Sample records for aegean island arc

  1. Temporal and spatial variations in provenance of Eastern Mediterranean Sea sediments: Implications for Aegean and Aeolian arc volcanism

    Klaver, Martijn; Djuly, Thomas; de Graaf, Stefan; Sakes, Alex; Wijbrans, Jan; Davies, Gareth; Vroon, Pieter


    The Eastern Mediterranean Sea (EMS) is the last remnant of the Tethys Ocean that has been subducted to the north since the Jurassic. Subduction has led to the formation of multiple island arcs in the EMS region where the Aeolian and Aegean arcs are currently active. The EMS is surrounded by continents and receives a large sediment input, part of which is transported down with the subducting slab into the mantle and potentially contributes a major flux to the arc volcanism. An along-arc gradient in the composition of subducting sediment has been evoked to explain the distinct geochemical signature of the easternmost volcanic centre of the Aegean arc, but direct evidence for this proposal is lacking. We present a detailed study of the mineralogical, major-, trace elements and Sr-Nd-Hf-Pb isotope composition of 45 Neogene EMS sediment samples obtained from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill sites and box cores to characterise their geochemical composition, distinguish provenance components and investigate the temporal and spatial variation in provenance to evaluate the potential changing contribution of subducted EMS sediment to Aegean and Aeolian arc volcanism. Based on trace element characteristics of EMS sediments, we can distinguish four provenance components. Nile sediment and Sahara dust are the main components, but contributions from the Tethyan ophiolite belt and arc volcanic rocks in the north are also recognised. Pliocene and Quaternary EMS sediment records a strong geochemical gradient where Nile River sediment entering the EMS in the east is progressively diluted by Sahara Desert dust towards the west. Pre-Messinian samples, however, have a remarkably homogeneous composition with Nile sediment characteristics. We relate this rapid increase in Sahara dust contribution to a late Miocene climate shift leading to decreased Nile runoff and aridification of the Sahara region. EMS sediment has a restricted range in Pb isotopes

  2. Zircon crytallization and recycling in the magma chamber of the rhyolitic Kos Plateau Tuff (Aegean arc)

    Bachman, O.; Charlier, B.L.A.; Lowenstern, J. B.


    In contrast to most large-volume silicic magmas in continental arcs, which are thought to evolve as open systems with significant assimilation of preexisting crust, the Kos Plateau Miff magma formed dominantly by crystal fractionation of mafic parents. Deposits from this ??? 60 km3 pyroclastic eruption (the largest known in the Aegean arc) lack xenocrystic zircons [secondary ion mass spectrometry (SIMS) U-Pb ages on zircon cores never older than 500 ka] and display Sr-Nd whole-rock isotopic ratios within the range of European mantle in an area with exposed Paleozoic and Tertiary continental crust; this evidence implies a nearly closed-system chemical differentiation. Consequently, the age range provided by zircon SIMS U-Th-Pb dating is a reliable indicator of the duration of assembly and longevity of the silicic magma body above its solidus. The age distribution from 160 ka (age of eruption by sanidine 40Ar/39Ar dating; Smith et al., 1996) to ca. 500 ka combined with textural characteristics (high crystal content, corrosion of most anhydrous phenocrysts, but stability of hydrous phases) suggest (1) a protracted residence in the crust as a crystal mush and (2) rejuvenation (reduced crystallization and even partial resorption of minerals) prior to eruption probably induced by new influx of heat (and volatiles). This extended evolution chemically isolated from the surrounding crust is a likely consequence of the regional geodynamics because the thinned Aegean microplate acts as a refractory container for magmas in the dying Aegean subduction zone (continent-continent subduction). ?? 2007 Geological Society of America.

  3. Zircon crystallization and recycling in the magma chamber of the rhyolitic Kos Plateau Tuff (Aegean arc)

    Bachman, O.; Charlier, B.L.A.; Lowenstern, J. B.


    In contrast to most large-volume silicic magmas in continental arcs, which are thought to evolve as open systems with significant assimilation of preexisting crust, the Kos Plateau Tuff magma formed dominantly by crystal fractionation of mafic parents. Deposits from this ~60 km3 pyroclastic eruption (the largest known in the Aegean arc) lack xenocrystic zircons [secondary ion mass spectrometry (SIMS) U-Pb ages on zircon cores never older than 500 ka] and display Sr-Nd whole-rock isotopic ratios within the range of European mantle in an area with exposed Paleozoic and Tertiary continental crust; this evidence implies a nearly closed-system chemical differentiation. Consequently, the age range provided by zircon SIMS U-Th-Pb dating is a reliable indicator of the duration of assembly and longevity of the silicic magma body above its solidus. The age distribution from 160 ka (age of eruption by sanidine 40Ar/39Ar dating; Smith et al., 1996) to ca. 500 ka combined with textural characteristics (high crystal content, corrosion of most anhydrous phenocrysts, but stability of hydrous phases) suggest (1) a protracted residence in the crust as a crystal mush and (2) rejuvenation (reduced crystallization and even partial resorption of minerals) prior to eruption probably induced by new influx of heat (and volatiles). This extended evolution chemically isolated from the surrounding crust is a likely consequence of the regional geodynamics because the thinned Aegean microplate acts as a refractory container for magmas in the dying Aegean subduction zone (continent-continent subduction).

  4. Reply to: 'A late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean Arc'

    Duermeijer, C.E.; Langereis, C.G.


    During the 80s, a number of seminal papers were published by the Gif-sur-Yvette group of Carlo Laj and co-workers, on the late Neogene palaeomagnetic rotations of the Aegean and, in particular, of the Aegean Arc system. These studies shed new light on the tectonic evolution of the region (e.g. [1,2

  5. Present situation and future prospects of electricity generation in Aegean Archipelago islands

    The Aegean Archipelago is a remote Hellenic area, including several hundreds of scattered islands of various sizes. In these islands more than 600,000 people are living mainly in small remote communities. The main economical activities of the islanders are apart from tourism, seafaring, fishery, agriculture and stock farming. One of the major problems of the area is the insufficient infrastructure, strongly related with the absence of an integrated and cost-effective electrification plan. In this context, the present work is concentrated on analyzing the present situation and demonstrating the future prospects of electricity generation in the Aegean Archipelago islands. For this purpose, one should first investigate the time evolution of the corresponding electricity generation parameters (i.e. annual electricity consumption, peak power demand, capacity factor, specific fuel consumption) for the last 30 years. Subsequently, the corresponding diesel and heavy-oil consumption along with the electricity production cost for every specific autonomous power station of the area are investigated. Special attention is paid in order to estimate the contribution of renewable energy sources (RES) in the energy balance of each island. Finally, an attempt is made to describe in brief the most realistic electricity production solutions available, including the operation of hybrid RES-based power plants in collaboration with appropriate energy storage facilities. Additionally, the idea of connecting the islands of the area with the mainland and interconnecting them is also taken into consideration

  6. Development of a behavioural framework for analyzing employment mobility decisions in island areas: the case of the Aegean Islands, Greece

    Eleni Kitrinou


    Full Text Available This paper proposes a theoretical framework to model employment mobility in island areas. It aims at identifying the critical factors affecting the decision of the employees to relocate their workplace to an island area, given a possible residential relocation. Emphasis is given to the role of transport and telecommunications systems on the region’s connectivity and accessibility. Discrete choice models are developed, using both observed and latent variables for the workplace relocation decision to the Aegean island area in Greece. Data was collected in the year 2012 from 518 Greek employees. Findings indicate the importance of the role of transport and telecommunications systems for employment mobility in island areas. The estimated choice models identified profiles of the employees who are prone to: a keep their current workplace; b relocate their workplace to the island area; c change occupation after residential relocation. Finally, the sample enumeration method integrates the models’ results across all Greek employees.

  7. Uluslarası Antlaşmalar Işığında Ege Adaları Sorunu///The Aegean Islands Issue under the Light of International Treaties

    Neslihan ALTUNCUOĞLU


    This article examines the Aegean Island Issue within the scope of Turkish-Italian and German Relations during World War II. The Aegean Islands Issue has been one of the most commonly discussed regional problems since the first quarter of the 20thcentury. Although the Treaty of Lausanne (1923) introduced a short-term solution to the Aegean Islands Issue Italy and Germany reopened the issue for their own national interests. Because of the strategic significance of the Aegean islands, at the b...

  8. Car-borne and on foot scintillometer survey of the Aegean Sea Islands (Greece). Pt. B

    This study being the continuation of a previous report (DEMO 84/8G) gives a detailed description and interpretation of the results of the radiometric survey in general and of the radiometric anomalies more particularly of fifty-one Aegean islands of Greece. The main radiometric anomalies from the point of view of great surface extension and/or high concentration in soluble and/or total uranium are indicated. Further estimation and investigation of the proven uraniferous regions where such anomalies have been traced are suggested. (author)

  9. Isotope geochemistry of recent magmatism in the Aegean arc: Sr, Nd, Hf, and O isotopic ratios in the lavas of Milos and Santorini-geodynamic implications

    Briqueu, L.; Javoy, M.; Lancelot, J.R.; Tatsumoto, M.


    In this comparative study of variations in the isotopic compositions (Sr, Nd, O and Hf) of the calc-alkaline magmas of the largest two volcanoes, Milos and Santorini, of the Aegean arc (eastern Mediterranean) we demonstrate the complexity of the processes governing the evolution of the magmas on the scale both of the arc and of each volcano. On Santorini, the crustal contamination processes have been limited, effecting the magma gradually during its differentiation. The most differentiated lavas (rhyodacite and pumice) are also the most contaminated. On Milos, by contrast, these processes are very extensive. They are expressed in the 143Nd/144Nd vs. 87Sr/86Sr diagram as a continuous mixing curve between a mantle and a crustal end member pole defined by schists and metavolcanic rocks outcropping on these volcanoes. In contrast with Santorini, the least differentiated lavas on Milos are the most contaminated. These isotopic singularities can be correlated with the geodynamic evolution of the Aegean subduction zone, consisting of alternating tectonic phases of distension and compression. The genesis of rhyolitic magmas can be linked to the two phases of distension, and the contamination of the calc-alkaline mantle-derived magmas with the intermediate compressive phase. The isotopic characteristics of uncontaminated calc-alkaline primitive magmas of Milos and Santorini are directly comparable to those of magmas generated in subduction zones for which a contribution of subducted sediments to partial melts from the mantle is suggested, such as in the Aleutian, Sunda, and lesser Antilles island arcs. However, in spite of the importance of the sediment pile in the eastern Mediterranen oceanic crust (6-10 km), the contribution of the subducted terrigenous materials remains of limited amplitude. ?? 1986.

  10. Multi-activity and Brand Name Local Products on an Island of the North Aegean, Greece

    Fotis Chatzitheodoridis


    Full Text Available The present work refers to a research that took place on Limnos, an island found in North Aegean, the more northern islander region of Greek Archipelagos. In the frame of the research, the factors that shape and influence the rural growth of the island were studied. Via these factors, the structure of rural occupation, as well as the multi-activity phenomenon is described. Moreover, the forms of rural occupation are combined with the farmer's confidence and opinion concerning the brand name rural products of the island. From the results of this research it becomes clear that the phenomenon of rural multi-activity is particularly intense and is related to other occupations in the tertiary sector. The brand name rural local products are mostly supported by the exclusively and mainly occupied in primary sector people, while the multi-activated young people that are secondarily or auxiliary occupied in agriculture dispute the value of local brand name products and their contribution in the growth of the island.

  11. STS-56 ESC Earth observation of Limnos Island in the Aegean Sea


    STS-56 electronic still camera (ESC) Earth observation image taken aboard Discovery, Orbiter Vehicle (OV) 103, shows Limnos Island in the Aegean Sea. The image was recorded with a 300mm lens on the Hand-held, Earth-oriented, Real-time, Cooperative, User-friendly, Location-targeting and Environmental System (HERCULES). HERCULES is a device that makes it simple for Shuttle crewmembers to take pictures of Earth as they merely point a modified 35mm camera and shoot any interesting feature, whose latitude and longitude are automatically determined in real time. In this observation, the center coordinates are 39.9 degrees north latitude and 25.3 degrees east longitude. The camera was in shutter priority mode with a 1/500-second shutter speed and -2/3 exposure compensation. Digital file name is ESC03037.IMG.

  12. On Entrepreneurs and Entrepreneurship of the Olive-oil Economy in the Aegean: The Case of Lesvos Island

    Evridiki Sifneos


    Full Text Available This article summarizes the conclusions of a study on entrepreneurial activities related to the cycle of the olive-oil economy in Lesvos, an island in the North-Eastern Aegean, from the eighteenth century until the middle of the twentieth century. It is based on research and observations drawn from a multiform primary material, such as companies' records, communal and family archives, consular and administrative reports, as well as secondary sources which allow comparisons with other oleiferous regions and connect the economy of Lesvos to the broader Aegean and Mediterranean environment.It points out that the single cultivation phenomenon, though associated to the economy of risk, obeyed to the market's command and was prepared by the abolition of the governor's monopoly on the oil trading and the consequent opening of the market. This enabled the Christian ottoman subjects to develop the administration of intensive olive growing, mechanized oil extraction and trade expansion. Olive oil and soap were the two basic commodities of the island's export revenues that were commercialised, despite their low quality, into a wide range of port and island markets of the Asia Minor coast, the Aegean islands and the Black Sea. Moreover, the article explores the type of commercial and industrial enterprises and the characteristics of the olive-cycle entrepreneurs. It concludes with the commercial crisis suffered from the major political and economic changes of the twentieth century and the consequent reorientation of Lesvos' businessmen towards Crete and Piraeus, the olive manufacturing centres of the Neohellenic state.

  13. Geochemical studies on island arc volcanoes

    This paper summarizes advances in three topics of geochemical studies on island arc volcanoes, which I and my colleagues have been investigating. First one is strontium isotope studies of arc volcanic rocks mainly from Japanese island arcs. We have shown that the precise spatial distribution of the 87Sr/86Sr ratio reflects natures of the subduction structure and slab-mantle interaction. Based on the 87Sr/86Sr ratio of volcanic rocks in the northern Kanto district, where two plates subduct concurrently with different directions, the existence of an aseismic portion of the Philippine Sea plate ahead of the seismic one was suggested. Second one is geochemical monitoring of active arc volcanoes. 3He/4He ratio of volcanic volatiles was shown to be a good indicator to monitor the behavior of magma: ascent and drain-back of magma result in increase and decrease in the ratio, respectively. In the case of 1986 eruptions of Izu-Oshima volcano, the ratio began to increase two months after big eruptions, reaching the maximum and decreased. Such delayed response is explained in terms of travelling time of magmatic helium from the vent area to the observation site along the underground steam flow. Third one is remote observation of volcanic gas chemistry of arc volcanoes, using an infrared absorption spectroscopy. During Unzen eruptions starting in 1990, absorption features of SO2 and HCl of volcanic gas were detected from the observation station at 1.3 km distance. This was the first ground-based remote detection of HCl in volcanic gas. In the recent work at Aso volcano, we could identify 5 species (CO, COS, CO2, SO2 and HCl) simultaneously in the volcanic plume spectra. (author)

  14. Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

    Bouvet De Maisonneuve, Caroline; Bachmann, Olivier; Burgisser, Alain


    Silicic pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to or at the fragmentation level. We have characterized four types of pumices from the non-welded rhyolitic Kos Plateau Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of pumice (>90 vol.%) shows highly elongated tubular vesicles. These tube pumices occur throughout the eruption. Less common pumice types include: (1) “frothy”...

  15. Barrier island arcs along abandoned Mississippi River deltas

    Penland, S.; Suter, J.R.; Boyd, Ron


    Generation of transgressive barrier island arcs along the Mississippi River delta plain and preservation of barrier shoreline facies in their retreat paths on the inner shelf is controlled by: (1) shoreface translation; (2) age of the transgression; and (3) the thickness of the barrier island arc sediment package. Barrier island arcs experience an average relative sea level rise of 0.50-1.00 cm yr-1 and shoreface retreat rates range from 5-15 m yr-1. Young barrier island arc sediment packages (Isles Dernieres) are thin and have experienced limited landward retreat of the shoreface. Older barrier island arcs (Chandeleur Islands) are thicker and have experienced significant landward movement of the shoreface because of the greater time available for retreat. If the transgressed barrier shoreline sediment package lies above the advancing ravinement surface, the entire sequence is truncated. A thin reworked sand sheet marks the shoreface retreat path. The base of the transgressive sediment package can lie below the ravinement surface in older barrier shorelines. In this setting, the superstructure of the barrier shoreline is truncated, leaving the basal portion of the transgressive sequence preserved on the inner shelf. A variety of transgressive stratigraphic sequences from sand sheets to truncated barrier islands to sand-filled tidal inlet scars have been identified by high resolution seismic profiling across the shoreface retreat paths of Mississippi delta barrier island arcs. One of these examples, the Isles Dernieres, represents a recently detached barrier island arc in the early stages of transgression. An older example, the Chandeleur Islands, represents a barrier island arc experiencing long-term shoreface retreat. This paper describes the stratigraphic character and preserved transgressive facies for the Isles Dernieres and Chandeleur Islands. ?? 1985.

  16. Carbon fluxes from hydrothermal vents off Milos, Aegean Volcanic Arc, and the influence of venting on the surrounding ecosystem.

    Dando, Paul; Aliani, Stefano; Bianchi, Nike; Kennedy, Hilary; Linke, Peter; Morri, Carla


    The island of Milos, in the Aegean Sea, has extensive hydrothermal fields to the east and southeast of the island with additional venting areas near the entrance to and within the central caldera. A calculation of the total area of the vent fields, based on ship and aerial surveys, suggested that the hydrothermal fields occupy 70 km2, twice the area previously estimated. The vents ranged in water depth from the intertidal to 300 m. As a result of the low depths there was abundant free gas release: in places water boiled on the seabed. The stream of gas bubbles rising through the sandy seabed drove a shallow re-circulation of bottom seawater. The majority of the water released with the gas, with a mean pH of 5.5, was re-circulated bottom water that had become acidified in contact with CO2 gas and was often diluted by admixture with the vapour phase from the deeper fluids. The major component of the free gas, 80%, was CO2, with an estimated total flux of 1.5-7.5 x 1012 g a-1. The methane flux, by comparison, was of the order of 1010 g a.-1 Using methane as a tracer it was shown that the major gas export from the vents was below the thermocline towards the southwest, in agreement with the prevailing currents. Areas of hydrothermal brine seepage occurred between the gas vents and occasional brine pools were observed in seabed depressions. Under relatively calm conditions, many of the brine seeps were covered by thick minero-bacterial mats consisting of silica and sulphur and surrounded by mats of diatoms and cyanobacteria. The minerals were not deposited in the absence of bacteria. Storms disrupted the mats, leading to an export of material to the surrounding area. Stable isotope data from sediments and sediment trap material suggested that exported POM was processed by zooplankton. The combined effects of the geothermal heating of the seabed, the large gas flux, variation in the venting and the effect of the brine seeps had a dramatic effect on the surrounding

  17. Assessing the determinants of local acceptability of wind-farm investment: A choice experiment in the Greek Aegean Islands

    This paper aims at analysing the factors, which motivate communities to resist the installation of wind farms in their vicinity. To this end, the choice experiment methodology was employed in communities in two Greek Aegean Islands to assess the determinants of preferences towards different wind-farm projects. Unlike other studies, the willingness to accept welfare measure was adopted. The results of our analysis show that the conservation status of the area where the wind farms are to be installed, along with the governance characteristics of the planning procedure are the most important determinants of local community welfare in relation to wind farms. In contrast to other studies, we find that the physical attributes of wind farms appear to be of less relative importance from a local community welfare point of view. Implications for the EU's future energy policy are drawn.

  18. diet composition of the salamander lyciasalamandra luschani basoglui on the greek island of kastellorizo in the southeast aegean sea


    the diet composition of the lycian salamander lyciasalamandra luschani basoglui across both age and sex groups was studied.specimens were collected from a small island in the southeast aegean sea.the dominant prey group of juveniles consisted of collembola,while coleoptera dominated the diet of males and females.the number and size of prey items consumed by males and females of l.luschani basoglui were quite similar,while juveniles ate fewer items of much smaller size.the numerical abundance along with the four measures of the size of prey permitted discrimination among males,females and juveniles.although discrimination between adults and juveniles is expected due to dissimilarity in body size,discrimination between males and females remains inexplicable despite their similarity in body size.future studies should be focused on understanding how and why prey choice differs between sexes in l.luschani basoglui.

  19. April 16, 2015 Crete Island Earthquake (Mw=5.9) Series and its Seismotectonic Significance, Southern Aegean Sea

    Yalçın, Hilal; Kürçer, Akın; Gülen, Levent


    The active deformation of the southern Aegean Sea is a result of the northward motion of the African and Arabian Plates with respect to the Eurasian Plate in the Eastern Mediterranean Region. The Hellenic subduction zone plays a key role in the active tectonics of the region. On 16 April, 2015, a moderate earthquake occurred on the eastern part of Hellenic arc (south of Crete island), with a moment magnitude of Mw=5.9. A series of aftershocks were occurred within four months following the mainshock, which have magnitudes varying from Mw = 3.4 to 5.4. Source parameters of the 16 April 2015 earthquake have been modeled in order to reveal the regional stress tensor and the tectonic style of the region. In this study, the source parameters of the main shock and 36 aftershocks that have magnitudes M≥3.4 have been determined and modeled by seismic moment tensor waveform inversion method developed by Sokos and Zahradnik (2006) algorithm using the near-field and regional waveforms. The depth of earthquakes are varied from 2 to 61 km. Stress tensor can describe reliably principle stress axes (σ1, σ2, σ3), their relative size and stress field variations. Stress tensor inversions have been carried out using the Micheal method (1984, 1987). In this study, 16 April 2015 Crete Earthquake mainshock (Mw=5.9), a total of 36 earthquake moment tensor solutions that belong to the Crete earthquake sequence and 24 earthquake moment tensor solutions of previous main shocks in the region have been compiled and used in the stress inversion calculation. Orientations of σ1, σ2 and σ3 were computed and the principal directions are projected onto a lower hemisphere Wulff net. The best fit was attained for Phi = 0.38+/‑0.13609 and indicated that the stress regime revealed strike-slip faulting with reverse component and for the azimuth and plunge pair of (-161.6°, 21.7°) for σ1, (-11.1°, 65.4°) for σ2 and (103.8°, 10.9°) for σ3. At the final step of the study, Gutenberg and

  20. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    Manga, Michael; Hornbach, Matthew J.; Friant, Anne Le; Ishizuka, Osamu; Stroncik, Nicole; Adachi, Tatsuya; Aljahdali, Mohammed; Boudon, Georges; Breitkreuz, Christoph; Fraass, Andrew; Fujinawa, Akihiko; Hatfield, Robert; Jutzeler, Martin; Kataoka, Kyoko; Lafuerza, Sara


    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to 15 km from the crest in the back arc direct...

  1. Radiometric dating of sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea

    Sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea were dated using the 210Pb method. The average unsupported 210Pb inventory in the cores was calculated to be 3256 Bq m-2. The corresponding mean annual 210Pb flux of 105 Bq m-2 year-1 is comparable to estimates of the atmospheric flux given in the literature. 210Pb fluxes calculated from the unsupported 210Pb inventories in cores are also comparable with the 210Pb vertical fluxes determined from settling particles off the coast of Milos Island. The highest unsupported 210Pb concentrations (89 Bq kg-1) were measured in the sediments nearest to the hydrothermal vent area suggesting that the sedimentation rate is lowest at this site. Direct gamma measurements of 210Pb were used to date three sediment cores that are located at different distances from the vent zone: one is in the immediate vicinity of the vent; and others are outside the zone. Sedimentation rates for these cores, calculated using the CRS and CIC models, ranged from 0.088±0.008 cm year-1 to 0.14±0.01 cm year-1. Where both models were applicable, the results given by the two methods were in good agreement. 137Cs concentrations in all three cores generally declined with depth but showed no clear signal of either the period of maximum fallout from weapons testing or the Chernobyl accident. 210Po activities were also measured and the maximum 210Po concentration was in the sediment surface layer (166 Bq kg-1)

  2. A list of macrofauna on the continental shelf of Gökçeada Island (northern Aegean Sea) with a new record (Gryphus vitreus Born, 1778) (Brachiopoda, Rhynchonellata) for the Turkish seas

    Gönülal, Onur; Güreşen, Sedat Ozan


    Abstract Long-term sampling (1974-2013) of macro fauna of the Gökçeada Island (northern Aegean Sea) provided qualitative information on many taxa including Porifera, Cnidaria Mollusca, Arthropoda, Brachiopoda, Bryozoa, Spinculida, Echinodermata, Chordata. Gryphus vitreus (Brachiopoda) and Funiculina quadrangularis (Pallas, 1766) are the first records for the Turkish seas and the Aegean coast of Turkey, respectively. The present paper aims to describe macrofauna occurring on the continental sh...

  3. Making and breaking an Island arc: a new perspective from the Oligocene Kyushu-Palau arc

    Ishizuka, O.; Taylor, R. N.; Yuasa, M.; Ohara, Y.


    The Kyushu-Palau Ridge (KPR) is a 2000km long remnant island arc that is separated from the active Izu-Bonin-Mariana (IBM) arc system by a series of spreading and rift basins. In this study we present 40Ar/39Ar ages and geochemical data for new samples taken from the entire length of the Kyushu-Palau arc. As such, this data provides the first comprehensive evaluation of temporal and spatial changes that are present in an Eocene-Oligocene island arc. Kyushu-Palau arc geochemistry is evaluated alongside new data from the conjugate arc which is stranded within the IBM fore-arc. Boninitic magmatism gave way to transitional arc suites including high-Mg andesites at c. 45 Ma (Ishizuka et al., 2006). After the transitional 45-41 Ma period, a mature arc system developed through the Eocene-Oligocene time: This volcanism is now preserved as the KPR. Dating results from 33 sites indicate that the KPR was active between 25 and 43 Ma, but the majority of the exposed volcanism occurred in the final phase of this arc, between 25 and 27 Ma. Unlike the IBM, the KPR has only limited systematic along-arc trends and does not include any of the strongly HIMU lavas found to the south of Izu-Bonin. Two components found along the KPR are found to have geochemistry that suggests an origin in the supra-subduction mantle rather than from the descending ocean crust. Firstly, in the south of the arc, EM-2-like lavas are present where the West Philippine Basin was in the final stages of spreading. Secondly, EM-1-like lavas are present in a restricted section of the arc, suggesting a localised heterogeneity. Subduction flux beneath the KPR generally imparted a Pb isotope vector towards low Δ8/4 (19). This is a similar trend to the Eocene/Oligocene lavas found on the eastern side of the basins which split the arc at 25Ma. Another geochemical heterogeneity is found at the KPR-Daito Ridge intersection where arc magmatism occurred on pre-existing Daito Ridge crust: a Cretaceous remnant arc

  4. Abundance and Distribution of Zooplankton in CoastalArea of Gokceada Island (Northern Aegean Sea)

    Tarkan, Abmet Nuri


    Abstract This study was carried out in order to determine population of zooplankton in the coastal waters of Gokgeada. At the 10 stations of those depths ranging from 20 in to 30 in, the measurements of temperature, salinity and oxygen were made, and zooplankton samples were collected vertically and horizontally using plankton nets. In the neritic waters of the island, the effects of the Black Sea waters through Dardanelles were observed and zooplankton species of the Black Sea found. F...

  5. Ductile nappe stacking and refolding in the Cycladic Blueschist Unit: insights from Sifnos Island (south Aegean Sea)

    Aravadinou, Eirini; Xypolias, Paraskevas; Chatzaras, Vasileios; Iliopoulos, Ioannis; Gerogiannis, Nikolaos


    New geological and structural mapping combined with kinematic and amphibole chemistry analyses is used to investigate the deformation history of the Cycladic Blueschist Unit (CBU) on Sifnos Island (Cyclades, Aegean Sea). We concentrate on north Sifnos, an area characterized by exceptionally well-preserved eclogites and blueschists. Our data show that the early, main phase (D2) of ductile deformation in the CBU occurred synchronous with the transition from prograde to close-to-peak retrograde conditions. This deformation phase took place at middle Eocene and is related to ESE-directed thrusting that emplaced the metavolcano-sedimentary subunit over the Marble subunit. The subsequent exhumation-related (D3) deformation is characterized by gently NE-plunging folds and NE-directed contractional shear zones that formed parallel to the axial planes of folds. NE-directed shearing occurred under blueschist and transitional blueschist-/greenschist-facies conditions during late Eocene-Oligocene and caused the restacking of the early nappe pile. We suggest that a mechanism of ductile extrusion of the CBU in a tectonic setting of net compression could explain better the recorded exhumation-related deformation than a mechanism of syn- and post-orogenic extension. Our new kinematic results in combination with previous works in the Cyclades area reveal a regional scale change in tectonic transport direction from (W)NW-(E)SE at Late Cretaceous-middle Eocene to (E)NE-(W)SW at late Eocene-Oligocene times. The observed change in transport direction may be governed by the relative motion of Africa with respect to Europe during Alpine orogeny.

  6. Formation of heterogeneous magmatic series beneath North Santorini, South Aegean island arc

    Bailey, John C; Jensen, E.S.; Hansen, A.; Kann, A.D.J.; Kann, K.

    The geochemistry of basaltic to dacitic lavas and dykes in the volcanic centres of NorthSantorini (Greece) has been investigated using elemental and Sr-Nd-Pb isotopic data andthree main magmatic series with sub-parallel trace element patterns for basalts can bedistinguished. The basalts have Sr and...... subducted slab to the overlying mantle. The three main magmatic series followed independent paths of assimilation of upper crustal materials during fractional crystallization. Assimilation was more pronounced at the basaltic stage. The long-lived histories of the three main magmatic series imply repetitive...

  7. A new metamorphic map of Syros Island (Aegean Sea, Greece): implications for strain localization from prograde to retrograde path

    Laurent, Valentin; Jolivet, Laurent; Roche, Vincent; Augier, Romain; Scaillet, Stéphane; Cardello, Luca


    The Aegean domain is located in the eastern part of the Mediterranean and has undergone a complex Alpine history that can be summarized in two successive episodes: (1) The formation of the Hellenides-Taurides belt due to the convergence between Eurasia and Africa; during this episode, a series of oceanic and continental nappes entered the subduction zone and were thrust on top of each other in a HP-LT metamorphic context. (2) From 35-30 Ma, an acceleration of slab retreat led to the collapse of the belt and the formation of large detachments. The island of Syros (Cycladic Blueschists belt) is worldwide known for the excellent preservation of HP-LT tectonic and metamorphic features associated with these processes, possibly providing one of the best places to study the deformation and metamorphic evolution of the subduction interface. Syros has recorded a complex deformation history during both the prograde and retrograde phase that resulted in the juxtaposition of two main units: (1) the Cycladic Blueschists Unit (CBU), and (2) the Vari unit cropping out in the SE of the island. Conflicting tectonic interpretations have been proposed to explain the evolution of the island, in part reflecting the lack of consensus about the detailed tectonic structure of the CBU. A new geological and metamorphic map of Syros is proposed to better characterize the different structures related to prograde and/or retrograde deformation stages. High-resolution field-mapping, combined with detailed structural-petrological observations, allows us to subdivide the CBU into three sub-units separated by major ductile shear zones. From top to bottom, these are: 1) the Kampos, 2) the Chroussa, and 3) the Posidonia units. Each of these units experienced similar peak eclogite-facies conditions (ca. 20 kbar - 550 °C), variably overprinted under blueschist- and greenschist-facies conditions across the nappe pile. New ductile structures have been discovered. Among those, a new large-scale top

  8. Petrologic Evolution of Palau; A Nascent Island Arc

    Hawkins, J. W.; Ishizuka, O.


    Initiation of subduction in intra-oceanic settings requires relative differences in plate thickness and density (i.e., age difference); a major zone of weakness separating the plates, e.g., a fracture zone; and a change in relative vectors of movement to cause convergence. These factors help explain the origin of the southern- most part of the > 2500 km long Kyushu - Palau Ridge (KPR). Palau Islands, at 7 deg 30 ' N, are the only significant emergent feature on KPR. Small islands are mainly uplifted Pliocene and younger reef carbonate. Large islands are mainly volcanic comprising rare boninite; major basalt, basaltic andesite and andesite; and minor dacite. Polymict breccia is abundant; sills, flows, dikes are common; pillows are rare. The same rock types, as well as high-Mg basalt, were dredged from the Palau Trench. Volcanism on Palau began in late Eocene and ended by early Miocene. Rocks are low-K primitive island arc- tholeiite series. None are MORB. REE and HFSE require a depleted mantle source. Zr* and Ti* suggest that melts interacted with OL-PX rocks of upper mantle or deep crust cumulates. Moderate enrichment of LILE and LREE indicate influx of "dehydration fluid." Ce/Ce* and Eu/Eu* show no evidence for subducted sediments or recycling of arc- derived clastics yet there is no accreted sedimentary prism. This paradox may be owing to lack of arc or terrigenous clastics on seafloor formed in open ocean "sterile" equatorial latitudes. Plate reconstructions and paleomagnetic data suggest that the "arc" probably formed on the trace of a transform fault that has migrated northward and rotated clockwise up to 90 deg. since Oligocene time. Episodes of transtension allowed upwelling of relatively fertile hot mantle into depleted mantle and sheared, altered, rocks of the transform. Episodes of transpression may have initiated subduction of seafloor having a thin cover of pelagic sediments (calcareous and radiolarian ooze, chert, chalk, limestone) deposited far from

  9. Geometry of the Aegean Benioff zones

    M. Knapmeyer


    Full Text Available The morphology of the Aegean Benioff zone was reconstructed using 1366 hypocentres from the PDE catalogue 1973-1997. Two such zones are identified under the Aegean area, a large one (Main Aegean Subduction, MAS spanning the whole Hellenic arc and a smaller and younger one under the Western Peloponnesus. The geometry of the MAS suggests that it blocks its own subduction and, therefore, causes the development of the smaller western zone as a result of a step back process in the Pliocene.

  10. Frequent underwater volcanism in the central Aegean Sea

    Huebscher, C.; Ruhnau, M.; Dehghani, G. A.


    The extinction of the Minoan culture in the mid second millennium BCE is a well known consequence of the Plinian eruption of Thera volcano (Santorini Island). Santorini is a member of the South Aegean arc forming a chain from the Gulf of Saronikos (Susaki, Egina, Poros, Methana) at West, to an area close to the Anatolian coast at East (Kos, Nisyros and minor islands), through the central part (Milos and Santorini island groups). Underwater volcanic activity was manifested historically only once. During 1649-1650 CE the Kolumbo underwater volcano evolved about 8 km northeast of Santorini. As a consequence of this eruption volcanic ash covered the entire Aegean area and a hazardous tsunami was triggered. Here we show by means of reflection seismic and magnetic data that underwater volcanism occurred more frequently in the central Aegean Sea than previously assumed. Seismic data show that Kolumbo constitutes of five vertically stacked cones of pyroclastic sediment plus at least four smaller cones on the flank of the volcano. The formation of Kolumbo started synchronous with Santorini Island. The entire volume of the Kolumbo pyroclastic cones is estimated to more than 15 cubic-kilometers. Several small-scale cones have been detected in the Anyhdros Basin some km north-east of Kolumbo, being previously interpreted as mud volcanoes by other authors. However, the similarity of seismic and magnetic signatures of these cones and Kolumbo strongly suggest that these cones were also created by underwater volcanism. Volcanic cones, Kolumbo and Santorini are situated along a NE-SW striking graben system that evolved during five extensional tectonic pulses in the Pliocene.

  11. Offshore wind power in the Aegean Sea

    Hasager, Charlotte Bay; Badger, Merete; Hahmann, Andrea N.

    The wind climate of the Mediterranean Sea has been estimated from atmospheric modelling (Cavaleri 2005, Lavignini et al. 2006) and QuikSCAT (Furevik et al. 2011). The latter shows the Aegean Sea as a promising area for offshore wind power development. According to the Hellenic Wind Energy...... Association (HWEA), the sites of particular interest for offshore wind energy are located close to the mainland and islands in the Aegean Sea. Wind farm developers aim to select local areas with favorable wind conditions to optimize the annual energy production and the economic profit. In the Aegean Sea...

  12. 16ch high-resolution seismic reflection surveys on the active fault of upper fore-arc slope off Okinawa Island, central Ryukyu Island Arc, Southwest Japan

    Arai, K.; Inoue, T.; Sato, T.; Tuzino, T.


    The Ryukyu Island Arc extends from Kyushu to Taiwan, a distance of 1,200 km, along the Ryukyu Trench where the Philippine Sea Plate is subducting beneath the Eurasian Plate. The Okinawa Trough, a back arc basin has formed behind the Ryukyu Island Arc in late Pliocene to early Pleistocene. The research cruises of GH08 (from 28th July to 29th August 2008) and GH09 (from 16th July to 17th August 2009) were carried out around Okinawa Island, which is located on the central Ryukyu Island Arc. More than 4,500 miles multi channel high-resolution seismic profiles were acquired during these two cruises by the GI-gun (355cu. inch) or the Cluster-gun (30+30 cu. inch) systems with 16ch digital streamer cable. Survey area in the southeast off Okinawa Island is located on the upper fore-arc slope. Seismic reflections of the upper fore-arc slope show a distinct reflector which may represent erosional unconformable surface. The distinct reflector had tilted southeastward and was overlain by the stratified sediments. No obvious deformation such as the fold and faults parallel to the Ryukyu Trench axis was found under the upper slope. In contrast, some active faults which were perpendicular to the Ryukyu Trench axis (NW-SE direction) were observed. The most conspicuous normal fault was found on north off Okinawa Island. The fault with 70-80°dipping toward northeast has been active since the early Pleistocene inferred from seismic stratigraphy and calcareous nannofossil biochronology. The maximum displacement reaches to 0.7 s two way travel time in depth. An average of maximum vertical displace component of the normal fault may reach up to ten cm/1000 years. Seismic profiles indicate that the tilting of Ryukyu Island Arc forward to the Ryukyu Trench plays the important role of formation of the fault in a NW-SE direction.

  13. Petrology and tectonics of Phanerozoic continent formation: From island arcs to accretion and continental arc magmatism

    Lee, C.-T.A.; Morton, D.M.; Kistler, R.W.; Baird, A.K.


    Mesozoic continental arcs in the North American Cordillera were examined here to establish a baseline model for Phanerozoic continent formation. We combine new trace-element data on lower crustal xenoliths from the Mesozoic Sierra Nevada Batholith with an extensive grid-based geochemical map of the Peninsular Ranges Batholith, the southern equivalent of the Sierras. Collectively, these observations give a three-dimensional view of the crust, which permits the petrogenesis and tectonics of Phanerozoic crust formation to be linked in space and time. Subduction of the Farallon plate beneath North America during the Triassic to early Cretaceous was characterized by trench retreat and slab rollback because old and cold oceanic lithosphere was being subducted. This generated an extensional subduction zone, which created fringing island arcs just off the Paleozoic continental margin. However, as the age of the Farallon plate at the time of subduction decreased, the extensional environment waned, allowing the fringing island arc to accrete onto the continental margin. With continued subduction, a continental arc was born and a progressively more compressional environment developed as the age of subducting slab continued to young. Refinement into a felsic crust occurred after accretion, that is, during the continental arc stage, wherein a thickened crustal and lithospheric column permitted a longer differentiation column. New basaltic arc magmas underplate and intrude the accreted terrane, suture, and former continental margin. Interaction of these basaltic magmas with pre-existing crust and lithospheric mantle created garnet pyroxenitic mafic cumulates by fractional crystallization at depth as well as gabbroic and garnet pyroxenitic restites at shallower levels by melting of pre-existing lower crust. The complementary felsic plutons formed by these deep-seated differentiation processes rose into the upper crust, stitching together the accreted terrane, suture and former

  14. The importance of shallow hydrothermal island arc systems in ocean biogeochemistry

    Hawkes, Jeffrey A.; Connelly, Douglas P.; Rijkenberg, Micha J. A.; Achterberg, Eric P.


    Hydrothermal venting often occurs at submarine volcanic calderas on island arc chains, typically at shallower depths than mid-ocean ridges. The effect of these systems on ocean biogeochemistry has been under-investigated to date. Here we show that hydrothermal effluent from an island arc caldera was rich in Fe(III) colloids (0.02-0.2 mu m; 46% of total Fe), contributing to a fraction of hydrothermal Fe that was stable in ocean water. Iron(III) colloids from island arc calderas may be transfer...

  15. Making and breaking an island arc: A new perspective from the Oligocene Kyushu-Palau arc, Philippine Sea

    Ishizuka, Osamu; Taylor, Rex N.; Yuasa, Makoto; Ohara, Yasuhiko


    The Kyushu-Palau Ridge (KPR) is a 2600 km long remnant island arc that is separated from the active Izu-Bonin-Mariana (IBM) arc by a series of spreading and rift basins. We present 40Ar/39Ar ages and geochemical data for the entire length of the Kyushu-Palau arc as well as for the conjugate arc which is stranded within the IBM fore arc. New 40Ar/39Ar ages indicate that the KPR was active between 25 and 48 Ma, but the majority of the exposed volcanism occurred in the final phase, between 25 and 28 Ma. Rifting of the Kyushu-Palau arc to form the Shikoku and Parece Vela basins occurred simultaneously along the length of the arc (circa 25 Ma), and at a similar distance from the trench. Unlike the IBM, the KPR has only limited systematic along-arc geochemical trends. Two geochemical components within the KPR indicate an origin in the suprasubduction mantle. First, EM-1-like lavas are identified in a restricted section of the arc, suggesting a localized heterogeneity. Second, EM-2-like arc volcanoes formed on juvenile West Philippine Basin crust, potentially reflecting ingress of mantle from the then active EM-2 province which lies in the west. Another geochemical heterogeneity is found at the KPR-Daito Ridge intersection where the arc developed on preexisting Cretaceous Daito Ridge crust. The geochemical characteristics at this intersection likely result from the involvement of sub-Daito Ridge lithospheric mantle. Subduction flux beneath the KPR generally matches post-45 Ma Eocene/Oligocene lavas in the IBM fore arc, involving fluids and melts derived from altered igneous crust.

  16. Estimation of critical CO2 values when planning the power source in water desalination: The case of the small Aegean islands

    Climate change is one of the most important issues our world faces today and it is responsible for a number of natural disasters that threaten human life and existence. Carbon dioxide, produced from almost every energy consuming activity, is the dominant greenhouse gas responsible for global warming. Water desalination is an energy intensive activity, and when it is powered by conventional energy sources, significant amounts of CO2 are released. For every cubic metre of fresh water produced, there is a 2 kg of CO2 reduction if renewable energy sources (RES) are used instead of electricity from the local grid. On the other hand, the cost of fresh water produced by desalination is much less if conventional sources of energy are used. Making appropriate policy choices require information on both costs and benefits. So here we estimate the critical CO2 cost, above which desalination units should use renewable energy instead of conventional energy sources. It was found that the critical CO2 emissions cost can be close to the CO2 capture cost and in many cases less than the penalties imposed by the European Commission. Several case studies of water desalination in the Aegean islands verify the conclusions.

  17. Brachyopa minima (Diptera: Syrphidae), a new species from Greece with notes on the biodiversity and conservation of the genus Brachyopa Meigen in the Northern Aegean Islands.

    Pérez-Bañón, Celeste; Radenković, Snezana; Vujić, Ante; Petanidou, Theodora


    An on-going study of the hoverfly fauna of the Northern Aegean Islands (Greece) has revealed the presence of four species of the genus Brachyopa Meigen. During the survey the following species were found: B. bicolor (Fallén), B. quadrimaculosa Thompson in Kaplan & Thompson, B. minima Vujić & Pérez-Bañón sp. nov. and an unidentified species very close to B. pilosa (Collin). Morphological characters and mitochondrial COI barcodes were used to link different life stages of B. minima, and to identify a larval specimen of B. bicolor. In this study adult and larval morphology and habitat preferences for B. minima are described. The description of larval morphology of B. bicolor and Brachyopa sp. aff. pilosa is amended too. An identification key to the adults of the B. quadrimaculosa group sensu Kassebeer (2002) in the Eastern Mediterranean (Greece, Israel and Turkey) is provided. The importance of specific microhabitats for the continued existence of these taxa is discussed. PMID:27395920

  18. Mantle dynamics during arc rupture and back-arc opening: Evidence from Tonga, the Lau Basin and the Lau Islands

    The geodynamic interplay between a sub-arc mantle with Pacific and/or Indian MORB-like affinities was first described by Hergt and Hawkesworth in 1994. Following this, a number of workers have recognised similar occurrences of these two domains in other arc/back-arc systems of the western Pacific. Controversy exists concerning the origin of these two mantle components and the extent to which they are geographically distributed. In order to test the geodynamic model proposed by Hergt and Hawkesworth (1994) for Tonga and the Lau Basin, additional samples from this region have been studied. These samples, from the Lau Islands, represent a record of magmatism beginning prior to arc rupture (prior to ∼6 Ma) and extending through to 0.3 Ma ago. Lead isotope composition of basalts from the back-arc sites provided additional insights to the study of this region and suggested the involvement of two mantle source region - similar to those producing basalts at the Pacific and Indian mid-ocean ridges. A new model has been proposed describing the tectonic history involved in the opening of the Lau Basin and using this information to re-examine the lead isotope variations, a new pattern emerges; the initial stages of back-arc formation involved horst and graben style extension of the arc crust, and some magmatism occurred within graben structures

  19. Cycling of sulfur in subduction zones: The geochemistry of sulfur in the Mariana Island Arc and back-arc trough

    Alt, J.C.; Shanks, Wayne C., III; Jackson, M.C.


    The sulfur contents and sulfur isotopic compositions of 24 glassy submarine volcanics from the Mariana Island Arc and back-arc Mariana Trough were determined in order to investigate the hypothesis that subducted seawater sulfur (??34S = 21???) is recycled through arc volcanism. Our results for sulfur are similar to those for subaerial arc volcanics: Mariana Arc glasses are enriched in 34S (??34S = up to 10.3???, mean = 3.8???) and depleted in S (20-290 ppm, mean = 100 ppm) relative to MORB (850 ppm S, ??34S = 0.1 ?? 0.5???). The back-arc trough basalts contain 200-930 ppm S and have ??34S values of 1.1 ?? 0.5???, which overlap those for the arc and MORB. The low sulfur contents of the arc and some of the trough glasses are attributed to (1) early loss of small amounts of sulfur through separation of immiscible sulfide and (2) later vapor-melt equilibrium control of sulfur contents and loss of sulfur in a vapor phase from sulfide-undersaturated melts near the minimum in sulfur solubility at f{hook}O2 ??? NNO (nickel-nickel oxide). Although these processes removed sulfur from the melts their effects on the sulfur isotopic compositions of the melts were minimal. Positive trends of ??34S with 87Sr 86Sr, LILE and LREE contents of the arc volcanics are consistent with a metasomatic seawater sulfur component in the depleted sub-arc mantle source. The lack of a 34S-rich slab signature in the trough lavas may be attributed to equilibration of metasomatic fluid with mantle material along the longer pathway from the slab to the source of the trough volcanics. Sulfur is likely to have been transported into the mantle wedge by metasomatic fluid derived from subducted sediments and pore fluids. Gases extracted from vesicles in arc and back-arc samples are predominantly H2O, with minor CO2 and traces of H2S and SO2. CO2 in the arc and back-arc rocks has ??13C values of -2.1 to -13.1???, similar to MORB. These data suggest that degassing of CO2 could explain the slightly lower

  20. Seismic Reflection Image Across the Izu-Bonin Island Arc System

    Park, J.; Tsuru, T.; Takahashi, N.; Kodaira, S.; Kaneda, Y.


    The Izu-Bonin island arc system occupies almost a northern half of the Izu-Bonin-Island (IBM) arc system extending 2500 km south from near Tokyo, which is one of the largest convergent margins on earth. This Izu-Bonin island arc system is a typical intra-oceanic island arc system involving trench-arc-backarc basin system, i.e., the Izu-Bonin trench, the Izu-Bonin arc, and the backarc Shikoku basin. In order to figure out the past 50 m.y. development history of the entire Izu-Bonin intra-oceanic island arc system, we collected marine multichannel seismic (MCS) reflection data across the island arc system on board the R/V Kairei of the Japan Marine Science and Technology Center (JAMSTEC) in May 2002. We used a ~5-km, 204-channel streamer and a 12,000 cubic inch (~200 L) air-guns array. Receiver spacing was 25-m, yielding 51-fold coverage at 12.5-m CDP spacing. We acquired the MCS data on two different lines: ~560-km-long Line 1 and ~1140-km-long Line 3. The MCS data were migrated in depth domain. Velocity-depth models for the depth migration were iteratively constructed by prestack depth migration velocity analysis. Wide-angle data guided the velocity analysis. In this paper, we show the two MCS profiles and discuss the development process of the Izu-Bonin island arc system from viewpoints of seismic stratigraphy and structure. We identify a clear seismic reflector of the subducting Pacific plate with several horst-and-graben structures, which can be observed beneath the arc more than 60 km landward from the trench axis. Forearc basin is characterized by several buried normal faults and vigorous intra-oceanic sedimentation. In the arc rifting zone, we observe many seismic hyperbolic signatures indicative of active volcanic intrusions, which are related to active magmatism. The topmost sedimentary cover sequences are obviously tilted and cut by many normal faults. It is noticeable that reflectors of the middle crust in the arc-backarc transition zone appear to pinch

  1. Seismic stratigraphy of barrier-island arc retreat paths in Mississippi River delta

    Penland, S.; Suter, J.R.


    The stratigraphic record preserved in the retreat path of Mississippi delta barrier-island arcs is controlled by erosional shoreface retreat processes, relative sea level rise, and sediment supply. More than 500 km (300 mi) of high resolution shallow seismic profiles correlated with vibracores from retreat paths fronting the Isles Dernieres and Chandeleur barrier-island arcs, show contrasting stratigraphic sequences preserved on the inner continental shelf (Mississippian delta). The Isles Dernieres barrier-island arc developed as a consequence of the Caillou Headland abandonment in the early Lafourche delta approximately 800 years B.P. On the lower shoreface, channels can be seen projecting seaward under the central part of the island arc; associated with it is a beach-ridge plain extending eastward. On the inner shelf, a sand sheet up to 60 cm (2 ft) thick marks the retreat path of the Isles Dernieres. The Chandeleur barrier-island arc was generated by abandonment of the St. Bernard delta complex 1,500 years ago. Scattered outcrops of shell reefs and lagoonal deposits occur on the lower shoreface. Beyond the shoreface, a 1 to 5 m (3 to 16 ft) thick sand sheet, caps tidal inlet scars up to 10 m (33 ft) thick, as well as the basal portions of migrating barrier-island sequences associated with earlier shoreline positions. Differences seen in the two stratigraphic sequences are a function of distributary size and depositional history of each barrier-island arc. The Isles Dernieres developed from a series of small sand-deficient distributaries in the Lafourche delta complex, whereas the Chandeleur Islands developed from large sand-rich distributaries of the St. Bernard delta complex.

  2. Costs of Low-Scale Distance Learning Programs: A Case of Distance Learning Courses in the Aegean Islands.

    Costas Tsolakidis


    Full Text Available The advance of Information and Communication Technology (ICT and the reduction of cost in digital applications motivate course designers to develop new application of distance learning programs so as to meet the increasing educational needs in the knowledge-based society. As a consequence, distance learning courses are increasing in number, credibility and acceptability all over the world. The question is whether these programs are efficient in terms of costs. The main theme of this work is to investigate cost behaviour and estimate cost efficiency of distance learning courses applied in low-inhabited, remote islands. The target group consists of high school students of Grade I. The distance learning course that is designed uses several scenarios of the “what-if form” and reaches the conclusion that cost of such solutions is far lower than that of any traditional course, even at the absence of scale economies.

  3. The petrogenesis of sodic island arc magmas at Savo volcano, Solomon Islands

    Smith, D. J.; Petterson, M. G.; Saunders, A. D.; Millar, I. L.; Jenkin, G. R. T.; Toba, T.; Naden, J.; Cook, J. M.


    Savo, Solomon Islands, is a historically active volcano dominated by sodic, alkaline lavas, and pyroclastic rocks with up to 7.5 wt% Na2O, and high Sr, arc-like trace element chemistry. The suite is dominated by mugearites (plagioclase-clinopyroxene-magnetite ± amphibole ± olivine) and trachytes (plagioclase-amphibole-magnetite ± biotite). The presence of hydrous minerals (amphibole, biotite) indicates relatively wet magmas. In such melts, plagioclase is relatively unstable relative to iron oxides and ferromagnesian silicates; it is the latter minerals (particularly hornblende) that dominate cumulate nodules at Savo and drive the chemical differentiation of the suite, with a limited role for plagioclase. This is potentially occurring in a crustal “hot zone”, with major chemical differentiation occurring at depth. Batches of magma ascend periodically, where they are subject to decompression, water saturation and further cooling, resulting in closed-system crystallisation of plagioclase, and ultimately the production of sodic, crystal and feldspar-rich, high-Sr rocks. The sodic and hydrous nature of the parental magmas is interpreted to be the result of partial melting of metasomatised mantle, but radiogenic isotope data (Pb, Sr, Nd) cannot uniquely identify the source of the metasomatic agent.

  4. Eocene volcanism during the incipient stage of Izu–Ogasawara Arc: Geology and petrology of the Mukojima Island Group, the Ogasawara Islands.

    Kanayama, Kyoko; Umino, Susumu; Ishizuka, Osamu


    The Ogasawara Islands mainly comprise Eocene volcanic strata formed when the Izu-Ogasawara-Mariana Arc began. We present the first detailed volcanic geology, petrography and geochemistry of the Mukojima Island Group, northernmost of the Ogasawara Islands, and show that the volcanic stratigraphy consists of arc tholeiitic rocks, ultra-depleted boninite-series rocks, and less-depleted boninitic andesites, which are correlatable to the Maruberiwan, Asahiyama and Mikazukiyama Formations on the Ch...

  5. An updated checklist of poisonous fishes of Turkish Aegean Sea

    Bahar Bayhan; Murat Kaya


    The current status of marine poisonous fish species ranging in the Aegean Sea coastline in Turkey were introduced. Turkey is a peninsula surrounded by seas with different ecological features on three sides. The total length of shoreline is 8 333 km including the islands. The total number of fish species in Turkish seas is 512, of which 449 live in the Aegean Sea followed by the Mediterranean Sea (441 species), the Marmara Sea (257 species) and the Black Sea (154species). O...

  6. Temporal geochemical trends in northern Luzon arc lavas (Philippines): implications on metasomatic processes in the island arc mantle

    Neogene and Quaternary lavas from Batan, Babuyan de Claro, Camiguin and Calayan islands (northern Luzon arc) display temporal increases in incompatible elements including Cs, Rb, Ba, K, La, Ce, Th, U, Ta, Hf and Zr from volcanoes older than 3 Ma to younger ones. These enrichments occur either within a single island (Batan) or within an island group (from Calayan to Camiguin and Babuyan). We show that these enrichments result from incompatible element input into the mantle wedge rather than from partial melting or fractionation effects. The fact that highly incompatible elements display temporal enrichment patterns in Batan lavas whatever their chemical properties indicates that hydrous fluids are not the only metasomatic agents operating in the mantle wedge and that slab-derived melts (adakitic magmas) may also be involved. The coupled temporal variation patterns of large ion lithophile elements and Sr-Nd isotopes suggest that the metasomatic budgets beneath the southern group of islands are mainly controlled by hydrous fluids inputs. In contrast, young Batan lavas likely derive from a mantle source mostly metasomatized by adakitic magmas. (authors)

  7. Seismological, Geological and Geomorphic Aspects of Arc Segmentation and Their Relation to Subducting Bathymetric Features in the Solomon Island Arc, SW Pacific Ocean

    Chen, M.; Frohlich, C.; Taylor, F. W.


    Arc segmentation partitions forearcs into multiple blocks so that the forearc behaves like a "keyboard on a piano" as each segment potentially interacts with the downgoing plate in a different tectonic style. For example, parts of the forearc of the Solomon Islands arc has undergone hundreds of meters of rapid subsidence and uplift during late Quaternary time. Other parts have undergone only minor late Quaternary movements. We use seismology, geology, and geomorphology to identify arc segments in order to evaluate how bathymetric features on the subducting plate influence seismicity and active tectonics and cause overriding plate segmentation. Seismic rupture areas for large earthquakes, seismicity patterns, seismicity cross sections, focal mechanisms, and seismic moment calculations all reveal that the central arc being underthrust by the Woodlark Basin system of active sea-floor spreading is very different from the northwest and southeast parts of the arc. Woodlark subduction is characterized by sparse seismicity, gentle subduction angle, and thrust faulting with some normal and strike-slip components. Observations from geologic maps, coastal geomorphology, and emerged coral reefs show that the arc segments are undergoing varying amounts and rates of uplift and submergence. Larger islands such as Guadalcanal and San Cristobal have both drowning and emerging coastlines. This information indicates the individual segments have dramatically different histories of vertical tectonics. We identify three supersegments: Bougainville, New Georgia, and Guadalcanal-San Cristobal. Smaller segments subdivide each supersegment. Thus we identify nine major boundaries, seven minor boundaries, and six possible boundaries. The classification of each boundary depends on the strength of evidence supporting its existence and the amount of change in tectonic behavior across the boundary. We speculate that subduction of the young Woodlark Spreading Center with seamounts and ridges on

  8. Deformation of island-arc lithosphere due to steady plate subduction

    Fukahata, Yukitoshi; Matsu'ura, Mitsuhiro


    Steady plate subduction elastically brings about permanent lithospheric deformation in island arcs, though this effect has been neglected in most studies based on elastic dislocation theory. We investigate the characteristics of the permanent lithospheric deformation using a kinematic model, in which steady slip motion is given along a plate interface in the elastic lithosphere overlying the viscoelastic asthenosphere under gravity. As a rule of thumb, long-term lithospheric deformation can be understood as a bending of an elastic plate floating on non-viscous fluid, because the asthenosphere behaves like water on the long term. The steady slip below the lithosphere-asthenosphere boundary does not contribute to long-term lithospheric deformation. Hence, the key parameters that control the lithospheric deformation are only the thickness of the lithosphere and the geometry of the plate interface. Slip on a plate interface generally causes substantial vertical displacement, and gravity always tries to retrieve the original gravitational equilibrium. For a curved plate interface gravity causes convex upward bending of the island-arc lithosphere, while for a planar plate interface gravity causes convex downward bending. Larger curvature and thicker lithosphere generally results in larger deformation. When the curvature changes along the plate interface, internal deformation is also involved intrinsically, which modifies the deformation field due to gravity. Because the plate interface generally has some curvature, at least near the trench, convex upward bending of the island-arc lithosphere, which involves uplift of island-arc and subsidence around the trench, is always realized. On the other hand, the deformation field of the island-arc lithosphere sensitively depends on lithospheric thickness and plate interface geometry. These characteristics obtained by the numerical simulation are consistent with observed topography and free-air gravity anomalies in subduction

  9. Eocene to Miocene back-arc basin basalts and associated island arc tholeiites from northern Sulawesi (Indonesia): Implications for the geodynamic evolution of the Celebes basin

    Eocene BABB basalts intruded by tholeiitic and calk-alkalic island arc magmatic rocks are reported from the north arm of Sulawesi (Indonesia). Age and geochemical similarities between these basalts and those drilled in the Celebes Sea indicate this North Sulawesi volcanic arc was built on the same oceanic crust. The 25 deg late Neogene clockwise rotation of the north arm of Sulawesi following its collision with fragments of Australia (Sula, Buton) is not sufficient to explain the asymmetrical magnetic anomalies in the Celebes basin. The North Sulawesi island arc could be interpreted as having progressively retreated northward on its own Celebes sea back arc basin, during an episode of Palaeogene-early Neogene tectonic erosion along the trench. (authors)

  10. Subduction Controls of Hf and Nd Isotopes in Lavas of the Aleutian Island Arc

    Yogodzinski, Gene; Vervoort, Jeffery; Brown, Shaun Tyler; Gerseny, Megan


    The Hf and Nd isotopic compositions of 71 Quaternary lavas collected from locations along the full length of the Aleutian island arc are used to constrain the sources of Aleutian magmas and to provide insight into the geochemical behavior of Nd and Hf and related elements in the Aleutian subduction-magmatic system. Isotopic compositions of Aleutian lavas fall approximately at the center of, and form a trend parallel to, the terrestrial Hf-Nd isotopic array with {var_epsilon}{sub Hf} of +12.0 to +15.5 and {var_epsilon}{sub Nd} of +6.5 to +10.5. Basalts, andesites, and dacites within volcanic centers or in nearby volcanoes generally all have similar isotopic compositions, indicating that there is little measurable effect of crustal or other lithospheric assimilation within the volcanic plumbing systems of Aleutian volcanoes. Hafnium isotopic compositions have a clear pattern of along-arc increase that is continuous from the eastern-most locations near Cold Bay to Piip Seamount in the western-most part of the arc. This pattern is interpreted to reflect a westward decrease in the subducted sediment component present in Aleutian lavas, reflecting progressively lower rates of subduction westward as well as decreasing availability of trench sediment. Binary bulk mixing models (sediment + peridotite) demonstrate that 1-2% of the Hf in Aleutian lavas is derived from subducted sediment, indicating that Hf is mobilized out of the subducted sediment with an efficiency that is similar to that of Sr, Pb and Nd. Low published solubility for Hf and Nd in aqueous subduction fluids lead us to conclude that these elements are mobilized out of the subducted component and transferred to the mantle wedge as bulk sediment or as a silicate melt. Neodymium isotopes also generally increase from east to west, but the pattern is absent in the eastern third of the arc, where the sediment flux is high and increases from east to west, due to the presence of abundant terrigenous sediment in the

  11. Crustal structure of Guadeloupe Islands and the Lesser Antilles Arc from a new gravity and magnetic synthesis

    Gailler, Lydie; Bouchot, Vincent; Martelet, Guillaume; Thinon, Isabelle; Lebrun, Jean-Frédéric; Münch, Philippe


    Guadeloupe Island (West French Indies) is one of the twenty islands that compose the Lesser Antilles Arc, which results from the subduction of the Atlantic Ocean plate beneath the Caribbean one. The island lies in a complex volcano-tectonic system and the need to understand its geological context has led to numerous on- and offshore geophysical investigations. This work presents the compilation and processing of available, on-land, airborne and marine, gravity and magnetic data acquired durin...

  12. Heterogeneous stress state of island arc crust in northeastern Japan affected by hot mantle fingers

    Shibazaki, Bunichiro; Okada, Tomomi; Muto, Jun; Matsumoto, Takumi; Yoshida, Takeyoshi; Yoshida, Keisuke


    By considering a thermal structure based on dense geothermal observations, we model the stress state of the crust beneath the northeastern Japan island arc under a compressional tectonic regime using a finite element method with viscoelasticity and elastoplasticity. We consider a three-layer structure (upper crust, lower crust, and uppermost mantle) to define flow properties. Numerical results show that the brittle-viscous transition becomes shallower beneath the Ou Backbone Range compared with areas near the margins of the Pacific Ocean and the Japan Sea. Moreover, several elongate regions with a shallow brittle-viscous transition are oriented transverse to the arc, and these regions correspond to hot fingers (i.e., high-temperature regions in the mantle wedge). The stress level is low in these regions due to viscous deformation. Areas of seismicity roughly correspond to zones of stress accumulation where many intraplate earthquakes occur. Our model produces regions with high uplift rates that largely coincide with regions of high elevation (e.g., the Ou Backbone Range). The stress state, fault development, and uplift around the Ou Backbone Range can all be explained by our model. The results also suggest the existence of low-viscosity regions corresponding to hot fingers in the island arc crust. These low-viscosity regions have possibly affected viscous relaxation processes following the 2011 Tohoku-oki earthquake.

  13. The Aegean: A natural laboratory for tectonics

    The Aegean, a young and active tectonic region, is a natural laboratory for analyzing many tectonic processes that occur in backarc extensional regimes, and the correlation of these processes from landscape development to deeper mantle dynamics. Cenozoic development of the Aegean region was dominated by subduction beneath Europe and coeval upper plate extension modified by westward extrusion of Anatolia. Intraorogenic and backarc extension began during early Cenozoic time within the Balkans and NW Turkey during closure of the Vardar ocean. Extension was manifested by core complex formation and a change in volcanism caused by the evolution of the lithosphere and mantle wedge. Following a short period of local (?) shortening in ∼ early Miocene time, regional extension began and continued to the present. Within the Hellenides, E-W extension and the subduction zone migrated westward as thick and thin crustal units were progressively accreted and were complexly rotated up to 400 CW. Within the eastern Balkans and NW Turkey, N-S extension migrated westward and southward, and in the Aegean the volcanic arc and subduction zone migrated southward. Turkish crustal elements rotated complexly CCW, which in concert with the CW rotation in the Hellenides increased the curvature of the subduction zone and lengthened the orogen causing greater subsidence and extension in the Aegean Sea. Westward extrusion of Anatolia from the Arabian collision zone was enhanced by slab roll back in west moving Aegean crust more rapidly westward. Abundant evidence supports slab rollback at different velocities along the subduction zone. In Pliocene time, the North Anatolian fault crossed the Hellenides in a complex transtensional zone and a diffuse zone of left-lateral shear crossed western Turkey at present isolating a relatively undeforming Aegean plate. Major tectonic questions include: What is the geometry and fate of subducted slabs?, How much crust is accreted during subduction of thick and

  14. Andaman-Sumatra island arc: III. Time evolution of seismogenic activation of the arc since the beginning of the 21st century

    Balakina, L. M.; Moskvina, A. G.


    The spatiotemporal evolution of the intense burst in seismogenesis within the Andaman-Sumatra island arc in 2000-2010 is analyzed. The onset of seismogenic activation was marked by two strong ( M S ˜ 7.9, M S ˜ 7.8) quakes that occurred in the lithosphere of the South Sumatra region on June 4, 2000 and by the strongest ( M W = 7.3) earthquake of July 25, 2004 that took place in the lower part of the focal zone. These seismic events were the foreshocks of the main episode of seismogenic activation of the island arc—the catastrophic earthquake of December 26, 2004, with its source near the northern coast of Sumatra. The large shocks ( M S ˜ 7.7-8.4) that occurred from March 28, 2005 to October 25, 2010 between the source of the Sumatran earthquake and epicentral zone of the foreshocks of June 4, 2000, are the aftershocks of the Sumatran event. The spatiotemporal evolution of seismogenic activation of the Andaman-Sumatra island arc at the beginning of the 21st century is compared to the seismogenic activation of the Kuril-Kamchatka arc in the middle of the 20th century. The positions, geological conditions, and focal parameters of the strongest Sumatran earthquakes of 2000-2010 are determined. The interpretation of the sources relies on the (1) complex analysis of all the manifestations of the earthquakes of 2000-2010 and (2) the established regularities of the occurrence of the earthquakes in the island arcs. The sources of the earthquakes of 2005-2010 are the steep longitudinal (trending along the arc) reverse faults of a backthrust type, which have a bedding depth of about a few dozen kilometers. The reverse-fault sources of the earthquakes of March 28, 2005, September 12, 2007 (11:10 UT), and October 10, 2010 are located in the zone of the Outer Range, and the earthquakes of September 12, 2007 (23:49 UT) fall in the Mentawai Trough. The strike-slip reverse fault, which cuts the island arc, is likely to be the focal mechanism of the earthquake of June 4, 2000

  15. Arc lavas on both sides of a trench: Slab window effects at the Solomon Islands triple junction, SW Pacific

    Chadwick, John; Perfit, Michael; McInnes, Brent; Kamenov, George; Plank, Terry; Jonasson, Ian; Chadwick, Claire


    The Woodlark Spreading Center (WSC) is subducted at the San Cristobal trench, forming a triple junction at the New Georgia Group (NGG) arc in the Solomon Islands. WSC lavas are N-MORB at > 100 km from the trench, but with decreasing distance they have increasingly arc-like Sr-Nd-Pb isotopic ratios, enrichments in Rb > K > Pb > Sr, and depletions in HFSE and Y. Within 50 km of the trench on the Simbo and Ghizo Ridges, many recovered samples are island arc tholeiites to medium-K calc-alkaline andesites and dacites, and many have the same or similar major and trace element and isotopic characteristics as true arc lavas in the NGG on the other side of the trench. Previous investigations have concluded that these WSC lavas are the result of relic back arc mantle enrichments resulting from subduction of the Pacific plate prior to the late Miocene at the North Solomon trench, > 200 km to the north. However, the high-silica WSC lavas are more arc-like than those recovered from other distal back arcs, and are more voluminous, forming large submarine ridges and stratovolcanoes. We suggest that true arc mantle migrates across the plate boundary from the adjacent NGG arc through slab windows created by the subduction of the WSC. This leads to variable mixing between NGG arc and WSC N-MORB end-members, forming the transitional lavas recovered from the WSC. Lavas with similar arc-like characteristics have previously been recovered on the Chile Rise near where it is subducted at the Chile Trench, raising the possibility that such mantle transfer is a common phenomenon where active spreading centers are subducted. The presence of slab windows may also be responsible for the unusual forearc volcanism in the NGG, and melting of slab window margins may account for the presence of high-silica adakite-like lavas on the WSC.

  16. Island-Arc Collision Dominates Japan's Sediment Flux to the Pacific Ocean

    Codilean, A. T.; Korup, O.; Hayakawa, Y. S.; Matsushi, Y.; Saito, H.; Matsuzaki, H.


    Quantifying volumes and rates of delivery of terrestrial sediment to subduction zones is indispensable for refining estimates of the thickness of trench fills that may eventually control the location and timing of submarine landslides and tsunami-generating mega-earthquakes. Despite these motivating insights, knowledge about the rates of erosion and sediment export from the Japanese islands to their Pacific subduction zones has somewhat stagnated despite the increasing availability of highly resolved data on surface deformation, climate, geology, and topography. Traditionally, natural erosion rates across the island arc have been estimated from catchment topographic predictors of reservoir sedimentation rates that were recorded over several years to decades. We correct for a systematic bias in these predictions, and present new estimates of decadal to millennial-scale erosion rates of the Japanese terrestrial inner forearc, drawing on several unprecedented inventories of mass wasting, reservoir sedimentation, and concentrations of cosmogenic 10Be in river sands. Our data reveal that catchments draining Japan's eastern seaboard have distinctly different tectonic, lithological, topographic, and climatic characteristics, underscored by a marked asymmetric pattern of erosion rates along and across the island arc. Erosion rates are highest in the Japanese Alps that mark the collision of two subduction zones, where high topographic relief, hillslope and bedrock-channel steepness foster rapid denudation by mass wasting. Comparable, if slightly lower, rates characterize southwest Japan, most likely due to higher typhoon-driven rainfall totals and variability rather than the similarly high relief and contemporary uplift rates that are linked to subduction earthquake cycles, and outpace long-term Quaternary uplift. In contrast, our estimated erosion and flux rates are lowest in the inner forearc catchments that feed sediment into the Japan Trench. We conclude that

  17. Tectonic implications of spatial variation of b-values and heat flow in the Aegean region

    Kalyoncuoglu, U. Yalcin; Elitok, Ömer; Dolmaz, M. Nuri


    The Aegean region is tectonically a complex area characterized mainly by the subduction of African oceanic lithosphere beneath the Aegean continental lithosphere including extensional subbasins and mantle driven block rotations. In this study, spatial distribution of earthquakes, b-value distribution, and heat flow data have been analyzed to reveal the deep structural features of the Aegean region. b-value distributions show two low NE-SW and NW-SE trending b-anomaly zones in the western and eastern side of the Crete, implying slab tear within the Aegean slab. Earthquake foci distribution indicates that the Aegean slab steepens in the eastern side of the Crete, compared to its western side. Earthquake foci reach maximum depth of 180 km along the Cycladic arc axis, suggesting northward subducted slab geometry. The low seismic activities and high b-value anomalies within Aegean basin, except North Aegean Trough, can be compared to higher heat flow. We concluded that collision-induced westward mantle flow beneath Turkey followed by hard collision between Arabian-Eurasian continental plates played a major role in the evolution of clockwise rotational retreat of the Aegean slab and slab steepening to the east of the Crete.

  18. On the time-scales of magmatism at island-arc volcanoes.

    Turner, S P


    Precise information on time-scales and rates of change is fundamental to an understanding of natural processes and the development of quantitative physical models in the Earth sciences. U-series isotope studies are revolutionizing this field by providing time information in the range 10(2)-10(4) years, which is similar to that of many modern Earth processes. I review how the application of U-series isotopes has been used to constrain the time-scales of magma formation, ascent and storage beneath island-arc volcanoes. Different elements are distilled-off the subducting plate at different times and in different places. Contributions from subducted sediments to island-arc lava sources appear to occur some 350 kyr to 4 Myr prior to eruption. Fluid release from the subducting oceanic crust into the mantle wedge may be a multi-stage process and occurs over a period ranging from a few hundred kyr to less than one kyr prior to eruption. This implies that dehydration commences prior to the initiation of partial melting within the mantle wedge, which is consistent with recent evidence that the onset of melting is controlled by an isotherm and thus the thermal structure within the wedge. U-Pa disequilibria appear to require a component of decompression melting, possibly due to the development of gravitational instabilities. The preservation of large (226)Ra disequilibria permits only a short period of time between fluid addition and eruption. This requires rapid melt segregation, magma ascent by channelled flow and minimal residence time within the lithosphere. The evolution from basalt to basaltic andesite probably occurs rapidly during ascent or in magma reservoirs inferred from some geophysical data to lie within the lithospheric mantle. The flux across the Moho is broadly andesitic, and some magmas subsequently stall in more shallow crustal-level magma chambers, where they evolve to more differentiated compositions on time-scales of a few thousand years or less. PMID

  19. Do fluid inclusions preserve δ18O values of hydrothermal fluids in epithermal systems over geological time? : evidence from paleo- and modern geothermal systems, Milos island, Aegean Sea

    Naden, Jonathan; Kilias, S.P.; M. J. Leng; Cheliotis, I.; Shepherd, T.J.


    Stable isotope compositions of quartz (δ18Oquartz) and fluid inclusion waters (δ18OFI and δDFI) were analysed from Profitis Ilias, a low-sulphidation epithermal gold mineralisation deposit on Milos island Greece, to establish if δ18OFI preserve a record of paleo-geothermal processes. Previous studies show that mineralisation at Profitis Ilias resulted from extreme boiling and vaporisation and a zone located at approximately 430 m asl represents the transition between a liquid- and vapour-dom...

  20. Geochemical characteristics of island-arc volcanic rocks in the Nan-Nam Pat-Phetchabun zone, northern Thailand

    SHEN Shangyue; FENG Qinglai; YANG Wenqiang; ZHANG Zhibin; Chongpom Chonglakmani


    Late Permian-Early Triassic (P2-T1) volcanic rocks distributed on the eastern side of ocean-ridge and oceanic-island basalts in the Nan-Uttaradit zone were analyzed from aspects of petrographic characteristics, rock assemblage, REE, trace elements, geotectonic setting, etc., indicating that those volcanic rocks possess the characteristic features of island-arc volcanic rocks. The volcanic rock assemblage is basalt-basaltic andesite-andesite. The volcanic rocks are sub-alkaline, dominated by calc-alkaline series, with tholeiite series coming next. The chemical composition of the volcanic rocks is characterized by low TiO2 and K2O and high Al2O3 and Na2O. Their REE patterns are of the flat, weak LREE-enrichment right-inclined type. The trace elements are characterized by the enrichment of large cation elements such as K, Rb and Ba, common enrichment of U and Th, and depletion of Nb, Ta, Zr and Hf. The petrochemical plot falls within the field of volcanic rocks, in consistency with the plot of island-arc volcanic rocks in the Jinsha River zone of China. This island-arc volcanic zone, together with the ocean-ridge/oceanic island type volcanic rocks in the Nan-Uttaradit zone, constitutes the ocean-ridge volcanic rock-island-arc magmatic rock zones which are distributed in pairs, indicating that the oceanic crust of the Nan-Uttaradit zone once was of eastward subduction. This work is of great significance in exploring the evolution of paleo-Tethys in the Nan-Uttaradit zone.

  1. Seasonal and vertical variations of phytoplankton composition in Marine Park of Gökçeada Island in the North Aegean Sea

    Güreşen, Aysu; Turan, Yelda Aktan


    Abstract This study was conducted to understand the seasonal and vertical variations in the composition and abundance of phytoplankton assemblages in the Marine Park of Gökçeada Island and to evaluate the relations of phytoplankton community structure with the environmental parameters. Water samples were taken from the water column at surface water, 10 m, 20 m and 28 m depths in Yıldız Bay seasonally between May 2009 and January 2010. A total of 28 species belonging to Bacillariophyceae (61%)...

  2. An updated checklist of poisonous ifshes of Turkish Aegean Sea

    Bahar Bayhan; Murat Kaya


    The current status of marine poisonous fish species ranging in the Aegean Sea coastline in Turkey were introduced. Turkey is a peninsula surrounded by seas with different ecological features on three sides. The total length of shoreline is 8 333 km including the islands. The total number of fish species in Turkish seas is 512, of which 449 live in the Aegean Sea followed by the Mediterranean Sea (441 species), the Marmara Sea (257 species) and the Black Sea (154species). On the Aegean Sea coasts, the richest sea regarding fish diversity, the number of poisonous fish species is also high. This mini-review revealed 51 poisonous fish species belonging to 14 families in the Turkish Aegean Sea. On the Aegean Sea coasts poisonous fish species can be categorized into three groups: (i) Fish that contain venomous spines on the tail or on the operculum (ii) Fish that carry poisonous bite and (iii) Fish having poisonous flesh or liver. Poisoning fish that contain venomous spines on the tail or on the operculum mostly are dangerous because of their poisonous thorns whereas the passive poisonous fish species poison when they are eaten. These toxins can cause morbidity and rarely, mortality in humans. Apart from these, swallowing the blood of species such as European eelAnguilla anguillaand European congerConger congermight also cause poisoning. Besides, as there has been an invasion of puffer fish especially on the Turkish Mediterranean and Aegean coasts in recent years, there is a danger in question. Thus, it is very important to particularly draw attention to these fish on the Turkish coasts.

  3. The Permian Dongfanghong island-arc gabbro of the Wandashan Orogen, NE China: Implications for Paleo-Pacific subduction

    Sun, Ming-Dao; Xu, Yi-Gang; Wilde, Simon A.; Chen, Han-Lin; Yang, Shu-Feng


    The Dongfanghong hornblende gabbro is located in the western part of the Wandashan Orogen and to the east of the Jiamusi Block in NE China. It was emplaced into Early Paleozoic oceanic crust (i.e. Dongfanghong ophiolite) at ~ 275 Ma and both later collided with the eastern margin of the Jiamusi Block. The Dongfanghong gabbro is sub-alkaline with high Na2O contents and is characterized by enrichment in light rare earth elements (LREE), large ion lithosphile elements (LILE), Sr, Eu, and Ba, and depletion in high field strength elements (HFSE). The enriched isotopic signatures (87Sr/86Sri = ~ 0.7065, εNd(t) = ~- 0.5, 208Pb/204Pbi = ~ 38.05, 207Pb/204Pbi = ~ 15.56, 206Pb/204Pbi = ~ 18.20 and zircon εHf(t) = ~+ 5.8) indicate an enriched mantle (EM2) source, with some addition of continental material. It has arc geochemical affinities similar to Permian arc igneous rocks in the eastern margin of the Jiamusi Block, the Yakuno Ophiolite in SW Japan, arc rocks along the western margin of the North America Craton, and also the Gympie Group in eastern Australia. All these features, together with information from tectonic discrimination diagrams, suggest that the Dongfanghong gabbro formed in an immature island arc. The spatial configuration of ~ 290 Ma immature continental arc rocks in the eastern part of the Jiamusi Block and the ~ 275 Ma immature island arc Dongfanghong gabbro in the Wandashan Orogen to the east is best explained by eastward arc retreat and slab roll-back of the Paleo-Pacific Plate. This model is also supported by the Carboniferous-Permian stratigraphic transition in the Jiamusi Block from oceanic carbonate rocks to coal-bearing terrestrial clastic rocks and andesites. We thus suggest that both Paleo-Pacific subduction and roll-back occurred in the Early Permian along the eastern margin of Asia.

  4. Using helium and carbon(CO2)isotopes to distinguish between source and crustal contribution in arc magmas. A case study from the Lesser Antilles island arc

    A quantitative assessment of the fate of sediments at subduction zones is a vital component in understanding then cycling history between the mantle and the exosphere. Coupling helium isotope (3He/4He) investigations with a tracer of sediment type - such as carbon isotopes (13C)- offers the additional possibility of identifying the nature of the subducted sedimentary component (marine versus terrigenous sediments for example). A regional survey of the helium and carbon isotope geochemistry of the Lesser Antilles volcanic arc was undertaken. Both geothermal fluids (fumaroles and hot springs) and young phenocryst-bearing lavas were analysed to establish helium and carbon relations along the arc. The northern group of islands appears to be characterised by a mixture of MORB with subducted slab component while the southern group has a clear signature of crustal contamination: however in this case the CO2/3He ratios indicate a possible third component

  5. Interplay between active and past tectonics in the Hellenic Arc (Greece): Geological and geomorphic evidences from Kythira Island

    Fernández-Blanco, David; de Gelder, Gino; Delorme, Arthur; Lacassin, Robin; Armijo, Rolando


    The Hellenic Arc undergoes the largest convergence velocity and highest seismic activity among Mediterranean subduction systems. The outer-arc high islands of the Hellenic Arc are thus key to understand the mode of deformation of the crust during subduction and the mechanisms behind vertical motions at the front of overriding plates, here and elsewhere. Kythira Island, located between SW Peloponnese and NE Crete, provides an exceptional opportunity to understand the interaction between past and active tectonics in the Hellenic Arc. The recent uplift of the Kythira Island is marked in its landscape as paleosurfaces, marine terraces, abandon valleys and gorges. Together with the sedimentary record of the island and its geologic structures, we attempt to reconstruct its tectonic evolution since the latest Miocene. Here, we present exceptionally detailed geological and geomorphological maps of the Kythira Island based on fieldwork, Pleiades satellite imagery and 2-m resolution DEM, as well as the analyses of marine terraces and river network morphometrics. Pliocene or younger infill sequences rest atop of Palaeocene or older rocks in several marine basins in the island. In the largest marine basin, we found a stratigraphic sequence with a (tilted) continental conglomerate at the base, passing upwards to a disconformal subhorizontal conglomerate, calcarenites and fine sands, and terminating with a marine conglomerate. This marine conglomerate acts as a "cap rock" that marks the topography and shapes the highermost, and most extensive, low-relief surface. Overall, the infill sequence onlaps basement with the exception of the western margin where normal faults partly controlled the deposition of its lower sector. These faults reactivated older Hellenic fold-and-thrust structures, parallel to the subduction trench, and were not active during the maximum marine transgression that led to the deposition of the subhorizontal part of the infill sequence, including the topmost

  6. Ophiolite emplacement by collision between the Sula Platform and the Sulawesi Island Arc, Indonesia

    Silver, Eli A.; McCaffrey, Robert; Joyodiwiryo, Yoko; Stevens, Scott


    Much of the tectonic complexity displayed in eastern Indonesia results from a series of Neogene collision events between island arcs, continental fragments, and the Australian continent. Here we examine the emplacement of a large ophiolite belt, resulting from the Miocene collision between the Sulawesi island arc and a continental fragment, the Sula platform. We present the results of several marine geophysical expeditions to the SW Molucca Sea and the NW Banda Sea, plus gravity and geology on the east arms of Sulawesi. The Batui thrust separates the ophiolite from sedimentary rocks deformed along the leading edge of the Sula platform. We mapped this thrust eastward from Sulawesi along the southern margin of the Gorontalo basin. The latter is floored by oceanic crust, and its south edge is uplifted against the thrust. Thus the Sulawesi ophiolite can be traced offshore to its origin as basement of the Gorontalo basin. The ophiolite is composed of harzburgite in the Southeast Arm and passes upward through a complex of gabbros and diabase dikes in the East Arm. Ophiolite melange underlies the harzburgites on the Southeast Arm beneath low-angle thrust contacts where seen. Our local observations show the melange to be composed of thrust packets of both serpentine and red shale matrix varieties. The packets are several hundred meters thick, and the melange, where studied, has a moderate north to northeast dipping foliation. This orientation, if regionally representative of the melange fabric, is consistent with a significant northward component of movement of the lower plate, probably the Sula platform or its margin. Where the ophiolite is in contact with rocks of the central schist belt, it dips under the schist, but where it encounters melange, or Mesozoic or Paleogene sedimentary rocks, the ophiolite is thrust over them. The tectonic overlap sequence, from west to east, is schist over ophiolite over older sediments or melange. The ophiolite appears to have been

  7. Temporal evolution of island arc magmatism: geochronology, petrology et geochemistry of mesozoic and cenozoic magmatic rocks from Sumatra (Indonesia)

    Sumatra island (Western Indonesia) belongs to the Sunda magmatic arc, which results from the subduction of the Indian ocean plate beneath the margin of the Eurasiatic continental block. Plutonic and volcanic rocks of Mesozoic and Cenozoic ages are very abundant in Sumatra, where they mainly outcrop in a NNW-SSE trending, 1,650 km-long stripe in the western part of the island. The spatial and temporal distributions of magmatic rocks in Sumatra were not previously investigated in detail. We have performed 175 40K-40Ar datings on bulk rocks and minerals separated from samples which have also been analysed for major and trace elements by ICP-AES. These results allow to discuss the distribution of magmatic events in space of a long subduction period on the chemical composition of the Sunda arc mantle wedge. (author)

  8. ArcInfo GRID format of the 2004 Multibeam Backscatter Data in the Northeastern Channel Islands Region, Southern California [

    U.S. Geological Survey, Department of the Interior — ArcInfo GRID format data generated from the 2004 multibeam sonar survey of the Northeastern Channel Islands, CA Region. The data include high-resolution, acoustic,...

  9. ArcInfo GRID format of the 2004 Multibeam Bathymetry Data in the Northeastern Channel Islands Region, Southern California [

    U.S. Geological Survey, Department of the Interior — ArcInfo GRID format data generated from the 2004 multibeam sonar survey of the Northeastern Channel Islands, CA Region. The data include high- resolution bathymetry.

  10. Hf-Nd-Sr isotopes and incompatible element abundances in island arcs: Implications for magma origins and crust-mantle evolution

    We present Hf, Nd and Sr isotopic data and abundances of K, Rb, Cs, Ba, Sr, Hf and REE for 32 samples from seven intra-oceanic island arcs. Samples from the Marianas, Izu, Aleutian and New Britain arcs have tightly grouped 176Hf/177Hfproportional0.28320, 143Nd/144Ndproportional0.51303 and 87Sr/86Srproportional0.7035 close to, but distinct from, mid-ocean ridge basalts (MORB) for 143Nd/144Nd and 87Sr/86Sr. In contrast, samples from the Sunda, Banda and Lesser Antilles arcs are much more variable towards lower 176Hf/177Hf and 143Nd/144Nd, and higher 87Sr/86Sr. Isotopically, island arcs on the whole are closely similar to ocean islands. Some commonly-occurring features of the trace element geochemistry of island arcs are apparent in our data: alkali and alkaline-earth elements, particularly Cs, have high abundance relative to LREE compared to oceanic basalts; negative Ce anomalies occur in six out of seven arcs. However, Hf does not appear underabundant relative to REE. The isotopic data require a continental component in all island arcs, in addition to probable mantle and oceanic crust contributions, even for the arcs with isotope ratios close to MORB. In the absence of continental crust, we can best explain this component by subducted pelagic sediment in the arc magma source region. The involvement of sediments in all arcs implies that there is an inherent recycling of older continent to island arcs, and potentially to new continent, of at least 1%. Conservative calculations show that the upper subducted slab (basalt + sediment) passes beyond the arc magma genesis zone and enters the deep mantle with a minimum of 500-1000 ppm K, and corresponding amounts of other incompatible elements. If this material is not completely homogenized with the mantle and later becomes part of the source of ocean island magmas, then the ocean island-island arc isotopic similarity is a result of their similar mix of source materials-mantle peridotite with trace element signatures from

  11. Focal mechanisms in the southern Aegean from temporary seismic networks – implications for the regional stress field and ongoing deformation processes

    W. Friederich


    Full Text Available The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earthquakes fall into 16 distinct spatial clusters distributed over the southern Aegean region. For each cluster, a stress inversion could be carried out yielding consistent estimates of the stress field and its spatial variation. At crustal levels, the stress field is generally dominated by a steeply dipping compressional principal stress direction except in places where coupling of the subducting slab and overlying plate come into play. Tensional principal stresses are generally subhorizontal. Just behind the forearc, the crust is under arc-parallel tension whereas in the volcanic areas around Kos, Columbo and Astypalea tensional and intermediate stresses are nearly degenerate. Further west and north, in the Santorini–Amorgos graben and in the area of the islands of Mykonos, Andros and Tinos, tensional stresses are significant and point around the NW–SE direction. Very similar stress fields are observed in western Turkey with the tensional axis rotated to NNE–SSW. Intermediate-depth earthquakes below 100 km in the Nisyros region indicate that the Hellenic slab experiences slab-parallel tension at these depths. The direction of tension is close to east–west and thus deviates from the local NW-oriented slab dip presumably owing to the segmentation of the slab. Beneath the Cretan sea, at shallower levels, the slab is under NW–SE compression. Tensional principal stresses in the crust exhibit very good alignment with extensional strain rate principal axes derived from GPS velocities except

  12. CRED 5 m Gridded bathymetry of Jarvis Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (5 m cell size) bathymetry of the shelf and slope environments of Jarvis Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  13. CRED 40 m Gridded bathymetry of Howland Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (40 m cell size) bathymetry of the shelf and slope environments of Howland Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  14. CRED 5 m Gridded bathymetry of Howland Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (5 m cell size) bathymetry of the shelf and slope environments of Howland Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  15. CRED 20 m Gridded bathymetry of Jarvis Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (20 m cell size) bathymetry of the shelf and slope environments of Jarvis Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  16. CRED 40 m Gridded bathymetry of Baker Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (40 m cell size) bathymetry of the shelf and slope environments of Baker Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  17. Geochemistry of oceanic igneous rocks - Ridges, islands, and arcs - With emphasis on manganese, scandium, and vanadium

    Doe, B.R.


    increasing Mn is an indication of titanomagnetite removal. Dual compatible and incompatible trends with differentiation are found chiefly for Cu, Sc, and Sr. Distinguishing mid-ocean ridge basalts (MORB), oceanic-island volcanic rocks (OIV), and island-arc volcanic rocks (IAV) may be accomplished by plots of Ce/Yb versus Ba/Ce, where OIV plot to higher values of Ce/Yb than do MORB, and IAV data plot to higher values of Ba/Ce than do those of MORB. These ratios do not seem to be significantly affected by submarine weathering.

  18. Magnetization strucrure of thermal vent on island arc from vector magnetic anomlies using AUV

    Isezaki, N.; Matsuo, J.; Sayanagi, K.


    The geomagnetic anomaly measured by a scalar magnetometer,such as a proton precession magnetometer cannot be defined its direction, then it does not satisfy the Laplace's equation. Therefore physical formula describing the relation between magnetic field and magnetization cannot be established.Because the difference between results obtained from scalar data and from vector data is very significant, we must use vector magnetic field data for magnetization analyses to get the more reliable and exact solutions. The development program of fundamental tools for exploration of deep seabed resources started with the financial support of the Ministry of Education, Culture, Sports, Science & Technology (MEXT) in 2008 and will end in 2012. In this project, we are developing magnetic exploration tools for seabed resources using AUV (Autonomous Underwater Vehicle) and other deep-towed vehicles to measure not the scalar magnetic field but the vector magnetic field in order to estimate magnetization structure below the sea-floor exactly and precisely. We conducted AUV magnetic survey in 2010 at the thermal area called Hakurei deposit in the Bayonnaise submarine caldera at the southern end of Izu island arc, about 400km south of Tokyo. We analyzed the observed vector magnetic fields to get the vector magnetic anomaly Fields using the method of Isezaki(1984). We inverted these vector magnetic anomaly fields to magnetization structure. CONCLUSIONS 1.The scalar magnetic field TIA (Total Intensity Anomaly) has no physical formula describing the relation between M (Magnetization) and TIA because TIA does not satisfy the Laplace's equation. Then it is impossible to estimate M from TIA. 2.Anlyses of M using TIA have been done so far under assumption TIA=PTA (Projected Total Anomay on MF (Main Geomagnetic Field)), however, which caused the analysis error due to ɛT= TIA - PTA . 3.We succeeded to measure the vector magnetic anomaly fields using AUV despite the severe magnetic noises

  19. CRED 5 m Gridded bathymetry of Baker Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (5 m cell size) bathymetry of the shelf and slope environments of Baker Island, Pacific Remote Isand Areas, Central Pacific. Almost complete bottom coverage...

  20. Hydrothermal mineralization at Kick'em Jenny submarine volcano in the Lesser Antilles island arc

    Olsen, R.; Carey, S.; Sigurdsson, H.; Cornell, W. C.


    Kick 'em Jenny (KeJ) is an active submarine volcano located in the Lesser Antilles island arc, ~7.5 km northwest of Grenada. Of the twelve eruptions detected since 1939, most have been explosive as evidenced by eyewitness accounts in 1939, 1974, and 1988 and the dominance of explosive eruption products recovered by dredging. In 2003, vigorous hydrothermal activity was observed in the crater of KeJ. Video footage taken by a remotely operated vehicle (ROV) during the cruise RB-03-03 of the R/V Ronald Brown documented the venting of a vapor phase in the form of bubbles that ascended through the water column and a clear fluid phase in the form of shimmering water. The shimmering water generally ascended through the water column but can also been seen flowing down gradient from a fissure at the top of a fine-grained sediment mound. These fine-grained sediment mounds are the only structure associated with hydrothermal venting; spire or chimney structures were not observed. Hydrothermal venting was also observed coming from patches of coarse-grained volcaniclastic sediment on the crater floor and from talus slopes around the perimeter of the crater. Samples were collected from these areas and from areas void of hydrothermal activity. XRD and ICPMS analyses of bulk sediment were carried out to investigate the geochemical relationships between sediment types. Sediment samples from the hydrothermal mound structures are comprised of the same components (plagioclase, amphibole, pyroxene, and scoria) as sediment samples from areas void of hydrothermal activity (primary volcaniclastic sediment) in the 500-63 μm size range. High resolution grain size analyses show that >78% of sediment in the hydrothermal mound samples are between 63-2 μm with 6-20% clay sized (talc, and I/S mixed layer) in the hydrothermal mound samples was confirmed x-ray diffraction analysis. Differences in major oxide composition of the two sediment types (depletion in Al2O3 but enrichments in MgO and Fe2O3

  1. Evolution and geochemistry of the Tertiary calc-alkaline plutons in the Adak Island region of the central Aleutian oceanic island arc

    Kay, Suzanne; Citron, Gary P.; Kay, Robert W.; Jicha, Brian; Tibbetts, Ashley


    Calc-alkaline plutons are major crustal building blocks of continental margin mountain belts like the Mesozoic to Tertiary Andes and the Sierra Nevada, but are rare in oceanic island arcs. Some of the most calc-alkaline I-type island arc plutons are in the Central Aleutians with the most extreme signatures, as indicated by FeO/MgO ratios of mafic volcanic and sedimentary rocks and postdate the small ~38 Ma tholeiitic Finger Bay pluton. The chemistry of these older magmatic rocks is basically similar to that of young Central Aleutian magmatic rocks with boninites and arc tholeiitic magmas seemingly being absent. The formation of the calc-alkaline plutons seems to require a sufficient crustal thickness, fluid concentration and contractional stress such that magma chambers can stabilize significant amounts of pargasitic hornblende. Seismic receiver function analyses (Janiszewski et al., 2013) indicate the modern Adak crust is ~ 37 km thick. Existing and new hornblende, plagioclase and biotite Ar/Ar ages from 16 Hidden Bay pluton and Gannet Lake stock gabbro, porphyritic diorite, diorite, granodiorite, leucogranodiorite and aplite samples range from 34.6 to 30.9 Ma and indicate an ~ 4 Ma intrusion history. Biotite Ar/Ar ages for Kagalaska gabbro and granodiorite samples range from 14.7 to 13.9 Ma. The new ages are consistent with the plutons being related to several eruptive centers and forming during the waning stages of volcanism as the magmatic arc front was displaced to the north, possibly in response to accelerated periods of forearc subduction erosion. The gabbroic to leucogranodioritic units evolved in the lower to mid-crust with more silicic magmas rising buoyantly to higher levels where final crystallization and segregation of aplites occurred. Most gabbro and all mafic diorite units are largely crystal cumulates; one gabbro approaches the melt composition of a high Al basalt. The volumetrically dominant silicic diorites and granodiorites (58-63% SiO2) show

  2. Differential timing of vertical-axis block rotations in the northern Ryukyu Arc: Paleomagnetic evidence from the Koshikijima Islands, Japan

    Tonai, Satoshi; Suganuma, Yusuke; Ashi, Juichiro; Itaya, Tetsumaru; Oiwane, Hisashi; Kiyokawa, Shoichi


    Over 300 samples for paleomagnetic analysis and K-Ar dating were collected from 27 sites at NW-SE and NE-SW trending dike swarms (herein, NW dikes and NE dikes, respectively) in the Koshikijima Islands, northern Ryukyu Arc. The NW dikes are Middle Miocene in age and have directions (D = - 37.7 ∘, I = 51.8 ∘, α95 = 9.6 ∘, and κ = 40.8) that are deflected westward relative to the stable eastern Asian continent. Conversely, the NE dikes, of Late Miocene age, have directions (D = 16.1 ∘, I = 57.7 ∘, α95 = 7.1 ∘, and κ = 41.9) that show no such deflection. These differences are interpreted as indicating that the Koshikijima Islands underwent approximately 40 ∘ of counter-clockwise rotation during the Middle to Late Miocene. A synthesis of the paleomagnetic and structural data suggests a three-stage history of extensional deformation: (1) displacement upon normal faults (F 1 faults) without vertical-axis block rotation, (2) strike-slip reactivation of F 1 faults and oblique-normal displacement on NE-SW-trending faults (F 2 faults) with vertical-axis block rotation, and (3) oblique-normal displacement on F 2 faults without vertical-axis block rotation. Regional differences in the timing and amount of counter-clockwise vertical-axis block rotations indicate that the northern Ryukyu Arc rotated as several distinct rigid blocks.

  3. Morphostructure at the junction between the Beata ridge and the Greater Antilles island arc (offshore Hispaniola southern slope)

    Granja Bruña, J. L.; Carbó-Gorosabel, A.; Llanes Estrada, P.; Muñoz-Martín, A.; ten Brink, U. S.; Gómez Ballesteros, M.; Druet, M.; Pazos, A.


    Oblique convergence between the Caribbean plate's interior and the inactive Greater Antilles island arc has resulted in the collision and impingement of the thickened crust of the Beata ridge into southern Hispaniola Island. Deformation resulting from this convergence changes from a low-angle southward-verging thrust south of eastern Hispaniola, to collision and uplift in south-central Hispaniola, and to left-lateral transpression along the Southern peninsula of Haiti in western Hispaniola. Using new swath bathymetry and a dense seismic reflection grid, we mapped the morphological, structural and sedimentological elements of offshore southern Hispaniola. We have identified four morphotectonic provinces: the Dominican sub-basin, the Muertos margin, the Beata ridge and the Haiti sub-basin. The lower slope of the Muertos margin is occupied by the active Muertos thrust belt, which includes several active out-of-sequence thrust faults that, were they to rupture along their entire length, could generate large-magnitude earthquakes. The interaction of the thrust belt with the Beata ridge yields a huge recess and the imbricate system disappears. The upper slope of the Muertos margin shows thick slope deposits where the extensional tectonics and slumping processes predominate. The northern Beata ridge consists of an asymmetrically uplifted and faulted block of oceanic crust. Our results suggest that the shallower structure and morphology of the northern Beata ridge can be mainly explained by a mechanism of extensional unloading from the Upper Cretaceous onward that is still active residually along the summit of the ridge. The tectonic models for the northern Beata ridge involving active reverse strike-slip faults and transpression caused by the oblique convergence between the Beata ridge and the island arc are not supported by the structural interpretation. The eastern Bahoruco slope an old normal fault that acts as a passive tear fault accommodating the sharp along

  4. Evolution of an intra-oceanic island arc during the late Silurian to late Devonian, New England fold belt

    Geochemical studies of volcanic rocks in the Gamilaroi terrane and Calliope Volcanic Assemblage, New England Fold Belt, eastern Australia, indicate that the setting in which these rocks formed changed in both space and time. The Upper Silurian to Middle Devonian basalts of the Gamilaroi terrane show flat to slightly light rare-earth element (LREE) depleted chondrite normalised patterns, depletion of high field strength elements (HFSE) relative to N-MORB, low Ti/V and high Ti/Zr ratios, high Ni, Cr and large-ion lithophile element (LILE) contents, features characteristic of intra-oceanic island arc basaltic magmas. They are associated with low-K, less mafic volcanics, showing moderate LREE enrichment, low Nb and Y contents and Rb/Zr ratios. The depletion of HFSE in the basalts indicates that the magmas were derived from a refractory source in a supra-subduction zone setting. The presence of such a zone implies that the arc was associated with a backarc basin, the location of which was to the west where a wide backarc region existed from the Middle Silurian. This polarity of arc and backarc basin suggests that the subduction zone dipped to the west. In contrast to their older counterparts, Middle to Upper Devonian basalts of the Gamilaroi terrane have MORB-like chondrite normalised patterns and higher Ti and lower LILE contents. Moreover, they have low Ti/Zr ratios and MORB-like Ti/V ratios and HFSE contents, features typical of backarc basins. Dolerites of the Gamilaroi terrane also have predominantly backarc basin signatures. These features suggest that both the basalts and dolerites have been emplaced in an extensional environment produced during the rifting of the intra-oceanic island arc lithosphere. A progressive increase in Ti/V ratios, and TiO2 and Fe2O3 contents at constant MgO, of stratigraphically equivalent basalts, towards the north-northwest part of the belt, is consistent with either greater extension to the north or melting of a more fertile magma

  5. 40 m Gridded bathymetry of Swains Island, American Samoa (Arc ASCII format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry (40 m cell size) of the slope environment of Swains Island, American Samoa. Almost complete bottom coverage was achieved in depths between 7 and...

  6. Geophysical characteristics of the Ninetyeast Ridge–Andaman island arc/trench convergent zone

    Subrahmanyam, C.; Gireesh, R.; Chand, S.; KameshRaju, K.A.; Rao, D.G.

    The convergence tectonics of the Ninetyeast Ridge (NER), upon the Andaman island arc–trench system is examined through an analysis of ETOPO2 bathymetry, satellite-derived free air gravity and seismic data. Oblique subduction and the buoyancy forces...

  7. Large seismic faults in the Hellenic arc

    B. S. Papazachos


    Full Text Available Using information concerning reliable fault plane solutions, spatial distribution of strong earthquakes (Ms³ 6.0 as well as sea bottom and coastal topography, properties of the seismic faults (orientation, dimension, type of faulting were determined in seven shallow (h < 40 km seismogenic regions along the convex part of thc Hellenic arc (Hellenic trench and in four seismogenic regions of intermediate depth earthquakes (h = 40-100 km along the concave part of this arc. Except for the northwesternmost part of the Hellenic trench, where the strike-slip Cephalonia transform fault dominates, all other faults along this trench are low angle thrust faults. III thc western part of the trench (Zante-west Crete faults strike NW-SE and dip NE, while in its eastern part (east Crete-Rhodos faults strike WNW-ESE and dip NNE. Such system of faulting can be attributed to an overthrust of the Aegean lithosphere on the eastern Mediterranean lithosphere. The longest of these faults (L = 300 km is that which produced the largest known shallow earthquake in the Mediterranean area (21 July 365, Ms = 8.3 which is located near the southwestern coast of Crete. The second longest such fault (L = l 70 km is that which produced a large earthquake (December 1303, Ms = 8.0 in the easternmost part of the trench (east of Rhodos island. Both earthquakes were associated with gigantic tsunamis which caused extensive damage in the coast of many Eastern Mediterranean countries. Seismic faults of the intermediate depth earthquakes in the shallow part of the Benioff zone (h = 40- 100 km are of strike-slip type, with a thrust component. The orientations of these faults vary along the concave part of the arc in accordance with a subduction of remnants of all old lithospheric slab from the convex side (Mediterranean to the concave side (Aegean of thc Hellenic arc. The longest of these faults (L = 220 km is that which produced the largest known intermediate depth earthquake in the

  8. Re-distribution of 137Cs Chernobyl signal in the Aegean Sea

    winter 1987 (just after the Chernobyl accident), and in winter 1993]. Actually, these two episodes have deeply modified the vertical profiles of 137Cs with respect to 1984, before the Chernobyl accident. In fact in 1999 - 2002, in the Lemnos and N-Skyros Basins, the 137Cs concentration increased from the surface to the bottom; in the deep waters it was about 5 Bq m-3, five times higher than in 1984. Historical observations and analyses suggest that the Cretan Sea is characterised by the formation of dense waters with variable characteristics, depending on the meteorological conditions and on the pre-conditioning of the water column. In the early nineties exceptionally dense, salty water started to fill the deep Cretan Basin and overflow the sills of the Cretan Arc straits. Since 1995 the outflow of very dense Cretan water to the Levantine and Ionian basins has diminished, corresponding to a long stagnation period regarding dense water production in the North (and possibly the South) Aegean. In the North Aegean, the evolution of 137Cs concentration in the deep basins is clearly controlled by vertical diffusion since 1994. In the South Aegean, the situation is not so clear: one of the main questions is whether the deep Cretan water is formed locally or if it is also partially originated in the Northern Basins. The high concentration of 137Cs (4.5 Bq.m-3) found in 2003 in the deep water of the South Aegean suggests a significant contribution of dense water from N-Aegean basins, having comparable 137Cs concentrations

  9. Multi-Hazards Geophysical Monitoring Through the Eastern Caribbean Islands arc: Strategy, Challenges and Future Development

    Fournier, N.; Lynch, L.; Robertson, R.; Latchman, J.; Mohais, R.; Ramsingh, C.


    The Seismic Research Unit (SRU), at the University of the West Indies, St Augustine, Trinidad, W.I., is responsible for monitoring and studying geological hazards in the English and Dutch speaking islands nestled along the ocean-ocean plate convergence zone in the Eastern Caribbean. The Unit operates a multi-hazards monitoring network that spans over 15 islands. Geophysical monitoring techniques include 11 broadband and 44 short period seismic stations, 4 accelerometers, 4 continuous GPS stations (cGPS) and over 50 ground-deformation benchmarks. This seismic network caters for general earthquake surveillance and study as well as for volcano early-warning. As part of the recent trust to improve tsunami surveillance capabilities in the Caribbean the unit has embarked on a program to upgrade a subset of the seismograph network. Near real-time satellite communications will be installed to improve the present network that is built around terrestrial Internet and telephone media. Additional strong motion accelerometers will also be operated alongside the broadband sensors at the upgraded stations to provide the necessary specifications for tsunami detection. Through real- time data exchanged with adjacent and global networks that are involved in the effort to establish a Tsunami Warning System for the Caribbean and adjacent regions, the Unit's capacity to monitor multiple hazard via the seismological method will be significantly improved. The geodetic monitoring program is a hybrid of near real-time data acquisition and static field surveys. It is principally geared towards volcano ground deformation monitoring. The main challenge while monitoring volcano ground deformation in small islands is the limited control on the reference station which are often located within the potential deformation field (versus been ideally outside any volcano related deformation field). As a result, SRU's strategy is to control reference stations in every island by long-baselines processing

  10. Temporal evolution of island arc magmatism: geochronology, petrology et geochemistry of mesozoic and cenozoic magmatic rocks from Sumatra (Indonesia); Evolution temporelle du magmatisme d`arc insulaire: geochronologie, petrologie et geochimie des magmatismes mesozoiques et cenozoiques de Sumatra (Indonesie)



    Sumatra island (Western Indonesia) belongs to the Sunda magmatic arc, which results from the subduction of the Indian ocean plate beneath the margin of the Eurasiatic continental block. Plutonic and volcanic rocks of Mesozoic and Cenozoic ages are very abundant in Sumatra, where they mainly outcrop in a NNW-SSE trending, 1,650 km-long stripe in the western part of the island. The spatial and temporal distributions of magmatic rocks in Sumatra were not previously investigated in detail. We have performed 175 {sup 40}K-{sup 40}Ar datings on bulk rocks and minerals separated from samples which have also been analysed for major and trace elements by ICP-AES. These results allow to discuss the distribution of magmatic events in space of a long subduction period on the chemical composition of the Sunda arc mantle wedge. (author)

  11. Tectonic setting of blueschist and island-arc terranes of west-central Baja California, Mexico

    Sedlock, R.L.


    Diverse oceanic rocks exposed in west-central Baja California (Mexico) are assigned to three shallowly dipping tectonic units. The lower plate is a subduction complex consisting of regionally metamorphosed blueschists and divided into structurally and petrologically distinct subterranes. The upper plate consists of Triassic-Lower Cretaceous arc rocks and overlapping mid-Cretaceous turbidites. A fault-bounded serpentinite-matrix melange between lower and upper plate rocks contains blueschist, eclogite, amphibolite, and variably serpentinized mafic and ultramafic blocks. Lower plate blueschists were metamorphosed in the late Early Cretaceous and uplifted along shallowly dipping normal faults during conditions of steady-state subduction. Exotic blocks of blueschist, eclogite, and amphibolite are derived from a cryptic terrane or terranes, record varied P-T-t histories, and were uplifted via tectonic emplacement or diapiric rise of serpentinite along the normal faults.

  12. Severe accidents due to windsurfing in the Aegean Sea.

    Kalogeromitros, A; Tsangaris, H; Bilalis, D; Karabinis, A


    Windsurfing is a popular sport and has recently become an Olympic event. As an open-air water activity that requires the participant to be in perfect physical condition, windsurfers may be prone to accidents when certain basic rules or procedures are violated. The current study monitored severe injuries due to windsurfing over a period of 12 months in the Aegean Sea in Greece. Our study revealed 22 cases of severe accidents due to windsurfing, with a wide range of injuries including head injuries, spinal cord injuries, and severe fractures of the extremities. Prolonged hospitalization, severe disability and two deaths occurred as consequences of these accidents. The study examined the characteristics of these patients and the possible risk factors and conditions associated with the accidents. We also focused on the most common types of injuries and reviewed the mechanisms that may provoke them. Water sports and particularly windsurfing represent a major challenge for the emergency medical system, especially in the Aegean Sea. Hundreds of islands, kilometres of isolated coasts, millions of tourists, an extended summer period and rapidly changing weather create conditions that constantly test the efficacy of the emergency services. The development of an appropriate infrastructure and maximum control of the risk factors causing these accidents could reduce the morbidity and mortality that, unfortunately but rather predictably, accompany this popular summer activity. PMID:12131638

  13. Geochemical characteristics and zircon U-Pb isotopic ages of island-arc basic igneous complexes from the Tianshui area in West Qinling

    PEI Xianzhi; LI Zuochen; LIU Huibin; LI Gaoyang; DING Saping; LI Yong; HU Bo; GUO Junfeng


    The Liushuigou intermediate-basic meta-igneous complex at Guanzizhen, Tianshui area, is mainly composed of metagabbro, metagabbro diorite and metadiorite, while the Baihua basic meta-igneous complex consists mainly of pyroxenite, gabbro (gabbro diorite), diorite and quartz diorite.They form a relatively complete comagmatic evolutionary series. The geochemical characteristics of intermediate-basic igneous rocks indicate that they belong to a tholeiite suite.Their chondrite-normalized REE patterns are nearly flat and are LREE-slightly enriched type, and their primitive mantle-normalized and MORB-normalized trace element spider-grams are generally similar; the LILEs Cs, Ba, Sr, Th and U are enriched, while Rb and K and the HFSEs Nb, P, Zr,Sm, Ti and Y are depleted. All these show comagmatic evolu-tionary and genetic characteristics. The tectonic environment discrimination by trace element reveals that these igneous complexes formed in an island-arc setting. The Thermal Ionization Mass Spectrometry (TIMS) single-grain zircon U-Pb age for the Liushuigou intermediate-basic meta-igneous rocks in the Guanzizhen area is (507.5 ± 3.0) Ma, represent-ing the age of these igneous complexes, which indicates that island-arc-type magmatite rocks in the northern zone of West Qinling are Late Cambrian and also reveals that the timing of subduction of the paleo-ocean basin represented by the Guanzizhen ophiolite and resulting island-arc-type magrnaticactivity are probably Late Cambrian to Early Ordovician.

  14. A tomography image of the Aegean region (Greece derived from inversion of macroseismic intensity data

    D. Papanastassiou


    Full Text Available The three-dimensional attenuation structure beneath the Aegean sea and the surrounding regions was determined by inversion of seismic intensity data. A large number of seismic intensity data have been accumulated in a uniform scale in the Aegean region, where the seismic activity is much higher than that of the other Mediterranean regions. Nearly 11000 seismic intensity data from 47 earthquakes that have occurred in these regions were used to determine the seismic attenuation structure. The resulting structure reveals a remarkable contrast of attenuation. In the top layer (depth 0-20 km, low Q is dominant in the central Aegean sea, while high Q is dominant in the surrounding land areas, except for Southwestern Turkey. The low-Q regions correspond to areas of Neogene-Quaternary grabens where the high seismicity of shallow earthquakes appears. In the lower layer (20-40 km low-Q areas are located in the southeastern part of the Hellenic arc. Some low-Q spots corresponding to the distribution of volcanoes exist along the volcanic arc. The low-Q spots might correspond to diapirs causing subduction volcanism.

  15. Oblique collision and accretion of the Netherlands Leeward Antilles island arc: A structural analysis of the Caribbean-South American plate boundary zone

    Beardsley, Amanda Gail


    The Netherlands Leeward Antilles volcanic island arc is an ideal natural laboratory to study the evolution of the Caribbean-South American plate boundary. The Leeward Antilles islands (Aruba, Curacao, and Bonaire) are located offshore western Venezuela, within the obliquely convergent diffuse plate boundary zone. Outcrop analysis, microthermometry, and 2D marine seismic reflection data provide evidence of three generations of regional deformation since the Late Cretaceous. Outcrop analysis of structural features, including faults, joints, and veins, characterizes the kinematic history of the islands. Fluid inclusion analysis of quartz and calcite veins coupled with apatite fission-track dating provides the island exhumation history. Finally, marine reflection seismic data processing and interpretation of newly acquired data elucidates offshore structures to integrate with our onshore results. The oldest regional deformation, resulting in both ductile (D1) and brittle (F 1) structures, is attributed to displacement partitioning along the arcuate Caribbean plate boundary. Associated crustal thinning initiated island exhumation, at a rate of 0.18 km/my, from a maximum burial depth of 6 km in the Late Cretaceous (˜89 Ma). Coeval with D1/F1 deformation and exhumation, stretching of the island arc resulted in extensive basin rifting that separated the island blocks. At ˜55 Ma, a change in the relative motion of the Caribbean plate altered plate boundary dynamics. Displacement along the right-lateral Caribbean transform fault and Oca - San Sebastian - El Pilar strike-slip fault system created a wrench tectonic regime within the diffuse plate boundary zone. A second generation of brittle structures (F2) developed while the islands were at a maximum burial depth of 2 km during the Paleocene/Eocene. Since ˜45 Ma, continued motion along the strike-slip fault systems and oblique plate convergence resulted in the youngest generation of structural features (F3). Regional

  16. Black Sea and Mediterranean Sea interaction: influence of the North Aegean dynamics

    Androulidakis, Yannis; Krestenitis, Yannis; Kourafalou, Vassiliki


    The brackish Black Sea Waters outflow to the Aegean Sea, through the Dardanelles Straits, affects and determines significantly the hydrodynamic and physical characteristics of the Aegean Sea. At the same time, it affects several biological parameters, like chl-a concentrations, and, therefore, the general quality of the marine environment. The investigation and mathematical simulation of the North Aegean's physical oceanography contributes to the knowledge and understanding of the buoyant waters' circulation initial conditions in the wider East Mediterranean region. The implementation and adaptation of the 3-d hydrodynamic mathematical model HYCOM (Hybrid Coordinate Ocean Model) in the North Aegean Sea (1/50οx1/50o), significantly contributes to the investigation of the area's hydrodynamic circulation. HYCOM, due to its hybrid coordinate operation, can describe at a satisfactory level, all the different topography and mixing cases of the complicated N. Aegean region. In addition, the high resolution atmospheric forcing and the nesting with a data assimilated broader Mediterranean HYCOM model along the southern open boundary of the North Aegean model, benefit the quality of the results and constitutes an important tool on the description and understanding of the Black Sea influence to the region's dynamics. A fundamental objective is the application and comparison of different Dardanelles outflow parameterizations based a) on the Black Sea water budget, b) on current measurements from a telemetric station in Limnos Island, and c) on historical time series. The Black Sea Waters plume evolution and the circulation patterns are dependant on the outflow rate magnitude, the flow distribution inside the straits and the prevailing winds. The long-term simulation covers the period of the last 20 years (1990-2010), investigating several physical characteristics of the North Aegean Sea, such as the deep water masses evolution, the major Black Sea waters circulation patterns

  17. CRED 20 m Gridded bathymetry and IKONOS estimated depths of Lisianski Island, Hawaii, USA (Arc ASCII format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry and IKONOS estimated depths of the shelf and slope environments of Lisianski Island, Northwestern Hawaiian Islands, Hawaii, USA. Bottom coverage...

  18. Scenario based tsunami wave height estimation towards hazard evaluation for the Hellenic coastline and examples of extreme inundation zones in South Aegean

    Melis, Nikolaos S.; Barberopoulou, Aggeliki; Frentzos, Elias; Krassanakis, Vassilios


    A scenario based methodology for tsunami hazard assessment is used, by incorporating earthquake sources with the potential to produce extreme tsunamis (measured through their capacity to cause maximum wave height and inundation extent). In the present study we follow a two phase approach. In the first phase, existing earthquake hazard zoning in the greater Aegean region is used to derive representative maximum expected earthquake magnitude events, with realistic seismotectonic source characteristics, and of greatest tsunamigenic potential within each zone. By stacking the scenario produced maximum wave heights a global maximum map is constructed for the entire Hellenic coastline, corresponding to all expected extreme offshore earthquake sources. Further evaluation of the produced coastline categories based on the maximum expected wave heights emphasizes the tsunami hazard in selected coastal zones with important functions (i.e. touristic crowded zones, industrial zones, airports, power plants etc). Owing to its proximity to the Hellenic Arc, many urban centres and being a popular tourist destination, Crete Island and the South Aegean region are given a top priority to define extreme inundation zoning. In the second phase, a set of four large coastal cities (Kalamata, Chania, Heraklion and Rethymno), important for tsunami hazard, due i.e. to the crowded beaches during the summer season or industrial facilities, are explored towards preparedness and resilience for tsunami hazard in Greece. To simulate tsunamis in the Aegean region (generation, propagation and runup) the MOST - ComMIT NOAA code was used. High resolution DEMs for bathymetry and topography were joined via an interface, specifically developed for the inundation maps in this study and with similar products in mind. For the examples explored in the present study, we used 5m resolution for the topography and 30m resolution for the bathymetry, respectively. Although this study can be considered as

  19. Regional setting and characteristics of the Neoproterozoic Wadi Hamama Zn-Cu-Ag-Au prospect: evidence for an intra-oceanic island arc-hosted volcanogenic hydrothermal system

    Abd El-Rahman, Yasser; Surour, Adel A.; El-Manawi, Abdel Hamid W.; El-Dougdoug, Abdel-Monem A.; Omar, Sayed


    The Wadi Hamama area is a volcanogenic Zn-Cu-Au-Ag prospect. It is hosted by a Neoproterozoic bimodal-mafic sequence, which comprises basalt, dacite and rhyolite along with volcaniclastic rocks. The rocks have a low-K tholeiitic affinity and are enriched in large ion lithophile elements over high field strength elements, which indicated their formation in an intra-oceanic island arc tectonic setting. The area was intruded by a tonalite-trondhjemite body, which has an intra-oceanic island arc affinity and later by diorite, which has a cordilleran-margin geochemical affinity. These rock units were intruded by post-tectonic granite dykes, which have a within-plate geochemical signature. There is a quartz-carbonate horizon extending along the contact between the basalt and the volcaniclastic rocks, mainly banded and lapilli tuffs. This horizon is of exhalative origin and is underlain by a mushroom-shaped alteration zone extending from the horizon down to the massive basalt. The footwall alteration is characterized by a silica-rich core surrounded by a thick chlorite sheath. Both the quartz-carbonate horizon and the footwall-altered rocks enclose historical trenches and pits. Sulfide-rich core samples are enriched in Zn, relative to Cu, and in Ag, which indicates the low-temperature nature of the hydrothermal system. The prospect was affected by supergene processes, which led to the widespread occurrence of secondary copper minerals and gold enrichment relative to the leached base metals, especially Zn. The prospect formed through a limited rifting of an intra-oceanic island arc which resulted in the formation of a small-scale volcanogenic Zn-Cu-Ag-Au prospect.

  20. Syn- and post-orogenic exhumation of metamorphic rocks in North Aegean

    R. Lacassin


    Full Text Available The Olympos-Ossa-Pelion (OOP ranges, in NW Aegean, encompass Greece highest summit and are located near the extremity of the North Anatolian Fault (NAF. Structural and thermochronological data gathered in the OOP ranges show that the main exhumation of metamorphic nappes occurred in the Eocene, at ca. 43–39 Ma. This early exhumation, associated with ductile, then brittle-ductile normal faulting with northeastward transport, is coeval with orogenic shortening in the close area. Cooling rates, and likely exhumation, have been low between ~40 Ma and ~20 Ma. 40Ar/39Ar crystallization ages (between 20 and 15 Ma appears related to brittle-ductile normal faulting and likely associated with Neogene Aegean back-arc extension. The dating of a diabase dyke, and the geometry of associated brittle jointing, of onshore and offshore active normal faults suggest a shift in extension direction after 4Ma, possibly in relation with the propagation of the NAF in northern Aegean.

  1. Exhumation of metamorphic rocks in N Aegean: the path from shortening to extension and extrusion

    R. Lacassin


    Full Text Available The Olympos-Ossa-Pelion (OOP ranges, in NW Aegean, encompass Greece highest summit and are located near the extremity of the North Anatolian Fault (NAF. Structural and thermochronological data gathered in the OOP ranges show that the main exhumation of metamorphic nappes occurred in the Eocene, at ca. 43–39 Ma. This early exhumation, associated with ductile, then brittle-ductile normal faulting with northeastward transport, is nearly coeval with orogenic shortening in the close area. Cooling rates, and likely exhumation, have been low between ~40 Ma and ~20 Ma. 40Ar/39Ar crystallization ages (between 20 and 15 Ma appears related to brittle-ductile normal faulting and likely associated with the onset of Aegean back-arc extension. The dating of a diabase dyke, and the geometry of associated brittle jointing, of onshore and offshore active normal faults imply a shift in extension direction after 4 Ma. Such a shift is probably related the propagation of the NAF in northern Aegean known to have occurred around 5 Ma.

  2. Neogene volcanism and extension in Western Anatolian-Aegean area: A new geodynamic model

    The widespread Western Anatolian-Aegean Neogene volcanism presents a complex geochemical evolution reflecting the uncommon space-time variability of the geodynamic setting of the region. In the Western Anatolian and Central Aegean, a widespread supra-subduction magmatism, with calc-alkaline to shoshonitic affinity, took place from Early to Middle Miocene; this phase of activity ends with spots of ultra-K lavas and dykes. From Late Miocene onwards scattered alkali basaltic lavas with intraplate affinity were emitted, while calc-alkaline activity occurred in the South Aegean arc. Since Late Oligocene-Early Miocene, the region was, and still is, affected by extensional tectonics generally ascribed to a backarc rift. However the Aegean region should rather be considered as an unconventional backarc since its characteristics rather differ from 'typical' backarcs. In fact, in spite of a long lasting(>40Ma) active NE-directed subduction of Africa, the backarc area still maintains a relatively thick continental crust (>20-25 km). Moreover, the upper Eurasian plate is overriding the lower Africa plate with separate segments, with Greece moving faster, and Turkey moving slower. The differential velocity between Greece and Turkey determines extension in the upper plate, unrelated to the loss of subducted retreating lithosphere, which is the usual setting for the origin of 'classic' backarc settings. The geodynamic framework is supported by the geochemical and isotopic features of the supra-subduction magmas revealing the occurrence of a trapped, drying slab, with progressive decreasing of Fluid Mobile Elements/Fluid Immobile Elements ratios, δ11B and δ7Li, coupled with scarce variations of Sr and Nd isotopes. Moreover, the differential motion between the Greek and Anatolian micro-plates creates tear zones with the formation of slab ruptures or vertical slab windows. The occurrence of such windows is, in fact, outlined by the presence of alkali basalts with intraplate

  3. Newly developed evidence for the original Tethysan island-arc volcanic rocks in the southern segment of the South Lancangjiang Belt


    This paper re-describes the characteristics of pre-Ordovician (Pt3) metamorphic volcanic rocks in the Huimin-Manlai region of Yunnan Province from the aspects of petrographic characteristics, rock assemblage, petrochemistry, REE, trace elements, lead isotopes and geotectonic setting. The metamorphic volcanic rocks maintain blasto-intergranular and blasto-andesitic textures; the volcanic rocks are characterized by a basalt-andesite-dacite assemblage; the volcanic rocks are basic-intermediate-intermediate-acid in chemical composition, belonging to semi-alkaline rocks, with calc-alkaline series and tholeiite series coexisting, and they are characterized by low TiO2 contents; their REE distribution patterns are of the LREE-enrichment right-inclined type; the volcanic rocks are enriched in large cation elements and commonly enriched in Th and partly depleted in Ti, Cr and P, belonging to the Gondwana type as viewed from their Pb isotopic composition; petrochemically the data points fall mostly within the field of island-arc volcanic rocks. All these characteristics provided new evidence for the existence of original Tethysan island-arc volcanic rocks in the region studied.

  4. Geochemical Evidence from the Kohistan Complex for Differentiation of Garnet Granulitic lower Crust in Island Arcs by Dehydration Melting of Amphibole-bearing Plutonics: Implications for the Andesite Model of Continental Crustal Growth

    Garrido, C. J.; Bodinier, J.; Burg, J.; Zeilinger, G.; Hussain, S. S.; Dawood, H.; Gervilla, F.


    We report a geochemical study of the Jijal and Sarangar complexes constituting the lower crust of the Mesozoic Kohistan paleo-island arc (N. Pakistan). The Jijal complex is composed of basal peridotites topped by a gabbroic section made up of mafic garnet granulite-with minor lenses of garnet hornblendite and granite-grading up section to hornblende gabbronorite. The Sarangar complex is constituted by metagabbro. Sarangar gabbro and Jijal hornblende gabbronorite have melt-like, LREE-enriched REE patterns similar to those of island arc basalts. These rocks and Jijal garnet granulite define altogether negative covariations of LaN, YbN and (La/Sm)N with Eu* (=2xEuN/SmN+GdN; N= chondrite normalized), and positive covariations of (Yb/Gd)N with Eu*. REE modeling indicates that these covariations cannot be accounted for by high-pressure crystal fractionation of hydrous primitive or derivative andesites. They are consistent with formation of garnet granulites as plagioclase-garnet assemblages with variable trapped melt fractions via either high-pressure crystallization of primitive island arc basalts or dehydration melting of hornblende gabbronorite, providing that the amount of segregated or restitic garnet was low (hornblende gabbronorite. Similarly, Jijal garnet-bearing hornblendite lenses were most likely generated by coeval dehydration melting of hornblendites. Furthermore, melting models and geochronological data point to intrusive leucogranites in the overlying Metaplutonic complex as the melts generated by dehydration melting of the plutonic protoliths of Jijal garnet-bearing restites. Consistently with the metamorphic evolution of the Kohistan lower arc crust, dehydration melting occurred at the mature stage of this island arc when shallower hornblende-bearing plutonics were buried to depth exceeding 25-30 km and heated at temperatures above ca. 900 oC. Available experimental data on dehydration melting of amphibolitic sources imply that thickening of oceanic arcs

  5. Evolution of freshwater crab diversity in the Aegean region (Crustacea: Brachyura: Potamidae).

    Jesse, Ruth; Grudinski, Melanie; Klaus, Sebastian; Streit, Bruno; Pfenninger, Markus


    The aim of this study was to estimate the influence of the palaeogeographic and climatic history of the Aegean region on the diversity of freshwater crabs of the genus Potamon and to test whether this area served as source or reservoir in species diversity. Necessary species delimitation was accomplished by phylogenetic analyses of the mitochondrial markers COX1 and ND1, partial 16S rRNA gene and the tRNALeu gene. We found 14 genetic lineages of which nine could be assigned to previously recognised species. Temporal estimates of the splitting pattern in the phylogeny of Potamon indicated that a combination of geological and climatic events influenced their diversification. Within Potamon, the lineages separated into a western group and an eastern group. This first split in the genus occurred approximately 8.3-5.5 Mya, thus possibly correlated with the Messinian salinity crisis. A likelihood approach to geographic range evolution suggested for most species, occurring in the Aegean area, an origin in the Middle East. Moreover, there were no insular endemics in the central Aegean archipelago, therefore low sea-levels during the Pleistocene glacial periods possibly enabled dispersal to these islands, but subsequent rise in sea-level did not cause speciation. Nevertheless, the diversification of most lineages occurred during the Pleistocene epoch thus coinciding with Quaternary fluctuations of the climate. PMID:21216297

  6. Alaska Open-file Report 144 Assessment of Thermal Springs Sites Aleutian Arc, Atka Island to Becherof Lake -- Preliminary Results and Evaluation

    Motyka, R.J.; Moorman, M.A.; Liss, S.A.


    Twenty of more than 30 thermal spring areas reported to exist in the Aleutian arc extending from Atka Island to Becherof Lake were investigated during July and August, 1980. Thermal activity of three of these sites had diminished substantially or no longer existed. At least seven more sites where thermal-spring activity is probable or certain were not visited because of their remoteness or because of time constraints. The existence of several other reported thermal spring sites could not be verified; these sites are considered questionable. On the basis of geothermometry, subsurface reservoir temperatures in excess of 150 C are estimated for 10 of the thermal spring sites investigated. These sites all occur in or near regions of Recent volcanism. Five of the sites are characterized by fumaroles and steaming ground, indicating the presence of at least a shallow vapor-dominated zone. Two, the Makushin Valley and Glacier Valley thermal areas, occur on the flanks of active Mukushin Volcano located on Unalaska Island, and may be connected to a common source of heat. Gas geothermometry suggests that the reservoir feeding the Kliuchef thermal field, located on the flanks of Kliuchef volcano of northeast Atka Island, may be as high as 239 C.

  7. The Role of Philippine Sea Plate to the Genesis of Quaternary Magmas of Northern Kyushu Island, Japan, Inferred from Along-Arc Geochemical Variations

    Shibata, T.; Yoshikawa, M.; Itoh, J.; Ujike, O.; Miyoshi, M.; Takemura, K.


    Quaternary volcanoes on Kyushu Island comprise volcanoes Himeshima, Futagoyama, Yufu-Tsurumi, Kuju, Aso, Kirishima and Sakurajima from north to south alongstrike the volcanic front. Adakitic lavas are observed from Yufu-Tsurumi and Kuju volcanoes in northern Kyushu (Kita et al., 2001; Sugimoto et al., 2007), whereas no Quaternary adakites were observed at Aso (e.g., Hunter, 1998) and the volcanoes south of Aso along the entire Ryukyu arc. Sugimoto et al. (2007) suggested that the trace element and Sr, Nd, and Pb isotopic compositions of adakitic magmas from Yufu-Tsurumi volcano indicate derivation of the magmas by partial melting of the subducting PSP. In contrast, Zellmer et al. (2012) suggested that these adakites may have formed by fractional crystallization of mantle-derived mafic magmas within the garnet stability field in the crust. The Honshu-Kyushu arc transition is a particular favorable setting to address these controversial models for the origin of the adakitic lavas, because of the potential relationship between the PSP materials and the alongstrike variation of the lava chemistry. The Palau-Kyushu ridge divides the oceanic crust of the PSP into northeastern and southwestern segments with ages of 26-15 (Shikoku Basin) and 60-40 Ma (West Philippine Basin), respectively (Mahony et al., 2011). Although there are no clear plate images beneath northern Kyushu, the northern extension of the Palau-Kyushu ridge potentially corresponds to the boundary between the SW Japan and Ryukyu arcs. If adakite genesis was related to the subducted slab rather than the overlying crust, then the spatial distribution of Quaternary adakites should correlate with the age of the subducted PSP. In order to test such correlation and elucidate the petrogenesis of the northern Kyushu adakites, we compiled major and trace elements and Sr-Nd-Pb isotope ratios from volcanoes along the arc front that includes the transition from adakitic to non-adakitic arc volcanism. Comprehensive

  8. CRED 60m Gridded bathymetry and IKONOS estimated depths of UTM Zone 3, Northwestern Hawaiian Islands, USA (Arc ASCII format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry and IKONOS estimated depths of the shelf and slope environments of the Northwestern Hawaiian Islands, USA within UTM Zone 3. Bottom coverage was...

  9. CRED 5 m Gridded bathymetry of Kingman Reef, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (5 m cell size) bathymetry of the lagoon, shelf and slope environments of Kingman Reef, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  10. CRED 20 m Gridded bathymetry of Johnston Atoll, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry (20 m cell size) of the shelf and slope environments of Johnston Atoll, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  11. CRED 40 m Gridded bathymetry of Palmyra Atoll, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (40 m cell size) bathymetry of the lagoon, shelf and slope environments of Palmyra Atoll, Pacific Remote Island Areas, Central Pacific. Almost complete...

  12. CRED 5 m Gridded bathymetry of Johnston Atoll, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry (5 m cell size) of the shelf and slope environments of Johnston Atoll, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  13. CRED 60 m Gridded bathymetry and IKONOS estimated depths of UTM Zone 2, Northwestern Hawaiian Islands, USA (Arc ASCII format)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry and IKONOS estimated depths of the shelf and slope environments of the Northwestern Hawaiian Islands, USA within UTM Zone 2. Bottom coverage was...

  14. Illegal immigration in the eastern Aegean Sea: a new source of marine litter



    Full Text Available The maritime area dominates the current increasing wave of illegal immigration to Europe. The Greek islands of the eastern Aegean Sea are the main entrance points of immigrants arriving from the coasts of Turkey. Immigration to the Greek islands is mainly conducted with inflatable boats, which are abandoned upon arrival along the coasts together with other items such as life-jackets, inflatable tubes, and clothing. This novel type of marine litter dominates many beaches and becomes increasingly abundant. Two beaches in Lesvos Island were surveyed for marine litter, and immigration-related items were found to account for more than 97% of marine litter by weight. Immigration-related littering adds pressure on marine biodiversity and the local economy, impacting the recreational value of beaches.

  15. Seismically active column and volcanic plumbing system beneath the island arc of the Izu-Bonin subduction zone

    Špičák, Aleš; Vaněk, Jiří; Hanuš, Václav


    Roč. 179, č. 3 (2009), s. 1301-1312. ISSN 0956-540X Institutional research plan: CEZ:AV0Z30120515 Keywords : seismicity and tectonics * volcano seismology * subduction zone processes * volcanic arc processes * magma migration and fragmentation * Pacific Ocean Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.435, year: 2009

  16. Focal Mechanisms at the convergent plate boundary in Southern Aegean, Greece.

    Moshou, Alexandra; Papadimitriou, Eleftheria; Drakatos, George; Evangelidis, Christos; Karakostas, Vasilios; Vallianatos, Filippos; Makropoulos, Konstantinos


    Greece is characterized by high seismicity, mainly due to the collision between the European and the African lithospheric plates and the dextral strike slip motion along the North Anatolia Fault zone and North Aegean Trough. The subduction of the Eastern Mediterranean oceanic plate along the Hellenic Arc under the Aegean microplate along with the accompanied roll back of the descending slab is considered the main tectonic feature of the region (Papazachos and Comninakis 1971; Makropoulos and Burton 1984; Papazachos et al. 2000a, b). The divergent motion between the Aegean block and mainland Europe is indicated by an extension zone in the northern Aegean, with Crete and Aegean diverging from mainland Europe at a rate of about 3.5 cm yr-1 with Africa moving northward relative to Europe at a rate of about 1 cm yr-1 (Dewey et al., 1989; Papazachos et al., 1998; Mc-Clusky et al., 2000; Reilinger et al., 2006). In this tectonically complicated area diverge types of deformation are manifested, in addition to the dominant subduction processes. Aiming to shed more light in the seismotectonic properties and faulting seismological data from the Hellenic Unified Seismological Network (HUSN) were selected and analyzed for determining focal mechanisms using the method of moment tensor inversion, additional to the ones being available from the routine moment tensor solutions and several publications. Thus, 31 new fault plane solutions for events with magnitude M>4.0, are presented in this study, by using the software of Ammon (Randall et al., 1995). For this scope the data from at least 4 stations were used with an adequate azimuthal coverage and with an epicentral distance not more than 350 km. The preparation of the data includes the deconvolution of instruments response, then the velocity was integrated to displacement and finally the horizontal components were rotated to radial and transverse. Following, the signal was inverted using the reflectivity method of Kennett (1983

  17. Compilation of seismic structural models of the Kyushu-Palau Ridge, paleo-island arc in the Philippine Sea plate, at 13-30 N

    Nishizawa, A.; Kaneda, K.; Oikawa, M.


    The Kyushu-Palau Ridge (KPR) is a 2600 km long bathymetric high extending north-south at the center of the Philippine Sea plate. The origin of the KPR is regarded as a remnant of the proto Izu-Ogasawara (Bonin)-Mariana (IBM) Island arc that was separated by backarc spreading of the Shikoku and Parece Vela Basins in the late Eocene. The extensive seismic explorations were implemented to grasp the spatial distribution of the arc crust of the KPR in 2004-2008 under the Japanese Continental Shelf Survey Project. We carried out 27 seismic reflection and refraction profiles across the ridge between 13 and 30 N and one along the ridge in the northernmost part. We deployed ocean bottom seismographs (OBSs) as a receiver at an average interval of 5 km along each line. A tuned airgun array with a volume of 8,040 cubic inches (132 liters) or a non-tuned airgun array with a volume of 6,000 cubic inches (98 liters) was shot at an interval of 200 m (90 sec) for the wide-angle seismic profiles. Multichannel reflection data using 480 ch. or 240 ch. hydrophone streamer were also collected on the coincident lines. We obtained P-wave velocity models using tomographic inversion, forward modeling with two-dimensional ray tracing and comparison with synthetic seismograms. The maximum crustal thickness for each profile across the KPR varies from 8 to 23 km among the seismic lines. The KPR crusts are roughly thicker in the north than those in the south and are always thicker than the neighboring backarc basin oceanic crusts of the West Philippine Basin to the west and of the Shikoku and Parece Vela Basins to the east. The thick crust is mainly attributed to the lower crust with P-wave velocity of 6.8-7.2 km/s. Pn velocities just beneath the KPR are less than 8 km/s, often accompanying with rather high Vp of 7.2 km/s at the base of the crust. Reflection signals observed in far offsets along several lines suggest some reflectors exist at the depths 23-40 km beneath the KPR. The crustal

  18. Anelastic attenuation structure of the southern Aegean subduction area

    Ventouzi, Chrisanthi; Papazachos, Constantinos; Papaioannou, Christos; Hatzidimitriou, Panagiotis


    The study of the anelastic attenuation structure plays a very important role for seismic wave propagation and provides not only valuable constraints for the Earth's interior (temperature, relative viscosity, slab dehydration and melt transport) but also significant information for the simulation of strong ground motions. In order to investigate the attenuation structure of the broader Southern Aegean subduction area, acceleration spectra of intermediate depth earthquakes produced from data provided by two local networks which operated in the area were used. More specifically, we employed data from approximately 400 intermediate-depth earthquakes, as these were recorded from the EGELADOS seismic monitoring project which consisted of 65 land stations and 24 OBS recorders and operated during 2005-2007, as well as data from the earlier installed CYCNET local network, which operated during 2002-2005. A frequency-independent path attenuation operator t* was computed for both P and S arrivals for each waveform, using amplitude spectra generated by the recorded data of the aforementioned networks. Initially, estimated P and S traveltimes were examined and modeled as a function of epicentral distance for different groups of focal depths, using data from the CYCNET network in order to obtain the expected arrival information when original arrival times were not available. Two approaches to assess the spectral-decay were adopted for t* determination. Initially, an automated approach was used, where t* was automatically calculated from the slope of the acceleration spectrum, assuming an ω2 source model for frequencies above the corner frequency, fc. Estimation of t* was performed in the frequency band of 0.2 to 25 Hz, using only spectra with a signal-to-noise ratio larger than 3 for a frequency range of at least 4Hz for P-waves and 1Hz for S-waves, respectively. In the second approach, the selection of the linearly-decaying part of the spectra where t* was calculated, was

  19. Mechanisms for tectonic erosion of an accretionary complex in the d'Entrecasteaux Zone-New Hebrides Island arc collision zone

    Collot, J.Y. (Orstom, Villefranche-sur-mer (France)); Fisher, M.A. (Geological Survey, Menlo Park, CA (USA))


    In the southwest Pacific Ocean the d'Entrecasteaux Zone (DEZ) is an arcuate submarine mountain chain that collides with the central part of the New Hebrides island arc. The collision zone moves slowly (2.5 cm/yr) northward along the trench, owing to the small oblique angle between the DEZ and the azimuth of convergence. Extensive Seabeam bathymetry as well as single- and multichannel seismic reflection data were collected over both the collision zone and the accretionary wedge that lies south of this zone. These data indicate that the accretionary complex underwent considerable tectonic erosion in response to oblique subduction of the DEZ during the past 8 Ma. Simplified calculation indicates that the mean erosional rate of this complex is 800-900 km{sup 3}/Ma. The main mechanisms for tectonic erosion of the accretionary complex involve mass wasting and extensional tectonics. First, mobilization and mass wasting of accreted rocks result in overlapping slump masses that blanket the arc slope. Second, block sliding along an extensional detachment within accreted rocks strips off the upper (about 1 km) part of the accretionary complex. Third, as the DEZ moves northward, the accreted rocks in the wake of the DEZ lose support and collapse along large normal faults that trend oblique to the arc slope. An additional errosive mechanism involves the formation of a deep subcircular reentrant into the accretionary complex; the reentrant is believed to be a scar caused by the collision and subduction of a seamount. The reentrant cuts downward through the accreted rocks almost to the depth of the abyssal oceanic plain.

  20. Static Stress Changes Inverted from Microseismicity in Eastern Aegean Sea

    Leptokaropoulos, Konstantinos; Papadimitriou, Eleftheria; Orlecka-Sikora, Beata; Karakostas, Vassilios


    In this study we attempted to derive static stress field variations from the changes of earthquake production rates in Kusadasi bay and Samos island (eastern Aegean), by applying the Dieterich et al. (2000) Rate/State formulation. The calculation of stress changes from earthquake occurrence rates fluctuations should be obtained from catalogues which achieve adequate spatial and temporal resolution and well determined hypocenter coordinates. For this reason we took advantage of the data from a regional network operating since July of 2007, providing continuous monitoring of microseismicity, along with data available from seismological stations of the permanent Hellenic Unified Seismological Network (HUSN). The high accuracy and large sized regional catalogue is utilized for inverting seismicity rate changes into stress variation through a Rate/State dependent friction model. After explicitly determining the physical parameters incorporating in the modeling (reference seismicity rates, characteristic relaxation time, constitutive properties of fault zones) we investigated stress changes in both space and time regime and their possible connection with earthquake clustering and fault interactions. The main interest is focused on the June 2009 Samos Mw=5.1 event, which was followed by an intense seismic activity for several days. We attempt to reproduce and interpret stress changes both before and after the initiation of this seismic burst. The differences between the earthquake occurrence rates before and after the main shock are used as input data in a stress inversion algorithm based upon the Rate/State dependent friction concept in order to provide an estimation of stress changes. Diverse assumptions and combinations of the parameters values are tested for the model performance and sensitivity to be evaluated. The approach followed here could provide evidence of the robustness of the seismicity rate changes usage as a stress meter for both positive and negative

  1. Temporal patterns of detachment faulting along Cycladic extensional metamorphic domes, Aegean region

    Schneider, D. A.; Grasemann, B.; Heizler, M.; Vogel, H.; Iglseder, C.


    The Aegean region together with the surrounding mainland areas are known for Miocene to Recent active, notably extensional tectonics that are the result of the retreating Hellenic slab, gravitational collapse of the region and, since the Late Miocene to Early Pliocene, the westward escape of Anatolia relative to Eurasia. Project ACCEL (Aegean Core Complexes along an Extended Lithosphere) has collected an extensive modern structural dataset for the islands of Kea, Kithnos, and Serifos of the western Cyclades. On all three islands, crustal-scale, low-angle frictional-viscous shear zones have been identified and record strikingly consistent SSW-directed extensional kinematics together with a WNE-ESE shortening component. The geology of Kea is dominated by highly-strained, greenschist-facies schists, calc-silicates and marbles; a major, 100's m thick ultramylonite zone defines this northern island as a structural dome. White mica Ar-Ar thermochronometry performed on variably deformed units from different structural levels yield consistent Early Miocene (15-19 Ma) cooling ages across the entire island. Other pervasively deformed shallow crustal regions of the Cyclades (Tinos and Andros; b-type domes of Jolivet et al. 2004) also record similar Early Miocene cooling. Comparable geology and structure is exposed on Serifos although locally deformed under amphibolite-facies conditions and intruded in the south by a Late Miocene granodiorite. A major high strain zone that is present on the island is localized along an earlier (Late Eocene) granitic pluton. White micas from mylonites and gneisses along this shear zone and from rocks in the southern portion of the island yield Late Miocene (8-9 Ma) cooling ages, whereas greenschist-facies units in northern Serifos that are dominated by a different structural record of several phases of folding yield Oligocene (30-34 Ma) mica Ar-Ar cooling ages. Oligocene ages are similarly reported from Evvia and Sifnos, which are noted for

  2. Early Cretaceous arc volcanic suite in Cebu Island, Central Philippines and its implications on paleo-Pacific plate subduction: Constraints from geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

    Deng, Jianghong; Yang, Xiaoyong; Zhang, Zhao-Feng; Santosh, M.


    The Philippine island arc system is a collage of amalgamated terranes of oceanic, continental and island arc affinities. Here we investigate a volcanic suite in Cebu Island of central Philippines, including basalt, diabase dike, basaltic pyroclastic rock and porphyritic andesite. LA-ICP-MS U-Pb geochronology of zircon grains from the porphyritic andesite and pyroclastic rock yielded ages of 126 ± 3 Ma and 119 ± 2 Ma, respectively, indicating an Early Cretaceous age. The age distribution of the detrital zircons from river sand in the area displays a peak at ca. 118 Ma, close to the age of the pyroclastic rock. The early Cretaceous volcanic rocks in the central Philippines were previously regarded as parts of ophiolite complexes by most investigators, whereas the Cebu volcanics are distinct from these, and display calc-alkaline affinity and island arc setting, characterized by high LREE/HREE ratios and low HFSE contents. These features are similar to the Early Cretaceous arc basalts in the Amami Plateau and east Halmahera in the northernmost and southernmost West Philippine Basin respectively. Zircon Hf isotopes of the pyroclastic rocks show depleted nature similar to those of the Amami Plateau basalts, implying the subducted Pacific-type MORB as probable source. Zircon Hf isotopes of the porphyritic andesite show slight enrichment relative to that of the pyroclastic rocks and MORB, indicating subducted sediments as a minor end-member in the source. The Hf isotopic compositions of the volcanic rocks are also reflected in the detrital zircons from the river sands. We propose that the volcanic rocks of Cebu Island were derived from partial melting of sub-arc mantle wedge which was metasomatized by dehydration of subducted oceanic crust together with minor pelagic sediments. Within the tectonic environment of Southeast Asia during Early Cretaceous, the volcanic rocks in Cebu Island can be correlated to the subduction of paleo-Pacific plate. The Early Cretaceous

  3. The Cryogenian arc formation and successive high-K calc-alkaline plutons of Socotra Island (Yemen)

    Denele, Y.; Leroy, S.; Pelleter, Ewan; Pik, R; Talbot, J-y.; Khanbari, K.


    The Socotra Island belongs to the southern rifted margin of the Gulf of Aden and occupied in Neoproterozoic times a key position to constrain the age and the nature of the largely hidden Neoproterozoic rocks of the Arabian plate. Our integrated field, petrographic, geochemical and geochronological study in the Neoproterozoic rocks recognises three main successive events: (a) high-temperature ductile deformation and metamorphism forming probably in a compressive or transpressive regime; (b) ma...

  4. Description of the first Lessepsian squid migrant, Sepioteuthis lessoniana (CEPHALOPODA: Loliginidae, in the Aegean Sea (Eastern Mediterranean



    Full Text Available Loliginid squids of the Sepioteuthis lessoniana complex are widely spread in the Indo-Pacific Ocean, where they constitute a commercially important resource for neritic fisheries. Sepioteuthis lessoniana is the only Lessepsian squid migrant till now, recorded for the first time in the Mediterranean in 2002 along the Turkish Levantine coasts. Two maturing males, with mantle lengths 193 mm and 244 mm, have been recently caught near the coasts of Rhodes Island (SE Aegean, extending the species distribution northward, into Hellenic waters. Their identity was confirmed by comparison of the main body, beak characteristics and morphometric measurements with those available in the literature for this species. Suspected expansion of the Lessepsian loliginid into the Aegean Sea, due to the gradual warming of the sea, is discussed.

  5. Repeated magmatism at 34 Ma and 23-20 Ma producing high magnesian adakitic andesites and transitional basalts on southern Okushiri Island, NE Japan arc

    Sato, Makoto; Shuto, Kenji; Nohara-Imanaka, Rikako; Takazawa, Eiichi; Osanai, Yasuhito; Nakano, Nobuhiko


    The southern part of Okushiri Island in the present-day back-arc margin of the NE Japan arc is one of the rare convergent plate boundaries where similar magma types (high-magnesian adakitic andesite (HMAA) and high-TiO2 basalt (HTB)) have been erupted concurrently at more than one time. Oligocene HMAA can be divided into two types: HMAA-I is characterized by high Sr/Y and low Y, and HMAA-II by relatively low Sr/Y and high Y. HMAA-I is primitive in terms of MgO (8.5 wt.%), Mg# (67), Ni (232 ppm) and Cr (613 ppm) contents, and the most Mg-rich olivine phenocrysts plot within the mantle olivine array in terms of Fo and NiO. The similar Cr versus Ni relations of types I and II HMAA indicate some interaction of slab-derived adakitic melts with mantle peridotite, whereas Ni contents are higher than those of most boninites derived by partial melting of mantle peridotite at a given Cr content. Types I and II HMAA have more enriched Sr and Nd isotopic compositions than N-MORB. The petrography and geochemistry of these rocks, combined with published results on the genesis of high-magnesian andesite (HMA) indicate that types I and II HMAA could be produced by interaction of slab (N-MORB and sediment)-derived adakitic melts with mantle peridotite. The comagmatism of HMAA and HTB is ascribed to the following model. A cool, less hydrous, adakite magma (spherical diapir) would rise from the subducting slab (Pacific Plate) and become more hydrous as a result of its interaction with overlying hydrous peridotite. This hydrated adakitic diapir further ascends and is heated on entering the overlying mantle wedge. Subsequently, the temperature and H2O gradients in the ascending adakitic diapir and surrounding mantle peridotite would have been established. The HTB magma segregated from the surrounding mantle peridotite region (high temperature and low H2O content) at a depth of 60 km or more, whereas the adakitic diapir (low temperature and high H2O content) continued to rise, with its

  6. Cephalopods distribution in the southern Aegean Sea



    Full Text Available The present study concerns faunal composition and distribution of cephalopods in the southern Aegean Sea (35Ζ 13’ 19’’- 37Ζ 55’ 25’’ N, 23Ζ 00’ 15’’ - 28Ζ 15’ 37’’ E. Samples were collected from 708 hauls, obtained by an experimental bottom trawl net during eight surveys carried out in the summers of the years 1994-2001, as well as by commercial trawl net during four surveys carried out in September 1995, December 1995, May and September 1996. The hauls were performed at depths ranging from 16 to 778 m. A total of 34 species of cephalopod in 12 families were identified, including 11 oegopsid squid, 3 myopsid squid, 7 octopod, 3 cuttlefish and 10 sepiolid. Trawling with the experimental net resulted in the capturing of some uncommon pelagic species, such as Ctenopteryx siculaand Octopoteuthis sicula, which were recorded for the first time in the Aegean Sea. Most of the species showed a wide depth and geographical range. The species: Sepia officinalis, Sepietta neglecta, Sepietta obscuraand Sepiola rondeletiwere caught only on the continental shelf, whereas the Ancistroteuthis lichtensteini, Bathypolypous sponsalis, Brachioteuthis riisei, Chiroteuthis veranyi, Ctenopteryx sicula, Heteroteuthis dispar, Histioteuthis reversa, Neorossia caroli and Pyroteuthis margaritiferawere found only on the slope. The rest of the species extended in both continental shelf and slope. The spatial distribution of different species groups is discussed in relation to the hydrology and topography of the study area and the species ecology.

  7. Determination of Upper Mantle Heterogeneity Beneath Aegean-Anatolian Region from Travel Time Tomography

    Aksari, D.; Simbaad Team


    Movement and the deformation of the continental lithosphere are not clear completely. In the first end-member model, the lithosphere consists of essentially rigid blocks (with most of the strength located in the upper crust) that float on the asthenosphere, are separated by lithospheric faults, and move because of forces applied to their edges. The second model holds that the lithosphere (including the upper mantle) deforms as a continuum, and that the upper crust moves in response to tractions applied to its base. Most elements of the debate are related to deformation at the surface or within the shallow crust (fault kinematics, geodetic displacements, or earthquake mechanisms). The Aegean Sea, the surrounding Greek coasts and the western Turkey, along with the Hellenic Arc, are the most active seismic areas of the Mediterranean Basin and of the whole Alpine-Himalayan chain. The catalogues of seismicity are certainly incomplete for low magnitude events (M30 km). This happens along the Hellenic Arc and in the Antalya Gulf (southern Turkey). In the whole area, the frequency of events with magnitude greater than 4, is evident, but there are many events with lower magnitudes. Teleseismic tomography is a powerful tool used to obtain about the deep velocity perturbations in the Earth, using travel times recorded by a regional network from distant sources (usually at distances of more than 20°). This method has been developed since the seventies [1] and has been successfully used for the investigation of different regions (e.g. [2-3]). The images of seismic anomalies are then used for the estimation of the distribution of temperature, density and other parameters [4], which then can be used for geodynamic modeling, gravity inversion [2,5] and other applications. We expect to obtain a 3D image of the velocity structure of the Hellenic Arc Zone beneath Greece and Aegean region to a depth of about 300 km. The results might provide better constrains on the evolution of the

  8. Sr-Pb-Nd isotopic evidence that both MORB and OIB sources contribute to oceanic island arc magmas in Fiji

    Twenty-eight new Pb, 20 Sr, and 9 Nd isotopic compositions are presented for 32 rocks and one galena from Fiji and the South Fiji (back-arc) Basin. The Fijian rocks range in age from 35 to 143Nd/144Nd and low 206Pb/204Pb). Nearly constant 207Pb/204Pb, and an OIB source component lying within the conventional Sr-Nd-Pb mantle array. In later calc-alkaline and shoshonitic series rocks, these same trace element and isotopic ratios are more like those of OIB. The change was not accompanied by an increase in 207Pb/204Pb or Cs/K, indeed, 207Pb/204Pb is closer to the mantle array in these later series. Consequently, the change indicates a greater contribution from OIB sources, rather than from recycled ocean crust. These interpretations require that both MORB and OIB sources coexist in the uppermost mantle above subducted lithosphere. (orig./WB)

  9. The miocene Ashizuri complex (SW Japan): source and magma differentiation of an alkaline plutonic assemblage in an island-arc environment

    The Ashizuri complex, mainly composed of gabbro, syenite and granite, belongs to the Shimanto Middle Miocene magmatic province and represents one of the rare examples of a within-plate-like alkaline complex in an island-arc setting. This complex is temporally and spatially associated with calc-alkaline volcano-plutonic bodies and, in a lesser amount, with T- to E-MORB and arc tholeites. The least evolved rocks of the Ashizuri complex are enriched in light rare earth elements ((La/Yb)n = 8-16) and other incompatible elements (e.g., Ba/La ≅ 11-13; Ba/Nb ≅ 9-11), features of intra-plate alkali basalts. These features are also characteristic of the more evolved rocks of acidic composition. Trace element petrogenetic modelling suggests that all the different components of the suite are co-magmatic and points out the major role of crystal fractionation process in its genesis. Sr and Nd isotopic data (εNdi = -0.59 to +2.56; εSri = -9.19 to + 2.90) suggest that assimilation as well as crystal fractionation occurred. Derivation through mixing of a MORB-like source and an old enriched component (e.g., sediment or old crust), or through partial melting of lower crust cannot explain both the elemental and isotopic signature of the Ashizuri suite. An OIB-type enriched mantle source is required. By comparison with volcanic rocks in southwest Japan and in the neighbouring Philippine Sea oceanic plate, this source is believed to lie not in the sub-Japan lithosphere but deeper in the asthenosphere prevalent under Japan and the Philippine Sea Plate. (authors). 83 refs., 8 figs., 7 tabs

  10. Quaternary volcanism in Deception Island (Antarctica): South Shetland Trench subduction-related signature in the Bransfield Basin back arc domain

    Deception Island shows a volcanism related to the Phoenix Plate subduction and roll-back under South Shetland Block in the present times. The development of the island is related to the evolution and collapse of a volcanic caldera, and this study is focused on the petrology, mineralogy and geochemistry of the post-caldera rocks. We have made a study of the lava flows, dikes and the youngest historic eruption in 1970. These rocks range from dacite to rhyolite and have a microporphyritic texture with olivine and minor clinopyroxene. A pre-caldera basaltic andesite has also been studied. It has a microporphyritic texture with clinopyroxene. The intermediate and acid compositions alternating in the volcanostratigraphic sequence suggest either mafic recharge events or melt extraction from different levels in the deep magmatic system. All the studied compositions share a subduction-related signature similar to other magmatics from the Bransfield Basin. However, compositional differences between pre-caldera and post-caldera rocks indicate a different magma source and depth of crystallisation. According to the geothermobarometric calculations the pre-caldera magmas started to crystallise at deeper levels (13.5-15 km) than the post-caldera magmas (6.2-7.8 km). Specifically, the postcaldera magmas indicate a smaller influence of the subducting slab in the southwestern part of the Bransfield Basin in respect to the available data from other sectors as well as the involvement of crustal contamination in the genesis of the magmas. (Author)

  11. Observations of Seafloor Outcrops in the Oblique Subduction Setting of Adak Canyon: Implications for Understanding the Early History of the Aleutian Island Arc

    Yogodzinski, G.; Scholl, D.; Jicha, B.; Wyatt, C.; Singer, B.; Kelemen, P.


    Submarine canyons in the western Aleutians (west of 177°W) are formed by oblique subduction, which has broken crustal blocks away from the arc massif and rotated them in clockwise sense, resulting in the formation of triangular-shaped summit basins and deep, structurally controlled submarine canyons (Geist et al., Tectonics v7, p327, 1988). A series of dives with the ROV Jason II on July 28-30, 2004 on Adak Canyon has provided the first-ever view of seafloor outcrops in an Aleutian canyon formed by this process. Two dives on the canyon's steep eastern wall revealed extensive exposures of blocky outcrops of volcanic rock at depths of 2900-1500 m. Samples of these units collected by the Jason II are a mixture of dark, pyroxene and plagioclase-phyric lavas and volcaniclastics. Degree of weathering/alteration is highly variable but some samples appear fresh. We anticipate that these rocks are offshore-equivalents of the Finger Bay Volcanics, which represent the earliest phase of Aleutian volcanism exposed on nearby Adak Island (e.g., Coats, 1956, USGS Bull. 1028-C). Exposures of granitic rock in Adak Canyon form low ledges of exfoliating outcrop interspersed with spheroidally weathered, bouldery sub-crop, in the depth range of 1800-1600 meters. Obtaining in-situ samples from these massive and subrounded exposures was not possible with the Jason II, but recovery of large, sub-angular slabs that litter the surface included samples of fresh diorite, fine-grained felsic intrusives and hydrothermally altered volcanic country rock. The stratigraphically highest exposures observed in Adak Canyon are gently dipping, poorly lithified `Middle Series' sedimentary rocks of probable Miocene-Oligocene age. All outcrop surfaces in Adak Canyon are covered with a uniformly dark brown, opaque coating of Mn oxide less than 1mm thick. Well-rounded cobbles and boulders interpreted to be glacial drift are largely free of Mn oxide coatings. Thick pavements of Mn-oxide were not observed

  12. A new contribution to the Late Quaternary tephrostratigraphy of the Mediterranean: Aegean Sea core LC21

    Satow, C.; Tomlinson, E. L.; Grant, K. M.; Albert, P. G.; Smith, V. C.; Manning, C. J.; Ottolini, L.; Wulf, S.; Rohling, E. J.; Lowe, J. J.; Blockley, S. P. E.; Menzies, M. A.


    Tephra layers preserved in marine sediments can contribute to the reconstruction of volcanic histories and potentially act as stratigraphic isochrons to link together environmental records. Recent developments in the detection of volcanic ash (tephra) at levels where none is macroscopically visible (so-called 'crypto-tephra') have greatly enhanced the potential of tephrostratigraphy for synchronising environmental and archaeological records by expanding the areas over which tephras are found. In this paper, crypto-tephra extraction techniques allow the recovery of 8 non-visible tephra layers to add to the 9 visible layers in a marine sediment core (LC21) from the SE Aegean Sea to form the longest, single core record of volcanic activity in the Aegean Sea. Using a novel, shard-specific methodology, sources of the tephra shards are identified on the basis of their major and trace element single-shard geochemistry, by comparison with geochemical data from proximal Mediterranean volcanic stratigraphies. The results indicate that the tephra layers are derived from 14 or 15 separate eruptions in the last ca 161 ka BP: 9 from Santorini; 2 or 3 from Kos, Yali, or Nisyros; 2 from the Campanian province; and one from Pantelleria. The attributions of these tephra layers indicate that 1) inter-Plinian eruptions from Santorini may have produced regionally significant tephra deposits, 2) marine tephrostratigraphies can provide unique and invaluable data to eruptive histories for island volcanoes, and 3) tephra from both Pantelleria and Campania may be used to correlate marine records from the Aegean Sea to those from the Tyrrhenian, Adriatic and Ionian Seas.

  13. Geochemistry of the Ophiolite and Island-Arc Volcanic Rocks in the Mianxian-Lueyang Suture Zone,Southern Qinling and Their Tectonic Significance


    Ultrabasic rocks in the Mianxian-Lueyang ophiolitic melange zone include harzburgite and dunite which exhibit LREE depletion with remarkable positive Eu anomaly.The diabase dike swarm shows LREE enrichment but slightly negative Eu anomaly.Metamorphosed volcanic rocks can be divided into two groups in terms of their REE geochemistry and trace element ratios of Ti/V,Th/Ta,Th/Yb and Ta/Yb.One is ths MORB-type basalt with LREE depletion,representing the fragments of oceanic crust and implying an association of the MORB-type ophiolite and an ancient ocean basin between the Qinling and Yangtze plates during the Middle Paleozoic-Early Mesozoic era.The oter comprises the island-arc volcanic rocks including tholeiitic basalt and a large amount of calc-alkaline intermediate-acic volcanic rock,which could not be the component of the ancient oceanic crust but the result of magmatism at the continental margin.This indicates that the Mianxian-Lueyang limited ocean basin had undergone a whole process of development,evolution and vanishing from Devonian-Cretaceous to Permian.And the Qinling area had becone an independent lithospheric microplate,on the southern side of which there were exhibited the tectonic characteristics of active continental margins during the Late Paleozoic-Early Mesozoic.That is to say.the Qinling cannot be simply considered as a result of collision between the Yangtze and North China plates.

  14. Chemical composition and hygroscopic properties of aerosol particles over the Aegean Sea

    S. Bezantakos


    Full Text Available The chemical composition and water uptake characteristics of sub-micrometer atmospheric particles in the region of the Aegean Sea were measured between 25 August and 11 September 2011 in the framework of the Aegean-Game campaign. High time-resolution measurements of the chemical composition of the particles were conducted using an airborne compact Time-Of-Flight Aerosol Mass Spectrometer (cTOF-AMS. These measurements involved two flights from the island of Crete to the island of Lemnos and back. A Hygroscopic Tandem Differential Mobility Analyzer (HTDMA located on the island of Lemnos was used to measure the ability of the particles to take up water. The HTDMA measurements showed that the particles were internally mixed, having hygroscopic growth factors that ranged from 1.00 to 1.59 when exposed to 85% relative humidity. When the aircraft flew near the ground station on Lemnos, the cTOF-AMS measurements showed that the organic volume fraction of the particles ranged from 43 to 56%. These measurements corroborate the range of hygroscopic growth factors measured by the HTDMA during that time. Good closure between HTDMA and cTOF-AMS measurements was achieved when assuming that the organic species were hydrophobic and had an average density that corresponds to aged organic species. Using the results from the closure study, the cTOF-AMS measurements were employed to determine a representative aerosol hygroscopic parameter κmix for the whole path of the two flights. Calculated κmix values ranged from 0.17 to 1.03 during the first flight and from 0.15 to 0.93 during the second flight. Air masses of different origin as determined by back trajectory calculations can explain the spatial variation in the chemical composition and κmix values of the particles observed in the region.

  15. Greek Islands, Western Asia Minor as seen from STS-58


    This north-looking view shows the western margin of Turkey (right) and the Dodecanese Islands of Greece between the Aegean Sea (left) and the Sea of Crete (foreground). The largest island is Crete (foreground) with the semicircular island of Thira beyond. Thira is dominated by the volcanoe Santorini. Two airplane contrails appear between the Turkish mainland and the large island of Rhodes immediately offshore. The narrow straits of the Dardanelles, joining the Black Sea to the Mediterranean, can be detected top left.

  16. High resolution seismic data coupled to Multibeam bathymetry of Stromboli island collected in the frame of the Stromboli geophysical experiment: implications with the marine geophysics and volcanology of the Aeolian Arc volcanic complex (Sicily, Southern Tyrrhenian sea, Italy).

    Aiello, Gemma; Di Fiore, Vincenzo; Marsella, Ennio; Passaro, Salvatore


    New high resolution seismic data (Subbottom Chirp) coupled to high resolution Multibeam bathymetry collected in the frame of the Stromboli geophysical experiment aimed at recording active seismic data and tomography of the Stromboli Island are here presented. The Stromboli geophysical experiment has been already carried out based on onshore and offshore data acquisition in order to investigate the deep structure and the location of the magma chambers of the Stromboli volcano. A new detailed swath bathymetry of Stromboli Island is here shown and discussed to reconstruct an up-to-date morpho-bathymetry and marine geology of the area compared to the volcanologic setting of the Aeolian Arc volcanic complex. Due to its high resolution the new Digital Terrain Model of the Stromboli Island gives interesting information about the submerged structure of the volcano, particularly about the volcano-tectonic and gravitational processes involving the submarine flanks of the edifice. Several seismic units have been identified based on the geologic interpretation of Subbottom Chirp profiles recorded around the volcanic edifice and interpreted as volcanic acoustic basement pertaining to the volcano and overlying slide chaotic bodies emplaced during its complex volcano-tectonic evolution. They are related to the eruptive activity of Stromboli, mainly poliphasic and to regional geological processes involving the intriguing geology of the Aeolian Arc, a volcanic area still in activity and needing improved research interest. PMID:24860717

  17. Physical and chemical processes of air masses in the Aegean Sea during Etesians: Aegean-GAME airborne campaign

    Tombrou, M.; Bossioli, E.; Kalogiros, J.; Allan, J. D.; Bacak, A.; Biskos, J.G.; Coe, H.; Dandou, A.; Kouvarakis, G.; Mihalopoulos, N.; Percival, C. J.; Protonotariou, A. P.; Szabó-Takács, Beáta


    Roč. 506, feb (2015), s. 201-216. ISSN 0048-9697 Institutional support: RVO:67179843 Keywords : Aegean-GAME campaign * Airborne measurements * Marine Atmospheric Boundary Layer * Turbulent fluxes * Gas and aero sol composition * Etesian winds Subject RIV: EH - Ecology, Behaviour Impact factor: 4.099, year: 2014

  18. A juvenile oceanic island arc origin for the Archean (ca. 2.97 Ga) Fiskenæsset anorthosite complex, southwestern Greenland: Evidence from oxygen isotopes

    Polat, Ali; Longstaffe, Fred J.


    The Archean (ca. 2.97 Ga) Fiskenæsset layered intrusion, southwestern Greenland, consists of an association of anorthosite, leucogabbro, gabbro, hornblendite, pyroxenite, peridotite and dunite. The intrusion is characterized by well-preserved igneous layering, cumulate texture and primary igneous minerals including olivine, pyroxene, plagioclase, hornblende and chromite. We use new whole-rock (n=36) and mineral (n=32) oxygen isotopic data for all major lithologic units from the best preserved stratigraphic section of the Fiskenæsset Complex at Majorqap qâva to revisit geodynamic and petrogenetic hypotheses proposed for the origin of Archean terranes. The Fiskenæsset Complex has modern mantle-like whole-rock O-isotope compositions (δO18=5.8±0.5‰). Average δO18 values increase from peridotite (δO18=5.0‰), through hornblendite (δO18=5.7‰), gabbro (δO18=5.8‰), pyroxene hornblendite (δO18=6.0‰) and leucogabbro (δO18=6.3‰), to anorthosite (δO18=6.3‰). These whole-rock isotopic compositions reflect the approximate modal abundances of olivine (average δO18=4.9‰), hornblende (average δO18=5.7‰), clinopyroxene (average δO18=6.4‰) and plagioclase (average δO18=6.4‰) in each rock type, as a consequence of mineral fractionation in the magma chamber(s). Field relationships and the absence of crustal contamination suggest that the Fiskenæsset Complex formed in an oceanic setting. Subduction zone-like whole-rock trace element signatures and mantle-like δO18 and initial εNd values are consistent with formation of these rocks in a juvenile oceanic island arc setting. Field and geochemical data from the Fiskenæsset region and adjacent terranes suggest that the origin of Archean crust in southwestern Greenland is consistent with Phanerozoic-like plate tectonic processes rather than density-driven sinking, delamination and diapiric processes requiring formation of greenstone belts and anorthosite complexes on pre-existing continental crust

  19. Modeling the buoyancy-driven Black Sea Water outflow into the North Aegean Sea

    Nikolaos Kokkos


    Full Text Available A three-dimensional numerical model was applied to simulate the Black Sea Water (BSW outflux and spreading over the North Aegean Sea, and its impact on circulation and stratification–mixing dynamics. Model results were validated against satellite-derived sea surface temperature and in-situ temperature and salinity profiles. Further, the model results were post-processed in terms of the potential energy anomaly, ϕ, analyzing the factors contributing to its change. It occurs that BSW contributes significantly on the Thracian Sea water column stratification, but its signal reduces in the rest of the North Aegean Sea. The BSW buoyancy flux contributed to the change of ϕ in the Thracian Sea by 1.23 × 10−3 W m−3 in the winter and 7.9 × 10−4 W m−3 in the summer, significantly higher than the corresponding solar heat flux contribution (1.41 × 10−5 W m−3 and 7.4 × 10−5 W m−3, respectively. Quantification of the ϕ-advective term crossing the north-western BSW branch (to the north of Lemnos Island, depicted a strong non-linear relation to the relative vorticity of Samothraki Anticyclone. Similar analysis for the south-western branch illustrated a relationship between the ϕ-advective term sign and the relative vorticity in the Sporades system. The ϕ-mixing term increases its significance under strong winds (>15 m s−1, tending to destroy surface meso-scale eddies.

  20. Wind Atlas of Aegean Sea with SAR data

    Bingöl, Ferhat; Hasager, Charlotte Bay; Badger, Merete;


    The Global Wind Atlas project is established to create a “free-to-use” wind atlas of the whole globe. The modelling chain of the project includes micro-scale models and new reanalysis datasets. Local measurements are planed to be use for test and validation. Unfortunately, it is not always possible...... satellite radar technologies made it possible to use Synthetic Aperture Radars (SAR) for wind speed and direction measurements at offshore locations. In this study, a new technique of making wind atlases is applied to the region of Aegean Sea is presented. The method has been tested and validated in the...... to find long term offshore measurement to make wind statistics. The main reason is the cost of setup and maintenance of an offshore mast. One of the regions which has high potential in wind resources but so far is without any long term offshore measurement is the Aegean sea. Recent developments in...

  1. Velocity and deformation fields in the North Aegean domain, Greece, and implications for fault kinematics, derived from GPS data 1993-2009

    Müller, M. D.; Geiger, A.; Kahle, H.-G.; Veis, G.; Billiris, H.; Paradissis, D.; Felekis, S.


    GPS rates based on data of an extended continuous and campaign-type GPS network in the North Aegean domain are presented. The data processed for the time period 1993-2009 is used to analyze the complex kinematic and deformation fields in the North Aegean Sea and adjacent regions. The presence of slowly deforming areas is investigated. Southern Bulgaria, eastern Macedonia and Thrace move uniformly southward relative to Eurasia (1.5-3.5 mm/yr). Western Macedonia, Epirus, Thessaly and Central Greece rotate rather coherently clockwise. The region comprising the islands of Limnos, Agios Efstratios and Alonnisos moves like a counterclockwise rotating slowly deforming block. The new GPS rates allow a quantification of the spatial change of strike-slip motion and locking depth along the North Aegean trough. Dextral strike-slip motion diminishes from east toward west amounting to 21.2 mm/yr along the Saros basin and 12.5 mm/yr south of the Chalkidiki peninsula. Less than 5 mm/yr (50 nstrain/yr shear strain rate) is transferred from the Sporades islands/Pelion toward Northern Evia. The locking depth is shallow for the Ganos fault and the western Saros basin (5.6-8.9 km). It is deeper between the Sporades islands and Pelion (~ 17.7 km) corresponding to a more diffuse shear zone. An elementary finite element model is applied to derive slip rates of the three main ENE-WSW to NE-SW trending dextral strike-slip faults in the North Aegean. Large-scale N-S to NNE-SSW extension in the North Aegean domain is analyzed by employing finite element and GPS based strain rate analyses. Pronounced extension (> 100 nstrain) is associated with known tectonic structures (e.g., Mygdonian graben, northern Gulf of Evia). In offshore areas such as the Sporades basin the correspondence between GPS derived extension rates and active fault structures is not entirely evident. However, important constraints are provided for seismotectonic interpretations.




    For the numerous métiers of the small scale fisheries in the North-Eastern Aegean sea (Lesvos and Limnos isl.), herein we present the catch composition per métier, the fishing effort and the estimation of total production. Daily logbooks were distributed to 20 professional coastal fishermen to record for a one year period their fishing activity. In total, 68 type of fisheries were reported, grouped in 20 different métiers...


    Nick Kardulias


    Full Text Available Aegean societies in the third and second millennia B.C. developed complex economics based on the accumulation of substantial agricultural surpluses, craft specialization, and intricate distribution systems. The trade items included both utilitarian and luxury goods. To place these activities in a proper context, this paper initially evaluates the world systems literature as it relates to antiquity. The paper then presents some specific evidence to support the contention that the Aegean BA economy was an adjunct to an Eastern Mediterranean world system. While Wallerstein's model offers valuable insights into the operation of trade networks, his approach has certain limitations. The paper explores some of these limitations, in particular the absence of periphery dependence on core areas that is a hallmark of modern capitalist systems, discusses revisions suggested by other scholars, and demonstrates the validity of the altered model with data from the Aegean. The evidence suggests the existence of a system with local, intraregional, and extraregional components. Finally, the paper also suggests that the world systemsapproach needs to place greater emphasis on production, not just exchange, as the crucial nexus of economic activity.

  4. Modeling of the upwelling hydrodynamics in the Aegean Sea



    Full Text Available The special features of the hydrodynamic circulation in the Aegean Sea referring to the development of regional upwelling coastal zones are studied by means of a mathematical model. The modeling effort is focused on the tracing of coastal areas, where upwelling events are frequently observed during the summer meteorological conditions. These areas are characterized by the enrichment of surface waters with nutrients and, consequently, increased fish production. The phenomenon is studied by the use of a two-layer mathematical model comprising the surface heated zone and the rest of the water column. The numerical solution of the model is based on the finite differences method. The wind shear applied over the stratified basin, with predefined density stratification and initial water-layers thickness, and the gravity and Coriolis forces taken into account, constitute the basic external factors for the generation of the hydrodynamic circulation in the area of the Aegean Sea. The calibration and the validation of the model are performed by the comparison of the model output to the data and observations reported in valid scientific sources. The aim of the paper is to demonstrate the significant contribution of numerical models to the better understanding of the hydrodynamics governing the Aegean water circulation as well as the tracing of upwelling zones.

  5. The Aegean Sea marine security decision support system

    L. Perivoliotis


    Full Text Available As part of the integrated ECOOP (European Coastal Sea Operational observing and Forecasting System project, HCMR upgraded the already existing standalone Oil Spill Forecasting System for the Aegean Sea, initially developed for the Greek Operational Oceanography System (POSEIDON, into an active element of the European Decision Support System (EuroDeSS. The system is accessible through a user friendly web interface where the case scenarios can be fed into the oil spill drift model component, while the synthetic output contains detailed information about the distribution of oil spill particles and the oil spill budget and it is provided both in text based ECOOP common output format and as a series of sequential graphics. The main development steps that were necessary for this transition were the modification of the forcing input data module in order to allow the import of other system products which are usually provided in standard formats such as NetCDF and the transformation of the model's calculation routines to allow use of current, density and diffusivities data in z instead of sigma coordinates. During the implementation of the Aegean DeSS, the system was used in operational mode in order support the Greek marine authorities in handling a real accident that took place in North Aegean area. Furthermore, the introduction of common input and output files by all the partners of EuroDeSS extended the system's interoperability thus facilitating data exchanges and comparison experiments.

  6. Stochastic strong ground motion simulations for the intermediate-depth earthquakes of the south Aegean subduction zone

    Kkallas, Harris; Papazachos, Konstantinos; Boore, David; Margaris, Vasilis


    We have employed the stochastic finite-fault modelling approach of Motazedian and Atkinson (2005), as described by Boore (2009), for the simulation of Fourier spectra of the Intermediate-depth earthquakes of the south Aegean subduction zone. The stochastic finite-fault method is a practical tool for simulating ground motions of future earthquakes which requires region-specific source, path and site characterizations as input model parameters. For this reason we have used data from both acceleration-sensor and broadband velocity-sensor instruments from intermediate-depth earthquakes with magnitude of M 4.5-6.7 that occurred in the south Aegean subduction zone. Source mechanisms for intermediate-depth events of north Aegean subduction zone are either collected from published information or are constrained using the main faulting types from Kkallas et al. (2013). The attenuation parameters for simulations were adopted from Skarladoudis et al. (2013) and are based on regression analysis of a response spectra database. The site amplification functions for each soil class were adopted from Klimis et al., (1999), while the kappa values were constrained from the analysis of the EGELADOS network data from Ventouzi et al., (2013). The investigation of stress-drop values was based on simulations performed with the EXSIM code for several ranges of stress drop values and by comparing the results with the available Fourier spectra of intermediate-depth earthquakes. Significant differences regarding the strong-motion duration, which is determined from Husid plots (Husid, 1969), have been identified between the for-arc and along-arc stations due to the effect of the low-velocity/low-Q mantle wedge on the seismic wave propagation. In order to estimate appropriate values for the duration of P-waves, we have automatically picked P-S durations on the available seismograms. For the S-wave durations we have used the part of the seismograms starting from the S-arrivals and ending at the

  7. Microhabitat choice in island lizards enhances camouflage against avian predators

    Marshall, Kate L A; Philpot, Kate E.; Martin Stevens


    Camouflage can often be enhanced by genetic adaptation to different local environments. However, it is less clear how individual behaviour improves camouflage effectiveness. We investigated whether individual Aegean wall lizards (Podarcis erhardii) inhabiting different islands rest on backgrounds that improve camouflage against avian predators. In free-ranging lizards, we found that dorsal regions were better matched against chosen backgrounds than against other backgrounds on the same island...

  8. Re-distribution of 137Cs Chernobyl signal in the Aegean Sea

    The present levels of 137Cs in the water column of the Aegean Sea are at all depths, significantly higher than in the pre-Chernobyl period. The concentrations in surface and intermediate water show a linear relationship to salinity, indicating that mixing of Black Sea Water with highly saline waters of Levantine origin is the main process controlling 137Cs levels. The present 137Cs concentrations in deep basins of the North and South Aegean (3.7 - 5.5 Bq m-3) are the highest in the deep waters of the Mediterranean Sea. In the North Aegean the transfer of 137Cs from the surface layers to the bottom took place through the dense water formation events in 1987 and 1993. The 137Cs levels in the deep South Aegean are higher than expected, possibly in relation to a contribution of N-Aegean deep waters. (author)

  9. Oil pollution in the surface water of the Aegean Sea

    Öztürk, Bayram; Güven, Kasim C.; Nesimigil, Filiz; Cumali, Selin; Dede, Ayhan


    Abstract Oil pollution in the surface water of the Aegean Sea was investigated from the Çanakkale Strait (Dardanelles) to the Marmaris Harbour, during 17-25 April in 2005. The oil pollution of samples was determined by UVF, through various crude oils and also chrysene as references materials. The oil pollution in water was ranged from 6.17 μg/L at Datca to 59.58 μg/L at Kusadasi through Russian crude oil equivalent. The highest polluted areas were Babakale-Kusadasi Bay, West of Giadoros Islan...

  10. Origin of primitive ultra-calcic arc melts at crustal conditions - Experimental evidence on the La Sommata basalt, Vulcano, Aeolian Islands

    Lanzo, Giovanni; Di Carlo, Ida; Pichavant, Michel; Rotolo, Silvio G.; Scaillet, Bruno


    To interpret primitive magma compositions in the Aeolian arc and contribute to a better experimental characterization of ultra-calcic arc melts, equilibrium phase relations have been determined experimentally for the La Sommata basalt (Som-1, Vulcano, Aeolian arc). Som-1 (Na2O + K2O = 4.46 wt.%, CaO = 12.97 wt.%, MgO = 8.78 wt.%, CaO/Al2O3 = 1.03) is a reference primitive ne-normative arc basalt with a strong ultra-calcic affinity. The experiments have been performed between 44 and 154 MPa, 1050 and 1150 °C and from NNO + 0.2 to NNO + 1.9. Fluid-present conditions were imposed with H2O-CO2 mixtures yielding melt H2O concentrations from 0.7 to 3.5 wt.%. Phases encountered include clinopyroxene, olivine, plagioclase and Fe-oxide. Clinopyroxene is slightly earlier than olivine in the crystallization sequence. It is the liquidus phase at 150 MPa, being joined by olivine on the liquidus between 44 and 88 MPa. Plagioclase is the third phase to appear in the crystallization sequence and orthopyroxene was not found. Experimental clinopyroxenes (Fs7-16) and olivines (Fo78-92) partially reproduce the natural phenocryst compositions (respectively Fs5-7 and Fo87-91). Upon progressive crystallization, experimental liquids shift towards higher SiO2 (up to ~ 55 wt.%), Al2O3 (up to ~ 18 wt.%) and K2O (up to ~ 5.5 wt.%) and lower CaO, MgO and CaO/Al2O3. Experimental glasses and natural whole-rock compositions overlap, indicating that progressive crystallization of Som-1 type melts can generate differentiated compositions such as those encountered at Vulcano. The low pressure cotectic experimental glasses reproduce glass inclusions in La Sommata clinopyroxene but contrast with glass inclusions in olivine which preserve basaltic melts more primitive than Som-1. Phase relations for the La Sommata basalt are identical in all critical aspects to those obtained previously on a synthetic ultra-calcic arc composition. In particular, clinopyroxene + olivine co-saturation occurs at very low

  11. The latest aspects of telluric and electromagnetic variations associated with shallow and intermediate depth earthquakes in the South Aegean

    M. Bakatsakis


    Full Text Available Recent observations of telluric and electromagnetic field variations (radioemissions assocuated with shallow and intermediate depth earthquakes in the South Aegean are presented. A telemetric system, installed on Crete Island, which continuously records the telluric and electromagnetic field variations is described. In the field stations of the system we measure both the telluric variations (using an appropriate electric dipole configuration and the horizontal electric component of the electromagnetic field in 3 kHz, 10 hKz, 41 MHz and 53 MHz (using tuned and l/2 antennas respectively. Furthermore, a theoretical model is given on the generation and the form of preseismic telluric variations based on the charge dislocation model.

  12. Spectroscopic studies of humic acids from subsurface sediment samples collected across the Aegean Sea



    Full Text Available Natural humic acids are biogenic, structurally complex and heterogeneous, refractory, acidic, yellow-to black-coloured organic polyelectrolytes of relatively high molecular weight. They occur in all soils, sediments, fresh waters, and seawaters. Humic acids represent the largest portion of nonliving soil organic matter. In the present paper, humic substances were isolated from marine subsurface sediment samples collected across the Aegean sea (in Greece and especially from a marine area extending northwards of the Samothraki plateau towards the north-eastern part of the island of Crete. In a following step, humic preparations were studied using infrared and fluorescence spectroscopy (emission, excitation and synchronous-scan excitation spectra were obtained. The infrared spectra suggested functional chemical groups such as as OH-, C-H aliphatic, C=C, C=O/COO-, salts of carboxylic acids, and also, in some cases, silicate anions or C-O from alcohols, esters and ethers. Fluorescence emission, excitation and synchronous scan excitation provided some valuable information concerning a probable origin (marine and/or terrestrial for the isolated humics.

  13. Macrobenthic community structure over the continental margin of Crete (South Aegean Sea, NE Mediterranean)

    Tselepides, Anastasios; Papadopoulou, Konstantia-N.; Podaras, Dimitris; Plaiti, Wanda; Koutsoubas, Drosos


    Macrobenthic faunal composition, abundance, biomass and diversity together with a suite of sedimentary environmental parameters were investigated on a seasonal basis in order to determine factors regulating faunal distribution over the oligotrophic continental margin of the island of Crete (South Aegean Sea, North Eastern Mediterranean). Macrofaunal species composition was similar to that of the western Mediterranean and the neighboring Atlantic having several common dominant species. Mean benthic biomass, abundance and diversity decreased with depth, with a major transition zone occurring at 540 m, beyond which values declined sharply. At comparable depths biomass and abundance values were considerably lower to those found in the Atlantic, high-lighting the extreme oligotrophy of the area. The continental margin of Crete was characterised by a high diversity upper continental shelf environment (dominated by surface deposit feeding polychaetes) and a very low diversity slope and deep-basin environment (dominated by carnivorous and filter feeding polychaetes). Classification and ordination analyses revealed the existence of four principle clusters divided by a faunal boundary between 200 and 540 m, as well as beyond 940 m depth. Significant correlations between macrofauna and sediment parameters led to the conclusion that besides depth, food availability (as manifested by the concentration of chloroplastic pigments) is the principle regulating factor in the system. Such being the case, the prevailing hydrographic features that structure the pelagic food web and are directly responsible for the propagation of organic matter to the benthos also affect its community structure.

  14. 210Po activity concentrations in mussels at Aegean Turkish Coast

    In Turkey mussels (Mytilus galloprovincialis) are consumed in relatively large quantities. Therefore, analyses of mussel samples from different sampling sites in Aegean Sea were performed in order to evaluate the ingestion of 210Po and 210Pb by the Turkey population. Polonium analyses were performed with a complete dissolution of the sample in mineral acids. Polonium isotopes were plated onto a copper discs in 0.5 M HCl solution in the presence of ascorbic acid using a technique modified from Flynn (1968). The alpha activity measurements of polonium isotopes plated on copper discs were performed with ZnS(Ag) detector. The highest concentrations was found in Karaburun mussels as 254 and the lowest one was at Inciralti as 18 Based on these 210Po activity concentrations, annual dose equivalent rates delivered to biological tissues in mussels would vary widely, from 136 to 10 mSv.y-1. It is concluded that in mussels living in the Aegean Sea a wide range of internal radiation dose exists and it is essentially sustained by 210Po food-chain transfer. (author)

  15. Anatomy of the Cycladic Blueschist Unit on Sifnos Island (Cyclades, Greece)

    Roche, Vincent; Laurent, Valentin; Cardello, Giovanni Luca; Jolivet, Laurent; Scaillet, Stéphane


    Since 35 Ma, the kinematics of the Aegean domain has been mainly controlled by the southward retreat of the African slab, inducing back-arc extension. The main structures and associated kinematics are well constrained, but the kinematics of deformation before 35 Ma, coeval with the exhumation of blueschists and eclogites of the Cycladic Blueschist Unit, is still poorly understood. The earlier Eocene syn-orogenic evolution is strongly debated and very different geometrical interpretations and kinematic histories have been proposed in the literature. This study focuses on the high-pressure and low-temperature (HP-LT) parageneses spectacularly exposed and well preserved on Sifnos Island. The new field work provides new structural constraints on the tectonic history of HP-LT units generated in the subduction zone during the Eocene. It further shows how lithological heterogeneities localize strain within an accretionary wedge and how the localisation of strain evolves through time during exhumation. We show, through new geological and metamorphic maps, cross-sections and analyses of kinematic indicators, that Sifnos is characterized by shallow-dipping shear zones reactivating weak zones due to competence contrasts or earlier tectonic contacts. Structures and kinematics associated with these shear zones, show a top-to-the-N to -NE ductile deformation. The lower part of the tectonic pile shows a downward gradient of shearing deformation and is actually a thick top-to-the-NE shear zone, which we name the Apollonia Shear Zone. Through time shearing deformation tends to localize downward, leaving the upper part of the subduction complex preserved from late deformation. The present-day shape and topography of the island is largely controlled by late brittle faults reworking the earlier ductile shear zones. Comparing with the nearby island of Syros, we propose a new tectono-metamorphic evolution of the Cycladic Blueschist Unit, which partly explains the different degrees of

  16. On some rarely caught fish in the southeastern Aegean Sea (Greece, Eastern Mediterranean

    Maria Corsini-Foka


    Full Text Available The marine region of the Dodecanese Islands (Greece is heavily affected by climate changes, intensification of anthropogenic interferences and biological invasions. Its ichthyofauna diversity is still poorly known, despite the development of marine research during the last decades, both in shallow and deep waters, and the increasing interest of fishermen to biodiversity knowledge and conservation. Regardless of its oligotrophic character, with only 1-3 % of the total Greek fishery production (ELSTAT, 2015, at least 60 % of the total fish species known in the Hellenic seas (510 has been recorded in the area (Papaconstantinou, 2014. Between 2009 and 2014, 14 uncommon species - Alopias superciliosus, Gymnura altavela, Aulopus filamentosus, Sudis hyalina, Gymnothorax unicolor, Ophisurus serpens, Nemichthys scolopaceus, Lophotus lacepede, Naucrates ductor, Alectis alexandrinus, Brama brama, Pomadasys incisus, Schedophilus ovalis and Mola mola - were captured. The first records of P. incisus and S. ovalis in the area significantly enlarge their known distribution in the Hellenic Aegean waters (Papaconstantinou, 2014. The capture of L. lacepede (approx. 140 cm total length in Patmos (2011 confirms the occurrence of this rare species in the Dodecanese, given that a juvenile is preserved at the Hydrobiological Station of Rhodes since the 1950s, and constitutes the third official record in the Aegean waters, after Gökova Bay and Chalkidiki findings (Bilecenoğlu et al., 2001; Minos et al., 2013. The captures of S. hyalina (2011 and N. scolopaceus (2014 confirm their occurrence some years after their first reports in the same area in 2004 and 2002 respectively (Corsini-Foka, 2009. The occurrence of A. superciliosus, a species infrequent in local fishery, is poorly documented in the Mediterranean and the species is considered scarce or rare in the basin (Madiraca and Davidov, 2015. The scattered records of the remaining above species contribute to monitor

  17. An Alternative Georoute: Approaching the Geological Heritage of the SE Part of Milos Island, Greece, via Hiking, Kayaking and Snorkeling

    Mavrogonatos, Constantinos; Galanopoulos, Evangelos; Anastasatou, Marianthi; Chadjimpaloglou, Petros; Xydous, Stamatios


    Milos Island is located at the southwest edge of the Cyclades island complex, in the central part of the Aegean archipelago. It is part of the modern South Aegean Volcanic Arc (SAVA), which belongs to the Hellenic subduction zone. This on-going process has resulted in the coexistence of complex geological formations and geodynamic phenomena with sceneries of incomparable natural beauty, in many areas along the arc. Among them, Milos Island is widely known to be a place of astonishing geological and natural wealth, combined with a cultural heritage that dates back to the 8th millennium BC. As geotourism has been rapidly evolving worldwide over the last years, Milos Island was among the first places in Greece that developed a network of geotrails and featured many sites of special interest in terms of geology, volcanology and geoarchaeology. This study proposes an original georoute through land and sea, which aims t? emerge both overland and underwater areas of special interest. It is a novel way to approach the geological and cultural wealth of Milos and focuses on the Aghia Kiriaki area, at the South part of the island. This alternative georoute includes hiking, kayaking and snorkeling, and anyone who follows it, can be guided to a significant number of important geological, volcanic, morphological and geoarcheological sites, in a relatively narrow area, combining athletic activities as well. The proposed georoute has a total length of 3,2 km and an estimated time of completion of about 4 hours. It starts from Aghia Kiriaki area, where visitors can see remnants of one of the island's collapsed calderic domes in a panoramic view towards the East. In the same site, volcanic emanations create impressive scenery, which introduces the participants to aspects of the island's geologic and volcanic history. After about 800 meters of hiking, throughout an area that is dominated by products of phreatic eruptions, Aghia Kiriaki beach is the next stop. Impressive findings of

  18. Early farmers from across Europe directly descended from Neolithic Aegeans.

    Hofmanová, Zuzana; Kreutzer, Susanne; Hellenthal, Garrett; Sell, Christian; Diekmann, Yoan; Díez-Del-Molino, David; van Dorp, Lucy; López, Saioa; Kousathanas, Athanasios; Link, Vivian; Kirsanow, Karola; Cassidy, Lara M; Martiniano, Rui; Strobel, Melanie; Scheu, Amelie; Kotsakis, Kostas; Halstead, Paul; Triantaphyllou, Sevi; Kyparissi-Apostolika, Nina; Urem-Kotsou, Dushka; Ziota, Christina; Adaktylou, Fotini; Gopalan, Shyamalika; Bobo, Dean M; Winkelbach, Laura; Blöcher, Jens; Unterländer, Martina; Leuenberger, Christoph; Çilingiroğlu, Çiler; Horejs, Barbara; Gerritsen, Fokke; Shennan, Stephen J; Bradley, Daniel G; Currat, Mathias; Veeramah, Krishna R; Wegmann, Daniel; Thomas, Mark G; Papageorgopoulou, Christina; Burger, Joachim


    Farming and sedentism first appeared in southwestern Asia during the early Holocene and later spread to neighboring regions, including Europe, along multiple dispersal routes. Conspicuous uncertainties remain about the relative roles of migration, cultural diffusion, and admixture with local foragers in the early Neolithization of Europe. Here we present paleogenomic data for five Neolithic individuals from northern Greece and northwestern Turkey spanning the time and region of the earliest spread of farming into Europe. We use a novel approach to recalibrate raw reads and call genotypes from ancient DNA and observe striking genetic similarity both among Aegean early farmers and with those from across Europe. Our study demonstrates a direct genetic link between Mediterranean and Central European early farmers and those of Greece and Anatolia, extending the European Neolithic migratory chain all the way back to southwestern Asia. PMID:27274049

  19. Application of multivariate techniques to analytical data on Aegean ceramics

    The general problems of data collection and handling for multivariate elemental analyses of ancient pottery are considered including such specific questions as the level of analytical precision required, the number and type of elements to be determined and the need for comprehensive multivariate statistical analysis of the collected data in contrast to element by element statistical analysis. The multivariate statistical procedures of clustering in a multidimensional space and determination of the numerical probabilities of specimens belonging to a group through calculation of the Mahalanobis distances for these specimens in multicomponent space are described together with supporting univariate statistical procedures used at Brookhaven. The application of these techniques to the data on Late Bronze Age Aegean pottery (largely previously analysed at Oxford and Brookhaven with some new specimens considered) have resulted in meaningful subdivisions of previously established groups. (author)

  20. Arc Statistics

    Meneghetti, M; Dahle, H; Limousin, M


    The existence of an arc statistics problem was at the center of a strong debate in the last fifteen years. With the aim to clarify if the optical depth for giant gravitational arcs by galaxy clusters in the so called concordance model is compatible with observations, several studies were carried out which helped to significantly improve our knowledge of strong lensing clusters, unveiling their extremely complex internal structure. In particular, the abundance and the frequency of strong lensing events like gravitational arcs turned out to be a potentially very powerful tool to trace the structure formation. However, given the limited size of observational and theoretical data-sets, the power of arc statistics as a cosmological tool has been only minimally exploited so far. On the other hand, the last years were characterized by significant advancements in the field, and several cluster surveys that are ongoing or planned for the near future seem to have the potential to make arc statistics a competitive cosmo...

  1. Living benthic foraminifera as an environmental proxy in coastal ecosystems: A case study from the Aegean Sea (Greece, NE Mediterranean)

    Koukousioura, Olga; Dimiza, Margarita D.; Triantaphyllou, Maria V.; Hallock, Pamela


    The species composition of the epiphytic benthic foraminiferal fauna was compared at two coastal locations in the Aegean Sea. Samples were collected during August 2001 and July 2003 along the southeastern coast of Andros Island at Korthi Gulf, where there are minimal anthropogenic activities, and at Kastro Gulf, with substantial anthropogenic influence. This study represents the first application of the FORAM Index (FI), which is a single-metric index for water quality originally developed for western Atlantic reef foraminiferal assemblages, to Mediterranean assemblages. Multivariate analyses distinguished three clusters of sample sites representing three foraminiferal assemblages. Samples dominated by the mixotrophic species, A. lobifera, were collected primarily from sites along the northern coasts of both gulfs. Characteristics of this assemblage, including relatively high dominance (D = 0.27-0.51), lower Shannon-Wiener diversity (H' = 1.3-2.1) and high FI (6.6-8.2), all reflect oligotrophic environmental conditions typical of pristine waters of the Aegean Sea. A. lobifera was typically the most common species in the second assemblage, though relative abundances of heterotrophic taxa were higher, resulting in somewhat higher diversity (H' = 1.6-2.4) and lower dominance (D = 0.14-0.36). These indices, as well as the FI range of 3.5-7.0 indicated somewhat more prevalent organic carbon resources but still relatively high water quality. This assemblage was found along the southern coast of Korthi Gulf and at more interior sites in northern Kastro Gulf. The third assemblage was dominated by smaller heterotrophic species, including notable proportions of the stress-tolerant taxa Ammonia spp. and Elphidium spp., and had few or no A. lobifera. Diversity (H' = 1.4-2.0) and dominance (D = 0.22-0.47) indices were similar to those for the first assemblage, but FI values were much lower (2.0-3.4). Samples characterized by this assemblage were collected only from the southern

  2. Modeling Arcs

    Insepov, Zeke; Veitzer, Seth; Mahalingam, Sudhakar


    Although vacuum arcs were first identified over 110 years ago, they are not yet well understood. We have since developed a model of breakdown and gradient limits that tries to explain, in a self-consistent way: arc triggering, plasma initiation, plasma evolution, surface damage and gra- dient limits. We use simple PIC codes for modeling plasmas, molecular dynamics for modeling surface breakdown, and surface damage, and mesoscale surface thermodynamics and finite element electrostatic codes for to evaluate surface properties. Since any given experiment seems to have more variables than data points, we have tried to consider a wide variety of arcing (rf structures, e beam welding, laser ablation, etc.) to help constrain the problem, and concentrate on common mechanisms. While the mechanisms can be comparatively simple, modeling can be challenging.

  3. Segmentation of Aegean Fishing Fleet and Spatial Distribution of Fishing Capacity

    Ilke Kosar Danisman


    The data on fishing fleet play an important role in fisheries management. It is an effective method that collection of reliable and regular data on fleet, and these data into information that is needed in terms of fleet management. In this study, it is demonstrated that the segmentation of the Aegean fishing fleet and fishing port based spatial distribution of fishing capacities concerning each fleet segment at the Aegean coast to improve fisheries management.

  4. A review of tectonics and sedimentation in a forearc setting: Hellenic Thrace Basin, North Aegean Sea and Northern Greece

    Maravelis, A. G.; Boutelier, D.; Catuneanu, O.; Seymour, K. St.; Zelilidis, A.


    Exposure of the forearc region of the North Aegean Sea, Greece, offers insight into evolving convergent margins. The sedimentary fill of the Thrace Basin during the Late Eocene to Oligocene time provides a record of subduction-driven processes, such as growth of magmatic arcs and construction of accretionary complexes. This large sediment repository received sediment from two sources. The southern (outboard) basin margin reflects the active influence of the exhumed accretionary prism (e.g. Pindic Cordillera or Biga peninsula), while the northern (inboard) margin records the effect of the magmatic arc in the Rhodope region. The forearc basin sedimentary fills shoal upward into shallow-marine strata but are dominated mainly by deep-marine facies. The depositional trend and stacking pattern are dominated by progradational patterns. This trend, which is observed in both basin margins, is related to tectonic deformation rather than sea-level fluctuations. Additional evidence for this tectonic uplift comes from the backstripping analysis. The accretionary complex provided material into the forearc basin. This material was transported northeast and formed a sand-rich turbidity system that evolved upslope into shallow-marine deposits. Stratigraphic data indicate that this turbidity system exhibits a successive landward (inboard) migration of the depocenter. Provenance data utilizing sandstone petrography, conglomerate clast composition, and bulk-rock geochemistry suggest that this system reflects an increased influx of mafic material into the basin. Volcanic arc-derived material was transported south and east and accumulated in deep-marine settings. Both stratigraphic and provenance data indicate a seaward (outboard) migration of the basin depocenter and a significant increase in felsic detritus into the forearc.

  5. A new species of Centaurea (Asteraceae) from the island of Samothraki (NE Greece)

    Strid, Arne; Tan, Kit


    Centaurea samothracica (subgen. Acrolophus) is described and illustrated. It is known from a single locality on (subgen. ) is described and illustrated. It is known from a single locality on the North Aegean island of Samothraki, and appears most closely related to C. chalcidicaea from Mt Athos....

  6. Adakites from Solander Island, New Zealand

    The subduction related, island arc Pleistocene volcano of Solander Island in Foveaux Strait is composed of adakite, a new rock type first described from Adak Island in the Aleutian arc. Adakites are formed by the partial fusion of young oceanic crust under eclogitic facies conditions. Comparison with other adakite localities suggests that the oceanic crust presently subducting at the nearby trench may be <25 Ma old. (author). 23 refs., 5 figs., 2 tabs

  7. Geochronology and geochemistry of rhyolites from Hormuz Island, southern Iran: A new record of Cadomian arc magmatism in the Hormuz Formation

    Faramarzi, Narges Sadat; Amini, Sadraddin; Schmitt, Axel Karl; Hassanzadeh, Jamshid; Borg, Gregor; McKeegan, Kevin; Razavi, Seyed Mohammad Hosein; Mortazavi, Seyed Mohsen


    Hormuz Island, a salt-gypsum dome in the Persian Gulf in southern Iran, is a complex halotectonic melange comprising evaporites, carbonates, volcanic and volcaniclastic rocks, as well as low-grade metamorphic and sedimentary rocks. Based on trace element (including rare earth elements REE) compositions of whole rocks and zircon, Hormuz rhyolites are inferred to have formed from subduction-related magmas generated in an active continental margin setting. Ion microprobe analyses of zircon crystals yielded concordant U-Pb ages with weighted mean 206Pb/238U age of 558 ± 7 Ma (juvenile zircons in contrast to those from previous magmatic episodes or xenocrysts) along with younger and older discordant ages which likely represent Pb loss and the presence of xenocrystic domains, respectively. Trace element ratios and in particular REE patterns of juvenile zircon from Hormuz rhyolites indicate crystallization from continental crustal source rocks typical for subduction environments. The concordant 206Pb/238U zircon age agrees with ages obtained from most other structural zones of Iran which indicate regional consolidation of igneous basement during the Neoproterozoic to Early Cambrian. Furthermore, Hormuz rhyolite ages and compositions correlate with counterparts that co-evolved along the northern margin of Gondwana, and are now preserved along the southern coast of the Persian Gulf. Hormuz rhyolites erupted synchronously with the deposition of carbonates and evaporites, suggesting that volcanism occupied an extensional backarc or retroarc setting. Such depositional environments predominated in the northern Gondwana continental margin where convergent (Proto-Tethyan) and extensional (Najd) tectonic regimes coexisted.

  8. Structural Analysis for Gold Mineralization Using Remote Sensing and Geochemical Techniques in a GIS Environment: Island of Lesvos, Hellas

    Exploration for epithermal Au has been active lately in the Aegean Sea of the eastern Mediterranean Basin, both in the islands of the Quaternary arc and in those of the back-arc region. The purpose of this study was the structural mapping and analysis for a preliminary investigation of possible epithermal gold mineralization, using remotely sensed data and techniques, structural and field data, and geochemical information, for a specific area on the Island of Lesvos. Therefore, Landsat-TM and SPOT-Pan satellite images and the Digital Elevation Model (DEM) of the study area were processed digitally using spatial filtering techniques for the enhancement and recognition of the geologically significant lineaments, as well as algebraic operations with band ratios and Principal Component Analysis (PCA), for the identification of alteration zones. Statistical rose diagrams and a SCHMIDT projection Stereo Net were generated from the lineament maps and the collected field data (dip and strike measurements of faults, joints, and veins), respectively. The derived lineament map and the band ratio images were manipulated in a GIS environment, in order to study the relation of the tectonic pattern to both the alteration zoning and the geomorphology of the volcanic field of the study area. Target areas of high interest for possible mineralization also were specified using geochemical techniques, such as X-Ray Diffraction (XRD) analysis, trace-element, and fluid-inclusion analysis. Finally, preliminary conclusions were derived about possible mineralization, the type (high or low sulfidation), and the extent of mineralization, by combining the structural information with geochemical information

  9. High oxygen consumption rates in the deep layers of the North Aegean Sea (eastern Mediterranean



    Full Text Available Severe winter meteorological conditions promote dense water formation over the shelves of the North Aegean Sea. The newly formed dense water fills the deep basins of the North Aegean Sea, contributing to their ventilation and the downward transport of organic and inorganic material. The great bathymetric variability imposes limitations on the deep circulation and the communication between the various basins and makes the North Aegean Sea an appropriate area for the monitoring of oxygen consumption in the deep layers. Historical hydrographic data suggest that there was extensive production of dense water in the North Aegean Sea on two occasions during the last decade, the winters of 1987 and 1992-1993. Our data series from August 1986 to September 1989 and from March 1997 to February 1999, permitted us to follow, step by step, the oxygen consumption and the nutrient regeneration in the deep basins of the northern Aegean Sea during these periods of isolation. The organic matter reaching the bottom layer just after the deep water formation event is rich in labile and easily oxidizable material and its decomposition leads to a significant oxygen uptake during the first year of stagnation. The further decomposition of the remaining semi-labile and refractory material turns over on greater time scales, by consuming lesser amounts of oxygen. A more significant oxygen decrease is recorded in the eastern basin (Lemnos Basin of the North Aegean Trough, than in the central (Athos Basin and the western (North Sporades Basin ones and is attributed to the irregular contribution of the Black Sea Water (BSW to the water masses formed on the different shelves of the North Aegean Sea. Our results and the existing data on the Turkish straits showed that dissolved organic matter is the major constituent responsible for this high oxygen consumption. The slightly different particulate organic carbon fluxes to these depressions play a secondary role.

  10. Statistical study of epicentre alignment in the broader Aegean area

    E. Papadirnitriou


    Full Text Available Accurate data concerning shallow (h = 60 km earthquakes (Ms =4.5 that occurred in the broader Aegean area are used to point out the presence of linear seismogenic structures (seismolineaments. The earthquake data were analyzed by the use of a specific algorithm, and the directions of the best alignment of epicentres were found. The algorithm is based on statistical criteria applied within a circular area with the aim of searching for the best direction of alignment; this is then tested, to discriminate whether or not the pattern could stem from a random distribution of epicentres, or whether it is effectively the result of a linear seismic structure; the procedure is repeated to cover the whole area examined. The resulting lineaments can be regarded as individual tectonic units, as they usually coincide with known active faults or fault systems. An interpretation is given of the spatio-temporal evolution of the seismicity along the lineaments in terms of the asperity model.

  11. Bermuda 1 arc-second Coastal Digital Elevation Model

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1 arc-second Bermuda DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the islands of Bermuda...

  12. Bermuda 3 arc-second Coastal Digital Elevation Model

    National Oceanic and Atmospheric Administration, Department of Commerce — The 3 arc-second Bermuda DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the islands of Bermuda...

  13. Tsunami hazard assessment for the island of Rhodes, Greece

    Pagnoni, Gianluca; Armigliato, Alberto; Zaniboni, Filippo; Tinti, Stefano


    The island of Rhodes is part of the Dodecanese archipelago, and is one of the many islands that are found in the Aegean Sea. The tectonics of the Rhodes area is rather complex, involving both strike-slip and dip-slip (mainly thrust) processes. Tsunami catalogues (e.g. Papadopulos et al, 2007) show the relative high frequency of occurrence of tsunamis in this area, some also destructive, in particular between the coasts of Rhodes and Turkey. In this part of the island is located the town of Rhodes, the capital and also the largest and most populated city. Rhodes is historically famous for the Colossus of Rhodes, collapsed following an earthquake, and nowadays is a popular tourist destination. This work is focused on the hazard assessment evaluation with research performed in the frame of the European project NearToWarn. The hazard is assessed by using the worst-credible case scenario, a method introduced and used to study local tsunami hazard in coastal towns like Catania, Italy, and Alexandria, Egypt (Tinti et al., 2012). The tsunami sources chosen for building scenarios are three: two located in the sea area in front of the Turkish coasts where the events are more frequent represent local sources and were selected in the frame of the European project NearToWarn, while one provides the case of a distant source. The first source is taken from the paper Ebeling et al. (2012) and modified by UNIBO and models the earthquake and small tsunami occurred on 25th April 1957.The second source is a landslide and is derived from the TRANSFER Project "Database of Tsunamigenic Non-Seismic Sources" and coincides with the so-called "Northern Rhodes Slide", possibly responsible for the 24th March 2002 tsunami. The last source is the fault that is located close to the island of Crete believed to be responsible for the tsunami event of 1303 that was reported to have caused damage in the city of Rhodes. The simulations are carried out using the finite difference code UBO-TSUFD that

  14. Chronology for the Aegean Late Bronze Age 1700-1400 B.C.

    Manning, Sturt W; Ramsey, Christopher Bronk; Kutschera, Walter; Higham, Thomas; Kromer, Bernd; Steier, Peter; Wild, Eva M


    Radiocarbon (carbon-14) data from the Aegean Bronze Age 1700-1400 B.C. show that the Santorini (Thera) eruption must have occurred in the late 17th century B.C. By using carbon-14 dates from the surrounding region, cultural phases, and Bayesian statistical analysis, we established a chronology for the initial Aegean Late Bronze Age cultural phases (Late Minoan IA, IB, and II). This chronology contrasts with conventional archaeological dates and cultural synthesis: stretching out the Late Minoan IA, IB, and II phases by approximately 100 years and requiring reassessment of standard interpretations of associations between the Egyptian and Near Eastern historical dates and phases and those in the Aegean and Cyprus in the mid-second millennium B.C. PMID:16645092

  15. Islands in the Midst of the World


    The Greek islands of the Aegean Sea, scattered across 800 kilometers from north to south and between Greece and western Turkey, are uniquely situated at the intersection of Europe, Asia and Africa. This image from the Multi-angle Imaging SpectroRadiometer includes many of the islands of the East Aegean, Sporades, Cyclades, Dodecanese and Crete, as well as part of mainland Turkey. Many sites important to ancient and modern history can be found here. The largest modern city in the Aegean coast is Izmir, situated about one quarter of the image length from the top, southeast of the large three-pronged island of Lesvos. Izmir can be located as a bright coastal area near the greenish waters of the Izmir Bay, about one quarter of the image length from the top, southeast of Lesvos. The coastal areas around this cosmopolitan Turkish city were a center of Ionian culture from the 11th century BC, and at the top of the image (north of Lesvos), once stood the ancient city of Troy.The image was acquired before the onset of the winter rains, on September 30, 2001, but dense vegetation is never very abundant in the arid Mediterranean climate. The sharpness and clarity of the view also indicate dry, clear air. Some vegetative changes can be detected between the western or southern islands such as Crete (the large island along the bottom of the image) and those closer to the Turkish coast which appear comparatively green. Volcanic activities are evident by the form of the islands of Santorini. This small group of islands shaped like a broken ring are situated to the right and below image center. Santorini's Thera volcano erupted around 1640 BC, and the rim of the caldera collapsed, forming the shape of the islands as they exist today.The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and views almost the entire globe every 9 days. This natural-color image was acquired by MISR's nadir (vertical-viewing) camera, and is a portion of the

  16. Old stories and lost pieces of the Eastern Mediterranean puzzle: a new approach to the tectonic evolution of the Western Anatolia and the Aegean Sea

    Yaltırak, Cenk; Engin Aksu, Ali; Hall, Jeremy; Elitez, İrem


    During the last 20 or so years, the tectonic evolution of Aegean Sea and Western Anatolia has been dominantly explained by back-arc extension and escape tectonics along the North Anatolian Fault. Various datasets have been considered in the construction of general tectonic models, including the geometry of fault patterns, paleomagnetic data, extensional directions of the core complexes, characteristic changes in magmatism and volcanism, the different sense of Miocene rotation between the opposite sides of the Aegean Sea, and the stratigraphy and position of the Miocene and Pliocene-Quaternary basins. In these models, the roles of the Burdur-Fethiye Shear Zone, the Trakya-Eskişehir Fault Zone, the Anaximander Mountains and Isparta Angle have almost never been taken into consideration. The holistic evaluation of numerous land and marine researches in the Aegean Sea and western Anatolia suggest the following evolutionary stages: 1. during the early Miocene, Greece and western Anatolia were deformed under the NE-SW extensional tectonics associated with the back-arc extension, when core complexes and supra-detachment basins developed, 2. following the collision of the Anaximander Mountains and western Anatolia in early Miocene , the Isparta Angle locked this side of the western arc by generating a triangle-shaped compressional structure, 3. while the Isparta Angle penetrated into the Anatolia, the NE-striking Burdur-Fethiye Shear Zone in the west and NW-striking Trakya-Eskişehir Fault Zone in the north developed along the paleo-tectonic zones , 4. the formation of these two tectonic structures allowed the counterclockwise rotation of the western Anatolia in the middle Miocene and this rotation removed the effect of the back-arc extension on the western Anatolian Block, 5. the counterclockwise rotation developed with the early westward escape of the Western Anatolian reached up to 35-40o and Trakya-Eskişehir Fault Zone created a total dextral displacement of about 200

  17. HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data



    Full Text Available A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a HF radial with CODE-type drifter radial velocities as well as (b HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

  18. Arc saw development report

    The arc saw is one of the key components of the Contaminated Equipment Volume Reduction (CEVR) Program. This report describes the progress of the arc saw from its inception to its current developmental status. History of the arc saw and early contributors are discussed. Particular features of the arc saw and their advantages for CEVR are detailed. Development of the arc saw including theory of operation, pertinent experimental results, plans for the large arc saw and advanced control systems are covered. Associated topics such as potential applications for the arc saw and other arc saw installations in the world is also touched upon

  19. Os and S isotope studies of ultramafic rocks in the Duke Island Complex, Alaska: variable degrees of crustal contamination of magmas in an arc setting and implications for Ni-Cu-PGE sulfide mineralization

    Stifter, Eric C.; Ripley, Edward M.; Li, Chusi


    The Duke Island Complex is one of the several "Ural-Alaskan" intrusions of Cretaceous age that occur along the coast of SE Alaska. Significant quantities of magmatic Ni-Cu-PGE sulfide mineralization are locally found in the complex, primarily within olivine clinopyroxenites. Sulfide mineralization is Ni-poor, consistent with petrologic evidence which indicates that sulfide saturation was reached after extensive olivine crystallization. Olivine clinopyroxenites were intruded by magmas that produced sulfide-poor, adcumulate dunites. As part of a study to investigate the potential for Ni-rich sulfide mineralization in association with the dunites, a Re-Os and S isotope study of the dunites, as well as sulfide mineralization in the olivine clinopyroxenites, was initiated. Importantly, recent drilling in the complex identified the presence of sulfidic and carbonaceous country rocks that may have been involved in the contamination of magmas and generation of sulfide mineralization. γOs (110 Ma) values of two sulfidic country rocks are 1022 and 2011. δ34S values of the country rocks range from -2.6 to -16.1 ‰. 187Os/188Os ratios of sulfide minerals in the mineralization hosted by olivine clinopyroxenites are variable and high, with γOs (110 Ma) values between 151 and 2059. Extensive interaction with Re-rich sedimentary country rocks is indicated. In contrast, γOs (110 Ma) values of the dunites are significantly lower, ranging between 2 and 16. 187Os/188Os ratios increase with decreasing Os concentration. This inverse relation is similar to that shown by ultramafic rocks from several arc settings, as well as altered abyssal dunites and peridotites. The relation may be indicative of magma derivation from a sub-arc mantle that had experienced metasomatism via slab-derived fluids. Alternatively, the relation may be indicative of minor contamination of magma by crustal rocks with low Os concentrations but high 187Os/188Os ratios. A third alternative is that the low Os

  20. Gridded bathymetry of Niihau Island, Hawaii, USA

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry shelf, bank and slope environments of Ni'ihau Island. This 5 m grid contains data between 0 and 100 meters. The netCDF and Arc ASCII grids...

  1. Cluster analysis of indermediate deep events in the southeastern Aegean

    Ruscic, Marija; Becker, Dirk; Brüstle, Andrea; Meier, Thomas


    The Hellenic subduction zone (HSZ) is the seismically most active region in Europe where the oceanic African litosphere is subducting beneath the continental Aegean plate. Although there are numerous studies of seismicity in the HSZ, very few focus on the eastern HSZ and the Wadati-Benioff-Zone of the subducting slab in that part of the HSZ. In order to gain a better understanding of the geodynamic processes in the region a dense local seismic network is required. From September 2005 to March 2007, the temporary seismic network EGELADOS has been deployed covering the entire HSZ. It consisted of 56 onshore and 23 offshore broadband stations with addition of 19 stations from GEOFON, NOA and MedNet to complete the network. Here, we focus on a cluster of intermediate deep seismicity recorded by the EGELADOS network within the subducting African slab in the region of the Nysiros volcano. The cluster consists of 159 events at 80 to 190 km depth with magnitudes between 0.2 and 4.1 that were located using nonlinear location tool NonLinLoc. A double-difference earthquake relocation using the HypoDD software is performed with both manual readings of onset times and differential traveltimes obtained by separate cross correlation of P- and S-waveforms. Single event locations are compared to relative relocations. The event hypocenters fall into a thin zone close to the top of the slab defining its geometry with an accuracy of a few kilometers. At intermediate depth the slab is dipping towards the NW at an angle of about 30°. That means it is dipping steeper than in the western part of the HSZ. The edge of the slab is clearly defined by an abrupt disappearance of intermediate depths seismicity towards the NE. It is found approximately beneath the Turkish coastline. Furthermore, results of a cluster analysis based on the cross correlation of three-component waveforms are shown as a function of frequency and the spatio-temporal migration of the seismic activity is analysed.

  2. The Plio Quaternary Ambon arc, Eastern Indonesia

    Honthaas, Christian; Maury, René C.; Priadi, Bambang; Bellon, Hervé; Cotten, Joseph


    Plio-Quaternary lavas and granites have been collected from Ambon, Seram, Kelang, Haruku, Saparua, Ambelau and Banda Api islands, Eastern Indonesia. They include low-K calc-alkaline basalts, andesites, dacites and rhyolites and high-K calc-alkaline andesites, dacites, rhyolites and granites. All these rocks present the usual chemical characteristics of island-arc magmas. The high-K suite of Ambon is mostly represented by cordierite-bearing dacites (known as ambonites) and granites. Low-K and high-K magmas were emplaced in neighbouring islands or even in the same island (Ambon), often concomitantly, during two magmatic pulses at 5-3.2 Ma and 2.3-1 Ma, respectively. We propose that the low-K suite results from the evolution of basaltic magmas derived from mantle melting above the Western Irian Jaya plate which subducts along the Seram trough. Intermediate and acidic rocks of the high-K suite (e.g. ambonites) are thought to derive from low-K mafic magmas through massive assimilation of the Seram-Ambon continental crust, as originally proposed by Van Bemmelen in 1949. The timing of magmatic events and the geochemical features of the studied lavas are clearly different from those of the southern part of the Banda arc, in which the low-K suite is lacking. In agreement with earlier seismic evidence for two different slabs subducting beneath the Seram-Ambon continental block and beneath the southern Banda arc (from Wetar to Manuk), respectively, we propose to recognise a new Plio-Quaternary island arc, i.e. the Ambon arc, extending west-east from Ambelau to the Banda Archipelago active low-K volcanoes through Kelang, southwestern Seram, Ambon, Haruku and Saparua.

  3. On the tectonic processes along the Hellenic Arc



    Full Text Available On the grounds of existing geophysical data one might be allowed lo conclude t h a t the origin of t h e stress field in the Ionian center (Ceplialonia-Zante-Patras at t h e northwestern margin of the Aegean microplate is r a t h e r shallow and in the southeastern center (Dodecanese-Crete is surely under the crust. In the area occupied by the second center of higher earthquake activity t h e relief of the Moho-discontinuity is shallower and smoother in comparison to t h a t derived from g r a v i t y and seismic d a t a for t he area of t h e northwestern center. Another difference derived from the fault-plane solutions is t h a t the Ionian center is seated in a region of horizontal pressure; the second center in the southeastern Aegean Sea belongs to a region of paramount horizontal tension. In the western side of the Hellenic arc the high sediment supply rate, combined with a thickening of the E a r t h ' s crust along the Ionian zone, is interpreted as evidence t h a t accretion has occurred there until recently or may still be occurring locally; plate consumption, if any, is rather low. The existence, 011 t h e other hand, of two very deep subparallel trenches with little fill southeast of Crete (Pliny trench, Strabo trench, combined with a very high subcrustal activity in the southeastern margin of t h e Aegean Bubplate, suggest that the subduction rate at the northern boundary of the African plate must be relatively high; 110 p l a t e accretion is expected to occur there.

  4. The influence of Black Sea Water inflow and its synoptic time-scale variability in the North Aegean Sea hydrodynamics

    Mavropoulou, Apostolia-Maria; Mantziafou, Anneta; Jarosz, Ewa; Sofianos, Sarantis


    The exchange water fluxes between the Black Sea and the North Aegean Sea through the Dardanelles Strait constitute an essential factor for the general circulation of the region. The Black Sea Water (BSW) inflow to the Aegean plays an important role in the hydrography and circulation of the basin and can affect the North Aegean deep water formation processes. Numerical experiments evaluating the influence of the time-scale variability (synoptic and seasonal) and the seasonality (period of maximum/minimum) of the Black Sea Water inflow on the dynamics of the North Aegean basin were performed. The experiments were carried out for the period from August 2008 to October 2009, using observed upper and lower-layer fluxes from the Dardanelles Strait, high-resolution atmospheric forcing, and boundary conditions derived from an operational system (ALERMO). The large-scale spatial patterns of the circulation and the seasonal variability of the North Aegean circulation show that dynamics of the basin can effectively absorb most of the Black Sea Water inflow variability. The overall cyclonic circulation of the North Aegean Sea and the predominant cyclonic and anti-cyclonic features are robust and are little affected by the different lateral fluxes. However, differences in the seasonality of the BSW inflow have an important impact in the North Aegean water column structure, while the synoptic variability observed in the Black Sea Water inflow affects the kinetic energy of the basin and the pathway of the Black Sea Water plume.

  5. Lifelong Learning and Vocational Training Programmes in Northern Aegean (Greece): Weaknesses, Possibilities and Prospects

    Giavrimis, Panagiotis; Papanis, Efstratios; Mitrellou, Sotiria; Nikolarea, Ekaterini


    This study presents, discusses and assesses the findings of a research into lifelong learning through Vocational Training Centres (VTCs) in the region of Northern Aegean, Greece. In the first part, the paper introduces its readers to the theoretical framework of lifelong education, whereas in the second part it makes a brief historical overview of…

  6. The ‘Mycenaeans’ in the south-eastern Aegean revisited

    J. Eerbeek


    The main subject of this dissertation is the Mycenaean archaeological evidence from the south-eastern Aegean. The term "Mycenaean" is typically used to refer to the dominant archaeological culture of the central and southern Greek mainland during the Late Bronze Age, which is dated between about 170

  7. ESA ResGrow: Trial cases for SAR lifting. Aegean Sea

    Badger, Merete; Hasager, Charlotte Bay; Hahmann, Andrea N.; Volker, Patrick; di Bella, Alessandro; Bingöl, Ferhat

    This report presents results related to lifting of wind maps retrieved from satellite Synthetic Aperture Radar (SAR) over the Aegean Sea. For this case study DTU Wind Energy collaborates with the Hellenic Wind Energy Association. Preliminary results have been presented to HWEA and their feedback...

  8. Structure and seismic stratigraphy of deep Tertiary basins in the northern Aegean Sea

    Beniest, Anouk; Brun, Jean-Pierre; Smit, Jeroen; Deschamps, Rémy; Hamon, Youri; Crombez, Vincent; Gorini, Christian


    Whereas active basin formation in the Aegean Sea is illustrated by seafloor bathymetry, the sedimentary and tectonic history of Tertiary basins is poorly known as existing offshore industrial seismic and well-log data are not easily accessible. We studied the evolution of the northern Aegean Sea with a focus on the North Aegean Trough and the Northern Skyros Basin, which are amongst the deepest basins of the northern Aegean domain. Structural and seismic stratigraphic interpretation of a 2D seismic dataset retrieved in the 1970's is combined with the well-investigated records of the onshore deep basins of northern Greece and Western Turkey. A general seismic signature chart was established using onshore basin stratigraphy and poorly-constrained well data. The studied domain shows two sharp unconformities that correspond to the Eocene-Oligocene transition and the Miocene-Pliocene shift, respectively. These transitions were then used as pillars for a more detailed structural and seismic stratigraphic interpretation. A NW-SE trending seismic line that cross-cuts the southern part of the NE-SW-trending North Aegean Through displays the main features that are observed in the area: 1) an overall basin geometry that is rather symmetrical; 2) pre-Pliocene units affected by steep normal faults; 3) a rather constant thickness of Oligocene sediments that define a depocenter with an apparent NW-SE orientation; 4) an ablation of Miocene sediments by erosion, likely related to the Messinian Salinity Crises (MSC); (5) thick deltaic/turbiditic deposits in the NE-SW oriented central through of Neogene age; 6) trans-tensional growth patterns in Pliocene and Quaternary sediments that combine NE-SW steeply dipping fault zones, more likely corresponding to strike-slip corridors, and E-W-trending normal faults. The evidence listed above suggest that, in the northern Aegean Sea, (1) extension started at the latest during the Late Eocene/Early Oligocene (data quality does not allow for a

  9. Assessment of SMOS Salinity and SST in the Aegean Sea (Greece) and correlations with MODIS SST measurements. Exploring the SSS and SST correlation to 137Cs inventory

    Sykioti, Olga; Florou, Heleni


    A program concept has been developed to utilize sea surface salinity (SSS) and sea surface temperature (SST) information for the inventory of artificial radionuclides, which are conservative and part of the sea salinity. As a pilot study, activity concentrations of 137Cs in the Aegean Sea (Greece) are combined to SMOS and other satellite data so as to develop an innovative tool for the remote radioactivity detection either for routine observations and emergency recordings. The presented first results are a part of an effort to attempt for the integration in space and time of field measurements to the respective satellite observations of salinity variations by model simulations, which might be also applicable for the prediction of the radiological impact of potential accidental events. The presented results involve the first assessment of SMOS SSS and SST measurements over the Aegean Sea. SMOS measurements are averaged over a surface of 40x40 sq km at an average distance of 100 km from the coastline. For this reason, totally thirty nine pixels from SMOS Level 2 data cover part of the Aegean Sea. Two time series are created that include all available measurements spanning December 2011 to current date, from descending and ascending passes, each one representing an acquisition frequency of about three days. The average SSS values in the Aegean Sea are 37-38psu following no distinct seasonal pattern. A general trend of increasing values is observed from north to south. Noise and uncertainty in the measurements are most probably due to land and RFI contamination. High island density is combined with radiofrequency interferences generated by illegal man-made emissions. The latter is a detected common issue in specific areas worldwide, such as the Mediterranean Sea. On the other hand, SST follows a clear typical seasonal variation pattern with maximum values observed in August and minimum ones around March and a general trend of increasing values from north to south

  10. Vertical and wide-angle seismic exploration of crustal structure, and the active evolution of the North Aegean Trough between the Sea of Marmara and Gulf of Corinth

    Sachpazi, M.; Vigner, A.; Laigle, M.; Hirn, A.; Roussos, N.


    The North Aegean Trough (NAT), which is the deepest among Aegean marine troughs, is bordered by the termination of the North Anatolian Fault, and thus marks the interaction of this strike-slip fault with mainland Greece and the extensional Aegean domain. In the development of academic exploration of active regions at the scale of the whole crust, with marine multichannel seismics (MCS), the STREAMERS acquisition almost ten years ago provided a first hint of the feasibility there and in other parts of the Aegean and Ionian seas (Sachpazi et al., Tectonophysics 1996), and a template for later MCS and coincident wide-angle reflection surveying. These profiles were acquired by the French N/O Nadir, with an only 96-channel streamer 2.4 km length, and with an only 840 cu. in. generator capacity of a 8 gun array, but for the first time shot in the "single-bubble" mode that was developed in this survey. With respect to the present standard set by 2001 cruises in the Gulf of Corinth (US R/V Maurice Ewing, Taylor et al. this meeting) and in the Sea of Marmara (French N/O Nadir, Hirn et al., EGS 2002 and this meeting) this was a 2 to 3 times shorter streamer cable, a 2 to 4 times smaller number of hydrophone groups, and a 10 to 3 times smaller source. The SEISGREECE survey, with a source 3 times that of STREAMERS but other parameters as modest, explored the Gulf of Corinth and the Cyclades and added profiles in the North Aegean to this early attempt. A first result of merging the two surveys was to lend credence to possible structures detected by the first single profile. This revealed an active, recent normal-fault imaged down to 10 km depth, that cuts at a N 110°E strike the northern side of the NAT (Laigle et al., Geology, 2000). Indeed although processing has been hampered by the modest streamer length and only 16 or 24-fold coverage, the data now resolve clearly the sedimentary structure, image the basement, detect intra-basement faults, an upper crustal reflective zone

  11. Propagation of back-arc extension into the arc lithosphere in the southern New Hebrides volcanic arc

    Patriat, M.; Collot, J.; Danyushevsky, L.; Fabre, M.; Meffre, S.; Falloon, T.; Rouillard, P.; Pelletier, B.; Roach, M.; Fournier, M.


    New geophysical data acquired during three expeditions of the R/V Southern Surveyor in the southern part of the North Fiji Basin allow us to characterize the deformation of the upper plate at the southern termination of the New Hebrides subduction zone, where it bends eastward along the Hunter Ridge. Unlike the northern end of the Tonga subduction zone, on the other side of the North Fiji Basin, the 90° bend does not correspond to the transition from a subduction zone to a transform fault, but it is due to the progressive retreat of the New Hebrides trench. The subduction trench retreat is accommodated in the upper plate by the migration toward the southwest of the New Hebrides arc and toward the south of the Hunter Ridge, so that the direction of convergence remains everywhere orthogonal to the trench. In the back-arc domain, the active deformation is characterized by propagation of the back-arc spreading ridge into the Hunter volcanic arc. The N-S spreading axis propagates southward and penetrates in the arc, where it connects to a sinistral strike-slip zone via an oblique rift. The collision of the Loyalty Ridge with the New Hebrides arc, less than two million years ago, likely initiated this deformation pattern and the fragmentation of the upper plate. In this particular geodynamic setting, with an oceanic lithosphere subducting beneath a highly sheared volcanic arc, a wide range of primitive subduction-related magmas has been produced including adakites, island arc tholeiites, back-arc basin basalts, and medium-K subduction-related lavas.

  12. Clinical Characteristics of the Premature Ejaculation Sufferers in Aegean Region of the Turkey: A Multicentre, Observational Study

    Ahmet Cihan; Ömer Demir; Ali Şahin; Fatih Zeren; Deniz Bolat; Burak Özçift; Abdulkadir Pektaş; Ertan Can; Bilal Gümüş; Tahir Turan; Ahmet Bölükbaşı; Haluk Erol; Ahmet Adil Esen


    Demonstration of the intra-vaginal ejaculation latency time (IELT) distribution in male subjects and its clinical expressions among couples in the Aegean region of the Turkey. Materials and Methods Subjects were recruited to the study from six different urologic centers in the Aegean region. During the enrollment period subjects were recruited in to two group according to presence of premature ejaculation (PE). PE diagnosis was made according to DSM-4 definition. Subjects...

  13. First recording of the non-native species Beroe ovata Mayer 1912 in the Aegean Sea



    Full Text Available A new alien species Beroe ovata Mayer 1912 was recorded in the Aegean Sea. It is most likely that this species spread on the currents from the Black Sea. Beroe ovata is also alien to the Black Sea, where it was introduced in ballast waters from the Atlantic coastal area of the northern America. The species is established in the Black Sea and has decreased the population of another invaderMnemiopsis leidyi, which has favoured the recovery of the Black Sea ecosystem.We compare a new 1 species with the native species fam. Beroidae from the Mediterranean and predict its role in the ecosystem of the Aegean Sea using the Black Sea experience.

  14. A three-step model to assess shoreline and offshore susceptibility to oil spills: the South Aegean (Crete) as an analogue for confined marine basins.

    Alves, Tiago M; Kokinou, Eleni; Zodiatis, George


    This study combines bathymetric, geomorphological, geological data and oil spill predictions to model the impact of oil spills in two accident scenarios from offshore Crete, Eastern Mediterranean. The aim is to present a new three-step method of use by emergency teams and local authorities in the assessment of shoreline and offshore susceptibility to oil spills. The three-step method comprises: (1) real-time analyses of bathymetric, geomorphological, geological and oceanographic data; (2) oil dispersion simulations under known wind and sea current conditions; and (3) the compilation of final hazard maps based on information from (1) and (2) and on shoreline susceptibility data. The results in this paper show that zones of high to very-high susceptibility around the island of Crete are related to: (a) offshore bathymetric features, including the presence of offshore scarps and seamounts; (b) shoreline geology, and (c) the presence near the shore of sedimentary basins filled with unconsolidated deposits of high permeability. Oil spills, under particular weather and oceanographic conditions, may quickly spread and reach the shoreline 5-96 h after the initial accident. As a corollary of this work, we present the South Aegean region around Crete as a valid case-study for confined marine basins, narrow seaways, or interior seas around island groups. PMID:25113103

  15. Protozoan parasites in cultured mussels Mytilus galloprovincialis in the Thermaikos Gulf (north Aegean Sea, Greece).

    Rayyan, Abdalnasser; Damianidis, Panagiotis; Antoniadou, Chryssanthi; Chintiroglou, Chariton C


    The protozoans Ancistrum mytili (Oligohymenophorea: Ancistridae) and Marteilia refringens/maurini (Marteiliidea: Marteiliidae) were found parasitizing cultured mussels Mytilus galloprovincialis L. in the Thermaikos Gulf (north Aegean Sea, Greece). The former did not affect the condition index of infected mussels, in contrast to the latter, which did so and which also induced hemocyte infiltration in the affected digestive epithelium. The prevalence of both parasites was relatively high in a polluted area. PMID:16903237

  16. Spatial distribution of vector borne disease agents in dogs in Aegean region, Turkey

    Kerem Ural; Mehmet Gultekin; Abidin Atasoy; Bulent Ulutas


    ABSTRACTObjective. Assess the spatial distribution of seroprevalence of infection with or exposure to 4 vector-borne pathogens Ehrlichia canis, Anaplasma phagocytophilum, Borrelia burgdorferi and Dirofilaria immitis, across the coastal states of the Aegean region with special reference to clinical signs and haematological variances related to disease condition. Materials and methods. A convenience sample, targeting blood from at least 10 pet dogs from İzmir, Aydin, Denizli, Mugla and Manisa c...

  17. Babylonian confusion of gudgeons in the west Aegean drainages inferred by the mitochondrial DNA analyses

    Radek Sanda; Jasna Vukic; Michal Nowak; Jan Mendel; Tihomir Stefanov; Stamatis Zogaris


    Gudgeons (Gobio and Romanogobio, Cypriniformes) are taxonomically very complicated group of primary freshwater fishes. The region of the west Aegean Sea rivers is inhabited by three species according to Kottelat and Freyhof (2007): Gobio feraensis endemic to the Pinios River basin; Gobio balcanicus inhabiting all remaining drainages, from the Aliakmon up to the Marica drainage; and Romanogobio elimeus occurring from the Pinios to the Vardar basin. Recent analysis of barcoding gene cytochrome ...

  18. Source of the tsunami generated by the 1650 AD eruption of Kolumbo submarine volcano (Aegean Sea, Greece)

    Ulvrova, Martina; Paris, R.; Nomikou, P.; Kelfoun, K.; Leibrandt, S.; Tappin, D. R.; McCoy, F. W.


    The 1650 AD explosive eruption of Kolumbo submarine volcano (Aegean Sea, Greece) generated a destructive tsunami. In this paper we propose a source mechanism of this poorly documented tsunami using both geological investigations and numerical simulations. Sedimentary evidence of the 1650 AD tsunami was found along the coast of Santorini Island at maximum altitudes ranging between 3.5 m a.s.l. (Perissa, southern coast) and 20 m a.s.l. (Monolithos, eastern coast), corresponding to a minimum inundation of 360 and 630 m respectively. Tsunami deposits consist of an irregular 5 to 30 cm thick layer of dark grey sand that overlies pumiceous deposits erupted during the Minoan eruption and are found at depths of 30-50 cm below the surface. Composition of the tsunami sand is similar to the composition of the present-day beach sand but differs from the pumiceous gravelly deposits on which it rests. The spatial distribution of the tsunami deposits was compared to available historical records and to the results of numerical simulations of tsunami inundation. Different source mechanisms were tested: earthquakes, underwater explosions, caldera collapse, and pyroclastic flows. The most probable source of the 1650 AD Kolumbo tsunami is a 250 m high water surface displacement generated by underwater explosion with an energy of ~ 2 × 1016 J at water depths between 20 and 150 m. The tsunamigenic explosion(s) occurred on September 29, 1650 during the transition between submarine and subaerial phases of the eruption. Caldera subsidence is not an efficient tsunami source mechanism as short (and probably unrealistic) collapse durations (< 5 min) are needed. Pyroclastic flows cannot be discarded, but the required flux (106 to 107 m3 · s- 1) is exceptionally high compared to the magnitude of the eruption.

  19. Zircon U-Pb, O, and Hf isotopic constraints on Mesozoic magmatism in the Cyclades, Aegean Sea, Greece

    Fu, Bin; Bröcker, Michael; Ireland, Trevor; Holden, Peter; Kinsley, Leslie P. J.


    Compared to the well-documented Cenozoic magmatic and metamorphic rocks of the Cyclades, Aegean Sea, Greece, the geodynamic context of older meta-igneous rocks occurring in the marble-schist sequences and mélanges of the Cycladic Blueschist Unit is as yet not fully understood. Here, we report O-Hf isotopic compositions of zircons ranging in age from ca. 320 Ma to ca. 80 Ma from metamorphic rocks exposed on the islands of Andros, Ios, Sifnos, and Syros with special emphasis on Triassic source rocks. Ion microprobe (SHRIMP II) single spot oxygen isotope analysis of pre-Cretaceous zircons from various felsic gneisses and meta-gabbros representing both the marble-schist sequences and the mélanges of the study area yielded a large range in δ18O values, varying from 2.7 ‰ to 10.1 ‰ VSMOW, with one outlier at -0.4 %. Initial ɛHf values (-12.5 to +15.7) suggest diverse sources for melts formed between Late Carboniferous to Late Cretaceous time that record derivation from mantle and reworked older continental crust. In particular, variable δ18O and ɛHf( t) values for Triassic igneous zircons suggest that magmatism of this age is more likely rift- than subduction-related. The significant crustal component in 160 Ma meta-gabbros from Andros implies that some Jurassic gabbroic rocks of the Hellenides are not part of SSZ-type (supra-subduction zone) ophiolites that are common elsewhere along the margin of the Pelagonian zone.

  20. Rotating arc spark plug

    Whealton, John H.; Tsai, Chin-Chi


    A spark plug device includes a structure for modification of an arc, the modification including arc rotation. The spark plug can be used in a combustion engine to reduce emissions and/or improve fuel economy. A method for operating a spark plug and a combustion engine having the spark plug device includes the step of modifying an arc, the modifying including rotating the arc.

  1. Babylonian confusion of gudgeons in the west Aegean drainages inferred by the mitochondrial DNA analyses

    Radek Sanda


    We have analysed control region (mitochondrial non coding DNA of gudgeon populations from all larger river drainages from the west Aegean region (Pinios to Marica basins. Included were also several populations from surrounding areas of the Danube River drainage and from the Black Sea rivers. The results are not at all congruent with the proposed taxonomy. MtDNA haplotypes of Romonagobio banarescui were found not only in the Vardar, but also in the lower Aliakmon River. Haplotypes of Romanogibo elimeus were found in the Pinios, upper Aliakmon and Loudias rivers. Situation of genus Gobio is completely confusing; there is no geographic structure in the distribution of haplotypes. Many different haplogroups are shared in some basins, especially in the drainages of the Struma, Mesta and Marica rivers. This indicates complicated evolutionary history of gudgeons in the region, probably having several historical refugia, and with multiple recent contacts of lineages. Our data indicate a contact between the Danubian, Black Sea and Aegean rivers. The taxonomic status of most of the populations of Gobio from the west Aegean area remains unclear.

  2. Large-scale bioprospecting of cyanobacteria, micro- and macroalgae from the Aegean Sea.

    Montalvão, Sofia; Demirel, Zeliha; Devi, Prabha; Lombardi, Valter; Hongisto, Vesa; Perälä, Merja; Hattara, Johannes; Imamoglu, Esra; Tilvi, Supriya Shet; Turan, Gamze; Dalay, Meltem Conk; Tammela, Päivi


    Marine organisms constitute approximately one-half of the total global biodiversity, being rich reservoirs of structurally diverse biofunctional components. The potential of cyanobacteria, micro- and macroalgae as sources of antimicrobial, antitumoral, anti-inflammatory, and anticoagulant compounds has been reported extensively. Nonetheless, biological activities of marine fauna and flora of the Aegean Sea have remained poorly studied when in comparison to other areas of the Mediterranean Sea. In this study, we screened the antimicrobial, antifouling, anti-inflammatory and anticancer potential of in total 98 specimens collected from the Aegean Sea. Ethanol extract of diatom Amphora cf capitellata showed the most promising antimicrobial results against Candida albicans while the extract of diatom Nitzschia communis showed effective results against Gram-positive bacterium, S. aureus. Extracts from the red alga Laurencia papillosa and from three Cystoseira species exhibited selective antiproliferative activity against cancer cell lines and an extract from the brown alga Dilophus fasciola showed the highest anti-inflammatory activity as measured in primary microglial and astrocyte cell cultures as well as by the reduction of proinflammatory cytokines. In summary, our study demonstrates that the Aegean Sea is a rich source of species that possess interesting potential for developing industrial applications. PMID:26902670

  3. New structural and U-Pb zircon data from Anafi crystalline basement (Cyclades, Greece): constraints on the evolution of a Late Cretaceous magmatic arc in the Internal Hellenides

    Martha, Silviu O.; Dörr, Wolfgang; Gerdes, Axel; Petschick, Rainer; Schastok, Janina; Xypolias, Paraskevas; Zulauf, Gernold


    The Asterousia Crystalline Complex consists of Late Cretaceous amphibolite facies metamorphic rocks and associated granitoids, which can be found in exposures on Crete and the Cyclades (Greece). It is attributed to the Uppermost Unit and therefore to the Pelagonian domain of the Internal Hellenides. The tectonometamorphic evolution of this unit is still a matter of debate. We present new structural and petrological data of Asterousia-type rocks and greenschist facies metamorphic rocks from the island of Anafi in the southern Aegean Sea as well as U-Pb zircon ages of granitoids from Anafi. The crystalline sequence of Anafi rests on top of Eocene flysch and comprises from bottom to top: (a) Anafi Greenschist; (b) Anafi Amphibolite Group (orthoamphibolite with intercalations of metasedimentary rocks at the base); and (c) Chalepa Group (amphibolite facies metasediments with slices of serpentinite and granitoids). LA-ICP-MS and ID-TIMS 206Pb/238U zircon ages of granodiorite from the Chalepa Group reveal several similar zircon populations suggesting continuous emplacement of granitoids inside a magmatic arc from ca. 72.5 to 79 Ma. The minimum emplacement age of granodioritic magma, deduced from the 206Pb/238U median age of the youngest zircon population, is 72.6 +0.1/-0.2 Ma. Deformation (micro)fabrics of granodiorite result from low strain obtained at T > 600 °C. This along with the U-Pb ages and published K-Ar ages indicates intrusion of the plutonic rocks at deep structural levels followed by very slow cooling. Monzogranitic dykes cutting through granodiorite in north-eastern Anafi are undeformed and yielded a 206Pb/238U median age of 69.9 +0.7/-0.7 Ma. Based on the new and published data, the following implications for the tectonometamorphic evolution on Anafi can be made: (1) obduction and accretion of mantle slices (serpentinite) to the Asterousia-type rocks were prior to amphibolite facies metamorphism; (2) intrusion of granitoids during the middle to late

  4. Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system

    Rizzo, Andrea Luca; Caracausi, Antonio; Chavagnac, Valèrie; Nomikou, Paraskevi; Polymenakou, Paraskevi N.; Mandalakis, Manolis; Kotoulas, Georgios; Magoulas, Antonios; Castillo, Alain; Lampridou, Danai


    Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their hazardousness and sea-depth. Here, we report 3He/4He measurements in CO2–dominated gases discharged at 500 m below sea level from the high-temperature (~220 °C) hydrothermal system of the Kolumbo submarine volcano (Greece), located 7 km northeast off Santorini Island in the central part of the Hellenic Volcanic Arc (HVA). We highlight that the mantle below Kolumbo and Santorini has a 3He/4He signature of at least 7.0 Ra (being Ra the 3He/4He ratio of atmospheric He equal to 1.39×10‑6), 3 Ra units higher than actually known for gases-rocks from Santorini. This ratio is also the highest measured across the HVA and is indicative of the direct degassing of a Mid-Ocean-Ridge-Basalts (MORB)-like mantle through lithospheric faults. We finally highlight that the degassing of high-temperature fluids with a MORB-like 3He/4He ratio corroborates a vigorous outgassing of mantle-derived volatiles with potential hazard at the Kolumbo submarine volcano.

  5. Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system.

    Rizzo, Andrea Luca; Caracausi, Antonio; Chavagnac, Valèrie; Nomikou, Paraskevi; Polymenakou, Paraskevi N; Mandalakis, Manolis; Kotoulas, Georgios; Magoulas, Antonios; Castillo, Alain; Lampridou, Danai


    Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their hazardousness and sea-depth. Here, we report (3)He/(4)He measurements in CO2-dominated gases discharged at 500 m below sea level from the high-temperature (~220 °C) hydrothermal system of the Kolumbo submarine volcano (Greece), located 7 km northeast off Santorini Island in the central part of the Hellenic Volcanic Arc (HVA). We highlight that the mantle below Kolumbo and Santorini has a (3)He/(4)He signature of at least 7.0 Ra (being Ra the (3)He/(4)He ratio of atmospheric He equal to 1.39×10(-6)), 3 Ra units higher than actually known for gases-rocks from Santorini. This ratio is also the highest measured across the HVA and is indicative of the direct degassing of a Mid-Ocean-Ridge-Basalts (MORB)-like mantle through lithospheric faults. We finally highlight that the degassing of high-temperature fluids with a MORB-like (3)He/(4)He ratio corroborates a vigorous outgassing of mantle-derived volatiles with potential hazard at the Kolumbo submarine volcano. PMID:27311383

  6. Early hominin biogeography in Island Southeast Asia.

    Larick, Roy; Ciochon, Russell L


    Island Southeast Asia covers Eurasia's tropical expanse of continental shelf and active subduction zones. Cutting between island landmasses, Wallace's Line separates Sunda and the Eastern Island Arc (the Arc) into distinct tectonic and faunal provinces. West of the line, on Sunda, Java Island yields many fossils of Homo erectus. East of the line, on the Arc, Flores Island provides one skeleton and isolated remains of Homo floresiensis. Luzon Island in the Philippines has another fossil hominin. Sulawesi preserves early hominin archeology. This insular divergence sets up a unique regional context for early hominin dispersal, isolation, and extinction. The evidence is reviewed across three Pleistocene climate periods. Patterns are discussed in relation to the pulse of global sea-level shifts, as well as regional geo-tectonics, catastrophes, stegodon dispersal, and paleogenomics. Several patterns imply evolutionary processes typical of oceanic islands. Early hominins apparently responded to changing island conditions for a million-and-a-half years, likely becoming extinct during the period in which Homo sapiens colonized the region. PMID:26478140

  7. Volcano collapse along the Aleutian Ridge (western Aleutian Arc)

    Montanaro, C.; J. Beget


    The Aleutian Ridge, in the western part of the Aleutian Arc, consists of a chain of volcanic islands perched atop the crest of a submarine ridge with most of the active Quaternary stratocones or caldera-like volcanoes being located on the northern margins of the Aleutian Islands. Integrated analysis of marine and terrestrial data resulted in the identification and characterization of 17 extensive submarine debris avalanche deposits from 11 volcanoes. Two morphological types of deposits are re...

  8. Peek Arc Consistency

    Bodirsky, Manuel


    This paper studies peek arc consistency, a reasoning technique that extends the well-known arc consistency technique for constraint satisfaction. In contrast to other more costly extensions of arc consistency that have been studied in the literature, peek arc consistency requires only linear space and quadratic time and can be parallelized in a straightforward way such that it runs in linear time with a linear number of processors. We demonstrate that for various constraint languages, peek arc consistency gives a polynomial-time decision procedure for the constraint satisfaction problem. We also present an algebraic characterization of those constraint languages that can be solved by peek arc consistency, and study the robustness of the algorithm.

  9. Electric arc hydrogen heaters

    The experimental data on the electric arc burning in hydrogen are presented. Empirical and semiempirical dependences for calculating the arc characteristics are derived. An engineering method of calculating plasma torches for hydrogen heating is proposed. A model of interaction of a hydrogen arc with a gas flow is outlined. The characteristics of plasma torches for heating hydrogen and hydrogen-bearing gases are described. (author)

  10. Wire + Arc Additive Manufacturing

    Williams, Stewart W.; Martina, Filomeno; Addison, Adrian C.; Ding, Jialuo; Pardal, Goncalo; Colegrove, Paul A.


    Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to ...

  11. Circulation and hydrological characteristics of the North Aegean Sea: a contribution from real-time buoy measurements



    Full Text Available In the framework of the POSEIDON Project, a network of open sea oceanographic buoys equipped with meteorological and oceanographic sensors has been operational in the Aegean Sea since 1998. The analysis of upper-ocean physical data (currents at 3m, temperature and salinity at 3-40m depths collected during the last 2 years from the stations of the North Aegean basin indicates a strong temporal variability of flow field and hydrological characteristics in both synoptic and seasonal time scales. The northern part of the basin is mainly influenced by the Black Sea Water outflow and the mesoscale variability of the corresponding thermohaline fronts, while the southern stations are influenced by the general circulation of the Aegean Sea with strong modulations caused by the seasonally varying atmospheric forcing.

  12. Land Use on the Island of Oahu, Hawaii, 1998

    U.S. Geological Survey, Department of the Interior — This is a vector GIS coverage (ESRI ArcInfo format) of the land use of the island of Oahu, 1998, derived from multiple sources of digital orthophotos.

  13. A detailed seismic zonation model for shallow earthquakes in the broader Aegean area

    Vamvakaris, D. A.; Papazachos, C. B.; Papaioannou, Ch. A.; Scordilis, E. M.; Karakaisis, G. F.


    In the present work we propose a new seismic zonation model of area type sources for the broader Aegean area, which can be readily used for seismic hazard assessment. The definition of this model is based not only on seismicity information but incorporates all available seismotectonic and neotectonic information for the study area, in an attempt to define zones which show not only a rather homogeneous seismicity release but also exhibit similar active faulting characteristics. For this reason, all available seismological information such as fault plane solutions and the corresponding kinematic axes have been incorporated in the analysis, as well as information about active tectonics, such as seismic and active faults. Moreover, various morphotectonic features (e.g. relief, coastline) were also considered. Finally, a revised seismic catalogue is employed and earthquake epicentres since historical times (550 BC-2008) are employed, in order to define areas of common seismotectonic characteristics, that could constitute a discrete seismic zone. A new revised model of 113 earthquake seismic zones of shallow earthquakes for the broader Aegean area is finally proposed. Using the proposed zonation model, a detailed study is performed for the catalogue completeness for the recent instrumental period.Using the defined completeness information, seismicity parameters (such as G-R values) for the 113 new seismic zones have been calculated, and their spatial distribution was also examined. The spatial variation of the obtained b values shows an excellent correlation with the geotectonic setting in the area, in good agreement with previous studies. Moreover, a quantitative estimation of seismicity is performed in terms of the mean return period, Tm, of large (M ≥ 6.0) earthquakes, as well as the most frequent maximum magnitude, Mt, for a typical time period (T = 50 yr), revealing significant spatial variations of seismicity levels within the study area. The new proposed seismic

  14. Arc magmatic chemistry: The source versus process debate

    Most geochemical studies of arcs world-wide easily demonstrate mixing trends in isotope-isotope space that originate with a MORB component. A slab-derived and possible hydrous fluid-dominated component is also well defined in some studies. This is best observed in arcs in which the magmas are otherwise highly lithophile-element poor, such as the Tonga-Kermadec arc. This component is only moderately LIL element-enriched with very high 87Sr/86Sr and 207Pb/204Pb ratios, low Ce/Pb and low'143Nd/144Nd. It is also characterised by high U/Th and with U-series disequilibrium to the right of the equiline. A third and important geochemical vector is one particularly recognised in arcs in complex tectonic settings in the Mediterranean, the Aegean and in Indonesia and is one which leads to the development of K20-rich suites. Features include silica-undersaturation, very high K/Nb, Ba/Nb and Ce/Y with 87Sr/86Sr values which are moderately low at moderately low 143Nd/144Nd values. On 87Sr/86Sr versus 143Nd/'144Nd diagrams these show mixing lines towards a significantly less radiogenic Sr end member than the MORB-sediment mixture. Magmas enriched in this component don't tend to show U-series disequilibrium and have low 230Th/232Th and 238U values. They appear to have κTH values that reflect a source with a long term history of high Th/U. The Nd- and Sr-isotopic characteristics imply a source with a moderately long history of LREE enrichment at moderate Rb/Sr and U/Pb

  15. Seasonal Nutrient Enrichment Experiment in Homa Lagoon (İzmir Bay, Aegean Sea)

    Banu Kutlu


    In order to determine the effects of nutrient (P, Si, NH4, NO3) enrichment on the growth of phytoplankton in Homa Lagoon (İzmir Bay, Aegean Sea), experiments of enrichment with discontinuous cultures have been executed seasonally in 2007. In our study, the elements limiting the growth of phytoplankton were NO3, P and Si in spring season, N and P in summer season, and NH4 in autumn and winter seasons. So, it has been determined that the addition of nitrogen (N) and phosphor (P) has led signifi...

  16. First recording of the non-native species Beroe ovata Mayer 1912 in the Aegean Sea

    Shiganova, T.A.; Christou, E. D.; Siokou, I.


    A new alien species Beroe ovata Mayer 1912 was recorded in the Aegean Sea. It is most likely that this species spread on the currents from the Black Sea. Beroe ovata is also alien to the Black Sea, where it was introduced in ballast waters from the Atlantic coastal area of the northern America. The species is established in the Black Sea and has decreased the population of another invaderMnemiopsis leidyi, which has favoured the recovery of the Black Sea ecosystem.We compare a new 1 species w...

  17. Oil pollution in surface water of the Turkish side of the Aegean and Eastern Mediterranean Seas

    Öztürk, Bayram; Altuğ, Gülşen; Çiftçi, Mine Çardak and Pelin S.


    Abstract Oil pollution of the South part of the Aegean Sea and Mediterranean Sea was investigated at 48 stations from the Bozburun Peninsula to İskenderun buy, during 17-28 August 2006.The highly carbon concentration of the samples was determined by UVF by using Iraq crude oil and also chrysene as references materials. The oil pollution in examined sea water was 4.16 µg/L in Antalya Bay and 100.33 µg/L in Iskenderun through Iraq crude oil equivalent. The highest polluted areas are Iskenderun,...

  18. Distribution and transfer of dissolved trace metals in the North Aegean Sea

    Sampling for trace metal analysis in the North Aegean Sea took place from 13-25 May 1997 with the R/V Aegaeo. Samples were collected from 12 Go-flo bottles attached to the rosette-CTD system and were filtered through 0.45 μm membrane filters, on-board, under a nitrogen atmosphere. Precautions were taken during handling of samples to minimise contamination. The samples were acidified and carried back to the clean laboratory for further analysis. A preconcentration step using the chelex-100 resin followed. Trace metals were determined on a Perkin-Elmer AAS equipped with a HGA-700

  19. Preliminary biological data on Pomadasys incisus (Osteichthyes: Haemulidae in the Aegean Sea, Greece



    Full Text Available The present paper gives, for the first time, some biological data concerning Pomadasys incisus in theArgolikos Gulf (C. Aegean Sea. The bastard grunt (Pomadasys incisus is a thermophilic species welladapted in the above area, but the status of fishery suggests an overexploitation. The sex ratio was infavour of males. The length frequency distribution did not differ between the sexes. Growth in weight wasestimated by means of the length-weight relationship. Reproduction seemed to take place in summer. Certainmorphometric characters appeared to be useful while comparing populations among the differentpopulations in the Mediterranean.

  20. Distribution of the Demersal Fishes on the Continental Shelves of the Levantine and North Aegean Seas (Eastern Mediterranean)

    Keskin, Çetin; Turan, Cemal; Ergüden, Deniz


    The aim of this study was to investigate the distribution patterns of demersal fishes on the continental shelves of the north-eastern Levantine and north-eastern Aegean seas. Fish samples were collected by bottom trawl. A total of 29 hauls were carried out, 15 hauls between 43 to 121 m depth in the north-eastern Levantine Sea and 14 hauls between 65 to 100 m depth in the north-eastern Aegean Sea. The total trawled area for both region was 1.87 km2. Cluster analysis and non-metric multidimens...

  1. Spatial distribution of vector borne disease agents in dogs in Aegean region, Turkey

    Kerem Ural


    Full Text Available Objective. Assess the spatial distribution of seroprevalence of infection with or exposure to 4 vector-borne pathogens Ehrlichia canis, Anaplasma phagocytophilum, Borrelia burgdorferi and Dirofilaria immitis, across the coastal states of the Aegean region with special reference to clinical signs and haematological variances related to disease condition. Materials and methods. A convenience sample, targeting blood from at least 10 pet dogs from İzmir, Aydin, Denizli, Mugla and Manisa cities involved was evaluated using a canine point-of-care ELISA kit. Results. Out of 307 dogs tested the overall seroprevalence was highest for E. canis (24.42%, followed by E. canis + A. phagocytophilum co-infection (10.42%, A. phagocytophilum (7.49% and D. immitis (2.28%. Only 2 cases were seropositive to B. burgdorferi albeit 10 dogs were co-infected with more than 2 agents. For both dogs infected with E. canis and co-infected with E. canis and A. phagocytophilum, anemia, thrombocytopenia and leukocytosis, were more commonly detected, whereas thrombocytopenia and leukocytosis were significant finding in dogs infected with A. phagocytophilum or D. immitis, respectively. Variance analysis showed significant differences for mean RBC, Hb, PCV and PLT values (p<0.01 among control group and other groups. Conclusions. Seropositivity for vector-borne pathogens other than B. burgdorferi, is moderately to widely distributed in dogs residing in the Aegean region in Turkey.

  2. Maximum Rain-Rate Evaluations in Aegean Archipelagos Hellas for Rain Attenuation Modeling at Microwave Frequencies

    Evangelia Karagianni


    Full Text Available By utilizing meteorological data such as relative humidity, temperature, pressure, rain rate and precipitation duration at eight (8 stations in Aegean Archipelagos from six recent years (2007 – 2012, the effect of the weather on Electromagnetic wave propagation is studied. The EM wave propagation characteristics depend on atmospheric refractivity and consequently on Rain-Rate which vary in time and space randomly. Therefore the statistics of radio refractivity, Rain-Rate and related propagation effects are of main interest. This work investigates the maximum value of rain rate in monthly rainfall records, for a 5 min interval comparing it with different values of integration time as well as different percentages of time. The main goal is to determine the attenuation level for microwave links based on local rainfall data for various sites in Greece (L-zone, namely Aegean Archipelagos, with a view on improved accuracy as compared with more generic zone data available. A measurement of rain attenuation for a link in the S-band has been carried out and the data compared with prediction based on the standard ITU-R method.

  3. Vertical distribution of marine cyanobacteria Synechococcus spp. in the Black, Marmara, Aegean, and eastern Mediterranean seas

    Uysal, Zahit


    The vertical distributions of the unicellular cyanobacteria Synechococcus were studied in several highly contrasting seas: the Black Sea, Sea of Marmara, Aegean Sea, and Mediterranean Sea. Cell abundances varied significantly on both vertical and horizontal scales in all physically and spatially discrete water masses. Epifluorescence microscope cell counts from all seas clearly showed that majority of the population remains suspended in the surface-mixed layer and decreases gradually towards the base of the euphotic zone. Surface spatial distributions in the Black Sea were heterogeneous. Salinity, rather than temperature, seemed to have the greatest impact on the surface distribution of cells in this highly eutrophic sea. Changes in abundance in the mixed layer were small compared to the abrupt changes below the halocline, especially in the Black Sea and the Sea of Marmara. In contrast to the Black Sea, the major population remains suspended above the depth of fluorescence maximum in the Aegean and eastern Mediterranean seas. Significant correlations ( r>P0.01) were observed between cell counts and physical and chemical parameters with depth in the Black Sea. In all seas, cells at subsurface chlorophyll- a maximum layer (SCML) reflected brighter and longer fluorescence than those present at the surface and below. Cell size derived from flow cytometry indicated the presence of larger cells at the surface mixed layer compared to those at depth.

  4. Trichoptera biodiversity of the Aegean and Adriatic sea basins in the republic of Kosovo.

    Ibrahimi, Halil; Kučinić, Mladen; Gashi, Agim; Grapci-Kotori, Linda


    We present the first preliminary inventory of Trichoptera taxa in the Aegean and Adriatic Sea basins in Kosovo that have previously received poor and fragmentary attention. Adult caddisflies were collected using ultraviolet (UV) light traps in 13 stations in areas of the Aegean Sea and Adriatic Sea drainage basins in Kosovo. Nineteen species out of 82, reported in this article, are first records for the Kosovo caddisfly fauna. Five genera are recorded for the first time in Kosovo: Brachycentrus, Ecclisopteryx, Psilopteryx, Thremma, and Oecetis. During this investigation, we found several Southeastern European endemic and rare species whose previous known distribution was limited to particular areas of this region, as well as other species whose distribution is considerably enlarged by this investigation: Polycentropus ierapetra, Polycentropus irroratus, Chaetopteryx stankovici, Drusus schmidi, Drusus tenellus, Potamophylax goulandriourum, Oecetis notata, and Notidobia melanoptera. Even though this article is a result of a limited sampling effort, it increases the number of Trichoptera taxa recorded for the Republic of Kosovo to 131. PMID:25434031

  5. Preceramic, Aceramic or Early Ceramic? The radiocarbon dated beginning of the Neolithic in the Aegean

    Agathe Reingruber


    Full Text Available The Pre-Pottery-Neolithic refers to a period in the Eastern Mediterranean when ceramic containers were not yet in use (although small objects made of clay were already being created. This concept, which reflects a specific and quite unique stage in the development of human history, was introduced to Aegean prehistory under the term of Preceramic during the 1950’s (e.g., in Argissa Magoula and Sesklo. Shortly thereafter, a different term, the Aceramic, was applied in the Aegean (e.g., in Knossos for levels devoid of pottery, although ceramic products were supposedly used in the wider region. In some cases, the thin levels interpreted as Preceramic or as Aceramic contained sherds that were regarded as being intrusive from above (e.g., Argissa-Magoula, Franchthi Cave. The new sequences of radiocarbon dates allow a more precise description of this early period and thereby contribute, not least, also to the clarification of terminological issues.

  6. Geochemical characteristics of late Quaternary sediments from the southern Aegean Sea (Eastern Mediterranean



    Full Text Available Ten cores from the southern Aegean Sea have been logged for their lithological composition and seventy-three sub-samples were analysed for the determination of major and trace elements concentrations. Four lithological units were identified, namely, mud, volcanic, turbidite and sapropel. On the basis of the “Z-2” Minoan ash layer radiocarbon age sedimentation rates for the southern Aegean Sea were estimated at 3.26 to 4.15 cm kyr -1. Simple correlation analysis revealed three groups of elements associated with: (1 biogenic carbonates; (2 terrigenous alumino-silicates and (3 sapropelic layers. R-mode factor analysis applied on the carbonate-free corrected data-set defined four significant factors: (1 the “detrital alumino-silicate factor” represented by Si, Al, Na, K, Rb, Zr, Pb and inversely related to Ca, Mg, and Sr; (2 a “hydrothermal factor” loaded with Cr, Ni, Co, Cu, Fe; (3 the “volcanic ash factor” with high loadings for Ti, Al, Fe, Na and (4 a “sapropel factor” represented by Ba, Mo, and Zn. High factor scores for the “hydrothermal factor” were observed in sediment samples proximal to Nisyros Isl., suggesting a potential hydrothermal influence. Red-brown oxides and crusts dredged from this area support further this possibility. The use of factor analysis enabled for a better understanding of the chemical elements associations that remained obscured by correlation analysis.

  7. Habitat Selection and Temporal Abundance Fluctuations of Demersal Cartilaginous Species in the Aegean Sea (Eastern Mediterranean)

    Maravelias, Christos D.; Tserpes, George; Pantazi, Maria; Peristeraki, Panagiota


    Predicting the occurrence of keystone top predators in a multispecies marine environment, such as the Mediterranean Sea, can be of considerable value to the long-term sustainable development of the fishing industry and to the protection of biodiversity. We analysed fisheries independent scientific bottom trawl survey data of two of the most abundant cartilaginous fish species (Scyliorhinus canicula, Raja clavata) in the Aegean Sea covering an 11-year sampling period. The current findings revealed a declining trend in R. clavata and S. canicula abundance from the late ′90 s until 2004. Habitats with the higher probability of finding cartilaginous fish present were those located in intermediate waters (depth: 200–400 m). The present results also indicated a preferential species' clustering in specific geographic and bathymetric regions of the Aegean Sea. Depth appeared to be one of the key determining factors for the selection of habitats for all species examined. With cartilaginous fish species being among the more biologically sensitive fish species taken in European marine fisheries, our findings, which are based on a standardized scientific survey, can contribute to the rational exploitation and management of their stocks by providing important information on temporal abundance trends and habitat preferences. PMID:22536389

  8. On the fecundity of the bogue Boops boops (Linnaeus, 1758) in the Turkish Aegean Sea

    Burcu Taylan; Bahar Bayhan


    Objective: To determine the fecundity of Boops boops (B. boops) from Aegean Sea coast of Turkey. Methods: A total of 470 specimens of B. boops were collected monthly from November in 2008 to October of 2009 in Izmir Bay (central Aegean Sea). Total length and total weight of each fish were measured and the maturity stages of gonads were determined. About 30 mature ovariums were taken to determine fecundity and oocysts were counted by using gravimetric method. Results: About 210 were females (44.7%) and 226 males (48.1%) while 34 (7.2%) were hermafrodite in terms of sexuality with sex ratio (female: male) of 0.93:1.00. The fecundity of the bogue was assessed by the gravimetric method with 30 ovaries from females between the total length of 19.6 and 27.6 cm [(mean: 23.5 ± 2.1) cm]. Estimates of total fecundity varied between 33072 and 66123 oocytes (mean: 49008 ± 8826) and fecundity–total length, fecundity–weight relationships were expressed as :F = 8207.6e0.075TL, F = 30297e0.003TW respectively. Conclusions: The results of the study will contribute to the reproductive biology of B. boops and will be useful for management of fisheries.

  9. Eastern Mediterranean geodynamics revised: a new Aegean extension realm in space, time and direction identified in the western Cyclades

    Grasemann, B.; Edwards, M.; Schneider, D.; Iglseder, C.; Zámolyi, A.; Rambousek, C.; Mueller, M.; Voit, K.; Thoeni, M.; Kloetzli, U.; Exner, U.


    The Eastern Mediterranean is renowned for its striking geodynamic features; strong seismicity with distinctive spatial and subsurface distributions, lucid slab tomography and accelerated slab retreat bourne out by some of the globally greatest angular velocities for continental crust displacement. The key questions of historical persistence of or precursor(s) to this setting are addressed by the early blueschist genesis and exhumation during collision and subsequent later-orogenic extension. The extension, in particular, is critical to the geodynamic models; the magnitude, distribution, kinematics, thermal structure and overall timetable are key variables. When and how did extension migrate /switch to the Cretan region and the presently active Gulf of Corinth? Most constraints have hitherto come from the central and western Cyclades (e.g. Naxos, Mykonos, Tinos, Paros) where an overall N-NE directed kinematics of Mid-Late Miocene extension (including any attendant melting) are documented through structural analyses, crystallisation and/or cooling geochronology and geobarometry. The eastern Cyclades meanwhile have lacked such comprehensive study. Project ACCEL (Aegean Core Complexes along an Extended Lithosphere) has obtained equivalent datasets for the eastern Cyclades that identify a realm of opposite kinematic sense (S-SW directed) crustal extension coeval with anatexis and multiple crustal failure that are apparently protracted since Eocene to Late Miocene; much earlier than for the central and western Cyclades. On Serifos island, P/T conditions (from petrology and deformation mechanisms), zircon U-Pb TIMS crystallisation ages, Rb-Sr cooling ages and structural surveying reveal that a major granodiorite intrusion syn- to post-dates a top-to-SSW, mid-upper crustal, mylonitic lithospheric-scale extensional detachment. This entire package further cross-cuts an earlier top-to-SSW, lower-mid crustal, high strain zone that mylonitises an S-type granite whose zircons

  10. Faroe Islands

    Christoffersen, Lisbet


    An update introduction including recent legislative changes on the Folkchurch of the Faroe Islands......An update introduction including recent legislative changes on the Folkchurch of the Faroe Islands...

  11. Cinnabar, arsenian pyrite and thallium-enrichment in active shallow submarine hydrothermal vents at Paleochori Bay, Milos Island, Greece

    Kati, Marianna; Voudouris, Panagiotis; Valsami-Jones, Eugenia; Magganas, Andreas; Baltatzis, Emmanouil; Kanellopoulos, Christos; Mavrogonatos, Constantinos


    We herein report the discovery of active cinnabar-depositing hydrothermal vents in a submarine setting at Paleochori Bay, within the offshore southeastern extension of the Milos Island Geothermal Field, South Aegean Active Volcanic Arc. Active, low temperature (up to 115 °C) hydrothermal venting through volcaniclastic material has led to a varied assemblage of sulfide and alteration mineral phases in an area of approximately 1 km2. Our samples recovered from Paleochori Bay are hydrothermal edifices composed of volcaniclastic detrital material cemented by pyrite, or pure sulfide (mainly massive pyrite) mounts. Besides pyrite and minor marcasite, the hydrothermal minerals include cinnabar, amorphous silica, hydrous ferric oxides, carbonates (aragonite and calcite), alunite-jarosite solid solution and Sr-rich barite. Among others, growth textures, sieve-textured pyrite associated with barite, alunite-jarosite solid solution and hydrous ferric oxides rims colloform-banded pyrite layers. Overgrowths of arsenian pyrite layers (up to 3.2 wt. % As and/or up to 1.1 wt. % Mn) onto As-free pyrite indicate fluctuation in As content of the hydrothermal fluid. Mercury, in the form of cinnabar, occurs in up to 5 μm grains within arsenian pyrite layers, usually forming distinct cinnabar-enriched micro-layers. Hydrothermal Sr-rich barite (barite-celestine solid solution), pseudocubic alunite-jarosite solid solution and Mn- and Sr-enriched carbonates occur in various amounts and closely associated with pyrite and/or hydrous ferric oxides. Thallium-bearing sulfides and/or sulfosalts were not detected during our study; however, hydrous ferric oxides show thallium content of up to 0.5 wt. % Tl. The following scenarios may have played a role in pyrite precipitation at Paleochori: (a) H2S originally dissolved in the deep fluid but separated upon boiling could have reacted with oxygenated seawater under production of sulphuric acid, thus causing leaching and dissolution of primary iron

  12. Tectono-stratigraphic evolution through successive extensional events of the Anydros Basin, hosting Kolumbo volcanic field at the Aegean Sea, Greece

    Nomikou, P.; Hübscher, C.; Ruhnau, M.; Bejelou, K.


    The structural evolution of the South Aegean Sea is little explored due to the lack of marine seismic data. Our present day understanding is mainly based on some island outcrops and GPS measurements. In this study we discuss the rather incremental opening of the Anydros Basin in the Pliocene during six major tectonic pulses and the subsequent basin fill processes by interpreting seismic data and derived time isochore maps. Between the active pulses basin floor tilting persisted on a much lower rate. Seismic data illustrate the depositional processes in the emerging Anydros Basin. The observation of onlap fill strata, divergent reflection pattern, moat channels and contourite drifts imply that deposition was controlled by turbidity and contour currents as well as the tilting basin floor. The metamorphic Attico-Cycladic basement shows a rise that aligns along an NW-SE directed axis crossing Anydros island. This axis marks a structural change of the Santorini-Amorgos Ridge and thus represents a major structural boundary. Dip angles of NE-SW trending major faults, like the Santorini-Amorgos Fault, indicate normal faulting to be the superior mechanism forming the present horst and graben environment. Hence, the area is likely to be in a state of NW-SE directed extensional stresses forming the asymmetric graben structure of Anydros. Secondary fault clusters strike the same direction but show much steeper dip angles, possibly indicating strike-slip movement or resulting from deformational stresses along the hinge zones of the normal faults. The majority of the faults we discovered are located in the area of earthquake clusters, which is another indication of recent faulting. Ring faults around Kolumbo submarine volcano, result from caldera collapse and mark the diameter of the magma chamber approximately to 20 km.

  13. Wild fire effects on floristic diversity in three thermo-Mediterranean vegetation types in a small islet of eastern Aegean sea

    Abraham, Eleni; Kyriazopoulos, Apostolos; Korakis, George; Parissi, Zoi; Chouvardas, Dimitrios


    Sclerophyllus scrub formations, the main vegetation type in many islands of the Aegean area, are characterized by their high biodiversity. Dominant shrub species of sclerophyllus formations are well adapted to dry season conditions by various anatomical and physiological mechanisms. As a result, their biomass acts as very flammable fine fuel, and consequently wild fires are very common in these ecosystems. Wildfire effects on vegetation and biodiversity in the Mediterranean basin have been studied and the results are diverse depending mainly on vegetation type and frequency of fire. The aim of this study was to evaluate the effects of wildfire on floristic diversity and species composition in three thermo-Mediterranean vegetation types 1) Sacropoterium spinosum phrygana, 2) low formations of Cistus creticus and 3) low formations of Cistus creticus in abandoned terraces. The research was conducted in Enoussa islet, which is located northeastern of Chios Island, in May 2013 (one year after the fire). Vegetation sampling was performed along five transects placed in recently burned and in adjacent unburned sites of each vegetation type. The plant cover and the floristic composition were measured, while diversity, evenness and dominance indices were determined for the vegetation data. Vegetation cover and the floristic diversity were significant lower and higher respectively in burned areas in comparison to the unburned. The woody species followed by the annual grasses and the annual forbs dominated in both burned and unburned areas. However, the woody species were significantly decreased in the burned areas in all vegetation types, while the annual grasses only in the burned areas of Sacropoterium spinosum phrygana and Cistus creticus in abandoned terraces. Inversely, the annual forbs significantly increased in the burned sites of Cistus creticus formations. The highest value of Morisita-Horn Index of similarity between burned and unburned sites (beta diversity) was

  14. Hemiasterella aristoteliana n. sp. (Porifera, Hadromerida) from the Aegean Sea with a discussion on the family Hemiasterellidae

    Voultsiadou-Koukoura, Eleni; Van, Soest


    A representative of the genus Hemiasterella Carter, 1879 was found for the first time in the Mediterranean Sea during sampling in the shallow waters of the northern Aegean Sea. The new species, H. aristoteliana, is compared with Atlantic Hemiasterella elongata Topsent, 1928. The status of the family Hemiasterellidae is discussed.

  15. Tokamak ARC damage

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage

  16. Vacuum arc anode phenomena

    A brief review of anode phenomena in vacuum arcs is presented. Discussed in succession are: the transition of the arc into the anode spot mode; the temperature of the anode before, during and after the anode spot forms; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. The dominant mechanism controlling the transition of the vacuum arc into the anode spot mode appears to depend upon the electrode geometry, the electrode material, and the current waveform of the particular vacuum arc being considered. Either magnetic constriction in the gap plasma or gross anode melting can trigger the transition; indeed, a combination of the two is a common cause of anode spot formation

  17. Crustal tomography of the Aegean-Anatolian domain using noise cross-correlations

    Hubans, Fabien; Paul, Anne; Campillo, Michel; Karabulut, Hayrullah; Hatzidimitriou, Panagiotis


    Data of more than 150 temporary and permanent broadband seismological stations deployed in the Aegean-Anatolian domain between May 2007 and May 2009 are grouped in the SIMBAAD (Seismic Imaging of the Mantle Across the Anatolian Domain) dataset. We compute noise cross-correlations between all station pairs on a 1.5-yr duration. We obtain more than 11.000 correlations for each component of the cross-correlation tensor. We apply a MFA (Multiple Filter Analysis) method to measure group velocity dispersion curves of Rayleigh waves on 4 components of the correlation tensor (ZZ, ZR, RZ, RR) and of Love waves on the TT component, both in positive and negative times. According to the theory, a noise cross-correlation converges to the Green function if noise sources are randomly distributed around the station pair. If this condition is fulfilled, the cross-correlation should be symmetrical in time. We compare group velocity measurements between positive and negative times to evaluate the convergence of each cross-correlation to the Green function. The quality of the symmetry is used to weight the time measurements in the inversion for group velocity maps. In the last step, Rayleigh wave group velocity data are inverted for a 3-D model of S-wave velocity. This processing gives an image of the crustal structure in the area [37-41°N ; 23-33°E] with a horizontal resolution of 60 to 200 km depending on depth and station coverage. The shallowest layers clearly display the present-day thick sedimentary basins (Axios, Thrace, Marmara, Bay of Antalya, ...) and older sedimentary nappes (Lycian nappes, Miocene sediments in the Kirsehir block) as strong low velocity anomalies. At larger depth, Southwestern Anatolia is characterized by a broad low velocity anomaly which contrasts with the higher velocities of the Aegean Sea. We clearly image a West to East increase of Moho depth from 20-25 km in the Aegean Sea to 35 km in the Anatolian plateau. This increase located between 27°E and

  18. Holocene Climatic Optimum centennial-scale paleoceanography in the NE Aegean (Mediterranean Sea)

    Triantaphyllou, Maria V.; Gogou, Alexandra; Dimiza, Margarita D.; Kostopoulou, Sofia; Parinos, Constantine; Roussakis, Grigoris; Geraga, Maria; Bouloubassi, Ioanna; Fleitmann, Dominik; Zervakis, Vassilis; Velaoras, Dimitris; Diamantopoulou, Antonia; Sampatakaki, Angeliki; Lykousis, Vassilis


    Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4G provided new centennial-scale paleoceanographic data for sapropel S1 deposition in the NE Aegean Sea during the Holocene Climatic Optimum. Sapropel layer S1a (10.2-8.0 ka) was deposited in dysoxic to oxic bottom waters characterized by a high abundance of benthic foraminiferal species tolerating surface sediment and/or pore water oxygen depletion (e.g., Chilostomella mediterranensis, Globobulimina affinis), and the presence of Uvigerina mediterranea, which thrives in oxic mesotrophic-eutrophic environments. Preservation of organic matter (OM) is inferred based on high organic carbon as well as loliolide and isololiolide contents, while the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. High inputs of terrigenous OM are attributed to north Aegean borderland riverine inputs. Both alkenone-based sea surface temperatures (SSTs) and δO18 G. bulloides records indicate cooling at 8.2 ka (S1a) and ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7-6.4 ka) is characterized by rather oxic conditions; abundances of foraminiferal species tolerant to oxygen depletion are very low compared with the U. mediterranea rise. Strongly fluctuating SSTs demonstrate repeated cooling and associated dense water formation, with a major event at 7.4 ka followed by cold spells at 7.0, 6.8, and 6.5 ka. The prominent rise of the carbon preference index within the S1b layer indicates the delivery of less degraded terrestrial OM. The increase of algal biomarkers, labile OM-feeding foraminifera and eutrophic planktonic species pinpoints an enhanced in situ marine productivity, promoted by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine OM along with fresher terrestrial OM inputs after ~7.7 ka imply sources alternative/additional to the north Aegean riverine borderland sources for

  19. Single-Arc IMRT?

    The idea of delivering intensity-modulated radiation therapy (IMRT) with a multileaf collimator in a continuous dynamic mode during a single rotation of the gantry has recently gained momentum both in research and industry. In this note we investigate the potential of this Single-Arc IMRT technique at a conceptual level. We consider the original theoretical example case from Brahme et al that got the field of IMRT started. Using analytical methods, we derive deliverable intensity 'landscapes' for Single-Arc as well as standard IMRT and Tomotherapy. We find that Tomotherapy provides the greatest flexibility in shaping intensity landscapes and that it allows one to deliver IMRT in a way that comes close to the ideal case in the transverse plane. Single-Arc and standard IMRT make compromises in different areas. Only in relatively simple cases that do not require substantial intensity modulation will Single-Arc be dosimetrically comparable to Tomotherapy. Compared with standard IMRT, Single-Arc could be dosimetrically superior in certain cases if one is willing to accept the spreading of low dose values over large volumes of normal tissue. In terms of treatment planning, Single-Arc poses a more challenging optimization problem than Tomotherapy or standard IMRT. We conclude that Single-Arc holds potential as an efficient IMRT technique especially for relatively simple cases. In very complex cases, Single-Arc may unduly compromise the quality of the dose distribution, if one tries to keep the treatment time below 2 min or so. As with all IMRT techniques, it is important to explore the tradeoff between plan quality and the efficiency of its delivery carefully for each individual case. (note)

  20. ALICE - ARC integration

    Anderlik, Csaba; Gregersen, Anders Rhod; Kleist, Josva; Peters, Andreas; Siaz, Pablo


    AliEn or Alice Environment is the Gridware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructur...

  1. Accumulation rates and sediment deposition in the Goekova Bay in Aegean Sea Turkish Coast

    Sediment accumulation rates were estimated from the vertical distribution of excess 210Pb in sediment cores collected at six stations in the Goekova Bay near the heavily industrialized Turkish Coastal zone of the Aegean Sea. Total 210Pb was determined by measuring 210Po activities. The sediment accumulation rates were calculated to vary from 0.32±0.01 cm yr-1 (0.17±0.01 g cm-2 yr-1) to 1.92±0.20 cm yr-1 (1.13±0.10 g cm-2 yr-1). The unsupported 210Pb flux was calculated from the accumulated dry matter of the examined slices and their unsupported 210Pb concentrations. The flux of unsupported 210Pb varies between 62±5 and 105±8 Bq m-2 yr-1. The average depositional flux was found to be considerably higher for cores from the Mediterranean

  2. Seasonal Nutrient Enrichment Experiment in Homa Lagoon (İzmir Bay, Aegean Sea

    Banu Kutlu


    Full Text Available In order to determine the effects of nutrient (P, Si, NH4, NO3 enrichment on the growth of phytoplankton in Homa Lagoon (İzmir Bay, Aegean Sea, experiments of enrichment with discontinuous cultures have been executed seasonally in 2007. In our study, the elements limiting the growth of phytoplankton were NO3, P and Si in spring season, N and P in summer season, and NH4 in autumn and winter seasons. So, it has been determined that the addition of nitrogen (N and phosphor (P has led significant change in biomass and growth of phytoplankton. It has also been observed that diatom and dinoflagellate species have grown under various concentrations of, especially, Silicate (Si and nitrogen (N.

  3. Galapagos Islands


    This true-color image of the Galapagos Islands was acquired on March 12, 2002, by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite. The Galapagos Islands, which are part of Ecuador, sit in the Pacific Ocean about 1000 km (620 miles) west of South America. As the three craters on the largest island (Isabela Island) suggest, the archipelago was created by volcanic eruptions, which took place millions of years ago. Unlike most remote islands in the Pacific, the Galapagos have gone relatively untouched by humans over the past few millennia. As a result, many unique species have continued to thrive on the islands. Over 95 percent of the islands' reptile species and nearly three quarters of its land bird species cannot be found anywhere else in the world. Two of the more well known are the Galapagos giant tortoise and marine iguanas. The unhindered evolutionary development of the islands' species inspired Charles Darwin to begin The Origin of Species eight years after his visit there. To preserve the unique wildlife on the islands, the Ecuadorian government made the entire archipelago a national park in 1959. Each year roughly 60,000 tourists visit these islands to experience what Darwin did over a century and a half ago. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  4. Earthquakes Versus Surface Deformation: Qualitative and Quantitative Relationships From The Aegean

    Pavlides, S.; Caputo, R.

    Historical seismicity of the Aegean Region has been revised in order to associate major earthquakes to specific seismogenic structures. Only earthquakes associated to normal faulting have been considered. All available historical and seismotectonic data relative to co-seismic surface faulting have been collected in order to evaluate the surface rup- ture length (SRL) and the maximum displacement (MD). In order to perform Seismic Hazard analyses, empirical relationships between these parameters and the magnitude have been inferred and the best fitting regression functions have been calculated. Both co-seismic fault rupture lengths and maximum displacements show a logarithmic re- lationships, but our data from the Aegean Region have systematically lower values than the same parameters world-wide though they are similar to those of the East- ern Mediterranean-Middle East region. The upper envelopes of our diagrams (SRL vs Mw and MD vs Mw) have been also estimated and discussed, because they give useful information of the wort-case scenarios; these curces will be also discussed. Further- more, geological and morphological criteria have been used to recognise the tectonic structures along which historical earthquakes occurred in order to define the geolog- ical fault length (GFL). Accordingly, the SRL/GFL ratio seems to have a bimodal distribution with a major peak about 0.8-1.0, indicating that several earthquakes break through almost the entire geological fault length, and a second peak around 0.5, re- lated to the possible segmentation of these major neotectonic faults. In contrast, no relationships can be depicted between the SRL/GFL ratio and the magnitude of the corresponding events.

  5. Po 210 in the Turkish coast of the Aegean sea ecosystem

    Full text: Po 210 is a natural radionuclide which constitutes the major source of natural radiation received by humans through the consumption of food and contributes more to the total radiation dose than environmental levels of anthropogenic radionuclides, such as Cs 137 and Pu 239, 240. For Turkish Coast of Aegean Sea Ecosystem, although there some investigations presently available on some natural radionuclides and gross radioactivity concentrations, data on Po 210 in the sea water, bottom sediment and marine biota are very scarce. The aim of the present study is to improve our knowledge about the levels of radioactive polonium along Aegean Turkish Coastal zone and also assess its enhancement from the fosil fuel industry like coal-fired power plants (CPPs), oil industry and from phosphate industry, all located along the coast and also from the discharge of a number streams and rivers in the region. This paper introduces an extensive set of data and related results on Po 210 in surface sea water, bottom sediments, fishes and mussels (Mytilus galloprovincialis) obtained from 6 stations (Canakkale, Dikili, Foca, Ceshme, Didim and Bodrum) along the coast in the period of 2004-2005. In the bottom sediments, Po 210 concentration varies between 21±1 and 214±24 Bq kg-1 dry wt with an average value of 70±7 Bq kg-1. The concentrations in surface water of the sea during the sampling period are around 0.016±0.001 Bq l-1. Amongst the fishes, small pelagic plankton feding fish like anchovy (Engraulis encrasicolus) and sardine (Sardine plichardus) tend to accumulate more Po 210. The concentration of Po 210 in mussels (Mytilus galloprovincialis) varies between 55±5 and 2288±124 Bq kg-1 which is in general higher than those given in literature for other countries. The highest Po 210 concentration belongs to Didim mussels for winter time with a shell length of 4-6 cm

  6. Modeling of Arc Force in Plasma Arc Welding

    GAO Zhonglin; HU Shengsun; YIN Fengliang; WANG Rui


    A three. dimensional mathematical model for the transferred-type argon arc was developed to describe arc force on the anode surface. The software ANSYS was employed to solve the model. The model includes a part of torch and tungsten electrode to achieve m ore reasonable results. The arc temperature and flow fields were derived. And the influences of welding parameters on arc force were also studied. The simulated results show that arc pressure at the anode are dependent on the welding current, plasma gas flow rate and electrode neck-in, while not sensitive to arc length.

  7. Climate variability and socio-environmental changes in the northern Aegean (NE Mediterranean) during the last 1500 years

    Gogou, Alexandra; Triantaphyllou, Maria; Xoplaki, Elena; Izdebski, Adam; Parinos, Constantine; Dimiza, Margarita; Bouloubassi, Ioanna; Luterbacher, Juerg; Kouli, Katerina; Martrat, Belen; Toreti, Andrea; Fleitmann, Dominik; Rousakis, Gregory; Kaberi, Helen; Athanasiou, Maria; Lykousis, Vasilios


    We provide new evidence on sea surface temperature (SST) variations and paleoceanographic/paleoenvironmental changes over the past 1500 years for the north Aegean Sea (NE Mediterranean). The reconstructions are based on multiproxy analyses, obtained from the high resolution (decadal to multi-decadal) marine record M2 retrieved from the Athos basin. Reconstructed SSTs show an increase from ca. 850 to 950 AD and from ca. 1100 to 1300 AD. A cooling phase of almost 1.5 °C is observed from ca. 1600 AD to 1700 AD. This seems to have been the starting point of a continuous SST warming trend until the end of the reconstructed period, interrupted by two prominent cooling events at 1832 ± 15 AD and 1995 ± 1 AD. Application of an adaptive Kernel smoothing suggests that the current warming in the reconstructed SSTs of the north Aegean might be unprecedented in the context of the past 1500 years. Internal variability in atmospheric/oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north Aegean Sea over the past 1500 years. The marked temperature drop of approximately ∼2 °C at 1832 ± 15 yr AD could be related to the 1809 ΑD 'unknown' and the 1815 AD Tambora volcanic eruptions. Paleoenvironmental proxy-indices of the M2 record show enhanced riverine/continental inputs in the northern Aegean after ca. 1450 AD. The paleoclimatic evidence derived from the M2 record is combined with a socio-environmental study of the history of the north Aegean region. We show that the cultivation of temperature-sensitive crops, i.e. walnut, vine and olive, co-occurred with stable and warmer temperatures, while its end coincided with a significant episode of cooler temperatures. Periods of agricultural growth in Macedonia coincide with periods of warmer and more stable SSTs, but further exploration is required in order to identify the causal links behind the observed phenomena. The Black Death

  8. Climate variability and socio-environmental changes in the northern Aegean (NE Mediterranean) during the last 1500 years

    Gogou, Alexandra; Triantaphyllou, Maria; Xoplaki, Elena; Izdebski, Adam; Parinos, Constantine; Dimiza, Margarita; Bouloubassi, Ioanna; Luterbacher, Juerg; Kouli, Katerina; Martrat, Belen; Toreti, Andrea; Fleitmann, Dominik; Rousakis, Gregory; Kaberi, Helen; Athanasiou, Maria; Lykousis, Vasilios


    We provide new evidence on sea surface temperature (SST) variations and paleoceanographic/paleoenvironmental changes over the past 1500 years for the north Aegean Sea (NE Mediterranean). The reconstructions are based on multiproxy analyses, obtained from the high resolution (decadal to multi-decadal) marine record M2 retrieved from the Athos basin. Reconstructed SSTs show an increase from ca. 850 to 950 AD and from ca. 1100 to 1300 AD. A cooling phase of almost 1.5 °C is observed from ca. 1600 AD to 1700 AD. This seems to have been the starting point of a continuous SST warming trend until the end of the reconstructed period, interrupted by two prominent cooling events at 1832 ± 15 AD and 1995 ± 2 AD. Application of an adaptive Kernel smoothing suggests that the current warming in the reconstructed SSTs of the north Aegean might be unprecedented in the context of the past 1500 years. Internal variability in atmospheric/oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north Aegean Sea over the past 1500 years. The marked temperature drop of approximately ~2°C at 1832 ± 15 yr AD could be related to the 1809 ΑD 'unknown' and the 1815 AD Tambora volcanic eruptions. Paleoenvironmental proxy-indices of the M2 record show enhanced riverine/continental inputs in the northern Aegean after ca. 1450 AD. The palaeoclimatic evidence derived from M2 record is combined with a socio-environmental study of the history of the north Aegean region. We show that the cultivation of temperature-sensitive crops, i.e. walnut, vine and olive, co-occurred with stable and warmer temperatures, while its end coincided with a significant episode of cooler temperatures. Periods of agricultural growth in Macedonia coincide with periods of warmer and more stable SSTs, but further exploration is required in order to identify the causal links behind the observed phenomena. The Black Death likely

  9. ALICE-ARC integration

    AliEn or Alice Environment is the Grid middleware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The inter-operation has two aspects, one is the data management part and the second the job management aspect. The first aspect was solved by using dCache across NDGF to handle data. Therefore, we will concentrate on the second part. Solving it, was somewhat cumbersome, mainly due to the different computing models employed by AliEn and ARC. AliEN uses an Agent based pull model while ARC handles jobs through the more 'traditional' push model. The solution comes as a module implementing the functionalities necessary to achieve AliEn job submission and management to ARC enabled sites

  10. Consolidating NASA's Arc Jets

    Balboni, John A.; Gokcen, Tahir; Hui, Frank C. L.; Graube, Peter; Morrissey, Patricia; Lewis, Ronald


    The paper describes the consolidation of NASA's high powered arc-jet testing at a single location. The existing plasma arc-jet wind tunnels located at the Johnson Space Center were relocated to Ames Research Center while maintaining NASA's technical capability to ground-test thermal protection system materials under simulated atmospheric entry convective heating. The testing conditions at JSC were reproduced and successfully demonstrated at ARC through close collaboration between the two centers. New equipment was installed at Ames to provide test gases of pure nitrogen mixed with pure oxygen, and for future nitrogen-carbon dioxide mixtures. A new control system was custom designed, installed and tested. Tests demonstrated the capability of the 10 MW constricted-segmented arc heater at Ames meets the requirements of the major customer, NASA's Orion program. Solutions from an advanced computational fluid dynamics code were used to aid in characterizing the properties of the plasma stream and the surface environment on the calorimeters in the supersonic flow stream produced by the arc heater.