Anatolian Fault in the Marmara region     

Aral I. Okay  Okan Tüysüz  inasi Kaya 《Tectonophysics》2004,391(1-4):259

The east–west-trending North Anatolian Fault makes a 17° bend in the western Marmara region from a mildly transpressional segment to a strongly transtensional one. We have studied the changes in the morphology and structure around this fault bend using digital elevation models, field structural geology, and multi-channel seismic reflection profiles. The transpression is reflected in the morphology as the Ganos Mountain, a major zone of uplift, 10 km wide and 35 km long, elongated parallel to the transpressional Ganos Fault segment west of this bend. Flat-lying Eocene turbidites of the Thrace Basin are folded upwards against this Ganos Fault, forming a monocline with the Ganos Mountain at its steep southern limb and the flat-lying hinterland farther north at the flat limb. The sharp northern margin of the Ganos Mountain coincides closely with the monoclinal axis. The strike of the bedding, and the minor and regional fold axes in the Eocene turbidites in Ganos Mountain are parallel to the trace of the Ganos Fault indicating that these structures, as well as the morphology, have formed by shortening perpendicular to the North Anatolian Fault. The monoclinal structure of Ganos Mountain implies that the North Anatolian Fault dips under this mountain at 50°, and this ramp terminates at a decollement at a calculated depth of 8 km. East of this fault bend, the northward dip of the North Anatolian Fault is maintained but it has a normal dip-slip component. This has led to the formation of an asymmetric half-graben, the Tekirdağ Basin in the western Sea of Marmara, containing a thickness of up to 2.5 km of Pliocene to Recent syn-transform sediments. As the Ganos uplift is translated eastwards from the transpressional to the transtensional zone, it undergoes subsidence by southward tilting. However, a morphological relic of the Ganos uplift is maintained as the steep northern submarine slope of the Tekirdağ Basin. The minimum of 3.5 km of fault-normal shortening in the Ganos Mountain, and the minimum of 40 km eastward translation of the Ganos uplift indicate that the present fault geometry has existed for at least the last 2 million years.  相似文献   

Pinus brutia as a biogeochemical medium to detect iron and zinc in soil analysis, chromite deposits of the area Mersin, Turkey     

Zeynep Özdemir 《Chemie der Erde / Geochemistry》2005,65(1):79-88

Soil and pine (Pinus brutia) samples were collected from 64 sites over chromite and ultramafic rocks near Musal?, and over clastic sediments of the Silifke-Anamur areas of Mersin, Turkey. Both sample media were analyzed for their Zn and Fe contents. The results showed similar concentration of both elements in the ash of needles and twigs, with each exhibiting lower concentration than the soils. Zinc was more concentrated in pines from the Silifke-Anamur area than at Musal?, but Fe concentrations were similar in both area. A positive correlation was observed between Zn and Fe in pine and soils (r=0.90 and 0.79, respectively). It is concluded that P. brutia can be used as a biogeochemical sample medium to detect concealed deposits of Zn and Fe.  相似文献   

Democracy,electoral systems and emissions: explaining when and why democratization promotes mitigation     

Zeynep Clulow 《Climate Policy》2019,19(2):244-257

Does democratization help countries mitigate climate change? On the one hand, by increasing the value placed on quality of life, creating more opportunity for environmental actors to influence policymaking and holding elected politicians accountable, an increase in democratic institution and process should promote emissions reduction. On the other hand, the desire to safeguard individual freedom presumably brings with it an aversion to intervene in lifestyle and market decisions, thereby raising the risk of climate inaction. This outcome is further encouraged by the political need to balance (conflicting) environmental and energy interests.

This article evaluates the thesis that democratization promotes mitigation in light of national emissions levels from 1990 to 2012. Using data from the Freedom House, Polity IV and V-Dem indices, World Bank World Development Indicators and the World Resources Institute Climate Data Explorer it conducts a large-N investigation of the emissions levels of 147 countries. Although several quantitative studies have found that domestic political regimes affect emissions levels, this article goes beyond existing research by building a more sophisticated – multilevel- research design to determine whether democracy: (a) continues to be an important driver of emissions when country-level clustering is accounted for and (b) has uniform effects across countries. The results indicate that, even after controlling for country-level clustering and holding constant the other confounding factors, democracy is indeed a significant driver. More strikingly, they reveal that while democracies tend to have lower emissions than non-democracies, democratization spells within the same country do not have the same kind of inhibitory effects as they do between countries. This article also finds tentative evidence that the type of electoral system plays a critical role in shaping the effect of democratization on individual countries.

Key policy insights

• Democracies tend to perform better in terms of emission levels than non-democracies.

• Democratization has non-uniform effects across different countries, with the type of electoral system playing a key role in determining the effect that democratization has on national emissions.

• Further research is needed to develop our understanding of how the political context influences emissions, especially with regard to the influence of pro and anti-decarbonisation actors.

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No significant Alpine tectonic overprint on the Cimmerian Strandja Massif (SE Bulgaria and NW Turkey)     

Silvia Cattò  Massimiliano Zattin  Aral I. Okay 《International Geology Review》2018,60(4):513-529

We provide the first comprehensive picture of the thermochronometric evolution of the Cimmerian Strandja metamorphic massif of SE Bulgaria and NW Turkey, concluding that the bulk of the massif has escaped significant Alpine-age deformation. Following Late Jurassic heating, the central part of the massif underwent a Kimmeridgian-Berriasian phase of relatively rapid cooling followed by very slow cooling in Cretaceous-to-Early Eocene times. These results are consistent with a Late Jurassic–Early Cretaceous Neocimmerian (palaeo-Alpine) phase of north-verging thrust imbrication and regional metamorphism, followed by slow cooling/exhumation driven by erosion. From a thermochronometric viewpoint, the bulk of the Cimmerian Strandja orogen was largely unaffected by the compressional stress related to the closure of the Vardar–?zmir–Ankara oceanic domain(s) to the south, contrary to the adjacent Rhodopes. Evidence of Alpine-age deformation is recorded only in the northern sector of the Strandja massif, where both basement and sedimentary rocks underwent cooling/exhumation associated with an important phase of shortening of the East Balkan fold-and-thrust belt starting in the Middle–Late Eocene. Such shortening focused in the former Srednogorie rift zone because this area had been rheologically weakened by Late Cretaceous extension.  相似文献   

Localization and characterization of cracks in clay‐rocks using frequency and time‐domain induced polarization     

G. Okay  P. Cosenza  A. Ghorbani  C. Camerlynck  J. Cabrera  N. Florsch  A. Revil 《Geophysical Prospecting》2013,61(1):134-152

Induced polarization (IP) is a geophysical method that is potentially sensitive to the presence of cracks in porous rocks and therefore to damage. We performed time‐domain and frequency domain IP measurements at the Tournemire Underground Research Laboratory (URL, Aveyron, France) in areas where different types of cracks are observed. These cracks correspond to both tectonic fractures and new cracks associated with stress release and desiccation resulting from the excavation of a gallery. These measurements were performed both in eastern and northern galleries of the test site. The eastern gallery was excavated in 1996 while the northern gallery was excavated recently in 2008. This gives us the opportunity to study the electrical characteristics of the excavation damaged zone surrounding the galleries with respect to the age of the excavation. Longitudinal profiles were performed along the floor of the galleries with 48 Cu/CuSO₄ electrodes separated by a distance of 20 cm. Chargeability and resistivity were inverted using a Gauss‐Newton iterative approach assuming an isotropic heterogeneous clay‐rock material. The resulting IP tomograms show a correlation between high values of chargeability and the presence of calcite‐filled tectonic fractures. X‐ray analysis indicates that the presence of pyrite in these fractures is a potential source of the observed IP signals. The cracks associated with the mechanical damage of the formation exhibit low values of chargeability, on the same order of magnitude than the chargeability of the clay‐rock matrix and are therefore hardly observable. A smaller IP response associated with the presence of these cracks is observed in the older gallery and this observation is qualitatively related to the desaturation process associated with these cracks. In a specific area of one of the galleries, the presence of calcareous nodules is observed to be an important source of anomalous chargeability. This signature seems to be associated with the presence of pyrite.  相似文献   

The tectonics of the Strandja Massif: late-Variscan and mid-Mesozoic deformation and metamorphism in the northern Aegean   总被引：2，自引：1，他引：2  

A. Okay  M. Satır  O. Tüysüz  S. Akyüz  F. Chen 《International Journal of Earth Sciences》2001,90(2):217-233

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Mineralogy,petrology, and phase relations of glaucophane-lawsonite zone blueschists from the Tavşanli Region,Northwest Turkey     

A. I. Okay 《Contributions to Mineralogy and Petrology》1980,72(3):243-255

Glaucophane-lawsonite facies blueschists representing a metamorphosed sequence of basic igneous rocks, cherts and shales have been investigated northeast of the district of Tav?anli in Northwest Turkey. Sodic amphiboles are rich in magnesium reflecting the generally high oxidation states of the blueschists. Lawsonite has a very uniform composition with up to 2.5 wt.% Fe₂O₃. Sodic pyroxenes show an extensive range of compositions with all the end-members represented. Chlorites are uniform in their Al/(Al+Fe+Mg) ratio but show variable Fe/ (Fe+Mg) ratios. Garnets from metacherts are rich in spessartine (>50%) whereas those from metabasites are largely almandine. Pistacite rich epidote is found in metacherts coexisting with lawsonite. Phengites are distinctly higher in their Fe, Mg and Si contents than those from greenschist facies. Hematites with low TiO₂ are ubiquitous in metacherts. Fe²⁺/Mg partitioning between chlorite and sodic amphibole is strongly controlled by the calcium content of the sodic amphibole and ranges from 1.1 for low calcium substitution to 0.8 for higher calcium substitution. The Al/Fe³⁺ partition coefficient between sodic amphibole and sodic pyroxene is 2.1. A model system has been constructed involving projections from lawsonite, iron-oxide and quartz onto a tetrahedron with Na, Al, Fe²⁺ and Mg at its apices. Calcite is treated as an indifferent phase. The model system illustrates the incompatibility of the sodic pyroxene with chlorite in the glaucophanelawsonite facies; this assemblage is represented by sodic amphibole. Sodic amphibole compositions are plotted in terms of coexisting ferromagnesian minerals. Five major areas on the sodic amphibole compositional field are delineated, each associated with one of the following minerals: chlorite, stilpnomelane, talc, almandine, deerite.  相似文献   

A fore-arc origin for the Thrace Basin,NW Turkey     

N. Görür  A. I. Okay 《International Journal of Earth Sciences》1996,85(4):662-668

Hydrocarbon-bearing Thrace Basin occupies much of the European part of Turkey. The Middle Eocene to Oligocene sequence in the centre of the basin exceeds 9 km in thickness. Based on the stratigraphy, structure and the regional context of this basin, we propose that it developed as a fore-arc basin between the medial Eocene and the Oligocene, above the northward subducting Intra-Pontide Ocean. Its post-Miocene history has been dominated mainly by wrench tectonics resulting from the activity of the now-deactivated northwestern strand. of the present-day North Anatolian fault zone.  相似文献