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Sample records for aegean extensional province

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  2. Enigmatic compressional structures in an extensional province: Eku field, OML 67, offshore Nigeria

    SciTech Connect

    Quinones, M.; Evans, R.; Alofe, K.; Onyeise, B.

    1996-12-31

    Acquisition of 3-D seismic data over OML 67-70 and a detailed reservoir description study done on the Eku field, have allowed identification of previously unrecognized compressional features. Situated within a depocenter between arcuate normal growth faults, the Eku structure consists of a shale-cored anticlinal fold and fold-and-thrust separated by a zone of lateral displacement. The crests of the folds have been eroded at a major unconformity at the base of the Qua Iboe shale (Early Pliocene). In the absence of definitive biostratigraphic data, correlations among the various fault-blocks are based on the character of sedimentary packages and sequences on wireline logs. Combined with analysis of the geometry of faults and folds, the correlations support a description of pulsatory movement of folding and faulting, that ultimately culminated in extensional reactivation of earlier regional extension and the not coincident. The effect of the anticipated reservoir sections, and deformation, both compressional, was gravity-driven and on shale detachments. A working hypothesis to explain the disparity in direction of earlier extension and subsequent compression is that thermal expansion that accompanied formation of the Cameroon volcanic line to the east of the Niger Delta in Miocene time, caused a change in the direction of structuring, allowing downslope gravity-driven compression to be superimposed on pre-existing extensional features.

  3. Enigmatic compressional structures in an extensional province: Eku field, OML 67, offshore Nigeria

    SciTech Connect

    Quinones, M.; Evans, R. ); Alofe, K.; Onyeise, B. )

    1996-01-01

    Acquisition of 3-D seismic data over OML 67-70 and a detailed reservoir description study done on the Eku field, have allowed identification of previously unrecognized compressional features. Situated within a depocenter between arcuate normal growth faults, the Eku structure consists of a shale-cored anticlinal fold and fold-and-thrust separated by a zone of lateral displacement. The crests of the folds have been eroded at a major unconformity at the base of the Qua Iboe shale (Early Pliocene). In the absence of definitive biostratigraphic data, correlations among the various fault-blocks are based on the character of sedimentary packages and sequences on wireline logs. Combined with analysis of the geometry of faults and folds, the correlations support a description of pulsatory movement of folding and faulting, that ultimately culminated in extensional reactivation of earlier regional extension and the not coincident. The effect of the anticipated reservoir sections, and deformation, both compressional, was gravity-driven and on shale detachments. A working hypothesis to explain the disparity in direction of earlier extension and subsequent compression is that thermal expansion that accompanied formation of the Cameroon volcanic line to the east of the Niger Delta in Miocene time, caused a change in the direction of structuring, allowing downslope gravity-driven compression to be superimposed on pre-existing extensional features.

  4. Transient shortening strain across an active extensional fault, Basin and Range Province, north-central Nevada, USA, based on geodetic and paleoseismologic data.

    NASA Astrophysics Data System (ADS)

    Friedrich, A.; Wernicke, B.; Lee, J.; Sieh, K.

    2003-04-01

    The northern Basin and Range province is one of the largest continental extensional regions on earth. At 40 degrees N latitude, the province is 800 km wide and consists of 15 and 20 N-S striking normal faults. These faults accommodated mainly east-west directed extension of tens of kilometers since Mid-Miocene time and recent geodetic surveys show that extension is still active today at a rate of ~1.5 cm/yr across the province (e.g., Bennett et al. 2000; Thatcher et al. 1999). The distribution of this geodetically measurable strain accumulation within the province, however, contradicts geologic observations across some of the active normal faults. For example, coordinated geologic and geodetic measurements across the Crescent Valley fault (CVF), north-central Nevada, reveal a profound mismatch in deformation rates. Since 1996, the two ranges on either side of the CVF have been moving toward each other at ca. 2 mm/yr, indicating shortening. In contrast, new reconnaissance mapping and paleoseismological analyses along the CVF also indicate that this fault is one of the more active normal faults of the Basin and Range province. The 50 km long Cortez Mountains range front is characterized by relief of up to 1.3 km, steep (up to 36 degrees) triangular facets, and young (late Pleistocene to late Holocene) alluvial fans cut by normal fault scarps. Vertical displacement across the CVF is ca. 3 km; since 15 Ma the average long-term vertical displacement rate is ca. 0.2 mm/yr. Topographic profiling shows that fault scarps, 2-7 m high, are the result of a single rupture event and cut late Holocene alluvial fans. A trench across a faulted alluvial fan at Fourmile Canyon reveals a vertical displacement of 4.5 m distributed across two normal faults. 14C analyses on charcoal from a buried offset surface in the hanging wall of the trench and from the base of the overlying colluvial wedge tightly bracket the age of the most recent earthquake to between 2.8 +- 0.1 and 2.7 +- 0.1 ka

  5. Apatite fission track evidence for Miocene extensional faulting east-central Nevada, northern Basin and Range province

    SciTech Connect

    Miller, E.L.; Dumitru, T.A. . Geology Dept.); Gans, P.B. . Geological Sciences Dept.); Brown, R.W. . Geology Dept.)

    1993-04-01

    Apatite fission track ages indicates that a large component of motion along many of the present range-bounding faults occurred in the Early to Middle Miocene, tilting and uplifting rocks through the apatite annealing zone (120--60 C) between 18--13 Ma (n = 20, Deep Creeks), 18--15 Ma (northern Snake Range, n = 20), 25--17 Ma (n = 7, southern Snake Range), 24--15 Ma (Egan Range, n = 6), 23--18 Ma (Kern Mts., n = 2) and 28--16 ma (Schell Creek Range, n = 2). Long track length distributions indicate rapid cooling through the 120--60 C interval followed by residence at low, near surface temperatures. The data set also indicates that the combined Deep Creek-Kern Mountains-northern and southern Snake Range constitutes a single coherent footwall crustal block beneath a > 150 km-long system of east-dipping Miocene faults which includes at least the eastern portions of faults that have been mapped as the Snake Range decollement (NSRD). Conglomerates deposited in hanging wall basins along this fault system contain metamorphic and granitic boulders whose FT ages are coeval with footwall unroofing. The deposits themselves are now known to be younger than previously reported (Oligocene) as ages from boulders are Miocene. The thick (> 2 km) sequences of synorogenic conglomerate indicates rapid unroofing; large slide blocks attest to generation of steep, fault-controlled topography. Faults that cut this sequence are now known to be younger than 15 Ma. Thus, protracted extensional faulting affected the region, beginning in the Early Oligocene and continuing to the Recent, but a significant part of this extension, including a large component of the slip on the NSRD, was accomplished in the Early to Middle Miocene. Data from this region is compatible with a growing base of apatite fission track data from elsewhere in the northern Basin and Range, which, together with geologic relationships, suggest an important episode of Miocene extension and Basin and Range development.

  6. Subduction and slab tearing dynamics constrained by thermal anomalies in the Anatolia-Aegean region

    NASA Astrophysics Data System (ADS)

    Roche, Vincent; Guillou-Frottier, Laurent; Jolivet, Laurent; Loiselet, Christelle; Bouchot, Vincent

    2015-04-01

    Most previous geodynamic studies treat subduction zones with backward migration (rollback), slab tearing or slab breakoff by numerical or laboratory experiments and by integrating seismicity, tomography data and geochemical studies. Here we investigate these processes in the Aegean-Anatolian domain and particularly the western side of Turkey (western Anatolia) by incorporating thermal regime of the crust, and in particular the geothermal fields as anomalies that could reflect the thermal state of Aegean subduction zone at depth. This domain is characterized by 1) extensional crustal deformation which progressively localized during the Aegean slab retreat from late Eocene to Present, enabling the development of a hot backarc domain; this extension accelerated between 15 and 8 Ma coeval with a fast rotation of the Hellenides and 2) since the latest Miocene, extension is coupled with the development of the North Anatolian Fault that accommodates the westward escape of the Anatolian block. Both the acceleration of extension in the Middle Miocene and the recent escape of Anatolia have been proposed to result from several slab tearing events, the first one being located below western Turkey and the Eastern Aegean Sea, a second one below eastern Turkey and a last one below the Corinth Rift (Faccenna et al., 2006; Jolivet et al., 2013). The distribution of magmatism and mineral resources has been suggested to be largely controlled by these retreat and tearing events (Menant et al., submitted). The development of a widespread active geothermal province in western Anatolia is unlikely to simply result from the Quaternary magmatism whose volcanism part has a too limited extent. Conversely, the long wavelength east-west variation of surface heat flow density could reflect deep thermal processes in the lower crust and/or deeper, and we thus look for possible connections with larger-scale mantle dynamics. We use the distribution of thermal anomalies at different scales and the 3

  7. Parameters influencing the location and characteristics of volcanic eruptions in a youthful extensional setting: Insights from the Virunga Volcanic Province, in the Western Branch of the East African Rift System

    NASA Astrophysics Data System (ADS)

    Smets, Benoît; d'Oreye, Nicolas; Kervyn, Matthieu; Kervyn, François

    2016-04-01

    The East African Rift System (EARS) is often mentioned as the modern archetype for rifting and continental break-up (Calais et al., 2006, GSL Special Publication 259), showing the complex interaction between rift faults, magmatism and pre-existing structures of the basement. Volcanism in the EARS is characterized by very active volcanoes, several of them being among the most active on Earth (Wright et al., 2015, GRL 42). Such intense volcanic activity provides useful information to study the relationship between rifting, magmatism and volcanism. This is the case of the Virunga Volcanic Province (VVP) located in the central part of the Western Branch of the EARS, which hosts two of the most active African volcanoes, namely Nyiragongo and Nyamulagira. Despite the intense eruptive activity in the VVP, the spatial distribution of volcanism and its relationship with the extensional setting remain little known. Here we present a study of the interaction between tectonics, magmatism and volcanism at the scale of the Kivu rift section, where the VVP is located, and at the scale of a volcano, by studying the dense historical eruptive activity of Nyamulagira. Both the complex Precambrian basement and magmatism appear to contribute to the development of the Kivu rift. The presence of transfer zones north and south of the Lake Kivu rift basin favoured the development of volcanic provinces at these locations. Rift faults, including reactivated Precambrian structures influenced the location of volcanism within the volcanic provinces and the rift basin. At a more local scale, the historical eruptive activity of Nyamulagira highlights that, once a composite volcano developed, the gravitational stress field induced by edifice loading becomes the main parameter that influence the location, duration and lava volume of eruptions.

  8. New constraints on the active tectonic deformation of the Aegean

    USGS Publications Warehouse

    Nyst, M.; Thatcher, W.

    2004-01-01

    Site velocities from six separate Global Positioning System (GPS) networks comprising 374 stations have been referred to a single common Eurasia-fixed reference frame to map the velocity distribution over the entire Aegean. We use the GPS velocity field to identify deforming regions, rigid elements, and potential microplate boundaries, and build upon previous work by others to initially specify rigid elements in central Greece, the South Aegean, Anatolia, and the Sea of Marmara. We apply an iterative approach, tentatively defining microplate boundaries, determining best fit rigid rotations, examining misfit patterns, and revising the boundaries to achieve a better match between model and data. Short-term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long-term kinematics. We find that present day Aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them. The RMS misfit of model to data is about 2-sigma, very good when compared to the typical match between coseismic fault models and GPS data. The simplicity of the microplate description of the deformation and its good fit to the GPS data are surprising and were not anticipated by previous work, which had suggested either many rigid elements or broad deforming zones that comprise much of the Aegean region. The isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions. Strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain/year (nstrain/year, 10-9/year), 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries. Lower strain rates may exist elsewhere withi the microplates but are only resolved in Anatolia, where extension of 13 ?? 4 nstrain/ year is required by the data. Our results suggest that despite the detailed complexity of active continental deformation

  9. A key extensional metamorphic complex reviewed and restored: The Menderes Massif of western Turkey

    NASA Astrophysics Data System (ADS)

    van Hinsbergen, Douwe J. J.

    2010-09-01

    This paper provides a review of the structure and metamorphism of the Menderes Massif in western Turkey, and subsequently a map-view restoration of its Neogene unroofing history. Exhumation of this massif — among the largest continental extensional provinces in the world — is generally considered to have occurred along extensional detachments with a NE-SW stretching direction. Restoration of the early Miocene history, however, shows that these extensional detachments can only explain part of the exhumation history of the Menderes Massif, and that NE-SW stretching can only be held accountable for half, or less, of the exhumation. Restoration back to ˜ 15 Ma is relatively straightforward, and is mainly characterised by a previously reported 25-30° vertical axis rotation difference between the northern Menderes Massif, and the Southern Menderes Massif and overlying HP nappes, Lycian Nappes and Bey Dağları about a pivot point close to Denizli. To the west of this pole, the rotation was accommodated by exhumation of the Central Menderes core complex since middle Miocene times, and to the east probably by shortening. At the end of the early Miocene, the Menderes Massif formed a rectangular, NE-SW trending tectonic window of ˜ 150 × 100 km. Geochronology suggests unroofing between ˜ 25 and 15 Ma. The north-eastern Menderes Massif was exhumed along the early Miocene Simav detachment, over a distance of ≤ 50 km. The accommodation of the remainder of the exhumation is enigmatic, but penetrative NE-SW stretching lineations throughout the Menderes Massif suggest a prominent role of NE-SW extension. This, however, requires that the eastern margin of the Menderes Massif, bordering a region without significant extension, is a transform fault with an offset of ˜ 150 km, cutting through the Lycian Nappes. For this, there is no evidence. The Lycian Nappes — a non-metamorphic stack of sedimentary thrust slices and an overlying ophiolite and ophiolitic mélange

  10. Extensional Acceleration of Diapiric Tectonics

    NASA Astrophysics Data System (ADS)

    Bailey, R. C.; Pearse, J.

    2005-12-01

    A decade ago, Glazner pointed out that density anomalies such as mafic plutons in reheated continental crust will drive vertical tectonics by ductile remobilization and subsidence as a result of buoyancy forces, and that this can be a relatively rapid process. We have examined the surface expression of this process using finite element modeling, and shown in previous work that a basin develops at the surface, succeeded by exhumation into a dome if crustal reheating is strong enough. The two-dimensional finite-element code models the coupled deformation and heat flow in a density-stratified crust (from 2.5 at the surface to about 2.9 at the Moho) with thermally activated viscoelasticity (with viscosity ranging from 1019 Pa-s after reheating in the middle of the crustal ductile channel at 25 km depth, to 1026 Pa-s at the Earth's surface). The most extreme plausible case investigated used mafic plutons (density 3.0) comparable with the Keeweenawan volcanics of the mid-continent gravity high under the Michigan Basin, embedded with centres between 8 and 15 km depth, and a reheating event comparable with that under the Basin and Range province today (about 100 mW/m2). In this case, subsidence of up to 7 km was followed by exhumation of up to 10 km, leaving a dome. Precise numbers depend on the embedding depth of the pluton and the amount of erosion assumed. Deeper embedding leads to earlier remobilization but reduced vertical displacements at the surface. Anything less than full erosion leads to surface topography but smaller vertical displacements. Basin and dome widths are determined by the flexural parameter of the thermally thinned elastic layer of the crust, and are of order 60 km in the models here. In the absence of regional deviatoric stresses, the subsidence phase lasts of the order of 25 Ma, and the exhumation phase about 10 Ma. However, with extensional stresses present, producing extensional strain rates of the order of 10-15 s-1, the modelled timescales for

  11. A comparison between two hydrothermally formed extensional environment related kaolin deposits: Balikesir-Duvertepe, Turkey and Kline Mountain, Sierra County, New Mexico

    SciTech Connect

    Isik, I.; Clark, K.F. . Dept. of Geological Sciences)

    1992-01-01

    Economically important and hydrothermally formed kaolin deposits are often found within rift lithologic units, formed as a result of interaction of physical and geochemical processes in the extensional environment. The kaolin deposits of Balikesir--Duvertepe, Turkey and Kline Mountain, Sierra County, New Mexico, studied herein, are examples of this type. The Balikesir--Duvertepe district has been known as the most productive kaolin district in Turkey. Total reserves are estimated at 15 million metric tons. Located in the active Simav Graben produced by the subduction of the African Plate under the Aegean region, the kaolin deposits occur irregularly and variably in quality as a result of hydrothermal alteration of Neogene tuffs. The Kline Mountain kaolin deposit was formed as a result of advanced argillic alteration on the southeastern edge of the Mogollon--Datil volcanic field, which is related to the extensional environment of Basin and Range province and the Rio Grande rift. Its reserve is reported as 200 million metric tons of altered tuffs. The two deposits show striking similarities: extensional related rock units, intense in situ hydrothermal alteration, mineral content, seismic activity, alunite contamination, chemical composition, and intense silicification. The deposits also display some differences: regional climate, the intensity of hydrothermal alteration and the elapsed time causing relatively complete replacement in the Turkish deposit compared to that in NM. The Balikesir--Duvertepe district has been the center of kaolin marketing for use chiefly in ceramic, paper, and white cement, while the Kline Mountain kaolin had been exploited primarily for paper and ceramic tile as a coating; and in the oil industry as a filler and absorbent material.

  12. Frequent underwater volcanism in the central Aegean Sea

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  13. Late Cenozoic extensional faulting in Central-Western Peloponnesus, Greece

    NASA Astrophysics Data System (ADS)

    Skourtsos, E.; Fountoulis, I.; Mavroulis, S.; Kranis, H.

    2012-04-01

    A series of forearc-dipping, orogen-parallel extensional faults are found in the central-western Peloponnesus, (south-western Aegean) which control the western margin of Mt Mainalon. The latter comprises HP/LT rocks of the Phyllites-Quartzites Unit (PQ), overlain by the carbonates and flysch of the Tripolis Unit while the uppermost nappe is the Pindos Unit, a sequence of Mesozoic pelagic sequence, topped by a Paleocene flysch. Most of the extensional structures were previously thought of as the original thrust between the Pindos and Tripolis Units. However, the cross-cutting relationships among these structures indicate that these are forearc (SW-dipping) extensional faults, downthrowing the Pindos thrust by a few tens or hundreds of meters each, rooting onto different levels of the nappe pile. In SW Mainalon the lowermost of the extensional faults is a low-angle normal fault dipping SW juxtaposing the metamorphic rocks of the PQ Unit against the non-metamorphic sequence of the Tripolis Unit. High-angle normal faults, found further to the west, have truncated or even sole onto the low-angle ones and control the eastern margin of the Quaternary Megalopolis basin. All these extensional structures form the eastern boundary of a series of Neogene-Quaternary tectonic depressions, which in turn are separated by E-W horsts. In the NW, these faults are truncated by NE to NNE-striking, NW-dipping faults, which relay the whole fault activity to the eastern margin of the Pyrgos graben. The whole extensional fault architecture has resulted (i) in the Pindos thrust stepping down from altitudes higher than 1000 m in Mainalon in the east, to negative heights in North Messinia and Southern Ilia in the west; and (ii) the gradual disappearance of the Phyllite-Quartzite metamorphics of Mainalon towards the west. The combination of these extensional faults (which may reach down to the Ionian décollement) with the low-angle floor thrusts of the Pindos, Tripolis and Ionian Units leads

  14. Mantle convection in the Middle East: Reconciling Afar upwelling, Arabia indentation and Aegean trench rollback

    NASA Astrophysics Data System (ADS)

    Faccenna, Claudio; Becker, Thorsten W.; Jolivet, Laurent; Keskin, Mehmet

    2013-08-01

    The Middle East region represents a key site within the Tethyan domain where continental break-up, collision, backarc extension and escape tectonics are kinematically linked together. We perform global mantle circulation computations to test the role of slab pull and mantle upwellings as driving forces for the kinematics of the Arabia-Anatolia-Aegean (AAA) system, evaluating different boundary conditions and mantle density distributions as inferred from seismic tomography or slab models. Model results are compared with geodetically inferred crustal motions, residual topography, and shear wave splitting measurements. The AAA velocity field with respect to Eurasia shows an anti-clockwise toroidal pattern, with increasing velocities toward the Aegean trench. The best match to these crustal motions can be obtained by combining the effect of slab pull exerted in the Aegean with a mantle upwelling underneath Afar and, more generally, with the large-scale flow associated with a whole mantle, Tethyan convection cell. Neogene volcanism for AAA is widespread, not only in the extensional or subduction settings, but also within plates, such as in Syria-Jordan-Israel and in Turkey, with geochemical fingerprints similar of those of the Afar lava. In addition, morphological features show large uplifting domains far from plate boundaries. We speculate that the tectonic evolution of AAA is related to the progressive northward entrainment of upwelling mantle material, which is itself associated with the establishment of the downwelling part of a convection cell through the segmented Tethyan slab below the northern Zagros and Bitlis collision zone. The recently established westward flow dragged Anatolia and pushed the Aegean slab south-westward, thus accelerating backarc extension. Our model reconciles Afar plume volcanism, the collision in the Bitlis mountains and northern Zagros, and the rapid increase of Aegean trench rollback in a single coherent frame of large scale mantle

  15. Contemplating autoimmunity in the Aegean islands.

    PubMed

    Walker, Lucy S K; Ziegler, Steven; Becher, Burkhard

    2016-03-01

    The Greek island of Crete became host to lively discussions on immunoregulation as experts from around the world gathered for the 7th Aegean Conference on Autoimmunity in September 2015. PMID:26882250

  16. Inversion of Extensional Sedimentary Basins

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne J. H.; Pfiffner, O. Adrian

    The evolution of extensional sedimentary basins is governed by the surrounding stress field and can, therefore, be expected to be highly sensitive to variations in these stresses. Important changes in basin geometry are to be expected in the case of an even short-lived reversal from extension to compression. We investigate the evolu- tion of fold and thrust structures which form in compression after extension, when basin forming processes have come to a complete stop. To this purpose, we use a two- dimensional, viscoplastic model and start our experiments from a pre-existing exten- sional geometry. We illustrate the sensitivity of the evolving structures to inherited extensional geometry, sedimentary and erosional processes, and material properties. One series of our model experiments involves the upper- to middle crust only in order to achieve a high detail in the basin area. We find that our results agree with examples from nature and analogue studies in, among others, the uplift and rotation of syn-rift sediments, the propagation of shear zones into the post-rift sediments and, in specific cases, the development of back-thrusts or basement short-cut faults. We test the out- come of these models by performing a second series of model simulations in which basins on a continental margin are inverted through their progressive approach of a subduction zone. These latter models are on the scale of the whole upper mantle.

  17. Moment tensor inversion of the January 8, 2013 (Mw=5.7) and May 24, 2014 (Mw 6.8) North Aegean Earthquakes: seismicity and active tectonics of the North Aegean Region

    NASA Astrophysics Data System (ADS)

    Kalafat, Dogan; Kekovali, Kivanc; Pinar, Ali

    2015-04-01

    parallel to the North Aegean Trough (NAT). Strike slip faulting is changing to oblique, with significant component of extension, as one goes from the Aegean to the coastal area of NW and Western Turkey. The sources region of the North Aegean earthquakes is influenced by both the Aegean extensional regime and the strike-slip regime in the western part of the North Anatolin Fault Zone. Strike-slip faulting is changing to oblique, with significant component of extension, as one goes from the Aegean to the coastal area of Western Turkey. This study was supported by Bogazici University Research Projects Commission under SRP/BAP project No. 6040 and MarDIM SATREPS project.

  18. GPS-Constrained Microplate Kinematics and Plio-Pleistocene Tectonic Evolution of the North Anatolian Fault and North Aegean Sea

    NASA Astrophysics Data System (ADS)

    Thatcher, W.

    2004-12-01

    tectonics thus has several strengths but some clear limitations. Using only the GPS constrained microplate model and no adjusted parameters, backwards extrapolation over the past 10 Ma explains the observed large scale Plio-Pleistocene extension of the North Aegean and its evolution towards present-day strike-slip tectonics via the much-discussed propagation of the North Anatolian fault into the North Aegean. The spatial distribution of Plio-Pleistocene sediments and large-offset normal faults is considerably more complex than the simple extensional faulting pattern expected from the plate kinematic extrapolation. The detailed pattern of Plio-Pleistocene extension is compatible with several abrupt jumps in the principal zone of extension from NE to SW with time, which would account for the localized sediment accumulations in the Kavala and Thermaikos basins and the smaller than expected offset of the North Anatolian fault in the Dardanelles. The relative youth of extension in the Gulf of Corinth indicates the current geometry and motion of the Central Greece microplate is correspondingly recent, so the extrapolated rotation of this block during the past 10 Ma cannot be correct. Extension prior to about 1 Ma BP must have occurred elsewhere, perhaps in the central and southern Aegean.

  19. Aquatic animal resources in Prehistoric Aegean, Greece.

    PubMed

    Mylona, Dimitra

    2014-12-01

    This paper explores the early stages in the history of fishing in the Aegean Sea in Greece, and highlights its formative phases and its specific characteristics in different points in time. This is testified by various physical remains, such as fish bones, fishing tools, and representations in art, which are gathered in the course of archaeological research. The aquatic resources in the Aegean Sea have been exploited and managed for millennia by communities that lived near the water and often made a living from it. The earliest evidence for a systematic, intensive exploitation of marine resources in the Aegean Sea dates to the Mesolithic, eleven millennia ago. In the Neolithic period, the adoption of a sedentary, agro-pastoral way of life led to a reduction in the intensity of fishing and shellfish gathering. Its importance as an economic resource remained high only in certain regions of rich, eutrophic waters. In the Bronze Age, an era of social complexity and centralized economy, the exploitation of aquatic, mostly marine, resources became a complex, multi-faceted activity which involved subsistence, industry and ideology. The range of preferred fish and invertebrate species, the fishing technology, and the processing of fish and shellfish in order to produce elaborate foods or prestige items are all traceable aspects of the complex relationship between humans and the aquatic resources throughout the prehistory of fishing and shellfish gathering in the Aegean area. The broadening of collaboration between archaeology and physical sciences offers new means to explore these issues in a more thorough and nuanced manner. PMID:25984485

  20. Petroleum exploration and geology of the Aegean

    SciTech Connect

    Bartling, T.C.; Gips, J.

    1988-08-01

    The present-day Aegean Sea covers several graben and/or half-graben basins filled with more than 12,000 ft of sedimentary rocks. The normal faulting observed on seismic record sections indicates a tensional tectonic regime. There is a marked coincidence of modern basins and bathymetric highs with paleobasins and highs. A stratigraphic section of marine clastics of Eocene through Miocene-Pliocene age have been encountered in the seven wildcat wells drilled. Cretaceous-age rocks must be considered basement for petroleum exploration because, except for an area in the eastern Aegean, Cretaceous and older rocks were metamorphosed during the Alpine orogenies. The Eocene is a transgressive clastic sequence. The Oligocene is conformable with the underlying Eocene. The Miocene is predominantly a regressive clastic sequence. This series ended with evaporitic conditions. The Messinian evaporite is an excellent seismic marker and is the seal for the one producing field in the Aegean Sea. Source rocks and reservoir rocks are found in both the Eocene and the Miocene. Four of the seven wildcats drilled have encountered hydrocarbon shows. Prinos field, discovered in 1974, was put on production in 1981 and is currently producing at design capacity of 25,000 to 28,000 bbl of oil per day. Cumulative production is approximately 50 million bbl. Prinos field is only 7 mi from metamorphic basement outcrop, yet field wells have penetrated more than 10,000 ft of Tertiary marine clastics.

  1. Extensional Rheology of Granular Staples

    NASA Astrophysics Data System (ADS)

    Franklin, Scott

    2013-03-01

    Collections of U-shaped granular materials (e.g. staples) show a surprising resistance to being pulled apart. We conduct extensional stress-strain experiments on staple piles with vary arm/spine (barb) ratio. The elongation is not smooth, with the pile growing in bursts, reminiscent of intruder motion through ordinary and rod-like granular materials. The force-distance curve shows a power-law scaling, consistent with previous intruder experiments. Surprisingly, there is significant plastic creep of the pile as particles rearrange slightly in response to the increasing force. There is a broad distribution of yield forces that does not seem to evolve as the pile lengthens, suggesting that each yield event is independent of the pile's history. The distribution of yield forces can be interpreted in the context of a Weibullian weakest-link theory that predicts the maximum pile strength to decrease sharply with increasing pile length. From this interpretation arise length and force scales that may be used to characterize the sample. This research supported in part by the NSF (CBET-#1133722) and ACS-PRF (#51438-UR10).

  2. Afar plume, Anatolia escape and Aegean rollback are features of the Arabia-Middle East convection system

    NASA Astrophysics Data System (ADS)

    Becker, T. W.; Faccenna, C.; Jolivet, L.

    2012-12-01

    The Arabia-Anatolia-Aegean (AAA) system represents a key site within the Tethyan domain where continental break-up, collision, and escape tectonics are linked together. This offers an opportunity to study the forces that drive and deform the continental lithosphere within a convecting mantle. We perform global mantle circulation computations to test the role of slab pull and mantle upwellings as driving forces for the kinematics of the AAA system, evaluating different boundary conditions and mantle density distributions as inferred from seismic tomography or slab models. Model result are compared with geodesy, residual topography and shear wave splitting. The AAA velocity field with respect to Eurasia shows an anti-clockwise toroidal pattern, with increasing velocities toward the Aegean trench. The best match to these crustal motions can be obtained by combining the effect of slab pull exerted in the Aegean with a mantle upwelling underneath Afar and, more generally, with the large-scale flow associated with a whole-mantle, Tethyan convection cell. Neogene volcanism for AAA is not confined to extensional or subduction settings but also found within plate interiors, such as in Syria-Jordan-Israel and in the collisional belt. In addition, morphological feature show large uplifting domains far from plate boundary. Such intraplate tectonics may all be associated with northward plume transport and the establishment of the Tethyan convection cell upon slab segmentation. Our model reconciles Afar plume volcanism, the collision on the Bitlis, and the rapid increase of Aegean trench rollback in a single coherent frame of large scale mantle convection, initiated during the last ~40 Ma.

  3. Neogene crustal extension in Aegean, revisited

    SciTech Connect

    Stiros, S.C. )

    1988-08-01

    The Neogene evolution of the Aegean and adjacent areas has been described as the result of homogeneous, subduction-associated lithosphere stretching by a factor near two, interrupted or not by short regional compressional intervals. However, reconsideration of some of the existing data (structural, volcanological, heat flow) and new or unpublished information from Greece, southern Bulgaria, and Yugoslavia concerning different scales, structural (tectonics of lignite and other basins), morpholtectonic (describing bulges, differential coastal movements, rotations of blocks around vertical axes, etc.), some seismic lines offshore, and aeromagnetic data suggest the following. (1) The patterns of Neogene volcanism, heat flow, and vertical motions are inconsistent with the idea of homogeneous stretching. (2) There is no evidence of features that should have accommodated the postulated level of regional extension. (3) The evolution of most Neogene basins, compressional features, and bulges in normal faulting environments most likely does not reflect cycles of regional extension-compression but of transtension-transpression associated with Mesozoic and still active shear zones and deeper processes. These data suggest that for the Aegean the uniform extension model is unsatisfactory in both large and local scale; small amounts of probably secondary extension are likely; and processes other than subduction must be anticipated.

  4. Shear and extensional properties of kefiran.

    PubMed

    Piermaría, Judith; Bengoechea, Carlos; Abraham, Analía Graciela; Guerrero, Antonio

    2016-11-01

    Kefiran is a neutral polysaccharide constituted by glucose and galactose produced by Lactobacillus kefiranofaciens. It is included into kefir grains and has several health promoting properties. In the present work, shear and extensional properties of different kefiran aqueous dispersions (0.5, 1 and 2% wt.) were assessed and compared to other neutral gums commonly used in food, cosmetic and pharmaceutics industries (methylcellulose, locust bean gum and guar gum). Kefiran showed shear flow characteristics similar to that displayed by other representative neutral gums, although it always yielded lower viscosities at a given concentration. For each gum system it was possible to find a correlation between dynamic and steady shear properties by a master curve including both the apparent and complex viscosities. When studying extensional properties of selected gums at 2% wt. by means of a capillary break-up rheometer, kefiran solutions did not show important extensional properties, displaying a behaviour close the Newtonian. PMID:27516254

  5. Shear and extensional properties of kefiran.

    PubMed

    Piermaría, Judith; Bengoechea, Carlos; Abraham, Analía Graciela; Guerrero, Antonio

    2016-11-01

    Kefiran is a neutral polysaccharide constituted by glucose and galactose produced by Lactobacillus kefiranofaciens. It is included into kefir grains and has several health promoting properties. In the present work, shear and extensional properties of different kefiran aqueous dispersions (0.5, 1 and 2% wt.) were assessed and compared to other neutral gums commonly used in food, cosmetic and pharmaceutics industries (methylcellulose, locust bean gum and guar gum). Kefiran showed shear flow characteristics similar to that displayed by other representative neutral gums, although it always yielded lower viscosities at a given concentration. For each gum system it was possible to find a correlation between dynamic and steady shear properties by a master curve including both the apparent and complex viscosities. When studying extensional properties of selected gums at 2% wt. by means of a capillary break-up rheometer, kefiran solutions did not show important extensional properties, displaying a behaviour close the Newtonian.

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

    NASA Astrophysics Data System (ADS)

    Friederich, W.; Brüstle, A.; Küperkoch, L.; Meier, T.; Lamara, S.; Egelados Working Group

    2014-05-01

    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 in volcanic areas, where both

  7. The shape of the Aegean MCC's, Insights from 3D numerical modelling

    NASA Astrophysics Data System (ADS)

    Le Pourhiet, L.; Denèle, Y.; Huet, B.; Jolivet, L.

    2010-12-01

    The Aegean sea is a back arc basin in which the continental lithosphere has been stretched through the tertiary leaving several diachronous belts of Metamorphic Core Complexes (MCCs). The Aegean MCCs present two classes of shapes. Some are elongated in the direction of the lineation (A-type e.g. Naxos, Paros..) while the others are elongated in a direction normal to the lineation (B-type e.g. Tinos, Evvia ...). While it is well established from 1 and 2D modeling that MCC's forms when the lower crust is weak, the reason for the diversity of shape remains an open question. The A-type domes are not only elongated in shape; their P-T-t paths indicate a clear phase of warming during the exhumation and they also present migmatites (which are not observed in the other islands). Several hypothesis may be drawn. The elongated domes could result from 1) the competition of boudinage versus normal constriction folding, 2) lateral variation of the thickness or the temperature of the crust resulting in local buoyant instability (R-T instability) or 3) lateral gradient of deformation. This contribution presents the preliminary results obtained with thermo-mechanical models in which we test the influence of a local plutonic intrusions, along strike variation of extensional rate, and lateral boundary condition (normal shortening or extension) on the shape of the domes. As this problem is inherently three dimensional, the models were computed on our computer cluster using Gale/Underworld an ALE method with visco-plastic temperature dependent rheologies.

  8. PREFACE: Donald D Harrington Symposium on the Geology of the Aegean

    NASA Astrophysics Data System (ADS)

    Catlos, Elizabeth J.

    2008-03-01

    This volume of the IOP Conference Series: Earth and Environmental Sciences presents a selection of papers given at the Donald D Harrington Symposium on the Geology of the Aegean held on the campus of the University of Texas at Austin on April 28-30, 2008. Donald D Harrington was born in Illinois in 1899 and moved westward after serving in the Army Air Corps during World War I. Mr Harrington took a position as a landman with Marlin Oil Company in Oklahoma. When the Texas Panhandle oil boom hit in 1926, he moved to Amarillo, Texas, where he met Sybil Buckingham—the granddaughter of one of Amarillo's founding families. They married in 1935 and went on to build one of the most successful independent oil and gas operations in Texas history. The couple created the Don and Sybil Harrington Foundation in 1951 to support worthy causes such as museums, medical research, education, and the arts. At the Harrington Symposium on the Geology of the Aegean, researchers presented papers organized under five general themes: (1) the geology of Aegean in general (2) the geologic history of specific domains within the Aegean (Cyclades, Menderes, Kazdag, Rhodope, Crete, southern Balkans, etc) (3) the dynamic tectonic processes that occur within the Aegean (4) its geo-archeological history, natural history and hazards and (5) comparisons of the Aegean to regions elsewhere (e.g., Basin and Ranges; Asian extensional terranes). The Aegean is a locus of dynamic research in a variety of fields, and the symposium provided an opportunity for geologists from a range of disciplines to interact and share new results and information about their research in the area. At the opening reception in the Harry S Ransom Center, Dr Clark Burchfiel (Massachusetts Institute of Technology, USA) provided a keynote address on the outstanding geologic problems of the Aegean region. His paper in this volume outlines a framework for future studies. We also call attention to a paper in this volume by Dr Y

  9. Mechanisms for folding of high-grade rocks in extensional tectonic settings

    NASA Astrophysics Data System (ADS)

    Harris, Lyal B.; Koyi, Hemin A.; Fossen, Haakon

    2002-11-01

    This review of structures developed in extensional high-grade terrains, combined with results of centrifuge analogue modelling, illustrates the range of fold styles and mechanisms for folding of amphibolite to granulite facies rocks during rifting or the collapse of a thrust-thickened orogen. Several extensional fold mechanisms (such as folding within detachment shear zones) are similar to those in contractional settings. The metamorphic P- T- t path, and not fold style or mode of formation, is therefore required to determine the tectonic setting in which some folds developed. Other mechanisms such as rollover above and folding between listric normal shear zones, and folding due to isostatic adjustments during crustal thinning, are unique to extensional tectonic settings. Several mechanisms for folding during crustal extension produce structures that could easily be misinterpreted as implying regional contraction and hence lead to errors in their tectonic interpretation. It is shown that isoclinal recumbent folds refolded by open, upright folds may develop during regional extension in the deep crust. Folds with a thrust sense of asymmetry can develop due to high shear strains within an extensional detachment, or from enhanced back-rotation of layers between normal shear zones. During back-rotation folding, layers rotated into the shortening field undergo further buckle folding, and all may rotate towards orthogonality to the maximum shortening direction. This mechanism explains the presence of many transposed folds, folds with axial planar pegmatites and folds with opposite vergence in extensional terrains. Examples of folds in high-grade rocks interpreted as forming during regional extension included in this paper are from the Grenville Province of Canada, Norwegian Caledonides, Albany Mobile Belt and Leeuwin Complex of Western Australia, Ruby Mountains in the Basin and Range Province of Nevada, the Atâ Sund area of Greenland, the Napier Complex of Enderby Land

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

    NASA Astrophysics Data System (ADS)

    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.

    2015-06-01

    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.

  11. Monitoring sea level fluctuation in South Aegean

    NASA Astrophysics Data System (ADS)

    Zacharis, Vangelis; Paradissis, Demitris; Drakatos, George; Marinou, Aggeliki; Melis, Nicolaos; Anastasiou, Demitris; Alatza, Stavroula; Papanikolaou, Xanthos

    2015-04-01

    The complexity of the geological setting of the South Aegean is well-known, among the scientific community. The subduction zone coupled with the latest unrest of the Santorini volcano, as well as the particular morphology of the earth's surface and seabed pose a poorly understood source of tsunami hazard. A sparse network of tide gauges that operate in the area for varying periods of time is strengthened by the establishment of new sensors at carefully selected locations, by the Institute of Geodynamics of the National Observatory of Athens, and the Dionyssos Satellite Observatory and the Laboratory of Higher Geodesy of the National Technical University of Athens. These new instruments, aided by a rather dense network of GNSS receivers, provide a more concrete basis for the development, testing and evaluation of a near real-time model of the sea level changes in the area. Moreover, integration with various other sensors allows to understand and assess the level of tsunami risk in the area.

  12. South Aegean Geodynamic And Tsunami Monitoring Platform

    NASA Astrophysics Data System (ADS)

    Paradissis, Demitris; Drakatos, George; Marinou, Aggeliki; Anastasiou, Demitris; Alatza, Stauroula; Zacharis, Vangelis; Papanikolaou, Xanthos; Melis, Nicolaos; Kalogeras, Ioannis; Chouliaras, Gerasimos; Evangelidis, Christos; Makropoulos, Konstantinos

    2015-04-01

    The Aegean Sea is one of the most tectonically and seismically active areas in the world, thus constituting a Natural Laboratory. For the first time, a permanent multiparametric platform of networks that combine different (both terrestrial and space oriented) techniques, is established, in order to monitor the tectonic and volcanic activity in the area and produce an on-line database available both to the scientific community and the public. This platform includes continuous GNSS networks, tide-gauge sensors, accelerometers and seismographs. All the available existing infrastructure has been upgraded, enlarged and modernized resulting in a collaborative operation. New instrumentation has been installed in carefully selected sites. All the available data are analysed using state of the art processing software. Raw data and products will be available through a project dedicated portal. The multiparametric data and results gathered will be integrated and combined with the existing archive owned by the participating institutes to produce a thoroughgoing view of the underlying geophysical processes. The island of Santorini will serve as a focused study case for the project, due to the special tectono-volcanic interest and because of the already existing dense multiparametric network. Our goal is to provide permanent infrastructure and knowledge both to enlighten ambiguous scientific hypothesis and serve as a focal point for further scientific research.

  13. Nestedness in centipede (Chilopoda) assemblages on continental islands (Aegean, Greece)

    NASA Astrophysics Data System (ADS)

    Simaiakis, Stylianos Michail; Martínez-Morales, Miguel Angel

    2010-05-01

    In natural ecosystems, species assemblages among isolated ecological communities such as continental islands often show a nested pattern in which biotas of sites with low species richness are non-random subsets of biotas of richer sites. The distribution of centipede (Chilopoda) species in the central and south Aegean archipelago was tested for nestedness. To achieve this aim we used distribution data for 53 species collected on 24 continental Aegean islands (Kyklades and Dodekanisa). Based on the first-order jackknife estimator, most of islands were comprehensively surveyed. In order to quantify nestedness, we used the nestedness temperature calculator (NTC) as well as the nestedness metric based on overlap and decreasing Fill (NODF). NTC indicated that data exhibited a high degree of nestedness in the central and south Aegean island complexes. As far as the Kyklades and Dodekanisa are concerned, NTC showed less nested centipede structures than the 24 islands. Likewise, NODF revealed a significant degree of nestedness in central and south Aegean islands. It also showed that biotas matrices without singletons were more nested than the complete ones (Aegean, Kyklades and Dodekanisa). The two commonest centipede taxa (lithobiomorphs and geophilomorphs) contributed differently to centipede assemblages. In the Kyklades and Dodekanisa, geophilomorphs did not show a reliable nested arrangement unlike lithobiomorphs. In relation to the entire data set, nestedness was positively associated with the degree of isolation. In the Kyklades altitudinal range best explained nestedness patterns, while in Dodekanisa habitat heterogeneity proved to be more important for the centipede communities. Island area does not seem to be a significant explanatory variable. Some of our results from the Kyklades were critically compared with those for terrestrial isopod and land snail nested assemblages from the same geographical area. The complex geological and palaeogeographical history of

  14. Flow between eccentric cylinders: a shear-extensional controllable flow

    NASA Astrophysics Data System (ADS)

    Tian, Guoqiang; Wang, Mengmeng; Wang, Xiaolin; Jin, Gang

    2016-05-01

    In this work the non-Newtonian fluid between eccentric cylinders is simulated with finite element method. The flow in the annular gap between the eccentric rotating cylinders was found to be a shear-extensional controllable flow. The influence of rotating speed, eccentricity as well as the radius ratio on the extensional flow in the vicinity of the minimum gap between the inner and outer cylinder was quantitatively investigated. It was found that both the strengths of shear flow and extensional flow could be adjusted by changing the rotating speed. In respect to extensional flow, it was also observed that the eccentricity and radius ratio exert significant influences on the ratio of extensional flow. And it should be noted that the ratio of extensional flow in the mix flow could be increased when increasing the eccentricity and the ratio of shear flow in the mix flow could be increased when increasing the radius ratio.

  15. Asymmetric Vesicle Instability in Extensional Flow

    NASA Astrophysics Data System (ADS)

    Spann, Andrew; Zhao, Hong; Shaqfeh, Eric

    2012-11-01

    Previous researchers have chronicled the breakup of drops in an extensional flow as they stretch into a dumbbell shape with a long thin neck. Motivated by recent experimental observations, we study an apparently similar problem with vesicles, which are deformable but incompressible membranes that conserve area and volume. First, we simulate vesicles in an unbounded uniaxial extensional flow which are given general radial perturbations from an initially stable symmetric equilibrium state. For sufficiently low reduced volume (< 0.74 at matched inner/outer viscosity) there exists a capillary number at which an asymmetric perturbation mode will grow, resulting in the formation of an asymmetric dumbbell shape with a thin connecting cylindrical bridge analogous to the shapes associated with drop breakup. Our simulations help elucidate a mechanism for this instability based on a competition between internal pressure differentials in the vesicle resulting from the membrane bending force and ambient flow. We compare and contrast this transition to the ``standard'' drop breakup transition. Funded by NSF GRFP and Stanford Graduate Fellowship.

  16. Extensional duplex in the Purcell Mountains of southeastern British Columbia

    SciTech Connect

    Root, K.G. )

    1990-05-01

    An extensional duplex consisting of fault-bounded blocks (horses) located between how-angle normal faults is exposed in Proterozoic strata in the Purcell Mountains of British Columbia, Canada. This is one of the first documented extensional duplexes, and it is geometrically and kinematically analogous to duplexes developed in contractional and strike-slip fault systems. The duplex formed within an extensional fault with a ramp and flat geometry when horses were sliced from the ramp and transported within the fault system.

  17. Magnetotelluric Investigation of the South Aegean Volcanic Arc, Greece

    NASA Astrophysics Data System (ADS)

    Kalisperi, Despina; Romano, Gerardo; Smirnov, Maxim; Kouli, Maria; Perrone, Angela; Makris, John P.; Vallianatos, Filippos

    2014-05-01

    The South Aegean Volcanic Arc (SAVA) is a chain of volcanic islands in the South Aegean resulting from the subduction of the African tectonic plate beneath the Eurasian plate. It extends from Methana, northwest, to the Island of Nisyros southeast (450 km total length). SAVA comprises a series of dormant and historically active volcanoes, with the most prominent to be Aegina, Methana, Milos, Santorini, Kolumbo, Kos and Nisyros. The aim of the ongoing research project "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)" is to contribute to the investigation of the geoelectric structure of Southern Aegean, and particularly to attempt to image the Hellenic Subduction Zone. In this context, onshore magnetotelluric (MT) measurements were recently carried out on the central and eastern part of SAVA (Milos, Santorini, Nisyros and Kos Islands). Data were collected using two MT systems running simultaneously plus a remote reference station installed in Omalos plateau (Western Crete). Robust MT data analysis of the broad-band MT soundings and the resulting model of the conductivity structure of the South Aegean Volcanic Arc is presented. The research is co-funded by the European Social Fund (ESF) and National Resources under the Operational Programme 'Education and Lifelong Learning (EdLL) within the context of the Action 'Supporting Postdoctoral Researchers' in the framework of the project title "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)".

  18. Extensional tectonics on continents and the transport of heat and matter

    NASA Technical Reports Server (NTRS)

    Neugebauer, H. J.

    1985-01-01

    Intracontinental zones of extensional tectonic style are commonly of finite width and length. Associated sedimentary troughs are fault-controlled. The evolution of those structures is accompanied by volcanic activity of variable intensity. The characteristic surface structures are usually underlaid by a lower crust of the transitional type while deeper subcustal areas show delayed travel times of seismic waves especially at young tectonic provinces. A correspondence between deep-seated processes and zones of continental extension appears obvious. A sequential order of mechanisms and their importance are discussed in the light of modern data compilations and quantitative kinematic and dynamic approaches. The Cenozoic exensional tectonics related with the Rhine River are discussed.

  19. Sedimentation in detachment-dominated extensional orogens: Examples from the Mojave extensional belt, California

    SciTech Connect

    Travis, C.J.; Dokka, R.K. )

    1990-06-01

    Recent studies of syntectonic sedimentary rocks of the early Miocene Mojave Extensional Belt (MEB) provide new data on sediment dispersal within an evolving continental extensional orogen. Sediment dispersal within the MEB apparently reflects the evolution of the major tectonic elements of the belt. Sediments deposited in the breakaway zone of the Daggett terrane in the Newberry Mountains were derived from unextended regions to the southwest and from intraterrane tilted fault blocks to the northeast. Sediment dispersal patterns near transfer zones are typically perpendicular to extensional axes. In the Daggett terrane, coarse clastic materials were transported northwestward from unextended areas across the Kane Springs transfer fault into upper plate fault-bounded basins. Sequences accumulated in the hanging walls of upper plate tilted fault blocks exhibit geometries similar to those of breakaway zones, but show differences in thickness and textural attributes. Intraterrane arching is indicated by dispersal patterns in conglomerates of the central Cady Mountains in the Daggett terrane. Locally, detachment faulting may be succeeded by high-angle, normal faulting. In the Waterman terrane, this has resulted in relative uplift and the development of a metamorphic core complex in the Waterman Hills-Mitchell Range area. The uplift and unroofing history of the Waterman Hills is recorded in the thick deposits of the formation of Ross Canyon and the Barstow Formation of the Mud Hills.

  20. a Structural and Thermochronological Study of Santorini Detachment in Santorini Island, Aegean Sea

    NASA Astrophysics Data System (ADS)

    Marsellos, A.; Foster, D. A.; Min, K. K.; Kamenov, G. D.; Kidd, W. S.; Garver, J. I.; Kyriakopoulos, K.

    2012-12-01

    Extension in the Aegean has been very prominent since early Miocene expressed by a series of detachments, opening of the Cretan basin, arc expansion and plutons, with a peak of extensional activity at 10-16 Ma across the south Aegean. In Santorini, which is the southernmost Cyclades island and closest to the forearc, intrusion of an unexposed pluton to a depth equivalent to modern sea level took place at about 9.5 Ma (Skarpelis et al., 1992). In this study, Zircon fission-track (ZFT) and apatite (U-Th)/He (AHe) data from the Athinios metamorphic rocks exposed in Santorini caldera distinguish an upper metamorphic cooling unit associated with Early-Middle Eocene exhumation (46.3 ± 2.8 Ma, ZFT; 49.34 ± 2.9 Ma, AHe) from a lower metamorphic unit of Middle-Late Miocene (10.9 ± 0.7 Ma, ZFT; 9.4 ± 0.3 Ma, AHe) exhumation ages. The upper unit shows mineral lineations that range from N-S to NE-SW trending while the lower unit shows lineations ranging from N-S to NW-SE trending. U-Pb (LA-MC-ICP-MS) zircon data from mica-schists in the lower Santorini metamorphic unit show a prominent Pan-African signature similar to the Phyllite-quartzite unit (PQU) rocks exposed along the forearc in Kythera, Peloponnese and western Crete. The NW-SE stretching lineations in the lower unit imply an arc-parallel extension. Similar arc-parallel extension took place between 10-13 in PQU rocks in the west Crete-Kythera-south Peloponnese area (Marsellos et al., 2010). The lower unit shows ductile structures affected by top to the S shearing while the upper unit by top to the N shearing. A 3D projection of the mineral lineation dip angles along N-S direction shows a C' shear band of top to the N shearing that has affected the entire structural stack. Early brittle structures, which appear to be re-oriented normal faults, and show top to the S displacement. Later normal faults show similar shear sense. A tectonic model that could explain the above structures shows that initial exhumation of the

  1. Major outputs of the recent multidisciplinary biogeochemical researches undertaken in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Lykousis, V.; Chronis, G.; Tselepides, A.; Price, N. B.; Theocharis, A.; Siokou-Frangou, I.; Van Wambeke, F.; Danovaro, R.; Stavrakakis, S.; Duineveld, G.; Georgopoulos, D.; Ignatiades, L.; Souvermezoglou, A.; Voutsinou-Taliadouri, F.

    2002-06-01

    The main outputs of a multidisciplinary and integrated studies are summarised. The results incorporate the latest biogeochemical researches, at basin scale, in the Aegean Sea (including thermohaline circulation studies, SPM dynamics, mass and energy fluxes, acknowledge biochemical processes in the euphotic and the benthic layer and benthic response to downward fluxes). The data were acquired within five (seasonal) research cruises, during 1997-1998. Data analysis and evaluation hence provided important new information on the functional processes of the Aegean ecosystem. In terms of water circulation, no new deep water formation in the Aegean Sea was observed, during 1997-1998, but rather intermediate water, due mainly to the mild winter conditions. All the biochemical parameters of the euphotic zone (nutrients, Particulate Organic Carbon (POC), chlorophyll- a, phytoplankton, primary and bacterial production), although high in the N. Aegean Sea reflect clearly the highly oligotrophic character of the Aegean Sea. In the N. Aegean, microbial food web was the main pathway of carbon, whereas in the S. Aegean, the food web could be classified as multivorous. An important Black Sea Water (BSW) signal was observed in the dissolved phase; this was especially pronounced in the Dissolved Organic Carbon (DOC), Mn and to a lesser degree to Cd, Cu and Ni concentrations. The downward material fluxes are higher in the N. Aegean, relative to the S. Aegean. Substantially higher values of near-bottom mass fluxes were measured in the deep basins of the N. Aegean, implying significant deep lateral fluxes of POM. The N. Aegean could be classified as a "continental margin" ecosystem, whilst the S. Aegean is a typical "oceanic margin" environment. There is a close relationship and, consequently, coupling between the near-bottom mass fluxes and the accumulation rates of organic matter (OM), with the near-bottom mineralisation, bioturbation, redox potential, oxygen consumption rates, the

  2. Extremely Shallow Extensional Faulting Near Geothermal Fields

    NASA Astrophysics Data System (ADS)

    Hudnut, K. W.; Wei, S.; Donnellan, A.; Fielding, E. J.; Graves, R. W.; Helmberger, D. V.; Liu, Z.; Parker, J. W.; Treiman, J. A.

    2013-12-01

    Surface faulting has been discovered in association with a shallow extensional M 4.9 earthquake, the source properties of which have also been studied by modeling of broadband seismic data and geodetic imagery. This M 4.9 and also a M 4.6 shallow normal event occurred late in the Brawley Swarm of August 2012, a dominantly strike-slip sequence with events up to M 5.5 (Hauksson et al., SRL 2013 and Wei et al., GRL 2013). The point source waveform inversions reveal normal mechanisms and centroid depths of ~2.5 km for both events, while the modeling of the geodetic data indicates a compatible depth of ~2.0 km. The M 4.9 event had unusually large (~40 cm) and sudden (~1.0 - 1.5 km/sec) slip, considering its extremely shallow depth. The earlier and larger strike-slip events during the Aug. 2012 swarm were on a left-lateral SW-NE oriented vertical planar cross-fault, whereas the M 4.6 and M 4.9 occurred on a SSW-NNE oriented, west-dipping plane. Airborne imagery obtained using Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) revealed a surface fault rupture that was subsequently confirmed and documented in the field in May 2013. A pre-existing but previously un-mapped fault sustained west-down surface slip of up to 18 × 2 cm along breaks extending ~3.5 km along a NNE orientation, and ruptured beneath and under a railroad track and pipeline (without breaking them). UAVSAR and seismological data were used jointly to image the source properties of the M 4.9 earthquake in detail. Typically, the uppermost few kms of right-lateral faults in the Salton Trough exhibit creep, especially after larger earthquakes, as in 1979 and 1987. On this basis, general models of stable sliding within the uppermost few kms have been developed. In this case, however, the joint inversion indicates that seismic energy was radiated by slip of up to 40 cm on a fault plane extending from the surface to a depth of only ~3 km, extending ~4 km along-strike, and dipping ~45° west, with west

  3. Magmatic Trigger for Extensional Collapse? Character and Significance of Pre-Extensional Volcanic Activity in the Whipple Mountains Region, Lower Colorado River Extensional Corridor

    NASA Astrophysics Data System (ADS)

    Fidler, M. K.; Gans, P. B.

    2014-12-01

    The character and timing of voluminous Miocene volcanic activity associated with regional crustal extension in the lower Colorado River Extensional Corridor (CREC) shed light on the interplay between tectonic and magmatic processes in the area. New 40Ar/39Ar ages from holocrystaline groundmass separates of mafic lava flows and phenocrystic plagioclase, biotite, hornblende, and sanidine from silicic extrusive rocks, combined with LA-ICPMS U-Pb ages of zircon from the more altered intermediate to silicic rocks provide important new constraints on the ages of pre-, syn-, and post-extensional volcanic sequences in the vicinity of the Whipple Mountains metamorphic core complex. Local eruptive activity began ~20.5 Ma and persisted for 1.5 million years prior to the inception of major extensional faulting and tilting at ~19 Ma, as recorded by upper plate tilt blocks. The pre-extensional sequences are homoclinal, steeply tilted, and disconformably overlie older arkosic sedimentary rocks. There is no compelling evidence for angular unconformities or growth faulting during this earliest pre-extensional volcanic activity. These early erupted units are dominantly mafic, forming ≥1 km thick sections of olivine-basalt and olv-cpx-plag basaltic andesite lava flows punctuated by rare aphyric to crystal poor dacite ignimbrites. Plag±pyx±bio±hbl dacite lava flows and domes with associated pyroclastic deposits appear late in the pre-extensional sequence, immediately prior to and during the onset of major extensional faulting. These crystal-poor to aphyric silicic rocks show abundant evidence of magma mingling and may represent hybridized partial melts generated by the influx of basaltic magma into the crust. The pre-extensional sequence is locally overlain by ~18.5 to 18.8 Ma syn- and post-extensional volcanic and sedimentary rocks along a pronounced 30-60° angular unconformity, indicating very rapid extension during the early stages of the CREC's development. This overall

  4. Extensional Rheology of Fire Ant Aggregates

    NASA Astrophysics Data System (ADS)

    Franklin, Scott; Kern, Matthew; Phonekeo, Sulisay; Hu, David

    We explore the extensional rheology and self-healing of fire ant (Solenopsis invicta) aggregations, mechanically entangled ensembles used to form rafts, bivouacs or bridges. Macroscopic experiments create quasi-two dimensional piles and measure the force required to impose a constant end-velocity. This force fluctuates, reminiscent of similar experiments on geometrically cohesive granular materials. Heterogeneous chains develop, with isolated ants often the sole link between top and bottom. Finally, the maximum pile strength scales sub-linearly with the number of ants, with the maximum force per ant decreasing as the pile grows. We reproduce these behaviors with a simple model that represents ants feet as discs connected by a spring (the ''leg''). Discs move randomly, and stick to one another when in contact. Discs in contact un-stick at random with a probability that decreases as the spring (leg) is stretched, modeling an ant's tendency to hold on longer when stretched. Simulations qualitatively reproduces the fluctuating force, chain formation and sublinear scaling of maximum force with particle number and give insight into underlying mechanisms that govern the ants' behaviors. Funded in part by NSF DMR #1133722.

  5. Grabens on Io: Evidence for Extensional Tectonics

    NASA Astrophysics Data System (ADS)

    Hoogenboom, T.; Schenk, P.

    2012-12-01

    Io may well be the most geologically active body in the solar system. A variety of volcanic features have been identified, including a few fissure eruptions, but tectonism is generally assumed to be limited to compression driven mountain formation (Schenk et al., 2001). A wide range of structural features can also be identified including scarps, lineaments, faults, and circular depressions (pits and patera rims). Narrow curvilinear graben (elongated, relatively depressed crustal unit or block that is bounded by faults on its sides) are also scattered across Io's volcanic plains. These features are dwarfed by the more prominent neighboring volcanoes and mountains, and have been largely ignored in the literature. Although they are likely to be extensional in origin, their relationship to local or global stress fields is unknown. We have mapped the locations, length and width of graben on Io using all available Voyager and Galileo images with a resolution better than 5 km. We compare the locations of graben with existing volcanic centers, paterae and mountain data to determine the degree of correlation between these geologic features and major topographic variations (basins/swells) in our global topographic map of Io (White et al., 2011). Graben are best observed in > 1-2 km low-sun angle images. Approximately 300 images were converted from ISIS to ArcMap format to allow easy comparison with the geological map of Io (Williams et al., 2012) along with previous higher resolution structural mapping of local areas (e.g. Crown et al., 1992). We have located >45 graben to date. Typically 1-3 kilometers across, some of these features can stretch for over 500 kilometers in length. Their formation may be related to global tidal stresses or local deformation. Io's orbit is eccentric and its solid surface experiences daily tides of up to ˜0.1 km, leading to repetitive surface strains of 10-4 or greater. These tides flex and stress the lithosphere and can cause it to fracture

  6. Shear zones developed between extensional and compressional tectonic regimes: recent deformation of the Burdur Fethiye Shear Zone as a case study

    NASA Astrophysics Data System (ADS)

    Elitez, İrem; Yaltırak, Cenk; Aktuǧ, Bahadır

    2016-04-01

    The southwestern Turkey is one of the most tectonically active areas of the eastern Mediterranean and therefore is a controversial region from the geodynamic point of view. This complex tectonic regime is dominated by the westward escape of Anatolia related to North Anatolian Fault, Aegean back-arc extension regime due to roll-back of Hellenic Arc, the subduction transform edge propagator (STEP) fault zone related to the motion of Hellenic and Cyprus arcs and compressional regime of Tauride Mountains. In addition to that, an active subduction and seamounts moving towards the north determine the tectonic frame of the Eastern Mediterranean. Many researchers suggest either the existence of a single left lateral fault or the nonexistence of a fault zone between Western Anatolia and Western Taurides. According to the integration of digital elevation data, non-commercial GoogleEarth satellite images and field studies, a 300 km-long 75-90 km-wide NE-SW-trending left lateral shear zone, the Burdur-Fethiye Shear Zone, is located among these tectonic structures. By using GPS velocities and focal mechanism solutions of earthquakes, it is understood that most of the previous studies turn a blind eye to the hundreds of faults related to a left-lateral shear zone which will have an important role in the Mediterrenean tectonics. The Burdur-Fethiye Shear Zone is like a zipper driven by the relative velocity differences due to the Aegean back-arc extensional system and Western Taurides compressional region and presents a high seismic activity. The GPS vectors reflect remarkable velocity differences on land and relatedly the significant topographic differences can be clearly observed. According to the GPS vectors, the Aegean region moves 4-12 mm/yr faster than the wesward escape of the Anatolia towards southwest and the velocities are low in the Western Taurides. The left-lateral differential motion across the Burdur-Fethiye Shear Zone varies from 3-4 mm/yr in the north side to 8

  7. Modeling of Tsunami Propagation and Inundation in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Aydin, B.; Moore, C. W.; Kalligeris, N.; Kanoglu, U.

    2011-12-01

    Several tsunami forecasting systems have been developed based on pre-computed tsunami scenario databases with the aim to provide early warning to tsunami-prone regions worldwide. NOAA's tsunami forecasting system for the United States is such a system, based on the concept of a pre-computed tsunami scenario database consisting of 100km x 50km fault planes with a slip value of 1m, referred to as tsunami source functions. These source functions are placed along the subduction zones in several rows, covering known faults throughout the major ocean basins. Linearity of the tsunami propagation in the open ocean allows scaling and/or combination of the pre-computed tsunami source functions since propagation of tsunamis in deep sea is linear. In real time, a specific tsunami scenario can be obtained by inverting deep-ocean buoy measurements providing initial and boundary conditions for site-specific, high-resolution, nonlinear forecast models. The database can also be used to generate different scenario events to produce tsunami inundation maps for target shorelines. To date, tsunami source functions have not been computed along the subduction zones in Aegean Sea even though there are considerable number of tsunami events causing damages. Although one might argue that the possibility of such an event is rare, the coastlines are densely populated, developed, and hosts millions of tourists during the summer months. Therefore, even though the risk of an event might be small, the hazard is high. Considering the long shorelines and the general lack of public knowledge about preparedness, a tsunami event in the region would be disastrous. A database for historical tsunami events in the Aegean Sea has been compiled, providing potential source locations. This data has allowed us to create a tsunami propagation database for Aegean Sea. Once finalized, this pre-computed scenario database will be extremely useful in developing tsunami resilient communities in the region.

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

    PubMed

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

    2002-06-01

    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

  9. The role of extensional viscosity in frog tongue projection

    NASA Astrophysics Data System (ADS)

    Noel, Alexis; Wagner, Caroline; McKinley, Gareth; Mendelson, Joe; Hu, David

    2014-11-01

    Frogs and other amphibians capture insects through high-speed tongue projection, some achieving tongue accelerations of over fifty times gravity. In this experimental study, we investigate how a frog's sticky saliva enables high-speed prey capture. At the Atlanta zoo, we used high-speed video to film the trajectory of frog tongues during prey capture. We have also designed and built a portable extensional rheometer; by following the capillary-driven thinning in the diameter of a thread of saliva we characterize the relaxation time and extensional viscosity and so infer the adhesive force between the frog tongue and prey.

  10. Kolumbo active seamount (Greece): A window into the Aegean mantle

    NASA Astrophysics Data System (ADS)

    Rizzo, A. L.; Caracausi, A.; Chavagnac, V.; Nomikou, P.; Polymenakou, P.; Magoulas, A.; Mandalakis, M.; Kotoulas, G.

    2015-12-01

    Submarine volcanism is ubiquitous in active tectonic settings of the earth, but due to depth and hazardousness of these environments the study is a challenge. In May 2014, we performed a cruise in the Aegean Sea aimed to investigate the high-temperature (>200°C) hydrothermal system of Kolumbo active underwater volcano, 7 km northeast off Santorini. Last explosive eruption occurred in 1650 A.D. and killed ~70 people, so plainly the eruptive potential is real. We sampled gases discharged from seven chimneys located at ~500 m b.s.l. and we investigated their composition. The chemistry indicates that these consist of almost pure CO2 with a small atmospheric contamination. The δ13C-CO2 varies from 0 to 1.5‰ and shows a positive correlation with the concentration of He, H2, CO and CH4 as the result of chemical and isotope fractionation due to variable extents of gas-water interaction. The 3He/4He varies from 7.0 to 7.1 Ra, coherently with the fact that this ratio does not suffer any fractionation due to gas-water interaction. These values are surprisingly higher (more than 3 units Ra) than the measurements performed in gases and rocks from Santorini (Rizzo et al., 2015). They are in the typical range of arc volcanoes worldwide (7-9 Ra; Hilton et al., 2002; Di Piazza et al., 2015), indicating that the 3He/4He ratios measured at Kolumbo are likely the result of direct mantle degassing in a general extensive regime. More importantly, these ratios are the highest in all the South Aegean volcanism, which leads to consider homogeneous (and MORB-like) the He isotope composition of the mantle below the central part of the Hellenic Volcanic Arc and eastward up to Nisyros, which until this study showed the highest ratios (6.2Ra; Shimizu et al., 2005). Our results strongly emphasize the role of tectonics in the transfer of fluids from the mantle toward the surface. The complicated geodynamics status of the Aegean-Anatolian region, plays a key role in generating crustal

  11. Assimilating Ferry Box data into the Aegean Sea model

    NASA Astrophysics Data System (ADS)

    Korres, G.; Ntoumas, M.; Potiris, M.; Petihakis, G.

    2014-12-01

    Operational monitoring and forecasting of marine environmental conditions is a necessary tool for the effective management and protection of the marine ecosystem. It requires the use of multi-variable real-time measurements combined with advanced physical and ecological numerical models. Towards this, a FerryBox system was originally installed and operated in the route Piraeus-Heraklion in 2003 for one year. Early 2012 the system was upgraded and moved to a new high-speed ferry traveling daily in the same route as before. This route is by large traversing the Cretan Sea being the largest and deepest basin (2500 m) in the south Aegean Sea. The HCMR Ferry Box is today the only one in the Mediterranean and thus it can be considered as a pilot case. The analysis of FerryBox SST and SSS in situ data revealed the presence of important regional and sub-basin scale physical phenomena, such as wind-driven coastal upwelling and the presence of a mesoscale cyclone to the north of Crete. In order to assess the impact of the FerryBox SST data in constraining the Aegean Sea hydrodynamic model which is part of the POSEIDON forecasting system, the in situ data were assimilated using an advanced multivariate assimilation scheme based on the Singular Evolutive Extended Kalman (SEEK) filter, a simplified square-root extended Kalman filter that operates with low-rank error covariance matrices as a way to reduce the computational burden. Thus during the period mid-August 2012-mid January 2013 in addition to the standard assimilating parameters, daily SST data along the ferryboat route from Piraeus to Heraklion were assimilated into the model. Inter-comparisons between the control run of the system (model run that uses only the standard data set of observations) and the experiment where the observational data set is augmented with the FerryBox SST data produce interesting results. Apart from the improvement of the SST error, the additional assimilation of daily of FerryBox SST

  12. Crustal structure of the Aegean area obtained by traveltime tomography

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Brüstle, A.; Küperkoch, L.; Friederich, W.

    2012-04-01

    The Hellenic arc and Aegean sea area are of locus of high seismicity and intense tectonic activity. Previous studies using either traveltimes of body waves or dispersion curves of surface waves show strong lateral heterogeneity of velocity structure of the crust and upper mantle under the Aegean area. Especially crustal thicknesses vary from about 20 km to 45 km. The complexity of crustal structure often requires the use of a number of one-dimensional layered models, in the calculation of synthetic seismograms for different ray traversing paths, to determine moment tensor of small-to-moderate earthquakes in this area. Using travel times from the EHB catalog data between 1980 and 1997 from International Seismological Center (Engdahl et al. 1998), Euro-Mediterranean Bulletin data between 1998 and 2008 from the Euro-Mediterranean Seismological Center (Godey et al. 2006), and additional local earthquakes recorded by the temporary stations deployed in the EGELADOS project, we derive a new three-dimensional velocity model of the crust in the Aegean area using the traveltime tomographic inversion code FMTOMO developed by Rawlinson et al. (2006). The events falling into the research area defined by 34°-40°N and 20°-29°E are firstly relocated using HypoDD (Waldhauser & Ellsworth 2000) before tomographic inversion is performed. Since the number of earthquakes is much greater than the number of stations, the source and receiver roles are interchanged to accelerate the forward calculation of traveltimes which is done by tracking the wavefront propagation with the fast marching method. The initial one-dimensional model was obtained by simultaneously inverting the data both for hypocenter locations and velocity using VELEST (Kissling et al. 1994). Checkboard resolution tests for the P waves show that anomalies of size of half a degree could be correctly recovered down to depth of 50 km. One notable feature from the preliminary inversion results for the P velocity is that the

  13. Factors That Influence the Extensional Rheological Property of Saliva.

    PubMed

    Vijay, Amrita; Inui, Taichi; Dodds, Michael; Proctor, Gordon; Carpenter, Guy

    2015-01-01

    The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste) salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva. PMID:26305698

  14. Factors That Influence the Extensional Rheological Property of Saliva

    PubMed Central

    Vijay, Amrita; Inui, Taichi; Dodds, Michael; Proctor, Gordon; Carpenter, Guy

    2015-01-01

    The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste) salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva. PMID:26305698

  15. Factors That Influence the Extensional Rheological Property of Saliva.

    PubMed

    Vijay, Amrita; Inui, Taichi; Dodds, Michael; Proctor, Gordon; Carpenter, Guy

    2015-01-01

    The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste) salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva.

  16. The extensional rheology of non-Newtonian materials

    NASA Technical Reports Server (NTRS)

    Spiegelberg, Stephen H.; Gaudet, Samuel; Mckinley, Gareth H.

    1994-01-01

    It has been proposed to measure the extensional viscosity function of a non-Newtonian polymer solution in a reduced gravity environment as part of the Advanced Fluid Module. In ground-based extensional measurements, the no-sip boundary condition at solid-fluid interfaces always result in appreciable shear gradients in the test fluid; however the removal of gravitational body forces permits controlled extensional deformation of containerless test samples and the first unambiguous measurements of this kind. Imperative to successful implementation of this experiment is the generation and subsequent deformation of a stable cylindrical column of test fluid. A study of the generation and deformation of liquid bridges demonstrates that Newtonian liquid bridges undergo capillary breakup as anticipated when stretched beyond a critical aspect ratio; non-Newtonian liquid bridges, however, are stabilized by the strain-hardening phenomenon exhibited by these materials. Numerical simulations of Newtonian breakup are compared with experimental results, and show that previous ground-based attempts at measuring the extensional viscosity of Newtonian fluids are of limited accuracy.

  17. 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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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

  18. Segmented Hellenic slab rollback driving Aegean deformation and seismicity

    NASA Astrophysics Data System (ADS)

    Sachpazi, M.; Laigle, M.; Charalampakis, M.; Diaz, J.; Kissling, E.; Gesret, A.; Becel, A.; Flueh, E.; Miles, P.; Hirn, A.

    2016-01-01

    The NE dipping slab of the Hellenic subduction is imaged in unprecedented detail using teleseismic receiver function analysis on a dense 2-D seismic array. Mapping of slab geometry for over 300 km along strike and down to 100 km depth reveals a segmentation into dipping panels by along-dip faults. Resolved intermediate-depth seismicity commonly attributed to dehydration embrittlement is shown to be clustered along these faults. Large earthquakes occurrence within the upper and lower plate and at the interplate megathrust boundary show a striking correlation with the slab faults suggesting high mechanical coupling between the two plates. Our results imply that the general slab rollback occurs here in a differential piecewise manner imposing its specific stress and deformation pattern onto the overriding Aegean plate.

  19. Sustainable use of water in the Aegean Islands.

    PubMed

    Gikas, Petros; Tchobanoglous, George

    2009-06-01

    Water demands in the Aegean Islands have increased steadily over the last decade as a result of a building boom for new homes, hotels, and resorts. The increase in water demand has resulted in the disruption of past sustainable water management practices. At present, most freshwater needs are met through the use of the limited groundwater, desalinated seawater, and freshwater importation. Wastewater reclamation, not used extensively, can serve as an alternative source of water, for a variety of applications now served with desalinated and imported water. Three alternative processes: desalination, importation, and water reclamation are compared with respect to cost, energy requirements and long-term sustainability. Based on the comparisons made, water reclamation and reuse should be components of any long-term water resources management strategy.

  20. An integrated approach to teaching Aegean archaeology and archaeological science

    NASA Astrophysics Data System (ADS)

    Pitcairn, Erica Glenn

    Outlined here is a course that would serve as an introduction to archaeological science, specifically within the context of Aegean Prehistory. The main objective of this course is to expose students early in their archaeological careers to a variety of methods and questions, and to depart from the culture-historical perspective that typifies introductory survey courses. The class structure is equal parts lecture and discussion, moving between learning how the methods work and evaluating case studies. All graded assignments build on one another, guiding the students through designing their own research project. The ultimate goals of the assignments are to build key writing and professional skills, develop a basic understanding of research design, and to instill confidence that the student can contribute to the production of knowledge, whatever field he or she decides to pursue.

  1. Earthquakes increase hydrothermal venting and nutrient inputs into the Aegean

    NASA Astrophysics Data System (ADS)

    Dando, P. R.; Hughes, J. A.; Leahy, Y.; Taylor, L. J.; Zivanovic, S.

    1995-05-01

    Areas of submarine gas and water venting around the island of Milos, in the Hellenic volcanic island arc, were mapped. Water samples were collected from five stations in the geothermally active Paleohori Bay on 15 March 1992. Seismic events, of M s 5.0 and 4.4, occurred south of the Bay on 20 March and the sampling was repeated after these. Phosphate and manganese in the water column increased by 360% after the seismic activity. Analysis of water samples collected from gas and water seeps and of interstitial water from sediment cores showed that the hot sediment in the Bay was enriched in phosphate, to a mean concentration of 65 μmol l -1 in the interstitial water. The number of geothermally active areas in the Aegean, together with the extent of venting and the frequency of earthquakes suggests that the hydrothermal areas may be an important source of phosphate in this oligotrophic Sea.

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

    PubMed Central

    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; 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.; Thomas, Mark G.; Papageorgopoulou, Christina; Burger, Joachim

    2016-01-01

    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

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

    PubMed

    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

    2016-06-21

    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

  4. Anisakidae infection in fish of the Aegean Sea.

    PubMed

    Chaligiannis, Ilias; Lalle, Marco; Pozio, Edoardo; Sotiraki, Smaragda

    2012-03-23

    Nematode worms of the family Anisakidae are the causative agents of infections in humans when fish is consumed raw and of serious allergies up to the death, when fish is consumed raw or cooked by previously sensitized people. From April until November 2009, 462 fish belonging to 26 species, fished in three areas of the Aegean Sea were tested for Anisakidae larvae. Anisakidae larvae were detected in 87 (18.83%) fish of 13 species. These larvae were identified by morphology as the third-stage larvae of the genera Hysterothylacium sp. or Anisakis. Larvae of the genus Anisakis were identified by PCR-RFLP as belonging to A. simplex s.str., A. pegreffii, or as hybrids between A. simplex s.str and A. pegreffii. PMID:22030376

  5. Sustainable use of water in the Aegean Islands.

    PubMed

    Gikas, Petros; Tchobanoglous, George

    2009-06-01

    Water demands in the Aegean Islands have increased steadily over the last decade as a result of a building boom for new homes, hotels, and resorts. The increase in water demand has resulted in the disruption of past sustainable water management practices. At present, most freshwater needs are met through the use of the limited groundwater, desalinated seawater, and freshwater importation. Wastewater reclamation, not used extensively, can serve as an alternative source of water, for a variety of applications now served with desalinated and imported water. Three alternative processes: desalination, importation, and water reclamation are compared with respect to cost, energy requirements and long-term sustainability. Based on the comparisons made, water reclamation and reuse should be components of any long-term water resources management strategy. PMID:19243876

  6. Source mechanism of the 2014 Aegean Sea earthquake

    NASA Astrophysics Data System (ADS)

    Nakano, Masaru

    2016-04-01

    Rapid determination of centroid moment tensor (CMT) of earthquakes, namely the source centroid location, focal mechanism, and magnitude is important for early disaster responses and issuing Tsunami warnings. In order to evaluate capability of Turkey seismic network for rapid determinations of CMT, I investigate the source mechanism of the 2014 Aegean Sea earthquake (Mw 6.9). Although this event occur out of Turkey seismic network, I obtained stable CMT solution. The CMT solution of this earthquake represents a strike-slip fault, consistent with the geometry of the North Anatolian Fault (NAF), and the source-time function indicates that this event comprised several distinct subevents. Each subevent is considered to have ruptured a different fault segment. This observation indicates the existence of a mechanical barrier, namely a NAF segment boundary, at the hypocenter. I also determined CMT solutions of background seismicity. CMT solutions of background seismicity beneath the Aegean Sea represent strike-slip or normal faulting along the NAF or its branch faults. The tensional axes of these events are oriented northeast-southwest, indicating a transtensional tectonic regime. Beneath the Sea of Marmara, the CMT solutions represent mostly strike-slip faulting, consistent with the motion of the NAF, but we identified a normal fault event with a tensional axis parallel to the strike of the NAF. This mechanism indicates that a pull-apart basin, marking a segment boundary of the NAF, is developing there. Because ruptures of a fault system and large earthquake magnitudes are strongly controlled by the fault system geometry and fault length, mapping fault segments along NAF can help to improve the accuracy of scenarios developed for future disastrous earthquakes in the Marmara region.

  7. The trace-element characteristics of Aegean and Aeolian volcanic arc marine tephra

    NASA Astrophysics Data System (ADS)

    Clift, Peter; Blusztajn, Jerzy

    1999-10-01

    High-silica volcanic ashes are found within deep-sea sediments throughout the Eastern Mediterranean. Although coring by Ocean Drilling Program has penetrated Lower Pliocene (˜4 Ma) sediments, few ashes older than 400 k.y. have been recovered, suggesting a young initiation to subaerial Aegean Arc volcanism. Ashes derived from the Aegean volcanic front were cored south and east of the arc, and are typified by medium-K, calc-alkaline major-element compositions, contrasting with high-K ashes from the Aeolian Arc found in the Ionian Sea and as far east as Crete. Ion microprobe analysis of individual glass shards shows that all the ashes have a light rare earth element (LREE)-enriched pattern after normalizing against a chondrite standard. Aeolian Arc-derived ashes show greater enrichment than those from the Aegean area. Within the latter set, two groups are discernible, a mildly enriched set similar to the volcanoes of the arc volcanic front, and a more enriched group corresponding to lavas from the backarc region or possible from western Anatolia. Multi-element `spider diagrams' also show a bimodal division of enriched and depleted Aegean ashes, possibly caused by source depletion due to melt extraction in the Aegean backarc followed by remelting under the volcanic front. Relative Nb depletion, a characteristic of arc volcanism, is seen to be modest in Aegean and non-existent in Aeolian ashes. Using B/Be as a proxy for the flux of material from the subducting slab, this influence is seen to be low in the Aeolian Arc but higher than at Vesuvius. B/Be is higher again in the Aegean Arc. These differences may reflect the rate of subduction in each system. Data suggest caution is required when correlating ashes solely on the basis of major elements, as alkaline ashes from the central part of the study may be derived from Italy or from the Aegean backarc.

  8. Relationships between subduction and extension in the Aegean region: evidence from granite plutons of the Biga Peninsula, NW Turkey

    NASA Astrophysics Data System (ADS)

    Black, K. N.; Catlos, E. J.; Oyman, T.; Demirbilek, M.

    2012-04-01

    The Biga Peninsula is a tectonically complex region in western Turkey characterized by Tethyan sutures overprinted by extensional grabens, active fault strands of the North Anatolian Shear Zone, and numerous granitoid plutons. Two end-member models for the initiation of extension in the Biga region have been proposed, both of which focus on the role of igneous assemblages. The first model involves the emplacement of a hot mantle plume that thins and weakens crust and isostatic doming drives extension. The second has regional tensional stresses as the driving force, and magmatism is a consequence of decompression. Here we focus on understanding the timing and geochemical evolution of three granitoid plutons located in and just south of the Biga Peninsula to understand which end-member model could be applicable to the Aegean region. The Kestanbolu pluton is located north of the proposed Vardar Suture Zone, whereas the Eybek and Kozak plutons are north of the Izmir-Ankara Suture Zone. These sutures may mark regions of the closure of branches of the NeoTethyan Ocean. To better understand their sources and tectonic evolution, we acquired geochemical and geochronological data, and cathodoluminescence (CL) images of the rocks. Previously reported ages of the plutons range from Late Eocene to Middle Miocene. Here we acquired in situ (in thin section) ion microprobe U-Pb ages of zircon grains found in a range of textural relationships. Ages from the Kozak pluton range from 37.8±5.4 Ma to 10.3±2.4 Ma (238U/206Pb, ±1σ) with two ages from a single grain of 287±26 Ma and 257±18 Ma. We also found Oligocene to Late Miocene zircon grains in the Kestanbolu pluton, whereas zircons from the Eybek pluton range from 34.3±4.8 Ma to 21.2±1.7 Ma. Samples collected from the Kozak and Eybek plutons are magnesian, calc-alkalic, and metaluminous, whereas the Kestanbolu rocks are magnesian, alkali-calcic, and metaluminous with one ferroan sample and one peraluminous sample. Trace

  9. Strain Localization Within a Syn-Tectonic Pluton in a Back-Arc Extensional Context: the Naxos granodiorite (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Bessiere, Eloïse; Rabillard, Aurélien; Arbaret, Laurent; Jolivet, Laurent; Augier, Romain; Menant, Armel

    2016-04-01

    Naxos Island is part of the central Cyclades (Aegean Sea, Greece) where a series of migmatite-cored metamorphic domes were exhumed below large-scale detachment systems during a Cenozoic back-arc extension. On Naxos, the Miocene exhumation history of the high-temperature metamorphic dome was notably achieved through two anastomosing and closely spaced top-to-the-north detachments belonging to the Naxos-Paros detachment system. According to previous contributions, the late exhumation stages were accompanied by the emplacement of a syn-kinematic I-type granodiorite that intruded a ductile-then-brittle detachment. Later the detachment migrated at the interface between the pluton and the metamorphic unit under ductile-to-brittle conditions. To clarify how extensional deformation was precisely distributed within the pluton, a multi-scale approach from field observations to laboratory investigations was undertaken. Through macro- to micro-structural observations, we show a continuous deformation history from magmatic to solid-state ductile/brittle conditions under an overall north-directed shearing deformation. The early magmatic or sub-solidus deformation is evidenced in a large part of the granodiorite, notably in its southern part where the original intrusive contact is still preserved. Solid-state deformation is recorded further north when approaching the detachment zone, highlighted by a thicker cataclastic zone and numerous pseudotachylite veins. From these field observations, we defined six strain facies, leading us to propose a qualitative strain map of the Naxos granodiorite. Based on field pictures and X-ray tomography of oriented samples collected along the strain gradient, we quantified the intensity of mineralogical fabrics in 2D and 3D. This step required the treatment of 600 rocks samples and pictures using SPO2003 (Shape Preferred Orientation) and Intercepts2003. Measured shape variations of the strain ellipsoid thus corroborate the large-scale strain

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

    PubMed

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

    2015-02-15

    High-resolution measurements of gas and aerosols' chemical composition along with meteorological and turbulence parameters were performed over the Aegean Sea (AS) during an Etesian outbreak in the framework of the Aegean-GAME airborne campaign. This study focuses on two distinct Etesian patterns, with similarities inside the Marine Atmospheric Boundary Layer (MABL) and differences at higher levels. Under long-range transport and subsidence the pollution load is enhanced (by 17% for CO, 11% for O3, 28% for sulfate, 62% for organic mass, 47% for elemental carbon), compared to the pattern with a weaker synoptic system. Sea surface temperature (SST) was a critical parameter for the MABL structure, turbulent fluxes and pollutants' distribution at lower levels. The MABL height was below 500 m asl over the eastern AS (favoring higher accumulation), and deeper over the western AS. The most abundant components of total PM1 were sulfate (40-50%) and organics (30-45%). Higher average concentrations measured over the eastern AS (131 ± 76 ppbv for CO, 62.5 ± 4.1 ppbv for O3, 5.0 ± 1.1 μg m(-3) for sulfate, 4.7 ± 0.9 μg m(-3) for organic mass and 0.5 ± 0.2 μg m(-3) for elemental carbon). Under the weaker synoptic system, cleaner but more acidic air masses prevailed over the eastern part, while distinct aerosol layers of different signature were observed over the western part. The Aitken and accumulation modes contributed equally during the long-range transport, while the Aitken modes dominated during local or medium range transport. PMID:25460953

  11. Single Polymer Dynamics under Large Amplitude Oscillatory Extensional (LAOE) Flow

    NASA Astrophysics Data System (ADS)

    Zhou, Yuecheng; Schroeder, Charles M.

    Over the past two decades, advances in fluorescence imaging and particle manipulation have enabled the direct observation of single polymer dynamics in model flows such as shear flow and planar extensional flow. The vast majority of single polymer studies, however, has focused on chain dynamics using simple transient step forcing functions. In order to study single polymer dynamics in non-idealized model flows, there is a clear need to implement more complicated transient flow forcing functions. In bulk rheology, large amplitude oscillatory shear (LAOS) was widely used to study the linear and nonlinear viscoelasticity of materials, but not yet been applied to molecular rheology. In this work, we directly probe single polymer dynamics using oscillatory extensional flow in precisely controlled microfluidic devices. We are able to generate large and small amplitude sinusoidal oscillatory extensional flow in a cross-slot microfluidic device while imaging the conformational dynamics of a single polymer trapped at the stagnation point. In this flow, polymer chains are stretched, squeezed, and rotated between extensional/compressional axes in a highly dynamic and transient manner. Using this technique, we studied the dynamics and coil-stretch transition of a single λ-DNA as a function of the Weissenberg number (Wi) and Deborah number (De). Moreover, we use Brownian dynamics simulation to map a wide range of Pipkin space for polymers from linear steady-state conditions to non-linear unsteady-states. Our results reveal a critical Wi at the coil-stretch transition that is function of the De in LAOE flow. Department of Materials Science and Engineering.

  12. Subglacial extensional fracture development and implications for Alpine Valley evolution

    NASA Astrophysics Data System (ADS)

    Leith, Kerry; Moore, Jeffrey R.; Amann, Florian; Loew, Simon

    2014-01-01

    stresses induced through exhumation and tectonic processes play a key role in the topographic evolution of alpine valleys. Using a finite difference model combining the effects of tectonics, erosion, and long-term bedrock strength, we assess the development of near-surface in situ stresses and predict bedrock behavior in response to glacial erosion in an Alpine Valley (the Matter Valley, southern Switzerland). Initial stresses are derived from the regional tectonic history, which is characterized by ongoing transtensional or extensional strain throughout exhumation of the brittle crust. We find that bedrock stresses beneath glacial ice in an initial V-shaped topography are sufficient to induce localized extensional fracturing in a zone extending laterally 600 m from the valley axis. The limit of this zone is reflected in the landscape today by a valley "shoulder," separating linear upper mountain slopes from the deep U-shaped inner valley. We propose that this extensional fracture development enhanced glacial quarrying between the valley shoulder and axis and identify a positive feedback where enhanced quarrying promoted valley incision, which in turn increased in situ stress concentrations near the valley floor, assisting erosion and further driving rapid U-shaped valley development. During interglacial periods, these stresses were relieved through brittle strain or topographic modification, and without significant erosion to reach more highly stressed bedrock, subsequent glaciation caused a reduction in differential stress and suppressed extensional fracturing. A combination of stress relief during interglacial periods, and increased ice accumulation rates in highly incised valleys, will reduce the likelihood of repeat enhanced erosion events.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  14. Upper Cenozoic organic-rich sequences (offshore and onshore the south Aegean sea)

    SciTech Connect

    Anastasakis, G.

    1988-08-01

    The upper Cenozoic sedimentary column of the south Aegean Sea is composed mostly of marine sediments which have been deposited after the Seravallian breakup of the south Aegean landmass. Extensive submarine coring has revealed the frequent occurrence of Quaternary dark, organic-rich layers in the cores retrieved from water depths greater than 180 m. Moreover, deep-sea drilling (DSDP leg 42A) in the south Aegean basin recovered organic-rich layers as old as late Miocene. Onshore the south Aegean Sea islands, organic-rich sediments are found at the north and south territories of the region, on Milos and Crete islands. Especially on the island of Crete and south of it, on the smaller islands of Gavdos and Koufonisi, these organic-rich sediments represent a considerable portion of the widespread upper Cenozoic sediments. Stratigraphically they cover the interval between upper Seravallian and lower Pleistocene. The organic carbon content of all these mostly calcareous lithofacies, the so-called sapropels, ranges mostly between 0.5 and 6.5%. The most reliably chronostratigraphically correlated upper Pleistocene sapropels display similar compositional characteristics across the entire basin. Certain Pleistocene and older organic-rich layers contain increased proportions of siliceous tests. However the entire range of sapropels in the region (except those within the Messinian evaporites) can be described adequately by the same lithofacies association. To demonstrate this the authors compare the lower Tortonian Faneromeni Formation on Crete with the upper Quaternary sediments from the south Aegean Sea.

  15. Extensional flow of blood analog solutions in microfluidic devices

    PubMed Central

    Sousa, P. C.; Pinho, F. T.; Oliveira, M. S. N.; Alves, M. A.

    2011-01-01

    In this study, we show the importance of extensional rheology, in addition to the shear rheology, in the choice of blood analog solutions intended to be used in vitro for mimicking the microcirculatory system. For this purpose, we compare the flow of a Newtonian fluid and two well-established viscoelastic blood analog polymer solutions through microfluidic channels containing both hyperbolic and abrupt contractions∕expansions. The hyperbolic shape was selected in order to impose a nearly constant strain rate at the centerline of the microchannels and achieve a quasihomogeneous and strong extensional flow often found in features of the human microcirculatory system such as stenoses. The two blood analog fluids used are aqueous solutions of a polyacrylamide (125 ppm w∕w) and of a xanthan gum (500 ppm w∕w), which were characterized rheologically in steady-shear flow using a rotational rheometer and in extension using a capillary breakup extensional rheometer (CaBER). Both blood analogs exhibit a shear-thinning behavior similar to that of whole human blood, but their relaxation times, obtained from CaBER experiments, are substantially different (by one order of magnitude). Visualizations of the flow patterns using streak photography, measurements of the velocity field using microparticle image velocimetry, and pressure-drop measurements were carried out experimentally for a wide range of flow rates. The experimental results were also compared with the numerical simulations of the flow of a Newtonian fluid and a generalized Newtonian fluid with shear-thinning behavior. Our results show that the flow patterns of the two blood analog solutions are considerably different, despite their similar shear rheology. Furthermore, we demonstrate that the elastic properties of the fluid have a major impact on the flow characteristics, with the polyacrylamide solution exhibiting a much stronger elastic character. As such, these properties must be taken into account in the

  16. Modes of tilting during extensional core complex development.

    PubMed

    Coleman, D S; Walker, J D

    1994-01-14

    Crustal extension and formation of the Mineral Mountains core complex, Utah, involved tilting of the Mineral Mountains batholith and associated faults during hanging wall and footwall deformation. The batholith was folded in the hanging wall of the Beaver Valley fault between 11 and 9 million years ago yielding about 45 degrees of tilt. Subsequently, the batholith was unroofed along the Cave Canyon detachment fault, and the batholith and fault were tilted approximately 40 degrees during footwall uplift. Recognition of deformed dikes beneath the detachment fault establishes the importance of footwall tilt during formation of extensional core complexes and demonstrates that footwall rebound can be an important process during extension.

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

    PubMed

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

    2006-04-28

    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

  18. Tsunami Propagation Database for the Mediterranean and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Kanoglu, U.; Hoto, O.; Kalligeris, N.; Flouri, E.; Aydin, B.; Moore, C. W.; Synolakis, C. E.

    2012-12-01

    Pre-computed tsunami scenario databases are common tools to develop long- or short-term forecasting methodologies and hazard assessment approaches for tsunami-prone regions worldwide. The benefits of such databases include the possibility of probabilistic studies (Gonzalez et al., 2009, J. Geophys. Res. 114, Article Number: C11023), inundation mapping (Barberopoulou et al., 2011, Pure Appl. Geophys. 168(11), 2133-2146), or real-time forecasting (Wei et al., 2008, Geophys. Res. Lett. 35(4), Article Number: L04609). As a result, several tsunami propagation databases have been developed including one by NOAA's Pacific Marine Environmental Laboratory (PMEL), and another by the Australian Bureau of Meteorology (BOM). Pre-computed tsunami scenario databases utilize different approaches. PMEL's tsunami propagation database is based on the concept of a pre-computed tsunami scenarios consisting of propagation results from 100km x 50km fault planes with a slip value of 1m referred to as tsunami source functions. PMEL's source functions are placed along the subduction zones in several rows, covering known faults throughout the major ocean basins. Linearity of the tsunami propagation in the open ocean allows scaling and/or combination of the pre-computed tsunami source functions to generate a desired scenario. The BOM database considers five earthquakes with magnitudes changing from 7.0 to 9.0 at each location with 100km intervals along the subduction zone. However, to date, no similar approach has been computed along the subduction zones in the Aegean and Mediterranean Seas, even though, historically, there have been a considerable number of tsunami events which caused damage in the region (Ambraseys and Synolakis, 2010, J. Earthquake Eng. 14 (3), 309-330, Article Number: PII 919600673). A new project was initiated between Greece and Turkey supported by General Secretariat for Research & Technology, The Ministry for Development (GSRT) of Greece and The Scientific and

  19. Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux Variability on Daily Through Decadal Time Scales

    NASA Technical Reports Server (NTRS)

    Romanski, Joy; Romanou, Anastasia; Bauer, Michael; Tselioudis, George

    2013-01-01

    We analyze daily wintertime cyclone variability in the central and eastern Mediterranean during 1958-2001, and identify four distinct cyclone states, corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc), and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux observations. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deep water formation was observed in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern (NCP), showing that the area of influence of large scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters.

  20. The economic determinants of Greek return migration to the islands of the East Aegean.

    PubMed

    Robolis, S; Xideas, E

    1996-01-01

    "The purpose of this article is to investigate the economic determinants of Greek return migration to the islands of the East Aegean, a region comprising hundreds of islands of different size in four administrative departments....[It] examines the sensitivity of return migration flows to changes in economic variables which influence decisions to return....The purpose...is to investigate the effect on return migration not only of economic development in the host country (push factors) but also of economic development in the islands of the East Aegean (pull factors), given their isolation from the mainland and their different economic structures." (SUMMARY IN SPA AND FRE)

  1. Folding associated with extensional faulting: Sheep Range detachment, southern Nevada

    SciTech Connect

    Guth, P.L.

    1985-01-01

    The Sheep Range detachment is a major Miocene extensional fault system of the Great Basin. Its major faults have a scoop shape, with straight, N-S traces extending 15-30 km and then abruptly turning to strike E-W. Tertiary deformation involved simultaneous normal faulting, sedimentation, landsliding, and strike-slip faulting. Folds occur in two settings: landslide blocks and drag along major faults. Folds occur in landslide blocks and beneath them. Most folds within landslide blocks are tight anticlines, with limbs dipping 40-60 degrees. Brecciation of the folds and landslide blocks suggests brittle deformation. Near Quijinump Canyon in the Sheep Range, at least three landslide blocks (up to 500 by 1500 m) slid into a small Tertiary basin. Tertiary limestone beneath the Paleozoic blocks was isoclinally folded. Westward dips reveal drag folds along major normal faults, as regional dips are consistently to the east. The Chowderhead anticline is the largest drag fold, along an extensional fault that offsets Ordovician units 8 km. East-dipping Ordovician and Silurian rocks in the Desert Range form the hanging wall. East-dipping Cambrian and Ordovician units in the East Desert Range form the foot wall and east limb of the anticline. Caught along the fault plane, the anticline's west-dipping west limb contains mostly Cambrian units.

  2. Pleistocene sand ramp deposits in the Aegean (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Draganits, E.; Zuschin, M.; Gier, S.; Bickel, L.

    2010-05-01

    Yellowish calcarenite is found abundantly on Despotiko, a small, unpopulated island in the central Aegean. Up to several meters thick layers of this sandstone is found as discordant cover above greenschist to amphibolite grade metamorphic rocks of the Attic-Cycladic Crystalline of the Central Hellenides. In some cases reddish soil is found below the sandstone. The calcarenite preferably fills preexisting relief of the underlying crystalline, therefore the thickest occurrences are found in the intermittent creeks. The sandstone can be traced from below sea-level up to around 90 m altitudes with abundant occurrences, but is most common at the north and northwest coast of the island. Generally, the sandstone layers and the internal lamination are parallel or at shallow angles to the slopes of the underlying crystalline without forming any morphological terraces. In some cases continuous layers of the sandstone can be traced for more than 20 m altitude. Cross-bedding has been observed in very rare cases and dips steeply towards the SE. The calcarenite (locally called "lithos poros") is strongly dominated by marine bioclasts (Corallinaceae, foraminifera, gastropod and bivalve fragments, etc.) with only minor siliciclastic components hardly exceeding 20%. The grains well-rounded and well-sorted with rain sizes range between medium sand to granule sizes. Based on the sandstone distribution in a high range of altitudes, sedimentary structures (e.g. pin-stripe lamination, high-angle cross bedding, rhizoliths, occurrence of terrestrial gastropod shells and correlation with almost identical sandstones in the Mediterranean) we conclude an aeolian origin and probably Pleistocene age of this sandstone. Horizons containing dm-sized, angular metamorphic clasts within well-rounded and well-sorted aeolian layers point to interaction of wind-blown and talus processes. Therefore these sediments are interpreted as sand ramps that formed during increased aeolian activity during the

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  4. Psychiatric Morbidity and Social Capital in Rural Communities of the Greek North Aegean Islands

    ERIC Educational Resources Information Center

    Tseloni, Andromachi; Zissi, Anastasia; Skapinakis, Petros

    2010-01-01

    Which facets of social capital affect mental health in rural settings? This study explores the association between different aspects of social capital and psychiatric morbidity in rural communities of the Greek North Aegean islands. A large number of individual and community characteristics that may influence psychiatric morbidity are concurrently…

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

    ERIC Educational Resources Information Center

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

    2009-01-01

    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. Structure of flows in the Northern Aegean Sea from a pilot drifter array

    NASA Astrophysics Data System (ADS)

    Kourafalou, V.; Olson, D.; Johns, W.; Kontoyiannis, H.; Zervakis, V.

    2003-04-01

    An array of thirty drifters deployed in the northern Aegean are used to consider the circulation in a complex archipelago of islands. The circulation of the Aegean is largely influenced by a combination of buoyancy from freshwaters introduced from the Black Sea via the Dardenelles Straits and from coastal rivers and by wind forcing. The latter is highly structured as the winds along the axis of the Aegean Sea are channeled between the orography of the Greek peninsula and islands. The above mechanisms are revealed in the drifter tracts. Preferred pathways that mark transport and exchange between the northern and southern parts of the basin are also evident. The drifters equipped with hourly GPS location and holly sock drogues provide information of time and space scales that have not been routinely sampled before. After a brief review of the overall circulation outlined by the array, the statistics of the turbulent field and its variation for the various subbasins are described. Of special interest are coastal plumes, motions induced as fluid passes between sub-basins, and the nature of cyclonic flows trapped within deep topographic pockets through the Aegean. An initial comparison of eddy statistics in relationship to wind events is also reported.

  7. A new approach to the structural features of the Aegean Sea: Cellular neural network

    NASA Astrophysics Data System (ADS)

    Aydogan, Davut; Elmas, Ali; Albora, A. Muhittin; Ucan, Osman N.

    2005-03-01

    In this study, structural features in the Aegean Sea were investigated by application of Cellular Neural Network (CNN) and Cross-Correlation methods to the gravity anomaly map. CNN is a stochastic image processing technique, which is based on template optimization using neighbourhood relationships of pixels, and probabilistic properties of two-Dimensional (2-D) input data. The performance of CNN can be evaluated by various interesting real applications in geophysics such as edge detection, data enhancement and separation of regional/residual potential anomaly maps. In this study, CNN is used in edge detection of geological bodies closer to the surface, which are masked by other structures with various depths and dimensions. CNN was first tested for (prismatic) synthetic examples and satisfactory results were obtained. Subsequently, CNN/Cross-Correlation maps and bathymetric features were evaluated together to obtain a new structural map for most of the Aegean Sea. In our structural map, the locations of the faults and basins are generally in accordance with the previous maps from restricted areas based on seismic data. In the southern and southeastern parts of the Aegean Sea, E-W trending faults cut NE-SW trending basins and faults, similar to on-shore Western Anatolia. Also, in the western, central and northern parts of the Aegean Sea, all of these structures are truncated by NE-trending faults.

  8. Shallow structure and recent evolution of the Aegean Sea deduced from the seismic reflection analysis

    SciTech Connect

    Laure, M.; Mascle, J.

    1988-08-01

    Together with the Tyrrhenian Sea, the Aegean Sea represents one of two marine basins still developing as a consequence of the subduction of the African lithosphere beneath Europe. Despite many geophysical similarities with the Tyrrhenian Sea, the Aegean displays a specific structural segmentation characterized by two distinct domains separated by the central Aegean. To the north of the basin, the so-called North Aegean trough likely represents the western marine extension of the transtensive Anatolian transform fault zone. The northern margin of this area contains a series of disconnected, often thickly sedimented small basins that probably initiated during the late Miocene as a consequence of a dominantly north-south extension; typical uppermost Miocene (Messinian) formations can be observed on seismic grounds. To the south, the Cretan Sea shows clear evidence of important distensive events occurring during two main episodes and following two main trends; a dominantly north-south-directed extension is responsibile for most of the structural features detected along both the Cretan and southern Cyclades margins.

  9. Extensional instability in electro-osmotic microflows of polymer solutions

    NASA Astrophysics Data System (ADS)

    Bryce, R. M.; Freeman, M. R.

    2010-03-01

    Fluid transport in microfluidic systems typically is laminar due to the low Reynolds number characteristic of the flow. The inclusion of suspended polymers imparts elasticity to fluids, allowing instabilities to be excited when substantial polymer stretching occurs. For high molecular weight polymer chains we find that flow velocities achievable by standard electro-osmotic pumping are sufficient to excite extensional instabilities in dilute polymer solutions. We observe a dependence in measured fluctuations on polymer concentration which plateaus at a threshold corresponding to the onset of significant molecular crowding in macromolecular solutions; plateauing occurs well below the overlap concentration. Our results show that electro-osmotic flows of complex fluids are disturbed from the steady regime, suggesting potential for enhanced mixing and requiring care in modeling the flow of complex liquids such as biopolymer suspensions.

  10. Microfluidic converging/diverging channels optimised for homogeneous extensional deformation

    PubMed Central

    Zografos, K.; Oliveira, M. S. N.

    2016-01-01

    In this work, we optimise microfluidic converging/diverging geometries in order to produce constant strain-rates along the centreline of the flow, for performing studies under homogeneous extension. The design is examined for both two-dimensional and three-dimensional flows where the effects of aspect ratio and dimensionless contraction length are investigated. Initially, pressure driven flows of Newtonian fluids under creeping flow conditions are considered, which is a reasonable approximation in microfluidics, and the limits of the applicability of the design in terms of Reynolds numbers are investigated. The optimised geometry is then used for studying the flow of viscoelastic fluids and the practical limitations in terms of Weissenberg number are reported. Furthermore, the optimisation strategy is also applied for electro-osmotic driven flows, where the development of a plug-like velocity profile allows for a wider region of homogeneous extensional deformation in the flow field. PMID:27478523

  11. Extensional hard linkages, eastern Gulf of Suez, Egypt

    NASA Astrophysics Data System (ADS)

    McClay, Ken; Khalil, Samir

    1998-06-01

    The Araba Abu Durba area on the eastern margin of the Gulf of Suez exhibits two superb outcrop examples of extensional hard linkages in a rift basin. Here, three large, domino-style, basement-cored, northeast-dipping fault blocks are formed by a series of major northwest-trending normal faults. These are offset by two north-northeast trending sinistral oblique-slip transfer faults that terminate in horsetail normal fault splays. The transfer faults do not extend across the entire rift basin. Detailed mapping and structural analysis show that they developed by breakage of initial low-strain relay ramps along reactivated north-northeast trending basement fabrics between overlapping northwest-trending normal fault segments. Paleostrain analysis of fault-slip indicators shows that both the normal and the sinistral oblique-slip transfer faults were formed synchronously in response to northeast-southwest extension, perpendicular to the main northwest rift trend.

  12. Microfluidic converging/diverging channels optimised for homogeneous extensional deformation.

    PubMed

    Zografos, K; Pimenta, F; Alves, M A; Oliveira, M S N

    2016-07-01

    In this work, we optimise microfluidic converging/diverging geometries in order to produce constant strain-rates along the centreline of the flow, for performing studies under homogeneous extension. The design is examined for both two-dimensional and three-dimensional flows where the effects of aspect ratio and dimensionless contraction length are investigated. Initially, pressure driven flows of Newtonian fluids under creeping flow conditions are considered, which is a reasonable approximation in microfluidics, and the limits of the applicability of the design in terms of Reynolds numbers are investigated. The optimised geometry is then used for studying the flow of viscoelastic fluids and the practical limitations in terms of Weissenberg number are reported. Furthermore, the optimisation strategy is also applied for electro-osmotic driven flows, where the development of a plug-like velocity profile allows for a wider region of homogeneous extensional deformation in the flow field.

  13. Microfluidic converging/diverging channels optimised for homogeneous extensional deformation.

    PubMed

    Zografos, K; Pimenta, F; Alves, M A; Oliveira, M S N

    2016-07-01

    In this work, we optimise microfluidic converging/diverging geometries in order to produce constant strain-rates along the centreline of the flow, for performing studies under homogeneous extension. The design is examined for both two-dimensional and three-dimensional flows where the effects of aspect ratio and dimensionless contraction length are investigated. Initially, pressure driven flows of Newtonian fluids under creeping flow conditions are considered, which is a reasonable approximation in microfluidics, and the limits of the applicability of the design in terms of Reynolds numbers are investigated. The optimised geometry is then used for studying the flow of viscoelastic fluids and the practical limitations in terms of Weissenberg number are reported. Furthermore, the optimisation strategy is also applied for electro-osmotic driven flows, where the development of a plug-like velocity profile allows for a wider region of homogeneous extensional deformation in the flow field. PMID:27478523

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

    NASA Astrophysics Data System (ADS)

    Androulidakis, Yannis; Krestenitis, Yannis; Kourafalou, Vassiliki

    2013-04-01

    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

  15. The role of rheology in extensional basin formation modelling

    NASA Astrophysics Data System (ADS)

    Fernàndez, M.; Ranalli, G.

    1997-12-01

    The rheology of the lithosphere determines its deformation under given initial and boundary conditions. This paper presents a critical discussion on how rheological properties are taken into account in extensional basin modelling. Since strength envelopes are often used in models, we review the uncertainties (in temperature and rheological parameters) and assumptions (in type of rheology and mode of deformation) involved in their construction. Models of extensional basins are classified into three groups: kinematic, kinematic with rheological constraints, and dynamic. Rheology enters kinematic models only implicitly, in the assumption of an isostatic compensation mechanism. We show that there is a critical level of necking that reconciles local isostasy with the finite strength of the lithosphere, which requires a flexural response. Kinematic models with rheological constraints make use of strength envelopes to assess the initial lateral variations of lithospheric strength and its evolution with time at the site of extension. Dynamic models are the only ones to explicitly introduce rheological constitutive equations (usually in plane strain or plane stress). They usually, however, require the presence of an initial perturbation (thickness variations, pre-existing faults, thermal inhomogeneities, rheological inhomogeneities). The mechanical boundary conditions (kinematic and dynamic) and the thermal boundary conditions (constant temperature or constant heat flux at the lower boundary of the lithosphere) may result in negative/positive feedbacks leading to cessation/acceleration of extension. We conclude that, while kinematic models (with rheological constraints if possible) are very successful in accounting for the observed characteristics of sedimentary basins, dynamic models are necessary to gain insight into the physical processes underlying basin formation and evolution.

  16. The Extensional Rheology of Non-Newtonian Materials

    NASA Technical Reports Server (NTRS)

    Spiegelberg, Stephen H.; McKinley, Gareth H.

    1996-01-01

    The evolution of the transient extensional stresses in dilute and semi-dilute viscoelastic polymer solutions are measured with a filament stretching rheometer of a design similar to that first introduced by Sridhar, et al. The solutions are polystyrene-based (PS) Boger fluids that are stretched at constant strain rates ranging from 0.6 less than or equal to epsilon(0) less than or equal to 4s(exp -1) and to Hencky strains of epsilon greater than 4. The test fluids all strain harden and Trouton ratios exceeding 1000 are obtained at high strains. The experimental data strain hardens at lower strain levels than predicted by bead-spring FENE models. In addition to measuring the transient tensile stress growth, we also monitor the decay of the tensile viscoelastic stress difference in the fluid column following cessation of uniaxial elongation as a function of the total imposed Hencky strain and the strain rate. The extensional stresses initially decay very rapidly upon cessation of uniaxial elongation followed by a slower viscoelastic relaxation, and deviate significantly from FENE relaxation predictions. The relaxation at long times t is greater than or equal to 5 s, is compromised by gravitational draining leading to non-uniform filament profiles. For the most elastic fluids, partial decohension of the fluid filament from the endplates of the rheometer is observed in tests conducted at high strain rates. This elastic instability is initiated near the rigid endplate fixtures of the device and it results in the progressive breakup of the fluid column into individual threads or 'fibrils' with a regular azimuthal spacing. These fibrils elongate and bifurcate as the fluid sample is elongated further. Flow visualization experiments using a modified stretching device show that the instability develops as a consequence of an axisymmetry-breaking meniscus instability in the nonhomogeneous region of highly deformed fluid near the rigid endplate.

  17. Microbial activities at the benthic boundary layer in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Bianchi, A.; Tholosan, O.; Garcin, J.; Polychronaki, T.; Tselepides, A.; Buscail, R.; Duineveld, G.

    2003-05-01

    During the Aegean Sea component of the EU MTP-MATER project, benthic samples were acquired along a depth gradient from two continental margins in the Aegean Sea. Sampling was undertaken during spring and summer 1997 and the microbial metabolic activities measured (Vmax for aminopeptidase activity, 14C-glutamate respiration and assimilation) displayed seasonal variability even in deep-sea conditions. The metabolic rates encountered in the North Aegean (average depth 566±234 m), were approximately five-fold higher than in the deeper (1336±140 m) Southern part of the Aegean. The aminopeptidase rates, however, were the exception with higher values recorded in the more oligotrophic sediments of the Southern stations (1383±152 vs. 766±297 nmol MCA cm -2 h -1). A discrepancy in bacterial metabolism also appeared in the near bottom waters. In the Southern stations, 80% of the glutamate uptake was used for energy yielding processes and only 20% devoted to biomass production, while in the North Aegean, most of the used glutamate was incorporated into bacterial cells. During the early burial stages, bacterial mineralization rates estimated from 14C-glutamate respiration decreased drastically compared to the rates of biopolymer hydrolysis estimated by aminopeptidase assays. Thus, at the 2-cm depth layer, these rates were only 32 and up to 77% of the corresponding average values, respectively, in the superficial layer. Such a discrepancy between the evolution of these two metabolic activities is possibly due to the rapid removal of readily utilizable monomers in the surface deposits. The correlation between bacterial respiration and total organic carbon, or total organic nitrogen, is higher in the surficial sediment (0-2 and 2-4 cm) than in the underlying layer. Conversely, it is only at 4-cm depth layer that the hydrolysis rates appear correlated with organic carbon and nitrogen concentrations. This pattern confirms the drastic degradation of organic matter during the

  18. The interaction between Aegean back-arc extension and Anatolia escape since Late Miocene

    NASA Astrophysics Data System (ADS)

    Philippon, M. M.; Brun, J. P.; Gueydan, F.; Sokoutis, D.

    2015-12-01

    The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Using laboratory experiments designed to study lithosphere-scale deformation, we show that the overall pattern of Aegean extension requires not only the combination of trench retreat and Anatolia escape since 15 Ma but also the presence of an inherited lithosphere-scale mechanical discontinuity: the Vardar Suture Zone (VSZ). The reactivation in dextral shear of the eastern branch of the VSZ accommodates both the trench retreat (NS stretching) and the westward escape of Anatolia (EW shortening) in the Cyclades area since 15 Ma. Additionally, our model shows that the North Anatolian Fault (NAF) is a late structure in the evolution of the Aegean, initiated 10 Ma after the onset of Anatolia escape. The model displays displacement sub-domains, which result from strain partitioning instead of being "rigid microplates", directly comparable to the present-day displacement field (GPS) of the Aegean and western Anatolia. Our modelling provides a simple way to look at the dynamics of Aegean extension in two main stages. From middle Eocene to middle Miocene, extension was only driven by the southward retreat of the Hellenic trench at a rate lower than 1 cm.y-1. Since middle Miocene, the combination of slab rollback with Anatolia westward escape, resulted in a southwest direction of trench retreat, with an accelerating rate of up to 3 cm.y-1.

  19. Plant speciation in continental island floras as exemplified by Nigella in the Aegean Archipelago.

    PubMed

    Comes, Hans Peter; Tribsch, Andreas; Bittkau, Christiane

    2008-09-27

    Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of geographical isolation on non-adaptive radiation and allopatric speciation brought about by genetic drift. The Aegean Archipelago forms a highly fragmented complex of mostly continental shelf islands that have become disconnected from each other and the mainland in relatively recent geological times (ca <5.2 Ma). These ecologically fairly homogenous islands thus provide a suitable biogeographic context for assessing the relative influences of past range fragmentation, colonization, gene flow and drift on taxon diversification. Indeed, recent molecular biogeographic studies on the Aegean Nigella arvensis complex, combining phylogenetic, phylogeographic and population level approaches, exemplify the importance of allopatry and genetic drift coupled with restricted gene flow in driving plant speciation in this continental archipelago at different temporal and spatial scales. While the recent (Late Pleistocene) radiation of Aegean Nigella, as well as possible instances of incipient speciation (in the Cyclades), is shown to be strongly conditioned by (palaeo)geographic factors (including changes in sea level), shifts in breeding system (selfing) and associated isolating mechanisms have also contributed to this radiation. By contrast, founder event speciation has probably played only a minor role, perhaps reflecting a migratory situation typical for continental archipelagos characterized by niche pre-emption because of a long established resident flora. Overall, surveys of neutral molecular markers in Aegean Nigella have so far revealed population genetic processes that conform remarkably well to predictions raised by genetic drift theory. The challenge is now to gain more direct insights into the relative importance of the role of genetic drift, as opposed to natural selection, in the phenotypic and reproductive divergence among these Aegean plant

  20. Anelastic attenuation structure of the southern Aegean subduction area

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  1. Aspects of three-dimensional strain at the margin of the extensional orogen, Virgin River depression area, Nevada, Utah, and Arizona

    USGS Publications Warehouse

    Anderson, R.E.; Barnhard, T.P.

    1993-01-01

    The Virgin River depression and surrounding mountains are Neogene features that are partly contiguous with the little-strained rocks of the structural transition to the Colorado Plateau province. This contiguity makes the area ideally suited for evaluating the sense, magnitude, and kinematics of Neogene deformation. Analysis along the strain boundary shows that, compared to the adjacent little-strained area, large-magnitude vertical deformation greatly exceeds extensional deformation and that significant amounts of lateral displacement approximately parallel the province boundary. Isostatic rebound following tectonic denudation is an unlikely direct cause of the strong vertical structural relief adjacent to the strain boundary. Instead, the observed structures are first-order features defining a three-dimensional strain field produced by approximately east-west extension, vertical structural attenuation, and extension-normal shortening. All major structural elements of the strain-boundary strain field are also found in the adjacent Basin and Range. -from Authors

  2. On dense water formation in shelves of the Aegean Sea during the year 1987

    NASA Astrophysics Data System (ADS)

    Salusti, Ettore; Bellacicco, Marco; Anagnostou, Christos; Rinaldi, Eleonora; Tripsanas, Efthymios

    2015-04-01

    We here investigate the role of the rather virgin year 1987, when some modern data are available but before the main EMT event. A combination of field, satellite and numerical model temperature and salinity data from PROTHEUS, as well as a coupled ocean-atmosphere model, are used to implement theoretical models. After its formation over a sloping shelf of some important points in the Aegean Sea, due to the strong cold winter winds, a dense water patch can either have a dramatic downflow or can start a slow geostrophic descent along shelves and then following isobaths, best described by streamtube models. The most important, among these shelves characterized by a strong air sea interaction, have been identified from satellite data. The Northernmost shelves are those north of the island of Samothrace and in the Northern Thermaikos Gulf. In agreement with the field measuraments of Georgopoulos et al. (1987) also the shallow shelf between Limnos and Goceada was a source of very dense water, as well as thr shelf between Lesbos and the Turkish coast. Most probably also the shelves around the Cycladic Plateau were affected by strong winds and contributed to the Aegean Sea deep water formation. In addition, other theoretical models of wind-induced coastal upwelling allow to infer temperature and salinity information of dense water dynamics along the shallow coasts and shelves of the Aegean Sea. All this allows a heuristic application of classical T/S diagrams to estimate Northern Aegean dense water evolution and spreading, that nicely supports the early ideas of Zervakis et al. (2000). A complex situation about the Cycladic Plateau dynamics is also analyzed in correlation with sediment locations. Indeed seismic-reflection profiles confirm the presence of a contourite location along the northeast Cyclades Plateau shelves. All this interestingly opens novel prospective about the dense water coastal formation shelves. In synthesis such field, numerical and satellite data

  3. Analysis of Neogene deformation between Beaver, Utah, and Barstow, California: suggestions for altering the extensional paradigm

    USGS Publications Warehouse

    Anderson, R. Ernest; Beard, L. Sue; Mankinen, Edward A.; Hillhouse, John W.

    2013-01-01

    For more than two decades, the paradigm of large-magnitude (~250 km), northwest-directed (~N70°W) Neogene extensional lengthening between the Colorado Plateau and Sierra Nevada at the approximate latitude of Las Vegas has remained largely unchallenged, as has the notion that the strain integrates with coeval strains in adjacent regions and with plate-boundary strain. The paradigm depends on poorly constrained interconnectedness of extreme-case lengthening estimated at scattered localities within the region. Here we evaluate the soundness of the inferred strain interconnectedness over an area reaching 600 km southwest from Beaver, Utah, to Barstow, California, and conclude that lengthening is overestimated in most areas and, even if the estimates are valid, lengthening is not interconnected in a way that allows for published versions of province-wide summations. We summarize Neogene strike slip in 13 areas distributed from central Utah to Lake Mead. In general, left-sense shear and associated structures define a broad zone of translation approximately parallel to the eastern boundary of the Basin and Range against the Colorado Plateau, a zone we refer to as the Hingeline shear zone. Areas of steep-axis rotation (ranging to 2500 km2) record N-S shortening rather than unevenly distributed lengthening. In most cases, the rotational shortening and extension-parallel folds and thrusts are coupled to, or absorb, strike slip, thus providing valuable insight into how the discontinuous strike-slip faults are simply parts of a broad zone of continuous strain. The discontinuous nature of strike slip and the complex mixture of extensional, contractional, and steep-axis rotational structures in the Hingeline shear zone are similar to those in the Walker Lane belt in the west part of the Basin and Range, and, together, the two record southward displacement of the central and northern Basin and Range relative to the adjacent Colorado Plateau. Understanding this province

  4. Isotopic evidence of source variations in commingled magma systems: Colorado River extensional corridor, Arizona and Nevada

    SciTech Connect

    Metcalf, R.V.; Smith, E.I.; Martin, M.W. . Dept. of Geoscience); Gonzales, D.A.; Walker, J.D. . Isotope Geochronology Lab.)

    1993-04-01

    Mixing of mantle derived mafic and crustal derived felsic magmas is a major Province-wide process forming Tertiary intermediate magmas within the Basin and Range. Major variations in magma sources, however, may exist in temporally and spatially related systems. Such variations are exemplified by two closely spaced plutons within the northern Colorado River extensional corridor. The 15.96 Ma Mt. Perkins pluton (MPP) was emplaced in three major phases: phase 1 (oldest) gabbro; phase 2 quartz diorite to hornblende granodiorite; and phase 3 biotite granodiorite ([+-]hbld). Phases 2 and 3 contain mafic microgranitoid enclaves (MME) that exhibit evidence of magma mingling. Combined data from phase 2 and 3 rocks, including MMW, shows positive [sup 87]Sr/[sup 86]Sr and negative [var epsilon]Nd correlations vs. SiO[sub 2] (50--72 wt %). Phase 2 rocks, which plot between phase 2 MME and MME-free phase 3 granodiorite, represent hybrid magmas formed by mixing of mantle and crustal derived magmas. Phase 1 gabbro falls off isotope-SiO[sub 2] trends and represents a separate mantle derived magma. The 13.2 Ma Wilson Ridge pluton (WRP), <20 km north of MPP, is cogenetic with the river Mountains volcano (RMV). In WRP an early diorite was intruded by a suite of monzodiorite to quartz monzonite. The monzodiorite portion contains MME and mafic schlieren representing mingled and mixed mafic magmas. The WRP and MPP represent two closely spaced isotopically distinct and separate magma systems. There are five magma sources. The two felsic mixing end members represent two different crustal magma sources. Two mantle sources are presented by MPP phase 1 gabbro and phase 2 MME, reflecting lithospheric and asthenospheric components, respectively. The latter represents the oldest reported Tertiary asthenospheric component within the region. A single lithospheric mantle source, different from the MPP gabbro, is indicated for the mafic mixing end member in the WRP-RMV suite.

  5. Quantitative Identification and Analysis of Sub-Seismic Extensional Structure System: Technique Schemes and Processes

    NASA Astrophysics Data System (ADS)

    Ou, C.; Chen, W.

    2014-12-01

    Quantitative characterization of complex sub-seismic extensional structure system that essentially controls petroleum exploitation is difficult to implement in seismic profile interpretation. This research, based on a case study in block M of Myanmar, established a set of quantitative treatment schemes and technique processes for the identification of sub-seismic low-displacement (SSLD) extensional faults or fractures upon structural deformation restoration and geometric inversion. Firstly, the master-subsidiary inheritance relations and configuration characterization of the seismic-scale extensional fault systems are determined by analyzing the structural pattern. Besides, three-dimensional (3D) pattern and characteristics of the seismic-scale extensional structure have been illustrated by 3D structure model built upon seismic sections. Moreover, according to the dilatancy obtained from structural restoration on the basis of inclined shear method, as well as the fracture-flow index, potential SSLD extensional faults or fractures have been quantitatively identified. Application of the technique processes to the sub-seismic low-displacement extensional structures in block M in Myanmar is instructive to quantitatively interpret those SSLD extensional structure systems in practice. The work was supported by National Basic Research Program of China (2014CB239205) and the National Science and Technology Major Project of China (20011ZX05030-005-003).

  6. Quantitative identification and analysis of sub-seismic extensional structure system: technique schemes and processes

    NASA Astrophysics Data System (ADS)

    Chenghua, Ou; Chen, Wei; Ma, Zhonggao

    2015-06-01

    Quantitative characterization of complex sub-seismic extensional structure system that essentially controls petroleum exploitation is difficult to implement in seismic profile interpretation. This research, based on a case study in block M of Myanmar, established a set of quantitative treatment schemes and technique processes for the identification of sub-seismic low-displacement (SSLD) extensional faults or fractures upon structural deformation restoration and geometric inversion. Firstly, the master-subsidiary inheritance relations and configuration of the seismic-scale extensional fault systems are determined by analyzing the structural pattern. Besides, three-dimensional (3D) pattern and characteristics of the seismic-scale extensional structure have been illustrated by a 3D structure model built upon seismic sections. Moreover, according to the dilatancy obtained from structural restoration on the basis of inclined shear method, as well as the fracture-flow index, potential SSLD extensional faults or fractures have been quantitatively identified. Application of the technique processes to the sub-seismic low-displacement extensional structures in block M in Myanmar is instructive to quantitatively interpret those SSLD extensional structure systems in practice.

  7. Cell stretching in extensional flows for assaying cell mechanics

    NASA Astrophysics Data System (ADS)

    Gossett, Daniel; Tse, Henry; Adeyiga, Oladunni; Yang, Otto; Rao, Jianyu; di Carlo, Dino

    2013-03-01

    There is growing evidence that cell deformability is a useful indicator of cell state and may be a label-free biomarker of metastatic potential, degree of differentiation, and leukocyte activation. In order for deformability measurements to be clinically valuable given the heterogeneity of biological samples, there exists a need for a high-throughput assay of this biophysical property. We developed a robust method for obtaining high-throughput (>1,000 cells/sec) single-cell mechanical measurements which employs coupled hydrodynamic lift forces and curvature-induced secondary flows to uniformly position cells in flow, extensional flow stretching, high-speed imaging, and automated image analysis to extract diameter and deformability parameters. Using this method we have assayed numerous in vitro models of cellular transformations and clinical fluids where malignant cells manifest. We found transformations associated with increased motility or invasiveness increased deformability and the presence of large and deformable cells within clinical pleural fluids correlated well with cytological diagnoses of malignancy. This agrees with the hypothesis that cancerous cells are deformable by necessity-to be able to transverse tight endothelial gaps and invade tissues.

  8. Shear History Extensional Rheology Experiment: A Proposed ISS Experiment

    NASA Technical Reports Server (NTRS)

    Hall, Nancy R.; Logsdon, Kirk A.; Magee, Kevin S.

    2007-01-01

    The Shear History Extensional Rheology Experiment (SHERE) is a proposed International Space Station (ISS) glovebox experiment designed to study the effect of preshear on the transient evolution of the microstructure and viscoelastic tensile stresses for monodisperse dilute polymer solutions. Collectively referred to as Boger fluids, these polymer solutions have become a popular choice for rheological studies of non-Newtonian fluids and are the non-Newtonian fluid used in this experiment. The SHERE hardware consists of the Rheometer, Camera Arm, Interface Box, Cabling, Keyboard, Tool Box, Fluid Modules, and Stowage Tray. Each component will be described in detail in this paper. In the area of space exploration, the development of in-situ fabrication and repair technology represents a critical element in evolution of autonomous exploration capability. SHERE has the capability to provide data for engineering design tools needed for polymer parts manufacturing systems to ensure their rheological properties have not been impacted in the variable gravity environment and this will be briefly addressed.

  9. Extensional diapirism in the eastern Prebetic foldbelt, southeastern Spain

    SciTech Connect

    Ruig, M.J. de

    1996-12-31

    The influence of tectonic stress on the initiation and development of evaporite diapirs is of great importance in the interpretation of diapiric structures and associated sediments. The eastern Prebetic foldbelt in southeastern Spain contains many diapirs that provide excellent examples of tectonically controlled diapirism. These diapirs are mainly composed of Triassic evaporite and shale that have pierced their overburden along extensional faults and in releasing oversteps along strike-slip faults. They occur as highly elongated diapiric walls or as large, fault-bounded bodies that can cover several tens of square kilometers at the center of grabens. Most of these diapirs reached the surface in Neogene times, constituting local depocenters for Miocene sediments. Outcrop and well data suggest that their source layer consists mainly of interbedded shale and anhydrite, which are denser than their carbonate overburden and thus preclude piercement diapirism driven by buoyancy. The external geometry of these diapirs and a variety of kinematic indicators in surrounding overburden suggest that their location and initiation was primarily controlled by (trans)tensional faulting. It is therefore concluded that the Prebetic diapirs formed in response to thin-skinned extension of their overburden, which induced differential loading and viscous flow of the Triassic evaporites. Regional paleostress analysis and chronostratigraphic correlation suggest that diapirism was triggered by rifting in the adjacent Western Mediterranean Basin.

  10. Divergence preceding island formation among Aegean insular populations of the freshwater snail genus Pseudorientalia (Caenogastropoda: Truncatelloidea).

    PubMed

    Szarowska, Magdalena; Hofman, Sebastian; Osikowski, Artur; Falniowski, Andrzej

    2014-10-01

    Freshwater snails that inhabit islands are excellent model organisms for testing relationships between geological events and phylogeography, especially in the Aegean region. Although many Aegean islands were searched in the present study, species of the genus Pseudorientalia were only found on Lesvos, Samos, and Chios. Phylogenetic relationships between specimens living on these three islands were analysed using COI and 16S rRNA molecular markers and morphological data. A high level of diversity was found between islands. Genetic distances between clades showed differences high enough for the samples from different islands to be considered distinct species (p-distance: 0.105-0.133). These results are also supported by obvious morphological differences in shell morphology between islands. The mean divergence time between the Lesvos clade and Samos/Chios clade was 24.13 ± 3.30 Mya; between the Samos and Chios clades the divergence time was 14.80 ± 1.11 Mya. Our data suggest that high divergence may have occurred between Pseudorientalia populations during the Upper and Middle Miocene, when the Aegean region was part of a united landmass. It is possible that the observed highly divergent Pseudorientalia clades are relicts of high regional diversity that existed in the past. PMID:25284387

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

    PubMed

    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

    2016-05-25

    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

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

    PubMed

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

    2011-04-01

    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.

  13. The effect of shear and extensional viscosity on atomization in medical inhaler.

    PubMed

    Broniarz-Press, L; Ochowiak, M; Matuszak, M; Włodarczak, S

    2014-07-01

    The paper contains the results of experimental studies of water, aqueous solutions of glycerol and aqueous solutions of glycerol-polyethylene oxide (PEO) atomization process in a medical inhaler obtained by the use of the digital microphotography method. The effect of the shear and extensional viscosity on the drop size, drop size histogram and mean drop diameter has been analyzed. The obtained results have shown that the drop size increases with the increase in shear and extensional viscosity of liquid atomized. Extensional viscosity has a greater impact on the spraying process. It has been shown that the change in liquid viscosity leads to significant changes in drop size distribution. The correlation for Sauter mean diameter as function of the shear and extensional viscosity was proposed.

  14. Dynamic linear viscoelastic properties and extensional failure of asphalt binders

    NASA Astrophysics Data System (ADS)

    Ruan, Yonghong

    properties at both high and low temperatures. Polymeric modifiers improve asphalt binders' ductility greatly, improvement that diminishes with aging. The extensional flow of modified binders is strikingly different from that of straight asphalts.

  15. The effects of extensional inheritance on transtensional deformation patterns

    NASA Astrophysics Data System (ADS)

    Naliboff, J.; Buiter, S. J.; Le Pourhiet, L.; May, D.

    2015-12-01

    Continental rifting and breakup frequently occurs through multiple phases of extension in which margin architecture is governed by distinct modes of brittle and viscous deformation, as well as surface processes. Transitions between such phases of extension may in some cases reflect plate-scale changes in extension obliquity and velocity. For example, recent studies indicate that localization of transtensional deformation onto a narrow shear zone in the Gulf of California Rift corresponds temporally with an increase in rift obliquity. Here, we use high-resolution 3-D models (run with pTatin3D) to examine how transtensional deformation patterns evolve with such increases in extension obliquity. Our models build on previous crustal-scale analogue and numerical studies examining oblique reactivation of normal faults. These studies show that the orientation and strength of inherited normal faults strongly control the style of slip and deformation partitioning between new and reactivated faults. While highly insightful, these studies examine deformation over limited spatial extents and do not account for key processes such as isostasy and temperature-dependent rock strength. Here, we model the thermal-mechanical evolution of the lithosphere and asthenosphere to a depth of 200 km. Deformation occurs through an initial phase of orthogonal, Basin and Range style extension, followed by 1-2 phases of extension at different obliquities. The initial lithospheric structure and time-dependent boundary conditions follow geologic observations and plate-reconstructions within the Gulf of California. Our experiments highlight the strong control of inheritance on transtensional crustal deformation. By comparing fault development, crustal thickness evolution and block rotations directly with observations from the Gulf of California and other extensional and transtensional regions, we can better evaluate the relative control of structural inheritance on passive margin architecture.

  16. Shear History Extensional Rheology Experiment II (SHERE II) Microgravity Rheology with Non-Newtonian Polymeric Fluids

    NASA Technical Reports Server (NTRS)

    Jaishankar, Aditya; Haward, Simon; Hall, Nancy Rabel; Magee, Kevin; McKinley, Gareth

    2012-01-01

    The primary objective of SHERE II is to study the effect of torsional preshear on the subsequent extensional behavior of filled viscoelastic suspensions. Microgravity environment eliminates gravitational sagging that makes Earth-based experiments of extensional rheology challenging. Experiments may serve as an idealized model system to study the properties of lunar regolith-polymeric binder based construction materials. Filled polymeric suspensions are ubiquitous in foods, cosmetics, detergents, biomedical materials, etc.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  18. Interior provinces in Alaska

    SciTech Connect

    Kirschner, C.E.; Fisher, M.A.; Bruns, T.R.; Stanley, R.G.

    1985-04-01

    Three types of interior provinces have been tested by exploratory drilling for their petroleum potential: three Tertiary nonmarine basins, two Jurassic and Cretaceous flysch and fold belts, and a Paleozoic thrust belt. Although the presence of hydrocarbons has not yet been demonstrated, the present data base is too limited to make a definitive assessment of hydrocarbon potential. During the 1983-84 field seasons, the authors acquired new gravity data and collected rock samples in and adjacent to the Yukon flats and the Nenana basins. These basins contain upper Tertiary, primarily nonmarine, sedimentary rock in extensional graben and half-graben complexes that are superimposed across preexisting terrane boundaries. The location and development of the basins result from strike-slip motion along the Tintina and Denali fault systems. Adjacent to the basins and within the fault systems are thick sections of nonmarine lower Tertiary coal-bearing rocks in deformed basin remnants. If these lower Tertiary rocks are present beneath the upper Tertiary fill, their greater depth and advanced maturation could enhance the hydrocarbon generative potential. Gravity modelling suggests the Tertiary fill is at least 3 km thick in the deeper parts of the basins and may be significantly thicker.

  19. Modelling the impact of Black Sea water inflow on the North Aegean Sea hydrodynamics

    NASA Astrophysics Data System (ADS)

    Tzali, Margarita; Sofianos, Sarantis; Mantziafou, Anneta; Skliris, Nikolaos

    2010-06-01

    The impact of the Black Sea Water (BSW) inflow on the circulation and the water mass characteristics of the North Aegean Sea is investigated using a high-resolution 3D numerical model. Four climatological numerical experiments are performed exploring the effects of the exchange amplitude at the Dardanelles Straits in terms of the mean annual volume exchanged and the amplitude of its seasonal cycle. Larger inflow of low salinity BSW influences the water characteristics of the whole basin. The largest salinity reduction is encountered in the upper layers of the water column, and the most affected region is the northeastern part of the basin. The winter insulation character of the BSW layer (low-salinity layer) is reduced by the seasonal cycle of the inflow (minimum during winter). The maximum atmospheric cooling coincides with the minimum BSW inflow rate, weakening the vertical density gradients close to the surface and thus facilitating the vertical mixing. The inflow rate of BSW into the North Aegean Sea constitutes an essential factor for the circulation in the basin. Increased inflow rate results into considerably higher kinetic energy, stronger circulation and reinforcement of the mesoscale circulation features. Although the position of the front between BSW and waters of Levantine origin does not vary significantly with the intensity of the BSW inflow rate, the flow along the front becomes stronger and more unstable as the inflow rate increases, forming meanders and rings. The changes in the intensity of BSW inflow rate overpower the wind and thermohaline forcing and largely determine the general circulation of the North Aegean Sea.

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

    USGS Publications Warehouse

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

    2007-01-01

    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.

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

    USGS Publications Warehouse

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

    2007-01-01

    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).

  2. New Constraints on Extensional Environments through Analysis of Teleseisms

    NASA Astrophysics Data System (ADS)

    Eilon, Zachary Cohen

    We apply a variety of teleseismic methodologies to investigate the upper mantle structure in extensional environments. Using a body wave dataset collected from a regional deployment in the Woodlark Rift, Papua New Guinea, we image anisotropic velocity structure of a rapidly extending rift on the cusp of continental breakup. In the process, we develop a technique for azimuthal anisotropy tomography that is generally applicable to regions of relatively simple anisotropic structure. The Cascadia Initiative ocean bottom seismometer (OBS) deployment provides coverage of an entire oceanic plate in unprecedented detail; we measure attenuation and velocities of teleseisms to characterize the temperature and melt structure from ridge to trench. Our study of shear wave splitting reveals strong azimuthal anisotropy within the Woodlark Rift with fairly uniform fast directions parallel to extension. This observation differs markedly from other continental rifts and resembles the pattern seen at mid-ocean ridges. This phenomenon is best explained by extension-related strain causing preferential alignment of mantle olivine. We develop a simple relationship that links total extension to predicted splitting, and show that it explains the apparent dichotomy in rifts' anisotropy. Finite frequency tomography using a dataset of teleseismic P- and S-wave differential travel times reveals the upper mantle velocity structure of the Woodlark Rift. A well developed slow rift axis extending >250 km along strike from the adjacent seafloor spreading centers demonstrates the removal of mantle lithosphere prior to complete crustal breakup. We argue that the majority of this rift is melt-poor, in agreement with geochemical results. A large temperature gradient arises from the juxtaposition of upwelled axial asthenosphere with a previously unidentified cold structure north of the rift that hosts well located intermediate depth earthquakes. Localization of upper mantle extension is apparent from

  3. Recent extensional tectonics on the Moon revealed by the Lunar Reconnaissance Orbiter Camera

    NASA Astrophysics Data System (ADS)

    Watters, Thomas R.; Robinson, Mark S.; Banks, Maria E.; Tran, Thanh; Denevi, Brett W.

    2012-03-01

    Large-scale expressions of lunar tectonics--contractional wrinkle ridges and extensional rilles or graben--are directly related to stresses induced by mare basalt-filled basins. Basin-related extensional tectonic activity ceased about 3.6 Gyr ago, whereas contractional tectonics continued until about 1.2 Gyr ago. In the lunar highlands, relatively young contractional lobate scarps, less than 1 Gyr in age, were first identified in Apollo-era photographs. However, no evidence of extensional landforms was found beyond the influence of mare basalt-filled basins and floor-fractured craters. Here we identify previously undetected small-scale graben in the farside highlands and in the mare basalts in images from the Lunar Reconnaissance Orbiter Camera. Crosscut impact craters with diameters as small as about 10m, a lack of superposed craters, and graben depths as shallow as ~1m suggest these pristine-appearing graben are less than 50 Myr old. Thus, the young graben indicate recent extensional tectonic activity on the Moon where extensional stresses locally exceeded compressional stresses. We propose that these findings may be inconsistent with a totally molten early Moon, given that thermal history models for this scenario predict a high level of late-stage compressional stress that might be expected to completely suppress the formation of graben.

  4. X-ray scattering studies of ordered block copolymer melts during uniaxial extensional flow

    NASA Astrophysics Data System (ADS)

    Burghardt, Wesley; Mao, Ruinan; McCready, Erica

    2012-02-01

    We present the design and implementation of a new apparatus for in situ x-ray scattering studies of polymer melts during homogenous uniaxial extensional flow. The instrument is based on the commercial SER extensional flow fixture, which employs counter-rotating drums to deform a strip of polymer melt, which is incorporated into a custom-built convection oven designed to facilitate x-ray access to the sample and operation in a synchrotron environment. Here we report measurements of extensional flow-induced structural changes in a cylindrically ordered styrene-ethylene butylene-styrene triblock copolymer melt. At early stages, SAXS data reveal that the ordered microstructure deforms affinely until Hencky strains of ˜ 0.2. A global re-orientation process leads to alignment of microdomains predominantly along the stretching direction after Hencky strains of ˜ 1. Further stretching does not lead to further qualitative changes in 2-D SAXS patterns. Relaxation of both microdomain orientation and d-spacing is observed following cessation of extensional flow, albeit with different characteristic time scales. In situ x-ray scattering data are compared with off-line measurements of transient extensional viscosity, performed using the SER fixture in a rotational rheometer.

  5. New discovery and geological significance of Late Silurian-Carboniferous extensional structures in Tarim Basin

    NASA Astrophysics Data System (ADS)

    Li, Yue-Jun; Wen, Lei; Yang, Hai-Jun; Zhang, Guang-Ya; Shi, Jun; Peng, Geng-Xin; Hu, Jian-Feng; Luo, Jun-Cheng; Huang, Zhi-Bin; Chen, Yan-Gui; Zhang, Qiang

    2015-02-01

    Late Silurian-Carboniferous extensional structures have been discovered after careful interpretation of seismic reflection data in western Manjiaer Sag, Central Tarim Basin in central Asia. The extensional structures comprise numerous small normal faults in nearly N-S strike direction. Groups of normal faults in profile show features suggestive of negative flower structures and small horst-graben structures. Based on growth index calculation, these extensional structures formed in the Late Silurian period, continued activity in the Devonian and Carboniferous and then ceased at the end of Carboniferous. The peak-stage of normal fault activity occurred in Late Silurian. Late Silurian-Carboniferous normal faults also developed in the Tazhong and Tabei areas, which implies that Tarim Basin were under regional extensional tectonic setting during that periods. The extensional structure in southern Tarim resulted from the post-orogeny stress relaxation of the Kunlun Early Paleozoic orogenic belt, and those in northern Tarim resulted from the Paleozoic back-arc rifting which led to the opening of South Tianshan ocean.

  6. Temporal patterns in southern Aegean seismicity revealed by the multiresolution wavelet analysis

    NASA Astrophysics Data System (ADS)

    Telesca, Luciano; Hloupis, George; Nikolintaga, Irini; Vallianatos, Filippos

    2007-12-01

    We applied multiresolution wavelet analysis to the sequence of times between earthquakes occurred between 1970 and 2003 in the southern Aegean area, one of the most seismically active area in the Mediterranean. We observed a twofold features in the wavelet-coefficient standard deviation σwav: (i) at low scales it decreases in correspondence with the occurrence of the strongest earthquake, mainly due to the aftershock activation mechanism; (ii) at high scales it is characterized by oscillating behaviour, which is a typical background seismicity.

  7. A misleading(?) similarity of indentor corners; Aegean-Anatolia versus the Himalaya syntaxes

    NASA Astrophysics Data System (ADS)

    Edwards, M.; Schneider, D.; Grasemann, B.; Accel, T.

    2006-12-01

    An appealing similarity of indentor corner-type geodynamic features in diffuse plate boundaries can be seen in the comparison of eastern Tibet/Namcha Barwa syntaxis (the termination of the main Himalaya) with the Aegean/Anatolian region (the termination of the easternmost Alpine Belt). Short-timescale measurements (seismological, GPS) show both regions are dynamic tectonic features that punctuate the ends of collisional orogens. Both regions are foci of elevated seismicity and, most strikingly, involve dramatic continental "escape tectonics" that boast some of the globe's highest angular velocities (surface vorticity) for continents that, moreover, have almost mirror-image symmetry. Finally, both regions are the progeny of protracted Tertiary orogenesis and exhume world-class high pressure deep crustal rocks. Beyond here, however, the appealing similarity of these apparent indentor corners ends; the Aegean/Anatolian region owes its exciting modern geodynamics to accelerated subducting slab retreat and, in stark contrast to the India-Asia collision, has limited net plate convergence. Furthermore, the renowned Aegean exhumation owes little to erosion and evacuation of material by intense surface processes, and extreme relief since the Miocene has been largely absent. Our data from Project ACCEL (this meeting) and many other studies highlight that the retreating slab governs displacement velocities for collisional plate boundaries whose lengths are short; most of the presently observed Aegean angular velocity enabled Anatolian escape and is certainly due to rapid slab retreat since at least the Miocene. The orogen preserves other equivalent, now diminished or terminated, examples of accelerated slab retreat such as the Appenines/Calabrian Arc and the Eastern Alps/Carpathians, indicative of the spatial and temporal transience of these slab retreat sites. These features would appear to be short term indentor corners. The indentor corners of the eastern and western

  8. Monitoring seismic velocity changes caused by the 2014 Northern Aegean earthquake using continuous ambient noise records

    NASA Astrophysics Data System (ADS)

    Evangelidis, Christos; Daskalakis, Emmanouil; Tsogka, Chrysoula

    2016-04-01

    The 24 May 2014 Northern Aegean earthquake (6.9 Mw), an event on the Northern Aegean Trough (NAT), ruptured on two different fault segments with a total ruptured length of ~100 km. For the second delayed segment, rupture propagated eastward from the hypocenter for ˜65 km with a supershear velocity (5.5 km/s). Low-aftershock seismicity on the supershear segment implies a simple and linear fault geometry there. An effort to monitor temporal seismic velocity changes across the ruptured area of the Northern Aegean earthquake is underway. In recent years, neighboring seismic broadband stations near active faults have been successfully used to detect such changes. The crosscorrelation functions (CCF) of ambient noise records between stations yields the corresponding traveltimes for those inter-station paths. Moreover, the auto-correlation functions (ACF) at each station produce the seismic responce for a coincident source and receiver position. Possible temporal changes of the measured traveltimes from CCFs and ACFs correspond to seismic velocity changes. Initially, we investigate the characteristics and sources of the ambient seismic noise as recorded at permanent seismic stations installed around NAT at the surrounding islands and in mainland Greece and Turkey. The microseismic noise levels show a clear seasonal variation at all stations. The noise levels across the double frequency band (DF; period range 4-8 s) reflect the local sea-weather conditions within a range of a few hundred kilometers. Three years of continuous seismic records framing the main shock have been analysed from ~15 stations within a radius of 100 km from the epicentre. We observe a clear decrease of seismic velocities most likely corresponding to the co-seismic shaking. The spatial variation of this velocity drop is imaged from all inter-station paths that correspond to CCF measurements and for station sites that correspond to ACF measurements. Thus, we explore a possible correlation between co

  9. Three-dimensional instantaneous dynamics modeling of present-day Aegean subduction

    NASA Astrophysics Data System (ADS)

    Glerum, Anne; Thieulot, Cedric; Pranger, Casper; van Hinsbergen, Douwe; Fraters, Menno; Spakman, Wim

    2015-04-01

    The Aegean region (Eastern Mediterranean) is exemplary of the interaction between crustal tectonics, plate motion, subduction and mantle flow: African subduction underneath the region has been continuous for at least the last 100 My, leading to about 2100-2500 km of subducted lithosphere residing in the mantle (van Hinsbergen et al., 2005). During this subduction, decoupled upper continental and oceanic crust accreted into a wedge of stacked nappes. In turn, these nappes have been significantly extended, predominantly during the last 25 My, due to the retreat of the African slab relative to Eurasia (van Hinsbergen and Schmid, 2012). As a first step to better understanding the coupling of the tectonic evolution of the crust and the underlying mantle dynamics, we are developing 3-D numerical models of the instantaneous dynamics of the present-day Aegean subduction system using the finite element code ASPECT (Kronbichler et al., 2012). The instantaneous models are set up with initial slab geometries derived from tomography and realistic plate boundary configurations and incorporate the major crustal weak zones of the overriding plate. Our modeling results in predictions of flow fields and stress, strain rate and rotation rate fields for the present-day tectonic setting of the Aegean region. By comparing our various model predictions to the widely available observations, such as focal mechanisms, GPS velocities and seismic anisotropy, we aim at an improved understanding of how mantle flow, subduction morphology and possibly slab segmentation, as well as the rheological behavior of the overriding plate, control present-day tectonic deformation. We expect to show preliminary results of this comparison. Kronbichler, M., Heister, T. and Bangerth, W. (2012), High Accuracy Mantle Convection Simulation through Modern Numerical Methods, Geophysical Journal International, 191, 12-29. Van Hinsbergen, D. J. J., Hafkenscheid, E., Spakman, W., Meulenkamp, J. E. and Wortel, R. (2005

  10. Capillary break-up, gelation and extensional rheology of hydrophobically modified cellulose ethers

    NASA Astrophysics Data System (ADS)

    Sharma, Vivek; Haward, Simon; Pessinet, Olivia; Soderlund, Asa; Threlfall-Holmes, Phil; McKinley, Gareth

    2012-02-01

    Cellulose derivatives containing associating hydrophobic groups along their hydrophilic polysaccharide backbone are used extensively in the formulations for inks, water-borne paints, food, nasal sprays, cosmetics, insecticides, fertilizers and bio-assays to control the rheology and processing behavior of multi-component dispersions. These complex dispersions are processed and used over a broad range of shear and extensional rates. The presence of hydrophobic stickers influences the linear and nonlinear rheology of cellulose ether solutions. In this talk, we systematically contrast the difference in the shear and extensional rheology of a cellulose ether: ethy-hydroxyethyl-cellulose (EHEC) and its hydrophobically-modified analog (HMEHEC) using microfluidic shear rheometry at deformation rates up to 10^6 inverse seconds, cross-slot flow extensional rheometry and capillary break-up during jetting as a rheometric technique. Additionally, we provide a constitutive model based on fractional calculus to describe the physical gelation in HMEHEC solutions.

  11. Pinch-off dynamics, extensional viscosity and relaxation time of dilute and ultradilute aqueous polymer solutions

    NASA Astrophysics Data System (ADS)

    Biagioli, Madeleine; Dinic, Jelena; Jimenez, Leidy Nallely; Sharma, Vivek

    Free surface flows and drop formation processes present in printing, jetting, spraying, and coating involve the development of columnar necks that undergo spontaneous surface-tension driven instability, thinning, and pinch-off. Stream-wise velocity gradients that arise within the thinning neck create and extensional flow field, which induces micro-structural changes within complex fluids that contribute elastic stresses, changing the thinning and pinch-off dynamics. In this contribution, we use dripping-onto-substrate (DoS) extensional rheometry technique for visualization and analysis of the pinch-off dynamics of dilute and ultra-dilute aqueous polyethylene oxide (PEO) solutions. Using a range of molecular weights, we study the effect of both elasticity and finite extensibility. Both effective relaxation time and the transient extensional viscosity are found to be strongly concentration-dependent even for highly dilute solutions.

  12. Comparison between extensional rheological properties of low density polyethylene melt in SER and RME rheometric systems

    NASA Astrophysics Data System (ADS)

    Narimissa, Esmaeil; Rolón-Garrido, Víctor Hugo; Wagner, Manfred Hermann

    2015-04-01

    Precise evaluation and notional prediction of extensional rheological behaviour of polymeric melts and solutions are of significant importance in polymer industry. This is evident in the well documentation of the dominance of elongational deformation of polymeric systems in processes such as melt spinning, blow moulding, biaxial stretching of extruded sheets, etc. The relevant commercial extensional rheometers thus far discussed in the literature are RME and SER. This research, for the first time, compares the extensional viscosity measurements of low density polyethylene at 140, 150, and 170 °C through RME and SER devices. Despite the observed similarities found in this comparative investigation, the main difference was laid in maximum Hencky strain, strain hardening viscosity, and the variation of those rheological properties with testing temperature of the samples.

  13. Spatial and temporal relations between coronae and extensional belts, northern Lada Terra, Venus

    NASA Technical Reports Server (NTRS)

    Baer, Gidon; Schubert, Gerald; Bindschadler, Duane L.; Stofan, Ellen R.

    1994-01-01

    Preliminary studies of the distribution of coronae and volcanic rises on Venus show that many of these features tend to cluster along zones of rifting and extension. The plains north of Lada Terra are crossed by two such extensional belts. Each belt is composed of grabens, ridges, faults, volcanic flows, coronae and coronalike features. The longer and more prominent belt is the NW trending Alpha-Lada extensional belt, which is over 6000 km long and 50-200 km wide, and includes the coronae Eve, Tamfana, Carpo, Selu, Derceto, Otygen, and an unnamed corona south of Otygen. The second belt is the NNE trending Derceto-Quetzalpetlatl extensional belt, which is about 2000 km long and in places over 300 km wide, and includes the coronae Sarpanitum, Eithinoha, and Quetzalpetlatl. The two belts intersect at the 1600 x 600 km wide Derceto volcanic plateau. It is apparent that deformation along the two belts overlapped in time, though deformation along the Alpha-Lada extensional belt probably continued after the deformation along the Derceto-Quetzalpetlatl extensional belt terminated. In certain areas, volcanism originated in grabens within the extensional belts, whereas in other areas, such as in Eve, Selu, Derceto, and Quetzalpetlatl, volcanism originated in the coronae and flowed into the lower parts of the extensional belts. Regional extension has affected the evolution of all the coronae at some stage of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha and after the initiation of Carpo, Tamfana, Otygen, and Sarpanitum. It is thus unlikely that coronae formation along the belts is solely a consequence of the regional extension, and it is also unlikely that regional extension has been caused solely by the coronae. No corona along the belts was formed subsequent to the cessation of the regional extension. We therefore suggest that

  14. Spatial and temporal relations between coronae and extensional belts, northern Lada Terra, Venus

    NASA Astrophysics Data System (ADS)

    Baer, G.; Schubert, G.; Bindschadler, D. L.; Stofan, E. R.

    1994-04-01

    Preliminary studies of the distribution of coronae and volcanic rises on Venus show that many of these features tend to cluster along zones of rifting and extension. The plains north of Lada Terra are crossed by two such extensional belts. Each belt is composed of grabens, ridges, faults, volcanic flows, coronae and coronalike features. The longer and more prominent belt is the NW trending Alpha-Lada extensional belt, which is over 6000 km long and 50-200 km wide, and includes the coronae Eve, Tamfana, Carpo, Selu, Derceto, Otygen, and an unnamed corona south of Otygen. The second belt is the NNE trending Derceto-Quetzalpetlatl extensional belt, which is about 2000 km long and in places over 300 km wide, and includes the coronae Sarpanitum, Eithinoha, and Quetzalpetlatl. The two belts intersect at the 1600 x 600 km wide Derceto volcanic plateau. It is apparent that deformation along the two belts overlapped in time, though deformation along the Alpha-Lada extensional belt probably continued after the deformation along the Derceto-Quetzalpetlatl extensional belt terminated. In certain areas, volcanism originated in grabens within the extensional belts, whereas in other areas, such as in Eve, Selu, Derceto, and Quetzalpetlatl, volcanism originated in the coronae and flowed into the lower parts of the extensional belts. Regional extension has affected the evolution of all the coronae at some stage of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha and after the initiation of Carpo, Tamfana, Otygen, and Sarpanitum. It is thus unlikely that coronae formation along the belts is solely a consequence of the regional extension, and it is also unlikely that regional extension has been caused solely by the coronae. No corona along the belts was formed subsequent to the cessation of the regional extension. We therefore suggest that

  15. Volcano-tectonic evolution of the polygenetic Kolumbo submarine volcano/Santorini (Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Hübscher, Christian; Ruhnau, M.; Nomikou, P.

    2015-01-01

    Here we show for the first time the 3D-structural evolution of an explosive submarine volcano by means of reflection seismic interpretation. Four to five vertically stacked circular and cone-shaped units consisting mainly of volcaniclastics build the Kolumbo underwater volcano which experienced its first eruption > 70 ka ago and its last explosive eruption 1650 AD, 7 km NE of Santorini volcano (southern Aegean Sea). The summed volume of volcaniclastics is estimated to range between 13-22 km3. The entire Kolumbo volcanic complex has a height of ≥ 1 km and a diameter of ≥ 11 km. All volcaniclastic units reveal the same transparent reflection pattern strongly suggesting that explosive underwater volcanism was the prevalent process. Growth faults terminate upwards at the base of volcaniclastic units, thus representing a predictor to an eruption phase. Similarities in seismic reflection pattern between Kolumbo and near-by volcanic cones imply that the smaller cones evolved through explosive eruptions as well. Hence, the central Aegean Sea experienced several more explosive eruptions (≥ 23) than previously assumed, thus justifying further risk assessment. However, the eruption columns from the smaller volcanic cones did not reach the air and- consequently - no sub-aerial pyroclastic surge was created. The Anydros basin that hosts Kolumbo volcanic field opened incrementally NW to SE and parallel to the Pliny and Strabo trends during four major tectonic pulses prior to the onset of underwater volcanism.

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

    PubMed Central

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

    2012-01-01

    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

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

    PubMed

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

    2014-01-01

    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.

  18. The Etesian wind system and wind energy potential over the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Dafka, Stella; Xoplaki, Elena; Garcia-Bustamante, Elena; Toreti, Andrea; Zanis, Prodromos; Luterbacher, Juerg

    2013-04-01

    The Mediterranean region lies in an area of great climatic interest since it is influenced by some of the most relevant mechanisms of the global climate system. In the frame of the three Europe 2020 priorities for a smart, sustainable and inclusive economy delivering high levels of employment, productivity and social cohesion, the Mediterranean energy plan is of paramount importance at the European level, being an area with a significant potential for renewable energy from natural sources that could play an important role in responding to climate change effects over the region. We present preliminary results on a study of the Etesian winds in the past, present and future time. We investigate the variability and predictability of the wind field over the Aegean. Statistical downscaling based on several methodologies will be applied (e.g. canonical correlation analysis and multiple linear regression). Instrumental time series, Era-Interim and the 20CR reanalyses will be used. Large-scale climate drivers as well as the influence of local/regional factors and their interaction with the Etesian wind field will be addressed. Finally, the Etesian wind resources on the present and future climate will be assessed in order to identify the potential areas suitable for the establishment of wind farms and the production of wind power in the Aegean Sea.

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

    NASA Astrophysics Data System (ADS)

    Uysal, Zahit

    2006-08-01

    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.

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

    PubMed

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

    2014-01-01

    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

  1. Early Cretaceous extensional reworking of the Triassic HP-UHP metamorphic orogen in Eastern China

    NASA Astrophysics Data System (ADS)

    Lin, Wei; Ji, Wenbin; Faure, Michel; Wu, Lin; Li, Qiuli; Shi, Yonghong; Scharer, Urs; Wang, Fei; Wang, Qingchen

    2015-11-01

    Corresponding to the Early Mesozoic continental subduction between the North China Block (NCB) and the South China Block (SCB), the Tongbaishan-Hong'an-Dabieshan-Sulu massifs are famous for their HP-UHP metamorphism. More than 50% of the HP-UHP Orogenic Belt was significantly reworked by Early Cretaceous extensional tectonics. This Early Cretaceous event with a fast cooling period, at 130-120 Ma, superimposed on the Early Mesozoic HP-UHP orogenic belt and intensively changed the architecture of this orogen. Each individual segment documents different Early Cretaceous extensional structures, namely the central Tongbaishan domain is a metamorphic core complex (MCC) represented by an A-type non-cylindrical antiform; the central Dabieshan domain is a typical Cordilleran-type migmatite-cored MCC; the Southern Sulu UHP domain is a "wedge-shaped" structure exhumed by a simple detachment fault. These late stage extensional structures expose the previous HP-UHP orogenic belt as fragments along the NCB-SCB boundary. The geodynamic setting of this Early Cretaceous extensional tectonics along the HP-UHP orogen is a part of a 1000 km-scale crustal extension belt that is widespread in eastern Eurasia continent from Trans-Baikal to the central part of SCB. Convective erosion or delamination of the mantle lithosphere might be considered as a possible mechanism for mantle removal.

  2. Early Cretaceous extensional reworking of the Triassic HP-UHP metamorphic orogen in Eastern China

    NASA Astrophysics Data System (ADS)

    Lin, W.; Ji, W.; Faure, M.; Wu, L.; Li, Q. L.; Shi, Y.; Scharer, U.; Wang, F.; Wang, Q.

    2015-12-01

    Corresponding to the Early Mesozoic continental subduction between the North China Block (NCB) and the South China Block (SCB), the Tongbaishan-Hong'an-Dabieshan-Sulu massifs are famous for their HP-UHP metamorphism. More than 50% of the HP-UHP Orogenic Belt was significantly reworked by Early Cretaceous extensional tectonics. This Early Cretaceous event with a fast cooling period, at 130-120 Ma, superimposed on the Early Mesozoic HP-UHP orogenic belt and intensively changed the architecture of this orogen. Each individual segment documents different Early Cretaceous extensional structures, namely the central Tongbaishan domain is a metamorphic core complex (MCC) represented by an A-type non-cylindrical antiform; the central Dabieshan domain is a typical Cordilleran-type migmatite-cored MCC; the Southern Sulu UHP domain is a "wedge-shaped" structure exhumed by a simple detachment fault. These late stage extensional structures expose the previous HP-UHP orogenic belt as fragments along the NCB-SCB boundary. The geodynamic setting of this Early Cretaceous extensional tectonics along the HP-UHP orogen is a part of a 1000 km-scale crustal extension belt that is widespread in eastern Eurasia continent from Trans-Baikal to the central part of the South China Block. Convective erosion or delamination of the mantle lithosphere might be considered as a possible mechanism for mantle removal.

  3. Thermal compensation in GaPO4 beam resonators: experimental evidence for length extensional mode.

    PubMed

    Sthal, Fabrice; Bigler, Emmanuel; Bourquin, Roger

    2007-01-01

    Temperature effects in gallium orthophosphate (GaPO4) vibrating beams are reported. In addition to the well-known, thickness-shear AT-cut, temperature-compensated cuts exist in GaPO4 for length extensional modes. Experimental evidence of a temperature-compensated cut in GaPO4 rectangular beam resonator vibrating in length extension is given. PMID:17225814

  4. Particulate and dissolved primary production along a pronounced hydrographic and trophic gradient (Turkish Straits System-NE Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Lagaria, A.; Psarra, S.; Gogou, A.; Tuğrul, S.; Christaki, U.

    2013-06-01

    The rates of particulate (PPp) and dissolved primary production (PPd) were estimated along a trajectory of variable environmental regimes formed in a narrow shelf area, following the course of Black Sea water masses (BSW) passing through the Turkish Straits System (TSS) into the NE Aegean Sea (BS-AS outflow). Seven stations in total were sampled, covering a transect from the eastern edge of the Marmara Sea basin to the NE Aegean Sea, during two consecutive cruises performed in October 2008 within the framework of the EU SESAME project. Along the BS-AS outflow, depth-integrated over the surface BSW layer PPp decreased considerably from 91 to < 16 mg C m- 2 h- 1 whereas PPd increased from 3 to 10 mg C m- 2 h- 1. As a consequence, the relative importance of PPd over total production (percentage extracellular release, PER) increased from 6% (± 3% sd) in the Marmara Sea to 37% (± 4% sd) in the NE Aegean Sea. Total chlorophyll a concentration gradually decreased and phytoplankton community size-structure was modified, with pico-phytoplankton, that originally represented 35% (± 9% sd) in the Marmara Sea, gradually becoming dominant in the NE Aegean (77% ± 2% sd), substituting large nano- and micro-phytoplankton cells (> 5 μm). This study showed that PER increased along a gradient from mesotrophy to oligotrophy, probably due to nutrient deficiency constraining phytoplankton growth and was closely related to phytoplankton size-structure. In the oligotrophic NE Aegean Sea, phytoplankton exudation was a significant source of dissolved organic carbon for heterotrophic prokaryotes.

  5. Tsunami Warning System for the Eastern Mediterranean, Aegean and Black Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Meral Ozel, Nurcan; Kalafat, Dogan; Comoglu, Mustafa; Ozer Sozdinler, Ceren; Yılmazer, Mehmet; Cevdet Yalçıner, Ahmet

    2015-04-01

    Bogazici University - KOERI is providing a Tsunami Warning System to Eastern Mediterranean, Aegean and Black Seas since 1 July 2012 as a Candidate Tsunami Service Provider (CTSP) within the ICG/NEAMTWS Framework. KOERI continues to operate 129 BB and 86 strong motion and 6 short period sensors. The regional coverage includes 77 stations from GFZ and additional 16 stations through bilateral agreements. During 2014, Romania and Russian Federation have subscribed to its services thanks to 2nd Tsunami Exercise of NEAMTWS - NEAMWave14, reaching a total of 11 NEAMTWS Member States as subscribers. No further progress could have been made in 2014 in the integration of the existing national-tide gauge stations due to the updated plans of the General Command of Mapping in charge of the operation of the national tide-gauge network. Collaborative activities with EC-JRC continued where a comprehensive tsunami scenario database for the Eastern Mediterranean, Aegean and Black Seas has been produced. In addition, KOERI also participated in EC-JRCs Global Tsunami Informal Monitoring Service Project and analyzed 16 tsunamigenic events around the globe. CTSP-TR continued to participate in the Communication Test Exercises (CTE) and Regular CTEs (RegCTE), and acted as the Message Provider for the NEAMWave14 Black Sea Scenario, where Black Sea was covered fort he first time in a NEAMTWS Tsunami Exercise. New Operational Centre has been built and full integration is expected in the first half of 2015. Data preparation activities for the inundation maps at TFPs continued. KOERI also continued to improve its TWS through its involvement of EC funded FP-7 Projects ASTARTE and MARSite and currently focuses on a detailed NEAMTWS Performance Monitoring Framework with associated Key Performance Indicators. This presentation provides a status overview of the operational system while focusing on selected events, such as 12 October 2013 Mw 6.6 and 24 May 2014 Mw 6.9 Northern Aegean earthquakes

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

    NASA Astrophysics Data System (ADS)

    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

    2016-02-01

    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

  7. Post-Miocene extension in Central Anatolia; It's linkage to Aegean extension

    NASA Astrophysics Data System (ADS)

    Rojay, Bora; Özsayın, Erman

    2013-04-01

    Post-Miocene extension in Central Anatolia; It's linkage to Aegean extension Anatolian Plate, -where Central Anatolia situated on-, escapes westward onto African plate along Eastern Mediterranean-Cyprus subduction zone, sliding by North and East Anatolian faults. Central Anatolia is bounded by dextral North Anatolian Fault from north, Taurides from south and it is fragmented by strike slip faults evolving under N-S compression in east and by Aegean horst and grabens evolving under N-S extension in west. To be able to delineate and understand the deformational order in Central Anatolia and its linkage to Aegean region, various sectors with the Anatolia are chosen, namely, Ankara region (Beypazarı to Kazan Miocene basins), Eskişehir region (Mihallıçık to İnönü Miocene basins) in Central Anatolia, Gediz-Alaşehir Graben and Efes areas in Western Anatolia are selected. To sum up, in a wide region from Central Anatolia to Western Anatolia, i. Unconformities btw uppermost Late Miocene and Plio-Quaternary, and btw Plio-Quaternary and Quaternary are clearly identified in both regions, ii) ENE-WSW to N-S compression (intense post-Late Miocene - pre-Pliocene folding) with almost E-W extension operates during post-Miocene (during Pliocene) is followed by a short lived strike slip deformation during Early Pliocene, and finally by NW-SE to WNW-ESE oriented multi directional extension during post-Plio-Quaternary. And in Gediz-Alaşehir Graben and Efes (western Anatolia); a continuous NNE-SSW to NE-SW multi directed extension since post-Late Miocene following almost N-S compression (post-Early Miocene) operated. Dextral strike slip faulting with normal components and normal faulting with right lateral strike slip components are recorded on same fault planes, iii) Quaternary normal faulting post dates folding, reverse and strike slip faulting in both regions. However, right lateral strike slip faulting is recorded to the NW tip of the normal faults like Efes, Manisa and

  8. Assessing different turbulence close schemes in the North Aegean: Preliminary results

    NASA Astrophysics Data System (ADS)

    Mamoutos, Ioannis; Zervakis, Vassilis; Tragou, Elina

    2015-04-01

    The North Aegean Sea potentially constitutes one of the deep-water formation sites of the Mediterranean Sea. The production of deep water however is highly controlled by the inflow of Black Sea waters forming a thin insulating surface layer over a large part of the region. For this reason, extensive replenishment of the deeper-than-400 m basins takes place infrequently, at intervals several years long. After the recorded major deep water formation events of 1987, 1992 and 1993, several smaller magnitude formation events have been observed in the 2000s. Long stagnation periods separate successive formation events, during which turbulent exchange through the interface between the deep, secluded locally-formed water mass and the overlaid, laterally flowing water masses is the major factor determining the evolution of the deep-layer properties. In this work we test different diapycnal mixing schemes via comparing the results of long-term hindcasts of the evolution of the deep-layer properties to successive observations in three deep basins of the North Aegean. The Regional Ocean Model System (ROMS) was used for the hindcasts. All the available turbulence closure schemes - KPP, GLS and Mellor - Yamada 2.5 - were used for the experiments. A rectangular grid covering the Aegean sea was developed (longitudinal range: 22.50 E - 28.37 E, latitudinal range: 36.43 N - 41.12 N) with a 1/40 degree ( ~ 2.5 km ) resolution in both directions and 30 vertical sigma layers. The initial and boundary conditions used refer to the 1985 - 2013 period, and have been provided by GNOO. Atmospheric forcing fields from ERA - interim data set were used with spatial resolution 0.5 × 0.5 degrees and three-hour time step. The Black-sea water inflow is temporally variable and has been provided by Vladimir Maderich based on Black and Marmara Sea budgets and hydraulic control at Bosphorus and Dardanelles Straits. The preliminary results of the numerical experiments are hereby presented and discussed

  9. Interaction Between Magmatism and Continental Extension, Insight From an Extensional Terrain in the Iranian Plateau

    NASA Astrophysics Data System (ADS)

    Malekpour Alamdari, A.; Axen, G. J.; Hassanzadeh, J.

    2014-12-01

    Our knowledge about the spatial and temporal relationship between continental extension and its related magmatism is mainly from the western US where removal of a flat subducting slab from under the continent controlled thermal weakening and some extensional collapse. The Iranian plateau, where flat-slab subduction and its subsequent rollback is suggested for the Tertiary magmatic evolution, is an ideal place to see if a similar interaction exists. Between the Late Cretaceous and, at least, the Early Eocene, large-scale continental extension affected the NE Iranian plateau. An ~100 km-long, SE tilted upper to mid-crustal section was exhumed by slip along a low-angle, NW-dipping detachment fault. From SE to NW (young to old) this section includes late Cretaceous pelagic limestones of the Kashmar ophiolites, Late and Early Cretaceous sedimentary rocks, and the Late Triassic and older crystalline rocks of the Biarjmand-Shotor Kuh metamorphic core complex. Little pre-extensional magmatic activity exists in the tilted sequence and in surrounding regions, as Late Jurassic and Early Cretaceous dikes. Similarly, syn-extensional magmatism is absent. In contrast, the tilted sequence is unconformably overlain by >4000 m of volcanic rocks with age ranging from the Middle Eocene (explosive, calc-alkaline?) to the Late Eocene (effusive, alkaline). The absence of considerable pre-extensional magmatism in the NE Iranian plateau does not support magma underplating, subsequent thermal weakening and collapse as a mechanism for the extension in this region. It also indicates that the models that consider waning of volcanism as a controlling mechanism for triggering of extensional faulting (Sonder & Jones, 1999) is not applicable for this region. The amagmatic extension may reflect magma crystallization at depth due to reduced confining pressure resulted from active normal faulting and fracturing (Gans & Bohrson, 1998). The extension and related asthenospheric rise may be developed in

  10. Volcanic history of the Colorado River extensional corridor: Active or passive rifting

    SciTech Connect

    Howard, K.A. )

    1993-04-01

    Magmatism and extension began nearly simultaneously in the Colorado River extensional corridor (CREC) between 34 and 35[degree] N. Initial eruptions of basanite at 23--19.5 Ma were low-volume but spanned a region now twice as wide as the 100-km-wide corridor. Extensional tilting of this age was local. A large flux of calc-alkaline basalt, andesite, dacite, and rhyolite was erupted at 22--18.5 Ma. They accumulated to average thicknesses of [approximately]1 km in the early CREC basin, and were accompanied by extensional tilting. Dike swarms, necks, and plutons represent intrusive equivalents. Plutons concentrate in the central belt of metamorphic core complexes, the most highly extended areas. Massive eruption at 18.5 Ma of the rhyolitic Peach Springs Tuff marked an ensuing lowered rate of volcanic output, a change to bimodal volcanism, much tilting and extension, and deposition of thick (to [approximately]2 km) synextensional clastic sediments 18--14 Ms. By 14--12 Ma, extensional tilting had largely ceased, and eruptions were sparse and basaltic only, as they have been since. Basalt compositions reveal changing patterns of trace-element composition that bear on sources. The early basanites have OIB-like compositions on spidergram plots, suggesting origin from the asthenosphere as would be expected from initiation of rifting driven by hot mantle upwelling. Basalts 20--12 Ma show low concentrations of Nb and Ta as in subduction-related arc magmas. Post-extensional basalts erupted 15--10 Ma exhibit a transition back toward primitive compositions seen in Quaternary alkalic basalts.

  11. Performance of Statistical Temporal Downscaling Techniques of Wind Speed Data Over Aegean Sea

    NASA Astrophysics Data System (ADS)

    Gokhan Guler, Hasan; Baykal, Cuneyt; Ozyurt, Gulizar; Kisacik, Dogan

    2016-04-01

    Wind speed data is a key input for many meteorological and engineering applications. Many institutions provide wind speed data with temporal resolutions ranging from one hour to twenty four hours. Higher temporal resolution is generally required for some applications such as reliable wave hindcasting studies. One solution to generate wind data at high sampling frequencies is to use statistical downscaling techniques to interpolate values of the finer sampling intervals from the available data. In this study, the major aim is to assess temporal downscaling performance of nine statistical interpolation techniques by quantifying the inherent uncertainty due to selection of different techniques. For this purpose, hourly 10-m wind speed data taken from 227 data points over Aegean Sea between 1979 and 2010 having a spatial resolution of approximately 0.3 degrees are analyzed from the National Centers for Environmental Prediction (NCEP) The Climate Forecast System Reanalysis database. Additionally, hourly 10-m wind speed data of two in-situ measurement stations between June, 2014 and June, 2015 are considered to understand effect of dataset properties on the uncertainty generated by interpolation technique. In this study, nine statistical interpolation techniques are selected as w0 (left constant) interpolation, w6 (right constant) interpolation, averaging step function interpolation, linear interpolation, 1D Fast Fourier Transform interpolation, 2nd and 3rd degree Lagrange polynomial interpolation, cubic spline interpolation, piecewise cubic Hermite interpolating polynomials. Original data is down sampled to 6 hours (i.e. wind speeds at 0th, 6th, 12th and 18th hours of each day are selected), then 6 hourly data is temporally downscaled to hourly data (i.e. the wind speeds at each hour between the intervals are computed) using nine interpolation technique, and finally original data is compared with the temporally downscaled data. A penalty point system based on

  12. Distribution of organotin compounds in the bivalves of the Aegean Sea, Greece.

    PubMed

    Chandrinou, S; Stasinakis, A S; Thomaidis, N S; Nikolaou, A; Wegener, J W

    2007-02-01

    Five bivalve species--Mytilus galloprovinciallis (Mediterranean mussels), Venus gallina (stripped venus), Modiola barbatus L. (bearded horse mussels), Pecten jacobeus (scallops) and Callista chione (hard clams)--were collected from seven areas in Aegean Sea, Greece, between August 2001 and January 2003 and analyzed for organotins (OTs). The concentrations (as geometric means) found were 17.1 ng g-1 for tributyltin (TBT), 18.8 ng g-1 for dibutytltin (DBT), 7.8 ng g-1 for monobutyltin (MBT) and 13.0 ng g-1 for triphenyltin (TPhT) (wet weight), which are at similar or lower levels than those reported worldwide. Studying OTs distribution between different bivalve species, lower concentrations were observed in mediterranean mussels, possibly due to their growth in water column (grown on sea net pens in mussel farms), in contrast to the free-ranging species, collected from fishing grounds. Concentrations of the OTs in the examined bivalves varied seasonally. PMID:17067676

  13. Symbiosis of sea anemones and hermit crabs: different resource utilization patterns in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Vafeiadou, Anna-Maria; Antoniadou, Chryssanthi; Chintiroglou, Chariton

    2012-09-01

    The small-scale distribution and resource utilization patterns of hermit crabs living in symbiosis with sea anemones were investigated in the Aegean Sea. Four hermit crab species, occupying shells of nine gastropod species, were found in symbiosis with the sea anemone Calliactis parasitica. Shell resource utilization patterns varied among hermit crabs, with Dardanus species utilizing a wide variety of shells. The size structure of hermit crab populations also affected shell resource utilization, with small-sized individuals inhabiting a larger variety of shells. Sea anemone utilization patterns varied both among hermit crab species and among residence shells, with larger crabs and shells hosting an increased abundance and biomass of C. parasitica. The examined biometric relationships suggested that small-sized crabs carry, proportionally to their weight, heavier shells and increased anemone biomass than larger ones. Exceptions to the above patterns are related either to local resource availability or to other environmental factors.

  14. Model simulation of the drift and spread of the Aegean Sea oil spill near La Coruna

    SciTech Connect

    Daniel, P.

    1994-12-31

    On the 3 December 1992 the Greek oil tanker Aegean Sea ran aground at Torre de Hercules near the entrance to the Ria de Coruna and La Coruna harbor, Spain. The 291 m tanker of 114,036-dwt carrying 79,096 tons of Brent type crude oil, broke up and exploded. Practically all of the oil was released into the sea. Over 200 km of shore was affected. A two-dimensional depth-integrated model on a .25 ft. x .25 ft. grid was implemented with the capability of predicting wind driven movements in the area of La Coruna. It is driven by meteorological analysis from the European Centre for Medium Range Weather Forecasts (ECMRWF) global numerical weather prediction model.

  15. Biodiversity of zoobenthic hard-substrate sublittoral communities in the Eastern Mediterranean (North Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Antoniadou, Chryssanthi; Chintiroglou, Chariton

    2005-03-01

    The spatial dispersion of zoobenthos from sublittoral hard substrate communities in the northern part of the Aegean Sea has been studied during summer 1997 and 1998. Material was collected by SCUBA diving, by totally scraping off five replicate quadrates (400 cm 2 each) at three depth levels (15, 30, 40 m) from six sites located in Chalkidiki peninsula, plus one in Kavala Gulf. The examination of the 19,343 living specimens collected revealed the presence of 314 species. Though the multivariate analyses showed high similarity between stations, the structure of this sciaphilic algal community seems to have an increased spatial heterogeneity. Four distinct facies were recorded in accordance with the occurrence of different algal forms, the degree of hard substrate inclination and the water clarity. A short review on the biodiversity of sublittoral communities in the Mediterranean revealed the affinity between the western and the eastern basin and also among the photophilic and the sciaphilic algal communities.

  16. Macrofauna biodiversity of mussel bed assemblages in Thermaikos Gulf (northern Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Chintiroglou, Chariton-Charles; Damianidis, Panagiotis; Antoniadou, Chryssanthi; Lantzouni, Marina; Vafidis, Dimitris

    2004-02-01

    Biomonitoring of mussel bed assemblages can provide valuable information about the impact of pollution on hard substrate assemblages. This study of Mytilus galloprovincialis mussel beds in Thermaikos Gulf (northern Aegean Sea) deals with the spatial and temporal structure of the associated fauna. Samples were collected and abiotic factors were measured in two successive years. Common biocoenotic methods were employed to analyze the data. The samples could be separated into three groups, with summer and winter samples being clearly different. A total of 100 species were found: polychaetes and crustaceans were the most dominant taxa. The assemblage shows high diversity with respect to species abundance. Biotic interactions within the assemblage appear to influence its composition, although the total evenness remains unaffected in space and time. The M. galloprovincialis assemblages can be found in clean as well as in polluted waters and, therefore, are of great interest in biomonitoring studies.

  17. Progress of KOERI Tsunami Warning System for the Eastern Mediterranean, Aegean and Black Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Meral Ozel, Nurcan; Ozer Sozdinler, Ceren; Yilmazer, Mehmet; Cokacar, Tulay; Comoglu, Mustafa; Pinar, Ali; Kekovali, Kivanc

    2016-04-01

    This presentation provides a progress report on the activities of the Bogazici University / Kandilli Observatory and Earthquake Research Institute - Regional Earthquake and Tsunami Monitoring Center (KOERI-RETMC) which provides services as a Candidate Tsunami Service Provider (CTSP) of ICG/NEAMTWS in the Eastern Mediterranean, Aegean and Black Seas since 1 July 2012. KOERI continues to operate 178 BB and 97 strong motion and 6 short period sensors and the regional coverage includes 77 stations from GFZ and additional 16 stations through bilateral agreements. One radar-type tide-gauge has been installed in Fethiye within the framework of "Inexpensive Device for Sea-Level Measurement" (IDSL) initiative offered as donation by the EC/JRC and planning is in progress for the possible installation of three more IDSLs in selected locations in the Aegean Sea coast of Turkey. The capabilities and the limitations of HF Radar technology for the purpose of tsunami detection in the Eastern Mediterranean has been identified and the maturity and the applicability of these systems for the possible use under the Tsunami Warning System has been determined. The development of the TsuComp as a user-friendly interface to be used in the assessment of tsunamigenic potential and as a single-point entry for message dissemination has been finalized. The work towards the creation of Tsunami Inundation Maps at the Tsunami Forecast Points in Turkey is near finalization. This work is partially funded by project ASTARTE - Assessment, Strategy And Risk Reduction for Tsunamis in Europe - FP7-ENV2013 6.4-3, Grant 603839. The authors would like to thank EC/JRC and Mr. Alessandro Annunziato for their continuous support in the operational activities of RETMC and IDSL initiative.

  18. Centennial-scale paleoceanography during sapropel S1 deposition in the NE Aegean (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Combined micropaleontological and geochemical analyses in the high-sedimentation gravity core M-4G, provided new centennial scale paleoceanographic data for the sapropel S1 deposition in the NE Aegean Sea. Sapropel layer S1a (10.2-8.0 ka) is deposited in dysoxic to oxic bottom waters; sediments are characterized by the high abundance of benthic foraminifers Chilostomella mediterranensis and Globobulimina affinis that are able to tolerate surface sediment and/or pore water oxygen depletion and the presence of the oxic mesotrophic-eutrophic U. mediterranea. Adequate preservation of organic matter is proven by the high organic carbon and loliolide and isololiolide contents, whereas the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. Both alkenone-based SSTs and δO18 G. bulloides records indicate coolings at 8.2 ka (S1a) and at ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7-6.4 ka) is characterized by rather oxic conditions marked by the prominent increase of U. mediterranea. The highly fluctuating SSTs demonstrate repeated coolings and associated dense water formation; major event at 7.4 ka, followed by cold spells at 7.0, 6.8, 6.5 ka. Besides, the increase of algal biomarkers, labile organic matter-feeding foraminifera and eutrophic planktonic species pinpoints rise in in situ marine productivity, which is enhanced by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine organic matter (OM) along with fresher terrestrial OM inputs after ~7.7 ka BP imply alternative/ additional than the north Aegean riverine borderland sources for the influx of organic matter at the south Limnos Basin, also related to the inflow of highly productive Marmara/Black Sea waters

  19. Exploration of the Black, Aegean, and Mediterranean Seas Aboard E/V Nautilus

    NASA Astrophysics Data System (ADS)

    Bell, K. L.; Ballard, R. D.; Brennan, M. L.; Raineault, N. A.; Shank, T. M.; Mayer, L. A.; Roman, C.; Mitchell, G. A.; Coleman, D. F.

    2012-12-01

    In the summer of 2012, the Exploration Vessel (E/V) Nautilus undertook a two-month expedition to the Black, Aegean, and Mediterranean Seas. The primary goal of the Nautilus is to create a focus of international leadership for the development and integration of leading-edge technologies, educational programs, field operations, and public outreach programs for ocean exploration, in partnership with the NOAA Office of Ocean Exploration, National Geographic Society, Office of Naval Research, and corporate partners. To do so, the program uses a complement of deep submergence vehicle systems and telepresence technologies to engage scientists, educators and the public, both at sea and ashore, allowing them to become integral members of the on-board exploration team. When discoveries are made, experts ashore are notified and brought aboard virtually within a short period of time to help guide shipboard response before the ship moves on. The 2012 expedition is comprised of four areas of interest. Extensive sidescan mapping took place off the Turkish coasts of the southern Black Sea and eastern Aegean Sea, and was followed by remotely operated vehicle (ROV) dives on targets of archaeological, geological, and biological interest. In the Black Sea, additional work was done on the porewater chemistry of the sediments in the oxic, suboxic, and anoxic zones. Nautilus returned to the Anaximander Seamounts, including Kazan, Amserdam, Thessaloniki, and Athina, to further explore active and formerly active seep sites located in 2010. Finally, based on biological and geological discoveries made on Eratosthenes Seamount in the eastern Mediterranean Sea, we returned to further study chemosynthetic vent communities and tectonic processes.;

  20. A Miocene onset of the modern extensional regime in the Isparta Angle: constraints from the Yalvaç Basin (southwest Turkey)

    NASA Astrophysics Data System (ADS)

    Koç, Ayten; Kaymakci, Nuretdin; van Hinsbergen, Douwe J. J.; Vissers, Reinoud L. M.

    2016-01-01

    The pre-Neogene Tauride fold-and-thrust belt, comprising Cretaceous ophiolites and metamorphic rocks and non-metamorphic carbonate thrust slices in southern Turkey, is flanked and overlain by Neogene sedimentary basins. These include poorly studied intra-montane basins including the Yalvaç Basin. In this paper, we study the stratigraphy, sedimentology and structure of the Yalvaç Basin, which has a Middle Miocene and younger stratigraphy. Our results show that the basin formed as a result of multi-directional extension, with NE-SW to E-W extension dominating over subordinate NW-SE to N-S extension. We show that faults bounding the modern basin also governed basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocentre. The Yalvac Basin was a local basin, but a similar, contemporaneous history recently reconstructed from the Altınapa Basin, ~100 km to the south, shows that multi-directional extension dominated by E-W extension was a regional phenomenon. Extension is still active today, and we conclude that this tectonic regime in the study area has prevailed since Middle Miocene times. Previously documented E-W shortening in the Isparta Angle along the Aksu Thrust, ~100 km to the southwest of our study area, is synchronous with the extensional history documented here, and E-W extension to its east shows that Anatolian westwards push is likely not the cause. Synchronous E-W shortening in the heart and E-W extension in the east of the Isparta Angle may be explained by an eastwards-dipping subduction zone previously documented with seismic tomography and earthquake hypocentres. We suggest that this slab surfaces along the Aksu thrust and creates E-W overriding plate extension in the east of the Isparta Angle. Neogene and modern Anatolian geodynamics may thus have been driven by an Aegean, Antalya and Cyprus slab segment that each had their own specific evolution.

  1. Food-web traits of the North Aegean Sea ecosystem (Eastern Mediterranean) and comparison with other Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Tsagarakis, K.; Coll, M.; Giannoulaki, M.; Somarakis, S.; Papaconstantinou, C.; Machias, A.

    2010-06-01

    A mass-balance trophic model was built to describe the food-web traits of the North Aegean Sea (Strymonikos Gulf and Thracian Sea, Greece, Eastern Mediterranean) during the mid-2000s and to explore the impacts of fishing. This is the first food-web model representing the Aegean Sea, and results were presented and discussed in comparison to other previous ecosystems modelled from the western and the central areas of the basin (South Catalan and North-Central Adriatic Seas). Forty functional groups were defined, covering the entire trophic spectrum from lower to higher trophic levels. Emphasis was placed on commercial invertebrates and fish. The potential ecological role of the invasive ctenophore, Mnemiopsis leidyi, and several vulnerable groups (e.g., dolphins) was also explored. Results confirmed the spatial productivity patterns known for the Mediterranean Sea showing, for example, that the total biomass is highest in N.C. Adriatic and lowest in N. Aegean Sea. Accordingly, food-web flows and several ecosystem indicators like the mean transfer efficiency were influenced by these patterns. Nevertheless, all three systems shared some common features evidencing similarities of Mediterranean Sea ecosystems such as dominance of the pelagic fraction in terms of flows and strong benthic-pelagic coupling of zooplankton and benthic invertebrates through detritus. The importance of detritus highlighted the role of the microbial food-web, which was indirectly considered through detritus dynamics. Ciliates, mesozooplankton and several benthic invertebrate groups were shown as important elements of the ecosystem linking primary producers and detritus with higher trophic levels in the N. Aegean Sea. Adult anchovy was shown as the most important fish group in terms of production, consumption and overall effect on the rest of the ecological groups in the model, in line with results from the Western Mediterranean Sea. The five fishing fleets considered (both artisanal and

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

    NASA Astrophysics Data System (ADS)

    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

    2016-04-01

    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

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

    NASA Astrophysics Data System (ADS)

    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

    2016-03-01

    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

  4. Extensional tectonics, halokinesis, eustacy in the Norwegian Central Graben, North Sea: A testing ground for sequence and seismic stratigraphic principles

    SciTech Connect

    Spencer, P.A.; Prosser, S.D.

    1996-12-31

    The Norwegian Central Graben is a mature hydrocarbon province with proven reserves within the Upper Jurassic succession. Several phases of extensional tectonics ranging from the Permo-Triassic to the Upper Jurassic, and a thick mobile salt section, serve to complicate a clear regional understanding of the area. A full integration of structural interpretation, seismic and sequence stratigraphic principles, biostratigraphy and core studies is required to achieve a realistic interpretation and predict Upper Jurassic facies distributions within this complex area. Utilizing some 30 wells, regional seismic data and biostratigraphy, candidate sequence boundaries and regionally correlatable flooding surfaces (e.g. Eudoxus), have been identified. Horizon flattening on these surfaces has allowed the recognition of thickening-away reflection geometries adjacent to salt features and divergent geometries into graben boundary faults. This facilitates the identification of the dominant local or regional controls on accommodation space creation. Detailed seismic facies analysis was then used to reveal the relative expansion or suppression of depositional systems tracts as a response to either regional or local structural controls. It was subsequently possible to place these systems within a biostratigraphically constrained regional framework. Mapping the base Zechstein, base Jurassic and base Cretaceous horizons has provided a map view of the active faults and slopes controlling sediment transport at any given time. This provided the third dimension essential in depicting the spatial distribution of depositional systems, and is a crucial component of any sequence stratigraphic interpretation. A regional picture of the progressive evolution of this complex area has been thus been derived, and the effect of both regional and local controls on sequence stratigraphic expressions has been determined.

  5. Extensional tectonics, halokinesis, eustacy in the Norwegian Central Graben, North Sea: A testing ground for sequence and seismic stratigraphic principles

    SciTech Connect

    Spencer, P.A. ); Prosser, S.D. )

    1996-01-01

    The Norwegian Central Graben is a mature hydrocarbon province with proven reserves within the Upper Jurassic succession. Several phases of extensional tectonics ranging from the Permo-Triassic to the Upper Jurassic, and a thick mobile salt section, serve to complicate a clear regional understanding of the area. A full integration of structural interpretation, seismic and sequence stratigraphic principles, biostratigraphy and core studies is required to achieve a realistic interpretation and predict Upper Jurassic facies distributions within this complex area. Utilizing some 30 wells, regional seismic data and biostratigraphy, candidate sequence boundaries and regionally correlatable flooding surfaces (e.g. Eudoxus), have been identified. Horizon flattening on these surfaces has allowed the recognition of thickening-away reflection geometries adjacent to salt features and divergent geometries into graben boundary faults. This facilitates the identification of the dominant local or regional controls on accommodation space creation. Detailed seismic facies analysis was then used to reveal the relative expansion or suppression of depositional systems tracts as a response to either regional or local structural controls. It was subsequently possible to place these systems within a biostratigraphically constrained regional framework. Mapping the base Zechstein, base Jurassic and base Cretaceous horizons has provided a map view of the active faults and slopes controlling sediment transport at any given time. This provided the third dimension essential in depicting the spatial distribution of depositional systems, and is a crucial component of any sequence stratigraphic interpretation. A regional picture of the progressive evolution of this complex area has been thus been derived, and the effect of both regional and local controls on sequence stratigraphic expressions has been determined.

  6. Age-dependent modes of extensional necking instability in soft glassy materials.

    PubMed

    Hoyle, David M; Fielding, Suzanne M

    2015-04-17

    We study the instability to necking of an initially cylindrical filament of soft glassy material subject to extensional stretching. By numerical simulation of the soft glassy rheology model and a simplified fluidity model, and by analytical predictions within a highly generic toy description, we show that the mode of instability is set by the age of the sample relative to the inverse of the applied extensional strain rate. Young samples neck gradually via a liquidlike mode, the onset of which is determined by both the elastic loading and plastic relaxation terms in the stress constitutive equation. Older samples fail at smaller draw ratios via a more rapid mode, the onset of which is determined only by the solidlike elastic loading terms (though plastic effects arise later, once appreciable necking develops). We show this solidlike mode to be the counterpart, for elastoplastic materials, of the Considère mode of necking in strain-rate-independent solids. PMID:25933343

  7. Planar Extensional Viscosity of Polystyrene and Polystyrene/CO2 Solution

    NASA Astrophysics Data System (ADS)

    Wang, Jing; James, David F.; Park, Chul B.

    2008-07-01

    The planar extensional viscosity of foaming-grade polystyrene, with and without blowing agent, was determined using a die consisting of a high-aspect-ratio straight rectangular channel followed by a hyperbolic convergent rectangular channel. With the hyperbolic geometry, the fluid near the centerline of the convergent channel was subjected to a constant rate of extension. The shear viscosity was found from the pressure drop along the straight channel, and the planar extensional viscosity was determined from the total pressure drop in the convergent channel minus the calculated pressure drop due to shearing. Two materials, polystyrene and a solution of 5% supercritical carbon dioxide in polystyrene, were tested using a tandem extrusion system and a high-resolution gas pump. Values of the planar Trouton ratio are presented.

  8. Prediction of cryogenic cavitation around hydrofoil by an extensional Schnerr-Sauer cavitation model

    NASA Astrophysics Data System (ADS)

    Sun, T. Z.; Wei, Y. J.; Wang, C.

    2015-12-01

    Developing a robust computational strategy to address the rich physics characteristic involved in the thermodynamic effects on the cryogenic cavitation remains a challenging problem. The objective of this present study is to model the numerical methodology to simulate the cryogenic cavitation by implanting the thermodynamic effects to the Schnerr-Sauer cavitation model, and coupling the energy equation considered the latent heat. For this purpose, cavitating flows are investigated over a three dimensional hydrofoil in liquid hydrogen and nitrogen. Experimental measurements of pressure and temperature are utilized to validate the extensional Schnerr-Sauer cavitation model. Specifically, the further analysis of the cavitation solution with respect to the thermodynamic term is conducted. The results show that the extensional Schnerr-Sauer cavitation model predicts better accuracy to the quasi-steady cavitation over hydrofoil in the two cryogenic fluids.

  9. Extensional flow of hyaluronic acid solutions in an optimized microfluidic cross-slot devicea

    PubMed Central

    Haward, S. J.; Jaishankar, A.; Oliveira, M. S. N.; Alves, M. A.; McKinley, G. H.

    2013-01-01

    We utilize a recently developed microfluidic device, the Optimized Shape Cross-slot Extensional Rheometer (OSCER), to study the elongational flow behavior and rheological properties of hyaluronic acid (HA) solutions representative of the synovial fluid (SF) found in the knee joint. The OSCER geometry is a stagnation point device that imposes a planar extensional flow with a homogenous extension rate over a significant length of the inlet and outlet channel axes. Due to the compressive nature of the flow generated along the inlet channels, and the planar elongational flow along the outlet channels, the flow field in the OSCER device can also be considered as representative of the flow field that arises between compressing articular cartilage layers of the knee joints during running or jumping movements. Full-field birefringence microscopy measurements demonstrate a high degree of localized macromolecular orientation along streamlines passing close to the stagnation point of the OSCER device, while micro-particle image velocimetry is used to quantify the flow kinematics. The stress-optical rule is used to assess the local extensional viscosity in the elongating fluid elements as a function of the measured deformation rate. The large limiting values of the dimensionless Trouton ratio, Tr ∼ O(50), demonstrate that these fluids are highly extensional-thickening, providing a clear mechanism for the load-dampening properties of SF. The results also indicate the potential for utilizing the OSCER in screening of physiological SF samples, which will lead to improved understanding of, and therapies for, disease progression in arthritis sufferers. PMID:24738010

  10. Extensional flow of hyaluronic acid solutions in an optimized microfluidic cross-slot device.

    PubMed

    Haward, S J; Jaishankar, A; Oliveira, M S N; Alves, M A; McKinley, G H

    2013-07-01

    We utilize a recently developed microfluidic device, the Optimized Shape Cross-slot Extensional Rheometer (OSCER), to study the elongational flow behavior and rheological properties of hyaluronic acid (HA) solutions representative of the synovial fluid (SF) found in the knee joint. The OSCER geometry is a stagnation point device that imposes a planar extensional flow with a homogenous extension rate over a significant length of the inlet and outlet channel axes. Due to the compressive nature of the flow generated along the inlet channels, and the planar elongational flow along the outlet channels, the flow field in the OSCER device can also be considered as representative of the flow field that arises between compressing articular cartilage layers of the knee joints during running or jumping movements. Full-field birefringence microscopy measurements demonstrate a high degree of localized macromolecular orientation along streamlines passing close to the stagnation point of the OSCER device, while micro-particle image velocimetry is used to quantify the flow kinematics. The stress-optical rule is used to assess the local extensional viscosity in the elongating fluid elements as a function of the measured deformation rate. The large limiting values of the dimensionless Trouton ratio, Tr ∼ O(50), demonstrate that these fluids are highly extensional-thickening, providing a clear mechanism for the load-dampening properties of SF. The results also indicate the potential for utilizing the OSCER in screening of physiological SF samples, which will lead to improved understanding of, and therapies for, disease progression in arthritis sufferers.

  11. Propagation of Long Extensional Nonlinear Waves in a Hyper-Elastic Layer

    NASA Astrophysics Data System (ADS)

    Teymür, Mevlüt

    Propagation of small but finite amplitude waves in a nonlinear hyper-elastic plate of uniform thickness is considered. By employing a perturbation expansion, extensional waves are examined under the long wave limit. It is shown that the asymptotic wave field is governed by a Korteweg-DeVries (K-dV) equation. Then the propagation characteristics of the asymptotic waves are discussed via the well known solutions of the K-dV equation.

  12. The Miocene to Pleistocene filling of a mature extensional basin in Trans-Pecos Texas: geomorphic and hydrologic controls on deposition

    NASA Astrophysics Data System (ADS)

    Langford, Richard P.; Jackson, Mary L. W.; Whitelaw, Mick J.

    1999-10-01

    Northwest Eagle Flat Basin, in Trans-Pecos (West) Texas, is a Late Tertiary-Quaternary extensional basin in the Basin and Range Province. The basin has largely filled with sediment, so that bedrock uplands only crop out around its rim. Movement on normal faults has effectively ceased, and the geomorphology and deposition differ from active extensional basins, where tectonism is the primary control on basin evolution. Eagle Flat differs from typical extensional basins because progressive changes in basin morphology caused by the aggrading basin-fill were the principal controls on sedimentation. A low-gradient alluvial basin floor expanded to cover the former, fault-defined basin margins. The playa lies on what was upland through the Miocene and Early Pliocene. Only the upper few meters of basin-fill crop out; however, a suite of 88 cores was drilled in the southern part of the basin. Nine of the cores and one trench were sampled for paleomagnetic reversal dating. Correlating the dated cores with interspersed cores allowed us to piece together the basin filling-history and explain how the mature features developed. The cores record the gradual burial of the southern half of the basin. The oldest basin-fill strata were cored in the deepest part of the basin, 219 m below the surface, at ˜12 Ma, in the Miocene. After deposition of 50 m of alluvial-fan gravel along the trend of an inferred normal fault, the basin floor aggraded and expanded. By the 780-ka Brunhes-Matuyama reversal, basin-floor drainage had reversed and was from the north. Sediment accumulation ended during the mid-Pleistocene. A fine-grained sediment supply that did not decrease, and outpaced subsidence was the primary control on basin deposition. This caused a progressive loss of relief and drainage-basin area as uplands were buried under the aggrading basin sediments. After the basin-margin faults were buried, the shape of the basin and its filling-history were little controlled by the original

  13. The rheology of aqueous solutions of ethyl hydroxy-ethyl cellulose (EHEC) and its hydrophobically modified analogue (hmEHEC): extensional flow response in capillary break-up, jetting (ROJER) and in a cross-slot extensional rheometer.

    PubMed

    Sharma, Vivek; Haward, Simon J; Serdy, James; Keshavarz, Bavand; Soderlund, Asa; Threlfall-Holmes, Phil; McKinley, Gareth H

    2015-04-28

    Cellulose derivatives containing associating hydrophobic groups along their hydrophilic backbone are used as rheology modifiers in the formulation of water-based spray paints, medicinal sprays, cosmetics and printable inks. Jetting and spraying applications of these materials involve progressive thinning and break-up of a fluid column or sheet into drops. Strong extensional kinematics develop in the thinning fluid neck. In viscous Newtonian fluids, inertial and viscous stresses oppose the surface tension-driven instability. In aqueous solutions of polymers such as Ethyl Hydroxy-Ethyl Cellulose (EHEC), chain elongation provides additional elastic stresses that can delay the capillary-driven pinch-off, influencing the sprayability or jettability of the complex fluid. In this study, we quantify the transient response of thinning filaments of cellulose ether solutions to extensional flows in a Capillary Break-up Extensional Rheometer (CaBER) and in a forced jet undergoing break-up using Rayleigh Ohnesorge Jetting Extensional Rheometry (ROJER). We also characterize the steady state molecular deformations using measurements of the flow-induced birefringence and excess pressure drop in an extensional stagnation point flow using a Cross-Slot Extensional Rheometer (CSER). We show that under the high extension rates encountered in jetting and spraying, the semi-dilute solutions of hydrophobically modified ethyl hydroxy-ethyl cellulose (hmEHEC) exhibit extensional thinning, while the unmodified bare chains of EHEC display an increase in extensional viscosity, up to a plateau value. For both EHEC and hmEHEC dispersions, the low extensibility of the cellulose derivatives limits the Trouton ratio observed at the highest extension rates attained (close to 10(5) s(-1)) to around 10-20. The reduction in extensional viscosity with increasing extension rate for the hydrophobically modified cellulose ether is primarily caused by the disruption of a transient elastic network that is

  14. The rheology of aqueous solutions of ethyl hydroxy-ethyl cellulose (EHEC) and its hydrophobically modified analogue (hmEHEC): extensional flow response in capillary break-up, jetting (ROJER) and in a cross-slot extensional rheometer.

    PubMed

    Sharma, Vivek; Haward, Simon J; Serdy, James; Keshavarz, Bavand; Soderlund, Asa; Threlfall-Holmes, Phil; McKinley, Gareth H

    2015-04-28

    Cellulose derivatives containing associating hydrophobic groups along their hydrophilic backbone are used as rheology modifiers in the formulation of water-based spray paints, medicinal sprays, cosmetics and printable inks. Jetting and spraying applications of these materials involve progressive thinning and break-up of a fluid column or sheet into drops. Strong extensional kinematics develop in the thinning fluid neck. In viscous Newtonian fluids, inertial and viscous stresses oppose the surface tension-driven instability. In aqueous solutions of polymers such as Ethyl Hydroxy-Ethyl Cellulose (EHEC), chain elongation provides additional elastic stresses that can delay the capillary-driven pinch-off, influencing the sprayability or jettability of the complex fluid. In this study, we quantify the transient response of thinning filaments of cellulose ether solutions to extensional flows in a Capillary Break-up Extensional Rheometer (CaBER) and in a forced jet undergoing break-up using Rayleigh Ohnesorge Jetting Extensional Rheometry (ROJER). We also characterize the steady state molecular deformations using measurements of the flow-induced birefringence and excess pressure drop in an extensional stagnation point flow using a Cross-Slot Extensional Rheometer (CSER). We show that under the high extension rates encountered in jetting and spraying, the semi-dilute solutions of hydrophobically modified ethyl hydroxy-ethyl cellulose (hmEHEC) exhibit extensional thinning, while the unmodified bare chains of EHEC display an increase in extensional viscosity, up to a plateau value. For both EHEC and hmEHEC dispersions, the low extensibility of the cellulose derivatives limits the Trouton ratio observed at the highest extension rates attained (close to 10(5) s(-1)) to around 10-20. The reduction in extensional viscosity with increasing extension rate for the hydrophobically modified cellulose ether is primarily caused by the disruption of a transient elastic network that is

  15. Considering too few alternatives: The mental model theory of extensional reasoning.

    PubMed

    Chevalley, Thierry; Schaeken, Walter

    2016-01-01

    When solving a simple probabilistic problem, people tend to build an incomplete mental representation. We observe this pattern in responses to probabilistic problems over a set of premises using the conjunction, disjunction, and conditional propositional connectives. The mental model theory of extensional reasoning explains this bias towards underestimating the number of possibilities: In reckoning with different interpretations of the premises (logical rules, mental model theoretical, and, specific to conditional premises, conjunction and biconditional interpretation) the mental model theory accounts for the majority of observations. Different interpretations of a premise result in a build-up of mental models that are often incomplete. These mental models are processed using either an extensional strategy relying on proportions amongst models, or a conflict monitoring strategy. The consequence of considering too few possibilities is an erroneous probability estimate akin to that faced by decision makers who fail to generate and consider all alternatives, a characteristic of bounded rationality. We compare our results to the results published by Johnson-Laird, Legrenzi, Girotto, Legrenzi, and Caverni [Johnson-Laird, P., Legrenzi, P., Girotto, V., Legrenzi, M., & Caverni, J. (1999). Naive probability: A mental model theory of extensional reasoning. Psychological Review, 106, 62-88. doi: 10. 1037/0033-295X.106.1.62], and we observe lower performance levels than those in the original article. PMID:26046814

  16. Radioactivity and metal concentrations in marine sediments associated with mining activities in Ierissos Gulf, North Aegean Sea, Greece.

    PubMed

    Pappa, F K; Tsabaris, C; Ioannidou, A; Patiris, D L; Kaberi, H; Pashalidis, I; Eleftheriou, G; Androulakaki, E G; Vlastou, R

    2016-10-01

    Marine sediment samples were collected from Ierissos Gulf, N Aegean Sea, close to the coastal mining facilities. Measurements of radionuclide and metal concentrations, mineral composition and grain size distribution were performed. The concentrations of (226)Ra, (235)U and trace metals showed enhanced values in the port of Stratoni compared with those obtained near to Ierissos port. The dose rates received by marine biota were also calculated by the ERICA Assessment Tool and the results indicated no significant radiological risk. PMID:27474903

  17. Evolutionary processes in a continental island system: molecular phylogeography of the Aegean Nigella arvensis alliance (Ranunculaceae) inferred from chloroplast DNA.

    PubMed

    Bittkau, C; Comes, H P

    2005-11-01

    Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of past fragmentation, dispersal, and genetic drift on taxon diversification. We used phylogeographical (nested clade) and population genetic analyses to elucidate the relative roles of these processes in the evolutionary history of the Aegean Nigella arvensis alliance (= 'coenospecies'). We surveyed chloroplast DNA (cpDNA) variation in 455 individuals from 47 populations (nine taxa) of the alliance throughout its core range in the Aegean Archipelago and surrounding mainland areas of Greece and Turkey. The study revealed the presence of three major lineages, with largely nonoverlapping distributions in the Western, Central, and Eastern Aegean. There is evidence supporting the idea that these major lineages evolved in situ from a widespread (pan-Aegean) ancestral stock as a result of multiple fragmentation events, possibly due to the influence of post-Messinian sea flooding, Pleistocene eustatic changes and corresponding climate fluctuations. Over-sea dispersal and founder events appear to have played a rather insignificant role in the group's history. Rather, all analytical approaches identified the alliance as an organism group with poor seed dispersal capabilities and a susceptibility to genetic drift. In particular, we inferred that the observed level of cpDNA differentiation between Kikladian island populations of Nigella degenii largely reflects population history, (viz. Holocene island fragmentation) and genetic drift in the near absence of seed flow since their time of common ancestry. Overall, our cpDNA data for the N. arvensis alliance in general, and N. degenii in particular, indicate that historical events were important in determining the phylogeographical patterns seen, and that genetic drift has historically been relatively more influential on population structure than has cytoplasmic gene flow.

  18. Towards an absolute chronology for the Aegean iron age: new radiocarbon dates from Lefkandi, Kalapodi and Corinth.

    PubMed

    Toffolo, Michael B; Fantalkin, Alexander; Lemos, Irene S; Felsch, Rainer C S; Niemeier, Wolf-Dietrich; Sanders, Guy D R; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8(th) century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11(th) century BCE according to the Conventional Aegean Chronology and in the late 12(th) century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11(th) century BCE. PMID:24386150

  19. Towards an Absolute Chronology for the Aegean Iron Age: New Radiocarbon Dates from Lefkandi, Kalapodi and Corinth

    PubMed Central

    Toffolo, Michael B.; Fantalkin, Alexander; Lemos, Irene S.; Felsch, Rainer C. S.; Niemeier, Wolf-Dietrich; Sanders, Guy D. R.; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8th century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11th century BCE according to the Conventional Aegean Chronology and in the late 12th century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11th century BCE. PMID:24386150

  20. Focal mechanism determinations of earthquakes along the North Anatolian fault, beneath the Sea of Marmara and the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Nakano, Masaru; Citak, Seckin; Kalafat, Doğan

    2015-09-01

    We determined the centroid moment tensor (CMT) solutions of earthquakes that occurred along the North Anatolian fault (NAF) beneath the Sea of Marmara and the Aegean Sea, using data obtained from Turkey's broad-band seismograph network. The CMT solution of the 2014 Aegean Sea earthquake ( Mw 6.9) represents a strike-slip fault, consistent with the geometry of the NAF, and the source-time function indicates that this event comprised several distinct subevents. Each subevent is considered to have ruptured a different fault segment. This observation indicates the existence of a mechanical barrier, namely a NAF segment boundary, at the hypocenter. CMT solutions of background seismicity beneath the Aegean Sea represent strike-slip or normal faulting along the NAF or its branch faults. The tensional axes of these events are oriented northeast-southwest, indicating a transtensional tectonic regime. Beneath the Sea of Marmara, the CMT solutions represent mostly strike-slip faulting, consistent with the motion of the NAF, but we identified a normal fault event with a tensional axis parallel to the strike of the NAF. This mechanism indicates that a pull-apart basin, marking a segment boundary of the NAF, is developing there. Because ruptures of a fault system and large earthquake magnitudes are strongly controlled by the fault system geometry and fault length, mapping fault segments along NAF can help to improve the accuracy of scenarios developed for future disastrous earthquakes in the Marmara region.

  1. Towards an absolute chronology for the Aegean iron age: new radiocarbon dates from Lefkandi, Kalapodi and Corinth.

    PubMed

    Toffolo, Michael B; Fantalkin, Alexander; Lemos, Irene S; Felsch, Rainer C S; Niemeier, Wolf-Dietrich; Sanders, Guy D R; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8(th) century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11(th) century BCE according to the Conventional Aegean Chronology and in the late 12(th) century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11(th) century BCE.

  2. Aliphatic hydrocarbon levels in turbot and salmon farmed close to the site of the Aegean Sea oil spill

    SciTech Connect

    Alvarez Pineiro, M.E.; Gonzalez-Barros, S.T.C.; Lozano, J.S.

    1996-12-31

    After the Andros Patria oil spill, the most serious oil tanker accident to occur off the coast of Galicia (N.W. Spain) was the running aground and subsequent conflagration of the Aegean Sea supertanker outside the northern Spanish port of La Coruna (December 3rd 1992). Approximately 60,000 tonnes of Brent oil were spilled into the Atlantic Ocean in the cited coastal region. Subsequently, an impropitious combination of a high tide and a change in wind direction caused the resulting slick to rapidly spread into the port. Measures aimed at cleaning up affected areas and evacuating the ca. 11,215 tonnes of oil remaining in the supertanker were immediately implemented. However, within just a few days the resulting contamination had killed some 15000 turbot juveniles and larvae, which are cultivated in fish farms close to the accident site. The environmental impact of major oil spillages has been widely studied. Several scientists have suggested that, in terms of the negative effects on the seawater quality and productive capacity of the affected maritime regions, the magnitudes of the Aegean Sea and Amoco Cadiz accidents are comparable. This paper reports variations over time of aliphatic hydrocarbon levels in turbot and Atlantic salmon sampled from fish farms close to the site of the Aegean Sea oil spill. 6 refs., 2 figs., 1 tab.

  3. Measurement of extensional viscosity using the falling drop technique. Final report, October 27, 1992--September 27, 1996

    SciTech Connect

    Jones, D.K.; Wildman, D.J. |

    1998-02-01

    In the falling drop technique, a drop is formed by slowly extruding a liquid downward through a small tube. The drop eventually falls, and fluid adheres to both the tube and the drop, creating a distinct extending fiber. Extensional viscosity may be determined by measuring the dimensions of the fiber as it extends. The flow of fluid in a falling drop has been modeled in order to determine extensional viscosity by measuring the extending fiber. A falling drop rheometer was built, and fiber dimensions were measured using two digital cameras and an image processing system. Extensional viscosity was measured for various solutions of glycerol, xanthan gum, and water. The falling drop technique proved to be an effective extensional rheometer for a range of solution concentrations. 6 refs., 3 figs., 1 tab.

  4. Eocene extensional exhumation of basement and arc rocks along southwesternmost Peru, Central Andes.

    NASA Astrophysics Data System (ADS)

    Noury, Mélanie; Bernet, Matthias; Sempéré, Thierry

    2014-05-01

    The overthickened crust of the current Central Andes is commonly viewed as the result of tectonic shortening. However, in the present-day terrestrial forearc and arc of southwesternmost Peru, crustal thickness increases from 30 km along the coastline to >60 km below the active arc, whereas the upper crust exhibits little to no evidence of crustal shortening and, in constrast, many extensional features. How (and when) crustal overthickness was acquired in this region is thus little understood. Because crustal overthickening often results in extensional collapse and/or significant erosion, here we address this issue through a regional-scale study of exhumation using fission-track thermochronology. The limited fission-track data previously available in the area suggested that exhumation began during the Mesozoic. In this study, we present new apatite and zircon fission-track data obtained along the current terrestrial forearc of southwesternmost Peru. This relatively restricted area presents the interest of providing extensive outcrops of Precambrian to Ordovician basement and Early Jurassic to Late Cretaceous arc plutons. In order to compare the chronology of exhumation of these units, we performed extensive sampling for fission-track dating, as well as structural mapping. Our results indicate that the basement rocks and Jurassic plutons that crop out in the Arequipa region, where the crust is now >50 km-thick, experienced a rapid cooling through the 240-110°C temperature range between ~65 and ~35 Ma. This period of rapid exhumation coincided in time with the accumulation of terrestrial forearc deposits (the Lower Moquegua Group), that exhibit many syn-sedimentary extensional features and are bounded by conspicuous normal faults, specifically along the region where intense activity of the main arc between ~90 and ~60 Ma had led to voluminous magma emplacement. This close succession of (1) intense magmatic activity and (2) regional-scale exhumation associated with

  5. Backstripping differentiation to detect primary geochemical trends along the Aegean arc

    NASA Astrophysics Data System (ADS)

    Elburg, Marlina; Smet, Ingrid

    2014-05-01

    The present active volcanic arc in the Aegean runs from the centre of Methana in the west through Santorini to Nisyros in the east. The arc is built on (stretched) continental crust of African derivation. None of the analysed whole-rock samples, either from literature or our own data set, is primary, based on a combination of Mg-number, Ni- or Cr-contents. Although samples with (moderately) high values for one or the other exist, they appear to be influenced by magma mixing processes. Therefore, any along-arc trends observed potentially suffer from the effects of crystal fractionation with or without mixing and crustal contamination, obscuring along-arc differences related to varying inputs into the sub-arc mantle. Simple graphical extrapolation to more primitive compositions on variation diagrams is one way to strip the effects of the combination of differentiation processes. The main problem with this approach is the assumption that the observed variation is a faithful representation of all differentiation processes that acted on the primary magma. It is therefore unlikely to work if magma mixing is the process dominating the observed variation, as is the case for Methana. Moreover, it is possible that the first stage of differentiation, modifying the primary magma, is different in nature to the later processes, because it might take place at greater depth. These problems are compounded by the 'lumping' approach of looking at the variation within the whole volcanic centre, which obscures the potential presence of different magma series. While keeping these caveats in mind, there appears to be a difference in the composition of the subducted slab component in Nisyros compared to the more westerly centres, with high Ba, Sr and Nb contents, and low Pb-isotope ratios. This could be related to sedimentary input from the Nile drainage system. Santorini shows the lowest 'slab contribution' in terms of fluid-mobile elements, and generally lower ratios of the more to less

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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

  7. Long-Term Marine Traffic Monitoring for Environmental Safety in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Giannakopoulos, T.; Gyftakis, S.; Charou, E.; Perantonis, S.; Nivolianitou, Z.; Koromila, I.; Makrygiorgos, A.

    2015-04-01

    The Aegean Sea is characterized by an extremely high marine safety risk, mainly due to the significant increase of the traffic of tankers from and to the Black Sea that pass through narrow straits formed by the 1600 Greek islands. Reducing the risk of a ship accident is therefore vital to all socio-economic and environmental sectors. This paper presents an online long-term marine traffic monitoring work-flow that focuses on extracting aggregated vessel risks using spatiotemporal analysis of multilayer information: vessel trajectories, vessel data, meteorological data, bathymetric / hydrographic data as well as information regarding environmentally important areas (e.g. protected high-risk areas, etc.). A web interface that enables user-friendly spatiotemporal queries is implemented at the frontend, while a series of data mining functionalities extracts aggregated statistics regarding: (a) marine risks and accident probabilities for particular areas (b) trajectories clustering information (c) general marine statistics (cargo types, etc.) and (d) correlation between spatial environmental importance and marine traffic risk. Towards this end, a set of data clustering and probabilistic graphical modelling techniques has been adopted.

  8. Sea cliff erosion in the eastern part of the North Aegean coastline, Northern Greece.

    PubMed

    Xeidakis, George S; Delimani, P K; Skias, S G

    2006-01-01

    The coastal zone is an area where many human activities are taking place. Erosion of the coast obstructs, in various ways, these activities creating occasionally serious socioeconomic and environmental problems. In this paper the coastal erosion problems encountered in the eastern Greek part of the North Aegean Sea Coast, a stretch of about 51 km long adjacent to the city of Alexandroupolis, are discussed. Given the observed type and location of erosion and other sea-action phenomena, the coast under study is divided in two parts/stretches. The western stretch, where the city of Alexandroupolis is presently extending, presents, mainly, cliff erosion problems and retreat of the coastline, very serious in some sections; whereas, the eastern stretch (to the east of the city) exhibits deposition and progression seawards due to the abundance of sediments supplied by Evros river delta. A classification of the coastline according to its relief, geologic material, erosion characteristics and rate, slope failure phenomena as well as the wave energy potential, is presented together with suggestions for case-appropriate mitigation and protection measures regarding the coastal erosion problems. The paper is focusing on the cliff erosion phenomena, since varying in height coastal cliffs made of soft rocks, cover the major part of the investigated coastline (western stretch).

  9. Pesticide residues in fruits and vegetables from the Aegean region, Turkey.

    PubMed

    Bakırcı, Gözde Türköz; Yaman Acay, Dilek Bengü; Bakırcı, Fatih; Ötleş, Semih

    2014-10-01

    The purpose of this study was to investigate pesticide residues in fruits and vegetables from the Aegean region of Turkey. A total of 1423 samples of fresh fruit and vegetables were collected from 2010 to 2012. The samples were analysed to determine the concentrations of 186 pesticide residues. The analyses utilized ultrahigh performance liquid chromatography coupled with tandem mass spectrometry (UPLC/MS/MS) and gas chromatography with an electron capture detector (GC-ECD) confirmed by gas chromatography with mass spectrometry (GC-MS) after a multi-residue extraction procedure (the QuEChERS method). The results were evaluated according to maximum residue limits (MRLs) for each commodity and pesticide by Turkish Regulation. All pomegranate, cauliflower and cabbage samples were pesticides-free. A total of 754 samples contained detectable residues at or below MRLs, and 48 (8.4%) of the fruit samples and 83 (9.8%) of the vegetable samples contained pesticide residues above MRLs. MRL values were most often exceeded in arugula, cucumber, lemon, and grape commodities. All detected pesticides in apricot, carrot, kiwifruit and leek were below the MRLs. Acetamiprid, chlorpyriphos and carbendazim were the most detected pesticide residues. PMID:24799252

  10. Flux measurements in the surface Marine Atmospheric Boundary Layer over the Aegean Sea, Greece.

    PubMed

    Kostopoulos, V E; Helmis, C G

    2014-10-01

    Micro-meteorological measurements within the surface Marine Atmospheric Boundary Layer took place at the shoreline of two islands at northern and south-eastern Aegean Sea of Greece. The primary goal of these experimental campaigns was to study the momentum, heat and humidity fluxes over this part of the north-eastern Mediterranean Sea, characterized by limited spatial and temporal scales which could affect these exchanges at the air-sea interface. The great majority of the obtained records from both sites gave higher values up to factor of two, compared with the estimations from the most widely used parametric formulas that came mostly from measurements over open seas and oceans. Friction velocity values from both campaigns varied within the same range and presented strong correlation with the wind speed at 10 m height while the calculated drag coefficient values at the same height for both sites were found to be constant in relation with the wind speed. Using eddy correlation analysis, the heat flux values were calculated (virtual heat fluxes varied from -60 to 40 W/m(2)) and it was found that they are affected by the limited spatial and temporal scales of the responding air-sea interaction mechanism. Similarly, the humidity fluxes appeared to be strongly influenced by the observed intense spatial heterogeneity of the sea surface temperature.

  11. Bacterial pollution, activity and heterotrophic diversity of the northern part of the Aegean Sea, Turkey.

    PubMed

    Çiftçi Türetken, Pelin S; Altuğ, Gülşen

    2016-02-01

    Isolation and characterization studies of marine heterotrophic bacteria are important to describe and understand eco-metobolism of the marine environments. In this study, diversity and community structures of the culturable heterotrophic bacteria, metabollicaly active bacteria and bacterial pollution in the coastal and offshore areas of Gökçeada Island, in the Northern Aegean Sea, Turkey were investigated from March 2012 to November 2013. The primary hydrographic parameters were recorded in situ. The frequency of the metabolically active bacteria was determined by using a modified staining technique. The indicator bacteria were determined by using membrane filtration technique; 126 bacteria isolates, 24 of them first records for this region, were identified using an automated micro-identification system, VITEK2 Compact30. The results showed that detected bacterial community profiles were significantly different when compared with previous studies conducted in polluted marine areas of Turkey. High frequency of faecal bacteria detected at station 2 indicated that increasing human activities and terrestrial pollution sources are shaping factors for possible risks, regarding recreational uses of this region, in the summer seasons.

  12. The Sponge Community of a Subtidal Area with Hydrothermal Vents: Milos Island, Aegean Sea

    NASA Astrophysics Data System (ADS)

    Pansini, M.; Morri, C.; Bianchi, C. N.

    2000-11-01

    Sponges were sampled by SCUBA diving at six subtidal rocky sites, three of which were close to hydrothermal vents, a common feature on the sea-floor off the south-east coast of Milos. Twenty-five species (2 Calcarea and 23 Demospongiae) were found, few compared with the 589 recorded for the Mediterranean, but an important addition to the scant information on the sponge fauna of the Aegean Sea. The number of species found at vent sites was consistently higher than that found at non-vent sites, but no vent-obligate species could be identified. However, Geodia cydonium and three species of Cliona ( C. copiosa, C. nigricans and C. rhodensis) showed a tendency to colonize vent areas. The former might take advantage of increased silica availability, the latter of the enhanced deposition of carbonates near vents. Substratum cover by sponges (estimated from wire-framed photographs of 0·7 m 2), varied greatly both among and within sites, mostly according to slope. Most sponge species preferred vertical to overhanging, shaded substrata. Proximity to vents seemed to have little or no influence on sponge cover, notwithstanding a primary effect on species diversity.

  13. Polychaetes associated with the sciaphilic alga community in the northern Aegean Sea: spatial and temporal variability

    NASA Astrophysics Data System (ADS)

    Antoniadou, C.; Nicolaidou, A.; Chintiroglou, C.

    2004-10-01

    Polychaete biodiversity has received little attention despite its importance in biomonitoring. This study describes polychaete diversity, and its spatial and temporal variability in infralittoral, hard substrate assemblages. Seven stations were chosen in the central area of the northern Aegean Sea. At each station, one to three depth levels were set (15, 30 and 40 m). Five replicates were collected by scuba diving with a quadrat sampler (400 cm2) from each station and depth level during summer for the spatial analysis, and seasonally for the study of temporal changes. Common biocoenotic methods were employed (estimation of numerical abundance, mean dominance, frequency, Margalef's richness, Shannon-Weaver index and Pielou's evenness). A total of 5,494 individuals, belonging to 79 species, were counted and classified. Diversity indices were always high. Clustering and multidimensional scaling techniques indicated a high heterogeneity of the stations, although these were all characterized by the sciaphilic alga community. A clear seasonal pattern was not detectable. Summer and autumn samples discriminate, while winter and spring form an even group. The abundance/biomass comparison indicated a dominance of k-strategy patterns, characteristic of stable communities.

  14. Human red blood cell behavior under homogeneous extensional flow in a hyperbolic-shaped microchannel

    PubMed Central

    Yaginuma, T.; Oliveira, M. S. N.; Lima, R.; Ishikawa, T.; Yamaguchi, T.

    2013-01-01

    It is well known that certain pathological conditions result in a decrease of red blood cells (RBCs) deformability and subsequently can significantly alter the blood flow in microcirculation, which may block capillaries and cause ischemia in the tissues. Microfluidic systems able to obtain reliable quantitative measurements of RBC deformability hold the key to understand and diagnose RBC related diseases. In this work, a microfluidic system composed of a microchannel with a hyperbolic-shaped contraction followed by a sudden expansion is presented. We provide a detailed quantitative description of the degree of deformation of human RBCs under a controlled homogeneous extensional flow field. We measured the deformation index (DI) as well as the velocity of the RBCs travelling along the centerline of the channel for four different flow rates and analyze the impact of the particle Reynolds number. The results show that human RBC deformation tends to reach a plateau value in the region of constant extensional rate, the value of which depends on the extension rate. Additionally, we observe that the presence of a sudden expansion downstream of the hyperbolic contraction modifies the spatial distribution of cells and substantially increases the cell free layer (CFL) downstream of the expansion plane similarly to what is seen in other expansion flows. Beyond a certain value of flow rate, there is only a weak effect of inlet flow rates on the enhancement of the downstream CFL. These in vitro experiments show the potential of using microfluidic systems with hyperbolic-shaped microchannels both for the separation of the RBCs from plasma and to assess changes in RBC deformability in physiological and pathological situations for clinical purposes. However, the selection of the geometry and the identification of the most suitable region to evaluate the changes on the RBC deformability under extensional flows are crucial if microfluidics is to be used as an in vitro clinical

  15. Human red blood cell behavior under homogeneous extensional flow in a hyperbolic-shaped microchannel.

    PubMed

    Yaginuma, T; Oliveira, M S N; Lima, R; Ishikawa, T; Yamaguchi, T

    2013-01-01

    It is well known that certain pathological conditions result in a decrease of red blood cells (RBCs) deformability and subsequently can significantly alter the blood flow in microcirculation, which may block capillaries and cause ischemia in the tissues. Microfluidic systems able to obtain reliable quantitative measurements of RBC deformability hold the key to understand and diagnose RBC related diseases. In this work, a microfluidic system composed of a microchannel with a hyperbolic-shaped contraction followed by a sudden expansion is presented. We provide a detailed quantitative description of the degree of deformation of human RBCs under a controlled homogeneous extensional flow field. We measured the deformation index (DI) as well as the velocity of the RBCs travelling along the centerline of the channel for four different flow rates and analyze the impact of the particle Reynolds number. The results show that human RBC deformation tends to reach a plateau value in the region of constant extensional rate, the value of which depends on the extension rate. Additionally, we observe that the presence of a sudden expansion downstream of the hyperbolic contraction modifies the spatial distribution of cells and substantially increases the cell free layer (CFL) downstream of the expansion plane similarly to what is seen in other expansion flows. Beyond a certain value of flow rate, there is only a weak effect of inlet flow rates on the enhancement of the downstream CFL. These in vitro experiments show the potential of using microfluidic systems with hyperbolic-shaped microchannels both for the separation of the RBCs from plasma and to assess changes in RBC deformability in physiological and pathological situations for clinical purposes. However, the selection of the geometry and the identification of the most suitable region to evaluate the changes on the RBC deformability under extensional flows are crucial if microfluidics is to be used as an in vitro clinical

  16. Alpine extensional detachment tectonics in the Grande Kabylie metamorphic core complex of the Maghrebides (northern Algeria)

    NASA Astrophysics Data System (ADS)

    Saadallah, A.; Caby, R.

    1996-12-01

    The Maghrebides are part of the peri-Mediterranean Alpine orogen. They expose in their inner zone inliers of high-grade crystalline rocks surrounded by Oligo-Miocene and younger Miocene cover. Detailed mapping coupled with structural and petrological investigations in the Grande Kabylie massif, and the reinterpretation of the available geochronological data, allow us to refute the traditional concept of rigid behaviour of this massif during Alpine events. We show that the dome geometry, the kinematic and metamorphic evolutions and the age pattern are typical of metamorphic core complexes exhumed by extension. A major low-angle detachment fault defined by mylonites and by younger cataclasites has been traced in the massif. The upper unit encompasses pre-Permian phyllites with Variscan {40Ar }/{39Ar } cooling ages, capped by unconformable Mesozoic to Tertiary cover of the Calcareous Range, both mainly affected by extensive Tertiary brittle deformation and normal faulting. The lower unit exposes in two half-domes a continuous tectonic pile, 6-8 km thick, of amphibolite facies rocks and orthogneisses affected by syndashmetamorphic ductile deformation, devoid of retrogression. The regular increase of paleotemperature downward and the {40Ar }/{39Ar } plateau ages around 80 Ma suggest that the high-temperature foliation and associated WNW-directed shear under a high geothermal gradient relate to extensional tectonics developed during Mesozoic lithospheric thinning of the Variscan south European margin. To the north, the Sidi Alli Bou Nab massif exposes another crustal section affected throughout by WNW-directed extensional shear during {HP }/{HT } syndashmetamorphic thinning and with overall {40Ar }/{39Ar } plateau ages of 25 Ma. The Eocene oblique collisional event responsible for crustal thickening was totally overprinted by this new extensional regime, synchronous with the beginning of the opening of the Western Mediterranean oceanic basin. This was also coeval with

  17. Rhaetian extensional tectonics in the Slovenian Basin (Southern Alps): Preliminary results of an outcrop study

    NASA Astrophysics Data System (ADS)

    Oprčkal, P.; Gale, L.; Kolar-Jurkovšek, T.; Rožič, B.

    2012-04-01

    A Late Triassic palaeogeographic position of the Slovenian Basin on the passive continental margin of the Neotethys Ocean to the East and later the Alpine Tethys to the West, implements that its evolution intimately depended on the events in these two areas of extension. Recent research of the "Bača dolomite", the typical Norian-Rhaetian lithologic unit of the Slovenian Basin, resulted in recognition of four extensional tectonic events (Gale et al., this volume). The Lower and Middle Norian tectonic pulses can be recognized throughout the basin. A weakened tectonic activity was recognized in the Rhaetian, followed by more pronounced, but spatially restricted tectonics at the Triassic-Jurassic boundary. Extensional tectonics was attributed to the diminishing rifting in the Neotethys area and to the incipient opening of the Alpine Tethys (Gale et al., this volume). The ongoing fieldwork in the vicinity of Škofja Loka (central Slovenia) resulted in the discovery of palaeofaults in the small-sized quarry that directly evidences the Late Triassic extensional tectonics. Based on superposition, the observed section of the "Bača dolomite" is of the Rhaetian age. The discovery is particularly important because it represents the first direct documentation of the Late Triassic down-faulting in the region. The lowest strata exposed consist of highly bituminous bedded dolostones with scour structures and several meters of mud-supported dolo-breccias. Breccias were downthrown along a normal fault and the created accommodation space filled with bedded dolostone. After complete leveling of topography, another differentiation took place, during which a new normal fault originated, whereas the pre-existing fault was reactivated in an antithetic sense. Thin-bedded dolostones were deposited during slowly abiding movements. The final cessation of tectonics is marked by a uniform deposition of massive dolostone, entirely overlying the fault-dissected sediments.

  18. Origin and role of fluids involved in the seismic cycle of extensional faults in carbonate rocks

    NASA Astrophysics Data System (ADS)

    Smeraglia, Luca; Berra, Fabrizio; Billi, Andrea; Boschi, Chiara; Carminati, Eugenio; Doglioni, Carlo

    2016-09-01

    We examine the potentially-seismic right-lateral transtensional-extensional Tre Monti Fault (central Apennines, Italy) with structural and geochemical methods and develop a conceptual evolutionary model of extensional faulting with fluid involvement in shallow (≤3 km depth) faults in carbonate rocks. In the analysed fault zone, multiscale fault rock structures include injection veins, fluidized ultracataclasite layers, and crackle breccias, suggesting that the fault slipped seismically. We reconstructed the relative chronology of these structures through cross-cutting relationship and cathodoluminescence analyses. We then used C- and O-isotope data from different generations of fault-related mineralizations to show a shift from connate (marine-derived) to meteoric fluid circulation during exhumation from 3 to ≤1 km depths and concurrent fluid cooling from ∼68 to <30 °C. Between ∼3 km and ∼1 km depths, impermeable barriers within the sedimentary sequence created a semi-closed hydrological system, where prevalently connate fluids circulated within the fault zone at temperatures between 60° and 75 °C. During fault zone exhumation, at depths ≤1 km and temperatures <30 °C, the hydrological circulation became open and meteoric-derived fluids progressively infiltrated and circulated within the fault zone. The role of these fluids during syn-exhumation seismic cycles of the Tre Monti Fault has been substantially passive along the whole fault zone, the fluids being passively redistributed at hydrostatic pressure following co-seismic dilatancy. Only the principal fault has been characterized, locally and transiently, by fluid overpressures. The presence of low-permeability clayey layers in the sedimentary sequence contributed to control the type of fluids infiltrating into the fault zone and possibly their transient overpressures. These results can foster the comprehension of seismic faulting at shallow depths in carbonate rocks of other fold-thrust belts

  19. Role of extensional tectonics in the formation of Talladega belt--Blue Ridge successor basins

    SciTech Connect

    Tull, J.F. . Dept. of Geology)

    1993-03-01

    Polydeformed and metamorphosed sequences occurring unconformably above the Cambrian-Ordovician (C-O) miogeoclinal sequence are nested within the Talladega belt (Talladega Group-TG) and Blue Ridge (Mineral Bluff Group-MBG). These successor basin sequences are 2.5--3 km thick and have a possible age range from Ordovician to Devonian, representing the youngest stratigraphic units east of the foreland. They are dominated by turbiditic metaclastic rocks derived from erosion of Grenville basement and its overlying cover of clastic and carbonate rock. Bimodal volcanic rocks occur in the TG, and within-plate mafic extrusive rocks are found in the MBG. The TG consists of a coarsening, thickening, and shallowing upward sequence with a submarine fan-like unit (Lay Dam Formation-LDF) at the base. The LDF contains a thick proximal boulder-bearing olistostromal facies with debris fan lobes stacked vertically and shed from a proximal fault scarp to the SE or S. The vertical stacking of olistostromal deposits, absence of crystalline-cored thrust sheets of this age at the structural top of the basin, and other relationships indicate that the basin did not result from detached deformation to the SE or transcurrent faulting, but rather from extensional faulting. Relationships within the C-O carbonate sequence (Sylacauga Marble Group) unconformably below the TG indicate that the TG basin developed above shallow shelf miogeoclinal rocks inboard of the continental margin hinge line, and thus indicate that Silurian-Devonian extensional structures affected relatively thick Laurentian crust. Similarities in lithofacies and stratigraphic sequence between the TG and MBG indicate that the settling of the MBG may have also been within an extensional basin but basin boundary faults have not yet been identified within the structural block below the pre-MBG unconformity. This basin developed above Laurentian crust previously thinned during late Protozoic rifting.

  20. Relations between extensional tectonics and magmatism within the Southern Oklahoma aulacogen

    NASA Technical Reports Server (NTRS)

    Mcconnell, D. A.; Gilbert, M. C.

    1985-01-01

    Variations in the geometry, distribution and thickness of Cambrian igneous and sedimentary units within southwest Oklahoma are related to a late Proterozoic - early Paleozoic rifting event which formed the Southern Oklahoma aulacogen. These rock units are exposed in the Wichita Mountains, southwest Olkahoma, located on the northern margin of a Proterozoic basin, identified in the subsurface by COCORP reflection data. Overprinting of the Cambrian extensional event by Pennyslvanian tectonism obsured the influence of pre-existing basement structures and contrasting basement lithologies upon the initial development of the aulacogen.

  1. Reconstructing Holocene sea surface salinity changes in the Northern Aegean Sea: evidence from morphological variations of Emiliania huxleyi-coccoliths

    NASA Astrophysics Data System (ADS)

    Herrle, Jens O.; Gebühr, Christina; Bollmann, Jörg; Giesenberg, Annika; Kranzdorf, Philip

    2013-04-01

    The Aegean Sea is a key area for our understanding of the impact of changes in the hydrological cycle on ocean circulation in the Mediterranean Sea. The Aegean Sea appears to be very sensitive to climate changes in Europe because of its small volume and the position between high- and low-latitude climate regimes. Therefore, it is assumed to record environmental change, especially changes in sea surface water salinity (SSS) without a significant time lag with respect to the forcing process (Rohling et al., 2002). However, up to date, SSS cannot be easily reconstructed from geological archives because several assumptions need to be made that lead to a significant error of the salinity estimates (e.g. Rohling, 2000). Here, we present the first high resolution SSS reconstruction from a Holocene sediment core based on a recently developed transfer function using the morphological variation of Emiliania huxleyi coccoliths (Bollmann & Herrle 2007, Bollmann et al., 2009). The core is located in the northern Aegean Sea (eastern Mediterranean Basin) and covers the time period 3 -11ka ago. Sea surface water salinity in the Aegean Sea has varied in concert with temperature oscillations as recorded in Greenland ice cores (iGISP2 ice core δ18O record) with a periodicity of about 900 years (Schulz & Paull, 2002). Four major SSS events can be identified at about 3.9, 4.7, 6.4, 7.4, and 8.2 ka in the northern Aegean Sea that correlate with increases in GISP2 δ18O (Schulz & Paull, 2002) as well as decreasing percentages of tree pollen studied at the same core expect for 3.9 ka (Kotthoff et al., 2008). The most prominent salinity increase occurred during the short-lived 8.2 kyr cold event (e.g., Rohling & Pälike, 2005), which was most likely triggered by a melt-water related perturbation of the Atlantic Meridional Overturning and associated decrease of ocean heat transport to the North Atlantic. We suggest that the salinity fluctuations in the northern Aegean Sea are related to

  2. Miocene extension and extensional folding in an anticlinal segment of the Black Mountains accommodation zone, Colorado River extensional corridor, southwestern United States

    USGS Publications Warehouse

    Varga, R.J.; Faulds, J.E.; Snee, L.W.; Harlan, S.S.; Bettison-Varga, L.

    2004-01-01

    Recent studies demonstrate that rifts are characterized by linked tilt domains, each containing a consistent polarity of normal faults and stratal tilt directions, and that the transition between domains is typically through formation of accommodation zones and generally not through production of throughgoing transfer faults. The mid-Miocene Black Mountains accommodation zone of southern Nevada and western Arizona is a well-exposed example of an accommodation zone linking two regionally extensive and opposing tilt domains. In the southeastern part of this zone near Kingman, Arizona, east dipping normal faults of the Whipple tilt domain and west dipping normal faults of the Lake Mead domain coalesce across a relatively narrow region characterized by a series of linked, extensional folds. The geometry of these folds in this strike-parallel portion of the accommodation zone is dictated by the geometry of the interdigitating normal faults of opposed polarity. Synclines formed where normal faults of opposite polarity face away from each other whereas anticlines formed where the opposed normal faults face each other. Opposed normal faults with small overlaps produced short folds with axial trends at significant angles to regional strike directions, whereas large fault overlaps produce elongate folds parallel to faults. Analysis of faults shows that the folds are purely extensional and result from east/northeast stretching and fault-related tilting. The structural geometry of this portion of the accommodation zone mirrors that of the Black Mountains accommodation zone more regionally, with both transverse and strike-parallel antithetic segments. Normal faults of both tilt domains lose displacement and terminate within the accommodation zone northwest of Kingman, Arizona. However, isotopic dating of growth sequences and crosscutting relationships show that the initiation of the two fault systems in this area was not entirely synchronous and that west dipping faults of the

  3. Late Quaternary stratigraphic and tectonic evolution of the northeastern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Isler, Ekrem Bursin

    The late Quaternary--Recent stratigraphic and tectonic evolution of the NE Aegean Sea, between the Islands of Bozcaada and Lesbos and the Biga Peninsula, is examined using ˜1600 km of seismic reflection and side scan profiles and six cores collected during cruises in 1998, 2000, 2002, and 2003. Detailed examination of the seismic reflection profiles showed that several vertically stacked depositional sequences developed within three NE-SW trending basins. These depositional sequences exhibit oblique- to complex oblique-sigmoid internal seismic reflection configuration and are separated from one another by shelf-crossing unconformities. The chronology of the depositional sequences is constrained by seven radiocarbon and two U/Th dates on in situ shell samples extracted from five cores. Sedimentation rates calculated by using these dates range between 19 cm/kyr and 30 cm/kyr. The ages and the stacked architecture of the depositional sequences, together with the correlations with the oxygen isotopic stages and global sea-level curve reveal that these seaward-prograded delta sequences were developed in a sufficiently rapidly subsiding shelf environment during successive global eustatic sea-level falls associated with late Quaternary glaciations. The progradation of the depositional sequences decelerated and eventually halted shortly after the subsequent major transgressions during which the shelf-crossing unconformities were generated. The terrigenous materials transported throughout the development of the depositional sequences originated from the Tuzla, Karamenderes, and Dumbek rivers draining the Biga Peninsula. Seismic reflection profiles showed no evidence for a major E--W-trending fault system, suggesting that the western continuation of the central strand of the North Anatolian Transform Fault does not exit into the Aegean Sea at Ezine. Detailed mapping of the seismic data showed that two major faults, A1 and beta8, constitute the main fault system in the study

  4. Extension in the Aegean nappe-stacks: Numerical Model and their Geological Validation

    NASA Astrophysics Data System (ADS)

    Lecomte, E.; Huet, B.; Le Pourhiet, L.; Labrousse, L.; Jolivet, L.

    2010-12-01

    After mountain building, the crust exhibits complex structure. Especially, thickening achieved by nappe-stacking induces rheological heterogenities at all scales: from the fault scale up to the crustal scale. This process is likely to influence post-orogenic evolution. However, it is generally not considered in numerical models. In this study, we consider the impact of pre-existing thrusts and nappes structures on the mode of post-orogenic extension. We focus on thermomechanical modeling of reactivation of convergent structures inherited from compression. The Aegean domain that experienced extension after the formation of the Hellenides is considered as a natural laboratory. Natural data are used to constrain a priori the geometry and rheology of the models and to validate them a posteriori. Three problems at different scales are considered. Firstly, we model the reactivation of a thrust as a low angle normal fault. Recent studies show that Aegean detachments were active in the brittle field with very shallow dips. These observations are in contradiction with the classical fault mechanics theory. In order to reconcile both point of view, we propose a new model by introducing an elasto-plastic frictional fault gouge that is able to compact. Our models show that plastic strain on badly oriented faults is favored by compaction of the fault gouge. Secondly, we model the formation of the Corinth rift. The Phyllite-Quartizte nappe is introduced in the upper crust as a weak shallow-dipping layer between the Pindos and Tripolitza massive carbonate nappes. The competence contrast between this nappe and its surrounding controls the dynamics of rifting. High competence contrast leads to the formation of crustal-scale planar faults rooting on the brittle ductile transition of the crust and thin-skinned listric faults rooting on the nappe itself. This model is consistent with the observed microseismicity patterns, the asymmetry of the Corinth Gulf, and the kinematics of fault

  5. Reflection of drill-string extensional waves at the bit-rock contact.

    PubMed

    Poletto, Flavio; Malusa, Massimo

    2002-06-01

    Downward propagating extensional waves are partially reflected at the bit-rock contact. The evaluation of the reflection coefficient is important to obtain while drilling information about the acoustic properties of the formations. The scope of this work is to estimate the bit-rock reflection coefficient, assuming a flat drill bit in perfect contact with the formation. Using the low-frequency approximation, which holds when the wavelength is much larger than the lateral dimensions of the borehole, the drill-string is assumed to be a laterally free rod, and the formation an homogeneous and isotropic medium. This work shows that the reflection coefficient of the extensional waves depends, along with the elastic properties of the formation, on the ratio of the cross sections of the drill-string and borehole. The impedance of the drilled rock can be calculated from the measured reflection coefficient, which is related to the amplitude of waves produced in the string and in the formation by a working drill-bit.

  6. Quaternary extensional growth folding beneath Reno, Nevada, imaged by urban seismic profiling

    USGS Publications Warehouse

    Stephenson, William J.; Frary, Roxy N.; Louie, John; Odum, Jackson K.

    2013-01-01

    We characterize shallow subsurface faulting and basin structure along a transect through heavily urbanized Reno, Nevada, with high‐resolution seismic reflection imaging. The 6.8 km of P‐wave data image the subsurface to approximately 800 m depth and delineate two subbasins and basin uplift that are consistent with structure previously inferred from gravity modeling in this region of the northern Walker Lane. We interpret two primary faults that bound the uplift and deform Quaternary deposits. The dip of Quaternary and Tertiary strata in the western subbasin increases with greater depth to the east, suggesting recurrent fault motion across the westernmost of these faults. Deformation in the Quaternary section of the western subbasin is likely evidence of extensional growth folding at the edge of the Truckee River through Reno. This deformation is north of, and on trend with, previously mapped Quaternary fault strands of the Mt. Rose fault zone. In addition to corroborating the existence of previously inferred intrabasin structure, these data provide evidence for an active extensional Quaternary fault at a previously unknown location within the Truckee Meadows basin that furthers our understanding of both the seismotectonic framework and earthquake hazards in this urbanized region.

  7. Brownian Dynamics Simulation of two-dimensional nanosheets under extensional flow

    NASA Astrophysics Data System (ADS)

    Xu, Yueyi; Green, Micah

    2014-11-01

    We investigated the morphology change of two-dimensional nanosheets under extensional flow using a coarse-grained model. Nanosheets such as graphene are promising materials for a variety of materials and electronics applications; extensional flow fields are used to cast or process liquid nanosheet dispersions in several processing techniques, including spin coating and compression molding. Process parameters, including bending stiffness and Weissenberg numbers can have a significant impact on the nanosheet morphology and the physical properties of the finished products. We use Brownian Dynamics simulations to study the impact of external flow field on a two-dimensional bead-rod lattice model. Our model was previously demonstrated for steady shear flow. Here we studied the change of morphology of graphene over time and varied the sheet size, bending stiffness and Weissenberg number. Our results showed a flattening behavior that increases with Weissenberg number. Our results also showed significant differences between nanosheets as a function of bending stiffness, with contrasting ``plate'' and ``washrag'' results under extension. The intrinsic viscosity first experiences a drop with Weissenberg number followed by a plateau associated with maximum extension.

  8. The importance of flow history in mixed shear and extensional flows

    NASA Astrophysics Data System (ADS)

    Wagner, Caroline; McKinley, Gareth

    2015-11-01

    Many complex fluid flows of experimental and academic interest exhibit mixed kinematics with regions of shear and elongation. Examples include flows through planar hyperbolic contractions in microfluidic devices and through porous media or geometric arrays. Through the introduction of a ``flow-type parameter'' α which varies between 0 in pure shear and 1 in pure elongation, the local velocity fields of all such mixed flows can be concisely characterized. It is tempting to then consider the local stress field and interpret the local state of stress in a complex fluid in terms of shearing or extensional material functions. However, the material response of such fluids exhibit a fading memory of the entire deformation history. We consider a dilute solution of Hookean dumbbells and solve the Oldroyd-B model to obtain analytic expressions for the entire stress field in any arbitrary mixed flow of constant strain rate and flow-type parameter α. We then consider a more complex flow for which the shear rate is constant but the flow-type parameter α varies periodically in time (reminiscent of flow through a periodic array or through repeated contractions and expansions). We show that the flow history and kinematic sequencing (in terms of whether the flow was initialized as shearing or extensional) is extremely important in determining the ensuing stress field and rate of dissipated energy in the flow, and can only be ignored in the limit of infinitely slow flow variations.

  9. Pattern of extensional faulting in pelagic carbonates of the Unbria-Marche Apennines of central Italy

    SciTech Connect

    Alvarez, W. )

    1990-05-01

    The Umbria-Marche Apennines provide a new region in which the nature passive-margin extensional faulting can be studied in outcrop. In these dominantly pelagic carbonate rocks of Jurassic and Cretaceous age, horsts acted as shallow, nonvolcani seamounts, while tilted half grabens formed deeper basins. One well-exposed seamount-basin transition agrees in general with the model of listric normal faulting and tilted half grabens, but shows interesting and significant divergences when studied in detail. A small sedimentary wedge at the faulted margin of a horst-block seamount thickens unexpectedly toward the adjacent basin. This wedge developed because of local convex-upward curvature of the shallowest part of a fault which at depth must have concave-up, listric geometry. The local sedimentary wedge resulted from deposition on the hanging wall as it tilted, followed by differential compaction of younger limestones that lapped onto the gentle slope leading from the horst-block seamount toward the basin. The map pattern of listric normal faulting in the Umbria-Marche Apennines suggests that both principal strain axes were extensional, in contrast to the usual pattern of listric faults crossed by transfer faults.

  10. FROM MICROCONTINENTS TO EXTENSIONAL ALLOCHTHONS: WITNESSES OF HOW CONTINENTS BREAK APART? (Invited)

    NASA Astrophysics Data System (ADS)

    Peron-Pinvidic, G.; Manatschal, G.

    2009-12-01

    It is well known that extensional processes can lead to different crustal configurations, depending notably on lithospheric composition, thermal structure and extension rate. Thereby, rifted margins are characterized, worldwide, by distinct tectonic, geological and magmatic contexts. Direct comparisons are not straightforward. However, even if different, these margins also present a limited number of crustal features that are regularly observed and described such as micro-continents, continental ribbons, H blocks, extensional allochthons and outer highs. If some of these structures have been proposed to be issued from plume-related events and strength differences between oceanic and continental lithosphere, it is still unclear how these different types of crustal bodies are generated and consequently what they may tell us about the underlying processes and associated tectonic evolution. However, we believe each of these features, by their similarities and differences, point to distinct processes (stretching, thinning, exhumation, magmatism, spreading). The aim of this contribution is to present these different "building stones", describe their characteristics and positions within the margins, and discuss the underlying tectonic processes and stratigraphic relationships related to their formation. We propose, using the example of the North Atlantic, that the superposition of specific deformation modes may explain the various types of crustal blocks and, as a consequence, that the occurrence of these various blocks are the witnesses of particular rifting processes.

  11. Localized extensional tectonics in an overall reverse-faulting regime, Northeast Japan

    NASA Astrophysics Data System (ADS)

    Umeda, Koji

    2015-12-01

    In Northeast Japan, it has been recognized that trench-normal compressional stresses, aligned in the approximate direction of plate convergence, tend to dominate stress fields over a broad region. However, a particularly notable event was the shallow, normal-faulting earthquake swarms with a T-axis oriented in the E-W or NW-SE directions that occurred immediately after the 2011 Tohoku-Oki earthquake near the Pacific coast in the Southeast Tohoku district. The stress tensor inversion represents the pre-Tohoku-Oki earthquake stress field in this area as a normal-faulting stress regime with the minimum principal horizontal stress oriented in a roughly NW-SE direction. Additionally, the stress regime varies with depth from normal faulting at shallow depths (<15 km) to thrust faulting at greater depths. Seismic tomography and magnetotelluric soundings defined a geophysical anomaly with low seismic velocity and low resistivity clearly visible beneath the swarm activity, strongly supporting the existence of an interconnected network with fluid-filled porosity. The upper boundary of the conductor is in good agreement with an extensional-compressional stress transition zone. A plausible explanation for these drastic changes in the stress regime is upward flexure of the upper crust due to partly anelastic deformation in the weakened lower crust. Additionally, remarkable upwarping and localized extensional tectonics during the late Pleistocene reflect the long-term rheological heterogeneities in the crust beneath the seismic source region.

  12. Extensional Rheology Experiment Developed to Investigate the Rheology of Dilute Polymer Solutions in Microgravity

    NASA Technical Reports Server (NTRS)

    Logsdon, Kirk A.

    2001-01-01

    A fundamental characteristic of fluid is viscosity; that is, the fluid resists forces that cause it to flow. This characteristic, or parameter, is used by manufacturers and end-users to describe the physical properties of a specific material so that they know what to expect when a material, such as a polymer, is processed through an extruder, a film blower, or a fiber-spinning apparatus. Normally, researchers will report a shear viscosity that depends on the rate of an imposed shearing flow. Although this type of characterization is sufficient for some processes, simple shearing experiments do not provide a complete picture of what a processor may expect for all materials. Extensional stretching flows are common in many polymer-processing operations such as extrusion, blow molding, and fiber spinning. Therefore, knowledge of the complete rheological (ability to flow and be deformed) properties of the polymeric fluid being processed is required to accurately predict and account for the flow behavior. In addition, if numerical simulations are ever able to serve as a priori design tools for optimizing polymer processing operations such as those described above, an accurate knowledge of the extensional viscosity of a polymer system and its variation with temperature, concentration, molecular weight, and strain rate is critical.

  13. Quantification and restoration of extensional deformation along the Western Iberia and Newfoundland rifted margins

    NASA Astrophysics Data System (ADS)

    Sutra, Emilie; Manatschal, Gianreto; Mohn, Geoffroy; Unternehr, Patrick

    2013-08-01

    Many recent papers describe the structure of the Iberia and Newfoundland rifted margins; however, none of them propose kinematic restorations of the complete rift system to quantify the amount of extension necessary to exhume mantle and initiate seafloor spreading. In our study, we use two pairs of cross sections considered as conjugate lines: one across the Galicia Bank-Flemish Cap and the other across the Southern Iberia Abyssal Plain-Flemish Pass. Both transects have been imaged by reflection- and refraction-seismic methods and have been drilled during Ocean Drilling Program Legs 103, 149, 173, and 210. Drilling penetrated parts of the rift stratigraphy and the underlying basement. The cross sections can therefore be considered as the best-documented conjugate transects across present-day hyperextended, magma-poor rifted margins. The aim of this paper is threefold: (1) provide a detailed description of the crustal architecture of the two conjugate sections, (2) define the extensional structures and their ages, and (3) quantify the amount of strain and strain rate accommodated along these lines. This paper proposes a quantitative description of extension along the Iberia-Newfoundland rift system and discusses the limitations and problems in quantifying extensional deformation along hyperextended rifted margins.

  14. A distinct source and differentiation history for Kolumbo submarine volcano, Santorini volcanic field, Aegean arc

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Carey, Steven; Nomikou, Paraskevi; Smet, Ingrid; Godelitsas, Athanasios; Vroon, Pieter

    2016-08-01

    This study reports the first detailed geochemical characterization of Kolumbo submarine volcano in order to investigate the role of source heterogeneity in controlling geochemical variability within the Santorini volcanic field in the central Aegean arc. Kolumbo, situated 15 km to the northeast of Santorini, last erupted in 1650 AD and is thus closely associated with the Santorini volcanic system in space and time. Samples taken by remotely-operated vehicle that were analyzed for major element, trace element and Sr-Nd-Hf-Pb isotope composition include the 1650 AD and underlying K2 rhyolitic, enclave-bearing pumices that are nearly identical in composition (73 wt.% SiO2, 4.2 wt.% K2O). Lava bodies exposed in the crater and enclaves are basalts to andesites (52-60 wt.% SiO2). Biotite and amphibole are common phenocryst phases, in contrast with the typically anhydrous mineral assemblages of Santorini. The strong geochemical signature of amphibole fractionation and the assimilation of lower crustal basement in the petrogenesis of the Kolumbo magmas indicates that Kolumbo and Santorini underwent different crustal differentiation histories and that their crustal magmatic systems are unrelated. Moreover, the Kolumbo samples are derived from a distinct, more enriched mantle source that is characterized by high Nb/Yb (>3) and low 206Pb/204Pb (<18.82) that has not been recognized in the Santorini volcanic products. The strong dissimilarity in both petrogenesis and inferred mantle sources between Kolumbo and Santorini suggests that pronounced source variations can be manifested in arc magmas that are closely associated in space and time within a single volcanic field.

  15. Internal wave measurements on the Cycladic Plateau of the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Alford, Matthew H.; Gregg, Michael C.; Zervakis, Vassilis; Kontoyiannis, Harialos

    2012-01-01

    The internal wave climate in the southern Aegean Sea is examined with an array of two bottom-mounted acoustic Doppler current profilers and three profiling moorings deployed on the northern continental slope of the Cretan Sea for 3 months. Frequency spectra indicate an extremely weak internal wave continuum, about 4-10 times weaker than the Garrett-Munk and Levine reference levels. Spectra are instead dominated by semidiurnal internal tides and near-inertial waves, which are examined in detail by bandpass filtering. In the semidiurnal band, a barotropic tidal flow of ≈2 cm s-1 is observed, with a pronounced spring/neap modulation in phase with the lunar fortnightly cycle. One to two days following several of these spring tide periods, a distinct internal tide featuring 10-20 m vertical displacements and 15-20 cm s-1baroclinic velocities is detectable propagating upward and to the southeast. Time-mean energy increases a factor of 2-5 within about 100 m from the bottom, implying generation and/or scattering from the bottom, whose slope is nearly critical to semidiurnal internal waves over much of the array. Several strong, downward propagating near-inertial events are also seen, each of which occurs following a period of work done by the wind on the mixed layer as estimated from a nearby surface mooring. The high-frequency internal wave continuum is more temporally constant but increases substantially toward the end of the deployment. Significant but unexplained differences in kinetic energy occur between successive spring tide periods in the case of the internal tides and between successive wind events in the case of the near-inertial signals. Substantial variability is observed in the low-frequency flows, which likely contributes to the time variability of the internal wave signals.

  16. Geomorphological Evidence Bearing on the Paired Compressional-Extensional Fronts of the Northern Apennines

    NASA Astrophysics Data System (ADS)

    Alvarez, W.

    2001-12-01

    The close association of compressional folding and extensional normal faulting in the Northern Apennines has long attracted the attention of geologists. Elter et al.(1) showed that an extensional front has been following along, about 100 km behind a NE-migrating compressional front. This puzzling tectonic pattern has most commonly been explained by delamination and rollback, but the identity of the delaminating unit has been controversial. Little attention has been paid to the question whether the migration of the paired tectonic fronts and the generation of structures has been episodic or steady state. Since most or all of the Northern Apennines has emerged from the sea in Neogene time, the drainage pattern of the Peninsula may provide evidence bearing on this question. At the latitude of Gubbio, many short, straight, parallel rivers flow northeast from the main drainage divide to the Adriatic Sea, cutting through large anticlines between the extensional and compressional fronts. Alvarez (2) showed that this pattern arose from a process suggested by Mazzanti and Trevisan (3), in which incipient anticlines, additions to the coastal plain, and downstream increments of the rivers formed synchronously at the advancing shoreline. Deeper and deeper gorges cutting higher and higher anticlines southwest from the Adriatic coast show that the eastern third of the Northern Apennines formed in a roughly steady-state process. From the Tyrrhenian coast to the drainage divide, grabens that formed behind the extensional front have produced a trellis pattern in the three master streams (Arno, Ombrone, Tiber). In the steady-state hypothesis, many short, straight, parallel streams - the former headwaters of the Adriatic rivers - would have been disrupted by graben formation and progressively (from SW to NE) added to the trellis pattern. Close to the extensional front, this disruption would have occurred only in Quaternary time, and one would predict that the abandoned headwater

  17. Assessing the salinity effect on planktonic foraminiferal Mg/Ca: Evidence from Aegean Sea core-top samples (Eastern Mediterranean).

    NASA Astrophysics Data System (ADS)

    Kontakiotis, G.; Antonarakou, A.; Mortyn, P. G.; Triantaphyllou, M. V.; Martínez-Botí, M. À.; Dermitzakis, M. D.

    2009-04-01

    Recent work across the Mediterranean Sea has illustrated a salinity (S) effect on planktonic foraminiferal Mg/Ca, which potentially confounds the use of this as a temperature (T) proxy for paleoceanographic reconstructions. As a likely illustration of this, recent downcore work revealed Mg/Ca values that were unreasonably high to be explained by T variations alone over the last deglaciation and throughout the Holocene. Modern biochemical and oceanographic studies highlight the Aegean Sea as an especially sensitive part of the Mediterranean that is closely connected to global climatic variability. Especially focused on T and S variations in the upper hundred meters of the water column, where energy storage and heat transport occur, we analyse planktonic foraminiferal Mg/Ca from a series of Aegean core tops, spanning a strong S gradient and little T range along a N-S transect. The aim is to isolate and quantify the S influence on the Mg/Ca tracer as well as possible in a field study from the region. We have specifically targeted the tropical spinose species Globigerinoides ruber, since it is the most ubiquitous species in the eastern Mediterranean and generally occurs in a wide range of T and S conditions. From our initially high core-top Mg/Ca measurements, we estimated how much of this was "excess", defined by amount of Mg/Ca exceeding that predicted using modern observed average summer T and a G. ruber calibration equation from the Western Equatorial Pacific (WEP). We then determined excess S values by subtracting WEP salinity values from those observed in our core-top locations. We observed that our results were in close agreement with those previously found for the Mediterranean as a whole, such that excess Mg/Ca is positively correlated with excess S. In the present study we expand on previous core-top results for the Aegean Sea in order to confirm and better quantify the S effect on G. ruber Mg/Ca signatures, such that paleo-records from this region will be

  18. SAXS/WAXS studies of flow-induced crystallization of poly(1-butene) in uniaxial extensional flow

    NASA Astrophysics Data System (ADS)

    McCready, Erica; Burghardt, Wesley

    2013-03-01

    We report studies of flow-induced crystallization of poly(1-butene) in uniaxial extensional flow. Flow was produced using an SER extensional flow fixture housed in a custom built convection oven designed to provide x-ray access for in situ studies of polymer structure using synchrotron x-ray scattering techniques. Samples were loaded into the SER fixture, heated well into the melt, and then cooled to a temperature at which quiescent crystallization would be prohibitively slow. A short interval of uniaxial extensional flow was then applied, after which simultaneous wide- and small-angle x-ray scattering (SAXS and WAXS) patterns were collected to study the phase transformation kinetics and morphology of the subsequent accelerated crystallization. The impact of both deformation rate and total applied strain on the crystallization process were examined.

  19. Heterogeneity and the role of normal stresses during the extensional thinning of non-Brownian shear-thickening fluids.

    PubMed

    Roché, Matthieu; Kellay, Hamid; Stone, Howard A

    2011-09-23

    We contrast the extensional and shear dynamics of non-Brownian suspensions as a function of particle concentration. We show that the thinning rate selected during the viscoelastic pinch-off of a liquid bridge is related to the shear rate at which normal stresses become positive, which differs from the shear rate at the onset of shear thickening. By tracking particles, we demonstrate that the extensional flow is heterogeneous, with local variations of the volume fraction consistent with self-dilution. This nonuniform structure is the cause of the buckling of the threads formed after breakup. PMID:22026859

  20. Late cretaceous extensional tectonics and associated igneous activity on the northern margin of the Gulf of Mexico Basin

    NASA Technical Reports Server (NTRS)

    Bowen, R. L.; Sundeen, D. A.

    1985-01-01

    Major, dominantly compressional, orogenic episodes (Taconic, Acadian, Alleghenian) affected eastern North America during the Paleozoic. During the Mesozoic, in contrast, this same region was principally affected by epeirogenic and extensional tectonism; one episode of comparatively more intense tectonic activity involving extensive faulting, uplift, sedimentation, intrusion and effusion produced the Newark Series of eposits and fault block phenomena. This event, termed the Palisades Disturbance, took place during the Late Triassic - Earliest Jurassic. The authors document a comparable extensional tectonic-igneous event occurring during the Late Cretaceous (Early Gulfian; Cenomanian-Santonian) along the southern margin of the cratonic platform from Arkansas to Georgia.

  1. The influence of regional extensional tectonic stress on the eruptive behaviour of subduction-zone volcanoes

    NASA Astrophysics Data System (ADS)

    Tost, M.; Cronin, S. J.

    2015-12-01

    Regional tectonic stress is considered a trigger mechanism for explosive volcanic activity, but the related mechanisms at depth are not well understood. The unique geological setting of Ruapehu, New Zealand, allows investigation on the effect of enhanced regional extensional crustal tension on the eruptive behaviour of subduction-zone volcanoes. The composite cone is located at the southwestern terminus of the Taupo Volcanic Zone, one of the most active silicic magma systems on Earth, which extends through the central part of New Zealand's North Island. Rhyolitic caldera eruptions are limited to its central part where crustal extension is highest, whereas lower extension and additional dextral shear dominate in the southwestern and northeastern segments characterized by andesitic volcanism. South of Ruapehu, the intra-arc rift zone traverses into a compressional geological setting with updoming marine sequences dissected by reverse and normal faults. The current eruptive behaviour of Ruapehu is dominated by small-scaled vulcanian eruptions, but our studies indicate that subplinian to plinian eruptions have frequently occurred since ≥340 ka and were usually preceded by major rhyolitic caldera unrest in the Taupo Volcanic Zone. Pre-existing structures related to the NNW-SSE trending subduction-zone setting are thought to extend at depth and create preferred pathways for the silicic magma bodies, which may facilitate the development of large (>100 km3) dyke-like upper-crustal storage systems prior to major caldera activity. This may cause enhanced extensional stress throughout the entire intra-arc setting, including the Ruapehu area. During periods of caldera dormancy, the thick crust underlying the volcano and the enhanced dextral share rate likely impede ascent of larger andesitic magma bodies, and storage of andesitic melts dominantly occurs within small-scaled magma bodies at middle- to lower-crustal levels. During episodes of major caldera unrest, ascent and

  2. Timing Aegean extension: Evidence from in situ U-Pb geochronology and cathodoluminescence imaging of granitoids from NW Turkey

    NASA Astrophysics Data System (ADS)

    Black, Karen N.; Catlos, Elizabeth J.; Oyman, Tolga; Demirbilek, Mehmet

    2013-11-01

    The Biga Peninsula of NW Turkey hosts granitoid plutons that record the timing of extension in the Aegean region. Here we focus on three plutons, the Kozak, Eybek, and Kestanbol and apply new methods to obtain a detailed tectonic history of their generation and exhumation. In situ (in thin section) ion microprobe zircon geochronology and color cathodoluminescence (CL) imaging of zircon grains and whole thin sections show these granites experienced magma mixing, brittle deformation, and significant fluid-rock interactions. Zircon ages range from the Late Eocene to Late Miocene with two ages from a single grain that are Permian. The Late Eocene-Early Oligocene ages record the end stages of subduction during the closure of a branch of the Neo-Tethyan Ocean, whereas Late Oligocene-Late Miocene ages record the plutons' extension and exhumation. We present a model in which Kozak, Eybek, and Kestanbol magmas were initially generated by fluid-flux melting from dehydration of the subducting Anatolide-Tauride block, as evidenced by the Late Eocene to Early Oligocene ages. Late Oligocene ages document the initiation of extension in the Biga Peninsula region and correlate to ages timing exhumation of the Kazdağ Massif. Early Miocene ages indicate continued Aegean extension in the southern Biga Peninsula region at this time.

  3. Isostatic uplift, crustal attenuation, and the evolution of an extensional detachment system in southwestern Nevada

    SciTech Connect

    Scott, R.B.

    1987-12-31

    Geological and geophysical evidence supports the existence of extensional detachments, between the Sheep Range and Death Valley. It is proposed that geographically separated pieces of detachments between Death Valley and the Sheep Range are parts of a regional detachment system that has evolved since the Miocene, and that the system consists of lenses of strata separated by an anastomosing network of low- and high-angle normal faults. This manuscript emphasizes the probability that isostatic uplift within the region of greatest crustal attenuation in this system, the Bullfrog Hills core complex, controlled the evolution of the detachment system between the breakaway zone a the Sheep Range and the core complex. Features in this system are described from east to west, which is the apparent direction of tectonic transport.

  4. Tertiary basin development and tectonic implications, Whipple detachment system, Colorado River extensional corridor, California and Arizona

    NASA Technical Reports Server (NTRS)

    Nielson, J. E.; Beratan, K. K.

    1990-01-01

    This paper reports on geologic mapping, stratigraphic and structural observations, and radiometric dating of Miocene deposits of the Whipple detachment system, Colorado River extensional corridor of California and Arizona. From these data, four regions are distinguished in the study area that correspond to four Miocene depositional basins. It is shown that these basins developed in about the same positions, relative to each other and to volcanic sources, as they occupy at present. They formed in the early Miocene from a segmentation of the upper crust into blocks bounded by high-angle faults that trended both parallel and perpendicular to the direction of extension and which were terminated at middle crustal depths by a low-angle detachment fault.

  5. The Mint River Fault: an Extensional Detachment in the York Mountains, Seward Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    Toro, J.; Burnette, L.; Amato, J.; Repetski, J.; Gehrels, G.

    2005-12-01

    The role of crustal extension in the origin of the gneiss domes of the Bering Strait region of Alaska and Russia has been debated for over a decade. Alternative models for gneiss dome formation include 1) thermal re-equilibration after crustal thickening by arc collision (Lieberman, 1988; Patrick and Evans, 1989); 2) extensional collapse of the crust during with mid-Cretaceous magmatism (Miller et al., 1992; Amato et al., 1994) and 3) thermally-induced diapiric rise of the high-grade rocks (Calvert et al., 1999). One major difference with the classic metamorphic core complexes of the Basin and Range is that, because of deep exhumation, evidence for mid-Cretaceous supra-crustal extension has not been widely documented in the Bering Strait region. In the York Mountains, the one area of the Seward Peninsula where unmetamorphosed rocks are preserved, the structure was originally described as a thrust belt (Sainsbury, 1969). New detailed mapping, structural analysis, 40Ar/39Ar thermochronology, and conodont biostratigraphy carried out in the York Mountains show that the Mint River Fault, which is the basal detachment of the supposed thrust belt, is actually a low angle extensional detachment fault. This fault separates polydeformed low greenschist grade rocks in the lower plate from unmetamorphosed Lower Ordovician to Silurian carbonates in the upper plate. The upper plate is cut by three major normal faults, the largest of which has about 4 km of down-to-the-south slip. These faults also tilt the Early Paleozoic carbonate succession. A younger-on-older relationship across one of the mayor faults is documented by conodont biostratigraphy demonstrating that these are not thrusts, as was previously believed. Stress inversion, based on minor brittle faults in the upper plate, indicates a direction of extension of 194, which is consistent with the strike of major normal faults. No direct evidence of bedding-plane thrusting could be documented, although minor folds do exist

  6. New approach to date the extensional tectonics in the Betic Chain (Spain)

    NASA Astrophysics Data System (ADS)

    Julián Esteban, José; María Tubía, José; Cuevas, Julia; Seward, Diane; Larionov, Alexander; Sergeev, Sergey; Navarro-Vilá, Francisco

    2013-04-01

    The Betic Cordilleras, in southern Spain, represent a good example of a collisional orogen disaggregated by extensional collapse in a convergent setting during the Miocene. The Alpujarride and Malaguide Complexes, in the Internal Zone, are bounded by an extensional detachment, previously interpreted as a thrust-nappe. In the western Betics, the Malaguide Complex overlies the Los Reales nappe (one of the tectonic slices that conforms the Alpujarride Complex) and although their boundary is characterized as a brittle-ductile extensional detachment, little is known about its age of movement. In order to constraint the age of the detachment, two dolerite dykes cut by the boundary were dated by U-Pb SHRIMP on zircons along with nine samples, from the lowest to the upper structural levels of the Malaguide Complex, by zircon fission-track analysis (ZFT). Zircons separated from dolerite dykes display rounded or eroded edges bounded by light or dark luminescent rims. Zircons cores with igneous appearance (euhedral, oscillatory zoning, high Th/U content) yield 206Pb/238U ages between 1799 and 264 Ma, which cannot be correlated with dolerite dyke intrusion, as similar dykes appear within Middle-Upper Triassic pelites in other Alpujarride sections. Otherwise, the external rims yield ages between 1187 to 28 Ma. Four of the youngest analysed zircon rims show Th/U ratios consistent with a metamorphic origin. These zircons define a mixing line intersecting the Concordia at 20.9 ± 9 (2σ), that agrees with the age of the thermal Alpine metamorphism. Two of the youngest rims display high Th/U contents, common in igneous zircons. They give concordant ages of 33.1 ± 1.5 (2σ) and 39.0 ± 2.5 (2σ) Ma. However, the youngest is the only one that has geological meaning, as similar ages have been reported using different geochronological systems. Therefore, it could be considered as the age of dolerite dyke intrusion. The ZFT samples yield ages between 18.6 ± 1.8 (2σ) and 25.8 ± 3

  7. Comparison of the Single Molecule Dynamics of Linear and Circular DNAs in Planar Extensional Flows

    NASA Astrophysics Data System (ADS)

    Li, Yanfei; Hsiao, Kai-Wen; Brockman, Christopher; Yates, Daniel; McKenna, Gregory; Schroeder, Charles; San Francisco, Michael; Kornfield, Julie; Anderson, Rae

    2015-03-01

    Chain topology has a profound impact on the flow behaviors of single macromolecules. The absence of free ends separates circular polymers from other chain architectures, i.e., linear, star, and branched. In the present work, we study the single chain dynamics of large circular and linear DNA molecules by comparing the relaxation dynamics, steady state coil-stretch transition, and transient molecular individualism behaviors for the two types of macromolecules. To this end, large circular DNA molecules were biologically synthesized and studied in a microfluidic device that has a cross-slot geometry to develop a stagnation point extensional flow. Although the relaxation time of rings scales in the same way as for the linear analog, the circular polymers show quantitatively different behaviors in the steady state extension and qualitatively different behaviors during a transient stretch. The existence of some commonality between these two topologies is proposed. Texas Tech University John R. Bradford Endowment.

  8. A Geothermal GIS for Nevada: Defining Regional Controls and Favorable Exploration Terrains for Extensional Geothermal Systems

    USGS Publications Warehouse

    Coolbaugh, M.F.; Taranik, J.V.; Raines, G.L.; Shevenell, L.A.; Sawatzky, D.L.; Bedell, R.; Minor, T.B.

    2002-01-01

    Spatial analysis with a GIS was used to evaluate geothermal systems in Nevada using digital maps of geology, heat flow, young faults, young volcanism, depth to groundwater, groundwater geochemistry, earthquakes, and gravity. High-temperature (>160??C) extensional geothermal systems are preferentially associated with northeast-striking late Pleistocene and younger faults, caused by crustal extension, which in most of Nevada is currently oriented northwesterly (as measured by GPS). The distribution of sparse young (160??C) geothermal systems in Nevada are more likely to occur in areas where the groundwater table is shallow (<30m). Undiscovered geothermal systems may occur where groundwater levels are deeper and hot springs do not issue at the surface. A logistic regression exploration model was developed for geothermal systems, using young faults, young volcanics, positive gravity anomalies, and earthquakes to predict areas where deeper groundwater tables are most likely to conceal geothermal systems.

  9. Synovial Fluid Response to Extensional Flow: Effects of Dilution and Intermolecular Interactions

    PubMed Central

    Haward, Simon J.

    2014-01-01

    In this study, a microfluidic cross-slot device is used to examine the extensional flow response of diluted porcine synovial fluid (PSF) samples using flow-induced birefringence (FIB) measurements. The PSF sample is diluted to 10× 20× and 30× its original mass in a phosphate-buffered saline and its FIB response measured as a function of the strain rate at the stagnation point of the cross-slots. Equivalent experiments are also carried out using trypsin-treated PSF (t-PSF) in which the protein content is digested away using an enzyme. The results show that, at the synovial fluid concentrations tested, the protein content plays a negligible role in either the fluid's bulk shear or extensional flow behaviour. This helps support the validity of the analysis of synovial fluid HA content, either by microfluidic or by other techniques where the synovial fluid is first diluted, and suggests that the HA and protein content in synovial fluid must be higher than a certain minimum threshold concentration before HA-protein or protein-protein interactions become significant. However a systematic shift in the FIB response as the PSF and t-PSF samples are progressively diluted indicates that HA-HA interactions remain significant at the concentrations tested. These interactions influence FIB-derived macromolecular parameters such as the relaxation time and the molecular weight distribution and therefore must be minimized for the best validity of this method as an analytical technique, in which non-interaction between molecules is assumed. PMID:24651529

  10. Carbonate sedimentation in an extensional active margin: Cretaceous history of the Haymana region, Pontides

    NASA Astrophysics Data System (ADS)

    Okay, Aral I.; Altiner, Demir

    2016-10-01

    The Haymana region in Central Anatolia is located in the southern part of the Pontides close to the İzmir-Ankara suture. During the Cretaceous, the region formed part of the south-facing active margin of the Eurasia. The area preserves a nearly complete record of the Cretaceous system. Shallow marine carbonates of earliest Cretaceous age are overlain by a 700-m-thick Cretaceous sequence, dominated by deep marine limestones. Three unconformity-bounded pelagic carbonate sequences of Berriasian, Albian-Cenomanian and Turonian-Santonian ages are recognized: Each depositional sequence is preceded by a period of tilting and submarine erosion during the Berriasian, early Albian and late Cenomanian, which corresponds to phases of local extension in the active continental margin. Carbonate breccias mark the base of the sequences and each carbonate sequence steps down on older units. The deep marine carbonate deposition ended in the late Santonian followed by tilting, erosion and folding during the Campanian. Deposition of thick siliciclastic turbidites started in the late Campanian and continued into the Tertiary. Unlike most forearc basins, the Haymana region was a site of deep marine carbonate deposition until the Campanian. This was because the Pontide arc was extensional and the volcanic detritus was trapped in the intra-arc basins and did not reach the forearc or the trench. The extensional nature of the arc is also shown by the opening of the Black Sea as a backarc basin in the Turonian-Santonian. The carbonate sedimentation in an active margin is characterized by synsedimentary vertical displacements, which results in submarine erosion, carbonate breccias and in the lateral discontinuity of the sequences, and differs from blanket like carbonate deposition in the passive margins.

  11. Recognizing Mantle Domains Related to an Extensional Cycle: the Record from Western Europe

    NASA Astrophysics Data System (ADS)

    Picazo, S.; Muntener, O.; Manatschal, G.

    2015-12-01

    Most of the studies on rifted margins have shown that the classical predictions of models assuming a "homogeneous" mantle lithosphere without some inheritance are unable to capture the observed large variety of magmatic budgets as a function of extension. More recently, new ideas and concepts have been developed to understand the evolution of the mantle lithosphere in hyper-extended magma-poor rifted margins that are mainly based on observations from the present-day Iberia-Newfoundland and ancient Alpine Tethys rifted margins and the Pyrenean systems. In contrast to the classical assumption assuming a simple, isotropic mantle lithosphere, these new models integrate observations from exposed and drilled mantle rocks and propose that the mantle lithosphere evolved and was modified during an extensional cycle from post-orogenic collapse through several periods of rifting to embryonic oceanic (ultra-) slow seafloor spreading. But it is, at present, unclear how far these ideas can be generalized and if they can explain the nature of mantle rocks observed across Western Europe and, in a more general way, at Atlantic type rifted margins. We review the available mantle data from Western Europe, i.e. ophiolite massifs, xenoliths and dredged samples, revisit the available terminology concerning mantle massifs and xenoliths and compile the available data to identify different mantle domains. We define chemical and petrological characteristics of mantle domains based on clinopyroxene and spinel compositions and compile them on present-day and paleo-geographic maps of Western Europe. Finally we link the observed distribution of mantle domains to the post-Variscan extensional cycle and link domains to processes related to the late post-Variscan extension, the rift evolution and refertilization associated to hyper-extension and the development of embryonic oceanic domains.

  12. Synovial fluid response to extensional flow: effects of dilution and intermolecular interactions.

    PubMed

    Haward, Simon J

    2014-01-01

    In this study, a microfluidic cross-slot device is used to examine the extensional flow response of diluted porcine synovial fluid (PSF) samples using flow-induced birefringence (FIB) measurements. The PSF sample is diluted to 10× 20× and 30× its original mass in a phosphate-buffered saline and its FIB response measured as a function of the strain rate at the stagnation point of the cross-slots. Equivalent experiments are also carried out using trypsin-treated PSF (t-PSF) in which the protein content is digested away using an enzyme. The results show that, at the synovial fluid concentrations tested, the protein content plays a negligible role in either the fluid's bulk shear or extensional flow behaviour. This helps support the validity of the analysis of synovial fluid HA content, either by microfluidic or by other techniques where the synovial fluid is first diluted, and suggests that the HA and protein content in synovial fluid must be higher than a certain minimum threshold concentration before HA-protein or protein-protein interactions become significant. However a systematic shift in the FIB response as the PSF and t-PSF samples are progressively diluted indicates that HA-HA interactions remain significant at the concentrations tested. These interactions influence FIB-derived macromolecular parameters such as the relaxation time and the molecular weight distribution and therefore must be minimized for the best validity of this method as an analytical technique, in which non-interaction between molecules is assumed.

  13. Carbonate sedimentation in an extensional active margin: Cretaceous history of the Haymana region, Pontides

    NASA Astrophysics Data System (ADS)

    Okay, Aral I.; Altiner, Demir

    2016-03-01

    The Haymana region in Central Anatolia is located in the southern part of the Pontides close to the İzmir-Ankara suture. During the Cretaceous, the region formed part of the south-facing active margin of the Eurasia. The area preserves a nearly complete record of the Cretaceous system. Shallow marine carbonates of earliest Cretaceous age are overlain by a 700-m-thick Cretaceous sequence, dominated by deep marine limestones. Three unconformity-bounded pelagic carbonate sequences of Berriasian, Albian-Cenomanian and Turonian-Santonian ages are recognized: Each depositional sequence is preceded by a period of tilting and submarine erosion during the Berriasian, early Albian and late Cenomanian, which corresponds to phases of local extension in the active continental margin. Carbonate breccias mark the base of the sequences and each carbonate sequence steps down on older units. The deep marine carbonate deposition ended in the late Santonian followed by tilting, erosion and folding during the Campanian. Deposition of thick siliciclastic turbidites started in the late Campanian and continued into the Tertiary. Unlike most forearc basins, the Haymana region was a site of deep marine carbonate deposition until the Campanian. This was because the Pontide arc was extensional and the volcanic detritus was trapped in the intra-arc basins and did not reach the forearc or the trench. The extensional nature of the arc is also shown by the opening of the Black Sea as a backarc basin in the Turonian-Santonian. The carbonate sedimentation in an active margin is characterized by synsedimentary vertical displacements, which results in submarine erosion, carbonate breccias and in the lateral discontinuity of the sequences, and differs from blanket like carbonate deposition in the passive margins.

  14. Geodynamic features along the Christianna-Santorini-Kolumbo tectonic line (South Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Nomikou, Paraskevi; Papanikolaou, Dimitrios; Carey, Steve; Bejelou, Konstantina; Sakellariou, Dimitris; Kilias, Stefanos; Camilli, Rich; Escartin, Javier; Bell, Kathrine; Parks, Michelle

    2013-04-01

    Numerous oceanographic surveys have been conducted in Santorini Volcanic Group (South Aegean Sea) since 2001, revealing the spectacular morphology of the seafloor (multibeam data) and the sub-seafloor stratigraphic horizons (seismic profiles). Technological advancements in seafloor exploration such as ROVs and a submersible, enabled us to observe products of submarine volcanism that were previously inaccessible. In addition, gravity and box coring, geological and biological samples have been collected from selected areas for further analysis. The offshore geophysical survey in Santorini shows that recent volcanism occurred along a NE-SW tectonic zone named as Christianna-Santorini-Kolumbo (CSK) line. Christiana islets and three newly discovered submarine volcanic domes, with small colonies of yellow, presumably sulfur-reducing hydrothermal bacteria, occur in the southwestern part of the line. The presently active intra caldera volcanic domes of Palea and Nea Kameni islands and the low temperature (17-24°C) vent mounds covered by yellowish bacterial mat occupy the middle part of the line. The Santorini vent field is linked with the Kolumbo normal fault onshore which is likely controlling the pathways of hydrothermal circulation within the caldera. The most prominent feature at the NE part of this zone, is Kolumbo submarine volcanic chain which is extended 20Km with several volcanic domes aligned along this direction. The Kolumbo volcano had an explosive eruption in 1650 that killed 70 people on Santorini. The hydrothermal vent field in the crater floor of Kolumbo consists dominantly of active and inactive sulfide-sulfate structures in the form of vertical spires and pinnacles, mounds and flanges along a NE-SW trend, with temperatures up to 220°C and vigorous CO2 gas emission. For several years, the highest frequency of earthquakes was concentrated mainly in the vicinity of Kolumbo volcano. However, during 2011-2012 both seismic and geodetic unrest began abruptly

  15. Oblique opening of Skyros Basin in the North Aegean Sea, based on Morphotectonic Analysis

    NASA Astrophysics Data System (ADS)

    Papanikolaou, Dimitris; Nomikou, Paraskevi; Livanos, Isidoros; Papantoniou, George; Rousakis, Grigoris; Lampridou, Danai

    2015-04-01

    Detailed analysis of swath bathymetry and seismic reflection profiling has revealed the morphotectonic structure of the Skyros Basin in North Aegean Sea (Greece). The overall geometry of the basin is shaped by a major slope discontinuity, separating the continental platform from the continental slope at depths between 200-400m. The basin forms an equilateral triangle. Its base is 50km long NW-SE trending at the southwest, parallel to the Skyros Island, whereas its pic is located at the northeast, north of Lesvos Island. The basin comprises 9 sub-basins at depths varying from 1200m at the southwest to 600m to the northeast and is structurally divided into three parts: i) the eastern part forms a longitudinal semi-graben with one sub-basin trending ENE-WSW of 45km length, but only 5-8 Km width at depths varing between 600-700m. This sub-basin is bounded to the south by a marginal fault of >1.5km throw but with unknown horizontal displacement. ii) the central part that forms the predominant part of the triangle with 45 Km long NW-SE trending base and 70km long axis at the NE-SW direction. The central part corresponds to an assymetric graben with a 70km long major marginal fault with >1500m throw along its southern slopes and a 70 km long antithetic fault with >400m throw along its northern slopes. It comprises 5 sub-basins with depths ranging between 950-700m, bounded by important E-W trending strike slip fault zones, characterized by flower structures, with minor vertical components ranging from a few meters up to 200m. iii) the western part of the basin trends NW-SE, is 55 Km long and 25 Km wide, revealing a NW-SE tectonic graben. It comprises two sub-basins, oriented NW-SE separated by an intermediate transverse fault zone. The throw of the western marginal faults offshore Skyros Island exceeds 1200m, whereas the throw of the parallel faults creating the NW-SE tectonic graben is limited to a few hundreds meters. It should be emphasized that the Alpine basement was

  16. Carbonate assimilation during magma evolution at Nisyros (Greece), South Aegean Arc: Evidence from clinopyroxenite xenoliths

    NASA Astrophysics Data System (ADS)

    Spandler, Carl; Martin, Lukas H. J.; Pettke, Thomas

    2012-08-01

    To contribute to the understanding of magma evolution in arc settings we investigate the oldest volcanic unit (Kanafià Synthem) of Nisyros volcano, located in the eastern Aegean Sea (Greece). The unit consists of porphyritic pillow lavas of basaltic andesite composition with trace element signatures that are characteristic of island-arc magmas. Two lava types are distinguished on the basis of geochemistry and the presence or absence of xenoliths, with the xenolith-bearing lavas having distinctly elevated Sr, MREE/HREE and MgO/Fe2O3 compared to the xenolith-free lavas. Xenoliths include relatively rare quartzo-feldspathic fragments that represent continental-type material, and coarse clinopyroxenite xenoliths that consist largely of aluminous and calcic clinopyroxene, and accessory aluminous spinel. Anorthite-diopside reaction selvages preserved around the clinopyroxenite xenoliths demonstrate disequilibrium between the xenoliths and the host magma. The xenolith clinopyroxene is distinctly enriched in most lithophile trace elements compared to clinopyroxene phenocrysts in the host magmas. A notable exception is the Sr concentration, which is similar in both clinopyroxene types. The high Al and low Na contents of the clinopyroxenites preclude a cumulate, deep metamorphic, or mantle origin for these xenoliths. Instead, their composition and mineralogy are diagnostic of skarn rocks formed by magma-carbonate interaction in the mid/upper crust. The Kanafià lavas are interpreted to have undergone crystal fractionation, magma mixing/mingling and crustal assimilation while resident in the upper crust. We show that magma-carbonate reaction and associated skarn formation does not necessarily result in easily recognised modification of the melt composition, with the exception of increasing Sr contents. Carbonate assimilation also releases significant CO2, which will likely form a free vapour phase due to the low CO2 solubility of arc magmas. In the broader context, we stress

  17. Bacterial and organic matter distribution in the sediments of the Thracian Sea (NE Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Polymenakou, Paraskevi N.; Fragkioudaki, Glykeria; Tselepides, Anastasios

    2007-10-01

    Recently, black carbon has been introduced as the form of carbon that may be separated from the biologically mediated carbon cycle thereby representing the non-bioavailable fraction of the estimated organic carbon. It has been speculated that the bioavailability of organic matter may be a limiting factor for the presence of active bacteria within the sediments. In order to address this question, marine sediments were collected from the Thracian Sea (Eastern Mediterranean), a complex system impacted by riverine inputs and Black Sea water masses. In addition to counts of total bacteria, we estimated the fraction of active bacteria by using a destaining step to the DAPI staining method. Black carbon was also estimated following the thermal oxidation method in order to determine the fraction of the refractory organic matter. The fraction of black carbon to total organic carbon varied from 16% to 53% indicating that black carbon constitutes a significant pool of sedimentary organic carbon in the Thracian sea. A fraction ranging from 18% to 97% was scored as nucleoid containing cells. We did not record any significant differences in the fraction of nucleoid-containing bacteria among sediment depths ( P<0.05) indicating that there was no accumulation of dead bacterial cells with depth. The same was observed for the fraction of black carbon and bioavailable organic carbon with sediment depth ( P<0.05) indicating that benthic consumers are not the key regulators of the organic matter pool in these sediments but have a minor effect. A possible reason for these observations and for the uncoupling between the active bacterial fraction and the bioavailability of organic matter could be (i) the presence of refractory components in the estimated bioavailable organic matter and (ii) the hydrological and geological complexity of the study area. The North Aegean marginal slopes are highly unstable experiencing frequent seismic events. These events are capable of inducing sediment

  18. The larvae of Hydropsyche rhadamanthys Malicky 2001 and Hydropsyche sarpedon Malicky 2001 (Trichoptera: Hydropsychidae), endemics of Crete (South Aegean, Greece), with notes on their ecology.

    PubMed

    Karaouzas, Ioannis

    2016-04-04

    The larvae of Hydropsyche rhadamanthys Malicky 2001 and Hydropsyche sarpedon Malicky 2001, endemics of Crete Island, Greece, are described for the first time. The diagnostic features of the species are described and illustrated, and some information regarding their ecology is included. In addition, diagnostic characters for larvae of the known Aegean Hydropsyche species are provided.

  19. The larvae of the Aegean endemic caddisflies Hydropsyche debirasi Malicky 1974 and Hydropsyche kleobis Malicky 2001 (Trichoptera: Hydropsychidae) with notes on their ecology and zoogeography.

    PubMed

    Karaouzas, Ioannis

    2013-01-01

    The larvae of Hydropsyche debirasi Malicky 1974 and Hydropsyche kleobis Malicky 2001, endemics of the Aegean Islands, Greece, are described for the first time. The diagnostic features of the species are described and illustrated and some information regarding their ecology and zoogeography are included.

  20. Assessment of ENSEMBLES regional climate models for the representation of monthly wind characteristics in the Aegean Sea (Greece): Mean and extremes analysis

    NASA Astrophysics Data System (ADS)

    Anagnostopoulou, Christina; Tolika, Konstantia; Tegoulias, Ioannis; Velikou, Kondylia; Vagenas, Christos

    2013-04-01

    The main scope of the present study is the assessment of the ability of three of the most updated regional climate models, developed under the frame of the European research project ENSEMBLES (http://www.ensembles-eu.org/), to simulate the wind characteristics in the Aegean Sea in Greece. The examined models are KNMI-RACMO2, MPI-MREMO, and ICTP - RegCM3. They all have the same spatial resolution (25x25km) and for their future projections they are using the A1B SRES emission scenarios. Their simulated wind data (speed and direction) were compared with observational data from several stations over the domain of study for a time period of 25 years, from 1980 to 2004 on a monthly basis. The primer data were available every three or six hours from which we computed the mean daily wind speed and the prevailing daily wind direction. It should be mentioned, that the comparison was made for the grid point that was the closest to each station over land. Moreover, the extreme speed values were also calculated both for the observational and the simulated data, in order to assess the ability of the models in capturing the most intense wind conditions. The first results of the study showed that the prevailing winds during the winter and spring months have a north - northeastern or a south - south western direction in most parts of the Aegean sea. The models under examination seem to capture quite satisfactorily this pattern as well as the general characteristics of the winds in this area. During summer, winds in the Aegean Sea have mainly north direction and the models have quite good agreement both in simulating this direction and the wind speed. Concerning the extreme wind speed (percentiles) it was found that for the stations in the northern Aegean all the models overestimate the extreme wind indices. For the eastern parts of the Aegean the KNMI and the MPI model underestimate the extreme wind speeds while on the other hand the ICTP model overestimates them. Finally for the

  1. Prediction of bending set, wave efficacy, and hair damage using an extensional permanent waving treatment and the 20% index value.

    PubMed

    Ueno, Yuzo; Namiki, Hideo

    2015-01-01

    To predict "wave efficacy" as evaluated by hairdressers, an extensional permanent waving treatment was performed on human hair fibers using various wave lotions manufactured in Japan. Glass columns devised for the purpose were equipped with a tensile tester in order to increase the measurement accuracy. Notably, the observed set agreed with the theoretical set. In addition, the data for the extensional set exhibited good correlation with the bending set and the wave efficacy assessed in a beauty parlor, and hair damage was estimated by the characteristic change in the 20% index. The following facts were experimentally determined. First, the Young's modulus of the hair fibers after extensional permanent waving treatment continually decreased with an increase in the reduction of the fibers and then abruptly decreased at 80% reduction. Second, the reduction of hair treated with the ammonium salt of thioglycolic acid followed pseudo first-order kinetics only during the initial stage of the reaction, independent of the pH level. Third, the 20% index of the individual virgin hairs remained constant in water at 30°C and also correlated with the Young's modulus of the hair after extensional permanent waving treatment.

  2. Suppositions, Extensionality, and Conditionals: A Critique of the Mental Model Theory of Johnson-Laird and Byrne (2002)

    ERIC Educational Resources Information Center

    Evans, Jonathan St. B. T.; Over, David E.; Handley, Simon J.

    2005-01-01

    P. N. Johnson-Laird and R. M. J. Byrne proposed an influential theory of conditionals in which mental models represent logical possibilities and inferences are drawn from the extensions of possibilities that are used to represent conditionals. In this article, the authors argue that the extensional semantics underlying this theory is equivalent to…

  3. On the link between orogenic shortening and back-arc extensional collapse in low topography orogens

    NASA Astrophysics Data System (ADS)

    Matenco, L. C.

    2012-04-01

    Classical models of orogenic evolution assume that back arc basins form in the hinterland of orogens, collapsing the upper plate above oceanic subduction zones. This is a common characteristic commonly thought to apply to all low-topography orogens of Mediterranean type driven by the fast roll-back of subducted slabs, or other analogues such as the Miocene to recent evolution of the SE Asia subduction zones. This extension may take place far at the interior of the upper plate, as is the case in various segments of the Carpathians or in the core of the SE Asian domain, but in most cases of the Dinarides, Apennines or Hellenides it take place superposed or far into the foreland of oceanic suture zones. Therefore, the term back-arc extension in many cases is misleading, as exhumation along major detachment zones takes place in the core of the orogen (Rif, Betics), in the accreted crustal material of the lower plate (Apennines, Dinarides) or even in a presumed former fore-arc (Aegean, Sunda-Banda arc). In all these subduction zones, collision has largely duplicated crustal blocks from the lower plate and has gradually shifted subduction zone far towards the lower plate. As a result, crustal thickening takes place in the foreland of the orogen, in contrast with the typical crustal roots of the high convergence orogens, such as the Alps or Himalaya. This demonstrate an active shift of the main subduction zone, the position of slabs detected by teleseismic mantle tomography is displaced to the foreland and cannot be connected with the position of the lower plate crust beneath the orogen. This shift is associated with large scale magmatism with unusual large crustal signatures, atypical for subduction related magmas. These observations demonstrate the need for an active reconsideration of existing orogenic models which should include displacements of subduction zones during orogenic shortening and an active investigation of the role of continental subduction and associated

  4. Present-day deformation across the Basin and Range Province, western United States

    USGS Publications Warehouse

    Thatcher, W.; Foulger, G.R.; Julian, B.R.; Svarc, J.; Quilty, E.; Bawden, G.W.

    1999-01-01

    The distribution of deformation within the Basin and Range province was determined from 1992, 1996, and 1998 surveys of a dense, 800-kilometer- aperture, Global Positioning System network, Internal deformation generally follows the pattern of Holocene fault distribution and is concentrated near the western extremity of the province, with lesser amounts focused near the eastern boundary. Little net deformation occurs across the central 500 kilometers of the network in western Utah and eastern Nevada. Concentration of deformation adjacent to the rigid Sierra Nevada block indicates that external plate-driving forces play an important role in driving deformation, modulating the extensional stress field generated by internal buoyancy forces that are due to lateral density gradients and topography near the province boundaries.

  5. Paleofluid evolution of strike-slip compartmentalized extensional fault zones in the Jabal Qusaybah anticline, Salakh Arc, Oman

    NASA Astrophysics Data System (ADS)

    Balsamo, Fabrizio; Clemenzi, Luca; Storti, Fabrizio; Mozafari, Mahtab; Solum, John; Swennen, Rudy; Taberner, Conxita; Tueckmantel, Christian

    2015-04-01

    The E-W-trending Jabal Qusaybah anticline, developed in layered Cretaceous carbonates, is located at the western termination of the Salakh Arc, Oman Mountains. The anticline is 10 km long and is characterized by a complex fault pattern which mainly includes NE-SW left-lateral strike-slip and N-S extensional fault zones. The N-S striking extensional fault zones are best developed in the central sector of the anticlinal crest, likely due to along-strike outer-arc extension associated with positive fault inversion and salt migration. Extensional fault zones are perpendicular to the fold axis and geometrically confined within major NE-SW left-lateral strike-slip fault zones. They have trace lengths ranging from a few m up to ~800 m, and displacements ranging from a few dm up to ~60 m. Fault zones consist of cataclastic fault cores (~1-15 cm thick) surrounded by vein-dominated damage zones. Overall, fault zones show significant volumes of dilation breccia texture, m-thick infillings of calcite crystals, and cm- to m-thick veins localized at fault tip zones, areas of fault overlap, and zones of interaction between strike-slip and extensional fault segments. By analyzing fault abutting geometries, detailed vein relative chronology, delta13C and delta18O signatures and fluid inclusion data from calcite veins and calcite fault infillings, we propose a model where a deep seated left-lateral strike-slip fault system, active during the growth of the anticline, inhibited the lateral propagation of late-stage transversal extensional fault zones. Our findings show that, in this geological setting, the structural position, rather than fault throw, is the parameter controlling the location of the more dilatant fault segments.

  6. Uplift of sedimentary basins in an extensional setting as a result of the migration of a thermal anomaly

    NASA Astrophysics Data System (ADS)

    Beniest, Anouk; Sassi, William; Xavier, Guichet; Matenco, Liviu; Burov, Evgueni

    2016-04-01

    The formation of sedimentary basins in a purely extensional setting is traditionally related to active tectonic processes during the syn-rift phase and passive processes such as thermal subsidence during the post-rift phase. In a purely extensional setting there is no room for uplift events. However, on seismic data unconformities are observed and interpreted as such, but they cannot be placed in a fully extensional setting. A seismic data base of the South Atlantic conjugate margins consisting only of already published seismic lines has given us the natural laboratory. Here, sedimentary basins show unconformities in their post-rift phase. Traditionally, the South Atlantic conjugate margins are thought to have undergone a considerably easy evolution, but recent interest and subsequent investigations in the region have proved this wrong. We investigate the possibility of a mechanism that couples mantle-dynamics with surface processes. The aim is to explain the unconformities observed on seismic data in marginal basins that have formed under an extensional stress regime. We propose that a laterally migrating thermal anomaly could result in the temporary uplift of marginal basins during their post-rift phase, thereby creating an unconformity. With the use of a 2D numerical, thermo-mechanical code, we tested several parameters that could be of influence on the evolution of the topography. Thirty-six tests have been performed, varying the initial geometry, extensional velocity and the initial location of the thermal anomaly. Our models show that all three parameters influence the formation of marginal basins and their vertical movements to different extends. The initial geometry of the lithosphere appears to control the direction in which the thermal anomaly is migrating. Even when the anomaly is 100's of kilometers away from the break-up point, it migrates towards the region where break-up eventually occurs. Local, temporary, vertical movement of marginal basins is

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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

  9. Death Valley turtlebacks: Mesozoic contractional structures overprinted by Cenozoic extension and metamorphism beneath syn-extensional plutons

    NASA Astrophysics Data System (ADS)

    Pavlis, T. L.; Miller, M.; Serpa, L.

    2008-07-01

    The term turtleback was first coined to describe the curvilinear fault surfaces that produced a distinctive geomorphic form in the Black Mountains east of Death Valley, and although it was decades before their full significance was appreciated, they remain one of the most distinctive features of the extensional structure of the Death Valley region. Historically the interpretation of the features has varied markedly, and misconceptions about their character continue to abound, including descriptions in popular field guides for the area. It the 1990's, however, the full history of the systems began to be apparent from several key data: 1) the dating of the plutonic assemblage associated with the turtlebacks demonstrated that late Miocene, syn-extensional plutonism was fundamental to their formation; 2) the plutonic assemblage forms an intrusive sheet structurally above the turtlebacks, indicating a tie between much of the high grade metamorphism and Cenozoic plutonism; 3) a modern analog for the syn-extensional plutonism in the Black Mountains was recognized beneath Death Valley with the imaging of a mid-crustal magma body; 4) the Neogene structural history was worked out in the turtlebacks showing that folding of early-formed shear zones formed the turtleback anticlinoria but overprinting by brittle faults produced the final form as they cut obliquely across the older structure; and 5) the pre-extensional structural history was clarified, demonstrating that Mesozoic basement-involved thrust systems are present within the turtlebacks, but have been overprinted by the extensional system. An unresolved issue is the significance of Eocene U-Pb dates for pegmatites within the region, but presumably these relate somehow to the pre-extensional history. Miller and Pavlis (2005; E. Sci. Rev.) reviewed many features of the turtlebacks, and our working model for the region is that the turtlebacks originated as mid-crustal ductile-thrust systems within the Cordilleran fold

  10. Late Quaternary Arc-parallel Extension of the Kongur Extensional System (KES), Chinese Pamir

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Schoenbohm, Lindsay M.; Yuan, Zhaode; Li, Wenqiao; Li, Tao; Owen, Lewis A.; Sobel, Edward R.; Hedrick, Kate

    2015-04-01

    Active deformation in the Chinese Pamir plateau is dominated by east-west extension along the active Kongur extensional system (KES). The KES lies along the northeastern margin of the Pamir at the western end of the Himalayan-Tibetan orogenic belt, and is part of a regional fault system which accommodates east-west extension in the hanging wall of the active Main Pamir Thrust (MPT). Previous work has shown that the MPT has been active since at least the Late Oligocene and accommodates northward motion of the Pamir salient over the Tarim and Tajik basins. It has been proposed that North-directed thrusting along the Main Pamir thrust has been interpreted to be related to east-west extension in the northern Pamir by either extensional collapse of over-thickened crust, or radial thrusting, or oroclinal bending along the Main Pamir Thrust. Alternatively, the east-west extension is related to northward propagation of the right-slip Karakoram fault. A newer model relates the extension to gravitational collapse of the Pamir into the Tadjik depression. Clearly the precise driver remains poorly understood. To better understand the nature of extension in the Pamir and to test the existing models, late Quaternary slip rate along the KES need to be defined using geomorphic mapping, geodetic surveying, Be-10 surface exposure and depth profile dating to quantify rates of fault slip using multiple landforms as strain markers such as offset outwash terraces, lateral moraines, and landslides at five sites, to identify spatial patterns in deformation rates. The preliminary results show that the overall extension direction is subhorizontal, is oriented E-W, and occurs at a high rate of about 7 mm/yr along the Muji and Qimugan faults to the north and deceased to about 1 mm/yr at Kuzigan to the south near Tashkurgan town, which matches the pattern of GPS data. A regional compilation from this study and existing data shows that recent extension along the KES is arc-parallel extension

  11. Droplet Deformation in an Extensional Flow: The Role of Surfactant Physical Chemistry

    NASA Technical Reports Server (NTRS)

    Stebe, Kathleen J.

    1996-01-01

    Surfactant-induced Marangoni effects strongly alter the stresses exerted along fluid particle interfaces. In low gravity processes, these stresses can dictate the system behavior. The dependence of Marangoni effects on surfactant physical chemistry is not understood, severely impacting our ability to predict and control fluid particle flows. A droplet in an extensional flow allows the controlled study of stretching and deforming interfaces. The deformations of the drop allow both Marangoni stresses, which resist tangential shear, and Marangoni elasticities, which resist surface dilatation, to develop. This flow presents an ideal model system for studying these effects. Prior surfactant-related work in this flow considered a linear dependence of the surface tension on the surface concentration, valid only at dilute surface concentrations, or a non-linear framework at concentrations sufficiently dilute that the linear approximation was valid. The linear framework becomes inadequate for several reasons. The finite dimensions of surfactant molecules must be taken into account with a model that includes surfaces saturation. Nonideal interactions between adsorbed surfactant molecules alter the partitioning of surfactant between the bulk and the interface, the dynamics of surfactant adsorptive/desorptive exchange, and the sensitivity of the surface tension to adsorbed surfactant. For example, cohesion between hydrocarbon chains favors strong adsorption. Cohesion also slows the rate of desorption from interfaces, and decreases the sensitivity of the surface tension to adsorbed surfactant. Strong cohesive interactions result in first order surface phase changes with a plateau in the surface tension vs surface concentration. Within this surface concentration range, the surface tension is decoupled from surface concentration gradients. We are engaged in the study of the role of surfactant physical chemistry in determining the Marangoni stresses on a drop in an extensional

  12. Numerical simulations of tsunamis generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrová, M.; Paris, R.; Kelfoun, K.; Nomikou, P.

    2014-02-01

    Increasing human activities along the coasts of the world provoke the necessity to assess tsunami hazard from different sources (earthquakes, landslides, volcanic activity). In this paper, we simulate tsunamis generated by underwater volcanic explosions from (1) a submerged vent in a shallow water lake (Karymskoye Lake, Kamchatka), and (2) from Kolumbo submarine volcano (7 km NE of Santorini, Aegean Sea, Greece). The 1996 tsunami in Karymskoye lake is a well-documented example and thus serves as a case study for validating the calculations. The numerical model reproduces realistically the tsunami run-ups measured onshore. Systematic numerical study of tsunamis generated by explosions of the Kolumbo volcano is then conducted for a wide range of energies. Results show that in case of reawakening, the Kolumbo volcano might represent a significant tsunami hazard for the northern, eastern and southern coasts of Santorini, even for small-power explosions.

  13. Numerical simulations of tsunami generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrová, M.; Paris, R.; Kelfoun, K.; Nomikou, P.

    2013-11-01

    Increasing human activities along the coasts of the world arise the necessity to assess tsunami hazard from different sources (earthquakes, landslides, volcanic activity). In this paper, we simulate tsunamis generated by underwater volcanic explosions from (1) a submerged vent in a shallow water lake (Karymskoye Lake, Kamchatka), and (2) from Kolumbo submarine volcano (7 km NE of Santorini, Aegean Sea, Greece). The 1996 tsunami in Karymskoye lake is a well-documented example and thus serves as a case-study for validating the calculations. The numerical model reproduces realistically the tsunami runups measured onshore. Systematic numerical study of tsunamis generated by explosions of Kolumbo volcano is then conducted for a wide range of energies. Results show that in case of reawakening, Kolumbo volcano might represent a significant tsunami hazard for the northern, eastern and southern coasts of Santorini, even for small-power explosions.

  14. Effects of fragmentation on genetic diversity in island populations of the Aegean wall lizard Podarcis erhardii (Lacertidae, Reptilia).

    PubMed

    Hurston, H; Voith, L; Bonanno, J; Foufopoulos, J; Pafilis, P; Valakos, E; Anthony, N

    2009-08-01

    Landbridge islands offer unique opportunities for understanding the effects of fragmentation history on genetic variation in island taxa. The formation of islands by rising sea levels can be likened to a population bottleneck whose magnitude and duration is determined by island area and time since isolation, respectively. The Holocene landbridge islands of the Aegean Sea (Greece) were formed since the last glacial maximum and constitute an ideal system for disentangling the effects of island area, age and geographic isolation on genetic variability. Of the many reptile species inhabiting this island system, the Aegean wall lizard Podarcis erhardii is an excellent indicator of fragmentation history due to its widespread distribution and poor over-water dispersal abilities. In this study, we utilize a detailed record of Holocene fragmentation to investigate the effects of island history on wall lizard mitochondrial and nuclear microsatellite diversity. Findings show that the spatial distribution of mitochondrial haplotypes reflects historical patterns of fragmentation rather than geographic proximity per se. In keeping with neutral bottleneck theory, larger and younger islands retain more nuclear genetic variation than smaller, older islands. Conversely, there is no evidence of an effect of isolation by distance or effect of distance to the nearest larger landmass on genetic variability, indicating little gene flow between islands. Lastly, population-specific measures of genetic differentiation are inversely correlated with island area, suggesting that smaller islands exhibit greater divergence due to their greater susceptibility to drift. Taken together, these results suggest that both island area and time since isolation are important predictors of genetic variation and that these patterns likely arose through the progressive fragmentation of ancestral diversity and the ensuing cumulative effects of drift.

  15. Forecasting skill assessment of an oil spill simulation system in the NE Aegean and atmospheric forcing perturbation experiments

    NASA Astrophysics Data System (ADS)

    Kailas, Marios; Chrysagi, Eyrydice; Sofianos, Sarantis

    2016-04-01

    In the present study, the predictive skill of an oil spill simulation system implemented in the Northern Aegean Sea was evaluated using field observations from surface drifters, provided in the framework of the TOSCA project. The system produces satisfactory results as in most cases the forecasting error is quite small, allowing the operational use of the forecast. In order to examine the sensitivity of the forecast to atmospheric forcing, additional simulations with perturbed atmospheric conditions were performed, using a time-shifting technique. In most experiments the differences between the simulations are relatively small, most likely due to slow oceanic response to variations in the wind fields. From the individual simulations an ensemble forecast was created, the results of which were also compared with the observations. The results suggest that by applying this method a safer forecast can be provided, especially regarding cases for which the wind-driven circulation is predominant. However, in cases where the circulation is characterized by intense velocity gradients (in the NE Aegean this is associated with the thermohaline front created by the Black Sea Water inflow), larger differences are present. They are related to imprecise representation of the location of the front. In these cases, the ensemble method produced no significant improvement since the relatively small differences between the trajectories of the ensemble members indicate that the position of the front in not significantly affected by the wind perturbations, based on the spatio-temporal scales examined. It is concluded that in regions with large spatio-temporal variability, an ensemble forecast produced by simulations generated from perturbed initial conditions could possibly lead to more robust results.

  16. Inferences on the Mesozoic evolution of the North Aegean from the isotopic record of the Chalkidiki block

    NASA Astrophysics Data System (ADS)

    Kydonakis, Konstantinos; Brun, Jean-Pierre; Poujol, Marc; Monié, Patrick; Chatzitheodoridis, Elias

    2016-07-01

    The Chalkidiki block is a major domain in the North Aegean that, contrary to other domains in the region, largely escaped thermal perturbations during Tertiary extension. As a result, the Chalkidiki block is an ideal candidate to glean information related to the timing of Mesozoic thermal events using appropriate geochronological techniques. We have undertaken a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) study (U-Th-Pb on monazites and U-Pb on zircons) coupled with 40Ar/39Ar dating on nine samples from various structural levels within the thrust system of the Chalkidiki block. The eastern, and structurally lower part of the system revealed a complete isotopic reset of Carboniferous - Early Triassic monazites coeval with partial monazite destruction, REE-mobilisation and formation of apatite-allanite-epidote coronas at ~ 132 Ma, a reaction that is commonly observed in amphibolite-facies rocks. These coronas formed after crystallisation of garnet (i.e., at T > 580 °C) and, in all probability, either close to the peak-temperature conditions (~ 620 °C) on a prograde path or during retrogression between the peak-temperature and the low-temperature boundary of the amphibolite facies. Cooling of these rocks and arrival at mid-crustal levels occurred at 95-100 Ma. By contrast, the western, and structurally uppermost part of the system went through the same event by 120-125 Ma. Further structural considerations with respect to medium-temperature geochronology data imply that syn-metamorphic thrusting must have ceased by early Late Cretaceous. We emphasize that, with the sole exception of the Chalkidiki block, no pre-45 Ma medium-temperature geochronology data are preserved in other North Aegean domains, a feature that is clearly related to the extension-induced thermal perturbation of the region during the Tertiary.

  17. Geographic patterns of elemental deposition in the Aegean region of Turkey indicated by the lichen, Xanthoria parietina (L.) Th. Fr.

    PubMed

    Yenisoy-Karakaş, S; Tuncel, S G

    2004-08-15

    Lichen samples from different parts of the world have been known to accumulate elements to a greater degree than higher plants, if they are exposed to these elements from the atmosphere or from water and sediments. It has been hypothesized that lichens can be used to monitor air pollution around point and area emission sources. Local variation (variation in substrate, age and morphology of lichen samples) of element concentrations would not be large enough to affect the concentration patterns in large areas. We tested this hypothesis in the Aegean region of Turkey, which is very urbanized and industrialized. No such study has been conducted before in this part of the country. A total of 234 samples of the lichen Xanthoria parietina were collected from a 51,800-km2 area. Samples were washed and analyzed by INAA and ICP-AES for 35 elements. The range of the concentrations for most of the elements on a local scale was an order of magnitude lower than for the element concentrations on a regional scale. The mean local coefficient of variance (CV) was found to be 15, providing that the local variation did not affect the concentration of elements in the sampling region. According to cluster analysis, 8 (As, Hg, Pb, Sb, Fe, Mn, Na and K) elements are indicative of important local pollution locations and their zone of impact in the region. By mapping the concentrations of eight indicative elements in lichen Xanthoria parietina of the Aegean region, it was possible to relate deposition to the existence of known sources of pollution in certain areas. Location of pollution sources such as iron-steel plants, and coal burning in the cities, industrial activity and two important coal-fired power plants generally corresponded with locations of highest element accumulations in the lichens.

  18. Salt diapirs in the Dead Sea basin and their relationship to Quaternary extensional tectonics

    USGS Publications Warehouse

    Al-Zoubi, A.; ten Brink, U.S.

    2001-01-01

    Regional extension of a brittle overburden and underlying salt causes differential loading that is thought to initiate the rise of reactive diapirs below and through regions of thin overburden. We present a modern example of a large salt diapir in the Dead Sea pull-apart basin, the Lisan diapir, which we believe was formed during the Quaternary due to basin transtension and subsidence. Using newly released seismic data that are correlated to several deep wells, we determine the size of the diapir to be 13 x 10 km. its maximum depth 7.2 km. and its roof 125 m below the surface. From seismic stratigraphy, we infer that the diapir started rising during the early to middle Pleistocene as this section of the basin underwater rapid subsidence and significant extension of the overburden. During the middle to late Pleistocene, the diapir pierced through the extensionally thinned overburden, as indicated by rim synclines, which attest to rapid salt withdrawal from the surrounding regions. Slight positive topography above the diapir and shallow folded horizons indicate that it is still rising intermittently. The smaller Sedom diapir, exposed along the western bounding fault of the basin is presently rising and forms a 200 m-high ridge. Its initiation is explained by localized E-W extension due monoclinal draping over the edge of a rapidly subsiding basin during the early to middle Pleistocene, and its continued rise by lateral squeezing due to continued rotation of the Amazyahu diagonal fault. ?? 2001 Elsevier Science Ltd. All rights reserved.

  19. Marangoni Effects of a Drop in an Extensional Flow: The Role of Surfactant Physical Chemistry

    NASA Technical Reports Server (NTRS)

    Stebe, Kathleen J.; Balasubramaniam, R. (Technical Monitor)

    2002-01-01

    While the changes in stresses caused by surfactant adsorption on non-deforming interfaces have been fairly well established, prior to this work, there were few studies addressing how surfactants alter stresses on strongly deforming interfaces. We chose the model problem of a drop in a uniaxial extensional flow to study these stress conditions To model surfactant effects at fluid interfaces, a proper description of the dependence of the surface tension on surface concentration, the surface equation of state, is required. We have adopted a surface equation of state that accounts for the maximum coverage limit; that is, because surfactants have a finite cross sectional area, there is an upper bound to the amount of surfactant that can adsorb in a monolayer. The surface tension reduces strongly only when this maximum coverage is approached. Since the Marangoni stresses go as the derivative of the surface equation of state times the surface concentration gradient, the non-linear equation of state determines both the effect of surfactants in the normal stress jump, (which is balanced by the product of the mean curvature of the interface times the surface tension), and the tangential stress jump, which is balanced by Marangoni stresses. First, the effects of surface coverage and intermolecular interactions among surfactants which drive aggregation of surfactants in the interface were studied. (see Pawar and Stebe, Physics of Fluids).

  20. Nonlinear flap-lag-extensional vibrations of rotating, pretwisted, preconed beams including Coriolis effects

    NASA Technical Reports Server (NTRS)

    Subrahmanyam, K. B.; Kaza, K. R. V.

    1985-01-01

    The effects of pretwist, precone, setting angle, Coriolis forces and second degree geometric nonlinearities on the natural frequencies, steady state deflections and mode shapes of rotating, torsionally rigid, cantilevered beams were studied. The governing coupled equations of flap lag extensional motion are derived including the effects of large precone and retaining geometric nonlinearities up to second degree. The Galerkin method, with nonrotating normal modes, is used for the solution of both steady state nonlinear equations and linear perturbation equations. Parametric indicating the individual and collective effects of pretwist, precone, Coriolis forces and second degree geometric nonlinearities on the steady state deflection, natural frequencies and mode shapes of rotating blades are presented. It is indicated that the second degree geometric nonlinear terms, which vanish for zero precone, can produce frequency changes of engineering significance. Further confirmation of the validity of including those generated by MSC NASTRAN. It is indicated that the linear and nonlinear Coriolis effects must be included in analyzing thick blades. The Coriolis effects are significant on the first flatwise and the first edgewise modes.

  1. Microbial Communities of Terrestrial Springs in Extensional Settings of the Western U.S.A.

    NASA Astrophysics Data System (ADS)

    Takacs-Vesbach, C.; Hall, J.; Crossey, L. J.; Karlstrom, K. E.; Fischer, T.; Cron, B.

    2008-12-01

    Gas and water chemistry from hot springs, gas vents, travertine-bearing cool springs, and high-pCO2 groundwaters of the western U.S. indicate a regionally extensive flux of deeply sourced volatiles through spring vents. We use the term "continental smokers" to emphasize and test analogs to mid-ocean vent systems, and are currently concentrating on vents in the Rocky Mountain/Colorado Plateau region as part of the Colorado Rockies and Experiment and Seismic transects (CREST). Measurable mantle-derived helium components (3He/4He = 0.10 to 2.1 RA) occur in nearly all springs in Colorado and New Mexico suggesting direct fast fluid pathways from the mantle to the surface hydrologic system. Important components of the CO2 are also derived from the mantle. We surveyed the geochemistry and microbial diversity of more than forty deeply sourced terrestrial springs that ranged in temperatures from 9° to 70°C. We hypothesize that degassing in continental extensional settings supports microbial assemblages that are analogous to chemolithotrophic communities at mid-ocean ridges and continental volcanic hydrothermal systems. Geochemical characteristics of the fluids and gases structure and sustain distinctive geomicrobiological communities as indicated by the widespread presence of archaea and thermophilic organisms in cool as well as hot springs.

  2. Extensional tectonic influence on lower and upper cretaceous stratigraphy and reservoirs, southern Powder River basin, Wyoming

    SciTech Connect

    Mitchell, G.C.; Rogers, M.H.

    1993-04-01

    The southern Powder River basin has been influenced significantly by an extensional system affecting Lower Cretaceous, Upper Cretaceous and Tertiary units. The system is composed of small throw, nearly vertical normal faults which are identified in the Cretaceous marine shales and that we believe are basement derived. Resultant fractures were present at erosional/depositional surfaces, both marine and nonmarine, that, in part, controlled erosion and subsequent deposition of Lower and Upper Cretaceous rocks. The normal faults also affected coal deposition in the Tertiary, now exposed at the surface. The erosion and resultant deposition formed extensive stratigraphic traps in Cretaceous units in both conventional and unconventional reservoirs. These reservoirs are interbedded with mature source rocks that have generated and expelled large amounts of hydrocarbons. Resulting overpressuring in the Fall River through the Niobrara formations has kept fractures open and has preserved primary porosity in the reservoirs. The normal faults offset thin sandstone reservoirs forming permeability barriers. Associated fractures may have provided vertical pathways for organic acids that assisted development of secondary porosity in Upper Cretaceous sandstones. These normal...faults and fractures provide significant potential for the use of horizontal drilling techniques to evaluate fractured, overpressured conventional and unconventional reservoirs.

  3. Late Cretaceous extensional unroofing in the Funeral Mountains metamorphic core complex, California

    SciTech Connect

    Applegate, J.D.R.; Hodges, K.V. ); Walker, J.D. )

    1992-06-01

    New filed and geochronologic data document the existence of Late Cretaceous extensional structures in the Death Valley region, California-Nevada. The authors have mapped two major, low-angle, ductile shear zones that omit stratigraphy in the footwall of the Funeral Mountains metamorphic core complex. Intervening strata have been strongly attenuated. Although stratigraphic offset across the shear zones is only 1.5 km, the presence of a large metamorphic discontinuity suggests that the amount of unroofing must be much greater. The timing of shear-zone formation, attenuation, and subsequent northwest-vergent folding is constrained by U-Pb geochronology on (1) prekinematic or synkinematic and (2) postkinematic pegmatites. Deformation was taking place by 72 Ma and had ended by 70 Ma. These results support earlier petrologic and geochronologic data that suggested substantial unroofing of the Funeral Mountains in Late Cretaceous time and add to a growing body of evidence for widespread Mesozoic extension in the hinterland of the Sevier thrust belt.

  4. Viscous and acoustic losses in length-extensional microplate resonators in liquid media

    NASA Astrophysics Data System (ADS)

    Ruiz-Díez, Víctor; Hernando-García, Jorge; Manzaneque, Tomás; Kucera, Martin; Schmid, Ulrich; Sánchez-Rojas, José Luis

    2015-02-01

    Damping mechanisms in the length-extensional mode of rectangular, mid-point supported microplate resonators immersed in liquid are studied. Piezoelectrically excited structures with different lengths and thicknesses were designed, fabricated, and characterized both optically and electrically in isopropanol. The experimental quality factors were compared to the results of Finite Element Method (FEM) simulations and the two main mechanisms of losses, i.e., acoustic and viscous losses, were identified. Analytical models for those two mechanisms are presented and the effects of the geometry on the in-liquid performance of the resonators are discussed. By applying these models, we found that for a given thickness, a maximum quality factor is reached at a critical length, resulting from the balance between acoustic and viscous losses. To further increase quality factors, a quarter wavelength fluid cavity was implemented, thereby reducing acoustic losses; an increase over 40% in the quality factor was predicted by a 2D FEM model including the cavity, and a quality factor as high as 145 was measured for a 3 mm long and 93 μm thick resonator in this configuration.

  5. Rotation of late Cenozoic extensional stresses, Yucca Flat region, Nevada Test Site, Nevada

    SciTech Connect

    Ander, H.D.

    1984-12-31

    The Nevada Test Site (NTS) is located in the southern Basin and Range where the geology is typified by complexly deformed Paleozoic sedimentary rocks underlying Tertiary and Quaternary volcanics and alluvium all displaced by Cenozoic normal faults. The purpose of this study is to interpret the history of change in Cenozoic extensional stress orientations using ash-flow distributions, surface fault configurations, and slickenside analyses. Extensive drill hole data collected from Yucca Flat within NTS were used to construct isopach and structure contour maps of Cenozoic units occupying the northerly-trending basin. The configuration of these units indicates that the north-south-trending faults controlling present day basin morphology were inactive during deposition of the volcanic rocks from approximately 25 to 11 myBP. However, after 11 myBP, the overlying sedimentary sequence was strongly influenced by these faults and consequent basin development. In particular, an inordinately thick section of late Tertiary and Quaternary alluvium occurs at the southwestern end of Yucca Flat. Southwest-striking faults at the southwestern and of Yucca flat are postulated to be deflected at their northeast ends, becoming continuous with the north-south basin forming fault sets.

  6. Micro-scale extensional rheometry using hyperbolic converging/diverging channels and jet breakup.

    PubMed

    Keshavarz, Bavand; McKinley, Gareth H

    2016-07-01

    Understanding the elongational rheology of dilute polymer solutions plays an important role in many biological and industrial applications ranging from microfluidic lab-on-a-chip diagnostics to phenomena such as fuel atomization and combustion. Making quantitative measurements of the extensional viscosity for dilute viscoelastic fluids is a long-standing challenge and it motivates developments in microfluidic fabrication techniques and high speed/strobe imaging of millifluidic capillary phenomena in order to develop new classes of instruments. In this paper, we study the elongational rheology of a family of dilute polymeric solutions in two devices: first, steady pressure-driven flow through a hyperbolic microfluidic contraction/expansion and, second, the capillary driven breakup of a thin filament formed from a small diameter jet ([Formula: see text]). The small length scale of the device allows very large deformation rates to be achieved. Our results show that in certain limits of low viscosity and elasticity, jet breakup studies offer significant advantages over the hyperbolic channel measurements despite the more complex implementation. Using our results, together with scaling estimates of the competing viscous, elastic, inertial and capillary timescales that control the dynamics, we construct a dimensionless map or nomogram summarizing the operating space for each instrument. PMID:27375824

  7. Mechanical Models of Bed-Perpendicular Fractures in Layered Rocks Subjected to Extensional Strain

    NASA Astrophysics Data System (ADS)

    Sanz, P.; Pollard, D. D.; Borja, R. I.

    2010-12-01

    Natural fractures (joints) enhance permeability and therefore are important for the economical production of low-permeability hydrocarbon reservoirs and aquifers. In this work we investigate the formation of bed-perpendicular joints during extension in a stiff brittle layer surrounded by thick softer layers. The quasi-static finite element models consist of three elasto-plastic layers with frictional bedding interfaces and the middle layer contains layer-perpendicular fractures that can accommodate opening at the bedding surface accompanied by interface sliding. The upper and lower boundaries are subject to normal tractions appropriate for the depth of burial. Lateral boundaries are displaced horizontally to represent the extensional tectonic regime. We use an interface model that captures the most important mechanical features during sliding of bedding interfaces and opening of joints: unilateral contact, elastic and plastic relative deformation, tensile strength, cohesion, frictional sliding, and non-associative plastic flow. The constitutive law extends the Coulomb slip criterion to the tensile regime to capture opening of fractures in a quasi-brittle manner. The finite element implementation employs a penalty scheme to impose the contact constraints along the interfaces. The numerical simulations show the effects of mechanical properties of layers and interfaces in the development and spacing of bed-perpendicular joints. We evaluate the concepts of fracture saturation and sequential infilling, and the relationship between joint spacing and layer thickness in the context of the new modeling capabilities.

  8. Mechanoelectrochemistry of PPy(DBS) from correlated characterization of electrochemical response and extensional strain.

    PubMed

    Northcutt, Robert G; Sundaresan, Vishnu-Baba

    2015-12-28

    This paper investigates nanostructured morphology-dependent charge storage and coupled mechanical strain of polypyrrole membranes doped with dodecylbenzenesulfonate (PPy(DBS)). Nanoscale features introduced in PPy(DBS) using phospholipid vesicles as soft-templates create a uniform and long-range order to the polymer morphology, and lead to higher specific capacitance. It is widely stated that nanostructured architecture offer reduced mechanical loading at higher charge capacities, but metrics and methods to precisely quantify coupled localized strains do not exist. Towards this goal, we demonstrate the use of scanning electrochemical microscope with shear force imaging hardware (SECM-SF) to precisely measure charge storage function and volumetric strain simultaneously, and define two metrics--filling efficiency and chemomechanical coupling coefficient to compare nanostructured morphologies and thicknesses. For thin membranes (smaller charge densities), planar and vesicle-templated membranes have comparable mechanoelectrochemical response. For thick membranes (0.4 to 0.8 C cm(-2)), a 15% increase in charge storage is associated with 50% reduction in extensional strain. These results allow for the formulation of rules to design nanostructured PPy(DBS)-based actuators and energy storage devices. PMID:26583690

  9. Extensional extrusion: Insights into south-eastward expansion of Tibetan Plateau from magnetotelluric array data

    NASA Astrophysics Data System (ADS)

    Dong, Hao; Wei, Wenbo; Jin, Sheng; Ye, Gaofeng; Zhang, Letian; Jing, Jian'en; Yin, Yaotian; Xie, Chengliang; Jones, Alan G.

    2016-11-01

    Despite extensive effort over many decades to understand the tectonic evolution of the Tibetan Plateau, the geodynamic processes creating the iconic south-eastward expansion of the plateau at the Eastern Himalayan Syntaxis (EHS) are still unclear and are hotly debated. Two popular (but not necessarily exclusive) geodynamic models, namely crustal flow at mid-to-lower crustal depths and coherent deformation between the crust and lithospheric mantle, are commonly invoked to explain the expansion mechanism. However, neither of these is able to reconcile all of the abundant geological and geophysical data. Here we present a three-dimensional (3D) geo-electrical model, derived from new SINOPROBE magnetotelluric (MT) array data, that reveals the geo-electrical, and by inference rheological, structure of southeast Tibet. Instead of NW-SE conductive channels proposed in prior two-dimensional (2D) MT studies, distinct NNE-SSW directed quasi-linear conductive anomalies are identified in the mid-to-lower crust, which are separated by a large-scale electrically resistive structure that extends from the crust to the upper mantle. This argues against the prior proposed model of south-eastward conductive anomalies, and hence against the southeast lower crust flow of material. To interpret our observations and resultant model, a new mechanism of "extensional extrusion" is proposed to address the lithospheric deformation of the south-eastward expansion of Tibetan Plateau.

  10. Probable Middle Cambrian and Middle-Late Ordovician seismites, a record of extensional to compressional tectonics

    SciTech Connect

    Pope, M.C.; Read, J.F. . Dept. of Geology)

    1992-01-01

    Facies resembling seismites, in situ shock deformation of sediments related to earthquake activity, appear to be developed in a Middle Cambrian intrashelf basinal setting in Virginia, and in a Middle-Late Ordovician foreland basin setting throughout Virginia and Kentucky. The Middle Cambrian facies developed during Rome trough and Conasauga basin extensional tectonics, whereas the Middle and Late Ordovician examples developed during eastward subduction of the North American plate (Taconic Orogeny). The seismites are characterized by contorted bedding, abundant ball and pillow structures, upward injection of sediment, in-place foundering of large blocks with erosional tops, development of mud-supported chaotic conglomerate fabrics and perhaps compacted sediment filled dikes in shale. The seismites occur in both clastic and carbonate, fine-to-carose grained sediments and vary in scale from centimeters to meters. The contorted bedding probably relates to seismically induced liquefaction of sediments within the upper few meters of section, whereas ball and pillow formation and sediment injection is due to water escape. The low sedimentation rates in the intrashelf basin and on the foreland ramp would tend to preclude these features resulting from high sedimentation rates causing loading of water-rich mud sections, even though some beds related to storm deposition. In fact, most of the storm beds, even thicker ones, show little evidence of ball and pillow formation. Seismites may provide an important temporal record of earthquakes affecting these basins, and need to be recognized if one is to separate tectonic from eustatic effects in these basins.

  11. Extensional rheometer for in situ x-ray scattering study on flow-induced crystallization of polymer

    NASA Astrophysics Data System (ADS)

    Liu, Yanping; Zhou, Weiqing; Cui, Kunpeng; Tian, Nan; Wang, Xiao; Liu, Liangbao; Li, Liangbin; Zhou, Yingui

    2011-04-01

    We designed and constructed an extensional rheometer for in situ small and wide angle x-ray study on flow-induced crystallization of polymer. Two rotating drums with an axis distance of 20 mm are employed to impose extensional deformation on the samples. With a constant angular velocity, the two drums generate a constant Henkcy strain rate as sample length for testing keeps constant during deformation. An ionic liquid is used as heating medium to prevent polymer melt from bending downward due to gravity, which is excellent in terms of high thermal stability, low viscosity, and relative low adsorption on x-ray. Flow-induced crystallization experiments are conducted with this apparatus on x-ray scattering station in Shanghai Synchrotron Radiation Facility (SSRF), which allows us to collect rheological and structural data simultaneously and may lead to a better understanding on flow-induced crystallization of polymer.

  12. Timing of Early Proterozoic collisional and extensional events in the granulite-gneiss-charnockite-granite complex, Lake Baikal, USSR: A U-Pb, Rb-Sr, and Sm-Nd isotopic study

    SciTech Connect

    Aftalion, M. ); Bibikova, E.V. ); Bowes, D.R. ); Hopwood, A.M. ); Perchuk, L.L. )

    1991-11-01

    In the Sharyzhalgay Complex of the Lake Baikal region in eastern Siberia Early Proterozoic collisional and extensional events were separated by ca. 100 m.yr. The earlier collisional event, associated with the development of granulites and gneisses as the result of high-grade dynamothermal metamorphism, took place close to 1965 {plus minus} 4 Ma. A {sup 207}Pb/{sup 204}Pb vs. {sup 206}Pb/{sup 204}Pb isochron for zircon from five size fractions and a six point Rb-Sr whole-rock errorchron give generally corresponding ages of 1956 {plus minus} 8 and 1963 {plus minus} 163 Ma, respectively. The later extensional event, associated with charnockitization due to the uprise of fluids and heat in a regime corresponding to the middle to upper crustal levels of a Basin and Range-type province, was initiated in the 1880-1860 Ma period. The event was continued with magmatic emplacement of granitic masses into the deep levels of caldera-like structures, possibly during the upper time range of lower concordia intercept ages of 1817 +30/{minus}32 and 1797 +40/{minus}44 Ma for two distinctly different zircon populations in a pyroxene-bearing granodiorite interpreted as an evolved (and contaminated) product of the mantle-derived magma that was the source of CO{sub 2} involved in the charnockitization. Upper intercept ages of 2784 +48/{minus}45 and 2775 +61/{minus}55 Ma indicate late Archean crust at depth as the source region of the incorporated zircon. T{sub DM} ages from Sm-Nd isotopic data show that the protolith of the lithologically layered supracrustal assemblage, subsequently polyphase deformed and polymetamorphosed in Early Proterozoic times, was also formed in Early Proterozoic (not Archean) times.

  13. Role of crustal thickening and extensional collapse in the tectonic evolution of the Sevier-Laramide orogeny, western United States

    SciTech Connect

    Livaccari, R.F. )

    1991-11-01

    The effects of crustal thickening and extensional collapse of continental crust, combined with variations in plate-convergence forces, provide a coherent explanation for evolution of the Cretaceous-early Tertiary Sevier-Laramide orogeny. Crustal thickening of the Sevier-Laramide hinterland region was triggered by the combination of compressive plate-convergence forces and subduction-induced conductive heating of the crust. Eastward progradation of the locus of Sevier-Laramide deformation through time reflects the progressive widening of the region of crustal thickening. The region of maximum crustal thickening migrated outward until about 80 to 75 Ma, when it encountered excessively strong lithosphere of the Colorado Plateau. The locus of deformation was then transmitted laterally across both a hinterland that had attained maximum crustal thickness and the rigid Colorado Plateau, into the Laramide Rocky Mountain foreland. An episode of vigorous extensional collapse of orogenically thickened crust affected the southern Cordillera between about 75 and 35 Ma. Early Tertiary waning of plate-convergence rates and continued subduction-induced conductive heating of thickened crust allowed extensional collapse along the southern Cordillera region to drive the Colorado Plateau block northward. The result was the late Laramide phase of Rocky Mountain foreland deformation in the central and southern Laramide Rocky Mountain region continued through Eocene time, rather than ceasing at 56 Ma, as it did in the northern Cordillera.

  14. Extensional deformation structures within a convergent orogen: The Val di Lima low-angle normal fault system (Northern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Clemenzi, Luca; Molli, Giancarlo; Storti, Fabrizio; Muchez, Philippe; Swennen, Rudy; Torelli, Luigi

    2014-09-01

    A low-angle extensional fault system affecting the non metamorphic rocks of the carbonate dominated Tuscan succession is exposed in the Lima valley (Northern Apennines, Italy). This fault system affects the right-side-up limb of a kilometric-scale recumbent isoclinal anticline and is, in turn, affected by superimposed folding and late-tectonic high-angle extensional faulting. The architecture of the low-angle fault system has been investigated through detailed structural mapping and damage zone characterization. Pressure-depth conditions and paleofluid evolution of the fault system have been studied through microstructural, mineralogical, petrographic, fluid inclusion and stable isotope analyses. Our results show that the low-angle fault system was active during exhumation of the Tuscan succession at about 180°C and 5 km depth, with the involvement of low-salinity fluids. Within this temperature - depth framework, the fault zone architecture shows important differences related to the different lithologies involved in the fault system and to the role played by the fluids during deformation. In places, footwall overpressuring influenced active deformation mechanisms and favored shear strain localization. Our observations indicate that extensional structures affected the central sector of the Northern Apennines thrust wedge during the orogenic contractional history, modifying the fluid circulation through the upper crust and influencing its mechanical behavior.

  15. An apparatus for in situ x-ray scattering studies of polymer melts during homogenous uniaxial extensional flow

    NASA Astrophysics Data System (ADS)

    Burghardt, Wesley; Mao, Ruinan

    2011-03-01

    In situ x-ray scattering methods have been broadly applied to study the structural dynamics of polymers and other complex fluids under flow, and can provide deep insights into the microstructural origins of complex non-Newtonian flow characteristics. Most studies in this vein have employed either homogenous shear flow, or processing flows such as fiber spinning which are complicated by inhomogenous deformation histories and/or nonisothermal operation. Here we present the design and implementation of a new apparatus for in situ x-ray scattering studies of polymer melts during homogenous uniaxial extensional flow. The experiment is based on the commercially-available SER extensional flow fixture, which employs two counter- rotating drums to deform a sample strip of polymer melt. This fixture has been incorporated into a custom-fabricated convection oven designed to facilitate x-ray access to the sample, and operation in a typical synchrotron beam line environment. Preliminary data on extensional flow induced orientation of ordered block copolymers will be used to illustrate the capabilities of this device.

  16. Kinetic aspects of the coil-stretch transition of polymer chains in dilute solution under extensional flow

    NASA Astrophysics Data System (ADS)

    Hernández Cifre, J. G.; García de la Torre, J.

    2001-11-01

    When linear polymer chains in dilute solution are subject to extensional flow, each chain in the sample experiences the coil-stretch transition at a different time. Using Brownian dynamics simulation, we have studied the distribution of transition times in terms of the extensional rate and the length of the chains. If instead of time one characterizes the effect of the flow by the accumulated strain, then the distribution and its moments seem to take general forms, independent of molecular weight and flow rate, containing some numerical, universal constants that have been evaluated from the dynamical simulation. The kinetics of the transition, expressed by the time-dependence of the fraction of remaining coils, has also been simulated, and the results for the kinetic rate constant has been rationalized in a manner similar to that used for the transition time. The molecular individualism, characterized in this work by the distribution of transition times, is related to the excess of the applied extensional rate over its critical value, which will determine the transition time and other features of the coil-stretch transition.

  17. Superposed local and regional paleostresses: fault-slip analysis of Neogene extensional faulting near coeval caldera complexes, Yucca Flat, Nevada

    USGS Publications Warehouse

    Minor, S.A.

    1995-01-01

    Numerous reduced stress tensors are computed by multiple inversions of 906 temporally and spatially partitioned fault-slip data from the Yucca Flat region in the southwest Nevada volcannic field to constrain the Neogene paleostress and faulting history and to investigate how the regional tectonic stress field was affected by local caldera magmatism. Perturbed, shalalow (<400 m), pre-11 Ma paleostress configurations, determined west and northwest of present (post-11 Ma) Yucca Flat basin, existed during mild extensional faulting and are attributed to superposition of transient caldera-magmatic stresses on the regional stress field. The stress field has rotated as much as 65?? clockwise since 11 Ma during extensional development of Yucca Flat basin, with most of the rotation and extension occurring before about 8.5 Ma. Results suggest that shallow magmatism and caldera development can strongly alter extensional tectonic stress fields, fault patterns, and slip directions in the uppermost crust out to distances of roughly two magma chamber radii away from a magma body. -from Author

  18. SAXS studies of the structure of a BCC-ordered block copolymer melt subjected to uniaxial extensional flow

    NASA Astrophysics Data System (ADS)

    Burghardt, Wesley; McCready, Erica

    We report in situ small-angle x-ray scattering (SAXS) investigations of a spherically-ordered block copolymer melt with a low styrene content (13%) resulting in spherical polystyrene microdomains ordered in BCC lattice. Melt annealing after clearing above the ODT produces ordered samples that have a macroscopically random orientation distribution of BCC 'grains'. Melt samples are subjected to uniaxial extensional flow in a counter-rotating drum extensional flow fixture housed in an oven with synchrotron x-ray access. During flow, initially isotropic diffraction rings in SAXS patterns become deformed, reflecting distortion of the BCC lattice. Diffracted intensity also concentrates azimuthally, indicating macroscopic alignment of the BCC lattice. There is evidence that extensional flow leads to progressive disordering of the BCC structure, with loss of higher order peaks and the emergence of a diffuse 'halo' of scattering. While the primary diffraction peak is visible in directions parallel and perpendicular to the stretching direction, the deformation of the lattice d-spacing follows affine deformation. Indications of ordering persist to higher strains in samples stretched at higher extension rates, and evidence of affine lattice deformation persists to very high strains (Hencky

  19. Extensional salt tectonics in the partially inverted Cotiella post-rift basin (south-central Pyrenees): structure and evolution

    NASA Astrophysics Data System (ADS)

    López-Mir, Berta; Muñoz, Josep Anton; García-Senz, Jesús

    2015-03-01

    The Cotiella Massif in the south-central Pyrenees hosts upper Cretaceous gravity-driven extensional faults which were developed in the Bay of Biscay-Pyrenean paleorift margin of the Atlantic Ocean. They accommodate up to 6 km of post-rift carbonates above relict upper Triassic salt. Subsequent Pyrenean contractional deformation preserved the main extensional features, but most of the upper Triassic salt was expulsed and then dissolved, leaving little indications of the original salt volume. Nonetheless, several distinctive salt-related features are still recognizable both at outcrop and at basin scale, providing an exposed analogue for salt-floored extensional basins developed on passive margins. Based on field research, we re-interpret the tectonic evolution of the area and suggest that passive diapirs were coeval with gravity-driven extension during the development of the Cotiella basin. The given interpretations are supported with detailed geological maps, original structural data, cross sections and outcrop photographs. The discovery of previously unknown post-rift salt structures in the Cotiella Massif is an extra element to consider in the paleogeographic reconstructions of the upper Cretaceous passive margin of the Bay of Biscay-Pyrenean realm and consequently helps in our understanding of the evolution of current Atlantic-type margins.

  20. SAXS/WAXS studies of flow-induced crystallization of poly(1-butene) in uniaxial extensional flow

    NASA Astrophysics Data System (ADS)

    McCready, Erica; Burghardt, Wesley

    2014-03-01

    We report studies of flow-induced crystallization of poly(1-butene) in uniaxial extensional flow. Flow was produced using an SER extensional flow fixture housed in a custom built convection oven designed to provide x-ray access for in situ studies of polymer structure using synchrotron x-ray scattering techniques. Samples were loaded into the SER fixture, heated well into the melt, and then cooled to a temperature at which quiescent crystallization would be prohibitively slow. A short interval of uniaxial extensional flow was then applied, after which simultaneous wide- and small-angle x-ray scattering (SAXS and WAXS) patterns were collected to study the phase transformation kinetics and morphology of the subsequent accelerated crystallization. The degree of crystallite orientation was generally found to decrease over the course of the crystallization. WAXS measurements yielded systematically higher degrees of crystallite orientation than SAXS. Both SAXS and WAXS gave generally consistent results for the extent of crystallization, although the SAXS invariant showed a decrease at long times that is not mirrored in the WAXS data. The impact of both deformation rate and total applied strain on the crystallization process were examined.

  1. The rift architecture and extensional tectonics of the South China Sea

    NASA Astrophysics Data System (ADS)

    Cameselle, Alejandra L.; Ranero, César R.; Barckhausen, Udo; Franke, Dieter

    2016-04-01

    Non-volcanic rifted continental margins are classically described as the product of lithospheric stretching and breakup leading to mantle exhumation, and subsequent seafloor spreading. However, recent studies question this model and indicate a wider range of structural evolutions, that challenge the existing model (e.g. Australia-Antarctic Rift System (Direen et al. 2007, 2011); the Tyrrhenian basin (Prada et al., 2014) or the South China Sea (Cameselle et al. 2015)). Rifting in the South China Sea developed from a series of extensional events, from early Eocene to Late Oligocene, resulting in a V-shape oceanic basin affected by the occurrence of several spreading centers, ridges, transform faults and post-spreading volcanism. In recent years, this marginal basin - the largest in East Asia - has increasingly become one of the key sites for the study of rifting and continental break-up. Its relative small size - compared to many classic, Atlantic-type continental margin settings - allows to easily match conjugated rifted margins and its relative youth promotes the preservation of its original nature. To examine the rifting evolution of the South China Sea, we have reprocessed with modern algorithms multichannel seismic profiles acquired during Sonne49 and BGR84 cruises across the three major subbasins: NW, SW and East subbasins. State-of-the-art of processing techniques have been used to increase the signal to noise ratio, including Tau-P and Wiener predictive deconvolution, multiple attenuation by both radon filtering and wave-equation-based surface-related multiple elimination (SRME) and time migration. To complement seismic interpretation, available vintage multichannel seismic data have been reprocessed with a post-stack flow, including Wiener deconvolution, FK-filtering, space and time variant band-pass filter and time migration. The improving quality of the seismic images shows a range of features including post-rift and syn-rift sediments, the structure of

  2. Tectonic and gravity extensional collapses in overpressured cohesive and frictional wedges

    NASA Astrophysics Data System (ADS)

    Yuan, X. P.; Leroy, Y. M.; Maillot, B.

    2015-03-01

    Two modes of extensional collapse in a cohesive and frictional wedge of arbitrary topography, finite extent, and resting on an inclined weak décollement are examined by analytical means. The first mode consists of the gravitational collapse by the action of a half-graben, rooting on the décollement and pushing seaward the frontal part of the wedge. The second mode results from the tectonics extension at the back wall with a similar half-graben kinematics and the landward sliding of the rear part of the wedge. The predictions of the maximum strength theorem, equivalent to the kinematic approach of limit analysis and based on these two collapse mechanisms, not only match exactly the solutions of the critical Coulomb wedge theory, once properly amended, but generalizes them in several aspects: wedge of finite size, composed of cohesive material and of arbitrary topography. This generalization is advantageous to progress in our understanding of many laboratory experiments and field cases. For example, it is claimed from analytical results validated by experiments that the stability transition for a cohesive, triangular wedge occurs with the activation of the maximum length of the décollement. It is shown that the details of the topography, for the particular example of the Mejillones peninsula (North Chile) is, however, responsible for the selection of a short length-scale, dynamic instability corresponding to a frontal gravitational instability. A reasonable amount of cohesion is sufficient for the pressures proposed in the literature to correspond to a stability transition and not with a dynamically unstable state.

  3. Hydrothermal dolomitization of basinal deposits controlled by a synsedimentary fault system in Triassic extensional setting, Hungary

    NASA Astrophysics Data System (ADS)

    Hips, Kinga; Haas, János; Győri, Orsolya

    2016-06-01

    Dolomitization of relatively thick carbonate successions occurs via an effective fluid circulation mechanism, since the replacement process requires a large amount of Mg-rich fluid interacting with the CaCO3 precursor. In the western end of the Neotethys, fault-controlled extensional basins developed during the Late Triassic spreading stage. In the Buda Hills and Danube-East blocks, distinct parts of silica and organic matter-rich slope and basinal deposits are dolomitized. Petrographic, geochemical, and fluid inclusion data distinguished two dolomite types: (1) finely to medium crystalline and (2) medium to coarsely crystalline. They commonly co-occur and show a gradual transition. Both exhibit breccia fabric under microscope. Dolomite texture reveals that the breccia fabric is not inherited from the precursor carbonates but was formed during the dolomitization process and under the influence of repeated seismic shocks. Dolomitization within the slope and basinal succession as well as within the breccia zones of the underlying basement block is interpreted as being related to fluid originated from the detachment zone and channelled along synsedimentary normal faults. The proposed conceptual model of dolomitization suggests that pervasive dolomitization occurred not only within and near the fault zones. Permeable beds have channelled the fluid towards the basin centre where the fluid was capable of partial dolomitization. The fluid inclusion data, compared with vitrinite reflectance and maturation data of organic matter, suggest that the ascending fluid was likely hydrothermal which cooled down via mixing with marine-derived pore fluid. Thermal gradient is considered as a potential driving force for fluid flow.

  4. Structural control of geothermal reservoirs in extensional tectonic settings: An example from the Upper Rhine Graben

    NASA Astrophysics Data System (ADS)

    Meixner, Jörg; Schill, Eva; Grimmer, Jens C.; Gaucher, Emmanuel; Kohl, Thomas; Klingler, Philip

    2016-01-01

    In extensional tectonic settings major structural elements such as graben boundary faults are typically oriented subparallel to the maximum horizontal stress component SHmax. They are often structurally accompanied by transfer zones that trend subparallel to the extension direction. In the Upper Rhine Graben, such transfer faults are typically characterized by strike-slip or oblique-slip kinematics. A major re-orientation of the regional stress field by up to 90° of the Upper Rhine Graben in the Early Miocene led to the present-day normal and strike-slip faulting regimes in the North and South of the Upper Rhine Graben, respectively, and a transition zone in-between. Consequently, conditions for fault frictional failure changed significantly. Moreover, it has been observed during tracer and stimulation experiments that such transfer faults may be of major importance for the hydraulic field of geothermal reservoirs under the present stress condition, especially, when located between production and injection well. In this context we have investigated slip and dilation tendencies (TS and TD) of major structural elements at reservoir scale for two representative geothermal sites, Bruchsal (Germany) and Riehen (Switzerland), located close to the Eastern Main Boundary Fault of the Upper Rhine Graben. We have evaluated the quality and uncertainty range of both tendencies with respect to potential variation in SHmax orientation. Despite significant differences in orientation of the structures and the stress regimes, the resulting variation of TS and TD reveal major similarities concerning the reactivation potential of both, the graben-parallel structures and the transfer faults. The conditions of criticality for tensile failure and non-criticality for shear failure suggest that transfer faults are most likely naturally permeable structures with low stimulation potential. This is in agreement with the absence of both immediate tracer recovery and seismicity in the studied

  5. Extensional Tectonics Evidenced in Recent Sediments of Lake Van, Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Sengul, M. Alper; Koral, Hayrettin; Elmas, M. Ali

    2016-04-01

    The Lake Van region is characterized by NE-SW trending faults with a left-lateral normal-slip component, NW-SE trending faults with a right-lateral normal-slip component and E-W trending reverse/thrust-slip faults, suggesting a N-S trending compressional stress orientation. Tectonic effects in the region continue to be manifested by recent seismicity as in the earthquake of October 23, 2011 (Mw=7.1). Although this earthquake has not produced many earthquake-related surface deformation, evidences of recent tectonics are rather extensive in the Quaternary sediments surrounding the lake. Therefore ages of sediments are important in determining the timing of tectonic activity. Optically stimulated luminescence (OSL) method was used to determine the age of lake sediments to the north of the lake. Also, shells of gastropods available in the sediments are dated by C14. Ages suggest that to the NE of Lake Van youngest activity on the NW-SE trending Erciş Fault with right-lateral normal-slip component is to be 34 ka. Activity on other normal faults in the same area is dated between 10-14 ka and 20 ka. Also, samewhat to the south of this region in vicinity of the Canik area, reverse faulting is dated to be younger than 40 ka. All ages indicate the region has been affected during the Pleistocene locally by an extensional regime contemporaneously with the contractional regime. The evidence of a one meter dip-slip displacement measured on a fault plane in a quarry supports the view of local extension in the NE sector of the lake. Key Words: Lake Van, OSL dating, neotectonics, active tectonics

  6. Single-molecule sequence detection via microfluidic planar extensional flow at a stagnation point

    PubMed Central

    Dylla-Spears, Rebecca; Townsend, Jacqueline E.; Jen-Jacobson, Linda; Sohn, Lydia L.; Muller, Susan J.

    2012-01-01

    We demonstrate the use of a microfluidic stagnation point flow to trap and extend single molecules of double-stranded (ds) genomic DNA for detection of target sequences along the DNA backbone. Mutant EcoRI-based fluorescent markers are bound sequence-specifically to fluorescently labeled ds λ-DNA. The marker-DNA complexes are introduced into a microfluidic cross slot consisting of flow channels that intersect at ninety degrees. Buffered solution containing the marker-DNA complexes flows in one channel of the cross slot, pure buffer flows in the opposing channel at the same flow rate, and fluid exits the two channels at ninety degrees from the inlet channels. This creates a stagnation point at the center of a planar extensional flow, where marker-DNA complexes may be trapped and elongated along the outflow axis. The degree of elongation can be controlled using the flow strength (i.e., a non-dimensional flow rate) in the device. Both the DNA backbone and the markers bound along the stretched DNA are observed directly using fluorescence microscopy and the location of the markers along the DNA backbone is measured. We find that our method permits detection of each of the five expected target site positions to within 1.5 kb with standard deviations of <1.5 kb. We compare the method’s precision and accuracy at molecular extensions of 68% and 88% of the contour length to binding distributions from similar data obtained via molecular combing. We also provide evidence that increased mixing of the sample during binding of the marker to the DNA improves binding to internal target sequences of dsDNA, presumably by extending the DNA and making the internal binding sites more accessible. PMID:20358051

  7. Foraminifera eco-biostratigraphy of the southern Evoikos outer shelf, central Aegean Sea, during MIS 5 to present

    NASA Astrophysics Data System (ADS)

    Drinia, Hara; Antonarakou, Assimina; Tsourou, Theodora; Kontakiotis, George; Psychogiou, Maria; Anastasakis, George

    2016-09-01

    The South Evoikos Basin is a marginal basin in the Aegean Sea which receives little terrigenous supply and its sedimentation is dominated by hemipelagic processes. Late Quaternary benthic and planktonic foraminifera from core PAG-155 are investigated in order to understand their response to the glacial-interglacial cycles in this region. The quantitative analysis of planktonic foraminifera, coupled with accelerator mass spectrometry (14C-AMS) radiocarbon date measurements, provide an integrated chrono-stratigraphic time framework over the last 90 ka (time interval between late Marine Isotopic Stages 5 and 1; MIS5-MIS1). The temporary appearance and disappearance as well as several abundance peaks in the quantitative distribution of selected climate-sensitive planktonic species allowed the identification of several eco-bioevents, useful to accurately mark the boundaries of the eco-biozones widely recognized in the Mediterranean records and used for large-scale correlations. The established bio-ecozonation scheme allows a detailed palaecological reconstruction for the late Pleistocene archive in the central Aegean, and furthermore provides a notable contribution for palaeoclimatic studies, facilitating intercorrelations between various oceanographic basins. The quantitative analyses of benthic foraminifera identify four distinct assemblages, namely Biofacies: Elphidium spp., Haynesina spp. Biofacies, characterized by neritic species, dominated during the transition from MIS 5 to MIS 4; Cassidulina laevigata/carinata Biofacies dominated till 42 ka (transgressive trend from MIS 4 to MIS 3); Bulimina gibba Biofacies dominated from 42 ka to 9.5 ka (extensive regression MIS 3,2 through lowstand and early transgression; beginning of MIS 1); Bulimina marginata, Uvigerina spp. Biofacies dominated from 9.5 ka to the present (late transgression through early highstand; MIS 1)., This study showed that the South Evoikos Basin which is characterized by its critical depths and

  8. Intensity of joints associated with an extensional fault zone: an estimation by poly3d .

    NASA Astrophysics Data System (ADS)

    Minelli, G.

    2003-04-01

    The presence and frequency of joints in sedimentary rocks strongly affects the mechanical and fluid flow properties of the host layers. Joints intensity is evaluated by spacing, S, the distance between neighbouring fractures, or by density, D = 1/S. Joint spacing in layered rocks is often linearly related to layer thickness T, with typical values of 0.5 T < S < 2.0 T . On the other hand, some field cases display very tight joints with S << T and nonlinear relations between spacing and thickness , most of these cases are related to joint system “genetically” related to a nearby fault zone. The present study by using the code Poly3D (Rock Fracture Project at Stanford), numerically explores the effect of the stress distribution in the neighbour of an extensional fault zone with respect to the mapped intensity of joints both in the hanging wall and in the foot wall of it (WILLEMSE, E. J. M., 1997; MARTEL, S. J, AND BOGER, W. A,; 1998). Poly3D is a C language computer program that calculates the displacements, strains and stresses induced in an elastic whole or half-space by planar, polygonal-shaped elements of displacement discontinuity (WILLEMSE, E. J. M., POLLARD, D. D., 2000) Dislocations of varying shapes may be combined to yield complex three-dimensional surfaces well-suited for modeling fractures, faults, and cavities in the earth's crust. The algebraic expressions for the elastic fields around a polygonal element are derived by superposing the solution for an angular dislocation in an elastic half-space. The field data have been collected in a quarry located close to Noci town (Puglia) by using the scan line methodology. In this quarry a platform limestone with a regular bedding with very few shale or marly intercalations displaced by a normal fault are exposed. The comparison between the mapped joints intensity and the calculated stress around the fault displays a good agreement. Nevertheless the intrinsic limitations (isotropic medium and elastic behaviour

  9. Ductile strain rate recorded in the Symvolon syn-extensional plutonic body (Rhodope core complex, Greece)

    NASA Astrophysics Data System (ADS)

    Cirrincione, Rosolino; Fazio, Eugenio; Ortolano, Gaetano; Fiannacca, Patrizia; Kern, Hartmut; Mengel, Kurt; Pezzino, Antonino; Punturo, Rosalda

    2016-04-01

    Sciences, 90 (1), 77-87. • Punturo, R., Cirrincione, R., Fazio, E., Fiannacca, P., Kern, H., Mengel, K., Ortolano G., and Pezzino, A. (2014). Microstructural, compositional and petrophysical properties of mylonitic granodiorites from an extensional shear zone (Rhodope Core complex, Greece). Geological Magazine, 151 (6), 1051-1071.

  10. Displacement Addition on Linking Extensional Fault Arrays in the Canyonlands Graben, Utah

    NASA Astrophysics Data System (ADS)

    Commins, D. C.; Gupta, S.; Cartwright, J. A.; Phillips, W. M.

    2003-12-01

    Studies of brittle fault populations over the past decade have revealed that large extensional faults grow by the lengthening, interaction and physical linkage of en echelon fault segments. However, the temporal evolution of displacement accumulation during segment interaction and linkage is difficult to unravel due to a lack of direct observation during each stage in the fault array development. The process of profile re-adjustment prevents reconstruction of the growth history of a fault from its final configuration, and as a result, several models for the growth trajectory of a fault array undergoing linkage are possible. Observational data with which to constrain the relative timing and mode of displacement accumulation during the linkage process are currently lacking. We use the deformation of late Pleistocene-Holocene stream systems by the growth of a active normal faults in The Grabens, Canyonlands National Park, Utah to constrain the mode of growth of fault arrays. Coupling fault displacement data with geomorphic analysis of deformed present-day and palaeo-streams, permits sequential reconstruction of both simple 2-segment fault arrays and complex multi-segment populations from their initial component segments to the present day displacement geometry. In particular, these data provide information on the relative rates of displacement addition. For example, the presence of waterfalls where streams cross fault scarps indicates abrupt rates of displacement accumulation which we can relate to the hard linkage process. The reconstruction of both three- and six-segment faults reveal common aspects of displacement distribution through time: (1) Displacement accumulation occurs almost entirely in the interaction and linkage phase. (2) Interaction between segments causes enhanced displacement addition in overlap zones. (3) Despite interaction in the soft-linkage stage, faults do not achieve a characteristic profile during this phase (4) Displacement accrues rapidly

  11. Tectonostratigraphic reconstruction Cretaceous volcano-sedimentary in the northwestern Andes: from extensional tectonics to arc accretion.

    NASA Astrophysics Data System (ADS)

    Zapata, S.; Patino, A. M.; Cardona, A.; Mejia, D.; Leon, S.; Jaramillo, J. S.; Valencia, V.; Parra, M.; Hincapie, S.

    2014-12-01

    Active continental margins characterized by continuous convergence experienced overimposed tectonic configurations that allowed the formation of volcanic arcs, back arc basins, transtensional divergent tectonics or the accretion of exotic volcanic terranes. Such record, particularly the extensional phases, can be partially destroyed and obscure by multiple deformational events, the accretion of exotic terranes and strike slip fragmentation along the margin. The tectonic evolution of the northern Andes during the Mesozoic is the result of post Pangea extension followed by the installation of a long-lived Jurassic volcanic arc (209 - 136 ma) that apparently stops between 136 Ma and 110 Ma. The Quebradagrande Complex has been define as a single Lower Cretaceous volcano-sedimentary unit exposed in the western flank of the Central Cordillera of the Colombian Andes that growth after the Late Jurassic to Early Cretaceous magmatic hiatus. The origin of this unit have been related either to an oceanic volcanic arc or a marginal basin environment. The existence of such contrasting models reflect the regional perspective followed in published studies and the paucity of detail analysis of the volcano-sedimentary sequences.We integrate multiple approaches including structural mapping, stratigraphy, geochemistry, U-Pb provenance and geochronology to improve the understanding of this unit and track the earlier phases of accumulation that are mask on the overimposed tectonic history. Our preliminary results suggest the existence of different volcano-sedimentary units that accumulated between 100 Ma and 82 Ma.The older Lower Cretaceous sequences was deposited over Triassic metamorphic continental crust and include a upward basin deepening record characterized by thick fan delta conglomerates, followed by distal turbidites and a syn-sedimentary volcanic record at 100 ma. The other sequence include a 85 - 82 Ma fringing arc that was also formed close to the continental margin or

  12. Submarine canyon, slope, and shelf sedimentation in an upper Eocene-Oligocene progradational system (Limnos Island, north Aegean Sea, Greece)

    SciTech Connect

    Roussos, N.

    1988-08-01

    The only well-exposed outcrops of a post-Alpine late Eocene-Oligocene basin in the north Aegean Sea are at Limnos Island. These mostly consist of typical slope deposits overlain by remnants of shallow marine shelf and continental (braided-river) deposits. Three main slope lithofacies are distinguished. Canyon deposits consist of thick-bedded, massive, and pebbly sandstones (facies B), conglomerates (facies A), pebbly mudstone where the matrix shows flow (facies F), rock falls (nummulitic limestones), and zones of slump folds in sandstones (facies F). Channelized facies of massive sandstones, classical turbidites, and thin interbeds of sandstone and mudstone (facies E - probably overbank or levee deposits) are associated with canyon deposits. Pelagic and hemipelagic slope deposits consist of mudstone (facies G) and thin-bedded sandstone (facies D) with occasional small to medium-scale slump folds. These mud-rich slope deposits are incised by several channels filled with conglomerates, thick massive sandstones with well-developed dish structures, and turbidites interbedded with thin layers of mudstone (facies C). This unit composes a typical thinning and fining-upward sequence.

  13. The application of an age-structured model to the north Aegean anchovy fishery: an evaluation of different management measures.

    PubMed

    Politikos, D V; Tzanetis, D E; Nikolopoulos, C V; Maravelias, C D

    2012-05-01

    The objective of this paper is the integration of existing biological and fishery knowledge of anchovy into a unified modelling framework in order to advance our understanding of species' population dynamics under different fishing strategies. The model simulates the anchovy biomass by combining an age-specific growth equation and a continuous age-structured population model based on the McKendrick-Von Foerster equation. Model predictions were compared to the biomass estimates and annual catches during the period 2003-2008. The present work provided direct evidence for the significance of the prespawning period as a critical life period for the management of anchovy stock in the Aegean Sea. It was found that the introduction of additional management measures could increase the profits in the long run for the fishery. However, for these to become apparent they will require a minimum of four years. Results also indicated that the reduction of fishing mortality directed at the spawning stock (recruitment overfishing) and the selective harvesting of younger individuals may be a plausible means of increasing stock's total anchovy biomass. Finally, as a criterion of long-term population survival, we have considered the mathematical notation of persistence. The numerical criteria of persistence in the present model indicated that the anchovy population could be considered viable.

  14. Total and inorganic arsenic levels in some marine organisms from Izmir Bay (Eastern Aegean Sea): a risk assessment.

    PubMed

    Kucuksezgin, Filiz; Gonul, Lutfi Tolga; Tasel, Didem

    2014-10-01

    The arsenic compounds in marine biota were evaluated from Izmir Bay (Eastern Aegean) and found that inorganic arsenic occurred as a minor fraction. No information is available on the annual variations of arsenic in important edible biota species from Izmir Bay. Fish and mussel samples were taken from different regions of Izmir Bay between 2009 and 2011 (n=854 individual specimens). The average percentages of inorganic arsenic to total arsenic for all biota samples were 3.43±3.38% with a range of 0.11-11.8%. The importance of speciation analysis for arsenic is supported by our work, because arsenic is ubiquitous in the ecosystem, and flexible toxicity of arsenic is based on chemical form. The average total As levels in Mullus barbatus were 6 times higher than Diplodus annularis and Mytilus galloprovincialis. This study also revealed that spatial variation influenced the arsenic levels in the fish samples and the highest concentrations of arsenic were found in Gediz site. Our study showed that estimated daily intakes of arsenic via consumption of flesh fish and shell fish were below the BMDL0.5 values established by FAO/WHO. PMID:25048921

  15. AMS fabric and tectonic evolution of Quaternary intramontane extensional basins in the Picentini Mountains (southern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Porreca, M.; Mattei, M.

    2012-04-01

    In this work, we report the results of combined geological, structural, and anisotropy of magnetic susceptibility (AMS) studies carried out on Quaternary deposits in the Picentini Mountains, southern Apennines (Italy). The study concerns four small continental basins, Acerno, Tizzano, Iumaiano, and Piano del Gaudo, related to fluvial-lacustrine depositional environments, ranging in altitude from 600 to 1,200 m a.s.l. and strongly incised during recent time. Stratigraphic and structural analyses, integrated by low- and high-field anisotropy of magnetic susceptibility (AMS), show that the formation of these basins has been controlled by extensional and transtensional tectonics. Most of the AMS sites exhibit a well-defined magnetic foliation parallel to the bedding planes. A well-defined magnetic lineation has also been measured within the foliation planes. In the Iumaiano, Tizzano, and Piano del Gaudo basins, magnetic lineations cluster around NNE-SSW trend and are parallel to the stretching directions inferred by structural analysis of faults and fractures. On the basis of structural, sedimentological, and high-field AMS data, we suggest a tectonic origin for the magnetic lineation, analogously to what has been observed in other weakly deformed sediments from Neogene and Quaternary extensional basins of the Mediterranean region. Our results demonstrate that onset and the evolution of the investigated basins have been mainly controlled since lower Pleistocene by NW-SE normal and transtensional faults. This deformation pattern is consistent with a prevalent NE-SW extensional tectonic regime, still active in southern Apennines, as revealed by seismological and geodetic data.

  16. Superposed local and regional paleostresses: Fault-slip analysis of Neogene extensional faulting near coeval caldera complexes, Yucca Flat, Nevada

    SciTech Connect

    Minor, S.A.

    1995-06-10

    Numerous reduced stress tensors are computed by multiple inversions of 906 temporally and spatially partitioned fault-slip data from the Yucca Flat region in the southwest Nevada volcanic field to constrain the Neogene paleostress and faulting history and to investigate how the regional tectonic stress field was affected by local caldera magmatism. Perturbed, shallow (<400 m), pre-11 Ma paleostress configurations, determined west and northwest of present (post-11 Ma) Yucca Flat basin, existed during mild extensional faulting and are attributed to superposition of transient caldera-magmatic stresses on the regional stress field. A brief ({approximately} 0.5 m.y.) change to a strike-slip stress state occurred at about 13 Ma and was accompanied by small-offset, quasi-conjugate strike-slip faulting. This stress state was most distinct, relative to a normalslip state, near calderas where stress solutions and fault relations indicate closer affinities to a reverse-slip state. Inferred 11.6-11.45 Ma paleostress tensors indicate radial tension associated with either initial caldera collapse or local post-collapse topographic modification of the stress field. Post-11 Ma normal-slip stress tensors are associated with normal- and oblique-slip faults that accommodated subsidence and eastward extension of Yucca Flat basin away from the caldera complexes. These tensors do not indicate stress modifications due to residual caldera-related effects and thus were used to infer post-11 Ma regional stress changes. The stress field has rotated as much as 65{degrees} clockwise since 11 Ma during extensional development of Yucca Flat basin, with most of the rotation and extension occurring before about 8.5 Ma. Results suggest that shallow magmatism and caldera development can strongly alter extensional tectonic stress fields, fault patterns, and slip directions in the uppermost crust out to distances of roughly two magma chamber radii away from a magma body. 59 refs., 11 figs., 2 tabs.

  17. Effects of an extensional tectonic stress on magmatic reservoir failure and magma propagation within the Venusian lithosphere

    NASA Astrophysics Data System (ADS)

    Le Corvec, N.; McGovern, P. J., Jr.; Grosfils, E. B.; Goldman, R. T.; Albright, J. A.

    2015-12-01

    Failure of magmatic reservoirs and propagation of magmas is controlled in part by the state of stress within the lithosphere. Such stresses are induced by a range of loadings (e.g., gravitational and magmatic). Additional stresses can be introduced by flexural deformation of the lithosphere due to a large volcanic edifice or mantle plume loading, or as a consequence of the regional tectonic environment. Rifting environments, for instance are the results of extensional stresses at the surface of planets (e.g., Devana Chasma on Venus). The resulting stress field may influence the failure of a magmatic reservoir and the propagation of magmas. To explore this scenario, we created 3D elastic models of the Venusian lithosphere using COMSOL Multiphysics, in which an extensional stress was applied. The stress state was implemented through horizontal deformation created by orthogonal contraction and extension on the outer boundaries of the quarter symmetry model. A spherical reservoir is embedded within the lithosphere to represent a magma chamber. In these models, we analyzed magma reservoir stability at different depths, the amount of overpressure needed to reach failure, and the type of resulting intrusions within the 3D model for three distinct environments: 1- lithostatic; 2- upward flexure due to a rising mantle plume; and 3- downward flexure due to a basaltic shield volcano. Preliminary results show that as the extensional stress increases: magmatic reservoirs become unstable at shallow depth and the amount of overpressure needed to reach failure decreases. In addition, the failure location along the reservoir flank rotates to parallel the horizontal contraction, which favors the formation of lateral dikes along the magma reservoir flanks over vertical dikes at the summit.

  18. Magnetic fabric results in weakly deformed deposits from extensional and compressional domains of the Northern Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Caricchi, Chiara; Cifelli, Francesca; Kissel, Catherine; Sagnotti, Leonardo; Mattei, Massimo

    2016-04-01

    Since 1960s the anisotropy of magnetic susceptibility (AMS) analysis has been used to reconstruct the deformation history of rocks, and many studies have been published regarding the relationships between magnetic fabric and tectonics. Nevertheless, an active scientific debate still exists on the tectonic or sedimentary origin of the magnetic fabric observed in sedimentary rocks in which visible evidence of deformation is lacking. In this work, we present results from AMS analyses carried out on weakly deformed fine-grained sediments from the Northern Apennines (Italy). We analyzed pre-, syn- and post- orogenic sequences, which differ in age, composition, depositional environment, degrees of deformation and tectonic regimes. The AMS fabric of these weakly deformed sediments is characterized by a magnetic foliation sub-parallel to the bedding plane, and a magnetic lineation well-defined in this plane. The sediments are characterized by strongly oblate magnetic susceptibility ellipsoids suggesting that magnetic fabric results from both compaction process and tectonic load during diagenesis and orogenic events. The orientation of the magnetic lineation with respect to the main tectonic elements depends on the regional tectonic context, and in particular it varies between extensional and compressional tectonic regimes. In the pre- and syn- orogenic deposits of the more internal arc of the Apennine chain, the lineation is mostly NNW-SSE, parallel to the main compressional structures (folds and thrusts), suggesting a tectonic origin of the magnetic lineation with an acquisition related to the Apennines compressional phases. Instead, in the post-orogenic deposits of the extensional basins developed along the Tuscan Tyrrhenian Margin, magnetic lineation is oriented ENE-WSW, almost perpendicular to the main extensional faults which represent the main deformation elements of the area. Our results indicate a distinctive linkage between the magnetic fabric and the local

  19. Permian evolution of sandstone composition in a complex back-arc extensional to foreland basin: The Bowen Basin, eastern Australia

    SciTech Connect

    Baker, J.C. . Centre for Microscopy and Microanalysis); Fielding, C.R. . Dept. of Earth Sciences); Caritat, P de . Dept. of Geology); Wilkinson, M.M. )

    1993-09-01

    The Bowen Basin is a Permo-Triassic, back-arc extensional to foreland basin that developed landward of an intermittently active continental volcanic arc associated with the eastern Australian convergent plate margin. The basin has a complex, polyphase tectonic history that began with limited back-arc crustal extension during the Early Permian. This created a series of north-trending grabens and half grabens which, in the west, accommodated quartz-rich sediment derived locally from surrounding, uplifted continental basement. In the east, coeval calc-alkaline, volcanolithic-rich, and volcaniclastic sediment was derived from the active volcanic arc. This early extensional episode was followed by a phase of passive thermal subsidence accompanied by episodic compression during the late Early Permian to early Late Permian, with little contemporaneous volcanism. In the west, quartzose sediment was shed from stable, polymictic, continental basement immediately to the west and south of the basin, whereas volcanolithic-rich sediment that entered the eastern side of the basin during this time was presumably derived from the inactive, and possibly partly submerged volcanic arc. During the late Late Permian, flexural loading and increased compression occurred along the eastern margin of the Bowen Basin, and renewed volcanism took place in the arc system to the east. Reactivation of this arc led to westward and southward spread of volcanolithic-rich sediment over the entire basin. Accordingly, areas in the west that were earlier receiving quartzose, craton-derived sediment from the west and south were overwhelmed by volcanolithic-rich, arc-derived sediment from the east and north. This transition from quartz-rich, craton-derived sediments to volcanolithic-rich, arc-derived sediments is consistent with the interpreted back-arc extensional to foreland basin origin for the Bowen Basin.

  20. Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting

    NASA Astrophysics Data System (ADS)

    Etheve, Nathalie; Frizon de Lamotte, Dominique; Mohn, Geoffroy; Martos, Raquel; Roca, Eduard; Blanpied, Christian

    2016-07-01

    Based on field work and seismic reflection data, we investigate the Cenozoic tectono-sedimentary evolution offshore and onshore Ibiza allowing the proposal of a new tectonic agenda for the region and its integration in the geodynamic history of the West Mediterranean. The late Oligocene-early Miocene rifting event, which characterizes the Valencia Trough and the Algerian Basin, located north and south of the study area respectively, is also present in Ibiza and particularly well-expressed in the northern part of the island. Among these two rifted basins initiated in the frame of the European Cenozoic Rift System, the Valencia Trough failed rapidly while the Algerian Basin evolved after as a back-arc basin related to the subduction of the Alpine-Maghrebian Tethys. The subsequent middle Miocene compressional deformation was localized by the previous extensional faults, which were either inverted or passively translated depending on their initial orientation. Despite the lateral continuity between the External Betics and the Balearic Promontory, it appears from restored maps that this tectonic event cannot be directly related to the Betic orogen, but results from compressive stresses transmitted through the Algerian Basin. A still active back-arc asthenospheric rise likely explains the stiff behavior of this basin, which has remained poorly deformed up to recent time. During the late Miocene a new extensional episode reworked the southern part of the Balearic Promontory. It is suggested that this extensional deformation developed in a trans-tensional context related to the westward translation of the Alboran Domain and the coeval right-lateral strike-slip movement along the Emile Baudot Escarpment bounding the Algerian Basin to the north.

  1. Extensional geometries as a result of regional scale thrusting: tectonic slides of the Dunlewy-NW Donegal area, Ireland

    NASA Astrophysics Data System (ADS)

    Hutton, Donald H. W.; Alsop, G. Ian

    1995-09-01

    The synmetamorphic ductile dislocations, known in the British Caledonian literature as 'Tectonic Slides', pose a classical structural problem. That is, despite being associated with synchronous contractional folds and cleavages the low angle dislocations have the effect, in many celebrated cases, of juxtaposing younger over older rocks: a geometry normally associated with extensional rather than contractional deformation. Recent models have attempted to demonstrate that this is the result of thrust reactivation of original, sedimentary, extensional growth faults. The Appin Group Dalradian metasediments of the complex and small Dunlewy area of NW Donegal, Ireland, contain the following geometric elements: (a) an early strike-swing-related stratigraphic facies change; (b) a major inter-deformational dolerite sheet; (c) major regional recumbent folds and slides; (d) major structures related to the 400 Ma sinistral Main Donegal Granite shear zone. This solution to the structural geometry reveals that the early mid-crustal (~11 km depth) D2 Ardsbeg-Dunlewy Slide is a thrust to the northwest. Its hangingwall contains rocks two-thirds of which are younger than the rocks of the footwall, together with major recumbent folds, coeval with the underlying thrust, which face downwards into the thrust in the direction of transport. Rather than thrust reactivation of an original extensional growth fault, we find that both stratigraphic and structural constraints are satisfied by a double thrusting model, with fault-bend folding onto an upper ramp of an earlier formed but penecontemporaneous and kinematically linked major fold pair. This solution to the geology also allows us to recognize that the regional (pre-granite) structure of the Dalradian of NW Donegal is a series of major D2 synmetamorphic thrust bounded nappes possibly involving up to 250 km of northwesterly overthrusting.

  2. Quantitative analysis of the extensional tectonics of Tharsis bulge, Mars - Geodynamic implications

    NASA Astrophysics Data System (ADS)

    Thomas, P. G.; Allemand, P.

    1993-07-01

    The amount of horizontal strain on the Martian Tharsis bulge is quantified in order to provide further information on the tectonic evolution of this province. About 10 percent of the Tharsis surface bulge exhibits elliptical impact craters, which are the largest strain markers in the solar system. It is shown that these strain ellipses indicate more strain than could be due to the bulge building alone. The existence of such intensely deformed areas, the direction of the extensive strain, the localization of these areas on the bulge crest or on the top of topographic slopes, and the evidence of nonthinned crust under these areas may all be explained by gravitational slidings of the bulge surface over the topographic slope. This sliding would be possible because of the presence of a decollement level two kilometers below the surface, and because of the prefracturation which have made the detachment possible.

  3. Parametric analysis of inherited low-angle fault reactivation, application to the Aegean detachment faults

    NASA Astrophysics Data System (ADS)

    Lecomte, E.; Le Pourhiet, L.; Lacombe, O.; Jolivet, L.

    2009-04-01

    Widespread occurrences of low angle normal faults have been described within the extending continental crust since their discovery in the Basin and Range province. Although a number of field observations suggest that sliding may occur at very shallow dip in the brittle field, the seismic activity related to such normal faults is nearly inexistent and agrees with the locking angle of 30° predicted from Andersonian fault mechanics associated with Byerlee's law. To understand this apparent contradiction, we have introduced Mohr Coulomb plastic flow rule within the inherited low-angle faults where former studies were limited to a yield criterion. The fault is considered as a pre existing compacting or dilating plane with a shallow dip (0-45°) embedded in a brittle media. Following Anderson's theory, we assume that the maximal principal stress is vertical and equal to the lithostatic pressure. This approximation may not be true for small faults but it holds for large detachment faults where associated joints are generally vertical. With this model, we can predict not only whether new brittle features forms in the surrounding of the low angle normal faults but also the complete stress-strain evolution both within the faults and in its surrounding. Moreover, the introduction of a flow rule within the fault allows brittle strain to occur on very badly oriented faults (dip < 30°) before yielding occurs in the surrounding medium. After performing a full parametric study, we find that the reactivation of low angle normal faults depends primarily on the friction angle of the fault material and the ratio of the cohesion between the shear band and its surrounding. Our model is therefore in good agreement with previous simpler models, and the locking angles obtained differ in most cases by only 2 or 3° from previous yield criteria-based approaches which did explain most of the data especially the repartition of focal mechanisms worldwide. However, we find that in some cases

  4. The continental Etirol-Levaz slice (Western Alps, Italy): Tectonometamorphic evolution of an extensional allochthon

    NASA Astrophysics Data System (ADS)

    Ewerling, Kathrin; Obermüller, Gerrit; Kirst, Frederik; Froitzheim, Nikolaus; Nagel, Thorsten; Sandmann, Sascha

    2013-04-01

    The Etirol-Levaz slice (ELS) in the western Valtournenche of Italy is a continental fragment trapped between two oceanic units, the eclogite-facies Zermatt-Saas Zone in the footwall and the greenschist-facies Combin Zone in the hanging wall. It has been interpreted as an extensional allochthon derived from the Adriatic continental margin and stranded inside the Piemont-Ligurian oceanic domain during Jurassic rifting (Dal Piaz et al., 2001; Beltrando et al., 2010). The slice consists of Variscan high-grade gneisses, micaschists and metabasics overprinted under eclogite-facies conditions during Early Tertiary Alpine subduction. Eclogites generally consist of garnet + omphacite ± epidote ± amphibole ± phengite ± quartz. We investigate their metamorphic history using equilibrium phase diagrams, mineral compositions, and textural relations between prograde, peak, and retrograde phases. In sample FD328, garnets have compositions of Alm52-61 Grs18-41 Prp5-22 Sps0.5-2 and typical growth zoning. Some garnet grains are brittlely fractured, strongly corroded and overgrown by epidote. Amphibole occurs as a major phase in the matrix and shows a progressive evolution from glaucophane in the core to pargasitic hornblende towards the rim. Sample FD329 with a particular Ca-rich bulk composition (18.3 wt% Ca) displays two distinct garnet generations. Perfectly euhedral cores show compositions of Grs42-45 Alm47-51 Prp3-6 Sps2-7 and typical prograde growth zoning. These cores are overgrown by irregularly shaped rims characterised by an initial rise in Mn and the Fe-Mg ratio. Omphacite in this sample with jadeite-contents of 19-28 mol% apparently has been fractured and annealed by jadeite-poor (7-12 mol%) omphacite suggesting brittle behaviour at eclogite-facies conditions or two high-pressure stages with lower metamorphic conditions in between. We discuss whether the ELS experienced the same monocyclic metamorphic history as the Zermatt-Saas Zone or not. Some of our observations

  5. Evidence for Neoarchaean extensional faults in the Vredefort Dome, South Africa.

    NASA Astrophysics Data System (ADS)

    mashabela, sello

    2013-04-01

    -2643 Ma) of the Ventersdorp Supergroup. The association potentially means that the Vredefort collar hosts rotated Ventersdorp-age extensional faults or a rift system of faults that predate impact-induced structures. 1. Manzi, M.S.D., Durrheim, R.J., Hein, K.A.A., King N., 2012. 3D edge detection seismic attributes used to map potential conduits for water and methane in deep gold mines in the Witwatersrand basin, South Africa. Geophysics 77 (5), 1-16. 2. Manzi, M., Gibson, M. A.S., Hein, K.A.A., King, N., Durrheim, R.J., 2012. Application of 3D Seismic techniques in evaluation of ore resources in the West Wits Line goldfield and portions of the West Rand Goldfield, South Africa. Geophysics 77, 1-9. 3. Manzi, M., Hein, K.A.A., King, N, Durrheim, R.J., submitted. NeoArchaean tectonic history of the Witwatersrand Basin and Ventersdorp Supergroup: New Constraints from high-resolution 3D seismic reflection data. Tectonophysics

  6. 3-D palinspastic restoration of normal faults in the Inner Moray Firth: implications for extensional basin development

    NASA Astrophysics Data System (ADS)

    Barr, David

    1985-10-01

    Balanced cross-section techniques, and the construction of a restored section, permit 2-dimensional palinspastic restorations to be made in both compressional and extensional terraines. In 3 dimensions, an equivalent restoration can be made by assuming conservation of bedding-plane area and considering the volume of a stratigraphic interval rather than its cross-sectional area. Extensional basins displaying upper crustal listric normal faulting are particularly amenable to this approach. Computerised 3-D restorations have been made of the Inner Moray Firth basin, offshore Scotland. This basin is not isostatically compensated, and was produced by 7-8% post-Triassic extension, of which 2.5-3% is post-Jurassic, above a detachment surface at 20-25 km depth, close to the base of the crust. Limited lower crustal thinning (and lithospheric stretching) has affected the eastern part of the basin, but this can account for no more than half of the measured upper crustal extension. Some of this shallow extension is probably coupled by low-angle faults or shear zones into major zones of lithospheric stretching such as the North Sea grabens, where it may help account for discrepancies between estimates of lithospheric thinning and upper crustal extension.

  7. The relationship of extensional and compressional tectonics to a Precambrian fracture system in the eastern overthrust belt, USA

    NASA Technical Reports Server (NTRS)

    Pohn, H.

    1985-01-01

    The central and southern Appalachians have a long history of interrelated extensional and compressional tectonics. It is proposed that each episode was controlled by a reactivation of a fracture system in the Precambrian basement. Proprietary seismic-reflection profiles show a system of down-to-the-east Precambrian extensional faults. When under renewed extension, these faults produce features such as the western border faults of Mesozoic basins, and when under compression, probably produce tectonic ramps in the overlying sedimentary cover rocks as well as the spatially and genetically related Alleghenian folds. This system, which parallels the Appalachian trend, is cut by a system of cross-strike hinge or scissors faults that have probable strike-slip movements. Reactivation of this cross-strike system appears to have produced lateral ramps that connect decollements at different stratigraphic levels and caused abrupt changes in fold wavelength along strikes. Continued reactivation of this cross-strike system is suggested by east-west border faults and Precambrian highs between Mesozoic basins. The present activity of this system is suggested by the fact that more than 35% of recent earthquakes are coincident with cross-strike faults and lateral ramps.

  8. The Pinto shear zone; a Laramide synconvergent extensional shear zone in the Mojave Desert region of the southwestern United States

    USGS Publications Warehouse

    Wells, M.L.; Beyene, M.A.; Spell, T.L.; Kula, J.L.; Miller, D.M.; Zanetti, K.A.

    2005-01-01

    The Pinto shear zone is one of several Late Cretaceous shear zones within the eastern fringe of the Mesozoic magmatic arc of the southwest Cordilleran orogen that developed synchronous with continued plate convergence and backarc shortening. We demonstrate an extensional origin for the shear zone by describing the shear-zone geometry and kinematics, hanging wall deformation style, progressive changes in deformation temperature, and differences in hanging wall and footwall thermal histories. Deformation is constrained between ???74 and 68 Ma by 40Ar/39Ar thermochronology of the exhumed footwall, including multi-diffusion domain modeling of K-feldspar. We discount the interpretations, applied in other areas of the Mojave Desert region, that widespread Late Cretaceous cooling results from refrigeration due to subduction of a shallowly dipping Laramide slab or to erosional denudation, and suggest alternatively that post-intrusion cooling and exhumation by extensional structures are recorded. Widespread crustal melting and magmatism followed by extension and cooling in the Late Cretaceous are most consistent with production of a low-viscosity lower crust during anatexis and/or delamination of mantle lithosphere at the onset of Laramide shallow subduction. ?? 2005 Elsevier Ltd. All rights reserved.

  9. Megabreccia deposits in an extensional basin: The Miocene-Pliocene Horse Camp Formation, east-central Nevada

    SciTech Connect

    Schmitt, J.G.; Brown, C.L. )

    1991-06-01

    Three varieties of megabreccia deposits are present in alluvial-lacustrine extensional basin fill of the Miocene-Pliocene Horse Camp Formation of east-central Nevada. Coherent debris sheets (150-300 m thick; up to 1,500 m long) consist of Oligocene-Miocene volcanic rock masses which are internally fractured yet retain their stratigraphic integrity. Fracture zones show variable amounts of displacement (up to 5 cm) and brecciation. These debris sheets overlie horizontally stratified sandstone and laminated claystone interpreted as playa deposits and are overlain by lithified grus. Emplacement of these coherent debris sheets was by landslide or block slide. Associated deposits of large boulders within playa facies suggest gliding of blocks broken from the edges of the landslides across wet playa surfaces. Large (1.6 - 2.4 km-long) allochthonous blocks consist of intact Paleozoic and Tertiary volcanic stratigraphic sequences which are brecciated and attenuated. Brecciation is accompanied in places by incorporation of muddy sand matrix. These blocks may be fragments of the upper plate of low-angle detachment faults which broke away as gravity-driven blocks from the nearby Horse Range and slid along the uplifted former detachment surface into the adjacent Horse Camp basin. Megabreccia deposits characterize Teritary extensional basins in western North America. Detailed analysis of their stratigraphic, sedimentologic, and structural relations can provide a better understanding of the complex tectonosedimentary history of these basins.

  10. Seismic reflection geometry of the Newark basin margin in Eastern Pennsylvania. Evidence for extensional reactivation of Paleozoic thrust faults

    SciTech Connect

    Ratcliffe, N.M.; Burton, W.C.; D'Angelo, R.M.; Costain, J.K.

    1986-07-01

    Low-angle 25/sup 0/ to 35/sup 0/ dips have been determined for the border fault of the Newark basin near Riegelsville, Pennsylvania, based on a VIBROSEIS profile and two continuously-cored drill holes across faults at the basin margin. A group of moderately strong planar reflections in a zone 0.5 km thick in gneiss and carbonate rocks of the footwall block coincide with the updip projection of imbricate fault slices and mylonites associated with the Musconetcong thrust system of Drake and others (1967). Contrasts in acoustic impedance among mylonitic dolostone and mylonitic gneiss and their protoliths, determined from measurements on core samples, are sufficiently large to account for reflections seen in the footwall block. Analysis of drill core and surface outcrops supports the conclusion that low-angle extensional faulting in the Early Mesozoic was localized by reactivation of Paleozoic imbricate thrust faults in the basement rocks. Extension in the NW-SE quadrant was approximately perpendicular to the strike of the ancient thrust faults in Eastern Pennsylvania and a passive origin of the Newark basin here is suggested. The data presented here represent some of the most explicit three-dimensional information obtained thus far, in the Eastern United States, in support of the concept of fault reactivation in controlling formation of Early Mesozoic extensional basins.

  11. Low-angle extensional faulting, reactivated mylonites, and seismic reflection geometry of the Newark basin margin in eastern Pennsylvania

    SciTech Connect

    Ratcliffe, N.M.; Burton, W.C.; D'Angelo, R.M.; Costain, J.K.

    1986-09-01

    Low-angle 25/sup 0/ to 35/sup 0/ dips have been determined for the border fault of the Newark basin near Riegelsville, Pennsylvania, on the basis of a Vibroseis profile and two continuously cored drill holes across faults at the basin margin. A group of moderately strong planar reflections in a zone 0.5 km thick in gneiss and carbonate rocks of the footwall block coincides with the updip projection of imbricate fault slices and mylonites associated with the Musconetcong thrust system of Drake et al. (1967). Contrasts in acoustic impedance among mylonitic dolostone and mylonitic gneiss and their protoliths, determined from measurements on samples from a third cored hole, are sufficiently large to account for reflections seen in the footwall block. Analysis of drill core and surface outcrops supports the conclusion that low-angle extensional faulting in the early Mesozoic was localized by reactivation of Paleozoic imbricate thrust faults in the basement rocks. Extension in the northwest-southeast quadrant was approximately perpendicular to the strike of the ancient thrust faults in eastern Pennsylvania. The data presented here are the most explicit three-dimensional information obtained thus far in the eastern US in support of the concept of fault reactivation in controlling formation of early Mesozoic extensional basins.

  12. A disarticulated lava cone, Burney Spring Mountain, Shasta County, USA: implications for extensional tectonics in the southern Cascades

    NASA Astrophysics Data System (ADS)

    Kersten, Kevin Robert

    Burney Spring Mountain is a 2556 ka lava cone situated in the northernmost part of the Lassen segment of the Cascade Range. Dominated in volume by lava flows ranging from olivine basalts to augite, hypersthene andesites, Burney Spring Mountain is also comprised of localized ash fall tuffs, a pyroclastic flow, a scoria cone and a debris flow. Lavas originate from a central vent. A robust survey of the stratigraphy shows that Burney Spring Mountain is composed of at least two magma batches. A paleomagnetic survey reveals that the characteristic remanent magnetization of Burney Spring Mountain is heavily influenced by faulting and that when structural corrections are applied to the data the sampled lava flows show a uniform direction of characteristic magnetization, indicative of an eruption period of a few hundred years. Mapping reveals that two vents (Burney Spring Mountain and the scoria cone) form a linear array that parallels local normal faults suggesting that Burney Spring Mountain formed under an extensional tectonic regime. This suggest that extension was occurring in the Lassen segment of the Cascade volcanic arc as early as 2556 ka, making it the earliest known evidence of extension. Burney Spring Mountain is mineralogically and chemically similar to younger volcanoes to the south such as those of the Poison Lake chain, the Prospect Peak chain and the Sugarloaf chain. Their chemical similarity and formation under extensional tectonics suggests a common origin. Plate 1 contains maps and unit descriptions

  13. Fabric evidence for granodiorite emplacement with extensional shear zones in the Variscan Gredos massif (Spanish Central System)

    NASA Astrophysics Data System (ADS)

    Díaz-Alvarado, Juan; Fernández, Carlos; Díaz-Azpiroz, Manuel; Castro, Antonio; Moreno-Ventas, Ignacio

    2012-09-01

    Three granitoid bodies in the central part of the Gredos massif (Spanish Central System batholith) are tabular, around 1 km in thickness, and intruded into a migmatitic middle crust during the D3 deformation phase of the Variscan Orogeny. Petrologically, they are composed of Bt-granodiorite and Crd-monzogranite, and they show varying abundance of large (cm-scale) feldspar megacrysts. A detailed study of the shape preferred orientation (SPO) magmatic fabric defined by these megacrysts, together with a kinematic analysis of the structures due to interactions between them, and the measurement of quartz c-axis fabrics in migmatites and granitoids, suggests that granitic magma and country rocks were mechanically coupled during deformation. The emplacement took place along large-scale, extensional shear zones active during the first stages of the D3 phase. The shape of the SPO ellipsoids varies from constrictional at the centre of the granitic bodies, to flattening or even oblate at their external contacts with the migmatitic host rocks. The favoured interpretation of this spatial fabric variation is the overprinting of the emplacement fabrics by a constrictional tectonic regime associated with the growth of tabular magma chambers along extensional detachments, followed by shear zone development commonly at the top of the granitic bodies. The entire structure was later folded during the last stages of the D3 phase.

  14. Tectonic fabrics vs. mineralogical artifacts in AMS analysis: A case study of the Western Morocco extensional Triassic basins

    NASA Astrophysics Data System (ADS)

    Oliva-Urcia, B.; Casas, A. M.; Moussaid, B.; Villalaín, J. J.; El Ouardi, H.; Soto, R.; Torres-López, S.; Román-Berdiel, T.

    2016-03-01

    New magnetic fabric data from 48 sites in Upper Triassic red beds from the Argana, Asni and Tizi n'Tichka areas in the western High Atlas, in combination with rock magnetic analyses, SEM observations and qualitative chemical analyses, reveal that mineralization processes can affect the primary (extensional) or secondary (post-depositional) magnetic fabrics. Twenty out of the 48 analyzed sites show tectonic-related fabrics consistent with the rifting stage (primary). Their orientation suggests that the extensional Atlasic (for the Asni area) and Atlantic (for Argana area) distinct directions prevailing during Liassic times are already present in the Upper Triassic sediments. The other 28 sites show axes switching (including different possibilities, kmax-kmin or kint-kmin), indicating their secondary development related to mineralogical changes after deposition. However, orientation of magnetic susceptibility axes (without considering their relative value) is consistent with the main directions obtained for the rifting stage. This magnetic fabric study also suggests that (i) extension had a small transtensional component and (ii) there is a limited influence of compressional inversion tectonics.

  15. Non-standard coupled extensional and bending bias tests for planar pantographic lattices. Part II: comparison with experimental evidence

    NASA Astrophysics Data System (ADS)

    Turco, Emilio; Barcz, Katarzyna; Rizzi, Nicola Luigi

    2016-10-01

    In dell'Isola et al. (Zeitschrift für Angewandte Math und Physik 66(6):3473-3498, 2015, Proc R Soc Lond A Math Phys Eng Sci 472(2185):1-23, 2016) pantographic sheets are proposed as a basic constituent for a novel metamaterial. In Part I, see Turco et al. (Zeitschrift für Angewandte Math und Physik, doi: 10.1007/s00033-016-0713-4, 2016), two different numerical models are applied in order to design an experimental setup aimed to prove the effectiveness of introduced concept. The aim of this paper is to prove that the Hencky-type model introduced for planar pantographic sheets allows for the correct prediction, in a large range of imposed displacements, of the experimental measurements concerning specimens undergoing coupled bending and extensional deformations. The four-parameter numerical model introduced is shown to have a large range of applicability: Indeed without changing the values of the material parameters previously attributed in simple extensional tests to a specific specimen by a best-fit procedure, it is possible to forecast its behavior in all the considered type of imposed deformations. The measurements performed include the determination of reactive forces exerted by used hard devices, and the numerical modeling is able to predict very carefully quantitatively and qualitatively also this complex aspect of phenomenology, where previously attempted models seem to have failed.

  16. Non-standard coupled extensional and bending bias tests for planar pantographic lattices. Part I: numerical simulations

    NASA Astrophysics Data System (ADS)

    Turco, Emilio; Barcz, Katarzyna; Pawlikowski, Marek; Rizzi, Nicola Luigi

    2016-10-01

    In dell'Isola et al. (Zeitschrift für Angewandte Math und Physik 66(6):3473-3498, 2015, Proc R Soc Lond A Math Phys Eng Sci 472(2185), 2016), the concept of pantographic sheet is proposed. The aim is to design a metamaterial showing: (i) a large range of elastic response; (ii) an extreme toughness in extensional deformation; (iii) a convenient ratio between toughness and weight. However, these required properties must coexist with non-detrimental mechanical characteristics in the presence of other kinds of imposed displacements. The aim of this paper is to prove via numerical simulations that pantographic sheets may effectively resist to coupled bending and extensional deformations. The four-parameter model introduced shows its versatility as it is able to encompass all the considered types of (large) deformations. The numerical integration scheme which we use is based on the same concepts exploited in Turco et al. (Zeitschrift für Angewandte Math und Physik 67(4):1-28, 2016): They prove that the Hencky-type discretization is very efficient also in nonlinear large deformations and large displacements regimes. In Part II of this paper, we will show that the used models are very effective to describe experimental evidence.

  17. Assessment of undiscovered oil and gas resources of the East Coast Mesozoic basins of the Piedmont, Blue Ridge Thrust Belt, Atlantic Coastal Plain, and New England Provinces, 2011

    USGS Publications Warehouse

    Milici, Robert C.; Coleman, James L.; Rowan, Elisabeth L.; Cook, Troy A.; Charpentier, Ronald R.; Kirschbaum, Mark A.; Klett, Timothy R.; Pollastro, Richard M.; Schenk, Christopher J.

    2012-01-01

    During the early opening of the Atlantic Ocean in the Mesozoic Era, numerous extensional basins formed along the eastern margin of the North American continent from Florida northward to New England and parts of adjacent Canada. The basins extend generally from the offshore Atlantic continental margin westward beneath the Atlantic Coastal Plain to the Appalachian Mountains. Using a geology-based assessment method, the U.S. Geological Survey estimated a mean undiscovered natural gas resource of 3,860 billion cubic feet and a mean undiscovered natural gas liquids resource of 135 million barrels in continuous accumulations within five of the East Coast Mesozoic basins: the Deep River, Dan River-Danville, and Richmond basins, which are within the Piedmont Province of North Carolina and Virginia; the Taylorsville basin, which is almost entirely within the Atlantic Coastal Plain Province of Virginia and Maryland; and the southern part of the Newark basin (herein referred to as the South Newark basin), which is within the Blue Ridge Thrust Belt Province of New Jersey. The provinces, which contain these extensional basins, extend across parts of Georgia, South Carolina, North Carolina, Virginia, Maryland, Delaware, Pennsylvania, New Jersey, New York, Connecticut, and Massachusetts.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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.

  20. Assessing enigmatic boulder deposits in NE Aegean Sea: importance of historical sources as tool to support hydrodynamic equations

    NASA Astrophysics Data System (ADS)

    Vacchi, M.; Rovere, A.; Zouros, N.; Firpo, M.

    2012-04-01

    Due to their importance in the assessment of coastal hazards, several studies have focused on geomorphological and sedimentological field evidence of catastrophic wave impacts related to historical tsunami events. Among them, many authors used boulder fields as important indicators of past tsunamis, especially in the Mediterranean Sea. The aim of this study was to understand the mechanism of deposition of clusters of large boulders, consisting of beachrock slabs, which were found on the southern coasts of Lesvos Island (NE Aegean Sea). Methods to infer the origin of boulder deposits (tsunami vs. storm wave) are often based on hydrodynamic models even if different environmental complexities are difficult to be incorporated into numerical models. In this study, hydrodynamic equations did not provide unequivocal indication of the mechanism responsible for boulder deposition in the study area. Further analyses, ranging from geomorphologic to seismotectonic data, indicated a tsunami as the most likely cause of displacement of the boulders but still do not allow to totally exclude the extreme storm origin. Additional historical investigations (based on tsunami catalogues, historical photos and aged inhabitants interviews) indicated that the boulders are likely to have been deposited by the tsunami triggered by the 6.7 Ms Chios-Karaburum earthquake of 1949 or, alternatively, by minor effects of the destructive tsunami produced by 1956's Amorgos Island earthquake. Results of this study point out that, at Mediterranean scale, to flank numerical models with the huge amount of the available historical data become a crucial tool in terms of prevention policies related to catastrophic coastal events.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  2. Tracing metal pollution sources of plants and soils in Güzelhisar Basin of Aegean Region, Turkey

    NASA Astrophysics Data System (ADS)

    Czarnecki, Sezin; Görsch, Carolin; Colak Esetlili, Bihter; Esetlili, Tolga; Tepecik, Mahmut; Kurucu, Yusuf; Anac, Dilek; Düring, Rolf-Alexander

    2016-04-01

    The study area Güzelhisar Basin is 6 km far from the city Aliaga, Aegean Region in the west part of Turkey which represents a rather industrialized area having five large iron and steel mills, but also areas of agriculture. A grid system of 2.5 km to the east and 2.5 km to the west of the Güzelhisar Stream was studied. The area was grouped into three main areas as West, Middle, and East region. Every 500 meters soil samples were taken after the rainfall (April-May) in 2014 from the GPS determined points at 0-30 and 30-60 cm depth. Soil reaction of the study area was determined within the range from 5.87 to 6.61. Even though, the West and the Middle regions had weak carbonate concentrations, the East region was poor in carbonates and relatively high electrical conductivity was measured. Topsoil contamination was examined by all investigated elements with the exception of Cd. An increase in pseudo total metal contents of Cr, Cu, Mn, Ni, and Zn was observed with the increasing distance from the coast with a simultaneous decrease in pH. Moreover, high plant metal concentrations [mg kg‑¹, ± sd] were detected for B [20.7 ± 23.9], Cu [7.99 ± 5.17], Mn (79.3 ± 89.2), Ni (3.50 ± 3.48), and Zn (25.5 ± 20.1). Transfer of the elements from soil to plants increased in the following order: Co < As < Cr < Pb < Mn < Ni < Cu < Zn < Cd << B.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  4. Simulating anchovy's full life cycle in the northern Aegean Sea (eastern Mediterranean): A coupled hydro-biogeochemical-IBM model

    NASA Astrophysics Data System (ADS)

    Politikos, D.; Somarakis, S.; Tsiaras, K. P.; Giannoulaki, M.; Petihakis, G.; Machias, A.; Triantafyllou, G.

    2015-11-01

    A 3-D full life cycle population model for the North Aegean Sea (NAS) anchovy stock is presented. The model is two-way coupled with a hydrodynamic-biogeochemical model (POM-ERSEM). The anchovy life span is divided into seven life stages/age classes. Embryos and early larvae are passive particles, but subsequent stages exhibit active horizontal movements based on specific rules. A bioenergetics model simulates the growth in both the larval and juvenile/adult stages, while the microzooplankton and mesozooplankton fields of the biogeochemical model provide the food for fish consumption. The super-individual approach is adopted for the representation of the anchovy population. A dynamic egg production module, with an energy allocation algorithm, is embedded in the bioenergetics equation and produces eggs based on a new conceptual model for anchovy vitellogenesis. A model simulation for the period 2003-2006 with realistic initial conditions reproduced well the magnitude of population biomass and daily egg production estimated from acoustic and daily egg production method (DEPM) surveys, carried out in the NAS during June 2003-2006. Model simulated adult and egg habitats were also in good agreement with observed spatial distributions of acoustic biomass and egg abundance in June. Sensitivity simulations were performed to investigate the effect of different formulations adopted for key processes, such as reproduction and movement. The effect of the anchovy population on plankton dynamics was also investigated, by comparing simulations adopting a two-way or a one-way coupling of the fish with the biogeochemical model.

  5. Hydrodynamic features of the South Aegean Sea as derived from Argo T/ S and dissolved oxygen profiles in the area

    NASA Astrophysics Data System (ADS)

    Kassis, Dimitris; Krasakopoulou, Evangelia; Korres, Gerasimos; Petihakis, George; Triantafyllou, George S.

    2016-11-01

    In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013-July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Paris, Raphael; Nomikou, Paraskevi; Tappin, Dave

    2016-04-01

    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 evidences of the 1650 AD tsunami were 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 correspond to an irregular 5 to 30 cm thick layer of dark grey sand intercalated in soil at depths between 30 and 50 cm. Composition of the tsunami sand is similar to the composition of the present-day beach and clearly differs from the pumiceous gravelly soil. Spatial distribution of the tsunami deposits was confronted to available historical records and to the results of numerical simulations of tsunami inundation. Different scenarios of source mechanism 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 E15 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. Caldera subsidence is not an efficient source of tsunami, as short (and probably unrealistic) collapse durations (< 5 minutes) are needed. Pyroclastic flows cannot be discarded, but the required flux (E6 to E7 m³.s-1) is exceptionally high compared to the magnitude of the eruption.

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

    PubMed

    Ugur, Aysun; Miquel, Juan-Carlos; Fowler, Scott W; Appleby, Peter

    2003-05-20

    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)).

  9. Tracing metal pollution sources of plants and soils in Güzelhisar Basin of Aegean Region, Turkey

    NASA Astrophysics Data System (ADS)

    Czarnecki, Sezin; Görsch, Carolin; Colak Esetlili, Bihter; Esetlili, Tolga; Tepecik, Mahmut; Kurucu, Yusuf; Anac, Dilek; Düring, Rolf-Alexander

    2016-04-01

    The study area Güzelhisar Basin is 6 km far from the city Aliaga, Aegean Region in the west part of Turkey which represents a rather industrialized area having five large iron and steel mills, but also areas of agriculture. A grid system of 2.5 km to the east and 2.5 km to the west of the Güzelhisar Stream was studied. The area was grouped into three main areas as West, Middle, and East region. Every 500 meters soil samples were taken after the rainfall (April-May) in 2014 from the GPS determined points at 0-30 and 30-60 cm depth. Soil reaction of the study area was determined within the range from 5.87 to 6.61. Even though, the West and the Middle regions had weak carbonate concentrations, the East region was poor in carbonates and relatively high electrical conductivity was measured. Topsoil contamination was examined by all investigated elements with the exception of Cd. An increase in pseudo total metal contents of Cr, Cu, Mn, Ni, and Zn was observed with the increasing distance from the coast with a simultaneous decrease in pH. Moreover, high plant metal concentrations [mg kg-¹, ± sd] were detected for B [20.7 ± 23.9], Cu [7.99 ± 5.17], Mn (79.3 ± 89.2), Ni (3.50 ± 3.48), and Zn (25.5 ± 20.1). Transfer of the elements from soil to plants increased in the following order: Co < As < Cr < Pb < Mn < Ni < Cu < Zn < Cd << B.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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.

  11. Growth and feeding patterns of European anchovy ( Engraulis encrasicolus) early life stages in the Aegean Sea (NE Mediterranean)

    NASA Astrophysics Data System (ADS)

    Catalán, Ignacio A.; Folkvord, Arild; Palomera, Isabel; Quílez-Badía, Gemma; Kallianoti, Fotini; Tselepides, Anastasios; Kallianotis, Argyris

    2010-01-01

    The objective of this work was to describe inter- and intra-annual variations in the environmental characteristics of the North-eastern Aegean Sea and to relate these changes to the egg and larval distributions, growth and feeding of larval anchovy ( Engraulis encrasicolus). Four cruises, two in July and two in September in 2003 and 2004 were performed. The distributions of eggs and larvae were associated with i) salinity fronts related to the Black Sea Water and ii) shallow areas of high productivity over the continental shelf, some of them with high riverine influence. The first published description of the anchovy larval diet in the Eastern Mediterranean was conducted in individuals ranging from 2.2 to 17 mm standard length. The number of non-empty guts was relatively high (between 20% and 30%), and the diet was described through 15 main items. The mean size of the prey increased with larval size, and was generally dominated by prey widths smaller than 80 μm (mainly the nauplii and copepodite stages of copepods). Small larvae positively selected copepod nauplii. As larvae grew, they shifted to larger copepod stages. At all sizes, larvae rejected abundant taxa like cladocerans. The average trophic level calculated for anchovy of all size ranges was 2.98 ± 0.16 (SE). Growth rates varied from 0.41 to 0.75 mm d -1, with the highest growth rates generally observed in September. Variability in the Black Sea Water influence and the recorded inter- and intra-annual changes in primary and secondary production, combined with marked changes in temperature over the first 20 m depth, are used to frame the discussion regarding the observed significant differences in growth rates in terms of both length and weight.

  12. On the recent seismic activity in North-Eastern Aegean Sea including the Mw5.8 earthquake on 8 January 2013

    PubMed Central

    SARLIS, Nicholas V.

    2013-01-01

    In the last week of November 2012, we announced that a strong electrotelluric disturbance, which we judged to be a Seismic Electric Signal (SES) activity, was recorded at station Assiros located in Northern Greece. This disturbance was actually followed by an Mw5.8 earthquake on 8 January 2013 in North-Eastern Aegean Sea. Here we show that, by analyzing this SES activity and employing the natural time analysis of subsequent seismicity, we estimated the epicentral location, magnitude and occurrence time which are reasonably compatible with those of the Mw5.8 event. PMID:24213207

  13. Uniaxial Extensional Behavior of A--B--A Thermoplastic Elastomers: Structure-Properties Relationship and Modeling

    NASA Astrophysics Data System (ADS)

    Martinetti, Luca

    At service temperatures, A--B--A thermoplastic elastomers (TPEs) behave similarly to filled (and often entangled) B-rich rubbers since B block ends are anchored on rigid A domains. Therefore, their viscoelastic behavior is largely dictated by chain mobility of the B block rather than by microstructural order. Relating the small- and large-strain response of undiluted A--B--A triblocks to molecular parameters is a prerequisite for designing associated TPE-based systems that can meet the desired linear and nonlinear rheological criteria. This dissertation was aimed at connecting the chemical and topological structure of A--B--A TPEs with their viscoelastic properties, both in the linear and in the nonlinear regime. Since extensional deformations are relevant for the processing and often the end-use applications of thermoplastic elastomers, the behavior was investigated predominantly in uniaxial extension. The unperturbed size of polymer coils is one of the most fundamental properties in polymer physics, affecting both the thermodynamics of macromolecules and their viscoelastic properties. Literature results on poly(D,L-lactide) (PLA) unperturbed chain dimensions, plateau modulus, and critical molar mass for entanglement effect in viscosity were reviewed and discussed in the framework of the coil packing model. Self-consistency between experimental estimates of melt chain dimensions and viscoelastic properties was discussed, and the scaling behaviors predicted by the coil packing model were identified. Contrary to the widespread belief that amorphous polylactide must be intrinsically stiff, the coil packing model and accurate experimental measurements undoubtedly support the flexible nature of PLA. The apparent brittleness of PLA in mechanical testing was attributed to a potentially severe physical aging occurring at room temperature and to the limited extensibility of the PLA tube statistical segment. The linear viscoelastic response of A--B--A TPEs was first

  14. Extensional Failure of "Pre-Stressed" Lithosphere Above a Subduction Zone May Have Contributed to the Size of the Tohoku-Oki Earthquake and Tsunami

    NASA Astrophysics Data System (ADS)

    Buck, W. R.; Lavier, L. L.; Petersen, K. D.

    2015-12-01

    The Tohoku-oki earthquake was not only the costliest natural disaster in history it was the best monitored. The unprecedented data set showed that anomalously large lateral motion of the seafloor near the trench contributed to the size of the tsunami. Also, for the first time it was shown that a large subduction earthquake was followed by extensional aftershocks in a broad region of the upper plate (up to 250 km from the Japan Trench). Several observations suggest that the near-trench seafloor motion and the extensional aftershocks are linked. For example, a seismically imaged fault, just landward of the region of large seafloor motion, slipped in a normal sense during the earthquake. Also, inspired by the Tohoku data, researchers have searched for and found upper plate extensional aftershocks associated with several other subduction earthquakes that produced large tsunami. Extension of the upper plate can be driven by a reduction in the dip of a subducting slab. Such a dip change is suggested by the post-Miocene westward migration of the volcanic arc in Honshu. Numerical models show that a long-term reduction in slab dip can generate enough extensional stress to cause normal faulting over a broad region of the upper plate. The time step of the numerical model is then reduced to treat the inter-seismic time scale of 100-1000 years, when the subduction interface is locked. The interface dip continues to be reduced during the inter-seismic period, but extensional fault slip is suppressed by the relative compression of the upper plate caused by continued convergence. The relief of compressional stresses during dynamic weakening of the megathrust triggers a release of bending-related extensional strain energy. This extensional yielding can add significantly to the co-seismic radiated seismic energy and seafloor deformation. This mechanism is analogous to the breaking of a pre-stressed concrete beam supporting a bending moment when the compressional pre-stress is

  15. Evolution of Extensional Structures Within the Internal Parts of the Higher Himalaya (Sutlej River Region, NW India)

    NASA Astrophysics Data System (ADS)

    Hintersberger, E.; Thiede, R. C.; Strecker, M. R.

    2006-12-01

    One of the most challenging problems in understanding the tectonics of active mountain belts is the presence of normal faults in the overall compressive settings. Consistent observations in the Andes, the Alps, as well as in the Himalaya record the presence of upper crustal structures with normal displacement contemporaneously with shortening and thrusting at lower crustal levels and elevations. Within the internal and high elevation sectors of the Himalayan orogen, active N-S striking normal fault systems are well documented. Crosscutting relationships indicate that these closely spaced faults cut all pre-existing compressional structures and are the youngest structural features in this region. However, their mode of propagation in time and space, as well as their origin remain largely unknown. For example, in the Sutlej River region (NW Himalaya, India), it is unclear whether these fault systems either are a local phenomenon and related to ongoing exhumation of the Leo Pargil metamorphic dome or, alternatively, are an integral part of the structural framework in the Himalaya and thus of regional importance. To better understand which processes constrain N-S striking normal faulting in the evolution of the Higher Himalaya, we have mapped the young extensional sectors in the greater Sutlej River area. In addition, we combine seismological data with the spacial and temporal distribution of brittle normal faulting to better understand the interaction between the ongoing normal and thrust faulting in the orogen. Using globally recorded seismicity data we observed ongoing extension in a N-S striking band extending from to the Leo Pargil extensional dome southward to the main thrust belts along the Himalayan front. Further installation of a seismic network in this region will provide the level of resolution needed to analyze the detailed pattern of local seismicity of the Sutlej-Spiti River region. Our preliminary structural geological field work reveals that the

  16. K-T magmatism of western Rajasthan, India: Manifestation of Reunion plume activity or extensional lithospheric tectonics?

    NASA Astrophysics Data System (ADS)

    Sharma, K.

    2004-12-01

    A number of alkaline plutons have been recorded at the K-T (Cretaceous-Tertiary) boundary in western Rajasthan, India. Significant magmatism occurred at Mundwara, Barmer, Sarnu-Dandali and Tavider. The evolution of the Cambay-Sanchor-Barmer rift during the K-T period resulted in these alkaline complexes at the rift margins. Sedimentary basins are developed in the Barmer and Jaiselmer regions. The magmatism of Mundwara and Sarnu-Dandali is dated at 68.50 Ma and considered as an early pulse of Deccan volcanism. Several workers correlated K-T sedimentary basin evolution, magmatism and other tectonic features of western Rajasthan with the Reunion plume-interaction in the northwestern Indian shield. Alkaline igneous complexes along the rift from the southern part are reported from Phenai Mata, Amba Dongar and Seychelles. The Seychelles was part of the northwestern Indian shield prior to Deccan volcanism. The Mundwara igneous complex represents three distinct circular plutonic bodies - Toa, Mer and Mushala, which are situated in the periphery of an area three kilometers in radius. Besides these, there are numerous concentric and radial dykes of lamprophyre, carbonatite, dolerite and amphibolite. All these three bodies represent different phases of intrusion and are not similar to each other. The alkaline rocks of Sarnu-Dandali occur as dykes and isolated plugs in the desert sand. Carbonatite dykes are also reported from southeast of Barmer. The Tavider outcrop is devoid of any plutonic rock and consists of rhyolite, andesite and basalt. These rocks occur along the Precambrian Malani magmatic lineaments. The development of the Cambay-Sanchor-Barmer rift caused reactivation of Precambrian fractures and resulted in magmatism at the basin margin. The Gondwanaland fragmentation during the Mesozoic era caused extensional tectonics in the northwestern Indian shield. This led to the development of rift basins in Gujarat and western Rajasthan. Deccan volcanism, separation of the

  17. Extensional deformation of the Guadalquivir Basin: rate of WSW-ward tectonic displacement from Upper Tortonian sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Roldán, Francisco J.; Azañón, Jose Miguel; Rodríguez-Fernández, Jose; María Mateos, Rosa

    2016-04-01

    The Guadalquivir Basin (Upper Tortonian-Quaternary sedimentary infilling) has been considered the foreland basin of the Betic Orogen built up during its collision with the Sudiberian margin. The basin is currently restricted to its westernmost sector, in the Cadiz Gulf, because the Neogene-Quaternary uplift of the Betic Cordillera has produced the emersion of their central and eastern parts. The upper Tortonian chronostratigraphic unit is the oldest one and it was indistinctly deposited on the South Iberian paleomargin and the External units from the Betic Cordillera. However, these rocks are undeformed on the Sudiberian paleomargin while they are deeply affected by brittle deformation on the External Betic Zone. Outcrops of Upper Tortonian sedimentary rocks on External Betic Zone are severely fragmented showing allocthonous characters with regard to those located on the Sudiberian paleomargin. This post- Upper Tortonian deformation is not well known in the External Zones of the Cordillera where the most prominent feature is the ubiquity of a highly deformed tecto-sedimentary unit outcropping at the basement of the Guadalquivir sedimentary infilling. This tecto-sedimentary unit belongs to the Mass Wasting Extensional Complex (Rodríguez-Fernández, 2014) formed during the collision and westward migration of the Internal Zone of the Betic Cordillera (15-8,5 Ma). In the present work, we show an ensemble of tectonic, geophysical and cartographic data in order to characterize the post-Upper Tortonian deformation. For this, seismic reflection profiles have been interpreted with the help of hidrocarbon boreholes to define the thickness of the Upper Tortonian sedimentary sequence. All these data provide an estimation of the geometrical and kinematic characteristics of the extensional faults, direction of movement and rate of displacement of these rocks during Messinian/Pliocene times. References Rodríguez-Fernández, J., Roldan, F. J., J.M. Azañón y Garcia-Cortes, A

  18. Tectonics and metallogenic provinces

    USGS Publications Warehouse

    Guild, P.W.

    1983-01-01

    Various theories have been advanced to explain the well-known uneven distribution of metals and ore-deposit types in space and time. Primordial differences in the mantle, preferential concentration of elements in the crust, the prevalence of ore-forming processes at certain times and (or) places, and combinations of one or several of these factors have all been called upon to account for the "metallogenic provinces," which can be defined loosely as regions containing similar deposits of one or a group of metals or minerals. Because many, perhaps most, provinces have complex, multistage origins, the relative importance of inheritance vs. process is still controversial. In recent years the geographic relationship of many geologically young provinces to present-day plate-tectonic positions (accreting or consuming margins, intraplate structures, etc.) has been widely recognized, and the presumption is strong that older provinces had similar relationships to former plates. As most ore deposits resulted from a favorable conjunction of geological processes that are no longer operative, elucidation of their genesis requires reconstruction of the geologic history of the province, with particular emphasis on events coeval with mineralization. Tectonic analysis is an important aspect of this reconstruction; data from orbiting satellites have contributed greatly to this analysis, as the voluminous literature of the past decade testifies. Both the synoptic view of large areas and the ability to emphasize faint contrasts have revealed linear, curvilinear, and circular features not previously recognized from field studies. Some of these undoubtedly reflect basement structures that have contributed to the development, or limit the extent, of metallogenic provinces. Their recognition and delineation will be increasingly valuable to the assessment of resources available and as guides to exploration for the ores needed by future generations. ?? 1983.

  19. The effect of shear and extensional viscosities on atomization of Newtonian and non-Newtonian fluids in ultrasonic inhaler.

    PubMed

    Broniarz-Press, L; Sosnowski, T R; Matuszak, M; Ochowiak, M; Jabłczyńska, K

    2015-05-15

    The paper contains results of the experimental study on atomization process of aqueous solutions of glycerol and aqueous solutions of glycerol-polyacrylamide (Rokrysol WF1) in an ultrasonic inhaler. In experiments the different concentration aqueous solutions of glycerol and glycerol-polyacrylamide have been tested. The results have been obtained by the use of laser diffraction technique. The differences between characteristics of ultrasonic atomization for test liquids have been observed. The analysis of drop size histograms shows that the different sizes of drops have been formed during atomization process. The present study confirmed the previous reports which suggested that the drops size changes with the increase in viscosity of solution changes in spray characteristics were also observed. It has been shown that the shear and extensional viscosities affect the process of atomization.

  20. Surprisingly young Rb/Sr ages from the Simav extensional detachment fault zone, northern Menderes Massif, Turkey

    NASA Astrophysics Data System (ADS)

    Bozkurt, Erdin; Satır, Muharrem; Buğdaycıoğlu, Çağrı

    2011-12-01

    The present paper demonstrates that exposed semi-brittle-brittle detachment fault zones, in addition to footwall mylonites and syn-extensional granitoids, can be used to date the timing of faulting and constrain the history and evolution of metamorphic core complexes. We employed Rb-Sr geochronology on micas, sampled directly from a part of the Simav detachment fault (SDF) zone in the northern Menderes Massif (western Turkey). The exposed part of the fault zone is marked by ˜3-m thick zone of low-grade mylonites/foliated cataclasites, in which mylonitic fabrics in orthogneisses are overprinted by fabrics of semi-brittle deformation. The low-grade mylonites/foliated cataclasites are characterized by coexistence of brown and green biotites. Rb-Sr ages on muscovite and brown and green biotite from the low-grade mylonites/foliated cataclasites are ca. 30 Ma, 17-13 Ma and 12-10 Ma, respectively; green biotite ages are interpreted as dating fluid-assisted deformation-induced dynamic recrystallization and suggest that a part of the SDF was active during a 12-10 Ma interval. The ca. 30 Ma muscovite ages date dynamic crystallization and probably beginning of extensional exhumation of the northern Menderes Massif. The coexistence of brown and green biotites in the same sample indicates retrogressive processes associated within a detachment faulting during which green biotites have recrystallized from primary brown biotites with an age of 19 ± 2 Ma in this area. This further means that the isotopic system became opened during faulting and that the green biotite ages therefore record the activity of the SDF. We have also dated an orthogneiss sample exposed well away from the detachment fault zone (devoid of any retrogressive processes); muscovites and biotites from this sample yield Rb-Sr ages of 45.7 ± 0.6 and 18.17 ± 0.18 Ma, respectively. The biotite age is in accord with regional biotite ages (19 ± 2 Ma) and record cooling of the footwall rocks of the detachment fault

  1. Structural analysis of three extensional detachment faults with data from the 2000 Space-Shuttle Radar Topography Mission

    USGS Publications Warehouse

    Spencer, J.E.

    2010-01-01

    The Space-Shuttle Radar Topography Mission provided geologists with a detailed digital elevation model of most of Earth's land surface. This new database is used here for structural analysis of grooved surfaces interpreted to be the exhumed footwalls of three active or recently active extensional detachment faults. Exhumed fault footwalls, each with an areal extent of one hundred to several hundred square kilometers, make up much of Dayman dome in eastern Papua New Guinea, the western Gurla Mandhata massif in the central Himalaya, and the northern Tokorondo Mountains in central Sulawesi, Indonesia. Footwall curvature in profile varies from planar to slightly convex upward at Gurla Mandhata to strongly convex upward at northwestern Dayman dome. Fault curvature decreases away from the trace of the bounding detachment fault in western Dayman dome and in the Tokorondo massif, suggesting footwall flattening (reduction in curvature) following exhumation. Grooves of highly variable wavelength and amplitude reveal extension direction, although structural processes of groove genesis may be diverse.

  2. Oil Spill Dispersion Forecasting System for the Region of Installation of the Burgas Alexandroulopis Pipeline Outlet(N.E. Aegean) in the Framework of ``DIAVLOS'' Project

    NASA Astrophysics Data System (ADS)

    Tzali, M.; Sofianos, S.; Kallos, G.; Mantziafou, A.; Zafeirakou, A.; Dermisis, V.; Koutitas, Ch.; Zervakis, V.

    2010-01-01

    In the framework of the project DIAVLOS, a 48-hours oil spill dispersion forecasting system was developed and implemented in the Northern Aegean Sea aiming at oil spill dispersion management at the Burgas-Alexandroupolis oil-pipe terminal (N.E. Aegean Sea). The system is based on wind, wave and ocean circulation models coupled with the operational systems ALERMO and SKIRON of the University of Athens and an oil-spill dispersion model. The various components of the system were successfully developed, improved through sensitivity tests and coupled to form an operational oil spill dispersion forecasting system, available at an independent and interactive web-site (http://diavlos.oc.phys.uoa.gr), in order to be used by interested authorities. The system was also tested against field observations of special drifting floats that monitor the trajection and spreading of oil spills. It gives satisfactory results and in most cases the forecasting error is quite small, allowing the operational use of the system. Additionally, high-resolution atmospheric and oceanic forecasting in the region is provided, to facilitate operations to contain oil spill spreading/beaching.

  3. Molecular spectrum of α-globin gene mutations in the Aegean region of Turkey: first observation of three α-globin gene mutations in the Turkish population.

    PubMed

    Onay, Hüseyin; Aykut, Ayça; Karaca, Emin; Durmaz, Asude; Solmaz, Aslı Ece; Çoğulu, Özgür; Aydınok, Yeşim; Vergin, Canan; Özkınay, Ferda

    2015-07-01

    Molecular test results of 231 individuals referred to our molecular genetics laboratory for analysis of α-globin gene mutations between the years 2007 and 2013 were evaluated. Analysis of α-thalassemia gene mutations was performed using reverse dot-blot hybridisation, which includes 21 common mutations. Twelve distinct α-thalassemia mutations and 23 different genotypes have been detected in the Aegean region of Turkey. The most frequent mutations were -α3.7 (52.28 %), -(α)20.5 (14.74 %), --MED (10.53 %), and αPA-1α (8.77 %). Three α-thalassemia mutations (αcd142α, --SEA, and αICα), which are more prevalent in Southeast Asia, are identified for the first time in Turkey in this study. We find that a broad spectrum of α-thalassemia mutations is present in the Aegean region of Turkey. The results obtained in this study may help inform decisions in the design and implementation of prevention strategies and diagnostic approaches.

  4. An integrated zircon geochronological and geochemical investigation into the Miocene plutonic evolution of the Cyclades, Aegean Sea, Greece: part 2—geochemistry

    NASA Astrophysics Data System (ADS)

    Bolhar, Robert; Ring, Uwe; Kemp, Anthony I. S.; Whitehouse, Martin J.; Weaver, Steve D.; Woodhead, Jon D.; Uysal, I. Tonguc; Turnbull, Rose

    2012-12-01

    Zircons from 14 compositionally variable granitic rocks were examined in detail using CL image-guided micro-analysis to unravel the complex magmatic history above the southward retreating Hellenic subduction zone system in the Aegean Sea. Previously published U-Pb ages document an episodic crystallisation history from 17 to 11 Ma, with peraluminous (S-type) granitic rocks systematically older than closely associated metaluminous (I-type) granitic rocks. Zircon O- and Hf isotopic data, combined with trace element compositions, are highly variable within and between individual samples, indicative of open-system behaviour involving mantle-derived melts and evolved supracrustal sources. Pronounced compositional and thermal fluctuations highlight the role of magma mixing and mingling, in accord with field observations, and incremental emplacement of distinct melt batches coupled with variable degrees of crustal assimilation. In the course of partial fusion, more fertile supracrustal sources dominated in the earlier stages of Aegean Miocene magmatism, consistent with systematically older crystallisation ages of peraluminous granitic rocks. Differences between zircon saturation and crystallisation temperatures (deduced from zircon Ti concentrations), along with multimodal crystallisation age spectra for individual plutons, highlight the complex and highly variable physico-compositional and thermal evolution of silicic magma systems. The transfer of heat and juvenile melts from the mantle varied probably in response to episodic rollback of the subducting lithospheric slab, as suggested by punctuated crystallisation age spectra within and among individual granitic plutons.

  5. Fault-controlled sedimentation in a progressively opening extensional basin: the Palaeoproterozoic Vargfors basin, Skellefte mining district, Sweden

    NASA Astrophysics Data System (ADS)

    Bauer, Tobias E.; Skyttä, Pietari; Allen, Rodney L.; Weihed, Pär

    2013-03-01

    The Vargfors basin in the central part of the Skellefte mining district is an inverted sedimentary basin within a Palaeoproterozoic (1.89 Ga) marine volcanic arc. The fault-segmented basin formed from upper-crustal extension and subsequent compression, following a period of intense sub-marine volcanism and VMS ore formation. New detailed mapping reveals variations in stratigraphy attributed to syn-extensional sedimentation, as well as provenance of conglomerate clasts associated with tectonic activity at the transition from extension to compression. The onset of fan delta to alluvial fan sedimentation associated with basin subsidence indicates that significant dip-slip displacement accommodating rapid uplift of the intrusive complex and/or subsidence of the adjacent volcano-sedimentary domain took place along a major fault zone at the southern margin of the intrusive complex. Subsidence of the Jörn intrusive complex and/or its burial by sedimentary units caused a break in erosion of the intrusion and favoured the deposition of a tonalite clast-barren conglomerate. Clast compositions of conglomerates show that the syn-extensional deposits become younger in the south-eastern parts of the basin, indicating that opening of the basin progressed from north-west to south-east. Subsequent basin inversion, associated with the accretion to the Karelian margin, involved reverse activation of the normal faults and development of related upright synclines. Progressive crustal shortening caused the formation of break-back faults accompanied by mafic volcanic activity that particularly affected the southern contact of the Jörn intrusive complex and the northern contact of the Vargfors basin.

  6. Structural style in a young flexure-induced oblique extensional system, north-western Bonaparte Basin, Australia

    NASA Astrophysics Data System (ADS)

    Saqab, Muhammad Mudasar; Bourget, Julien

    2015-08-01

    In the north-western Bonaparte Basin (North West Shelf of Australia) Neogene to Recent flexure-induced extension superimposed obliquely over the Mesozoic rift structures. Thus, the area offers a good opportunity to investigate the dynamics and architecture of oblique extension fault systems. Analysis of basin-scale 2D and 3D seismic data along the Vulcan sub-basin shows that Neogene deformation produced a new set of extensional, en échelon faults, at places accompanied by the reactivation of the Mesozoic faults. The pre-existing Mesozoic structures strongly control the distribution of the Neogene-Recent deformation, both at regional and local scales. Main controls on the Neogene-Recent fault style, density and segmentation/linkage include: (1) the orientation of the underlying Mesozoic structures, (2) the obliqueness of the younger extension relative to the rift-inherited faults, and (3) the proximity to the Timor Trough. Three types of vertical relationships have been observed between Mesozoic and Neogene-Recent faults. Hard linkages seems to develop when both fault systems trend parallel, therefore increasing risks for trap integrity. It is suggested that the orientation of maximum horizontal stress (SHmax) relative to the Mesozoic faults, forming hydrocarbon traps, is critical for their potential seal/leak behaviour. Stratigraphic growth across the faults indicates that main fault activity occurred during the Plio-Pleistocene, which corresponds to the timing of tectonic loading on Timor Island and the development of lithospheric flexure. Synchronism of normal faulting with flexural bending suggests that extensional deformation on the descending Australian margin accompanied the formation of the Timor Trough.

  7. 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

    NASA Astrophysics Data System (ADS)

    Sykioti, Olga; Florou, Heleni

    2014-05-01

    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

  8. Depositional environment, foraminifer content and ESR ages of Quaternary Gediz Delta Sediments (Eastern Aegean Sea, İzmir-Western Turkey)

    NASA Astrophysics Data System (ADS)

    Gökçe Benli, Ekin; Aydın, Hülya; İşintek, İsmail; Engin, Birol; Şengöçmen, Berna

    2016-04-01

    Sediments and fossil content of Gediz Delta (Eastern Aegean Sea - İzmir) were examined based on the drilling core samples of the YSK-C and SK-246 drilling. W-SW part of the Delta is represented by continental delta sediments up to 6 meters and shallow marine detritic sediments up to 35 meters in the YSK-C drilling. Continental part consists of an soiled, graveled, muddy and sandy sediment in terms of rich organic substance. As for marine part, it consists of bioclast, muddy, fine graveled sand and by repetition of pebble, sand and bioclast bearing mud layers. Bioclasts comprise of bivalvia, echinoid, ostracod, gastropod, foramifer and bryozoa fragments. Benthic foraminiferal fauna determinated in the marine levels are represented by 55 bethic, 2 planktonic species. These foraminifers and bioclasts reflect that the W-SW part of the delta, has been occured in marine conditions between 8-31m deep. E-NE part of the delta is generally represented by continental sediments up to 43.5m in SK-246 drilling. In addition, it includes marine levels in 18-19 m, 23-24 m and 36-37,5 m intervals. Continental sediments of E-NE part is generally represented by calcareous and sandy mud rocks which mostly includes ash, tuff, and pebble derived from Neogene volcanic rocks. As for marine levels, it is composed of calcareous mud stones and calcareous clay stones including very thin gastropod, bivalvia and ostracod in 18- 19 and 36-37.5 meters whereas it is represented by sandy mud stones including a great deal of bentic foraminifer, bivalvia, bryozoa, echinoid, gastropod in 23-24 metres. Thus show that E-NE part of the delta is usually in continental condition but it is occasionally covered by sea. In aging studies of YSK-C core done by ESR method, age of 8-9 m interval is determined to be 11. 376 ± 0,067 Ka; however ages of 10-11m and 24-25 m intervals are revealed to be 16.466 ± 0,016 Ka and 15.344 ± 0,021 Ka respectively; finally age of 25-26 m interval is found to be 19.995 ± 0

  9. Evolution and fluxes of 137Cs in the Black Sea/Turkish Straits System/North Aegean Sea

    NASA Astrophysics Data System (ADS)

    Delfanti, R.; Özsoy, E.; Kaberi, H.; Schirone, A.; Salvi, S.; Conte, F.; Tsabaris, C.; Papucci, C.

    2014-07-01

    The vertical profiles of 137Cs were determined in the North Aegean, Marmara and Black Seas, to assess inventories and fluxes of the radionuclide in these basins. The inventory of 137Cs in the Western Black Sea integrated from the surface down to 400 m water depth is 3.4 ± 0.1 kBq m- 2, which is surprisingly close to the amount determined in 1988, decay corrected to 2007 (2.9 ± 0.1 kBq m- 2). On the other hand, based on the comparison of profiles roughly 20 years apart, it is estimated that about 1 kBq m- 2 has been transferred from above the halocline to depths below the halocline, emphasizing the effective redistribution of tracers within the same period. We estimate that about 12 TBq y- 1 of 137Cs presently leaves the Black Sea with the upper layer flow through the Bosphorus and only 2 TBq y- 1 is returned with the lower layer inflow of Mediterranean water from the Marmara Sea. Accounting for river fluxes, estimated on the order of 2 TBq y- 1 few years after the Chernobyl accident, and possibly decreased by now, we can thus estimate a net rate of loss of about 8-10 TBq y- 1. Investigating the effective redistribution in the upper water column, the supply by the inflowing Mediterranean water alone does not explain the increase of 137Cs concentration and inventory at intermediate depths in the Western Black Sea. The most important mechanism transferring 137Cs and dissolved contaminants from the surface water to the sub-pycnocline layer appears to be the turbulent entrainment of a larger quantity of Black Sea water into the inflowing plume of Mediterranean water through mixing processes on the southwestern shelf and continental slope following its exit from the Bosphorus. This process produces an extra export of some10 TBq y- 1 of 137Cs from the surface to the sub-pycnocline depths of the Black Sea, a quantity comparable in magnitude to the total export out from the basin. It is the entrainment flux resulting from the mixing, and the further advection and

  10. Quaternary tectonic and sedimentary history of the shelf area between the Saros and Edremit Troughs, NE Aegean Turkey

    NASA Astrophysics Data System (ADS)

    Alpar, B.

    2009-04-01

    On the basis of new swath bathymetric and high-resolution sparker reflection data, Quaternary tectonic and sedimentary history of the Aegean continental shelf area between the gulfs of Saros and Edremit was investigated. These gulfs accommodate two complex neotectonic structures which control the major geodynamic processes in the region; these are the northern and middle strands of the North Anatolian fault (NAF), respectively. A mature erosion surface, partially intersected by some vertical faults, can indeed be interpreted from the clear reflections over the Miocene basement, which is represented by various folded layers. This acoustical surface forms the base level of deposition for the studied shelf area and overlain by various depositional basins elongated between the gulfs of Saros and Edremit. Depending on the global sea level changes, water exchange between the seas of Mediterranean and Marmara, and partly on some terrestrial inputs, these basins have been developed. Sea-level decreased during the glacial stages while the Mediterranean conditions prevailed during the interglacial stages. As evidenced from the formation of the Pleistocene coastal terraces in the Canakkale (Dardanelles) Strait region and under the control of compressional forces along the NAF zone a regional uplift of 0.2-0.9 mm per year is another major component in the tectonic history. The depositional units over the mature Pliocene erosion surface were mainly controlled by the fluvial discharges of the Karamenderes paleo-river and some others during the postglacial times, by sea-level oscillations which determined the proximity of basins to river mouths, and by oceanographic conditions. A rise in basement has been traced at 60-65 m below the modern sea level which has been played an important role in the sediment transportation occurred at the exit of the Canakkale Strait. The folded layers above the acoustical basement coincide with the development of the transpressional Anafartalar

  11. Re-examination of models for the origin of granite-rhyolite provinces in the midcontinent region, USA

    SciTech Connect

    Van Schmus, W.R. . Dept. of Geology)

    1993-03-01

    New isotopic data for the 1.47 Ga Eastern Granite-Rhyolite Province and the 1.37 Ga Southern Granite-Rhyolite Province require re-examination of models for the origin of these suites of rock. For the most part, eNd(t) values for the granite-rhyolite provinces and A-type plutons intrusive into adjacent Early proterozoic basement are compatible with origin through melting of 1.8 Ga continental crust. However, new data shows that southeastern parts of the granite-rhyolite provinces yield positive [var epsilon]Nd(t) data is an E-W trending belt of intermediate values in northern Oklahoma; [var epsilon]Nd(t) data south of this belt, in s. Oklahoma, are equivalent to that in Kansas and Nebraska, reflecting cal 1.8 Ga lower crust. The granite-rhyolite provinces are not related to any well defined tectonic event, and they have commonly been referred to as anorogenic. The thermal event responsible for producing the silicic melts may have been associated with an extensional regime, in view of the a-type character of the granites.

  12. Using Facilities And Potential Of Geothermal Resources In The Canakkale Province - NW Turkey

    NASA Astrophysics Data System (ADS)

    Deniz, Ozan; Acar Deniz, Zahide

    2016-04-01

    Turkey, due to its geological location, has a rich potential in point of geothermal resources. Çanakkale province is located northwestern (NW) part of Turkey and it has important geothermal fields in terms of geothermal energy potential. Geothermal resources reach to the surface both effects of past volcanic activity and extensions of fault zones associated with complex tectonic systems in the region. The aim of this study is to summarize hydrogeochemical characteristics, using facilities and potential of hot springs and spas located in the Çanakkale province. There are 13 geothermal fields in the region and the surface temperatures of hot springs are ranging between 28 centigrade degree and 175 centigrade degree. Hydrogeochemical compositions of thermal water display variable chemical compositions. Na, Ca, SO4, HCO3 and Cl are the dominant ions in these waters. Thermal waters of Tuzla and Kestanbol geothermal fields which is located the near coastal area can be noted NaCl type. Because these two geothermal waters have high TDS values, scaling problems are seen around the hot springs and pipelines. Geothermal waters in the province are meteoric origin according to oxygen-18, deuterium and tritium isotopes data. Long underground residence times of these waters and its temperatures have caused both more water - rock interaction and low tritium values. Geothermal energy is utilized in many areas in Turkey today. It is generally used for space heating, balneotherapy and electricity generation. Explorations of geothermal resources and investments in geothermal energy sector have risen rapidly in the recent years particularly in western Turkey. High-temperature geothermal fields are generally located in this region related to the Aegean Graben System and the North Anotalian Fault Zone. All geothermal power plants in Turkey are located in this region. Considering the Çanakkale province, most geothermal fields are suitable for multipurpose usage but many of them have

  13. Upper Cretaceous-Paleocene extensional phase in the Golfo San Jorge basin (Argentina): Growth-fault model, paleoseismicity and paleostress analysis

    NASA Astrophysics Data System (ADS)

    Foix, Nicolás; Paredes, José Matildo; Giacosa, Raúl Eduardo

    2012-02-01

    A total of 170 synsedimentary normal faults preserved in the marine Salamanca Formation (Early Paleocene of the Golfo San Jorge basin) were described from exposures of the Northern Flank of the basin. The result of the paleostress analysis of those normal faults indicates an NE-SW (49°) extensional direction during Early Paleocene times. Synsedimentary normal faults and seismites in the unit demonstrate the occurrence of an extensional tectonic event coeval with the deposition of the Salamanca Formation. Available 3D seismic surveys of the subsurface of the basin allowed recognizing asymmetric, fault-bounded Upper Cretaceous-Paleocene depocentres, identifying at least two main tectonic pulses in this extensional phase. The mapping of normal faults from seismic attributes (e.g. time slices) is WNW-ESE (278°-98°), a trend that apart significantly from outcrop results. The major faults in the subsurface that affect the Early Paleocene succession are the result of the extensional reactivation of Lower Cretaceous normal faults, which are mainly related to pre-existing structures in the basement of the basin. The D/L ratio of normal faults in the subsurface give smaller values than those based on theoretical relationships, being considered as sub-displaced normal faults. These low D-L values imply that the length of the major Paleocene faults was reached earlier by inheritance of previous faults. In addition, the subsurface lengths of faults allowed estimating paleoearthquake magnitudes greater to M ≈ 5 from empirical relations, matching with previous results obtained from the analysis of soft-sediment deformational structures preserved in the Salamanca Formation. This study displays at several scales the nature, origin and tectonic products of the Upper Cretaceous-Paleocene extensional phase in the Golfo San Jorge basin.

  14. Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?

    NASA Astrophysics Data System (ADS)

    Koppers, Anthony A. P.; Staudigel, Hubert; Pringle, Malcolm S.; Wijbrans, Jan R.

    2003-10-01

    South Pacific intraplate volcanoes have been active since the Early Cretaceous. Their HIMU-EMI-EMII mantle sources can be traced back into the West Pacific Seamount Province (WPSP) using plate tectonic reconstructions, implying that these distinctive components are enduring features within the Earth's mantle for, at least, the last 120 Myr. These correlations are eminent on the scale of the WPSP and the South Pacific Thermal and Isotopic Anomaly (SOPITA), but the evolution of single hot spots emerges notably more complicated. Hot spots in the WPSP and SOPITA mantle regions typically display intermittent volcanic activity, longevities shorter than 40 Myr, superposition of hot spot volcanism, and motion relative to other hot spots. In this review, we use 40Ar/39Ar seamount ages and Sr-Nd-Pb isotopic signatures to map out Cretaceous volcanism in the WPSP and to characterize its evolution with respect to the currently active hot spots in the SOPITA region. Our plate tectonic reconstructions indicate cessation of volcanism during the Cretaceous for the Typhoon and Japanese hot spots; whereas the currently active Samoan, Society, Pitcairn and Marquesas hot spots lack long-lived counterparts in the WPSP. These hot spots may have become active during the last 20 Myr only. The other WPSP seamount trails can be only "indirectly" reconciled with hot spots in the SOPITA region. Complex age distributions in the Magellan, Anewetak, Ralik and Ratak seamount trails would necessitate the superposition of multiple volcanic trails generated by the Macdonald, Rurutu and Rarotonga hot spots during the Cretaceous; whereas HIMU-type seamounts in the Southern Wake seamount trail would require 350-500 km of hot spot motion over the last 100 Myr following its origination along the Mangaia-Rurutu "hotline" in the Cook-Austral Islands. These observations, however, violate all assumptions of the classical Wilson-Morgan hot spot hypothesis, indicating that long-lived, deep and fixed mantle

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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

  16. Extensional Detachment faulting in melange rocks. Plurikilometres migration by W the External Zone (Cordillera Bética, Spain)

    NASA Astrophysics Data System (ADS)

    Roldán, Francisco Javier; Azañon, Jose Miguel; Rodríguez, Jose; Mateos, Rosa Maria

    2014-05-01

    The synthesis and correlation of units carried out in the continuous geological map (Roldán et al., 2012), has revealed a fragmentation of the carbonate outcrops belong to the Subbetic Domain (García-Hernández et al., 1980). Subbetic NW verging thrust and fold axial traces have not lateral continuity and Jurassic carbonate outscrops appear as klippes on the olistotromic unit. These ductile structures that can be observed in the internal structure of these jurassic blocks are unrelated to the brittle-ductile deformation bands observed at the basal pelitic levels. Basal detachments are rooted in: a) the Olistostromic unit, a Upper Langhian-Lower Serravallian breccia constituted by gypsum-bearing clay and marls; b) Cretaceous-Tertiary marly sedimentary rocks (Rodríguez-Fernández, et al., 2013) . In both kind of rocks, cataclastic structures allows to infer a top-to-the WSW displacement. Paleostress measurements, made on these detachments levels, are compatible with a extensional regime (Roldán et al., 2012). At the same time, the analysis and interpretation of subsurface data (seismic surveys and borehole testing) shows that the Subbetic Domain (External Subbetic, Molina 1987) are affected by westward low-angle normal faults. A balanced cross-section, based on morphological and cartographic data in the area between Sierra de Cabra and Sierra de Alta Coloma (Valdepeñas de Jaén), shows plurikilometric displacements which has been produced during Late Serravallian-Early Tortonian times. References: García-Hernández, M., López-Garrido, A.C., Rivas, P., Sanz de Galdeano, C., Vera, J.A. (1980): Mesozoic paleogeographic evolution of the zones of the Betic Cordillera. Geol. Mijnb. 59 (2). 155-168. Molina, J.M. (1987). Análisis de facies del Mesozoico en el Subbético. Tesis Doctoral, Univ. Granada. 518 p. Rodríguez-Fernández, J., Roldán, F. J., Azañón, J.M. y García-Cortés, A. (2013). El colapso gravitacional del frente orogénico a lpino en el Dominio Subb

  17. The Late Cretaceous I- and A-type granite association of southeast China: Implications for the origin and evolution of post-collisional extensional magmatism

    NASA Astrophysics Data System (ADS)

    Zhao, Jiao-Long; Qiu, Jian-Sheng; Liu, Liang; Wang, Rui-Qiang

    2016-01-01

    We present new geochronological, mineralogical, and geochemical data for granitic plutons that crop out within the Zhoushan archipelago, northeastern coastal Zhejiang Province, in order to constrain their origin, and the genetic relationship between the I- and A-type granites. These granites can be divided into two groups: (1) the northern I-type Putuoshan (PTS) and Dadong'ao (DDA) plutons; and (2) the southern A-type Daqingshan (DQS), Taohuadao (THD), and Xiazhidao (XZD) plutons. Zircon LA-ICP-MS U-Pb dating yielded ages of 98-96 Ma for the northern I-type plutons and 89-86 Ma for the southern A-type plutons. All of these granites are highly siliceous, K-rich, and have similar total alkali and total rare earth element (REE) abundances. However, there are also geochemical differences between the I-type and the A-type granites. The northern I-type alkali-feldspar granites are high-K calc-alkaline, metaluminous to mildly peraluminous, contain low concentrations of the high field strength elements (HFSE; e.g., Nb, Ta, Zr, and Hf), and have low Ga/Al ratios (2.04-2.44). In contrast, the southern A-type granites are peralkaline and F-rich, and have lower CaO and Al2O3 concentrations, and higher Fe2O3T and HFSE concentrations and Ga/Al ratios (3.25-3.86). Meanwhile, they have slightly higher heavy REE (HREE) concentrations, and are more depleted in Ba, Sr, P, Ti, and Eu than the northern I-type granites. Both the I- and A-type granites have homogeneous whole-rock Nd and highly variable zircon Hf isotopic compositions. Of note, the southern peralkaline A-type granites appear to have more radiogenic Nd and Hf isotope compositions than the northern I-type granites. The present data, together with the results of a previous study on mafic enclaves within the PTS pluton, suggest that the northern I-type alkali-feldspar granites were generated by mixing of mantle-derived material with crustal-derived magmas that formed by dehydration melting of mica-bearing basaltic rocks

  18. Syn-orogenic extensional pulses within the contractional history of thrust wedges. The Val di Lima low-angle normal fault case study, Northern Apennines, Italy.

    NASA Astrophysics Data System (ADS)

    Clemenzi, Luca; Molli, Giancarlo; Storti, Fabrizio; Muchez, Philippe; Swennen, Rudy; Torelli, Luigi

    2014-05-01

    In this contribution we describe the Val di Lima low-angle fault system, a kilometric-scale extensional structure exposed in the central sector of the Northern Apennines thrust wedge, Italy. The low-angle extensional fault system delaminates the right-side-up limb of a km-scale recumbent isoclinal anticline that affects the carbonate-dominated Late Triassic to early Early Miocene non-metamorphic Tuscan succession. The low-angle fault system, in turn, is affected by superimposed folding and late-tectonic high-angle extensional faulting. The three-dimensional configuration of the low-angle fault system has been investigated through detailed structural mapping and restoration of the superimposed deformations, while the fault damage zone architecture has been characterized in outcrops with appropriate exposure. Pressure-depth conditions and palaeofluid evolution of the fault system have been studied through microstructural, mineralogical, petrographic, fluid inclusion and stable isotope analysis of fault rocks and fault-related calcite and quartz veins. Our results show that the low-angle fault system was active during exhumation of the Tuscan succession, at estimated conditions of about 180°C and 5.2 km depth. The fault system had a twofold influence on fluid circulation within the orogenic wedge: i) it allowed the migration of low-salinity fluids, due to the increased permeability along the fault zone; ii) it favored footwall fluid overpressures where the fault core acted as an efficient hydraulic barrier. Abundant fluid circulation in fault damage zones also characterized the late-stage evolution of the low-angle fault system, allowing the recrystallization of calcite veins and limestone host rocks at shallower conditions (~ 4 km). Within this P-T framework, the fault zone architecture shows important differences, related to the different lithologies involved in the fault system and to the role played by the fluids during deformation. In particular, footwall fluid

  19. Late Miocene extensional tectonics in the evolution of the eastern Betics and Neogene-Quaternary basins, an example from the Sorbas basin (SE Spain).

    NASA Astrophysics Data System (ADS)

    Giaconia, Flavio; Booth-Rea, Guillermo; Martínez-Martínez, José Miguel; Azañón, José Miguel

    2013-04-01

    Neogene to Quaternary basins in the eastern Betics occur in synclines among near E/W-elongated antiformal ridges where the metamorphic basement crops out. These antiforms are related to or cut by large-scale strike-slip faults, both developed in response of the NW-SE Africa-Iberia convergence. Most literature associated the origin and evolution of the Neogene-Quaternary eastern Betics basins with this transpressional strike-slip regime. However, recent work showed the great importance of extensional tectonics in the development and evolution of these basins during the middle to late Miocene. In order to define the role of Miocene extensional tectonics in the origin and evolution of Neogene - Quaternary basins, we have carefully mapped a key area in the southeastern Betics, the western termination of Sierra Cabrera. We analyzed the age and linking relationships between brittle fault segments, and finally we constructed a balanced cross section. We identified a NW-SE listric normal fault system that was active during the Tortonian producing southwestward hanging-wall displacement. These normal faults show hard linkage relationships with E-W to N70E vertical strike-slip and oblique-slip extensional transfer faults that show both dextral and sinistral kinematics. The balanced cross section shows that listric faults probably join together into a basal detachment (about 1 km depth) inside the metamorphic basement (Nevado-Filabride complex). The fault system influenced the Tortonian sedimentary evolution of the Sorbas Basin controlling the sediments thickness. The early Tortonian sedimentary unit is missed in the hangingwall of the fault system, meanwhile the thickness of late Tortonian sediments deposited between 11 and 8 Ma change across the main faults from approximately 200 m thick in the footwall of the system to up to 800 m in the main depocentre. Furthermore, the fault system controlled the Tortonian sedimentary facies shifting from continental and deltaic

  20. Extensional Basins in a Convergent Margin: Oligocene-Early Miocene Salar de Atacama and Calama basins, Central Andes

    NASA Astrophysics Data System (ADS)

    Jordan, T. E.; Mpodozis, C.; Blanco, N.; Pananont, P.; Dávila, F.

    2004-12-01

    The Salar de Atacama Basin (SdAB) is the largest and most persistent sedimentary basin of northern Chile, accumulating nonmarine sediment from Cretaceous to modern times. Its northwestern neighbor, the Calama, was a Cenozoic basin. Although SdAB was in the backarc zone early in the Andean orogeny, both are now forearc basins. Others demonstrated that the basins overlie anomalously cold, strong, and dense crust and lithosphere. We focus on an extensional Oligocene basin stage. Interpretation of the basin-controlling faults is based on seismic reflection studies supported by field relations. The SdAB is limited to the west by the NNE-trending, steeply east-dipping, Paciencia Fault (PF). The PF experienced 5-7 km of down-to-the-east offset during the Oligocene-early Miocene. Syntectonic strata, an arid succession of siliciclastics and evaporites, are asymmetric, with thicknesses of 5000 m and abundant halite adjacent to the PF, and of 1000 m with fine detrital clastic strata 25 km farther east. Relations in conglomeratic growth strata that overlap the PF also demonstrate normal displacement during sediment accumulation. Seismic data reveal that a buried normal fault with 1-1.5 km down-to-the-east displacement limits the western margin of the Oligocene-Miocene Calama siliciclastic basin fill. Regionally, Oligocene-early Miocene margin-parallel strike-slip deformation dominated northwest of the basins, contributing sinistral offset (West Fissure Fault) to the northern segment of the long-lived Domeyko Fault System. The new SdAB and Calama data reveal that a 20,000 km2 domain of extensional basins existed within the dominantly strike-slip region. Even if PF and the fault in the Calama Basin were transtensional, the proportion of extension to strike-slip displacement is much greater in these basins than elsewhere in northern Chile. Further study is required to understand what combination of factors caused this kinematic distinction as well as delayed the onset of CVZ

  1. Early Miocene Kirka-Phrigian caldera, western Anatolia - an example of large volume silicic magma generation in extensional setting

    NASA Astrophysics Data System (ADS)

    Seghedi, Ioan; Helvacı, Cahit

    2014-05-01

    Large rhyolitic ignimbrite occurrences are close connected to the Early Miocene initiation of extensional processes in the central-west Anatolia along Taşvanlı-Afyon zones. Field correlations, petrographical, geochemical and geochronological data lead to a substantial reinterpretation of the ignimbrite surrounding Kırka area, known from its world-class borate deposits, as representing the climatic event of a caldera collapse, unknown up to now and newly named "Kırka-Phrigian caldera". The caldera, which is roughly oval (24 km x 15km) in shape, one of the largest in Turkey, is supposed to have been formed in a single stage collapse event, at ~19 Ma that generated huge volume extracaldera outflow ignimbrites. Transtensive/distensive tectonic stresses since 25 Ma ago resulted in the NNW-SSE elongation of the magma chamber and influenced the roughly elliptical shape of the subsided block (caldera floor) belonging to the apex of Eskişehir-Afyon-Isparta volcanic area. Intracaldera post-collapse sedimentation and volcanism (at ~ 18 Ma) was controlled through subsidence-related faults with generation of a series of volcanic structures (mainly domes) showing a large compositional range from saturated silicic rhyolites and crystal-rich trachytes to undersaturated lamproites. Such volcanic rock association is typical for lithospheric extension. In this scenario, enriched mantle components within the subcontinental lithospheric mantle will begin to melt via decompression melting during the initiation of extension. Interaction of these melts with crustal rocks, fractionation processes and crustal anatexis driven by the heat contained in the ascending mantle melts produced the silicic compositions in a large crustal reservoir. Such silicic melts generated the initial eruptions of Kırka-Phrigian caldera ignimbrites. The rock volume and geochemical evidence suggests that silicic volcanic rocks come from a long-lived magma chamber that evolved episodically; after caldera

  2. Active Extensional Faulting at the Southern Half-Graben Belt of the Tepic-Zacoalco Rift, Western Mexico

    NASA Astrophysics Data System (ADS)

    Rosas-Elguera, J.; Ferrari, L.; Delgado, M.; Uribe, A.; Valdivia, L.; Castillo, R.

    2003-12-01

    In the past decade much debate has centered upon the kinematics and the mechanism of continental deformation in western Mexico and the motion of the Jalisco block relative to North America. Two distinct models have been proposed. The first one suggest a NW-motion of the Jalisco block that would implies a right-lateral faulting along the Tepic-Zacoalco rift (TZR). More recently others authors have documented a N-NE extensional tectonics active since late Miocene and suggested that the continental boundaries of the Jalisco block, are older structures reactivated by plate boundary forces. Studies on the crustal seismicity and the kinematics of Quaternary faults provide another constraint on the direction of motion between the Jalisco block and North America. On November 4, 5, 6, and 7, 1995, one month after the October 09, 1995, Manzanillo earthquake (Mw = 8.0), a swarm of small events was felt in the Amatlan de Ca¤as half-graben and recorded by the regional seismic network of Comision Federal de Electricidad. The coda magnitude of the largest event was Mc = 2.5-3.6 and the events were located depth ranging from 6 to 10 km. This seismic activity provoked that people from Pie de la Cuesta and Yerbabuena villages were evacuated. After that a seismic station equipped with an analogic seismograph MEQ-800 at Pie de la Cuesta was installed for three months. During the same time, October, 1995, some houses distributed along a WNW trend in Ameca city underwent severe damages, they are. The digital elevations model of the Ameca city suggest that several structures tectonics are shorter than 2 km are present in the area. The present direction of motion of the Rivera plate relative to North America plate along Middle America Trench has been estimated between N19° E to N48° E (e.g. Bandy et al., 1996). During the October 09, 1995, subduction-related earthquake (Mw = 8.0) a GPS network recorded a SW motion of the Jalisco block which could be associated to an elastic deformation

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

    NASA Astrophysics Data System (ADS)

    Yalçın, Hilal; Kürçer, Akın; Gülen, Levent

    2016-04-01

    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

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

    NASA Astrophysics Data System (ADS)

    Yalçın, Hilal; Kürçer, Akın; Gülen, Levent

    2016-04-01

    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

  5. The advance of Kos Plateau Tuff ignimbrite into the marine realm of the Kalymnos Basin, SE Aegean Sea.

    NASA Astrophysics Data System (ADS)

    Markakis, Emmanouil; Anastasakis, George

    2013-04-01

    The 161 ka Kos Plateau Tuff (KPT) eruption is considered to be the largest explosive Quaternary event in the eastern Mediterranean. It produced pumice rafts followed by "non-welded ignimbrites" that are up to 30m thick, especially widespread on Kos island and covering an area of > 80 Km2 that includes mainly islands and present marine regions. Pyroclastic flows travelled from the proposed vent, that lies between and around Yali and Nisyros islands, across present land and sea, the total volume of the tuff has been estimated as at least 100km3. KPT products principally consist of rhyolitic ash and pumice. Post 2010 Athens University oceanographic missions have mapped the seafloor around the volcanic islands of the SE Aegean Sea. Here we present new data on seafloor morphology and Upper Quaternary seafloor stratigraphy of the Kalymnos basin that extends over an area over 70km2 and map the advance and deposition of the KPT that was previously unknown in this region. The Kalymnos basin is roughly triangular in shape and essentially consists of two sedimentation depocenters: a) a roughly elliptical 400 m deep northern segment that is developed sub-parallel to Kalymnos Island and its W-SW shelf; b) a rather physiographically complex western sector developed NE of Astipalea island and reaching depths of over 620m. High resolution sparker profiles from the west Kos-Kalymnos shelf reveal an outstanding seismic stratigraphy of stacked and prograded coastal clinoform packets capped by erosional transgressive surfaces that record Quaternary eustatic lowstands deposits of sea level with clinoforms developing during forced regression and the erosional surfaces during transgression. We show that a massive gravity flow deposit is intercalated with the shelf sediments. Above it low sea level MIS 6 and 2 sedimentary sequences are fully developed and below stage 8-10 sediments are erratically preserved over stages 12 and 16 sediments. This gravity flow deposit swept across the shelf

  6. Recurrent intrusions of transitional waters of Eastern Mediterranean origin in the Cretan Sea as a tracer of Aegean Sea dense water formation events

    NASA Astrophysics Data System (ADS)

    Velaoras, Dimitris; Krokos, George; Theocharis, Alexander

    2015-06-01

    Available temperature and salinity data in the Cretan Sea from 1955 up to 2014 as well as literature sources were revisited in order to trace the appearance of low salinity, temperature, oxygen and nutrient-rich waters inside the basin at depths below the intermediate layer. First appearing as far back as 1961 in literature, these waters were found originating in the layers that separate intermediate and deep waters of the Eastern Mediterranean Sea (EMed) and were named Transitional Mediterranean Water (TMW) in the 1990s. Data analysis showed that the appearance of TMW in the Cretan Sea is a recurrent phenomenon connected to water mass exchanges between the Aegean Sea and the EMed. In particular, the inflow of TMW in the Cretan basin acts as compensation for the outflow of equally dense or denser masses from the Aegean. This export is a result of dense water formation (DWF) events taking place inside the Aegean Sea triggering TMW compensatory inflow into the Cretan Sea through the Cretan Straits. In this context, TMW intrusions in the Cretan basin can be used as a tracer of DWF in the Aegean Sea while the depth of the intrusion can provide valuable information about the intensity of the DWF event. The importance of TMW intrusions is not solely restricted to the tracing and evaluation of DWF events but could additionally expand to the impact on local ecological processes as TMW is a nutrient carrier for the oligotrophic Cretan Sea. It is obvious that this low salinity, temperature and oxygen layer is what was later named TMW. The core temperature, salinity and oxygen values reported by Miller (1974) fall within the range of values observed during the PELAGOS project in 1994, as noted in Section 'Presence of low salinity water masses below the intermediate layer in the Cretan Sea during the EMT event'. Using the same dataset provided by MEDATLAS 2002 database, a salinity transect along the Cretan Sea is reconstructed in Fig. 5. The bottle data originate from the

  7. Eastern-Mediterranean ventilation variability during sapropel S1 formation, evaluated at two sites influenced by deep-water formation from Adriatic and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Filippidi, A.; Triantaphyllou, M. V.; De Lange, G. J.

    2016-07-01

    Present-day bottom-water ventilation in the Eastern Mediterranean basin occurs through deep-water convection originating from the two marginal basins, i.e. Adriatic and Aegean Seas. In the paleo record, long periods of enhanced deep-water formation have been alternating with shorter periods of reduced deep-water formation. The latter is related mainly to low-latitude humid climate conditions and the enhanced deposition and preservation of organic-rich sediment units (sapropels). This study focuses on sedimentary archives of the most-recent sapropel S1, retrieved from two sites under the direct influence of the two deep-water formation areas. Restricted oxygen conditions have developed rapidly at the beginning of S1 deposition in the Adriatic site, but bottom-water conditions have not persistently remained anoxic during the full interval of sapropel deposition. In fact, the variability in intensity and persistence of sedimentary redox conditions at the two deep-water formation sites is shown to be related to brief episodes of climate cooling. In the Adriatic site, sapropel deposition appears to have been interrupted twice. The 8.2 ka event, only recovered at the Adria site, is characterized by gradually increasing suboxic to possibly intermittently oxic conditions and decreasing Corg fluxes, followed by an abrupt re-establishment of anoxic conditions. Another important event that disrupted sapropel S1 formation, has taken place at ca. 7.4 cal ka BP. The latter event has been recovered at both sites. In the Adriatic site it is followed by a period of sedimentary conditions that gradually change from suboxic to more permanently oxic, as deduced from the Mn/Al pattern. Using the same proxy for suboxic/oxic sedimentary redox conditions, we observe that conditions in the Aegean Sea site shift to more permanently oxic from the 7.4 ka event onwards. However, at both sites the accumulation and preservation of enhanced amounts of organic matter have continued under these

  8. The first isolation of Cryptococcus neoformans from Eucalyptus trees in South Aegean and Mediterranean Regions of Anatolia in Turkey despite Taurus Mountains alkalinity.

    PubMed

    Ergin, Cağri; Ilkit, Macit; Hilmioğlu, Süleyha; Kaleli, Ilknur; Gülbaba, A Gani; Demirci, Mustafa; Kaya, Selçuk

    2004-07-01

    Eucalyptus trees are widespread in subtropical parts of Turkey that have alkaline environments due to the soil structure of Taurus Mountains. In this study, the existence of Cryptococcus neoformans in eucalyptus trees in the South Aegean and Mediterranean Regions of Anatolia, Turkey, was screened between March 1998 and September 2002. Only one strain of Cryptococcus neoformans var. grubii (Serotype A) was isolated from 1175 eucalyptus samples including debris and flowers in culture by Guizotia abyssinica agar. The environmental niche of the isolate was Eucalyptus camaldulensis Dehn in the Gokova Region, in the western part of the Taurus Mountains. In this study, the existence of Cryptococcus neoformans was shown in the eucalyptus flora of Turkey despite the alkaline soil condition. PMID:15487319

  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

    USGS Publications Warehouse

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

    1986-01-01

    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. Molecular Basis of β-Thalassemia in the Population of the Aegean Region of Turkey: Identification of A Novel Deletion Mutation.

    PubMed

    Ozkinay, Ferda; Onay, Huseyin; Karaca, Emin; Arslan, Esra; Erturk, Biray; Ece Solmaz, Asli; Tekin, Ismihan Merve; Cogulu, Ozgur; Aydinok, Yeşim; Vergin, Canan

    2015-01-01

    β-Thalassemia (β-thal) is the most common monogenic disorder in Turkey. The aim of this study was to investigate the spectrum of β-thal mutations in the Aegean region of Turkey. The data was derived from 1171 unrelated β-thal subjects, detected in a regional reference hospital between November 2004 and December 2013. Screening for the 22 common mutations was performed using the polymerase chain reaction (PCR)-reverse dot-blot method, and direct automated DNA sequencing for the unknown samples. Thirty-one different β-thal alleles were identified. Seven mutations, namely IVS-I-110 (G > A) (41.7%), IVS-I-1 (G > A) (8.9%), IVS-II-745 (C > G) (8.6%), codon 8 (-AA) (7.7%), IVS-II-1 (G > A) (7.2%), IVS-I-6 (T > C) (6.6%), codon 39 (C > T) (4.6%) accounted for 85.3% of the mutated alleles. Frequencies of the remaining 24 β-thal mutations were less than 2.2%; these included one novel mutation [HBB: c.206_212del (p.Leu69Profs*19)], and four others [-56 (G > C), codon 16 (-C), IVS-I (-3) (C > T) (codon 29), codon 76 (-C)] found in Turkey for the first time. The results will help to prevent severe β-thal through genetic counseling and prenatal diagnosis (PND) in the Aegean region of Turkey.

  11. Deformation microstructures and diagenesis in sandstone adjacent to an extensional fault: Implications for the flow and entrapment of hydrocarbons

    SciTech Connect

    Hippler, S.J. )

    1993-04-01

    Microstructural and diagenetic analyses of the North Scapa Sandstone in the hanging wall of the North Scapa fault, Orkney, Scotland, provide insight into the relationship between faulting and fluid flow during basin development. The results demonstrate the influence of this relationship on fault sealing processes and hydrocarbon migration. During development of the Orcadian basin in the Middle Devonian, the fault moved in an extensional sense. Dilatancy associated with cataclastic deformation caused localization of fluid flow and resulted in the precipitation of quartz and illite cement in the North Scapa Sandstone up to 1 m from the fault plane. This diagenetic event, coupled with cataclastic grain-size reduction, significantly reduced the porosity and permeability of the sandstone directly adjacent to the fault. These processes are effective sealing mechanisms within the sandstone. Lacustrine source rocks in the Orcadian basin reached maturation during the latest Devonian to middle Carboniferous. At the end of this time, the basin was uplifted, and the North Scapa fault was reactivated in a normal, but dominantly oblique-slip sense. This later deformation was accommodated directly outside the sealed zone and resulted in the development of broad (10-20 cm) breccia zones and narrow (<10 cm) cataclastic bands. Further dilatancy associated with the cataclastic deformation channelized hydrocarbon flow through the high-strain breccia zones and cataclastic bands. These observations indicate that fault activity that is broadly coincident with maturation and expulsion of hydrocarbons within a basin can directly influence the location of migration pathways. 81 refs., 14 figs., 1 tab.

  12. Brittle extension of the continental crust along a rooted system of low-angle normal faults: Colorado River extensional corridor

    NASA Technical Reports Server (NTRS)

    John, B. E.; Howard, K. A.

    1985-01-01

    A transect across the 100 km wide Colorado River extensional corridor of mid-Tertiary age shows that the upper 10 to 15 km of crystalline crust extended along an imbricate system of brittle low-angle normal faults. The faults cut gently down a section in the NE-direction of tectonic transport from a headwall breakaway in the Old Woman Mountains, California. Successively higher allochthons above a basal detachment fault are futher displaced from the headwall, some as much as tens of kilometers. Allochthonous blocks are tilted toward the headwall as evidenced by the dip of the cappoing Tertiary strata and originally horizontal Proterozoic diabase sheets. On the down-dip side of the corridor in Arizona, the faults root under the unbroken Hualapai Mountains and the Colorado Plateau. Slip on faults at all exposed levels of the crust was unidirectional. Brittle thinning above these faults affected the entire upper crust, and wholly removed it locally along the central corridor or core complex region. Isostatic uplift exposed metamorphic core complexes in the domed footwall. These data support a model that the crust in California moved out from under Arizona along an asymmetric, rooted normal-slip shear system. Ductile deformation must have accompanied mid-Tertiary crustal extension at deeper structural levels in Arizona.

  13. Extensional Flow of a Polystyrene Boger Fluid Through a 4:1:4 Axisymmetric Contraction/Expansion

    NASA Technical Reports Server (NTRS)

    Rothstein, Jonathan P.; McKinley, Gareth H.

    1999-01-01

    The creeping flow of a dilute (0.025 wt%) monodisperse polystyrene/polystyrene Boger fluid through a 4:1:4 axisymmetric contraction/expansion is experimentally observed for a wide range of Deborah numbers. Pressure drop measurements across the orifice plate show a large extra pressure drop that increases monotonically with Deborah number above the value observed for a similar Newtonian fluid at the same flow rate. This enhancement in the dimensionless pressure drop is not associated with the onset of a flow instability, yet it is not predicted by existing steady-state or transient numerical computations with simple dumbbell models. It is conjectured that this extra pressure drop is the result of an additional dissipative contribution to the polymeric stress arising from a stress-conformation hysteresis in the strong non-homogeneous extensional flow near the contraction plane. Such a hysteresis has been independently measured and computed in recent studies of homogeneous transient uniaxial stretching of PS/PS Boger fluids. Flow visualization and velocity field measurements using digital particle image velocimetry (DPIV) show large upstream growth of the corner vortex with increasing Deborah number. At large Deborah numbers, the onset of an elastic instability is observed, first locally as small amplitude fluctuations in the pressure measurements, and then globally as an azimuthal precessing of the upstream corner vortex accompanied by periodic oscillations in the pressure drop across the orifice.

  14. Comparison of quartz tuning forks and AlN-based extensional microresonators for viscosity measurements in oil/fuel mixtures

    NASA Astrophysics Data System (ADS)

    Toledo, J.; Manzaneque, T.; Hernando-García, J.; Vazquez, J.; Ababneh, A.; Seidel, H.; Lapuerta, M.; Sánchez-Rojas, J. L.

    2013-05-01

    In-situ monitoring of the physical properties of liquids is of great interest in the automotive industry. For example, lubricants are subject to dilution with diesel fuel as a consequence of late-injection processes, which are necessary for regenerating diesel particulate filters. This dilution can be determined by tracking the viscosity and the density of the lubricant. Here we report the test of two in-plane movement based resonators to explore their capability to monitor oil dilution with diesel and biodiesel. One of the resonators is the commercially available millimeter-sized quartz tuning fork, working at 32.7 kHz. The second resonator is a state-of-the-art micron-sized AlN-based rectangular plate, actuated in the first extensional mode in the MHz range. Electrical impedance measurements were carried out to characterize the performance of the structures in various liquid media in a wide range of viscosities. These measurements were completed with the development of low-cost electronic circuits to track the resonance frequency and the quality factor automatically, these two parameters allow to obtain the viscosity of various fluids under investigation, as in the case of dilution of lubricant SAE 15W40 and biodiesel.

  15. Regional geomorphology and history of Titan's Xanadu province

    USGS Publications Warehouse

    Radebaugh, J.; Lorenz, R.D.; Wall, S.D.; Kirk, R.L.; Wood, C.A.; Lunine, J.I.; Stofan, E.R.; Lopes, R M.C.; Valora, P.; Farr, T.G.; Hayes, A.; Stiles, B.; Mitri, G.; Zebker, H.; Janssen, M.; Wye, L.; LeGall, A.; Mitchell, K.L.; Paganelli, F.; West, R.D.; Schaller, E.L.; ,

    2011-01-01

    Titan's enigmatic Xanadu province has been seen in some detail with instruments from the Cassini spacecraft. The region contains some of the most rugged, mountainous terrain on Titan, with relief over 2000 m. Xanadu contains evolved and integrated river channels, impact craters, and dry basins filled with smooth, radar-dark material, perhaps sediments from past lake beds. Arcuate and aligned mountain chains give evidence of compressional tectonism, yet the overall elevation of Xanadu is puzzlingly low compared to surrounding sand seas. Lineations associated with mountain fronts and valley floors give evidence of extension that probably contributed to this regional lowering. Several locations on Xanadu's western and southern margins contain flow-like features that may be cryovolcanic in origin, perhaps ascended from lithospheric faults related to regional downdropping late in its history. Radiometry and scatterometry observations are consistent with a water–ice or water–ammonia–ice composition to its exposed, eroded, fractured bedrock; both microwave and visible to near-infrared (v-nIR) data indicate a thin overcoating of organics, likely derived from the atmosphere. We suggest Xanadu is one of the oldest terrains on Titan and that its origin and evolution have been controlled and shaped by compressional and then extensional tectonism in the icy crust and ongoing erosion by methane rainfall.

  16. Alaska: A twenty-first-century petroleum province

    USGS Publications Warehouse

    Bird, K.J.

    2001-01-01

    Alaska, the least explored of all United States regions, is estimated to contain approximately 40% of total U.S. undiscovered, technically recoverable oil and natural-gas resources, based on the most recent U.S. Department of the Interior (U.S. Geological Survey and Minerals Management Service) estimates. Northern Alaska, including the North Slope and adjacent Beaufort and Chukchi continental shelves, holds the lion's share of the total Alaskan endowment of more than 30 billion barrels (4.8 billion m3) of oil and natural-gas liquids plus nearly 200 trillion cubic feet (5.7 trillion m3) of natural gas. This geologically complex region includes prospective strata within passive-margin, rift, and foreland-basin sequences. Multiple source-rock zones have charged several regionally extensive petroleum systems. Extensional and compressional structures provide ample structural objectives. In addition, recent emphasis on stratigraphic traps has demonstrated significant resource potential in shelf and turbidite systems in Jurassic to Tertiary strata. Despite robust potential, northern Alaska remains a risky exploration frontier - a nexus of geologic complexity, harsh economic conditions, and volatile policy issues. Its role as a major petroleum province in this century will depend on continued technological innovations, not only in exploration and drilling operations, but also in development of huge, currently unmarketable natural-gas resources. Ultimately, policy decisions will determine whether exploration of arctic Alaska will proceed.

  17. Typhlonesticus gocmeni sp. n., a new cave-dwelling blind spider species from the Aegean region of Turkey (Araneae, Nesticidae)

    PubMed Central

    Ribera, Carles; Elverici, Mert; Kunt, Kadir Boğaç; Özkütük, Recep Sulhi

    2014-01-01

    Abstract A new species of the troglobitic spider genus Typhlonesticus is described from specimens found in Keloğlan Cave (Denizli Province, Dodurgalar Town), Turkey. Typhlonesticus gocmeni sp. n. is described on the basis of both sexes; and its phylogenetic relationships with closely related European genera and species are discussed based on morphological and molecular data (the cox1, rrnL and H3 genes). Three new combinations are proposed: Typhlonesticus idriacus (Roewer, 1931), comb. n., Typhlonesticus morisii (Brignoli, 1975) comb. n. and Typhlonesticus obcaecatus (Simon, 1907), comb. n. all ex Nesticus. PMID:25061362

  18. From colloidal spheres to nanofibrils: extensional flow properties of mineral pigment and mixtures with micro and nanofibrils under progressive double layer suppression.

    PubMed

    Dimic-Misic, Katarina; Hummel, Michael; Paltakari, Jouni; Sixta, Herbert; Maloney, Thad; Gane, Patrick

    2015-05-15

    Suspensions of mineral pigment and cellulose fibrillar derivatives are materials regularly found in the forest products industries, particularly in paper and board production. Many manufacturing processes, including forming and coating employ flow geometries incorporating extensional flow. Traditionally, colloidal mineral pigment suspensions have been considered to show little to no non-linear behaviour in extensional viscosity. Additionally, recently, nanofibrillar materials, such as microfibrillar (MFC) and nanofibrillar cellulose (NFC), collectively termed MNFC, have been confirmed by their failure to follow the Cox-Merz rule to behave more as particulate material rather than showing polymeric rheological properties when dispersed in water. Such suspensions and their mixtures are currently intensively investigated to enable them to generate likely enhanced composite material properties. The processes frequently involve exposure to increasing levels of ionic strength, coming either from the weak solubility of pigments, such as calcium carbonate, or retained salts arising from the feed fibre source processing. By taking the simple case of polyacrylate stabilised calcium carbonate suspension and comparing the extensional viscosity as a function of post extension capillary-induced Hencky strain on a CaBER extensional rheometer over a range of increasing salt concentration, it has been shown that the regime of constriction changes as the classic DLVO double layer is progressively suppressed. This change is seen to lead to a characteristic double (bimodal) measured viscosity response for flocculated systems. With this novel characteristic established, more complex mixed suspensions of calcium carbonate, clay and MNFC have been studied, and the effects of fibrils versus flocculation identified and where possible separated. This technique is suggested to enable a better understanding of the origin of viscoelasticity in these important emerging water-based suspensions.

  19. From colloidal spheres to nanofibrils: extensional flow properties of mineral pigment and mixtures with micro and nanofibrils under progressive double layer suppression.

    PubMed

    Dimic-Misic, Katarina; Hummel, Michael; Paltakari, Jouni; Sixta, Herbert; Maloney, Thad; Gane, Patrick

    2015-05-15

    Suspensions of mineral pigment and cellulose fibrillar derivatives are materials regularly found in the forest products industries, particularly in paper and board production. Many manufacturing processes, including forming and coating employ flow geometries incorporating extensional flow. Traditionally, colloidal mineral pigment suspensions have been considered to show little to no non-linear behaviour in extensional viscosity. Additionally, recently, nanofibrillar materials, such as microfibrillar (MFC) and nanofibrillar cellulose (NFC), collectively termed MNFC, have been confirmed by their failure to follow the Cox-Merz rule to behave more as particulate material rather than showing polymeric rheological properties when dispersed in water. Such suspensions and their mixtures are currently intensively investigated to enable them to generate likely enhanced composite material properties. The processes frequently involve exposure to increasing levels of ionic strength, coming either from the weak solubility of pigments, such as calcium carbonate, or retained salts arising from the feed fibre source processing. By taking the simple case of polyacrylate stabilised calcium carbonate suspension and comparing the extensional viscosity as a function of post extension capillary-induced Hencky strain on a CaBER extensional rheometer over a range of increasing salt concentration, it has been shown that the regime of constriction changes as the classic DLVO double layer is progressively suppressed. This change is seen to lead to a characteristic double (bimodal) measured viscosity response for flocculated systems. With this novel characteristic established, more complex mixed suspensions of calcium carbonate, clay and MNFC have been studied, and the effects of fibrils versus flocculation identified and where possible separated. This technique is suggested to enable a better understanding of the origin of viscoelasticity in these important emerging water-based suspensions

  20. Distinct magnetic fabric in weakly deformed sediments from extensional basins and fold-and-thrust structures in the Northern Apennine orogenic belt (Italy)

    NASA Astrophysics Data System (ADS)

    Caricchi, Chiara; Cifelli, Francesca; Kissel, Catherine; Sagnotti, Leonardo; Mattei, Massimo

    2016-02-01

    We report on results from anisotropy of magnetic susceptibility (AMS) analyses carried out on weakly deformed fine-grained sediments from the Northern Apennine orogenic system (Italy). We sampled 63 sites from preorogenic, synorogenic, and postorogenic sequences, which differ in age, composition, depositional environment, degrees of deformation, and tectonic regimes. The magnetic fabric is typical of weakly deformed sediments, with a magnetic foliation subparallel to the bedding plane and a magnetic lineation well defined in this plane. Northern Apennine chain deposits are characterized by strongly oblate magnetic susceptibility ellipsoids, indicating that the magnetic fabric is the result of both compaction process and tectonic load experienced by the sediments during diagenesis and orogenic events. The orientation of magnetic lineation is significantly different depending whether the studied sites underwent extensional or compressional tectonic regimes. In the Northern Apennine chain, the magnetic lineation is mostly oriented NNW-SSE, parallel to the main compressional structures. It suggests a tectonic origin of the magnetic lineation with an acquisition related to the Apennines compressional phases. In the extensional Tuscan Tyrrhenian margin, magnetic lineation is oriented ENE-WSW, almost perpendicular to the main extensional faults, which represent the main deformation elements of the area. Our results demonstrate a close relationship between the shape and orientation of magnetic fabric and the tectonic history of rocks, confirming that AMS represents a valuable tool to investigate the tectonic history of weakly deformed sedimentary rocks.

  1. Geometry of miocene extensional deformation, lower Colorado River Region, Southeastern California and Southwestern Arizona: Evidence for the presence of a regional low-angle normal fault

    NASA Technical Reports Server (NTRS)

    Tosdal, R. M.; Sherrod, D. R.

    1985-01-01

    The geometry of Miocene extensional deformation, which changes along a 120 km-long, northeast-trending transect from the southestern Chocolate Mountains, southeastern California, to the Trigo and southern Dome Rock Mountains, southwestern Arizona is discussed. Based upon regional differences in the structural response to extension and estimated extensional strain, the transet can be divided into three northwesterly-trending structural domains. From southwest to northeast, these domains are: (1) southestern Chocolate-southernmost Trigo Mountains; (2) central to northern Trigo Mountains; and (3) Trigo Peaks-southern Dome Rock Mountains. All structures formed during the deformation are brittle in style; fault rocks are composed of gouge, cohesive gouge, and local microbreccia. In each structural domain, exposed lithologic units are composed of Mesozoic crystalline rocks unconformably overlain by Oligocene to Early Miocene volcanic and minor interbedded sedimentary rocks. Breccia, conglomerate, and sandstone deposited synchronously with regional extension locally overlie the volcanic rocks. Extensional deformation largely postdated the main phase of volcanic activity, but rare rhyolitic tuff and flows interbedded with the syndeformational clastic rocks suggest that deformation began during the waning stages of valcanism. K-Ar isotopic ages indicate that deformation occurred in Miocene time, between about 22 and m.y. ago.

  2. Positive inversion of extensional footwalls in the southern Serra do Espinhaço, Brazil--insights from sandbox laboratory experiments.

    PubMed

    Gomes, Caroline J S; Martins-Neto, Marcelo A; Ribeiro, Valéria E

    2006-06-01

    Analogue experiments were carried out to get insights into the processes governing positive inversion during the foreland propagating thrust tectonics in the southern Serra do Espinhaço, a Brasiliano/Panafrican foldthrust belt in southeast Brazil. In particular, model listric half-grabens were inverted by applying contractional displacement to the footwall blocks. We investigated two different inversion conditions in listric half-grabens: (i) extensional and contractional detachments at the same level and (ii) at different positions. The models revealed that the development of a forward-breaking thrust system occurs in the basin synrift deposits, by contractional translation of the extensional footwall block when the extensional and contractional master faults do not coincide. Our experiments show the tectonic imbrication between basement and synrift sequences which characterizes the southern Serra do Espinhaço, and support the location in the eastern mountain range domain of the Espinhaço rift master fault system, which is not exposed at the surface.

  3. Time dependent structural architecture of subsidiary fracturing and stress pattern in the tip region of an extensional growth fault system, Tarquinia basin, Italy

    NASA Astrophysics Data System (ADS)

    Balsamo, F.; Storti, F.; Piovano, B.; Salvini, F.; Cifelli, F.; Lima, C.

    2008-06-01

    Fault tip regions, relay ramps and accommodation zones in between major segments of extensional fault systems provide zones of additional structural and stratigraphic complexities and also significantly affect their hydraulic behaviour. The great interest for both academic and industrial purposes encouraged specific studies of fault tip regions that, in some cases, produced controversial results. We approached the study of fault tip regions by integrating structural, AMS and stratigraphic analyses of the tip of an extensional growth fault system in the Tarquinia basin, on the Tyrrhenian side of the Northern Apennines. Detailed structural mapping indicates the occurrence of systematic relationships between the orientation of the main subsidiary fault zones, the orientation and position of the two main joint sets developed in the fault damage zones, and the overprinting relationships between the two main joint sets themselves. Microstructural analysis of fault core rocks indicates a progression of deformation from soft-sediment to brittle conditions. The AMS study supports the evolution of deformation under a constantly oriented stress field. By combining this multidisciplinary information we propose an evolutionary model for the tip of the extensional growth fault system that accounts for the progressively changing sediment rheological properties, and for the time dependent subsidiary deformation pattern by invoking the interplay between the regional stress field and the local, kinematically-derived one by fault activity. We also speculate on the overall implications for fluid flow of the proposed evolutionary model.

  4. Oblique transfer of extensional strain between basins of the middle Rio Grande rift, New Mexico: fault kinematic and paleostress constraints

    USGS Publications Warehouse

    Minor, Scott A.; Hudson, Mark R.; Caine, Jonathan Saul; Thompson, Ren A.

    2013-01-01

    The structural geometry of transfer and accommodation zones that relay strain between extensional domains in rifted crust has been addressed in many studies over the past 30 years. However, details of the kinematics of deformation and related stress changes within these zones have received relatively little attention. In this study we conduct the first-ever systematic, multi-basin fault-slip measurement campaign within the late Cenozoic Rio Grande rift of northern New Mexico to address the mechanisms and causes of extensional strain transfer associated with a broad accommodation zone. Numerous (562) kinematic measurements were collected at fault exposures within and adjacent to the NE-trending Santo Domingo Basin accommodation zone, or relay, which structurally links the N-trending, right-stepping en echelon Albuquerque and Española rift basins. The following observations are made based on these fault measurements and paleostresses computed from them. (1) Compared to the typical northerly striking normal to normal-oblique faults in the rift basins to the north and south, normal-oblique faults are broadly distributed within two merging, NE-trending zones on the northwest and southeast sides of the Santo Domingo Basin. (2) Faults in these zones have greater dispersion of rake values and fault strikes, greater dextral strike-slip components over a wide northerly strike range, and small to moderate clockwise deflections of their tips. (3) Relative-age relations among fault surfaces and slickenlines used to compute reduced stress tensors suggest that far-field, ~E-W–trending σ3 stress trajectories were perturbed 45° to 90° clockwise into NW to N trends within the Santo Domingo zones. (4) Fault-stratigraphic age relations constrain the stress perturbations to the later stages of rifting, possibly as late as 2.7–1.1 Ma. Our fault observations and previous paleomagnetic evidence of post–2.7 Ma counterclockwise vertical-axis rotations are consistent with increased

  5. Tectonomagmatic relationship between the Sierra Madre Occidental ignimbrite flare-up and the southern Basin and Range province

    NASA Astrophysics Data System (ADS)

    Aguirre-Diaz, G. J.; Labarthe-Hernandez, G.

    2004-12-01

    The Sierra Madre Occidental (SMO) is a Mid-Tertiary, large-volume, ignimbrite province at least 1,200 km long and 200-500 km wide, extending continuously from the U.S.-Mexico border (31\\deg N) to its intersection with the Mexican Volcanic Belt (21\\deg N). Considering the average thickness of 1,000 m for the ignimbrite plateau, based on several measured sections along the province, and the average wide of the province of 300 km, a conservative estimate of the physical volume of the SMO ignimbrites is about 360,000 km3. The southern part of the Basin and Range province is in Mexico. This extensional province overlaps in space and time with the SMO ignimbrite flare-up and formed NW- to NE-trending normal faults that bound many large grabens, which are particularly long and deep in the southern SMO. Basin and Range faulting occurred between at least 32 Ma and 12 Ma with both limits probably extending until the Eocene and the Quaternary. Ignimbrite activity can be as old as 51 Ma and as young as 17-16 Ma, but most of the ignimbrite volume was erupted in the 38-23 Ma period. Thus, the ignimbrite flare-up can be defined as a period of intense explosive volcanic activity that produced enormous volumes of silicic ignimbrite sheets, which took place mainly between 38 and 23 Ma in Mexico. The ignimbrite flare-up coincided in time with peaks in Basin and Range faulting, and the ignimbrite activity apparently migrated from the east-northeast to the west-southwest, i.e., from central Chihuahua (38-27 Ma) to Durango-Tayoltita-Nazas (32-29 Ma) to Zacatecas-Tepic (24-23 Ma), finishing by 16 Ma at Jalisco-Nayarit, as deduced from the compilation of geologic works done in the SMO. It is unknown yet whether there was a west-southward migration of Basin and Range faulting and if the ignimbrite flare-up occurred episodically as peaks (38-27 Ma, 32-29 Ma, and 24-23 Ma) or was continuous. Nevertheless, by the time that the ignimbrite flare-up started, the Basin and Range extension was

  6. Origin and evolution of extensional faults within the ductile-to-brittle transition, Badwater Turtleback, Death Valley, CA

    SciTech Connect

    Miller, M.G. . Geological Sciences)

    1992-01-01

    Field relations in the footwall of the Badwater Turtleback suggest a model for two geometrically distinct sets of brittle faults. The model shows how extensional brittle faults may (1) initiate within mylonite zones as a result of strain incompatibilities, and (2) become inactive as a function of decreased dip angles. Cross-cutting relations indicate that, as the footwall cooled, late stages of ductile strain concentrated in calcite marble shear zones while brittle faults formed within the other rocks. These faults fall into two groups: decollement-style faults (DSF) and high angle faults (HAF). They must have formed concurrently with calcite mylonitization because they locally terminate at the calcite shear zones. DSF are subparallel to mylonitic foliation and locally re-occupy calcite shear zones. They are moderately nonplanar, discontinuous at scales of 10--100m, and show limited evidence for transport parallel to stretching lineations in adjacent mylonites. HAF cut foliation at high angles. These faults either (1) end downwards into unfractured calcite mylonite, (2) cut calcite mylonite and join underlying DSF, or (3) cut calcite mylonite and DSF. Where they join DSF, HAF are strongly listric and maintain integrity as distinct slip surfaces within the DSF zone (see inset). DSF formed at rheological boundaries and at places where actively deforming calcite marble pinched out into brittle rocks. HAF formed in brittle upper plates of calcite marble shear zones to accommodate differences in strain between brittle and nonbrittle rock. With continued strain and consequent cooling and eastward tilting of the footwall, calcite shear zones stopped deforming ductility, became occupied by DSF, and gradually rotated to lower angles.

  7. Tuff of Bridge Spring: A mid-Miocene ash-flow tuff, northern Colorado River extensional corridor, Nevada and Arizona

    SciTech Connect

    Smith, E.I.; Morikawa, S.A.; Martin, M.W. . Dept. of Geoscience); Gonzales, D.A.; Walker, J.D. . Isotope Geochronology Lab.)

    1993-04-01

    The Tuff of Bridge Spring (TBS) (15.19[+-]0.02 Ma; Gans, 1991) is a compositionally variable dacite to rhyolite ash-flow tuff that crops out over 1800 sq. km in the northern Colorado River extensional corridor. The TBS varies in composition from 59.5 to 74 wt. % SiO[sub 2] and typically contains phenocrysts of sanidine, plagioclase, biotite, clinopyroxene, [+-] sphene, [+-] apatite, [+-] zircon, and [+-] hornblende. The TBS is thickest and displays its greatest compositional range in the center of its area of exposure. The McCullough Range section contains at least three chemically distinct flow units that vary in composition from dacite to rhyolite. The basal and uppermost units are normally zoned and the middle unit is reversely zoned. The complex chemical zonation and zoning reversals in the TBS indicate that it erupted from a magma chamber that was periodically injected by both mafic and felsic magmas. Sections at the edge of the exposure area are thin, contain only one or two chemically definable flow units and have a limited compositional range. To the west at Sheep Mountain, TBS is 2.9 m thick and ranges from 70.2--71.7 wt % SiO[sub 2]. To the east in the White Hills, TBS is 14 m thick and ranges from 59.5--65.3 wt % SiO[sub 2]. This chemical and field data indicate that although the TBS is regionally extensive, individual flow units are not. Isotopic data and chemistry suggest that all sections of the TBS are cogenetic. Comparisons of chemical, geochronological and isotopic data between the TBS and nearby coeval plutons indicate that the Aztec Wash (Eldorado Mts., Nevada) and Mt. Perkins (Black Mountain, Arizona) plutons are possible source for the TBS. Both plutons exhibit ample evidence of magma mixing and commingling, processes that may produce compositional zonation such as that observed in the TBS.

  8. Extensional tectonics during the igneous emplacement of the mafic-ultramafic rocks of the Barberton greenstone belt

    NASA Technical Reports Server (NTRS)

    Dewit, M. J.

    1986-01-01

    The simatic rocks (Onverwacht Group) of the Barberton greenstone belt are part of the Jamestown ophiolite complex. This ophiolite, together with its thick sedimentary cover occupies a complex thrust belt. Field studies have identified two types of early faults which are entirely confined to the simatic rocks and are deformed by the later thrusts and associated folds. The first type of fault (F1a) is regional and always occurs in the simatic rocks along and parallel to the lower contacts of the ophiolite-related cherts (Middle Marker and equivalent layers). These fault zones have previously been referred to both as flaser-banded gneisses and as weathering horizons. In general the zones range between 1-30m in thickness. Displacements along these zones are difficult to estimate, but may be in the order of 1-100 km. The structures indicate that the faults formed close to horizontal, during extensional shear and were therefore low angle normal faults. F1a zones overlap in age with the formation of the ophiolite complex. The second type of faults (F1b) are vertical brittle-ductile shear zones, which crosscut the complex at variable angles and cannot always be traced from plutonic to overlying extrusive (pillowed) simatic rocks. F1b zones are also apparently of penecontemporaneous origin with the intrusive-extrusive igneous processs. F1b zones may either represent transform fault-type activity or represent root zones (steepened extensions) of F1a zones. Both fault types indicate extensive deformation in the rocks of the greenstone belt prior to compressional overthrust tectonics.

  9. Extensional tectonics of a part of the southwestern White Pine Range, Nevada: Implications for petroleum occurrence in Railroad Valley

    SciTech Connect

    Langrock, H.; Taylor, W.J.

    1995-06-01

    Extension exerts controls on migration and trapping of petroleum in rift settings, such as the Great Basin. Extensional controls are critical to the accumulation of petroleum in Nevada, including in Pine and Railroad Valleys. In these fields, reservoir permeability increased due to extension-related fracturing. These fractured reservoirs and structural traps may be contained within upper plates to regional detachments. Just northeast of Nevada`s most productive oil fields, a regionally extensive detachment is exposed in the White Pine Range. This detachment, the Blackrock fault, is a presently low, angle normal fault which dips <30{degrees} along most of its surface trace. The Blackrock fault is nonplanar and exhibits drastic changes in both orientation and geometry along its length. The amount of stratigraphic separation across the fault is also highly variable ranging from <30 to {approximately}3800 m. Upper plate structures to the Blackrock fault may influence oil fields in Railroad Valley. Rocks in the hanging wall of the Blackrock fault are more intensely faulted than rocks in the footwall. The upper plate faults strike north, northwest, east, and northeast. The {approximately}east-striking faults are youngest because they typically cut the other structures. These faults are closely spaced and largely interconnected which allows migration of hydrocarbons. Most of the hanging wall faults are high-angle normal faults which cut both Paleozoic and Oligocene rocks. In the Blackrock upper plate, Paleozoic, carbonate and minor siliciclastic rocks are unconformably overlain by Oligocene tuffs and tuffaceous sedimentary rocks of the Garret Ranch Group with interbedded rhyolites. Upper plate fracturing of the Paleozoic rocks and Garret Ranch Group is important because parts of both sections are producing reservoirs in Railroad Valley.

  10. Relation between extensional geometry of the northern Grant Range and oil occurrences in railroad valley, East-Central Nevada

    SciTech Connect

    Lund, K.; Perry, W.J. Jr. ); Beard, L.S. )

    1993-06-01

    In the northern Grant Range, heterogeneous Neogene extension was dominated by synchronous arching and attenuation. Attenuation was accomplished along a stacked set of attenuation faults that formed at low angles to bedding as the Paleozoic carbonate and Paleogene rocks arched about a north-northwest axis. The style and amount of attenuation was controlled by lithologic character and structural depth of rock units and by geometry of the arch. On the steeper west side of the Grant Range arch, the curviplanar low-angle attenuation faults converge into a single shallowly west-dipping fault zone along which the stratigraphic juxtaposition of Mississippian units over Middle Cambrian units and Late Cretaceous granite marks the zone of maximum attenuation. Arching and heterogeneous extension resulted from uplift of the Grant Range relative to the structural basin of Railroad Valley to the west. This structural differentiation is a complex zone of subparallel-to-bedding, shallow-dipping attenuation faults rather than as a simple high-angle range-front fault. Seismic and drill-hole data indicate that low-angle attenuation faults in the range extend into Railroad Valley and control the structure buried in the valley. Mississippian and Paleocene to Eocene petroleum source rocks and Devonian to Oligocene reservoir rocks in Railroad Valley oil fields are in extensively fractured rocks of the upper plate to the major extensional fault system. Thus, relatively cold upper-plate rocks, immature with respect to hydrocarbon generation, were brought relatively down into contact with hotter lower-plate rocks by Neogene attenuation faulting. Oil in Railroad Valley, which is sourced from rocks as young as Eocene, was probably generated by this juxtaposition during Neogene crustal attenuation, and subsequently migrated into upper-plate fractured reservoirs. 101 refs., 10 figs.

  11. Comparison of force sensors for atomic force microscopy based on quartz tuning forks and length-extensional resonators

    NASA Astrophysics Data System (ADS)

    Giessibl, Franz J.; Pielmeier, Florian; Eguchi, Toyoaki; An, Toshu; Hasegawa, Yukio

    2011-09-01

    The force sensor is key to the performance of atomic force microscopy (AFM). Nowadays, most atomic force microscopes use micromachined force sensors made from silicon, but piezoelectric quartz sensors are being applied at an increasing rate, mainly in vacuum. These self-sensing force sensors allow a relatively easy upgrade of a scanning tunneling microscope to a combined scanning tunneling/atomic force microscope. Two fundamentally different types of quartz sensors have achieved atomic resolution: the “needle sensor,” which is based on a length-extensional resonator, and the “qPlus sensor,” which is based on a tuning fork. Here, we calculate and measure the noise characteristics of these sensors. We find four noise sources: deflection detector noise, thermal noise, oscillator noise, and thermal drift noise. We calculate the effect of these noise sources as a factor of sensor stiffness, bandwidth, and oscillation amplitude. We find that for self-sensing quartz sensors, the deflection detector noise is independent of sensor stiffness, while the remaining three noise sources increase strongly with sensor stiffness. Deflection detector noise increases with bandwidth to the power of 1.5, while thermal noise and oscillator noise are proportional to the square root of the bandwidth. Thermal drift noise, however, is inversely proportional to bandwidth. The first three noise sources are inversely proportional to amplitude while thermal drift noise is independent of the amplitude. Thus, we show that the earlier finding that quoted an optimal signal-to-noise ratio for oscillation amplitudes similar to the range of the forces is still correct when considering all four frequency noise contributions. Finally, we suggest how the signal-to-noise ratio of the sensors can be improved further, we briefly discuss the challenges of mounting tips, and we compare the noise performance of self-sensing quartz sensors and optically detected Si cantilevers.

  12. A brittle-ductile high- and low-angle fault related to the Kea extensional detachment (W Cyclades., Greece)

    NASA Astrophysics Data System (ADS)

    Rockenschaub, M.; Grasemann, B.; Iglseder, C.; Rice, A. H. N.; Schneider, D.; Zamolyi, A.

    2010-05-01

    fluid infiltration. Ar/Ar white mica data from Pisses constrain ductile deformation to ca. 20 Ma. Since the high-angle faults show a continuum from ductile to brittle deformation, the Ar/Ar cooling ages suggest that faulting must have occurred in the Miocene. Consequently the high-angle faulting was genetically related to the SSW-directed low-angle extensional event and does not represent a later overprint related to a different kinematic event.

  13. The tectonic evolution of Cenozoic extensional basins, northeast Brazil: Geochronological constraints from continental basalt 40Ar/39Ar ages

    NASA Astrophysics Data System (ADS)

    de Souza, Zorano Sérgio; Vasconcelos, Paulo Marcos; Knesel, Kurt Michael; da Silveira Dias, Luiz Gustavo; Roesner, Eduardo Henrique; Cordeiro de Farias, Paulo Roberto; de Morais Neto, João Marinho

    2013-12-01

    The Boa Vista and Cubati Basins, Paraíba, Brazil, are NW-SE extension-related intracratonic basins that resulted from tectonic stresses after the opening of the South Atlantic. These basins contain lacustrine fossiliferous sediments, bentonite beds, and basalt flows that preserve Cenozoic continental records. 40Ar/39Ar ages for six whole-rocks from two distinct basaltic flows underlying the sediments in the Boa Vista basin are 27.3 ± 0.8 and 25.4 ± 1.3 Ma, while three grains from a basaltic flow overlying the sediments yield 22.0 ± 0.2 Ma. The sediments at the nearby Cubati Basin are overlain by a basalt flow with ages of ˜25.4 Ma. Three whole-rocks from an NE-SW-trending trachytic dyke cross cutting the sediments at the Boa Vista Basin yield 40Ar/39Ar ages of ˜12.45 ± 0.06, 12.59 ± 0.07, and 12.58 ± 0.07 Ma. Three whole-rocks from a nearby volcanic plug (Chupador) yield an age of 23.4 ± 0.1 Ma. The geochronological results combined with stratigraphic correlations between the two basins allow bracketing the age of the main sedimentary and bentonic units within the Boa Vista and Cubati Basins between 25.5 ± 1.3 and 24.9 ± 0.1 Ma. The ages, combined with field observations reveal that the formation of the Boa Vista and Cubati basins is associated with mantle-derived magmas channelled through reactivated Precambrian shear zones. Our geochronological results suggest that a temporal link with the Fernando de Noronha and Saint Helena hot spots can be excluded as possible sources of the Boa Vista and Cubati magmas. Rather, the extensional tectonics in the 30-20 Ma interval, long after Gondwana break-up, may be associated with the re-activation of continental-scale shear zones that channelled small batches of mantle-derived magmas.

  14. Quaternary extensional and compressional tectonics revealed from Quaternary landforms along Kosi River valley, outer Kumaun Lesser Himalaya, Uttarakhand

    NASA Astrophysics Data System (ADS)

    Luirei, Khayingshing; Bhakuni, S. S.; Kothyari, Girish Ch.; Tripathi, Kavita; Pant, P. D.

    2016-04-01

    A portion of the Kosi River in the outer Kumaun Lesser Himalaya is characterized by wide river course situated south of the Ramgarh Thrust, where huge thickness (~200 m) of the landslide deposits and two to three levels of unpaired fan terraces are present. Brittle normal faults, suggesting extensional tectonics, are recognized in the Quaternary deposits and bedrocks as further supported by surface morphology. Trending E-W, these faults measure from 3 to 5 km in length and are traced as discontinuous linear mini-horst and fault scarps (sackungen) exposed due to cutting across by streams. Active normal faults have displaced the coarsely laminated debris fan deposits at two sites located 550 m apart. At one of the sites, the faults look like bookshelf faulting with the maximum displacement of ~2 m and rotation of the Quaternary boulders along the fault plane is observed. At another site, the maximum displacement measures about 0.60 cm. Thick mud units deposited due to blocking of the streams by landslides are observed within and above the fan deposit. Landslide debris fans and terrace landforms are widely developed; the highest level of fan is observed ~1240 m above mean sea level. At some places, the reworking of the debris fans by streams is characterized by thick laminated sand body. Along the South Almora Thrust and Ramgarh Thrust zones, the valleys are narrow and V-shaped where Quaternary deposits are sparse due to relatively rapid uplift across these thrusts. Along the South Almora Thrust zone, three to four levels of fluvial terraces are observed and have been incised by river exposing the bedrocks due to recent movement along the RT and SAT. Abandoned channel, tilted mud deposits, incised meandering, deep-cut V-shaped valleys and strath terraces indicate rapid uplift of the area. Thick mud sequences in the Quaternary columns indicate damming of streams. A ~10-km-long north-south trending transverse Garampani Fault has offset the Ramgarh Thrust producing

  15. Thermal history and extensional exhumation of a high-temperature crystalline complex (Hırkadağ Massif, Central Anatolia)

    NASA Astrophysics Data System (ADS)

    Lefebvre, Côme; Kalijn Peters, M.; Wehrens, Philip C.; Brouwer, Fraukje M.; van Roermund, Herman L. M.

    2015-12-01

    The Central Anatolian Crystalline Complex (CACC) is a large continental domain exposed in central Turkey that was affected by high temperature metamorphism during the Late Cretaceous. As a result of this event, Paleozoic sediments became metamorphosed, initially under Barrovian conditions, then overprinted locally by high temperature-low pressure metamorphism, and intruded by widespread batholiths. In this study we focus on the crystalline Hırkadağ Massif located in the central part of the CACC, where we applied an integrated approach involving metamorphic, structural and geochronological analysis in order to elucidate its tectonic history from burial to exhumation. Our metamorphic study reveals that conditions of metamorphism reached ~ 7-8 kbar/700 °C and were relatively homogeneous at the scale of the Hırkadağ Massif. Coeval with the regional metamorphism, the rocks were intensely deformed as reflected by isoclinal folding, the development of a pervasive foliation and top-to-the-SE shearing. This was followed by decompression to pressures of ~ 3-4 kbar at 800 °C, which may be linked to the emplacement of local granodioritic intrusions at ~ 77 Ma. Subsequent cooling of the Hırkadağ high-grade metamorphic and intrusive rocks is indicated by 40Ar/39Ar cooling ages of 68.8 ± 0.9 Ma (biotite) and 67.0 ± 1.2 Ma (potassium feldspar). Evidence for tectonic exhumation has been identified within the marbles at the NE margin of the Hırkadağ Massif, in the form of discrete protomylonitic and mylonitic shear bands showing a consistent N40-60 top-to-NE sense of shear. Further east, the contact between brecciated mylonitic marbles and non-metamorphic conglomerates preserves the typical structural features of an upper-crustal detachment fault. Restoration of the Hırkadağ Massif and the CACC to their late Cretaceous configuration suggests that the LP-HT metamorphism, magmatism and extensional structures evolved as a result of the development and exhumation of a ~ N

  16. Interaction between regional and local tectonic forcing along a complex Quaternary extensional basin: Upper Tiber Valley, Northern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Pucci, S.; Mirabella, F.; Pazzaglia, F.; Barchi, M. R.; Melelli, L.; Tuccimei, P.; Soligo, M.; Saccucci, L.

    2014-10-01

    In extending areas undergoing regional tectonic uplift, the persistence of subsidence at a normal-fault hanging-wall depends on the competition between regional and local tectonic effects. When regional uplift exceeds the subsidence of the hanging-wall block, denudation prevails at both the hanging-wall and the foot-wall. When local tectonic subsidence exceeds regional uplift, sedimentation occurs over the hanging-wall block, supplied by foot-wall erosion. We analyzed a Pliocene-Quaternary continental basin, currently crossed by the Tiber River in Italy. The tectono-sedimentary evolution of the basin developed at the hanging-wall of a regional low-angle extensional detachment, the Alto Tiberina Fault, in the axial region of the Northern Apennines of Italy. This area is affected by regional uplift on the order of 0.5-1.0 mm/yr. The present-day activity of the fault is revealed by both microseismicity and geodetic (GPS) data. We investigated the mid- (10-100 ka) and long-term (0.5-3.0 Ma) evolution of the three depocenters by studying the continental Pleistocene succession infilling the basin as well as fluvial terraces and higher paleosurfaces carved into the Pleistocene deposits. By using surficial geologic data and an interpretation of a set of seismic reflection profiles, we show that the three depocenters experienced a fairly similar evolution during the Pliocene-Early Pleistocene, when a 1000-m-thick continental succession was deposited. On the contrary, geomorphological observations indicate that, at the beginning of the Middle Pleistocene, a switch occurred in the evolution of the three depocenters. In the northernmost Sansepolcro sub-basin, bounding normal faults are active and hanging-wall subsidence outpaces regional uplift. Concurrently, in the Umbertide and Ponte Pattoli sub-basins uplift dominates over the hanging-wall subsidence, promoting river incision and exhumation of the Pleistocene deposits. For these two depocenters, by means of terrace

  17. The role of salt layers in the hangingwall deformation of kinked-planar extensional faults: Insights from 3D analogue models and comparison with the Parentis Basin

    NASA Astrophysics Data System (ADS)

    Ferrer, O.; Roca, E.; Vendeville, B. C.

    2014-12-01

    Using an analogue modelling approach, this work investigates the role played by salt in the hangingwall deformation of an extensional fault. Models' set-up included a wooden block simulating the footwall of different kinked-planar fault geometries flattening at depth. Above these faults, the hangingwall was modelled using only sand or sand overlain by pre- or syn-kinematic silicone putty. Regardless of the stage at which was deposited, the silicone appears as an efficient decoupling level that changes the deformation mode of the overlying sand layers. Above the silicone layers, the rollover panels only continue to develop up to the welding of the underlying silicone. Afterwards, they do not grow anymore and all shearing induced by the underlying fault bends is accommodated along the tilted silicone layer that acts as an extensional shear band. Further fault slip produces near-horizontal growth stratal geometries that can be easily misinterpreted as a syn-rift/post-rift boundary. In addition, the differential sedimentary loading of syn-kinematic layers triggers the upslope silicone flow from the hangingwall depocenters towards the rollover shoulders. This migration results in the formation of silicone welds at the rollover limbs and the growth of gentle silicone-cored anticlines above or near the rollover shoulder that are locally pierced by diapirs and walls. These experimental results fit with the Parentis Basin structure that, formed from the motion of lithosphere-scale kinked-planar extensional faults, includes salt inflated anticlines above their rollover shoulders and an intra-Albian unconformity interpreted now as syn-kinematic.

  18. On extensional waves in a poroelastic cylinder within the framework of viscosity-extended Biot theory: the case of traction-free open-pore cylindrical surface

    NASA Astrophysics Data System (ADS)

    Solorza, Selene; Sahay, Pratap N.

    2009-12-01

    For a fluid saturated porous cylinder, in which the saturating fluid is allowed to move freely across the traction-free cylindrical boundary surface, the dispersion relation for extensional deformation, established over four decades ago by Gardner within the framework of Biot's theory, yield a trivial and two non-trivial roots. One of the non-trivial roots corresponds to the coupled Biot fast-compressional and shear waves and it is the poroelastic analogue of the extensional wave of the elasticity theory. The nature of the second non-trivial root is not fully understood yet. Also there is the suggestion that the scope of applicability of Gardner's first non-trivial root might be limited. Apart from these matters, since the Biot theory is also incapable of accounting for the viscous bulk- and shear-relaxations that occur within the saturating Newtonian fluid because its fluid stress tensor is devoid of the viscous stress tensor part, therefore, we re-examined this poroelastic extensional problem with viscosity-extended Biot constitutive relations. The erstwhile trivial third root of the Biot-Gardner framework is not non-vanishing in this viscosity-extended Biot framework. In the frequency regime below the Biot relaxation frequency, the other two non-trivial roots in this framework are the same as those obtained by Gardner within the classical Biot framework. We find there is nothing dubious about the formula of Gardner's first root. The scenario in which it is not expected to hold true, in fact the Biot theory itself breaks down. We find the Gardner's second root to be essentially the Biot slow-compressional wave, the out-of-phase/differential compressional motion of the two phases. The new non-vanishing third root is akin to the slow-shear process, the out-of-phase/differential shear motion of the two phases, and a process analogue to the Biot slow-compressional wave.

  19. Chemistry of amphiboles and clinopyroxenes from Euganean (NE Italy) cumulitic enclaves: implications for the genesis of melts in an extensional setting

    NASA Astrophysics Data System (ADS)

    Bartoli, O.; Meli, S.; Sassi, R.; Magaraci, D.

    2009-04-01

    The magmatism of the Euganean Volcanic District (Veneto Volcanic Province, VVP) developed in the last phases of the Alpine orogenesis; the geochemical and geophysical data are consistent with an extensional geodynamic context (Milani et al., 1999). Cumulitic gabbroic enclaves occur within the Euganean trachytes, and Bartoli et al. (2008) pointed to their cogenetic origin with the Euganean host lavas. Sr isotopic data suggest that these cumulates derived from uncontaminated mantle-derived liquids. We analysed both cumulus and intercumulus amphiboles and clinopyroxenes by electron microprobe and LA-ICP-MS. The cumulus-intercumulus Cpx are diopsides and augites. The Mg#Cpx varies in a wide range (Mg#cumulus-Cpx= 0.74-0.84 and Mg#intercumulus-Cpx= 0.67-0.68). They show a MREE enrichment relative to LREE and HREE (LaN/SmN= 0.46-0.68 and TbN/YbN= 2.18-4.77). No significant Eu anomaly (Eu/Eu* = 0.78-1.23) was observed. On a chondrite-normalized spiderdiagram Cpx exhibits significant Pb and Co negative anomalies, and less evident negative anomalies for Sr and Zr. La, Sm and HREE increase, whereas Ba, Ti, Li and V decrease from core to rim. These Cpx exhibit high Cr contents (701-2958 ppm). Moreover, they display trace element differences when compared to Cpx from MORB gabbros. We analyzed also amphiboles: pargasites, edenites and kaersutites. In the cumulus Amph Mg# varies in the range 0.60-0.69, whereas in the intercumulus assemblage from 0.57 to 0.63. The high K2O and TiO2 contents are distinct from that of amphiboles in MORB gabbros. LREE are enriched relative to HREE (LaN/YbN = 5.07-7.56). Moreover, TbN/YbN = 2.50-4.02 indicates a HREE depletion relative to MREE. REE patterns lack a significant Eu anomaly (Eu/Eu* = 1.06-1.19). From core to rim Th and U decrease in cumulus crystals, but they increase in the intercumulus Amph. Ba (258-282 ppm) is enriched relative to other LILE and Nb-Ta are enriched relative to LREE. Cr varies in the range 423-594 ppm. The similar REE

  20. 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.

    PubMed

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

    2016-01-01

    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

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

    PubMed

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

    2014-09-15

    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

  2. Periodicities in sediment temperature time-series at a marine shallow water hydrothermal vent in Milos Island (Aegean Volcanic arc, Eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Aliani, Stefano; Meloni, Roberto; Dando, Paul R.

    2004-05-01

    Time-series data sets of total bottom pressure (tidal plus atmospheric), seawater temperature and sediment temperature from a marine shallow hydrothermal vent (Milos, Hellenic Volcanic Arc, Aegean Sea) were studied to determine factors influencing periodicity at the vents. Bottom pressure and vent temperature were mainly opposite in phase, with the main fluctuations of vent temperature occurring at tidal frequencies. Although the fluctuations in atmospheric pressure were of the same order as those due to tidal pressure, the contribution of atmospheric pressure was considerably weaker at diurnal frequencies. Some sudden discontinuities in sediment temperature were recorded, at least one of these may have been caused by seismic events. Seawater temperature changes were not reflected in the sediment temperature record. Transient loadings, such as tidal loadings, barometric pressure and earth tides, may affect the pore pressure in sediments, influencing fluid expulsion and sediment temperature as a consequence. Most of the contribution to the fluctuations in sediment temperature depends on tidal loadings. Gravitational forces, in the form of earth tides, can also be involved and barometric pressure is probably responsible for long period temperature oscillations.

  3. Marine pollution risk in a coastal city: use of an eco-genotoxic tool as a stress indicator in mussels from the Eastern Aegean Sea.

    PubMed

    Kacar, Asli; Pazi, Idil; Gonul, Tolga; Kucuksezgin, Filiz

    2016-08-01

    Coastal areas, such as bays, estuaries, and harbors, are heavily polluted since these areas are the settlements to which toxic chemicals from industrial and domestic wastes are discharged. The genetic damage was evaluated using bioindicator mussel Mytilus galloprovincialis caused by toxic chemicals (metals and polycyclic aromatic hydrocarbons) in İzmir and Çandarlı Bays (the Eastern Aegean Sea) through comet assay. Three sampling sites from the two bays were selected and the study was conducted during the spring and autumn periods. The highest levels of DNA damage expressed as %Tail-DNA were observed in İzmir Bay (34.60 % Tail-DNA) in the spring. Analysis of the correlation between PAHs and metals in mussels and %T-DNA in the hemolymph and gill cells showed a statistically significant positive correlation between %T-DNA and ∑PAH, chromium (p < 0.05). This study determined the pollution level of the İzmir and Çandarlı Bays by using the DNA damage to the mussel, which can identify the effects of environmental pollutants at the cellular levels. These results confirm that comet assay can be used to determine the temporal and spatial differences of DNA damage, and as a suitable tool for the measurement of genotoxicity in regions with low pollutant concentrations. PMID:27146544

  4. Implementation of a reduced order Kalman filter to assimilate ocean color data into a coupled physical-biochemical model of the North Aegean Sea.

    NASA Astrophysics Data System (ADS)

    Kalaroni, Sofia; Tsiaras, Kostas; Economou-Amilli, Athena; Petihakis, George; Politikos, Dimitrios; Triantafyllou, George

    2013-04-01

    Within the framework of the European project OPEC (Operational Ecology), a data assimilation system was implemented to describe chlorophyll-a concentrations of the North Aegean, as well the impact on the European anchovy (Engraulis encrasicolus) biomass distribution provided by a bioenergetics model, related to the density of three low trophic level functional groups of zooplankton (heterotrophic flagellates, microzooplankton and mesozooplankton). The three-dimensional hydrodynamic-biogeochemical model comprises two on-line coupled sub-models: the Princeton Ocean Model (POM) and the European Regional Seas Ecosystem Model (ERSEM). The assimilation scheme is based on the Singular Evolutive Extended Kalman (SEEK) filter and its variant that uses a fixed correction base (SFEK). For the initialization, SEEK filter uses a reduced order error covariance matrix provided by the dominant Empirical Orthogonal Functions (EOF) of model. The assimilation experiments were performed for year 2003 using SeaWiFS chlorophyll-a data during which the physical model uses the atmospheric forcing obtained from the regional climate model HIRHAM5. The assimilation system is validated by assessing the relevance of the system in fitting the data, the impact of the assimilation on non-observed biochemical parameters and the overall quality of the forecasts.

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

    PubMed

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

    2014-09-15

    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.

  6. Marine pollution risk in a coastal city: use of an eco-genotoxic tool as a stress indicator in mussels from the Eastern Aegean Sea.

    PubMed

    Kacar, Asli; Pazi, Idil; Gonul, Tolga; Kucuksezgin, Filiz

    2016-08-01

    Coastal areas, such as bays, estuaries, and harbors, are heavily polluted since these areas are the settlements to which toxic chemicals from industrial and domestic wastes are discharged. The genetic damage was evaluated using bioindicator mussel Mytilus galloprovincialis caused by toxic chemicals (metals and polycyclic aromatic hydrocarbons) in İzmir and Çandarlı Bays (the Eastern Aegean Sea) through comet assay. Three sampling sites from the two bays were selected and the study was conducted during the spring and autumn periods. The highest levels of DNA damage expressed as %Tail-DNA were observed in İzmir Bay (34.60 % Tail-DNA) in the spring. Analysis of the correlation between PAHs and metals in mussels and %T-DNA in the hemolymph and gill cells showed a statistically significant positive correlation between %T-DNA and ∑PAH, chromium (p < 0.05). This study determined the pollution level of the İzmir and Çandarlı Bays by using the DNA damage to the mussel, which can identify the effects of environmental pollutants at the cellular levels. These results confirm that comet assay can be used to determine the temporal and spatial differences of DNA damage, and as a suitable tool for the measurement of genotoxicity in regions with low pollutant concentrations.

  7. Heat flow in the Basin and Range province and thermal effects of tectonic extension

    USGS Publications Warehouse

    Lachenbruch, A.H.

    1978-01-01

    In regions of tectonic extension, vertical convective transport of heat in the lithosphere is inevitable. The resulting departure of lithosphere temperature and thickness from conduction-model estimates depends upon the mechanical mode of extension and upon how rapidly extension is (and has been) taking place. Present knowledge of these processes is insufficient to provide adequate constraints on thermal models. The high and variable regional heat flow and the intense local heat discharge at volcanic centers in the Basin and Range province of the United States could be accounted for by regional and local variations in extensional strain rate without invoking anomalous conductive heat flow from the asthenosphere. Anomalous surface heat flow typical of the province could be generated by distributed extension at average rates of about 1/2 to 1%/m.y., similar to rates estimated from structural evidence. To account for higher heat flow in subregions like the Battle mountain High, these rates would be increased by a factor of about 3, and locally at active bimodal volcanic centers, by an order of magnitude more. ?? 1978 Birkha??user Verlag.

  8. Fault zone development and strain partitioning in an extensional strike-slip duplex: A case study from the Mesozoic Atacama fault system, Northern Chile

    NASA Astrophysics Data System (ADS)

    Cembrano, J.; González, G.; Arancibia, G.; Ahumada, I.; Olivares, V.; Herrera, V.

    2005-05-01

    Upper crustal strike-slip duplexes provide an excellent opportunity to address the fundamental question of fault zone development and strain partitioning in an evolving system. Detailed field mapping of the Mesozoic Atacama fault system in the Coastal Cordillera of Northern Chile documents the progressive development of second- and third-order faults forming a duplex at a dilational jog between two overstepping master faults: the sinistral strike-slip, NNW-striking, Jorgillo and Bolfin faults. These are constituted by a meter-wide core of foliated S-C ultracataclasite and cataclasite, flanked by a damage zone of protocataclasite, splay faults and veins. Lateral separation of markers along master faults is on the order of a few kilometers. Second-order, NW-striking, oblique-slip subsidiary fault zones do not show foliated ultracataclasite; lateral sinistral separations are in the range of ˜ 10 to 200 m with a relatively minor normal dip-slip component. In turn, third-order, east-west striking normal faults exhibit centimetric displacement. Oblique-slip (sinistral-normal) fault zones located at the southern termination of the Bolfin fault form a well-developed imbricate fan structure. They exhibit a relatively simple architecture of extensional and extensional-shear fractures bound by low displacement shear fractures. Kinematic analysis of fault slip data from mesoscopic faults within the duplex area, document that the NW-striking and the EW-striking faults accommodate transtension and extension, respectively. Examination of master and subsidiary faults of the duplex indicates a strong correlation between total displacement and internal fault structure. Faults started from arrays of en echelon extensional/extensional-shear fractures that then coalesced into throughgoing strike-slip faults. Further displacement leads to the formation of discrete bands of cataclasite and ultracataclasite that take up a significant part of the total displacement. We interpret that the

  9. April 7, 2009, Mw 5.5 aftershock of the L'Aquila earthquake: seismogenic fault geometry and its implication for the central Apennines active extensional tectonics (Italy).

    NASA Astrophysics Data System (ADS)

    Adinolfi, Guido Maria; Lavecchia, Giusy; De Matteis, Raffaella; Nardis Rita, De; Francesco, Brozzetti; Federica, Ferrarini; Zollo, Aldo

    2015-04-01

    On April 6, 2009 (at 01:32 UTC) a Mw 6.3 earthquake hit the town of L'Aquila (central Italy) and surrounding villages causing fatalities and severe damage in the area. After few days, a nearly 40-km-long extensional fault system was activated generating both northward and southward seismicity migration along the NW-SE trending sector of central Apennines. During the intense aftershocks sequence, different sesmogenic sources with a distinct geometry, size and the degree of involvement were reactivated. Among the relevant aftershocks with Mw 5.0 to 5.5, the largest one occurred on April 7 (at 17:47 UTC), 9 km SE-ward of the mainshock involving a source seated at much greater depths (~14 km). Despite the enormous number of studies of the 2009 L'Aquila earthquake, mainly focused on the various geological and seismological aspects of the main Paganica source, the April 7 strongest aftershock (Mw 5.5) has not yet been deeply investigated. Consistent geometric and kinematic correlations between the geological and seismological data about this seismogenic source are missing. There are still open questions concerning its unresolved geometry and the unknown style of the central Apennines structure activated at greater depths during the 2009 L'Aquila seismic sequence. Furthermore, some authors (Lavecchia et al., 2012) have supposed that the April 7, 2009 aftershock (Mw 5.5) occurred onto an high dip segment (~50°) of an east-dipping extensional basal detachment with a potential surface expression outcropping in the area of the eastern Sabina-Simbruini Mts. In this work we propose a seismological analysis of the April 7, 2009 aftershock (Mw 5.5) rupture process. In order to define the unresolved source geometry, we computed the focal mechanism through the time domain, moment tensor full waveform inversion (Dreger and Helmberger, 1993). Also, we estimated the apparent source time functions (ASTFs) by deconvolution of the impulse response of the medium from the recorded data

  10. Entrepreneur achievement. Liaoning province.

    PubMed

    Zhao, R

    1994-03-01

    This paper reports the successful entrepreneurial endeavors of members of a 20-person women's group in Liaoning Province, China. Jing Yuhong, a member of the Family Planning Association at Shileizi Village, Dalian City, provided the basis for their achievements by first building an entertainment/study room in her home to encourage married women to learn family planning. Once stocked with books, magazines, pamphlets, and other materials on family planning and agricultural technology, dozens of married women in the neighborhood flocked voluntarily to the room. Yuhong also set out to give these women a way to earn their own income as a means of helping then gain greater equality with their husbands and exert greater control over their personal reproductive and social lives. She gave a section of her farming land to the women's group, loaned approximately US$5200 to group members to help them generate income from small business initiatives, built a livestock shed in her garden for the group to raise marmots, and erected an awning behind her house under which mushrooms could be grown. The investment yielded $12,000 in the first year, allowing each woman to keep more than $520 in dividends. Members then soon began going to fairs in the capital and other places to learn about the outside world, and have successfully ventured out on their own to generate individual incomes. Ten out of twenty women engaged in these income-generating activities asked for and got the one-child certificate.

  11. The mantle sources beneath the Afar volcanic province and their interplay with extension

    NASA Astrophysics Data System (ADS)

    Pik, Raphael; Stab, Martin; Ancellin, Marie-Anne; Medynski, Sarah; Cloquet, Christophe; Ayalew, Dereje; Yirgu, Gezahegn; Chazot, Gilles; Vye-Brown, Charlotte; Bellahsen, Nicolas; Leroy, Sylvie

    2015-04-01

    The evolution of mantle sources beneath the Ethiopian volcanic province has long been discussed and debated with a long-lived controversy in identifying mantle reservoirs and locating them in the mantle. One interpretation of the isotopic composition of erupted lavas considers that the Afar mantle plume composition is best expressed by recent lavas from Afar and Gulf of Aden (e.g. Erta Ale, Manda Inakir and the 45°E torus anomaly on the Gulf of Aden) implying that all other volcanics (including other active segments and the initial flood basalt province) result from mixing of this plume component with additional lithospheric and asthenospheric components. A completely opposite view considers that the initial Oligocene continental flood basalts best represent the isotopic composition of the Afar mantle plume, which is subsequently mixed in various proportions with continental lithospheric mantle for generating some of the specific signature of Miocene and Quaternary volcanics. The precise and correct identification of mantle components involved in the generation of magmas is of particular importance because this is the only way to document the participation of mantle during extension and its potential role in break-up processes. In this contribution we provide new isotopic data for central Afar and we revisit the whole data set of the Ethiopian volcanic province and African/Arabian intraplate volcanics in order to: (i) precisely identify the distinct mantle components implicated, (ii) discuss their location and evolution in space and time, and (3) link the evolution of mantle with extensional processes beneath the Afar province. This new interpretation of geochemical data allows reconsidering the evolution of mantle in the course of rift evolution. In terms of mantle sources, two populations of active segments are frontally opposed in the volcanic province: those that share exactly the same composition with plume related CFBs (e.g. the Manda Hararo and the Main

  12. Constraints on the pre-extensional paleoelevation of the central Basin and Range from carbonate clumped-isotope paleothermometry

    NASA Astrophysics Data System (ADS)

    Niemi, N. A.; Lechler, A. R.; Hren, M. T.; Lohmann, K. C.

    2011-12-01

    Large-magnitude Cenozoic extension across the Basin and Range has been constrained on the basis of a wide variety of geological and geophysical studies. Despite this regional extension, and associated crustal thinning, the Basin and Range maintains high (>1 km) regional elevations, and a fairly uniform, and typical thickness, continental crust. A number of geodynamic models have been proposed to explain these apparent contradictions, and a potentially useful discriminant between these models are the different predictions each makes for the paleoelevation history of the Basin and Range. We present new carbonate clumped-isotope paleothermometry data that bears on this paleoelevation history. Clumped isotope paleothermometry from lacustrine micrites in two Paleocene sections provides constraints on the paleoelevation of east-central Nevada prior to large-magnitude regional extension and core complex formation in Eocene time. The Goler Formation, which outcrops in the El Paso Mountains, east of the Sierra Nevada, has a known paleoelevation at or near sea-level and yields paleotemperatures on the order of 40°C (Universal Reference Frame (URF) Δ47 = 0.63-0.65). Lacustrine micrites from the age-equivalent Sheep Pass Formation in the Egan Range, Nevada, yield paleotemperatures of ~23-26°C (Δ47 = 0.69-0.71). Using a typical range of terrestrial lapse rates, the temperature difference between these two sites is indicative of a paleoelevation for the Sheep Pass Formation of 2500-3000 m, or perhaps as much as 1000 m higher than the elevation of present-day exposure. In the central Basin and Range, where large-magnitude upper crustal extension is generally well-constrained to have occurred later than 15 Ma, paleotemperatures of two pre-extensional (16-20 Ma) lacustrine micrites in the Death Valley region are ~25-28°C (Δ47 = 0.69-0.70). Lacustrine micrites within the Bena gravel (~17 Ma), exposed in the western Sierra Nevada, and deposited at sea-level on the paleo

  13. The Tertiary structural and thermal evolution of the Central Alps—compressional and extensional structures in an orogenic belt

    NASA Astrophysics Data System (ADS)

    Steck, Albrecht; Hunziker, Johannes

    1994-11-01

    The Western Alpine Arc has been created during the Cretaceous and the Tertiary orogenies. The interference patterns of the Tertiary structures suggest their formation during continental collision of the European and the Adriatic Plates, with an accompanying anticlockwise rotation of the Adriatic indenter. Extensional structures are mainly related to ductile deformation by simple shear. These structures developed at a deep tectonic level, in granitic crustal rocks, at depths in excess of 10 km. In the early Palaeogene period of the Tertiary Orogeny, the main Tertiary nappe emplacement resulted from a NW-thrusting of the Austroalpine, Penninic and Helvetic nappes. Heating of the deep zone of the Upper Cretaceous and Tertiary nappe stack by geothermal heat flow is responsible for the Tertiary regional metamorphism, reaching amphibolite-facies conditions in the Lepontine Gneiss Dome (geothermal gradient 25°C/km). The Tertiary thrusting occurred mainly during prograde metamorphic conditions with creation of a penetrative NW-SE-oriented stretching lineation, X I(finite extension), parallel to the direction of simple shear. Earliest cooling after the culmination of the Tertiary metamorphism, some 38 Ma ago, is recorded by the cooling curves of the Monte Rosa and Mischabel nappes to the west and the Suretta Nappe to the east of the Lepontine Gneiss Dome. The onset of dextral transpression, with a strong extension parallel to the mountain belt, and the oldest S-vergent "backfolding" took place some 35 to 30 Ma ago during retrograde amphibolite-facies conditions and before the intrusion of the Oligocene dikes north of the Periadriatic Line. The main updoming of the Lepontine Gneiss Dome started some 32-30 Ma ago with the intrusion of the Bergell tonalités and granodiorites, concomitant with S-vergent backfolding and backthrusting and dextral strike-slip movements along the Tonale and Canavese Lines (Argand's Insubric phase). Subsequently, the center of main updoming

  14. Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana

    USGS Publications Warehouse

    Ruleman, Chester A.; Larsen, Mort; Stickney, Michael C.

    2014-01-01

    The catastrophic Hebgen Lake earthquake of 18 August 1959 (MW 7.3) led many geoscientists to develop new methods to better understand active tectonics in extensional tectonic regimes that address seismic hazards. The Madison Range fault system and adjacent Hebgen Lake–Red Canyon fault system provide an intermountain active tectonic analog for regional analyses of extensional crustal deformation. The Madison Range fault system comprises fault zones (~100 km in length) that have multiple salients and embayments marked by preexisting structures exposed in the footwall. Quaternary tectonic activity rates differ along the length of the fault system, with less displacement to the north. Within the Hebgen Lake basin, the 1959 earthquake is the latest slip event in the Hebgen Lake–Red Canyon fault system and southern Madison Range fault system. Geomorphic and paleoseismic investigations indicate previous faulting events on both fault systems. Surficial geologic mapping and historic seismicity support a coseismic structural linkage between the Madison Range and Hebgen Lake–Red Canyon fault systems. On this trip, we will look at Quaternary surface ruptures that characterize prehistoric earthquake magnitudes. The one-day field trip begins and ends in Bozeman, and includes an overview of the active tectonics within the Madison Valley and Hebgen Lake basin, southwestern Montana. We will also review geologic evidence, which includes new geologic maps and geomorphic analyses that demonstrate preexisting structural controls on surface rupture patterns along the Madison Range and Hebgen Lake–Red Canyon fault systems.

  15. TR method (TRM): A separation and stress inversion method for heterogeneous fault-slip data driven by Andersonian extensional and compressional stress regimes

    NASA Astrophysics Data System (ADS)

    Tranos, Markos D.

    2015-10-01

    The recently proposed TR method (TRM) which uses the slip preference of the faults to separate heterogeneous fault-slip data in extensional and compressional Andersonian stress regimes, is enhanced so as to determine stress tensors with the use of the Wallace-Bott slip criterion. Published natural fault-slip data from the extensional region of Tympaki, Crete, Greece and artificial fault-slip data modeled from the Chelungpu thrust, activated during the 1999 Chi-Chi earthquake in Taiwan, have been used as case studies. In the first case, the fault-slip data previously considered as homogeneous might actually be of heterogeneous origin as they determine two distinct stress tensors that both fit well with the neotectonic faulting deformation of the region. In the second case, where the fault-slip data belonging to three different subsets are of low diversity, the TRM succeeds in defining the driving stress tensors. The Misfit Angle minimization criterion can adequately separate the fault-slip data between two subsets when the percentage of the "Stress Tensor Discriminator Faults" is higher than approximately 70%.

  16. The role of small-scale extensional faulting in the evolution of basin geometries. An example from the late Palaeozoic Petrel Sub-basin, northwest Australia

    NASA Astrophysics Data System (ADS)

    Baxter, K.

    1998-03-01

    During continental extension, the kinematic collapse of the hangingwall of major normal faults and the subsequent isostatic response imposes a strong control on the evolving basin geometry. The interaction of the flexural wavelength. and the magnitude and location of faults may allow the development of basin geometries which deviate from a classic half-graben style, particularly if some of this deformation is below the scale of observation (commonly seismic reflection data). In particular the development of a lateral partitioning between large- and small-scale faults within a basin may exert a significant control on the resulting basin geometry. Using the Petrel Sub-basin in northwest Australia as an example, it is demonstrated that an extensional basin geometry consisting of a classic half-graben can be overprinted by a significant 'sag' geometry which can be related to the lateral offset of sub-resolution faulting. This lateral partitioning and resulting basin geometry may also have an application to other extensional basins, particularly if a mechanism is present to allow this partitioning of fault styles to develop. In the Petrel Sub-basin this has been related to the presence of older basement features of the Halls Creek Mobile Zone beneath the axis of the basin. However, a comparison with physical models also suggests that this may be applicable to basins formed by oblique rifting (a component of which may also be present within the Petrel Sub-basin), particularly if this is imposed upon a weak zone or suture within the upper mantle.

  17. Analysis of coupled fast-shear and extensional vibrations of a LiTaO3 crystal plate with a ferroelectric inversion layer.

    PubMed

    Ma, Tingfeng; Pei, Jieyu; Wang, Ji; Du, Jianke; Zhang, Chao; Huang, Bin; Yuan, Lili; Yu, Fapeng

    2016-05-01

    The resonance vibrations of LiTaO3 fast-shear overtone mode resonators with a ferroelectric inversion layer are analyzed. In addition to the fast-shear mode, the coupled extensional mode is considered. Different from most of the LiTaO3 resonators studied in the literature that are based on the slow-shear mode, the resonator in this paper operates with the fast-shear overtone mode. Results show that the capacitance ratio assumes maxima at two resonances, which are identified to be the second overtone modes of fast-shear and extension, respectively. It is found that the thickness of the inversion layer has obvious influences on the capacitance ratio of fast-shear and extensional modes. This condition may provide a simple method to adjust capacitance ratios of piezoelectric resonators. The influence mechanisms are also discussed. Besides, the effect of the cut angle of the crystal on the mode shape of vibrations is also investigated. The results can be used as important basis of parameters designs of LiTaO3 resonators operating on the fast-shear overtone mode. PMID:27250157

  18. Anisotropy of Magnetic Susceptibility (AMS) of the Neogene Volcanic Succession at the Sierra Juarez - Las PintasVolcanic Province, Northeastern Baja California, Mexico: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Mendoza-Borunda, R.; Cañón-Tapia, E.; Suárez-Vidal, F.; Gradilla-Martínez, L.

    2010-12-01

    The Sierra Juarez-Las Pintas Volcanic Province is among the largest in northern Baja California. For this work, we focused on a bimodal volcanic succession of late Miocene age, composed of an extensive ignimbrite unit and few dispersed basaltic flows that crop out in central Sierra Juarez and northern Sierra Las Tinajas. The ignimbrite is zoned, composed by three distinctive members: a basal unwelded white tuff, a mid-section unwelded orange tuff, and an upper red welded tuff. The basaltic flows are olivine-rich. Samples were collected in five sites that define a NE-SW section across the Sierra Juarez Escarpment, in the western boundary of the so-called Gulf Extensional Province. In each of these sites a stratigraphic column composed of more than one geologic unit was sampled. The total number of analyzed cores is ca. 160. The preliminary results show vertical and lateral variations of the AMS of the ignimbrite that can be interpreted in terms of the local flow direction and processes of emplacement of these volcanic deposits. Such variations, in turn, are likely to reflect variations in the dynamics of the eruptive process that produced them. Although the AMS of all the rocks in this province display a complex set of orientations, in this work is shown that when examined in detail important clues concerning the geological evolution of the province can be obtained from these data.

  19. Time-Domain Moment Tensors for shallow ( h ≤ 40 km) earthquakes in the broader Aegean Sea for the years 2006 and 2007: The database of the Aristotle University of Thessaloniki

    NASA Astrophysics Data System (ADS)

    Roumelioti, Zafeiria; Kiratzi, Anastasia; Benetatos, Christoforos

    2011-03-01

    We present a catalog of moment tensor (MT) solutions and moment magnitudes, Mw, for 119 shallow ( h ≤ 40 km) earthquakes in Greece and its surrounding lands (34°N-42°N, 19°E-30°E) for the years 2006 and 2007, computed with the 1D Time-Domain Moment Tensor inversion method (TDMT_INV code of Dreger, 2003). Magnitudes range from 3.2 ≤ Mw ≤ 5.7. Green's functions (GF) have been pre-computed to build a library, for a number of velocity profiles applicable to the broader Aegean Sea region, to be used in the inversion of observed broad band waveforms (10-50 s). All MT solutions are the outcome of a long series of tests of different reported source locations and hypocenter depths. Quality factors have been assigned to each MT solution based on the number of stations used in the inversion and the goodness of fit between observed and synthetic waveforms. In general, the focal mechanisms are compatible with previous knowledge on the seismotectonics of the Aegean area. The new data provide evidence for strike-slip faulting along NW-SE trending structures at the lower part of Axios basin, close to the heavily industrialized, and presently subsiding, region of the city of Thessaloniki. Normal faulting along E-W trending planes is observed at the Strimon basin, and in Orfanou Gulf in northern Greece. A sequence of events in the east Aegean Sea close to the coastline with western Anatolia sheds light on an active structure bounding the north coastline of Psara-Chios Islands about 20-25 km in length exhibiting right lateral strike-slip faulting.

  20. Tracing organic and inorganic pollution sources of agricultural crops and water resources in Güzelhisar Basin of the Aegean Region - Turkey

    NASA Astrophysics Data System (ADS)

    Czarnecki, Sezin; Colak Esetlili, Bihter; Esetlili, Tolga; Tepecik, Mahmut; Anac, Dilek; Düring, Rolf-Alexander

    2014-05-01

    The study area Güzelhisar Basin is 6 km far from the city Aliaga, Aegean Region in Turkey which represents a rather industrialized area having five large iron and steel factories, but also areas of agriculture. Steel industry in Aliaga is causing metal pollution. Around Güzelhisar Basin and nearby, the dominant crop fields are cotton, maize, vegetables, olive trees and vineyards. Güzelhisar stream and dam water is used for irrigation of the agricultural land. Due to contamination from metal industry in Aliaga, organic farming is not allowed in this region. Industrial activities in the region present a threat on sustainable agriculture. The region is a multi-impacted area in terms of several pollutant sources affecting soil and water quality. The overall objective of the project is to trace back plant nutrients (N, P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, and B), hazardous substances (i. e. persistent organic pollutants), radionuclides (40K, 232Th, 226Ra/238U), and metal contents (As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, and Zn) by examining the soils, agricultural crops and natural plants from Güzelhisar Basin and water and sediments from Güzelhisar stream and dam. Spatial distribution of pollution will be evaluated by regionalization methods. For this, an advanced analytical methodology will be applied which provides an understanding of sources and occurrence of the respective substances of concern. An innovative multi-tracer approach comprising organic and inorganic marker substances, will identify and quantitatively assess sources and their impact on water pollution and the pollutant pathways in this agricultural crop production system.

  1. Hydrodynamic features of the South Aegean Sea as derived from Argo T/S and dissolved oxygen profiles in the area

    NASA Astrophysics Data System (ADS)

    Kassis, Dimitris; Krasakopoulou, Evangelia; Korres, Gerasimos; Petihakis, George; Triantafyllou, George S.

    2016-09-01

    In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013-July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.

  2. Palaeomagnetic Results From Minoan Ash Deposits (Rv Vema) Cores V10-50 And V10-58 South Aegean Sea: A Comparison With Santorini Minoan Pumice Deposits.

    NASA Astrophysics Data System (ADS)

    Downey, W. S.

    Palaeomagnetic and anisotropy measurements were carried out on Minoan ash deposits ob-tained from the deep-sea cores, (V10-50 and V10-58), South Aegean Sea. Three distinct layers have been reported within the ash deposit in core (V10-50). Based primarily on grain-size differences, a link to three separate eruptive phases of Santorini has been suggested. Magnetic results were una-ble to resolve any differences between these layers which suggests that the eruption may have been a 'single event'. Some magnetic parameters indicate that the final ignimbrite phase of the eruption of Santorini is most likely to have been responsible for the bulk of the deep-sea ash deposits, alt-hough a contribution from the first phase (phreatomagmatic and/or Plinian air-fall) cannot be ex-cluded. Anisotropy of magnetic susceptibility measurements indicate a primary sedimentary fabric and quiet depositional conditions for V10-50 ash sediment. A more disturbed petrofabric is ob-served for V10-58 suggesting, bottom current activity and/or slumping. The mean palaeomagnetic inclination calculated from appropriate V10-50 results is:- 60.2° ± 4.3° (corrected for anisotropy and geographical location differences of sites). This is statistically identical to values obtained for burnt mud brick from destruction sites in eastern Crete but different to the mean palaeomagnetic inclina-tion obtained for central Cretan sites. A comparison with the secular variation (inclination) data for the Balkan region and for Greece, suggests that the eruption/s of Santorini occurred in the period between ~1540 and 1500 BC.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  4. Kimmeridgian Shales Total Petroleum System of the North Sea Graben Province

    USGS Publications Warehouse

    Gautier, Donald L.

    2005-01-01

    The North Sea Graben of northwestern Europe, World Energy Project Province 4025, is entirely offshore within the territorial waters of Denmark, Germany, the Netherlands, Norway, and the United Kingdom. Extensional tectonics and failed rifting are fundamental to the distribution of oil and gas in the province. Accordingly, the geologic history and reser-voir rocks of the province are considered in the context of their temporal relationship to the principal extension and rifting events. The oil and gas accumulations of the province are considered part of a single petroleum system: the Kimmeridg-ian Shales Total Petroleum System (TPS). Source rocks of the Kimmeridgian Shales TPS were deposited in Late Jurassic to earliest Cretaceous time during the period of intensive exten-sion and rifting. The Kimmeridgian Shales contain typical 'type II' mixed kerogen. Oil and gas generation began locally in the North Sea Graben Province by Cretaceous time and has continued in various places ever since. Reservoirs are found in strata with ages ranging from Devonian to Eocene. Pre-rift reservoirs are found in fault-block structures activated during rifting and can be of any age prior to the Late Jurassic. Syn-rift reservoirs are restricted to strata actually deposited during maximum extension and include rocks of Late Jurassic to earliest Cretaceous age. Post-rift reservoirs formed after rifting and range in age from Early Cretaceous to Eocene. Seals are diverse, depending upon the structural setting and reservoir age. Pre-rift reservoirs com-monly have seals formed by fine-grained, post-rift sedimentary sequences that drape the Late Jurassic to earliest Cretaceous structures. Contemporaneous shales such as the Kimmeridge Clay seal many syn-rift reservoirs. Fields with post-rift res-ervoirs generally require seals in fine-grained Tertiary rocks. In most of the North Sea Graben, source rocks have been continuously buried since deposition. Structural trap forma-tion has also taken

  5. Late Cenozoic evolution of epithermal gold metallogenic provinces in Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Watanabe, Yasushi

    2005-11-01

    Kyushu Island, Japan, is located at the junction of the Southwest Japan arc and the Ryukyu arc. There are two major late Cenozoic epithermal gold-silver provinces in Kyushu, which are termed the Northern and Southern provinces. The provinces are characterized by: 1) Pliocene volcanism dominated by calc-alkaline andesite, followed by Quaternary volcanism including extrusion of both calc-alkaline and tholeiitic magmas; 2) formation of extensional grabens; 3) Pliocene to Pleistocene mineralization, which was dominated by abundant low sulfidation (LS) epithermal deposits with a few high sulfidation (HS) examples. The two epithermal gold-silver provinces have evolved differently since about 5 Ma; the Northern province has exhibited diminished hydrothermal activity from the Pliocene to Pleistocene, whereas the Southern province has witnessed increased hydrothermal activity mainly in easterly and northerly directions. Changes of tectonic setting from the Pliocene to Pleistocene account for the variable trends in epithermal gold deposit formation. Westward oblique subduction of the Philippine Sea plate beneath the Southwest Japan arc caused development of the Hohi graben and arc-related volcanism at about 6 Ma. This was associated with widespread LS mineralization in and surrounding the Hohi graben, as is represented by the Bajo and Taio deposits. The subduction of the relatively buoyant Kyushu-Palau ridge during the early Pliocene strengthened the coupling between the slab and overriding Ryukyu arc, leading to polygenetic andesite volcanism with associated HS (Kasuga, Iwato, and Akeshi) and LS (Kushikino) mineral deposits forming in the Southern province. A change of the subduction direction of the Philippine Sea plate, from west to north-northwest in the early Pliocene, increased the orthogonal convergence rate between the Southwest Japan arc and the Philippine Sea plate, resulting in a decrease of volcanic and hydrothermal activity in the Hohi graben of the Northern

  6. A Lower Carboniferous two-stage extensional basin along the Avalon-Meguma terrane boundary: Evidence from southeastern Isle Madame, Nova Scotia

    USGS Publications Warehouse

    Force, E.R.; Barr, S.M.

    2006-01-01

    Anomalously thick and coarse clastic sedimentary successions, including over 5000 m of conglomerate, are exposed on Isle Madame off the southern coast of Cape Breton Island. Two steeply to moderately dipping stratigraphic packages are recognized: one involving Horton and lower Windsor groups (Tournasian-Visean); the other involving upper Windsor and Mabou (Visean-Namurian) groups. Also anomalous on Isle Madame are three long narrow belts of "basement" rocks, together with voluminous chloritic microbreccia and minor semi-ductile mylonite, which are separated from the conglomerate-dominated successions by faults. The angular relations between the cataclastic rocks and the conglomerate units, combined with the presence of cataclasite clasts in the conglomerate units and evidence of dip-slip faults within the basin, suggest an extensional setting, where listric normal faults outline detachment allochthons. Allochthon geometry requires two stages of extension, the older stage completed in early Windsor Group time and including most of the island, and the more local younger stage completed in Mabou Group time. Domino-style upper-plate faulting in the younger stage locally repeated the older detachment relation of basement and conglomerate to form the observed narrow belts. Re-rotation of older successions in the younger stage also locally overturned the Horton Group. These features developed within a broad zone of Carboniferous dextral transcurrent faulting between already-docked Avalon and Meguma terranes. Sites of transpression and transtension alternated along the Cobequid-Chedabucto fault zone that separated these terranes. The earlier extensional features in Isle Madame likely represent the northern headwall and associated clastic debris of a pull-apart or other type of transtensional basin developed along part of this fault zone that had become listric; they were repeated and exposed by being up-ended in the second stage of extension, also on listric faults. The

  7. Tectono-sedimentary evolution of an extensional basin revealed by a combined photo-geological and field-mapping approach. The Montefalco Basin (Northern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Bucci, Francesco; Mirabella, Francesco; Santangelo, Michele; Cardinali, Mauro; Guzzetti, Fausto

    2016-04-01

    Active extensional basins are important since their sedimentary infills and bounding tectonic structures provide: i) sinks with preservation potential for sedimentary and fossil records of past changes in climate and sediment/water supply, ii) information on the growth, activity, decay and death of normal faults, iii) vast economic reserves of hydrocarbons, water and minerals. Unfortunately, quaternary extensional basins, especially if located in humid and temperate climate environments, are often characterized by extensively cultivated areas, homogeneous terrains and quite flat morphologies. Furthermore, they commonly host human settlements, together with roads, economic and industrial infrastructures, with a consequent limited availability of good outcrops. Such a limitation can (often severely) hamper an adequate mapping of the sedimentary infill. Therefore alternative methodological approaches (such as aerial photographs interpretation, API) are needed to integrate heterogeneous and incomplete datasets. This contribution presents an updated photo-geological map of a Quaternary extensional basin in Central Italy, the Montefalco Basin. This basin developed in a continental environment characterized by clayey-sandy lacustrine and fluvial sequences (late Pliocene - early Pleistocene) underlying more recent coarse grained deposits related to alluvial fan environment (early-to-late Pleistocene) and younger palustrine deposits (late Pleistocene). Since the late Pleistocene, regional uplift and local tectonics led to the end of deposition in the Montefalco basin, which experienced a diffuse incision and the modification of the drainage network, in response to the W-to-E migration of active faulting and tectonic subsidence. The new photo-geological map represents an important improvement compared to the existing data, since it provides unprecedented and spatially distributed information on the geometry of the continental deposits and on the tectonic structures affecting

  8. Pushing the Limits of Geological Mapping Outside the Earth: 3D Modeling of Strike-Slip and Extensional Fault Systems in Meridiani Planum Region, Mars.

    NASA Astrophysics Data System (ADS)

    Vidal Royo, O.

    2014-12-01

    GIS and geological modeling software have radically changed the means by which geological mapping is produced, published and visualized. This type of software environment normally requires a spatially aware reference system to position data and interpretation, often referred as georeferenced data (i.e. geographic data referenced on the Earth). However, for this study we coin the term areoreferenced data (i.e. Mars-referenced "geographic" data). Thanks to the wealth of areoreferenced data made available by the NASA and the HiRise at University of Arizona it is now possible to carry out 3D areographic and areologic (i.e. related to the topography and geology of Mars, respectively) reconstructions in great detail. The present work benefits from the availability of software and areographic data, and presents the results of an areologic map and 3D model of the fault systems in the Meridiani Planum of Mars. The work has been carried out in Move™ (developed by Midland Valley Exploration), a geological modeling toolkit that allows for easy data loading in a wide range of formats as well as straightforward 2D/3D model building tools of geological bodies. Initial data consisted of Digital Terrain Model and orthoimages (NASA/JPL/University of Arizona/USGS). From these we have interpreted several structural domains: right-lateral strike-slip systems with associated releasing bends, which gave room to an extensional event causing a horizontal-axis rotation of the bedding. Bedding ranges from subhorizontal in the southern domain where strike-slip prevails to nearly 40º in the central and northern domains, where a more complex interaction between strike-slip and extensional faults is described. The stratigraphic sequence is mainly composed by moderately rounded well laminated basaltic sandstones (Squyres et al., 2004) in which a high component of sulfurs (e.g. sulfate anhydrate, hexahydrite, epsomite, gypsum) and salts (e.g. halite) has been described (Squyres et al., 2004

  9. Geochemistry and geochronology of pre-Brasiliano rocks from the Transversal Zone, Borborema Province, Northeast Brazil

    NASA Astrophysics Data System (ADS)

    Sá, J. M.; Bertrand, J. M.; Leterrier, J.; Macedo, M. H. F.

    2002-03-01

    Proterozoic metamorphosed sequences are identified in the Transversal Zone (TZ) domain of the Borborema geological province, Northeast Brazil. This TZ domain is located between the well-known E-W Patos and Pernambuco continental shear zones. In its eastern part, in the Taquaritinga region, a large mass of augen gneisses with a conspicuous horizontal to subhorizontal tectonic foliation forms one of the most important rock types in the region that displays U-Pb zircon ages ca. 1.52 Ga. Paleoproterozoic orthogneisses dated by U-Pb on zircon at ca. 1.97 Ga and older paragneisses and banded gneisses represent basement rocks, which were cross-cut by these Mesoproterozoic augen gneisses, and have been in turn intruded by plutonic rocks in upper Neoproterozoic (U-Pb and Rb-Sr, ca. 0.6 Ga) times. Chemical analyses of major, minor, and trace elements (including REE) for the basement orthogneisses indicate calcalkaline affinities and a signature very similar to volcanic arc granites, representing crustal accretion during the Paleoproterozoic Transamazonian/Eburnean orogenesis in the region. In turn, the chemical data for augen gneisses indicate that they are relatively homogeneous and evolved metaluminous metaplutonic rocks with characteristics very similar to A-type granites generated and emplaced in an extensional anorogenic setting. Relatively high 87Sr/ 86Sr initial ratio and negative ɛNd( t) are signatures of crustal components in these rocks. Based on geochemical, geochronological, and structural data, the Taquaritinga region is composed of Paleoproterozoic (>1.97 Ga) rocks intruded by Mesoproterozoic (ca. 1.5 Ga) anorogenic granites and Neoproterozoic granites (ca. 0.6 Ga). These data also suggest that the tectonometamorphic structures displayed by Meso and Neoproterozoic suites were developed by the Brasiliano/Pan-African orogeny and that the record of Transamazonian/Eburnean orogeny is restricted to basement rocks. This means that there is no evidence for a

  10. Depositional architecture of a mixed travertine-terrigenous system in a fault-controlled continental extensional basin (Messinian, Southern Tuscany, Central Italy)

    NASA Astrophysics Data System (ADS)

    Croci, Andrea; Della Porta, Giovanna; Capezzuoli, Enrico

    2016-03-01

    The extensional Neogene Albegna Basin (Southern Tuscany, Italy) includes several thermogene travertine units dating from the Miocene to Holocene time. During the late Miocene (Messinian), a continental fault-controlled basin (of nearly 500-km2 width) was filled by precipitated travertine and detrital terrigenous strata, characterized by a wedge-shaped geometry that thinned northward, with a maximum thickness of nearly 70 m. This mixed travertine-terrigenous succession was investigated in terms of lithofacies types, depositional environment and architecture and the variety of precipitated travertine fabrics. Deposited as beds with thickness ranging from centimetres to a few decimetres, carbonates include nine travertine facies types: F1) clotted peloidal micrite and microsparite boundstone, F2) raft rudstone/floatstone, F3) sub-rounded radial coated grain grainstone, F4) coated gas bubble boundstone, F5) crystalline dendrite cementstone, F6) laminated boundstone, F7) coated reed boundstone and rudstone, F8) peloidal skeletal grainstone and F9) calci-mudstone and microsparstone. Beds of terrigenous deposits with thickness varying from a decimetre to > 10 m include five lithofacies: F10) breccia, F11) conglomerate, F12) massive sandstone, F13) laminated sandstone and F14) claystone. The succession recorded the following three phases of evolution of the depositional setting: 1) At the base, a northward-thinning thermogene travertine terraced slope (Phase I, travertine slope lithofacies association, F1-F6) developed close to the extensional fault system, placed southward with respect to the travertine deposition. 2) In Phase II, the accumulation of travertines was interrupted by the deposition of colluvial fan deposits with a thickness of several metres (colluvial fan lithofacies association, F10 and F12), which consisted of massive breccias, adjacent to the alluvial plain lithofacies association (F11-F14) including massive claystone and sandstone and channelized

  11. Structure and U-Pb zircon geochronology of an Alpine nappe stack telescoped by extensional detachment faulting (Kulidzhik area, Eastern Rhodopes, Bulgaria)

    NASA Astrophysics Data System (ADS)

    Georgiev, Neven; Froitzheim, Nikolaus; Cherneva, Zlatka; Frei, Dirk; Grozdev, Valentin; Jahn-Awe, Silke; Nagel, Thorsten J.

    2016-10-01

    The Rhodope Metamorphic Complex is a stack of allochthons assembled during obduction, subduction, and collision processes from Jurassic to Paleogene and overprinted by extensional detachment faults since Middle Eocene. In the study area, the following nappes occur in superposition (from base to top): an orthogneiss-dominated unit (Unit I), garnet-bearing schist with amphibolite and serpentinite lenses (Unit II), greenschist, phyllite, and calcschist with reported Jurassic microfossils (Unit III), and muscovite-rich orthogneiss (Unit IV). U-Pb dating of zircons from a K-feldspar augengneiss (Unit I) yielded a protolith age of ca. 300 Ma. Garnet-bearing metasediment from Unit II yielded an age spectrum with distinct populations between 310 and 250 Ma (detrital), ca. 150 Ma, and ca. 69 Ma (the last two of high-grade metamorphic origin). An orthogneiss from Unit IV yielded a wide spectrum of ages. The youngest population gives a concordia age of 581 ± 5 Ma, interpreted as the age of the granitic protolith. Unit I represents the Lower Allochthon (Byala Reka-Kechros Dome), Unit II the Upper Allochthon (Krumovitsa-Kimi Unit), Unit III the Uppermost Allochthon (Circum-Rhodope Belt), and Unit IV a still higher, far-travelled unit of unknown provenance. Telescoping of the entire Rhodope nappe stack to a thickness of only a few 100 m is due to Late Eocene north directed extensional shearing along the newly defined Kulidzhik Detachment which is part of a major detachment system along the northern border of the Rhodopes. Older top-to-the south mylonites in Unit I indicate that Tertiary extension evolved from asymmetric (top-to-the-south) to symmetric (top-to-the-south and top-to-the-north), bivergent unroofing.

  12. Extensional strain and displacement distribution due to mesoscale normal faults in Late Miocene-Pliocene sedimentary rocks along the northwestern side of the Red Sea, Egypt

    NASA Astrophysics Data System (ADS)

    Zaky, Kh. S.

    2015-09-01

    Field observations are presented on the NW-SE mesoscale, dip-slip, normal faults in the Late Miocene-Pliocene sedimentary rocks, along the northwestern part of the SW side of the Red Sea, Egypt. These faults were initiated parallel to the Red Sea, and were originated by the NE-SW extension associated with the Red Sea opening in the Late Oligocene-Early Miocene time. About 100 mesoscale normal faults were measured in the Late Miocene-Pliocene sedimentary rocks along seven scan-lines. The extensional strain determined in five scan-lines ranges from 2.6393 to 5.12% with an average of 3.53145%. The other two scan-lines have anomalous values of 6.2988 and 15.53%. The represented data demonstrate that the extensional strain varies significantly from profile to profile and even along the fault because of several surficial factors. The first factor is a difference in lithology. The second and third factors are the local stress and the difference between perpendicular to the direction of maximum lateral extension of area and strike of faults. The L-D (Length-Displacement) diagrams along twelve selected faults reveal three patterns. These patterns include a cone-shaped (C-type), meso-shaped (M-type), and a zigzag-shaped (Z-type). The remarkable variation of displacement (D) along the fault plane (L) is a result of the difference in lithology, and/or the overlapping fault segments, as well as the local stress along the faults.

  13. A hybrid hard- and soft-linked fault model for the development of Australian extensional basin systems: Reconciling observations from seismic, aeromagnetic and analogue modelling data

    SciTech Connect

    O'Brien, G.W.; Symonds, P.; Blevin, J. ); Higgins, R.

    1996-01-01

    A series of rift models has been developed for basin systems around Australia, via the interpretation of newly acquired deep crustal seismic and high resolution aeromagnetic data. These models, which incorporate observations on rift architecture, fault geometries, fault orientation, basement fabric/grain, extensional transport direction and reactivation history, have then been iteratively tested by over twenty-five sophisticated analogue modelling experiments. This work has led to the development of a hybrid hard-linked/soft-linked fault model for the Australian margin. In this model, basement grain is the principal control on the rift architecture that develops, with pre-existing fractures acting to establish discrete offsets (hard-linkages) between adjacent extensional faults and rift segments. It is these basement features which produce the rectilinear features which are so common on aeromagnetic data around the Australian margin. With progressively greater extension, the basement-involved, hard-linked system exerts virtually no influence over the type or intensity of faulting within the syn-rift phase, though they do control the fault location. Syn-rift faulting is dominated by [open quotes]soft-linked[close quotes] fault systems, with relay ramps/zones accommodating jumps in the position of the basin margin faults. During basin reactivation (particularly inversion), it is the location and geometry of the underpinning, hard-linked basement features which ultimately control the locations of the traps that develop in the syn- and post-rift section, whereas it is the soft-linked fault system which is the primary control on the fluid migration pathways. Reconciling these concepts provides a set of powerful predictive tools for exploring both frontier and mature basins.

  14. A hybrid hard- and soft-linked fault model for the development of Australian extensional basin systems: Reconciling observations from seismic, aeromagnetic and analogue modelling data

    SciTech Connect

    O`Brien, G.W.; Symonds, P.; Blevin, J.; Higgins, R.

    1996-12-31

    A series of rift models has been developed for basin systems around Australia, via the interpretation of newly acquired deep crustal seismic and high resolution aeromagnetic data. These models, which incorporate observations on rift architecture, fault geometries, fault orientation, basement fabric/grain, extensional transport direction and reactivation history, have then been iteratively tested by over twenty-five sophisticated analogue modelling experiments. This work has led to the development of a hybrid hard-linked/soft-linked fault model for the Australian margin. In this model, basement grain is the principal control on the rift architecture that develops, with pre-existing fractures acting to establish discrete offsets (hard-linkages) between adjacent extensional faults and rift segments. It is these basement features which produce the rectilinear features which are so common on aeromagnetic data around the Australian margin. With progressively greater extension, the basement-involved, hard-linked system exerts virtually no influence over the type or intensity of faulting within the syn-rift phase, though they do control the fault location. Syn-rift faulting is dominated by {open_quotes}soft-linked{close_quotes} fault systems, with relay ramps/zones accommodating jumps in the position of the basin margin faults. During basin reactivation (particularly inversion), it is the location and geometry of the underpinning, hard-linked basement features which ultimately control the locations of the traps that develop in the syn- and post-rift section, whereas it is the soft-linked fault system which is the primary control on the fluid migration pathways. Reconciling these concepts provides a set of powerful predictive tools for exploring both frontier and mature basins.

  15. The pre-Kos Plateau Tuff Volcanic Rocks on Kefalos Peninsula (Kos Island, Dodecanese, Greece): Crescendo to the Largest Eruption of the Modern Aegean Arc

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Schnyder, C.

    2006-12-01

    Young volcanic rocks (K-Ar ages of 3 to 0.5 Ma) from the Kefalos Peninsula (Kos Island, Dodecanese, Greece) erupted prior to the voluminous (>60 km\\ 3) Kos Plateau Tuff (KPT; Ar-Ar age of 0.16 Ma) were studied in order to better define the conditions that led to the paroxysmal eruption of the modern Aegean Arc. Two different whole-rock compositions were sampled on Kefalos peninsula; dacites (63-65 wt% SiO2) and rhyolites (75-77 wt% SiO2). Kefalos dacites are crystal-rich (>40% crystals), show high Sr-Ba contents compared to other continental arcs, and have "adakitic" Sr/Y ratios (>40). Kefalos rhyolites are typical high- SiO2 arc magmas, similar in composition and mineralogy to the KPT, but displaying lower crystallinities (<5 vol% instead of >30% in most of the KPT). The high Sr/Y ratios of the dacites is surprising in an area where the subducting slab is not particularly hot and the continental crust relatively thin (~30 km). If the low Y and high Sr-Ba contents result from the fact that magma formed deep enough to supress plagioclase and have garnet present, dacite magma generation must have occurred in the mantle. There is geochemical and mineralogical evidence for the Kefalos and KPT rhyolites being generated by fractional crystallization from magmas similar to the Kefalos dacites. However, the few distinctions between KPT and Kefalos rhyolites (KPT is more voluminous, contains more crystals, has lower whole-rock U and Th contents, and lower MgO-SiO2, but higher Al2O3-FeOtot in biotite) suggest slightly different conditions in the magma chambers. These observations, together with increasing explosivity of the volcanic products from ~3 Ma to 0.16 Ma, may indicate that the build-up to the large KPT eruption could be the result of an increase in magmatic water input in the system through time.

  16. Geomorphological characteristics of the onshore/offshore volcanic edifices with respect to their evolutionary stage in the South Aegean Sea, Greece.

    NASA Astrophysics Data System (ADS)

    Carey, S.; Nomikou, P.; Papanikolaou, D.; Alexandri, M.

    2014-12-01

    Volcanism in the South Aegean Sea first occurred about 3-4 million years ago, along four different volcanic island groups, including both onshore and recently discovered offshore volcanoes: 1) Starting from the west, the Methana group consists of the Methana stratovolcano, composed exclusively of volcaniclastics and lavas, creating cones and domes onland and the Paphsanias submarine cone in the Epidavros tectonic graben, bordered by E-W normal faults. It has a 2 km basal diameter at 400 m depth and its top rises to 150 m. 2) The Milos-Antimilos group consists of volcanic domes and calderas onland and three submarine domes to the east of Antimilos. A hydrothermal vent field is limited in the SE coastal zone of Milos, 3) The Santorini group consists of: (i) the older volcanic cones of Christianna islets and three submarine domes east of them, (ii) Santorini volcano which during the last 500 ka experienced repeated caldera collapses following Plinian eruptions and edifice rebuilding, represented by the growth of the Kamenes islands after the last catastrophic Late Bronze age eruption. (iii) a chain of about twenty submarine volcanic domes and craters in the Kolumbo zone northeast of Santorini. Kolumbo volcano is a 3 km diameter cone with a 1500 m wide crater, a crater rim as shallow as 18 m depth and a flat crater floor at 505 m depth containing an active hydrothermal vent field degassing 99% of CO2. 4) The Kos-Nisyros group at the eastern edge of the Hellenic Volcanic arc, comprises several domes and craters offshore and Nisyros volcano consists exclusively of alternating lava and pyroclastic deposits following several phases of reconstruction and caldera collapse. The rhyodacitic domes of Profitis Ilias are the latest evolutionary stage of Nisyros volcano which disrupted a pre-existed caldera and may be regarded as an earlier reconstruction phase similar to the Kameni islands at Santorini. The volcanic relief reaches 1100-1200 m in most cases. This is produced from

  17. New boron isotopic evidence for sedimentary and magmatic fluid influence in the shallow hydrothermal vent system of Milos Island (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Wu, Shein-Fu; You, Chen-Feng; Lin, Yen-Po; Valsami-Jones, Eugenia; Baltatzis, Emmanuel

    2016-01-01

    Magmatic sources may contribute a significant amount of volatiles in geothermal springs; however, their role is poorly understood in submarine hydrothermal systems worldwide. In this study, new results of B and δ11B in 41 hydrothermal vent waters collected from the shallow hydrothermal system of Milos island in the Aegean Sea were combined with previously published data from other tectonic settings and laboratory experiments to quantify the effects of phase separation, fluid/sediment interaction and magmatic contribution. Two Cl-extreme solutions were identified, high-Cl waters (Cl as high as 2000 mM) and low-Cl waters (Cl < 80 mM). Both sets of waters were characterized by high B/Cl (~ 1.2-5.3 × 10- 3 mol/mol) and extremely low δ11B (1.4-6.3‰), except for the waters with Mg content of near the seawater value and δ11B = 10.3-17.4‰. These high-Cl waters with high B/Cl and low δ11B plot close to the vent waters in sediment-hosted hydrothermal system (i.e., Okinawa Trough) or fumarole condensates from on-land volcanoes, implying B addition from sediment or magmatic fluids plays an important role. This is in agreement with fluid/sediment interactions resulting in the observed B and δ11B, as well as previously reported Br/I/Cl ratios, supporting a scenario of slab-derived fluid addition with elevated B, 11B-rich, and low Br/Cl and I/Cl, which is derived from the dehydration of subducted-sediments. The slab fluid becomes subsequently mixed with the parent magma of Milos. The deep brine reservoir is partially affected by injections of magmatic fluid/gases during degassing. The results presented here are crucial for deciphering the evolution of the brine reservoirs involved in phase separation, fluid/sediment interaction and magmatic contribution in the deep reaction zone of the Milos hydrothermal system; they also have implications in the understanding of the formation of metallic vein mineralization.

  18. Hf isotope study of Palaeozoic metaigneous rocks of La pampa province and implications for the occurrence of juvenile early Neoproterozoic (Tonian) magmatism in south-central Argentina

    NASA Astrophysics Data System (ADS)

    Chernicoff, C. J.; Zappettini, E. O.; Santos, J. O. S.; Belousova, E.; McNaughton, N. J.

    2011-12-01

    On a global scale, juvenile Tonian (Early Neoproterozoic) magmatic rocks are associated with the extensional events that lead to the breakup of the Rodinia supercontinent. In Argentina, no geological record is available for this time interval, lasting from 1000 to 850 Ma. We present indirect evidence for the existence of Tonian extension in Argentina, as supported by Hf and Nd isotope determinations on Phanerozoic magmatic and sedimentary rocks. We mainly focus on our own Hf isotope determinations carried out on U-Pb SHRIMP dated zircons from Palaeozoic metaigneous rocks of La Pampa province, south-central Argentina, i.e. metagabbros of Valle Daza, dioritic orthogneiss of Estancia Lote 8, and metadiorite of Estancia El Carancho, having found that these rocks were derived from sources of ca. 920 to ca 880 Ma, with ɛHf values between +6.83 and + 9.59. Inherited zircons of this age and character identified in these rocks also point to the same source. We also compile additional Hf and Nd studies from previous work on Phanerozoic magmatic and sedimentary rocks. We preliminarily compare the age of the juvenile Tonian sources referred to in our work with that of two extensional events identified in the São Francisco craton, Brazil.

  19. Assessment of undiscovered petroleum resources of the Amerasia Basin Petroleum Province

    USGS Publications Warehouse

    Houseknecht, David W.; Bird, Kenneth J.; Garrity, Christopher P.

    2012-01-01

    The Amerasia Basin Petroleum Province encompasses the Canada Basin and the sediment prisms along the Alaska and Canada margins, outboard from basinward margins (hingelines) of the rift shoulders that formed during extensional opening of the Canada Basin. The province includes the Mackenzie delta and slope, the outer shelves and marine slopes along the Arctic margins of Alaska and Canada, and the deep Canada Basin. The province is divided into four assessment units (AUs): (1) The Canning-Mackenzie deformed margin AU is that part of the rifted margin where the Brooks Range orogenic belt has overridden the rift shoulder and is deforming the rifted-margin prism of sediment outboard of the hingeline. This is the only part of the Amerasia Basin Province that has been explored and—even though more than 3 billion barrels of oil equivalent (BBOE) of oil, gas, and condensate have been discovered—none has been commercially produced. (2) The Alaska passive margin AU is the rifted-margin prism of sediment lying beneath the Beaufort outer shelf and slope that has not been deformed by tectonism. (3) The Canada passive margin AU is the rifted-margin prism of sediment lying beneath the Arctic outer shelf and slope (also known as the polar margin) of Canada that has not been deformed by tectonism. (4) The Canada Basin AU includes the sediment wedge that lies beneath the deep Canada Basin, north of the marine slope developed along the Alaska and Canada margins. Mean estimates of risked, undiscovered, technically recoverable resources include more than 6 billion barrels of oil (BBO), more than 19 trillion cubic feet (TCF) of associated gas, and more than 16 TCF of nonassociated gas in the Canning-Mackenzie deformed margin AU; about 1 BBO, about 3 TCF of associated gas, and about 3 TCF of nonassociated gas in the Alaska passive margin AU; and more than 2 BBO, about 7 TCF of associated gas, and about 8 TCF of nonassociated gas in the Canada passive margin AU. Quantities of natural

  20. On the Prepuna biogeographic province: A nomenclatural clarification.

    PubMed

    Morrone, Juan J; Ezcurra, Cecilia

    2016-06-29

    The nomenclatural status of the Prepuna province sensu Cabrera (1951) and sensu Morrone (1999) is clarified. The Prepuna province sensu Cabrera (1951) is demoted to a district of the Monte province, stat. nov. The valid name of the Prepuna province sensu Morrone (1999) is Cuyan High Andean province Cabrera, 1971, stat. nov. Diagnoses of these areas are provided and their endemic taxa are listed.

  1. Isotopic evolution of the idaho batholith and Challis intrusive province, Northern US Cordillera

    USGS Publications Warehouse

    Gaschnig, R.M.; Vervoort, J.D.; Lewis, R.S.; Tikoff, B.

    2011-01-01

    The Idaho batholith and spatially overlapping Challis intrusive province in the North American Cordillera have a history of magmatism spanning some 55 Myr. New isotopic data from the ???98 Ma to 54 Ma Idaho batholith and ???51 Ma to 43 Ma Challis intrusions, coupled with recent geochronological work, provide insights into the evolution of magmatism in the Idaho segment of the Cordillera. Nd and Hf isotopes show clear shifts towards more evolved compositions through the batholith's history and Pb isotopes define distinct fields correlative with the different age and compositionally defined suites of the batholith, whereas the Sr isotopic compositions of the various suites largely overlap. The subsequent Challis magmatism shows the full range of isotopic compositions seen in the batholith. These data suggest that the early suites of metaluminous magmatism (98-87 Ma) represent crust-mantle hybrids. Subsequent voluminous Atlanta peraluminous suite magmatism (83-67 Ma) results primarily from melting of different crustal components. This can be attributed to crustal thickening, resulting from either subduction processes or an outboard terrane collision. A later, smaller crustal melting episode, in the northern Idaho batholith, resulted in the Bitterroot peraluminous suite (66-54 Ma) and tapped different crustal sources. Subsequent Challis magmatism was derived from both crust and mantle sources and corresponds to extensional collapse of the over-thickened crust. ?? The Author 2011. Published by Oxford University Press. All rights reserved.

  2. The seismogenic structure of the 2013-2014 Matese seismic sequence, Southern Italy: implication for the geometry of the Apennines active extensional belt

    NASA Astrophysics Data System (ADS)

    Ferranti, L.; Milano, G.; Burrato, P.; Palano, M.; Cannavò, F.

    2015-05-01

    Seismological, geological and geodetic data have been integrated to characterize the seismogenic structure of the late 2013-early 2014 moderate energy (maximum local magnitude MLmax = 4.9) seismic sequence that struck the interior of the Matese Massif, part of the Southern Apennines active extensional belt. The sequence, heralded by a ML = 2.7 foreshock, was characterized by two main shocks with ML = 4.9 and ML = 4.2, respectively, which occurred at a depth of ˜17-18 km. The sequence was confined in the 10-20 km depth range, significantly deeper than the 1997-1998 sequence which occurred few km away on the northeastern side of the massif above ˜15 km depth. The depth distribution of the 2013-14 sequence is almost continuous, albeit a deeper (16-19 km) and a shallower (11-15 km) group of events can be distinguished, the former including the main shocks and the foreshock. The epicentral distribution formed a ˜10 km long NNW-SSE trending alignment, which almost parallels the surface trace of late Pliocene-Quaternary southwest-dipping normal faults with a poor evidence of current geological and geodetic deformation. We built an upper crustal model profile for the eastern Matese massif through integration of geological data, oil exploration well logs and seismic tomographic images. Projection of hypocentres on the profile suggests that the seismogenic volume falls mostly within the crystalline crust and subordinately within the Mesozoic sedimentary cover of Apulia, the underthrust foreland of the Southern Apennines fold and thrust belt. Geological data and the regional macroseismic field of the sequence suggest that the southwest-dipping nodal plane of the main shocks represents the rupture surface that we refer to here as the Matese fault. The major lithological discontinuity between crystalline and sedimentary rocks of Apulia likely confined upward the rupture extent of the Matese fault. Repeated coseismic failure represented by the deeper group of events in the

  3. Income and health inequality across Canadian provinces.

    PubMed

    Safaei, Jalil

    2007-09-01

    This paper uses the aggregate data from the Public Use Microdata Files (PUMF) of Canadian National Population Health Survey to estimate income related health inequalities across the ten Canadian provinces. The unique features of the PUMF allow for a meaningful cross-provincial comparison of health indices and their measured inequalities. It concludes that health inequalities favouring the higher income people do exist in all provinces when health status is either self assessed or measured by the health utility index. Moreover, it finds considerable variations in measured health inequalities across the provinces with consistent rankings for certain provinces.

  4. Geology, geochronology and tectonic setting of late Cenozoic volcanism along the southwestern Gulf of Mexico: The Eastern Alkaline Province revisited

    NASA Astrophysics Data System (ADS)

    Ferrari, Luca; Tagami, Takahiro; Eguchi, Mugihiko; Orozco-Esquivel, Ma. Teresa; Petrone, Chiara M.; Jacobo-Albarrán, Jorge; López-Martínez, Margarita

    2005-09-01

    A NNW-trending belt of alkaline mafic volcanic fields parallels the Gulf of Mexico from the U.S. border southward to Veracruz state, in eastern Mexico. Previous studies grouped this volcanism into the so-called "Eastern Alkaline Province" (EAP) and suggested that it resulted from Gulf-parallel extensional faulting migrating from north to south from Oligocene to Present. On the basis of new geologic studies, forty-nine unspiked K-Ar and two 40Ar- 39Ar ages, we propose a new geodynamic model for the volcanism along the southwestern Gulf of Mexico. We studied in detail four of the six recognized fields of mafic alkaline volcanism in Veracruz state: 1) The lavas flows of Tlanchinol area (7.3-5.7 Ma), 2) the Alamo monogenetic field and Sierra de Tantima (7.6-6.6 Ma), 3) the Poza Rica and Metlatoyuca lava flows (1.6-1.3 Ma) and 4) the Chiconquiaco-Palma Sola area (6.9-3.2 Ma). Other two mafic volcanic fields may represent the continuation of alkaline volcanism to the southeast: the Middle Miocene lavas at Anegada High, offshore port of Veracruz, and the Middle to Late Miocene volcanism at the Los Tuxtlas. The existence of major Neogene extensional faults parallel to the Gulf of Mexico (i.e., ˜N-S to NNW-SSE) proposed in previous works was not confirmed by our geological studies. Elongation of volcanic necks, vent alignment, and faults mapped by subsurface data trend dominantly NE to ENE and NW to NNW. These directions are parallel to transform and normal faults that formed during the Late Jurassic opening of the Gulf of Mexico. Ascent of mafic magmas was likely facilitated and controlled by the existence of these pre-existing basement structures. Coupled with previous studies, our data demonstrate the occurrence of three magmatic episodes in Veracruz: 1) A Middle Miocene (˜15-11 Ma) episode in southern Veracruz (Palma Sola, Anegada, and Los Tuxtlas); 2) A Late Miocene to Early Pliocene (˜7.5-3 Ma) pulse of mafic alkaline volcanism throughout the study region; and 3) A

  5. Inferences of Integrated Lithospheric Strength from Plate-Scale Analyses of Deformation Observed in the Aegean-Anatolian Region and the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Houseman, Gregory

    2016-04-01

    In the context of a comprehensive review of the rheology and strength of the lithosphere (Marine and Petroleum Geology, 2011, doi:10.1016/j.marpetgeo.2011.05.008), Evgene Burov described the difficulty of extrapolating rock deformation laws derived from laboratory experiments to the time and length scales that apply when the Earth's lithosphere is deformed. Not only does the extrapolation introduce a large uncertainty, but even the relative importance of different possible mechanisms of deformation may be uncertain. Even though lithospheric deformation has a strong conceptual and theoretical basis, it is therefore essential, as Burov argued, that deformation laws for the lithosphere must be calibrated by using observations of deformation that occurs on a lithospheric length scale and at geological strain rates. The influence of regionally varying factors like crustal thickness, geothermal gradient and tectonic environment may induce large variations in how rapidly the lithosphere may deform in response to an applied load, not least in the contrast from continent to ocean. Plates may be deformed by different loading mechanisms but, when deformation is distributed over a broad region, the strain-rate field may be approximately constant with depth and we may integrate the in-plane stress components across the thickness of the lithosphere to derive a depth-averaged constitutive law for the deformation. This approximation is the basis for the thin viscous sheet formulation of lithospheric deformation and, in combination with appropriate observations, it allows us to calibrate the integrated resistance to processes like regional extension or convergence. In this talk I will summarise what we learn about effective lithospheric rheology from two recent studies of the distribution and rates of diffuse deformation of the lithosphere in, firstly the Anatolian-Aegean region, and secondly the Central Indian Ocean. In the first case the distribution of deformation i