WorldWideScience

Sample records for plate tectonic reconstruction

  1. Plate tectonic reconstruction of the Carpathian-Pannonian region

    Science.gov (United States)

    Csontos, L.; Vörös, A.

    2003-04-01

    Plate tectonics of the Carpathian area is controlled by microcontinents between the European and African margins and the relative movements of these margins. Beside the generally accepted Apulian (Austroalpine, West Carpathian, Dinaric) microcontinents two others: the Bihor-Getic (Tisza) and Drina-Ivanjica are introduced. The first was attached to the European margin, the second to the Apulian microcontinent. During Permian a major ocean was obliquely subducted south of the Apulian microcontinents. Drina-Ivanjica rifted off the Apulian microcontinent in the Late Permian-Middle Triassic, as a consequence of back-arc rifting. Short-lived oceans subducted by the end of Jurassic, causing Drina-Ivanjica to collide with the internal Dinaric-West Carpathian and Bihor-Getic margins. An external Penninic-Váhic ocean tract began opening in the Early Jurassic, separating the East Alpine-West Carpathian microcontinent (and its fauna) from the European shelf. Further south, the Severin-Ceahlau-Magura also began opening in the Early Jurassic, but final separation of the Bihor-Getic (and its fauna) from the European shelf did not take place until the Middle-Late Jurassic. Two oroclinal bends: the Alcapa on the Dinaric margin and the Tisza-Dacia on the South Carpathian-Getic margin are essential elements of these reconstructions. Their bending (Aptian and Albian-Maastrichtian, respectively) are suggested by paleomagnetic and tectonic transport data. The two oroclinal bends are finally opposed and pushed into the Carpathian embayment by the Paleogene. In Miocene a back-arc basin develops on older tectonic elements. Differential rotations affect the wealded microcontinents.

  2. Plate tectonics

    Digital Repository Service at National Institute of Oceanography (India)

    Chaubey, A.K.

    's continental drift theory was later disproved, it was one of the first times that the idea of crustal movement had been introduced to the scientific community; and it has laid the groundwork for the development of modern plate tectonics. In the early... of the structure of the atom was to physical sciences and the theory of evolution was to the life sciences. Tectonics is the study of the forces within the Earth that give rise to continents, ocean basins, mountain ranges, earthquake belts and other large-scale...

  3. Playing jigsaw with Large Igneous Provinces—A plate tectonic reconstruction of Ontong Java Nui, West Pacific

    Science.gov (United States)

    Hochmuth, Katharina; Gohl, Karsten; Uenzelmann-Neben, Gabriele

    2015-11-01

    The three largest Large Igneous Provinces (LIP) of the western Pacific—Ontong Java, Manihiki, and Hikurangi Plateaus—were emplaced during the Cretaceous Normal Superchron and show strong similarities in their geochemistry and petrology. The plate tectonic relationship between those LIPs, herein referred to as Ontong Java Nui, is uncertain, but a joined emplacement was proposed by Taylor (2006). Since this hypothesis is still highly debated and struggles to explain features such as the strong differences in crustal thickness between the different plateaus, we revisited the joined emplacement of Ontong Java Nui in light of new data from the Manihiki Plateau. By evaluating seismic refraction/wide-angle reflection data along with seismic reflection records of the margins of the proposed "Super"-LIP, a detailed scenario for the emplacement and the initial phase of breakup has been developed. The LIP is a result of an interaction of the arriving plume head with the Phoenix-Pacific spreading ridge in the Early Cretaceous. The breakup of the LIP shows a complicated interplay between multiple microplates and tectonic forces such as rifting, shearing, and rotation. Our plate kinematic model of the western Pacific incorporates new evidence from the breakup margins of the LIPs, the tectonic fabric of the seafloor, as well as previously published tectonic concepts such as the rotation of the LIPs. The updated rotation poles of the western Pacific allow a detailed plate tectonic reconstruction of the region during the Cretaceous Normal Superchron and highlight the important role of LIPs in the plate tectonic framework.

  4. Seismic tomographic constraints on plate-tectonic reconstructions of Nazca subduction under South America since late Cretaceous (˜80 Ma)

    Science.gov (United States)

    Chen, Y. W.; Wu, J.; Suppe, J.

    2017-12-01

    Global seismic tomography has provided new and increasingly higher resolution constraints on subducted lithospheric remnants in terms of their position, depth, and volumes. In this study we aim to link tomographic slab anomalies in the mantle under South America to Andean geology using methods to unfold (i.e. structurally restore) slabs back to earth surface and input them to globally consistent plate reconstructions (Wu et al., 2016). The Andean margin of South America has long been interpreted as a classic example of a continuous subduction system since early Jurassic or later. However, significant gaps in Andean plate tectonic reconstructions exist due to missing or incomplete geology from extensive Nazca-South America plate convergence (i.e. >5000 km since 80 Ma). We mapped and unfolded the Nazca slab from global seismic tomography to produce a quantitative plate reconstruction of the Andes back to the late Cretaceous 80 Ma. Our plate model predicts the latest phase of Nazca subduction began in the late Cretaceous subduction after a 100 to 80 Ma plate reorganization, which is supported by Andean geology that indicates a margin-wide compressional event at the mid-late Cretaceous (Tunik et al., 2010). Our Andean plate tectonic reconstructions predict the Andean margin experienced periods of strike-slip/transtensional and even divergent plate tectonics between 80 to 55 Ma. This prediction is roughly consistent with the arc magmatism from northern Chile between 20 to 36°S that resumed at 80 Ma after a magmatic gap. Our model indicates the Andean margin only became fully convergent after 55 Ma. We provide additional constraints on pre-subduction Nazca plate paleogeography by extracting P-wave velocity perturbations within our mapped slab surfaces following Wu et al. (2016). We identified localized slow anomalies within our mapped Nazca slab that apparently show the size and position of the subducted Nazca ridge, Carnegie ridge and the hypothesized Inca plateau

  5. Origin of marginal basins of the NW Pacific and their plate tectonic reconstructions

    Science.gov (United States)

    Xu, Junyuan; Ben-Avraham, Zvi; Kelty, Tom; Yu, Ho-Shing

    2014-03-01

    Geometry of basins can indicate their tectonic origin whether they are small or large. The basins of Bohai Gulf, South China Sea, East China Sea, Japan Sea, Andaman Sea, Okhotsk Sea and Bering Sea have typical geometry of dextral pull-apart. The Java, Makassar, Celebes and Sulu Seas basins together with grabens in Borneo also comprise a local dextral, transform-margin type basin system similar to the central and southern parts of the Shanxi Basin in geometry. The overall configuration of the Philippine Sea resembles a typical sinistral transpressional "pop-up" structure. These marginal basins except the Philippine Sea basin generally have similar (or compatible) rift history in the Cenozoic, but there do be some differences in the rifting history between major basins or their sub-basins due to local differences in tectonic settings. Rifting kinematics of each of these marginal basins can be explained by dextral pull-apart or transtension. These marginal basins except the Philippine Sea basin constitute a gigantic linked, dextral pull-apart basin system.

  6. Plate tectonics in the late Paleozoic

    Directory of Open Access Journals (Sweden)

    Mathew Domeier

    2014-05-01

    Full Text Available As the chronicle of plate motions through time, paleogeography is fundamental to our understanding of plate tectonics and its role in shaping the geology of the present-day. To properly appreciate the history of tectonics—and its influence on the deep Earth and climate—it is imperative to seek an accurate and global model of paleogeography. However, owing to the incessant loss of oceanic lithosphere through subduction, the paleogeographic reconstruction of ‘full-plates’ (including oceanic lithosphere becomes increasingly challenging with age. Prior to 150 Ma ∼60% of the lithosphere is missing and reconstructions are developed without explicit regard for oceanic lithosphere or plate tectonic principles; in effect, reflecting the earlier mobilistic paradigm of continental drift. Although these ‘continental’ reconstructions have been immensely useful, the next-generation of mantle models requires global plate kinematic descriptions with full-plate reconstructions. Moreover, in disregarding (or only loosely applying plate tectonic rules, continental reconstructions fail to take advantage of a wealth of additional information in the form of practical constraints. Following a series of new developments, both in geodynamic theory and analytical tools, it is now feasible to construct full-plate models that lend themselves to testing by the wider Earth-science community. Such a model is presented here for the late Paleozoic (410–250 Ma together with a review of the underlying data. Although we expect this model to be particularly useful for numerical mantle modeling, we hope that it will also serve as a general framework for understanding late Paleozoic tectonics, one on which future improvements can be built and further tested.

  7. Plate tectonic reconstruction of India and Madagascar closing through the Mascarene Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Shuhail, M.

    anomaly information from Mascarene Basin forced all those studies to follow the IND-ANT-AFR circuit to obtain India-Madagascar reconstruction models in their pre-drift scenario (e.g. Fig. 2a). Since those models were not accounted for the deformation....1029/2007GC001743 3. Royer et al., 2002, Geological Society of London Special Publication 195, 7-23 4. Yatheesh et al., 2006, Gondwana Research 10, 179-185. PhD with the guidance of V. Yatheesh and G.C. Bhattacharya. CSIR-NIO/UGC are acknowledged...

  8. Soft Plate and Impact Tectonics

    Science.gov (United States)

    Tikoff, Basil

    In the field of tectonics, most of our ideas are published in journals. This is not true of other fields, such as history, in which ideas are primarily published in books. Within my own field of structural geology, I can recall only one book, Strain Fades by E. Hansen (Springer-Verlag, 1971), which presents a new idea in book form. However, even this book is more useful for its philosophical approach and particular methodology of determining directions of folding, than for its overarching idea.Enter Soft Plate and Impact Tectonics, a new book with an interesting hypothesis that has been informally discussed in the geoscience community: A fundamental tenet of plate tectonics is incorrect—namely, that the plates are rigid. This assertion is evident when looking at any mountain range, and is perhaps most clearly stated in Molnar [1988].

  9. The tectonic plates are moving!

    CERN Document Server

    Livermore, Roy

    2018-01-01

    Written in a witty and informal style, this book explains modern plate tectonics in a non-technical manner, showing not only how it accounts for phenomena such as great earthquakes, tsunamis, and volcanic eruptions, but also how it controls conditions at the Earth’s surface, including global geography and climate, making it suitable for life. The book presents the advances that have been made since the establishment of plate tectonics in the 1960s, highlighting, on the fiftieth anniversary of the theory, the contributions of a small number of scientists who have never been widely recognized for their discoveries. Beginning with the publication of a short article in Nature by Vine and Matthews, the book traces the development of plate tectonics through two generations of the theory. First-generation plate tectonics covers the exciting scientific revolution of the 1960s, its heroes, and its villains. The second generation includes the rapid expansions in sonar, satellite, and seismic technologies during the 1...

  10. Indonesian Landforms and Plate Tectonics

    Directory of Open Access Journals (Sweden)

    Herman Th. Verstappen

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v5i3.103The horizontal configuration and vertical dimension of the landforms occurring in the tectonically unstable parts of Indonesia were resulted in the first place from plate tectonics. Most of them date from the Quaternary and endogenous forces are ongoing. Three major plates – the northward moving Indo-Australian Plate, the south-eastward moving SE-Asian Plate and the westward moving Pacific Plate - meet at a plate triple-junction situated in the south of New Guinea’s Bird’s Head. The narrow North-Moluccan plate is interposed between the Asia and Pacific. It tapers out northward in the Philippine Mobile Belt and is gradually disappearing. The greatest relief amplitudes occur near the plate boundaries: deep ocean trenches are associated with subduction zones and mountain ranges with collision belts. The landforms of the more stable areas of the plates date back to a more remote past and, where emerged, have a more subdued relief that is in the first place related to the resistance of the rocks to humid tropical weathering Rising mountain ranges and emerging island arcs are subjected to rapid humid-tropical river erosions and mass movements. The erosion products accumulate in adjacent sedimentary basins where their increasing weight causes subsidence by gravity and isostatic compensations. Living and raised coral reefs, volcanoes, and fault scarps are important geomorphic indicators of active plate tectonics. Compartmental faults may strongly affect island arcs stretching perpendicular to the plate movement. This is the case on Java. Transcurrent faults and related pull-apart basins are a leading factor where plates meet at an angle, such as on Sumatra. The most complicated situation exists near the triple-junction and in the Moluccas. Modern research methods, such as GPS measurements of plate movements and absolute dating of volcanic outbursts and raised coral reefs are important tools. The mega-landforms resulting

  11. Plate tectonics, habitability and life

    Science.gov (United States)

    Spohn, Tilman; Breuer, Doris

    2016-04-01

    The role of plate tectonics in defining habitability of terrestrial planets is being increasingly discussed (e.g., Elkins-Tanton, 2015). Plate tectonics is a significantly evolved concept with a large variety of aspects. In the present context, cycling of material between near surface and mantle reservoirs is most important. But increased heat transport through mixing of cold lithosphere with the deep interior and formation of continental crust may also matter. An alternative mechanism of material cycling between these reservoirs is hot-spot volcanism combined with crust delamination. Hot-spot volcanism will transport volatiles to the atmosphere while delamination will mix crust, possibly altered by sedimentation and chemical reactions, with the mantle. The mechanism works as long as the stagnant lithosphere plate has not grown thicker than the crust and as long as volcanic material is added onto the crust. Thermal evolution studies suggest that the mechanism could work for the first 1-2 Ga of planetary evolution. The efficiency of the mechanism is limited by the ratio of extrusive to intrusive volcanism, which is thought to be less than 0.25. Plate tectonics would certainly have an advantage by working even for more evolved planets. A simple, most-used concept of habitability requires the thermodynamic stability of liquid water on the surface of a planet. Cycling of CO2between the atmosphere, oceans and interior through subduction and surface volcanism is an important element of the carbonate-silicate cycle, a thermostat feedback cycle that will keep the atmosphere from entering into a runaway greenhouse. Calculations for a model Earth lacking plate tectonics but degassing CO2, N, and H2O to form a surface ocean and a secondary atmosphere (Tosi et al, 2016) suggest that liquid water can be maintained on the surface for 4.5Ga. The model planet would then qualify as habitable. It is conceivable that the CO2 buffering capability of its ocean together with silicate

  12. Towards community-driven paleogeographic reconstructions: integrating open-access paleogeographic and paleobiology data with plate tectonics

    Directory of Open Access Journals (Sweden)

    N. Wright

    2013-03-01

    Full Text Available A variety of paleogeographic reconstructions have been published, with applications ranging from paleoclimate, ocean circulation and faunal radiation models to resource exploration; yet their uncertainties remain difficult to assess as they are generally presented as low-resolution static maps. We present a methodology for ground-truthing the digital Palaeogeographic Atlas of Australia by linking the GPlates plate reconstruction tool to the global Paleobiology Database and a Phanerozoic plate motion model. We develop a spatio-temporal data mining workflow to validate the Phanerozoic Palaeogeographic Atlas of Australia with paleoenvironments derived from fossil data. While there is general agreement between fossil data and the paleogeographic model, the methodology highlights key inconsistencies. The Early Devonian paleogeographic model of southeastern Australia insufficiently describes the Emsian inundation that may be refined using biofacies distributions. Additionally, the paleogeographic model and fossil data can be used to strengthen numerical models, such as the dynamic topography and the associated inundation of eastern Australia during the Cretaceous. Although paleobiology data provide constraints only for paleoenvironments with high preservation potential of organisms, our approach enables the use of additional proxy data to generate improved paleogeographic reconstructions.

  13. Subduction Drive of Plate Tectonics

    Science.gov (United States)

    Hamilton, W. B.

    2003-12-01

    Don Anderson emphasizes that plate tectonics is self-organizing and is driven by subduction, which rights the density inversion generated as oceanic lithosphere forms by cooling of asthenosphere from the top. The following synthesis owes much to many discussions with him. Hinge rollback is the key to kinematics, and, like the rest of actual plate behavior, is incompatible with bottom-up convection drive. Subduction hinges (which are under, not in front of, thin leading parts of arcs and overriding plates) roll back into subducting plates. The Pacific shrinks because bounding hinges roll back into it. Colliding arcs, increasing arc curvatures, back-arc spreading, and advance of small arcs into large plates also require rollback. Forearcs of overriding plates commonly bear basins which preclude shortening of thin plate fronts throughout periods recorded by basin strata (100 Ma for Cretaceous and Paleogene California). This requires subequal rates of advance and rollback, and control of both by subduction. Convergence rate is equal to rates of rollback and advance in many systems but is greater in others. Plate-related circulation probably is closed above 650 km. Despite the popularity of concepts of plumes from, and subduction into, lower mantle, there is no convincing evidence for, and much evidence against, penetration of the 650 in either direction. That barrier not only has a crossing-inhibiting negative Clapeyron slope but also is a compositional boundary between fractionated (not "primitive"), sluggish lower mantle and fertile, mobile upper mantle. Slabs sink more steeply than they dip. Slabs older than about 60 Ma when their subduction began sink to, and lie down on and depress, the 650-km discontinuity, and are overpassed, whereas younger slabs become neutrally buoyant in mid-upper mantle, into which they are mixed as they too are overpassed. Broadside-sinking old slabs push all upper mantle, from base of oceanic lithosphere down to the 650, back under

  14. Earth's Decelerating Tectonic Plates

    Energy Technology Data Exchange (ETDEWEB)

    Forte, A M; Moucha, R; Rowley, D B; Quere, S; Mitrovica, J X; Simmons, N A; Grand, S P

    2008-08-22

    Space geodetic and oceanic magnetic anomaly constraints on tectonic plate motions are employed to determine a new global map of present-day rates of change of plate velocities. This map shows that Earth's largest plate, the Pacific, is presently decelerating along with several other plates in the Pacific and Indo-Atlantic hemispheres. These plate decelerations contribute to an overall, globally averaged slowdown in tectonic plate speeds. The map of plate decelerations provides new and unique constraints on the dynamics of time-dependent convection in Earth's mantle. We employ a recently developed convection model constrained by seismic, geodynamic and mineral physics data to show that time-dependent changes in mantle buoyancy forces can explain the deceleration of the major plates in the Pacific and Indo-Atlantic hemispheres.

  15. Reducing risk where tectonic plates collide

    Science.gov (United States)

    Gomberg, Joan S.; Ludwig, Kristin A.

    2017-06-19

    Most of the world’s earthquakes, tsunamis, landslides, and volcanic eruptions are caused by the continuous motions of the many tectonic plates that make up the Earth’s outer shell. The most powerful of these natural hazards occur in subduction zones, where two plates collide and one is thrust beneath another. The U.S. Geological Survey’s (USGS) “Reducing Risk Where Tectonic Plates Collide—A USGS Plan to Advance Subduction Zone Science” is a blueprint for building the crucial scientific foundation needed to inform the policies and practices that can make our Nation more resilient to subduction zone-related hazards.

  16. Spreading continents kick-started plate tectonics.

    Science.gov (United States)

    Rey, Patrice F; Coltice, Nicolas; Flament, Nicolas

    2014-09-18

    Stresses acting on cold, thick and negatively buoyant oceanic lithosphere are thought to be crucial to the initiation of subduction and the operation of plate tectonics, which characterizes the present-day geodynamics of the Earth. Because the Earth's interior was hotter in the Archaean eon, the oceanic crust may have been thicker, thereby making the oceanic lithosphere more buoyant than at present, and whether subduction and plate tectonics occurred during this time is ambiguous, both in the geological record and in geodynamic models. Here we show that because the oceanic crust was thick and buoyant, early continents may have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading, to initiate subduction at their margins and to trigger episodes of subduction. Our model predicts the co-occurrence of deep to progressively shallower mafic volcanics and arc magmatism within continents in a self-consistent geodynamic framework, explaining the enigmatic multimodal volcanism and tectonic record of Archaean cratons. Moreover, our model predicts a petrological stratification and tectonic structure of the sub-continental lithospheric mantle, two predictions that are consistent with xenolith and seismic studies, respectively, and consistent with the existence of a mid-lithospheric seismic discontinuity. The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth's interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining.

  17. Quantitative tectonic reconstructions of Zealandia based on crustal thickness estimates

    Science.gov (United States)

    Grobys, Jan W. G.; Gohl, Karsten; Eagles, Graeme

    2008-01-01

    Zealandia is a key piece in the plate reconstruction of Gondwana. The positions of its submarine plateaus are major constraints on the best fit and breakup involving New Zealand, Australia, Antarctica, and associated microplates. As the submarine plateaus surrounding New Zealand consist of extended and highly extended continental crust, classic plate tectonic reconstructions assuming rigid plates and narrow plate boundaries fail to reconstruct these areas correctly. However, if the early breakup history shall be reconstructed, it is crucial to consider crustal stretching in a plate-tectonic reconstruction. We present a reconstruction of the basins around New Zealand (Great South Basin, Bounty Trough, and New Caledonia Basin) based on crustal balancing, an approach that takes into account the rifting and thinning processes affecting continental crust. In a first step, we computed a crustal thickness map of Zealandia using seismic, seismological, and gravity data. The crustal thickness map shows the submarine plateaus to have a uniform crustal thickness of 20-24 km and the basins to have a thickness of 12-16 km. We assumed that a reconstruction of Zealandia should close the basins and lead to a most uniform crustal thickness. We used the standard deviation of the reconstructed crustal thickness as a measure of uniformity. The reconstruction of the Campbell Plateau area shows that the amount of extension in the Bounty Trough and the Great South Basin is far smaller than previously thought. Our results indicate that the extension of the Bounty Trough and Great South Basin occurred simultaneously.

  18. LOWLID FORMATION AND PLATE TECTONICS ON EXOPLANETS

    Science.gov (United States)

    Stamenkovic, V.; Noack, L.; Breuer, D.

    2009-12-01

    The last years of astronomical observation have opened the doors to a universe filled with extrasolar planets. Detection techniques still only offer the possibility to detect mainly Super-Earths above five Earth masses. But detection techniques do steadily improve and are offering the possibility to detect even smaller planets. The observations show that planets seem to exist in many possible sizes just as the planets and moons of our own solar system do. It is only a natural question to ask if planetary mass has an influence on some key habitability factors such as on plate tectonics, allowing us to test which exoplanets might be more likely habitable than others, and allowing us to understand if plate tectonics on Earth is a stable or a critical, instable process that could easily be perturbed. Here we present results derived from 1D parameterized thermal evolution and 2D/3D computer models, showing how planetary mass influences the propensity of plate tectonics for planets with masses ranging from 0.1 to 10 Earth masses. Lately [2, 3] studied the effect of planetary mass on the ability to break plates and hence initiate plate tectonics - but both derived results contradictory to the other. We think that one of the reasons why both studies [2, 3] are not acceptable in their current form is partly due to an oversimplification. Both treated viscosity only temperature-dependent but neglected the effect pressure has on enlarging the viscosity in the deep mantle. More massive planets have therefore a stronger pressure-viscosity-coupling making convection at high pressures sluggish or even impossible. For planets larger than two Earth masses we observe that a conductive lid (termed low-lid) forms above the core-mantle boundary and thus reduces the effective convective part of the mantle when including a pressure-dependent term into the viscosity laws as shown in [1]. Moreover [2, 3] use time independent steady state models neglecting the fact that plate tectonics is a

  19. From Plate Tectonic to Continental Dynamics

    Science.gov (United States)

    Molnar, P. H.

    2017-12-01

    By the early 1970s, the basics of plate tectonics were known. Although much understanding remained to be gained, as a topic of research, plate tectonics no longer defined the forefront of earth science. Not only had it become a foundation on which to build, but also the methods used to reveal it became tools to take in new directions. For me as a seismologist studying earthquakes and active processes, the deformation of continents offered an obvious topic to pursue. Obviously examining the deformation of continents and ignoring the widespread geologic evidence of both ongoing and finite deformation of crust would be stupid. I was blessed with the opportunity to learn from and collaborate with two of the best, Paul Tapponnier and Clark Burchfiel. Continental deformation differed from plate tectonics both because deformation was widespread but more importantly because crust shortens (extends) horizontally and thickens (thins), processes that can be ignored where plate tectonics - the relative motion of rigid plates - occurs. Where a plate boundary passes into a continent, not only must the forces that move plates do work against friction or other dissipative processes, but where high terrain is created, they must also do work against gravity, to create gravitational potential energy in high terrain. Peter Bird and Kenneth Piper and Philip England and Dan McKenzie showed that a two-dimensional thin viscous sheet with vertically averaged properties enabled both sources of resistance to be included without introducing excessive complexity and to be scaled by one dimensionless number, what the latter pair called the Argand number. Increasingly over the past thirty years, emphasis has shifted toward the role played by the mantle lithosphere, because of both its likely strength and its negative buoyancy, which makes it gravitationally unstable. Despite progress since realizing that rigid plates (the essence of plate tectonics) provides a poor description of continental

  20. Crustal thickness controlled by plate tectonics

    DEFF Research Database (Denmark)

    Artemieva, Irina M.; Meissner, Rolf

    2012-01-01

    /gabbro–eclogite phase transition in crustal evolution and the links between lithosphere recycling, mafic magmatism, and crustal underplating. We advocate that plate tectonics processes, togetherwith basalt/gabbro–eclogite transition, limit crustal thickness worldwide by providing effective mechanisms of crustal...

  1. Global Dynamic Numerical Simulations of Plate Tectonic Reorganizations

    Science.gov (United States)

    Morra, G.; Quevedo, L.; Butterworth, N.; Matthews, K. J.; Müller, D.

    2010-12-01

    We use a new numerical approach for global geodynamics to investigate the origin of present global plate motion and to identify the causes of the last two global tectonic reorganizations occurred about 50 and 100 million years ago (Ma) [1]. While the 50 Ma event is the most well-known global plate-mantle event, expressed by the bend in the Hawaiian-Emperor volcanic chain, a prominent plate reorganization at about 100 Ma, although presently little studied, is clearly indicated by a major bend in the fracture zones in the Indian Ocean and by a change in Pacific plate motion [2]. Our workflow involves turning plate reconstructions into surface meshes that are subsequently employed as initial conditions for global Boundary Element numerical models. The tectonic setting that anticipates the reorganizations is processed with the software GPlates, combining the 3D mesh of the paleo-plate morphology and the reconstruction of paleo-subducted slabs, elaborated from tectonic history [3]. All our models involve the entire planetary system, are fully dynamic, have free surface, are characterized by a spectacular computational speed due to the simultaneous use of the multi-pole algorithm and the Boundary Element formulation and are limited only by the use of sharp material property variations [4]. We employ this new tool to unravel the causes of plate tectonic reorganizations, producing and comparing global plate motion with the reconstructed ones. References: [1] Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, VOL. 46, RG3004, 44 PP., 2008 [2] Wessel, P. and Kroenke, L.W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research, Vol 113, B06101, 2008 [3] L. Quevedo, G. Morra, R. D. Mueller. Parallel Fast Multipole Boundary Element Method for Crustal Dynamics, Proceeding 9th World Congress and 4th Asian

  2. Tectonic History and Deep Structure of the Demerara Plateau from Combined Wide-Angle and Reflection Seismic Data and Plate Kinematic Reconstructions

    Science.gov (United States)

    Klingelhoefer, F.; Museur, T.; Roest, W. R.; Graindorge, D.; Chauvet, F.; Loncke, L.; Basile, C.; Poetisi, E.; Deverchere, J.; Lebrun, J. F.; Perrot, J.; Heuret, A.

    2017-12-01

    Many transform margins have associated intermediate depth marginal plateaus, which are commonly located between two oceanic basins. The Demerara plateau is located offshore Surinam and French Guiana. Plate kinematic reconstructions show that the plateau is located between the central and equatorial Atlantic in a position conjugate to the Guinean Plateau. In the fall of 2016, the MARGATS cruise acquired geophysical data along the 400 km wide Demerara plateau. The main objective of the cruise was to image the deep structure of the Demerara plateau and to study its tectonic history. A set of 4 combined wide-angle and reflection seismic profiles was acquired along the plateau, using 80 ocean-bottom seismometers, a 3 km long seismic streamer and a 8000 cu inch tuned airgun array. Forward modelling of the wide-angle seismic data on a profile, located in the eastern part of the plateau and oriented in a NE-SW direction, images the crustal structure of the plateau, the transition zone and the neighbouring crust of oceanic origin, up to a depth of 40 km. The plateau itself is characterised by a crust of 30 km thickness, subdivided into three distinct layers. However, the velocities and velocity gradients do not fit typical continental crust, with a lower crustal layer showing untypically high velocities and an upper layer having a steep velocity gradient. From this model we propose that the lowermost layer is probably formed from volcanic underplated material and that the upper crustal layer likely consists of the corresponding extrusive volcanic material, forming thick seaward-dipping reflector sequences on the plateau. A basement high is imaged at the foot of the slope and forms the ocean-continent transition zone. Further oceanward, a 5-6 km thick crust is imaged with velocities and velocity gradients corresponding to a thin oceanic crust. A compilation of magnetic data from the MARGATS and 3 previous cruises shows a high amplitude magnetic anomaly along the northern

  3. History and Evolution of Precambrian plate tectonics

    Science.gov (United States)

    Fischer, Ria; Gerya, Taras

    2014-05-01

    Plate tectonics is a global self-organising process driven by negative buoyancy at thermal boundary layers. Phanerozoic plate tectonics with its typical subduction and orogeny is relatively well understood and can be traced back in the geological records of the continents. Interpretations of geological, petrological and geochemical observations from Proterozoic and Archean orogenic belts however (e.g., Brown, 2006), suggest a different tectonic regime in the Precambrian. Due to higher radioactive heat production the Precambrian lithosphere shows lower internal strength and is strongly weakened by percolating melts. The fundamental difference between Precambrian and Phanerozoic tectonics is therefore the upper-mantle temperature, which determines the strength of the upper mantle (Brun, 2002) and the further tectonic history. 3D petrological-thermomechanical numerical modelling experiments of oceanic subduction at an active plate at different upper-mantle temperatures show these different subduction regimes. For upper-mantle temperatures 250 K above the present day value no subduction occurs any more. The whole lithosphere is delaminating and due to strong volcanism and formation of a thicker crust subduction is inhibited. This stage of 200-250 K higher upper mantle temperature which corresponds roughly to the early Archean (Abbott, 1994) is marked by strong volcanism due to sublithospheric decompression melting which leads to an equal thickness for both oceanic and continental plates. As a consequence subduction is inhibited, but a compressional setup instead will lead to orogeny between a continental or felsic terrain and an oceanic or mafic terrain as well as internal crustal convection. Small-scale convection with plume shaped cold downwellings also in the upper mantle is of increased importance compared to the large-scale subduction cycle observed for present temperature conditions. It is also observed that lithospheric downwellings may initiate subduction by

  4. Is plate tectonics needed to evolve technological species on exoplanets?

    Directory of Open Access Journals (Sweden)

    Robert J. Stern

    2016-07-01

    Full Text Available As we continue searching for exoplanets, we wonder if life and technological species capable of communicating with us exists on any of them. As geoscientists, we can also wonder how important is the presence or absence of plate tectonics for the evolution of technological species. This essay considers this question, focusing on tectonically active rocky (silicate planets, like Earth, Venus, and Mars. The development of technological species on Earth provides key insights for understanding evolution on exoplanets, including the likely role that plate tectonics may play. An Earth-sized silicate planet is likely to experience several tectonic styles over its lifetime, as it cools and its lithosphere thickens, strengthens, and becomes denser. These include magma ocean, various styles of stagnant lid, and perhaps plate tectonics. Abundant liquid water favors both life and plate tectonics. Ocean is required for early evolution of diverse single-celled organisms, then colonies of cells which specialized further to form guts, appendages, and sensory organisms up to the complexity of fish (central nervous system, appendages, eyes. Large expanses of dry land also begin in the ocean, today produced above subduction zones in juvenile arcs and by their coalescence to form continents, although it is not clear that plate tectonics was required to create continental crust on Earth. Dry land of continents is required for further evolution of technological species, where modification of appendages for grasping and manipulating, and improvement of eyes and central nervous system could be perfected. These bioassets allowed intelligent creatures to examine the night sky and wonder, the beginning of abstract thinking, including religion and science. Technology arises from the exigencies of daily living such as tool-making, agriculture, clothing, and weapons, but the pace of innovation accelerates once it is allied with science. Finally, the importance of plate

  5. Plate tectonics and planetary habitability: current status and future challenges.

    Science.gov (United States)

    Korenaga, Jun

    2012-07-01

    Plate tectonics is one of the major factors affecting the potential habitability of a terrestrial planet. The physics of plate tectonics is, however, still far from being complete, leading to considerable uncertainty when discussing planetary habitability. Here, I summarize recent developments on the evolution of plate tectonics on Earth, which suggest a radically new view on Earth dynamics: convection in the mantle has been speeding up despite its secular cooling, and the operation of plate tectonics has been facilitated throughout Earth's history by the gradual subduction of water into an initially dry mantle. The role of plate tectonics in planetary habitability through its influence on atmospheric evolution is still difficult to quantify, and, to this end, it will be vital to better understand a coupled core-mantle-atmosphere system in the context of solar system evolution. © 2012 New York Academy of Sciences.

  6. Oil prospection using the tectonic plate model

    Science.gov (United States)

    Pointu, Agnès

    2015-04-01

    Tectonic plate models are an intellectual setting to understand why oil deposits are so uncommon and unequally distributed and how models can be used in actual oil and gas prospection. In this case, we use the example of the Ghawar deposit (Saudi Arabia), one of the largest producing well in the world. In the first step, physical properties of rocks composing the oil accumulation are studied by laboratory experiments. Students estimate the porosity of limestone and clay by comparing their mass before and after water impregnation. Results are compared to microscopic observations. Thus, students come to the conclusion that oil accumulations are characterized by superposition of rocks with very different properties: a rich organic source rock (clays of the Hanifa formation), a porous reservoir rock to store the petroleum in (limestones of the Arab formation) and above an impermeable rock with very low porosity (evaporites of the Tithonien). In previous lessons, students have seen that organic matter is usually mineralized by bacteria and that this preservation requires particular conditions. The aim is to explain why biomass production has been so important during the deposit of the clays of the Hanifa formation. Tectonic plate models make it possible to estimate the location of the Arabian Peninsula during Jurassic times (age of Hanifa formation). In order to understand why the paleo-location of the Arabian Peninsula is important to preserve organic matter, students have different documents showing: - That primary production of biomass by phytoplankton is favored by climatic conditions, - That the position of continents determinate the ocean currents and the positions of upwelling zones and zones where organic matter will be able to be preserved, - That north of the peninsula there was a passive margin during Jurassic times. An actual seismic line is studied in order to highlight that this extensive area allowed thick sedimentary deposits to accumulate and that fast

  7. Looking for Plate Tectonics in all the wrong fluids

    Science.gov (United States)

    Davaille, Anne

    2017-04-01

    Ever since the theory of Plate Tectonics in the 1960's, the dream of the geomodeler has been to generate plate tectonics self-consistently from thermal convection in the laboratory. By selfconsistenly, I mean that the configuration of the plate boundaries is in no way specified a priori, so that the plates develop and are wholly consumed without intervention from the modeler. The reciepe is simple : put a well-chosen fluid in a fishtank heated from below and cooled from above, wait and see. But the « well-chosen » is the difficult part... and the interesting one. Plate tectonics is occuring on Earth because of the characteristics of the lithosphere rheology. The latter are complex to estimate as they depend on temperature, pressure, phase, water content, chemistry, strain rate, memory and scale. As a result, the ingredients necessary for plate tectonics are still debated, and it would be useful to find an analog fluid who could reproduce plate tectonics in the laboratory. I have therefore spent the last 25 years to try out fluids, and I shall present a number of failures to generate plate tectonics using polymers, colloids, ketchup, milk, chocolate, sugar, oils. To understand why they failed is important to narrow down the « well-chosen » fluid.

  8. Petroleum and natural gas geology and plate tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, B.

    1984-01-01

    Several processes of oil and gas geology are studied in connection with plate-tectonical processes. Thus it becomes clear, that there is a distinct difference between the Paleozoic development of the European plate and the Mesozoic development. One can state, that the Paleozoic development is essentially influenced by the positions of the mobile belts and the cratonized parts of the plates. The development during Meso-Caenozoic is mainly characterized by crustal processes in the result of the disintegration of Pangaea.

  9. A combined rigid/deformable plate tectonic model for the evolution of the Indian Ocean

    Science.gov (United States)

    Watson, J. G.; Glover, C. T.; Adriasola Munoz, A. C.; Harris, J. P.; Goodrich, M.

    2012-04-01

    Plate tectonic reconstructions are essential for placing geological information in its correct spatial context, understanding depositional environments, defining basin dimensions and evolution, and serve as a basis for palaeogeographic mapping and for palaeo-climate modelling. Traditional 'rigid' plate reconstructions often result in misfits (overlaps and underfits) in the geometries of juxtaposed plate margins when restored to their pre-rift positions. This has been attributed to internal deformation pre- and/or syn- continental break-up. Poorly defined continent-ocean boundaries add to these problems. To date, few studies have integrated continental extension within a global model. Recent plate tectonic reconstructions based on the relative motions of Africa, Madagascar, India and Antarctica during the break-up of eastern Gondwana have not taken into account the effects of deformation; particularly between India and Madagascar, and India and the Seychelles. A deformable plate model is in development that builds on the current rigid plate model to describe the complex multiphase break-up history between Africa, Madagascar, Seychelles and India, the associated magmatic activity and subsequent India/Eurasia collision. The break-up of eastern Gondwana occurred in the mid Jurassic by rifting between Africa and the India-Madagascar-Australian-Antarctica plates, followed by the Late Jurassic drift of India away from Australia and the Cretaceous break-up of Australia and Antarctica. The northwards drift of the Seychelles-India block in the Tertiary was accommodated by the opening of the Laxmi Basin. This was followed by the eruption of the extensive Deccan flood basalts and the separation of India and the Seychelles. Crustal domains on volcanic margins can be very difficult to define due to the accretion of magmatic material. On these margins, there is much speculation on the position of the continent-ocean boundary and the timing of rifting and sea-floor spreading. The

  10. Plate tectonic regulation of global marine animal diversity

    Science.gov (United States)

    Zaffos, Andrew; Finnegan, Seth; Peters, Shanan E.

    2017-05-01

    Valentine and Moores [Valentine JW, Moores EM (1970) Nature 228:657-659] hypothesized that plate tectonics regulates global biodiversity by changing the geographic arrangement of continental crust, but the data required to fully test the hypothesis were not available. Here, we use a global database of marine animal fossil occurrences and a paleogeographic reconstruction model to test the hypothesis that temporal patterns of continental fragmentation have impacted global Phanerozoic biodiversity. We find a positive correlation between global marine invertebrate genus richness and an independently derived quantitative index describing the fragmentation of continental crust during supercontinental coalescence-breakup cycles. The observed positive correlation between global biodiversity and continental fragmentation is not readily attributable to commonly cited vagaries of the fossil record, including changing quantities of marine rock or time-variable sampling effort. Because many different environmental and biotic factors may covary with changes in the geographic arrangement of continental crust, it is difficult to identify a specific causal mechanism. However, cross-correlation indicates that the state of continental fragmentation at a given time is positively correlated with the state of global biodiversity for tens of millions of years afterward. There is also evidence to suggest that continental fragmentation promotes increasing marine richness, but that coalescence alone has only a small negative or stabilizing effect. Together, these results suggest that continental fragmentation, particularly during the Mesozoic breakup of the supercontinent Pangaea, has exerted a first-order control on the long-term trajectory of Phanerozoic marine animal diversity.

  11. A Plate Tectonic Model for the Neoproterozoic with Evolving Plate Boundaries

    Science.gov (United States)

    Merdith, Andrew; Collins, Alan; Williams, Simon; Pisarevsky, Sergei; Müller, Dietmar

    2017-04-01

    The Neoproterozoic was dominated by the formation of the supercontinent Rodinia, its break-up and the subsequent amalgamation of Gondwana, during which, the planet experienced large climatic variations and the emergence of complex life. Here we present a topological plate model of the Neoproterozoic based on a synthesis of available geological and palaeomagnetic data. Subduction zones, which are well preserved in the geological record, are used as a proxy for convergent margins; evidence for mid-ocean ridges and transform motion is less clearly preserved, though passive margins are used as a proxy for spreading centres, and evidence for strike-slip motions are used to model transform boundaries. We find that the model presented here only predicts 70% of the total length of subduction active today, though it models similar lengths of both transform and divergent boundaries, suggesting that we have produced a conservative model and are probably underestimating the amount of subduction. Where evidence for convergent, divergent or transform motion is not preserved, we interpret the locations of plate boundaries based on the relative motions of cratonic crust as suggested through either palaeomagnetic data or the geological record. Using GPlates, we tie these boundaries together to generate a plate model that depicts the motion of tectonic plates through the Neoproterozoic. We omit India and South China from Rodinia completely, due to long-lived subduction preserved on margins of India and conflicting palaeomagnetic data for the Cryogenian, but tie them together due to similar Tonian aged accretionary patterns along their respective (present-day) north-western and northern margins, such that these two cratons act as a "lonely wanderer" for much of the Neoproterozoic, and form their own tectonic plate. We also introduce a Tonian-Cryogenian aged rotation of the Congo-São Francisco Craton relative to Rodinia to better fit palaeomagnetic data and account for thick passive

  12. Gondwana Tales: an inquiry approach to plate tectonics

    Science.gov (United States)

    Domènech Casal, Jordi

    2014-05-01

    Plate tectonics and its effects on the constitution of seas and continents are key models in science education. Fossil evidences are usually taught in demostrative key when Wegener's discoverings about Pangea are introduced. In order to introduce inquiry-based science education (IBSE) approaches to this topic, we propose "Gondwana Tales", an activity where students are asked to use fossil data to reconstruct the geologic history of an imaginary planet. Grouped in independent teams, each team is furnished with stratigraphic columns from several sites containing faunistic successions of real organisms existing in the past in Earth. Students are told to reconstruct a model of the evolution of the continents, by making calculations of relative ages of the fossils, and relating each fossil to a geologic era. The different teams have incomplete and complementary information. After a first step where they have to propose a partial model based on incomplete data, each team receives a "visitor scientist" from another team, this implying an informal scientific communication event. This process is performed several times, engaging a discussion in each team and getting a final consensus model created by the whole class. Correct answer is not given to the students, even at the end of the activity, to keep the activity under the parameters of real scientific experience, where there is not a "correct answer" to compare. Instead of this, and following the IBSE standards, a reflection on the process is proposed to students. The lack of complete information and the need to collaborate are part of classroom dynamics focused to the understanding of the process of creation of the scientific knowledge. This activity is part of the C3 Project on Creation of Scientific Knowledge that is being applied in the school.

  13. The magma ocean as an impediment to lunar plate tectonics

    Science.gov (United States)

    Warren, Paul H.

    1993-01-01

    The primary impediment to plate tectonics on the moon was probably the great thickness of its crust and particularly its high crust/lithosphere thickness ratio. This in turn can be attributed to the preponderance of low-density feldspar over all other Al-compatible phases in the lunar interior. During the magma ocean epoch, the moon's crust/lithosphere thickness ratio was at the maximum theoretical value, approximately 1, and it remained high for a long time afterwards. A few large regions of thin crust were produced by basin-scale cratering approximately contemporaneous with the demise of the magma ocean. However, these regions probably also tend to have uncommonly thin lithosphere, since they were directly heated and indirectly enriched in K, Th, and U by the same cratering process. Thus, plate tectonics on the moon in the form of systematic lithosphere subduction was impeded by the magma ocean.

  14. Is Active Tectonics on Madagascar Consistent with Somalian Plate Kinematics?

    Science.gov (United States)

    Stamps, D. S.; Kreemer, C.; Rajaonarison, T. A.

    2017-12-01

    The East African Rift System (EARS) actively breaks apart the Nubian and Somalian tectonic plates. Madagascar finds itself at the easternmost boundary of the EARS, between the Rovuma block, Lwandle plate, and the Somalian plate. Earthquake focal mechanisms and N-S oriented fault structures on the continental island suggest that Madagascar is experiencing east-west oriented extension. However, some previous plate kinematic studies indicate minor compressional strains across Madagascar. This inconsistency may be due to uncertainties in Somalian plate rotation. Past estimates of the rotation of the Somalian plate suffered from a poor coverage of GPS stations, but some important new stations are now available for a re-evaluation. In this work, we revise the kinematics of the Somalian plate. We first calculate a new GPS velocity solution and perform block kinematic modeling to evaluate the Somalian plate rotation. We then estimate new Somalia-Rovuma and Somalia-Lwandle relative motions across Madagascar and evaluate whether they are consistent with GPS measurements made on the island itself, as well as with other kinematic indicators.

  15. Learning Plate Tectonics Using a Pre-Analogy Step

    Science.gov (United States)

    Glesener, G. B.; Sandoval, W. A.

    2011-12-01

    Previous research has shown that children tend to demonstrate lower performance on analogical reasoning tasks at a causal relations level compared to most adults (Gentner & Toupin, 1986). This tendency is an obstacle that geoscience educators must overcome because of the high frequency of analogies used in geoscience pedagogy. In particular, analog models are used to convey complex systems of non-everyday/non-observable events found in nature, such as plate tectonics. Key factors in successful analogical reasoning that have been suggested by researchers include knowledge of the causal relations in the base analog (Brown & Kane, 1988; Gentner, 1988; Gentner & Toupin, 1986), and development of learning strategies and metaconceptual competence(Brown & Kane, 1988). External factors, such as guiding cues and hints have been useful cognitive supports that help students reason through analogical problems (Gick & Holyoak, 1980). Cognitive supports have been seen by researchers to decrease processing demands on retrieval and working memory (Richland, Zur, & Holyoak, 2007). We observed third and fourth graders learning about plate tectonics beginning with a pre-analogy step-a cognitive support activity a student can do before working with an analogy to understand the target. This activity was designed to aid students in developing their understanding of object attributes and relations within an analog model so that more focus can be placed on mapping the corresponding higher-order relations between the base and target. Students learned targeted concepts of plate tectonics, as measured by pre to post gains on items adapted from the Geosciences Concept Inventory. Analyses of classroom interaction showed that students used the object attributes and higher-order relations highlighted in the pre-analogy activity as resources to reason about plate boundaries and plate movement during earthquakes.

  16. The San Andreas fault experiment. [gross tectonic plates relative velocity

    Science.gov (United States)

    Smith, D. E.; Vonbun, F. O.

    1973-01-01

    A plan was developed during 1971 to determine gross tectonic plate motions along the San Andreas Fault System in California. Knowledge of the gross motion along the total fault system is an essential component in the construction of realistic deformation models of fault regions. Such mathematical models will be used in the future for studies which will eventually lead to prediction of major earthquakes. The main purpose of the experiment described is the determination of the relative velocity of the North American and the Pacific Plates. This motion being so extremely small, cannot be measured directly but can be deduced from distance measurements between points on opposite sites of the plate boundary taken over a number of years.

  17. Ore-lead isotopes and Grenville plate tectonics

    International Nuclear Information System (INIS)

    Farquhar, R.M.; Fletcher, I.R.

    1980-01-01

    Recent advances in the 'whole earth' modelling of evolutionary processes of Pb isotopes shed light upon the origin of the metals found in various types of ore deposits. On the bases of these models and several recently published data sets, we believe that the ore deposits formed in various plate tectonic environments may carry 'isotopic fingerprints' which, when used with other characteristics such as mineral assemblages, may identify the depositional environments of many ore bodies. In the present study Pb-isotopic measurements have been made of a number of Precambrain mineralization types and localities throughout the Central Metasedimentary Belt of the Grenville Province. The data for individual deposits are at best ambiguous, but fall into two groups sufficiently distinctive to allow some degree of 'fingerprint' identification. Comparisons with data from other areas suggest that the major periods of sedimentation within the Central Metasedimentary Belt accompanied plate rifting and/or island arc tectonic activity, with most of the mineralized lead being derived from mantle sources. Detailed comparisons between the Grenville and other regions are uncertain, mainly because there are few detailed high-accuracy data sets from younger, tectonically unambiguous mineral occurrences. We suggest that once these data sets are availble, isotopic fingerprinting may become diagnostic for deposits ranging well back into the Precambrain

  18. Transoceanic Dispersal and Plate Tectonics Shaped Global Cockroach Distributions: Evidence from Mitochondrial Phylogenomics.

    Science.gov (United States)

    Bourguignon, Thomas; Tang, Qian; Ho, Simon Y W; Juna, Frantisek; Wang, Zongqing; Arab, Daej A; Cameron, Stephen L; Walker, James; Rentz, David; Evans, Theodore A; Lo, Nathan

    2017-04-01

    Following the acceptance of plate tectonics theory in the latter half of the 20th century, vicariance became the dominant explanation for the distributions of many plant and animal groups. In recent years, however, molecular-clock analyses have challenged a number of well-accepted hypotheses of vicariance. As a widespread group of insects with a fossil record dating back 300 My, cockroaches provide an ideal model for testing hypotheses of vicariance through plate tectonics versus transoceanic dispersal. However, their evolutionary history remains poorly understood, in part due to unresolved relationships among the nine recognized families. Here, we present a phylogenetic estimate of all extant cockroach families, as well as a timescale for their evolution, based on the complete mitochondrial genomes of 119 cockroach species. Divergence dating analyses indicated that the last common ancestor of all extant cockroaches appeared ∼235 Ma, ∼95 My prior to the appearance of fossils that can be assigned to extant families, and before the breakup of Pangaea began. We reconstructed the geographic ranges of ancestral cockroaches and found tentative support for vicariance through plate tectonics within and between several major lineages. We also found evidence of transoceanic dispersal in lineages found across the Australian, Indo-Malayan, African, and Madagascan regions. Our analyses provide evidence that both vicariance and dispersal have played important roles in shaping the distribution and diversity of these insects.

  19. The Biggest Plates on Earth. Submarine Ring of Fire--Grades 5-6. Plate Tectonics.

    Science.gov (United States)

    National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

    This activity is designed to teach how tectonic plates move, what some consequences of this motion are, and how magnetic anomalies document the motion at spreading centers do. The activity provides learning objectives, a list of needed materials, key vocabulary words, background information, day-to-day procedures, internet connections, career…

  20. Seismic gaps and plate tectonics: seismic potential for major boundaries

    Energy Technology Data Exchange (ETDEWEB)

    McCann, W R; Nishenko, S P; Sykes, L R; Krause, J

    1979-01-01

    The theory of plate tectonics provides a basic framework for evaluating the potential for future great earthquakes to occur along major plate boundaries. Along most of the transform and convergent plate boundaries considered in this paper, the majority of seismic slip occurs during large earthquakes, i.e., those of magnitude 7 or greater. The concepts that rupture zones, as delineated by aftershocks, tend to abut rather than overlap, and large events occur in regions with histories of both long-and short-term seismic quiescence are used in this paper to delineate major seismic gaps. The term seismic gap is taken to refer to any region along an active plate boundary that has not experienced a large thrust or strike-slip earthquake for more than 30 years. A region of high seismic potential is a seismic gap that, for historic or tectonic reasons, is considered likely to produce a large shock during the next few decades. The seismic gap technique provides estimates of the location, size of future events and origin time to within a few tens of years at best. The accompanying map summarizes six categories of seismic potential for major plate boundaries in and around the margins of the Pacific Ocean and the Caribbean, South Sandwich and Sunda (Indonesia) regions for the next few decades. These six categories are meant to be interpreted as forecasts of the location and size of future large shocks and should not be considered to be predictions in which a precise estimate of the time of occurrence is specified. The categories of potential assigned here provide a rationale for assigning priorities for instrumentation, for future studies aimed at predicting large earthquakes and for making estimates of tsunami potential.

  1. Subduction and Plate Edge Tectonics in the Southern Caribbean

    Science.gov (United States)

    Levander, A.; Schmitz, M.; Niu, F.; Bezada, M. J.; Miller, M. S.; Masy, J.; Ave Lallemant, H. G.; Pindell, J. L.; Bolivar Working Group

    2013-05-01

    The southern Caribbean plate boundary consists of a subduction zone at at either end of a complex strike-slip fault system: In the east at the Lesser Antilles subduction zone, the Atlantic part of the South American plate subducts beneath the Caribbean. In the north and west in the Colombia basin, the Caribbean subducts under South America. In a manner of speaking, the two plates subduct beneath each other. Finite-frequency teleseismic P-wave tomography confirms this, imaging the Atlantic and the Caribbean plates subducting steeply in opposite directions to transition zone depths under northern South America (Bezada et al, 2010). The two subduction zones are connected by the El Pilar-San Sebastian strike-slip fault system, a San Andreas scale system that has been cut off at the Bocono fault, the southeastern boundary fault of the Maracaibo block. A variety of seismic probes identify subduction features at either end of the system (Niu et al, 2007; Clark et al., 2008; Miller et al. 2009; Growdon et al., 2009; Huang et al., 2010; Masy et al, 2011). The El Pilar system forms at the southeastern corner of the Antilles subduction zone with the Atlantic plate tearing from South America. The deforming plate edges control mountain building and basin formation at the eastern end of the strike-slip system. Tearing the Atlantic plate from the rest of South America appears to cause further lithospheric instability continentward. In northwestern South America the Caribbean plate very likely also tears, as its southernmost element subducts at shallow angles under northernmost Colombia but then rapidly descends to the transition zone under Lake Maracaibo (Bezada et al., 2010). We believe that the flat slab controls the tectonics of the Neogene Merida Andes, Perija, and Santa Marta ranges. The nonsubducting part of the Caribbean plate also underthrusts northern Venezuela to about the width of the coastal mountains (Miller et al., 2009). We infer that the edge of the underthrust

  2. Scaling of Convection and Plate Tectonics in Super-Earths

    Science.gov (United States)

    Valencia, D. C.; O'Connell, R. J.; Sasselov, D. D.

    2006-12-01

    The discovery of three Super-Earths around different stars, possible only in the last year, prompts us to study the characteristics of our planet within a general context. The Earth, being the most massive terrestrial object in the solar system is the only planet that exhibits plate tectonics. We think this might not be a coincidence and explore the role that mass plays in determining the mode of convection. We use the scaling of convective vigor with Rayleigh number commonly used in parameterized convection. We study how the parameters controlling convection: Rayleigh number (Ra), boundary layer thickness (δ), internal temperature (T_i) and convective velocities (u) scale with mass. This is possible from the scaling of heat flux, mantle density, size and gravity with mass which we reported in Valencia, et. al 2006. The extrapolation to massive rocky planets is done from our knowledge of the Earth. Even though uncertainties arise from extrapolation and assumptions are needed we consider this simple scaling to be a first adequate step. As the mass of a planet increases, Ra increases, yielding a decrease in δ and an increase in u, while T_i increases very slightly. This is true for an isoviscous case and is more accentuated in a temperature dependent viscosity scenario. In a planet with vigorous convection (high u), a thin lithosphere (low δ) is easier to subduct and hence, initiate plate tectonics. The lithosphere also has to be dense enough (cold and thick) to have the bouyancy necessary for subduction. We calculate that a convective cycle for an isoviscous planet is τ ~ M^{-0.3} considering whole mantle convection. Meaning that if these planets have continents, the timescale for continental rearrangement is shorter (about half the Earth's for a 5 earth-mass planet). Additionally, we explore the negative feedback cycle between convection and temperature dependent viscosity and estimate a timescale for this effect.

  3. Global Ocean Sedimentation Patterns: Plate Tectonic History Versus Climate Change

    Science.gov (United States)

    Goswami, A.; Reynolds, E.; Olson, P.; Hinnov, L. A.; Gnanadesikan, A.

    2014-12-01

    Global sediment data (Whittaker et al., 2013) and carbonate content data (Archer, 1996) allows examination of ocean sedimentation evolution with respect to age of the underlying ocean crust (Müller et al., 2008). From these data, we construct time series of ocean sediment thickness and carbonate deposition rate for the Atlantic, Pacific, and Indian ocean basins for the past 120 Ma. These time series are unique to each basin and reflect an integrated response to plate tectonics and climate change. The goal is to parameterize ocean sedimentation tied to crustal age for paleoclimate studies. For each basin, total sediment thickness and carbonate deposition rate from 0.1 x 0.1 degree cells are binned according to basement crustal age; area-corrected moments (mean, variance, etc.) are calculated for each bin. Segmented linear fits identify trends in present-day carbonate deposition rates and changes in ocean sedimentation from 0 to 120 Ma. In the North and South Atlantic and Indian oceans, mean sediment thickness versus crustal age is well represented by three linear segments, with the slope of each segment increasing with increasing crustal age. However, the transition age between linear segments varies among the three basins. In contrast, mean sediment thickness in the North and South Pacific oceans are numerically smaller and well represented by two linear segments with slopes that decrease with increasing crustal age. These opposing trends are more consistent with the plate tectonic history of each basin being the controlling factor in sedimentation rates, rather than climate change. Unlike total sediment thickness, carbonate deposition rates decrease smoothly with crustal age in all basins, with the primary controls being ocean chemistry and water column depth.References: Archer, D., 1996, Global Biogeochem. Cycles 10, 159-174.Müller, R.D., et al., 2008, Science, 319, 1357-1362.Whittaker, J., et al., 2013, Geochem., Geophys., Geosyst. DOI: 10.1002/ggge.20181

  4. On the relative significance of lithospheric weakening mechanisms for sustained plate tectonics

    Science.gov (United States)

    Araceli Sanchez-Maes, Sophia

    2018-01-01

    Plate tectonics requires the bending of strong plates at subduction zones, which is difficult to achieve without a secondary weakening mechanism. Two classes of weakening mechanisms have been proposed for the generation of ongoing plate tectonics, distinguished by whether or not they require water. Here we show that the energy budget of global subduction zones offers a simple yet decisive test on their relative significance. Theoretical studies of mantle convection suggest bending dissipation to occupy only 10-20 % of total dissipation in the mantle, and our results indicate that the hydrous mechanism in the shallow part of plates is essential to satisfy the requirement. Thus, surface oceans are required for the long-term operation of plate tectonics on terrestrial worlds. Establishing this necessary and observable condition for sustained plate tectonics carries important implications for planetary habitability at large.

  5. Plate tectonic influences on Earth's baseline climate: a 2 billion-year record

    Science.gov (United States)

    McKenzie, R.; Evans, D. A.; Eglington, B. M.; Planavsky, N.

    2017-12-01

    Plate tectonic processes present strong influences on the long-term carbon cycle, and thus global climate. Here we utilize multiple aspects of the geologic record to assess the role plate tectonics has played in driving major icehouse­-greenhouse transitions for the past 2 billion years. Refined paleogeographic reconstructions allow us to quantitatively assess the area of continents in various latitudinal belts throughout this interval. From these data we are able to test the hypothesis that concentrating continental masses in low-latitudes will drive cooler climates due to increased silicate weathering. We further superimpose records of events that are believed to increase the `weatherability' of the crust, such as large igneous province emplacement, island-arc accretion, and continental collisional belts. Climatic records are then compared with global detrital zircon U-Pb age data as a proxy for continental magmatism. Our results show a consistent relationship between zircon-generating magmatism and icehouse-greenhouse transitions for > 2 billion years, whereas paleogeographic records show no clear consistent relationship between continental configurations and prominent climate transitions. Volcanic outgassing appears to exert a first-order control on major baseline climatic shifts; however, paleogeography likely plays an important role in the magnitude of this change. Notably, climatic extremes, such as the Cryogenian icehouse, occur during a combination of reduce volcanism and end-member concentrations of low-latitudinal continents.

  6. The Rapid Drift of the Indian Tectonic Plate

    Science.gov (United States)

    Kumar, P.; Yuan, X.; Kumar, R.; Kind, R.; Li, X.; Chadha, R.

    2007-12-01

    The breakup of the supercontinent Gondwanaland into Africa, Antarctica, Australia and India about 140 million years ago and consequently the opening of the Indian Ocean was caused by heating of the lithosphere from below by a large plume whose relicts are the Marion, Kerguelen and Reunion plumes. Plate reconstructions based on paleomagnetic data suggest that the Indian plate attained a very high speed (18-20 cm/yr during late Cretaceous) subsequent to its breakup from the Gondwanaland and slowed down to ~5 cm/yr since the continental collision with Asia during the last ~50 Ma. The Australian and African plates moved comparatively lesser distances and at much lesser speed of 2-4 cm/yr. Antarctica remained almost stationary. This super mobility makes India unique compared to the other fragments of Gondwanaland. We propose that when the parts of Gondwanaland were separated by the plume, the penetration of their lithospheric roots into the asthenosphere played an important role in determining their speed. We estimated the thickness of the lithospheric plates of the different parts of Gondwanaland around the Indian Ocean using the S-receiver function technique. We found that the part of Gondwanaland with clearly the thinnest lithosphere has travelled with the highest speed - India. The lithospheric root in South Africa, Australia and Antarctica is between 180 and 300 km deep. The Indian lithosphere is in contrast only about 100 km thick. Our interpretation is that the plume that partitioned Gondwanaland has also melted the lower half of the Indian lithosphere thus permitting faster motion due to the ridge push or slab pull.

  7. Linking plate reconstructions with deforming lithosphere to geodynamic models

    Science.gov (United States)

    Müller, R. D.; Gurnis, M.; Flament, N.; Seton, M.; Spasojevic, S.; Williams, S.; Zahirovic, S.

    2011-12-01

    While global computational models are rapidly advancing in terms of their capabilities, there is an increasing need for assimilating observations into these models and/or ground-truthing model outputs. The open-source and platform independent GPlates software fills this gap. It was originally conceived as a tool to interactively visualize and manipulate classical rigid plate reconstructions and represent them as time-dependent topological networks of editable plate boundaries. The user can export time-dependent plate velocity meshes that can be used either to define initial surface boundary conditions for geodynamic models or alternatively impose plate motions throughout a geodynamic model run. However, tectonic plates are not rigid, and neglecting plate deformation, especially that of the edges of overriding plates, can result in significant misplacing of plate boundaries through time. A new, substantially re-engineered version of GPlates is now being developed that allows an embedding of deforming plates into topological plate boundary networks. We use geophysical and geological data to define the limit between rigid and deforming areas, and the deformation history of non-rigid blocks. The velocity field predicted by these reconstructions can then be used as a time-dependent surface boundary condition in regional or global 3-D geodynamic models, or alternatively as an initial boundary condition for a particular plate configuration at a given time. For time-dependent models with imposed plate motions (e.g. using CitcomS) we incorporate the continental lithosphere by embedding compositionally distinct crust and continental lithosphere within the thermal lithosphere. We define three isostatic columns of different thickness and buoyancy based on the tectonothermal age of the continents: Archean, Proterozoic and Phanerozoic. In the fourth isostatic column, the oceans, the thickness of the thermal lithosphere is assimilated using a half-space cooling model. We also

  8. The Earth's Mantle Is Solid: Teachers' Misconceptions About the Earth and Plate Tectonics.

    Science.gov (United States)

    King, Chris

    2000-01-01

    Discusses the misconceptions revealed by the teachers' answers and outlines more accurate answers and explanations based on established evidence and uses these to provide a more complete understanding of plate tectonic process and the structure of Earth. (Author/YDS)

  9. Feeling and Understanding Plate Tectonics - How can We attract Museum Visitors Attention?

    Science.gov (United States)

    Simon, Gilla; Apel, Michael

    2017-04-01

    Earthquakes, volcano eruptions and other natural hazards are commonly paid attention to, if news about disastrous events reach us. The mission of an Earth Science or Natural History Museum, however, goes beyond explaining the causes of natural disasters, but should also present science history and cutting edge research. Since dealing with a subject, especially with one, which seems to be in the abstract, is more effective, we realised two new projects where our visitors can feel and understand plate tectonics in a more exciting way. In 2015 we installed an earthquake simulator in our permanent exhibition to allow our visitors the physical experience of an earthquake. Because of static restrictions the simulator is housed in a container outside the building where it can be visited as a booked program upon prior reservation or by joining public tours on Sundays and special occasions. The simulation of six real earthquakes in two spatial directions is accompanied by a movie presenting facts about the earthquake itself (e.g. location, magnitude, damage and victims), but also general information about plate tectonics. This standard program takes about 20 minutes. During an educational program, however, not only the simulator is visited, but also the permanent exhibition, where the guide can focus on different aspects and then might choose specific earthquakes and information blocs in the simulator. In addition workshops with experiments are offered for school classes and other groups. This allows us to offer an individual program fitting to the visitor group. In 2016 we converted an old movie room to a state of the art media room. In cooperation with Media Informatics students we developed a quiz for three different levels and various themes like earthquakes, volcanoes, history and plate tectonics in general. Starting the quiz, a virtual earthquake destroys a building which will be reconstructed if the participants answer multiple choice questions correctly. Though, the

  10. Plate tectonics, mantle convection and D'' seismic structures

    Science.gov (United States)

    Wen, Lianxing

    This thesis adopts multidisciplinary (geodynamical and seismological) approaches toward understanding dynamics of the Earth's mantle. My geodynamical approach is directed at understanding the relationship between large-scale surface observables (geoid, topography, plate motions) and mantle rheology and convection of the present-day Earth. In chapter 2, I remove shallow mantle structure of various tectonic features to generate "residual tomography." In chapter 3, I show that the pattern, spectrum and amplitude of the "residual topography" are consistent with shallow origin of the "Earth surface dynamic topography;" the long wavelength geoid and topography (l = 2-3) are successfully explained by density models inferred from the "residual tomography," assuming layered mantle convection stratified at the "920 km seismic discontinuity." In chapter 4, I develop a new method to calculate mantle flow with lateral variation of viscosity. The viscosity contrast between continental and oceanic regions is identified to have dominating effects on both the observed poloidal/toroidal ratio and pattern of toroidal motions at long wavelengths. My seismological approach is focused on exploring fine structures near the core-mantle boundary (CMB) and developing new seismic techniques. I discuss the method development and strategies to explore fine structures in the following chapters. In chapter 5, I develop a hybrid method, a combination of analytical and numerical methods, with numerical methods applied in heterogeneous regions only. In chapter 6, I constrain the general structures of the ultra low velocity zones (ULVZ) near the CMB under the south-east Pacific and Iceland. The SKS-SPdKS data are explained by ULVZ with P-velocity reduction of 10%, horizontal length-scales of about 250 km and height of about 40 km. S-velocity reduction of 30% is consistent with the data. In chapter 7, I constrain the detailed structures of the ULVZ near the CMB from observed broadband PKP precursors

  11. Tectonic Storytelling with Open Source and Digital Object Identifiers - a case study about Plate Tectonics and the Geopark Bergstraße-Odenwald

    Science.gov (United States)

    Löwe, Peter; Barmuta, Jan; Klump, Jens; Neumann, Janna; Plank, Margret

    2014-05-01

    The communication of advances in research to the common public for both education and decision making is an important aspect of scientific work. An even more crucial task is to gain recognition within the scientific community, which is judged by impact factor and citation counts. Recently, the latter concepts have been extended from textual publications to include data and software publications. This paper presents a case study for science communication and data citation. For this, tectonic models, Free and Open Source Software (FOSS), best practices for data citation and a multimedia online-portal for scientific content are combined. This approach creates mutual benefits for the stakeholders: Target audiences receive information on the latest research results, while the use of Digital Object Identifiers (DOI) increases the recognition and citation of underlying scientific data. This creates favourable conditions for every researcher as DOI names ensure citeability and long term availability of scientific research. In the developed application, the FOSS tool for tectonic modelling GPlates is used to visualise and manipulate plate-tectonic reconstructions and associated data through geological time. These capabilities are augmented by the Science on a Halfsphere project (SoaH) with a robust and intuitive visualisation hardware environment. The tectonic models used for science communication are provided by the AGH University of Science and Technology. They focus on the Silurian to Early Carboniferous evolution of Central Europe (Bohemian Massif) and were interpreted for the area of the Geopark Bergstraße Odenwald based on the GPlates/SoaH hardware- and software stack. As scientific story-telling is volatile by nature, recordings are a natural means of preservation for further use, reference and analysis. For this, the upcoming portal for audiovisual media of the German National Library of Science and Technology TIB is expected to become a critical service

  12. SECULAR CHANGES IN RELATIONSHIPS BETWEEN PLATE-TECTONIC AND MANTLE-PLUME ENGENDERED PROCESSES DURING PRECAMBRIAN TIME

    Directory of Open Access Journals (Sweden)

    M. V. Mints

    2016-01-01

    Full Text Available Paradoxically, the lists of “proxies” of both plate- and plume-related settings are devoid of even a mention of the high-grade metamorphic rocks (granulite, amphibolite and high-temperature eclogite facies. However, the granulite-gneiss belts and areas which contain these rocks, have a regional distribution in both the Precambrian and the Phanerozoic records. The origin and evolution of the granulite-gneiss belts correspond to the activity of plumes expressed in vigorous heating of the continental crust; intraplate magmatism; formation of rift depressions filled with sediments, juvenile lavas, and pyroclastic flow deposits; and metamorphism of lower and middle crustal complexes under conditions of granulite and high-temperature amphibolite facies that spreads over the fill of rift depressions also. Granulite-gneiss complexes of the East European Craton form one of the main components of the large oval intracontinental tectonic terranes of regional or continental rank. Inclusion of the granulite-gneiss complexes from Eastern Europe, North and South America, Africa, India, China and Australia in discussion of the problem indicated in the title to this paper, suggests consideration of a significant change in existing views on the relations between the plate- and plume-tectonic processes in geological history, as well as in supercontinent assembly and decay. The East European and North American cratons are fragments of the long-lived supercontinent Lauroscandia. After its appearance at ~2.8 Ga, the crust of this supercontinent evolved under the influence of the sequence of powerful mantle plumes (superplumes up to ~0.85 Ga. During this time Lauroscandia was subjected to rifting, partial breakup and the following reconstruction of the continent. The processes of plate-tectonic type (rifting with the transition to spreading and closing of the short-lived ocean with subduction within Lauroscandia were controlled by the superplumes. Revision of the

  13. Barrel organ of plate tectonics - a new tool for outreach and education

    Science.gov (United States)

    Broz, Petr; Machek, Matěj; Šorm, Zdar

    2016-04-01

    Plate tectonics is the major geological concept to explain dynamics and structure of Earth's outer shell, the lithosphere. In the plate tectonic theory processes in the Earth lithosphere and its dynamics is driven by the relative motion and interaction of lithospheric plates. Geologically most active regions on Earth often correlate with the lithospheric plate boundaries. Thus for explaining the earth surface evolution, mountain building, volcanism and earthquake origin it is important to understand processes at the plate boundaries. However these processes associated with plate tectonics usually require significant period of time to take effects, therefore, their entire cycles cannot be directly observed in the nature by humans. This makes a challenge for scientists studying these processes, but also for teachers and popularizers trying to explain them to students and to the general public. Therefore, to overcome this problem, we developed a mechanical model of plate tectonics enabling demonstration of most important processes associated with plate tectonics in real time. The mechanical model is a wooden box, more specifically a special type of barrel organ, with hand painted backdrops in the front side. These backdrops are divided into several components representing geodynamic processes associated with plate tectonics, specifically convective currents occurring in the mantle, sea-floor spreading, a subduction of the oceanic crust under the continental crust, partial melting and volcanism associated with subduction, a formation of magmatic stripes, an ascent of mantle plume throughout the mantle, a volcanic activity associated with hot spots, and a formation and degradation of volcanic islands on moving lithospheric plate. All components are set in motion by a handle controlled by a human operator, and the scene is illuminated with colored lights controlled automatically by an electric device embedded in the box. Operation of the model may be seen on www

  14. Coupling intensity and isostatic competition between subducting slab and overriding plate control trench motions and tectonics of the overriding plate

    Science.gov (United States)

    Wu, G.; Moresi, L. N.

    2017-12-01

    Trench motions not only reflect tectonic regimes on the overriding plate but also shed light on the competition between subducting slab and overriding plate, however, major controls over trench advance or retreat and their consequences are still illusive. We use 2D thermo-mechanical experiments to study the problem. We find that the coupling intensity particularly in the uppermost 200 km and the isostatic competition between subducting slab and overriding plate largely determine trench motion and tectonics of in the overriding plate. Coupling intensity is the result of many contributing factors, including frictional coefficient of brittle part of the subducting interface and the viscosity of the ductile part, thermal regime and rheology of the overriding plate, and water contents and magmatic activity in the subducting slab and overriding plate. In this study, we are not concerned with the dynamic evolution of individual controlling parameter but simply use effective media. For instance, we impose simple model parameters such as frictional coefficient and vary the temperature and strain-rate dependent viscosity of the weak layer between the subducting slab and overriding plate. In the coupled end-member case, strong coupling leads to strong corner flow, depth-dependent compression/extension, and mantle return flow on the overriding plate side. It results in fast trench retreat, broad overriding plate extension, and even slab breakoff. In the decoupled end-member case, weak coupling causes much weaker response on the overriding plate side compared with the coupled end-member case, and the subducting slab can be largely viewed as a conveyer belt. We find that the isostatic competition between the subducting slab and overriding plate also has a major control over trench motion, and may better be viewed in 3D models. This is consistent with the findings in previous 3D studies that trench motion is most pronounced close to the slab edge. Here we propose that the

  15. Using a Web GIS Plate Tectonics Simulation to Promote Geospatial Thinking

    Science.gov (United States)

    Bodzin, Alec M.; Anastasio, David; Sharif, Rajhida; Rutzmoser, Scott

    2016-01-01

    Learning with Web-based geographic information system (Web GIS) can promote geospatial thinking and analysis of georeferenced data. Web GIS can enable learners to analyze rich data sets to understand spatial relationships that are managed in georeferenced data visualizations. We developed a Web GIS plate tectonics simulation as a capstone learning…

  16. A tale of two arcs? Plate tectonics of the Izu-Bonin-Mariana (IBM) arc using subducted slab constraints

    Science.gov (United States)

    Wu, J. E.; Suppe, J.; Renqi, L.; Kanda, R. V. S.

    2014-12-01

    Published plate reconstructions typically show the Izu-Bonin Marianas arc (IBM) forming as a result of long-lived ~50 Ma Pacific subduction beneath the Philippine Sea. These reconstructions rely on the critical assumption that the Philippine Sea was continuously coupled to the Pacific during the lifetime of the IBM arc. Because of this assumption, significant (up to 1500 km) Pacific trench retreat is required to accommodate the 2000 km of Philippine Sea/IBM northward motion since the Eocene that is constrained by paleomagnetic data. In this study, we have mapped subducted slabs of mantle lithosphere from MITP08 global seismic tomography (Li et al., 2008) and restored them to a model Earth surface to constrain plate tectonic reconstructions. Here we present two subducted slab constraints that call into question current IBM arc reconstructions: 1) The northern and central Marianas slabs form a sub-vertical 'slab wall' down to maximum 1500 km depths in the lower mantle. This slab geometry is best explained by a near-stationary Marianas trench that has remained +/- 250 km E-W of its present-day position since ~45 Ma, and does not support any significant Pacific slab retreat. 2) A vanished ocean is revealed by an extensive swath of sub-horizontal slabs at 700 to 1000 km depths in the lower mantle below present-day Philippine Sea to Papua New Guinea. We call this vanished ocean the 'East Asian Sea'. When placed in an Eocene plate reconstruction, the East Asian Sea fits west of the reconstructed Marianas Pacific trench position and north of the Philippine Sea plate. This implies that the Philippine Sea and Pacific were not adjacent at IBM initiation, but were in fact separated by a lost ocean. Here we propose a new IBM arc reconstruction constrained by subducted slabs mapped under East Asia. At ~50 Ma, the present-day IBM arc initiated at equatorial latitudes from East Asian Sea subduction below the Philippine Sea. A separate arc was formed from Pacific subduction below

  17. Reconstruction of Northeast Asian Deformation Integrated with Western Pacific Plate Subduction since 200 Ma

    Science.gov (United States)

    Liu, S.; Gurnis, M.; Ma, P.; Zhang, B.

    2017-12-01

    The configuration and kinematics of continental deformation and its marginal plate tectonics on the Earth's surface are intrinsic manifestations of plate-mantle coupling. The complex interactions of plate boundary forces result in plate motions that are dominated by slab pull and ridge push forces and the effects of mantle drag; these interactions also result in continental deformation with a complex basin-mountain architecture and evolution. The kinematics and evolution of the western Pacific subduction and northeast Asian continental-margin deformation are a first-order tectonic process whose nature and chronology remains controversial. This paper implements a "deep-time" reconstruction of the western Pacific subduction, continental accretion or collision and basin-mountain deformation in northeast Asia since 200 Ma based on a newly revised global plate model. The results demonstrate a NW-SE-oriented shortening from 200-137 Ma, a NWW-SEE-oriented extension from 136-101 Ma, a nearly N-S-oriented extension and uplift with a short-term NWW-SEE-oriented compressional inversion in northeast China from 100-67 Ma, and a NW-SE- and nearly N-S-oriented extension from 66 Ma to the present day. The western Pacific oceanic plate subducted forward under East Asia along Mudanjiang-Honshu Island during the Jurassic, and the trenches retreated to the Sikhote-Alin, North Shimanto, and South Shimanto zones from ca. 137-128 Ma, ca. 130-90 Ma, and in ca. 60 Ma, respectively. Our time-dependent analysis of plate motion and continental deformation coupling suggests that the multi-plate convergent motion and ocean-continent convergent orogeny were induced by advance subduction during the Jurassic and earliest Cretaceous. Our analysis also indicates that the intra-continent rifting and back-arc extension were triggered by trench retreat during the Cretaceous and that the subduction of oceanic ridge and arc were triggered by trench retreat during the Cenozoic. Therefore, reconstructing

  18. Plate Tectonics as a Far-From-Equilibrium Self-Organized Dissipative System

    Science.gov (United States)

    Anderson, D. L.

    2001-12-01

    A fluid above the critical Rayleigh number is far from equilibrium and spontaneously organizes itself into patterns involving the collective motion of large numbers of molecules which are resisted by the viscosity of the fluid. No external template is involved in forming the pattern. In 1928 Pearson showed that Bénard's experiments were driven by variations in surface tension at the top of the fluid and the surface motions drove convection in the fluid. In this case, the surface organized itself AND the underlying fluid. Both internal buoyancy driven flow and flow driven by surface forces can be far-from-equilibrium self-organized open systems that receive energy and matter from the environment. In the Earth, the cold thermal boundary layer at the surface drives plate tectonics and introduces temperature, shear and pressure gradients into the mantle that drive mantle convection. The mantle provides energy and material but may not provide the template. Plate tectonics is therefore a candidate for a far-from-equilibrium dissipative self-organizing system. Alternatively, one could view mantle convection as the self-organized system and the plates as simply the surface manifestation. Lithospheric architecture also imposes lateral temperature gradients onto the mantle which can drive and organize flow. Far-from-equilibrium self-organization requires; an open system, interacting parts, nonlinearities or feedbacks, an outside steady source of energy or matter, multiple possible states and a source of dissipation. In uniform fluids viscosity is the source of dissipation. Sources of dissipation in the plate system include bending, breaking, folding, shearing, tearing, collision and basal drag. These can change rapidly, in contrast to plate driving forces, and introduce the sort of fluctuations that can reorganize far-from-equilibrium systems. Global plate reorganizations can alternatively be thought of as convective overturns of the mantle, or thermal weakening of plates

  19. A new plate tectonic concept for the eastern-most Mediterranean

    Science.gov (United States)

    Huebscher, C.; McGrandle, A.; Scaife, G.; Spoors, R.; Stieglitz, T.

    2012-04-01

    Owing to the seismogenic faults bordering the Levant-Sinai realm and the discovery of giant gas reservoirs in the marine Levant Basin the scientific interest in this tectonically complex setting increased in recent years. Here we provide a new model for the Levant Basin architecture and adjacent plate boundaries emphasizing the importance of industrial seismic data for frontier research in earth science. PSDM seismics, residual gravity and depth to basement maps give a clear line of evidence that the Levant Basin, formerly considered as a single tectonic entity, is divided into two different domains. Highly stretched continental crust in the southern domain is separated from deeper and presumably Tethyan oceanic crust in the north. A transform continuing from southwest Cyprus to the Carmel Fault in northern Israel is considered as the boundary. If this interpretation holds, the Carmel-Cyprus Transform represents a yet unknown continent-ocean boundary in the eastern Mediterranean, thus adding new constrains for the Mediterranean plate tectonic puzzle. The Eratosthenes Seamount, considered as the spearhead of incipient continental collision in the eastern Mediterranean, is interpreted as a carbonate platform that developed above a volcanic basement. NW-SE trending strike-slip faults are abundant in the entire Levant region. Since this trend also shapes the topography of the Levant hinterland including Quaternary deposits their recent tectonic activity is quite likely. Thus, our study supports previous studies which attributed the evolution of submarine canyons and Holocene triggering of mass failures not only to salt tectonics or depositional processes, but also to active plate-tectonics.

  20. North America-Greenland-Eurasian relative motions: implications for circum-arctic tectonic reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Rowley, D.B.; Lottes, A.L.; Ziegler, A.M.

    1985-02-01

    The Mesozoic-Cenozoic tectonic evolution of the Circum-Arctic region is based on constraints imposed by (1) relative motion histories of the three major plates (North America, Greenland, and Eurasia) and a number of smaller pieces, and (2) distribution and age of sutures, accretionary prisms, volcanic arcs, fold-thrust belts, stretched continental crust, strike-slip faults, and ocean floor. The authors conclude that: (1) North America and Eurasia remained relatively fixed to each other until the latest Cretaceous-Paleocene opening of the Labrador Sea-Baffin Bay and Greenland-Norwegian and Eurasian basins (earlier convergence between North America and Eurasia in the Bering Sea region shown on many reconstructions are artifacts of incorrect plate reconstructions); (2) the North Slope-Seward-Chukotka block has constituted an isthmus connection between North America and northeast Asia since at least the middle Paleozoic and did not rotate away from the Canadian Arctic; (3) the Canada basin opened behind a clockwise-rotating Alpha Cordillera-Mendeleyev ridge arc during the Early to middle Cretaceous and consumed older, Paleozoic(.) Makarov basin ocean floor (the Chukchi cap is a detached continental fragment derived from the Beaufort Sea; the North Slope Arctic margin is a left-lateral transform fault associated with the opening of the Canada basin); and (4) the Nares Strait fault has a net relative displacement of approximately 25 km, but actual motion between Greenland and northern Ellesmere was about 250 km of strongly transpressive motion that resulted in the Eurekan and Svalbardian orogenies.

  1. Petroleum formation by Fischer-Tropsch synthesis in plate tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Szatmari, P. (Petrobras Research Center, Rio de Janeiro (Brazil))

    1989-08-01

    A somewhat speculative hypothesis of petroleum genesis in the upper lithosphere is proposed, based on Fischer-Tropsch synthesis. This hypothesis is distinct from both the organic (biogenic) model and the inorganic model of hydrocarbon degassing from the Earth's interior. The hypothesis presented in this paper proposes that petroleum liquids form by Fischer-Tropsch synthesis on magnetite and hematite catalysts when carbon dioxide (derived by massive metamorphic or igneous decarbonation of subducted sedimentary carbonates) reacts with hydrogen generated by the serpentinization (in the absence of air) of shallow-mantle lithosphere and ophiolite thrust sheets. Oblique plate movements may favor hydrocarbon formation by creating deep faults that aid fluid flow and serpentinization. The world's richest oil provinces, including those of the Middle East, may be tentatively interpreted to have formed by this mechanism. 8 figs., 1 tab.

  2. GIS and geodatabases application to global scale plate tectonics modelling

    OpenAIRE

    Hochard, Cyril; Stampfli, Gérard

    2008-01-01

    Les reconstructions palinspastiques fournissent le cadre idéal à de nombreuses études géologiques, géographiques, océanographique ou climatiques. En tant qu’historiens de la terre, les “reconstructeurs” essayent d’en déchiffrer le passé. Depuis qu’ils savent que les continents bougent, les géologues essayent de retracer leur évolution à travers les âges. Si l’idée originale de Wegener était révolutionnaire au début du siècle passé, nous savons depuis le début des années « soixante » que les c...

  3. GIS and geodatabases application to global scale plate tectonics modelling

    OpenAIRE

    Hochard, C.

    2008-01-01

    Les reconstructions palinspastiques fournissent le cadre idéal à de nombreuses études géologiques, géographiques, océanographique ou climatiques. En tant qu?historiens de la terre, les "reconstructeurs" essayent d?en déchiffrer le passé. Depuis qu?ils savent que les continents bougent, les géologues essayent de retracer leur évolution à travers les âges. Si l?idée originale de Wegener était révolutionnaire au début du siècle passé, nous savons depuis le début des années « soixante » que les c...

  4. Intra-Arc extension in Central America: Links between plate motions, tectonics, volcanism, and geochemistry

    Science.gov (United States)

    Phipps Morgan, Jason; Ranero, Cesar; Vannucchi, Paola

    2010-05-01

    This study revisits the kinematics and tectonics of Central America subduction, synthesizing observations of marine bathymetry, high-resolution land topography, current plate motions, and the recent seismotectonic and magmatic history in this region. The inferred tectonic history implies that the Guatemala-El Salvador and Nicaraguan segments of this volcanic arc have been a region of significant arc tectonic extension; extension arising from the interplay between subduction roll-back of the Cocos Plate and the ~10-15 mm/yr slower westward drift of the Caribbean plate relative to the North American Plate. The ages of belts of magmatic rocks paralleling both sides of the current Nicaraguan arc are consistent with long-term arc-normal extension in Nicaragua at the rate of ~5-10 mm/yr, in agreement with rates predicted by plate kinematics. Significant arc-normal extension can ‘hide' a very large intrusive arc-magma flux; we suggest that Nicaragua is, in fact, the most magmatically robust section of the Central American arc, and that the volume of intrusive volcanism here has been previously greatly underestimated. Yet, this flux is hidden by the persistent extension and sediment infill of the rifting basin in which the current arc sits. Observed geochemical differences between the Nicaraguan arc and its neighbors which suggest that Nicaragua has a higher rate of arc-magmatism are consistent with this interpretation. Smaller-amplitude, but similar systematic geochemical correlations between arc-chemistry and arc-extension in Guatemala show the same pattern as the even larger variations between the Nicaragua arc and its neighbors. We are also exploring the potential implications of intra-arc extension for deformation processes along the subducting plate boundary and within the forearc ‘microplate'.

  5. Plate tectonic model for the oligo-miocene evolution of the western Mediterranean

    Science.gov (United States)

    Cohen, Curtis R.

    1980-10-01

    This paper outlines a plate tectonic model for the Oligo-Miocene evolution of the western Mediterranean which incorporates recent data from several tectonic domains (Corsica, Sardinia, the Kabylies, Balearic promontory, Iberia, Algero-Provençal Basin and Tunisian Atlas). Following late Mesozoic anticlockwise rotation of the Iberian peninsula (including the Balearic promontory and Sardinia), late Eocene collision occurred between the Kabylies and Balearic promontory forming a NE-trending suture with NW-tectonic polarity. As a result of continued convergence between the African and European plates, a polarity flip occurred and a southward-facing trench formed south of the Kabylie—Balearic promontory suture. During late Oligocene time an E-W-trending arc and marginal basin developed behind the southward-facing trench in the area of the present-day Gulf of Lion. Opening of this basin moved the Corsica—Sardinia—Calabria—Petit Kabylie—Menorca plate southward, relative to the African plate. Early Miocene back-arc spreading in the area between the Balearic promontory and Grand Kabylie emplaced the latter in northern Algeria and formed the South Balearic Basin. Coeval with early Miocene back-arc basin development, the N-S-extension in the Gulf of Lion marginal basin changed to a more NW-SE direction causing short-lived extension in the area of the present-day Valencia trough and a 30° anticlockwise rotation of the Corsica-Sardinia-Calabria—Petit Kabylie plate away from the European plate. Early—middle Miocene deformation along the western Italian and northeastern African continental margins resulted from this rotation. During the early late Miocene (Tortonian), spreading within a sphenochasm to the southwest of Sardinia resulted in the emplacement of Petit Kabylie in northeastern Algeria.

  6. Mandibular reconstruction using a titanium plate: the impact of radiation therapy on plate preservation

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Janice K; Stern, Robin L; Robinson, Marilyn G; Bowers, Michael K; Kubo, Hideo D; Donald, Paul J; Rosenthal, Seth A; Fu, Karen K

    1995-06-15

    Purpose: To evaluate the soft tissue and bone tolerance of radiation therapy (RT) in patients undergoing radical composite resection and mandibular reconstruction using a bridging titanium plate with myocutaneous flap closure. Methods and Materials: From 1990 to 1994, 47 patients with primary or recurrent oral cavity or oropharyngeal carcinomas were treated with radical composite resection and mandibular reconstruction using a bridging titanium plate with myocutaneous flap closure. Eleven patients received no RT (no RT), 10 patients received RT greater than 10 months from the time of surgery (remote RT), and 26 patients received RT within 12 weeks of surgery (perioperative RT). The radiation dose to the reconstructed mandible ranged from 45 to 75 Gy (median 63 Gy). The effect of the titanium plate on the radiation dose was measured using film dosimetry and soft tissue and bone-equivalent materials. The median follow-up was 17 months (range: 3-50 months). Results: Late complications included four patients with osteomyelitis or necrosis, two plate exposures requiring flap revision, one chronic infection, two cases of chronic pain, two fistulae, and one case of trismus and malocclusion. The crude incidence of late complications by treatment was: (a) no RT: 3 of 11 patients (27%); (b) remote RT: 2 of 10 patients (20%); and (c) perioperative RT: 9 of 26 patients (35%). One patient in the no-RT group lost the plate due to chronic pain. Five patients in the perioperative RT group also had plate loss, four due to osteomyelitis and/or necrosis, and one due to pain related to a recurrent tumor. No patients in the remote RT group had plate loss. The actuarial prosthesis preservation rate at 2 years was 88% for the no RT, 100% for the remote RT, and 57% for the perioperative RT groups (p = 0.05). Phantom dose measurements showed that for parallel opposed 6 MV photon beams, there was no significant increase in the dose proximal or distal to the plate in either a soft tissue- or

  7. Finding the last 200Ma of subducted lithosphere in tomography and incorporating it into plate reconstructions

    Science.gov (United States)

    Suppe, J.; Wu, J.; Chen, Y. W.

    2016-12-01

    Precise plate-tectonic reconstruction of the Earth has been constrained largely by the seafloor magnetic-anomaly record of the present oceans formed during the dispersal of the last supercontinent since 200Ma. The corresponding world that was lost to subduction has been only sketchily known. We have developed methodologies to map in 3D these subducted slabs of lithosphere in seismic tomography and unfold them to the Earth surface, constraining their initial size, shapes and locations. Slab edges are commonly formed at times of plate reorganization (for example bottom edges typically record initiation of subduction) such that unfolded slabs fit together at times of reorganization, as we illustrate for the Nazca slab at 80Ma and the western Pacific slabs between Kamchatka and New Zealand at 50Ma. Mapping to date suggests that a relatively complete and decipherable record of lithosphere subducted over the last 200Ma may exist in the mantle today, providing a storehouse for new discoveries. We briefly illustrate our procedure for obtaining slab-constrained plate-tectonic models from tomography with our recent study of the Philippine Sea plate, whose motions and tectonic history have been the least known of the major plates because it has been isolated from the global plate and hotspot circuit by trenches. We mapped and unfolded 28 subducted slabs in the mantle under East Asia and Australia/Oceania to depths of 1200km, with a subducted area of 25% of present-day global oceanic lithosphere, and incorporated them as constraints into a new globally-consistent plate reconstruction of the Philippine Sea and surrounding East Asia, leading to a number of new insights, including: [1] discovery of a major (8000 km x 2500 km) set of vanished oceans that we call the East Asia Sea that existed between the Pacific and Indian Oceans, now represented by flat slabs in the lower mantle under present-day Philippine Sea, eastern Sundaland and northern Australia and [2] the Philippine Sea

  8. Reconstructing the tectonic history of Fennoscandia from its margins: The past 100 million years

    Energy Technology Data Exchange (ETDEWEB)

    Muir Wood, R [EQE International Ltd (United Kingdom)

    1995-12-01

    In the absence of onland late Mesozoic and Cenozoic geological formations the tectonic history of the Baltic Shield over the past 100 million years can be reconstructed from the thick sedimentary basins that surround Fennoscandia on three sides. Tectonic activity around Fennoscandia through this period has been diverse but can be divided into four main periods: a. pre North Atlantic spreading ridge (100-60 Ma) when transpressional deformation on the southern margins of Fennoscandia and transtensional activity to the west was associated with a NNE-SSW maximum compressive stress direction; b. the creation of the spreading ridge (60-45 Ma) when there was rifting along the western margin; c. the re-arrangement of spreading axes (45-25 Ma) when there was a radial compression around Fennoscandia, and d. the re-emergence of the Iceland hot-spot (25-0 Ma) when the stress-field has come to accord with ridge or plume `push`. Since 60 Ma the Alpine plate boundary has had little influence on Fennoscandia. The highest levels of deformation on the margins of Fennoscandia were achieved around 85 Ma, 60-55 Ma, with strain-rates around 10{sup -9}/year. Within the Baltic Shield long term strain rates have been around 10{sup -1}1/year, with little evidence for significant deformations passing into the shield from the margins. Fennoscandian Border Zone activity, which was prominent from 90-60 Ma, was largely abandoned following the creation of the Norwegian Sea spreading ridge, and with the exception of the Lofoten margin, there is subsequently little evidence for deformation passing into Fennoscandia. Renewal of modest compressional deformation in the Voering Basin suggest that the `Current Tectonic Regime` is of Quaternary age although the orientation of the major stress axis has remained consistent since around 10 Ma. The past pattern of changes suggest that in the geological near-future variations are to be anticipated in the magnitude rather than the orientation of stresses.

  9. Reconstructing the tectonic history of Fennoscandia from its margins: The past 100 million years

    International Nuclear Information System (INIS)

    Muir Wood, R.

    1995-12-01

    In the absence of onland late Mesozoic and Cenozoic geological formations the tectonic history of the Baltic Shield over the past 100 million years can most readily be reconstructed from the thick sedimentary basins that surround Fennoscandia on three sides. Tectonic activity around Fennoscandia through this period has been diverse but can be divided into four main periods: a. pre North Atlantic spreading ridge (100-60 Ma) when transpressional deformation on the southern margins of Fennoscandia and transtensional activity to the west was associated with a NNE-SSW maximum compressive stress direction; b. the creation of the spreading ridge (60-45 Ma) when there was rifting along the western margin; c. the re-arrangement of spreading axes (45-25 Ma) when there was a radial compression around Fennoscandia, and d. the re-emergence of the Iceland hot-spot (25-0 Ma) when the stress-field has come to accord with ridge or plume 'push'. Since 60 Ma the Alpine plate boundary has had little influence on Fennoscandia. The highest levels of deformation on the margins of Fennoscandia were achieved around 85 Ma, 60-55 Ma, with strain-rates around 10 -9 /year. Within the Baltic Shield long term strain rates have been around 10 -1 1/year, with little evidence for evidence for significant deformations passing into the shield from the margins. Fennoscandian Border Zone activity, which was prominent from 90-60 Ma, was largely abandoned following the creation of the Norwegian Sea spreading ridge, and with the exception of the Lofoten margin, there is subsequently very little evidence for deformation passing into Fennoscandia. Renewal of modest compressional deformation in the Voering Basin suggest that the 'Current Tectonic Regime' is of Quaternary age although the orientation of the major stress axis has remained approximately consistent since around 10 Ma. The past pattern of changes suggest that in the geological near-future variations are to be anticipated in the magnitude rather

  10. Tectonics of the Philippine Sea plate before and after 52 Ma subduction initiation to form the Izu-Bonin-Mariana arc

    Science.gov (United States)

    Ishizuka, O.; Tani, K.; Harigane, Y.; Umino, S.; Stern, R. J.; Reagan, M. K.; Hickey-Vargas, R.; Yogodzinski, G. M.; Kusano, Y.; Arculus, R. J.

    2016-12-01

    Robust tectonic reconstruction of the evolving Philippine Sea Plate for the period immediately before and after subduction initiation 52 Ma to form the Izu-Bonin-Mariana (IBM) arc is prerequisite to understand cause of subduction initiation (SI) and test competing hypotheses for SI such as spontaneous or induced nucleation. Understanding of nature and origin of overriding and subducting plates is especially important because plate density is a key parameter controlling SI based on numerical modeling (e.g., Leng and Gurnis 2015). There is increasing evidence that multiple geological events related to changing stress fields took place in and around Philippine Sea plate about the time of SI 52 Ma (Ishizuka et al., 2011). For our understanding of the early IBM arc system to increase, it is important to understand the pattern and tempo of these geological events, particularly the duration and extent of seafloor spreading in the proto arc associated with SI, and its temporal relationship with spreading in the West Philippine Basin (WPB). IODP Exp. 351 provided evidence of SI-related seafloor spreading west of the Kyushu-Palau Ridge (Arculus et al., 2015). Planned age determination of the basement crust at Site U1438 will constrain the timing and geometry of SI-related spreading and its relationship to variation in mode of spreading in the WPB including rotation of spreading axis. Some tectonic reconstructions suggest that part of the IBM arc could have formed on "young" WPB crust. Dredging of the northern Mariana forearc crust and mantle in 2014 aimed to test this hypothesis. Preliminary data indicates that early arc crustal section of the N. Mariana forearc is geochemically and temporally similar to that exposed in the Bonin and southern Mariana forearcs. New tectonic reconstructions for the nascent IBM system will be presented based on these observations.

  11. Commentary: The Feasibility of Subduction and Implications for Plate Tectonics on Jupiter's Moon Europa

    Science.gov (United States)

    Kattenhorn, Simon A.

    2018-03-01

    A new modeling-based study by Johnson et al. (2017, https://doi.org/10.1002/2017JE005370) lends support to the hypothesis that portions of Europa's surface may have been removed by the process of subduction, as suggested by Kattenhorn and Prockter (2014, https://doi.org/10.1038/NGEO2245). Using a simple 1-D model that tracks the thermal and density structure of a descending ice plate, Johnson et al. show that ice plates with 10% porosity and overall salt contents of 5%, which differ in salt content by 2.5% from the surrounding reference ice shell, are nonbuoyant and thus likely to sink through the underlying, convecting portion of the ice shell. The feasibility of subduction in an ice shell is critical to the existence of icy plate tectonics, which is hypothesized to exist at least locally on Europa, potentially making it the only other Solar System body other than Earth with a surface modified by plate tectonics.

  12. Plate tectonics hiati as the cause of global glaciations: 2. The late Proterozoic 'Snowball Earth'

    Science.gov (United States)

    Osmaston, M. F.

    2003-04-01

    A fundamental reappraisal of the mechanisms that drive plate tectonics has yielded the remarkable conclusion that, for at least the past 130 Ma, the principal agent has not been ridge-push or slab-pull but a CW-directed torque (probably of electromagnetic origin at the CMB) reaching the deep (>600 km, e.g.[1]) tectospheric keel of the Antarctica craton. Major changes in spreading direction marked both ends of the 122--85 Ma Cretaceous Superchron and started by forming the Ontong Java Plateau. Action of MORs as gearlike linkages has driven Africa and India CCW since Gondwana breakup and continues to drive the Pacific plate CCW. In the Arctic there is now no cratonic keel to pick up any corresponding polar torque, so northern hemisphere plate tectonics is far less active. The thesis of this contribution is that in the Neoproterozoic the lack of cratons at high latitudes would have deprived plate tectonics of this motivation, causing MORs to die (see below) and a major fall in sea-level, leading to global glaciation as outlined in Part 1 for the Huronian events. Like that seen during that first hiatus, dyke-swarm volcanism could have arisen from thermal shrinkage of the global lithosphere, providing CO2 and ash-covering that interrrupted glacial episodes. In oceanic settings this volcanism would have lowered pH and supplied Fe2+ for shallow bio-oxygenic action to deposit as BIF. My multifacet studies of the subduction process convince me that the rapid development of "flat-slab" interface profiles involves the physical removal of hanging-wall material in front of the downbend by basal subduction tectonic erosion (STE). Historically this, and its inferred ubiquity in the Archaean as the precursor to PSM (Part 1), suggests that the required subducting-plate buoyancy is thermal. Accordingly, a redesign [2] of the MOR process has incorporated the heat-containing LVZ as an integral part of the plate and luckily provides a lot more ridge-push to ensure the subduction of

  13. A probabilistic approach towards understanding how planet composition affects plate tectonics - through time and space.

    Science.gov (United States)

    Stamenkovic, V.

    2017-12-01

    We focus on the connections between plate tectonics and planet composition — by studying how plate yielding is affected by surface and mantle water, and by variable amounts of Fe, SiC, or radiogenic heat sources within the planet interior. We especially explore whether we can make any robust conclusions if we account for variable initial conditions, current uncertainties in model parameters and the pressure dependence of the viscosity, as well as uncertainties on how a variable composition affects mantle rheology, melting temperatures, and thermal conductivities. We use a 1D thermal evolution model to explore with more than 200,000 simulations the robustness of our results and use our previous results from 3D calculations to help determine the most likely scenario within the uncertainties we still face today. The results that are robust in spite of all uncertainties are that iron-rich mantle rock seems to reduce the efficiency of plate yielding occurring on silicate planets like the Earth if those planets formed along or above mantle solidus and that carbon planets do not seem to be ideal candidates for plate tectonics because of slower creep rates and generally higher thermal conductivities for SiC. All other conclusions depend on not yet sufficiently constrained parameters. For the most likely case based on our current understanding, we find that, within our range of varied planet conditions (1-10 Earth masses), planets with the greatest efficiency of plate yielding are silicate rocky planets of 1 Earth mass with large metallic cores (average density 5500-7000 kg m-3) with minimal mantle concentrations of iron (as little as 0% is preferred) and radiogenic isotopes at formation (up to 10 times less than Earth's initial abundance; less heat sources do not mean no heat sources). Based on current planet formation scenarios and observations of stellar abundances across the Galaxy as well as models of the evolution of the interstellar medium, such planets are

  14. A harbinger of plate tectonics: a commentary on Bullard, Everett and Smith (1965) 'The fit of the continents around the Atlantic'.

    Science.gov (United States)

    Dewey, John F

    2015-04-13

    In the 1960s, geology was transformed by the paradigm of plate tectonics. The 1965 paper of Bullard, Everett and Smith was a linking transition between the theories of continental drift and plate tectonics. They showed, conclusively, that the continents around the Atlantic were once contiguous and that the Atlantic Ocean had grown at rates of a few centimetres per year since the Early Jurassic, about 160 Ma. They achieved fits of the continental margins at the 500 fathom line (approx. 900 m), not the shorelines, by minimizing misfits between conjugate margins and finding axes, poles and angles of rotation, using Euler's theorem, that defined the unique single finite difference rotation that carried congruent continents from contiguity to their present positions, recognizing that the real motion may have been more complex around a number of finite motion poles. Critically, they were concerned only with kinematic reality and were not restricted by considerations of the mechanism by which continents split and oceans grow. Many of the defining features of plate tectonics were explicit or implicit in their reconstructions, such as the torsional rigidity of continents, Euler's theorem, closure of the Tethyan ocean(s), major continental margin shear zones, the rapid rotation of small continental blocks (Iberia) around nearby poles, the consequent opening of small wedge-shaped oceans (Bay of Biscay), and misfit overlaps (deltas and volcanic piles) and underlaps (stretched continental edges). This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

  15. Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical, magnetic and tectonic data reveal early plate tectonic genes flanking subduction margins

    Directory of Open Access Journals (Sweden)

    Maarten de Wit

    2018-05-01

    Full Text Available The Makhonjwa Mountains, traditionally referred to as the Barberton Greenstone Belt, retain an iconic Paleoarchean archive against which numerical models of early earth geodynamics can be tested. We present new geologic and structural maps, geochemical plots, geo- and thermo-chronology, and geophysical data from seven silicic, mafic to ultramafic complexes separated by major shear systems across the southern Makhonjwa Mountains. All reveal signs of modern oceanic back-arc crust and subduction-related processes. We compare the rates of processes determined from this data and balance these against plate tectonic and plume related models. Robust rates of both horizontal and vertical tectonic processes derived from the Makhonjwa Mountain complexes are similar, well within an order of magnitude, to those encountered across modern oceanic and orogenic terrains flanking Western Pacific-like subduction zones. We conclude that plate tectonics and linked plate-boundary processes were well established by 3.2–3.6 Ga. Our work provides new constraints for modellers with rates of a ‘basket’ of processes against which to test Paleoarchean geodynamic models over a time period close to the length of the Phanerozoic. Keywords: Paleoarchean, Barberton Greenstone Belt, Onverwacht Suite, Geologic bedrock and structural maps, Geochemistry and geophysics, Plate tectonics

  16. Tectonics and Non-isostatic Topography of the Mariana Trench and Adjacent Plates

    Science.gov (United States)

    Hongyu, L.; Lin, J.; Zhou, Z.; Zhang, F.

    2017-12-01

    Multi-types of geophysical data including multibeam bathymetry, sediment thickness, gravity anomaly, and crustal magnetic age were analyzed to investigate tectonic processes of the Mariana Trench and the surrounding plates. We calculated non-Airy-isostatic topography by removing from the observed bathymetry the effects of sediment loading, thermal subsidence, and Airy local isostatically-compensated topography. The Mariana Trench was found to be associated with a clearly defined zone of negative non-isostatic topography, which was caused by flexural bending of the subducting Pacific plate and with the maximum depth anomaly and flexural bending near the Challenger Deep. In contrast, the Caroline Ridge and Caroline Islands Chain have much more subdued non-isostatic topography, indicating their higher topography is largely compensated by thicker crust. Along the Mariana Trough, the northern and central segments appear to be associated with relatively low magma supply as indicated by the relatively low topography and thin crust. In contrast, the southern Mariana Trough is associated with relatively high magma supply as indicated by the relatively high and smoother topography, an axial high spreading center, and relatively thick crust. The southern end of the Mariana Trough was also found to be associated with positive non-isostatic topographic anomaly, which might be caused by the complex tectonic deformation of the overriding Mariana and Philippine Sea plates and their interaction with the subducting Pacific plate. Analysis further revealed that the southern Mariana Arc, located between the Mariana Trench and Mariana Trough, is associated with positive non-isostatic topographic anomalies, which may be explained by the late stage magmatic loading on the older and thus stronger lithospheric plate of the Mariana volcanic arc.

  17. Stagnant lids and mantle overturns: Implications for Archaean tectonics, magmagenesis, crustal growth, mantle evolution, and the start of plate tectonics

    Directory of Open Access Journals (Sweden)

    Jean H. Bédard

    2018-01-01

    probability that oceanic crustal segments could founder in an organized way, producing a gradual evolution of pre-subduction convergent margins into modern-style active subduction systems around 2.5 Ga. Plate tectonics today is constituted of: (1 a continental drift system that started in the Early Archaean, driven by deep mantle currents pressing against the Archaean-age sub-continental lithospheric mantle keels that underlie Archaean cratons; (2 a subduction-driven system that started near the end of the Archaean.

  18. Driving Forces of Plate Tectonics and Evolution of the Oceanic Lithosphere and Asthenosphere

    Science.gov (United States)

    Forsyth, D. W.

    2017-12-01

    As plate tectonics became established as an excellent kinematic description of the relative motions of different blocks of the Earth's lithosphere, many investigators also began exploring the forces involved in driving the plate motions. Because the plates move at nearly constant velocities over long periods of time and inertial terms are unimportant, driving forces must always be balanced by resisting forces in a way that regulates the velocities. Forsyth and Uyeda (1975) incorporated the balancing of torques on the individual plates to help constrain the relative importance of the driving and resisting forces, as parameterized in a way based on prior model investigations of individual parts of the convecting system. We found that the primary driving force was sinking of subducting lithosphere at trenches, balanced largely by viscous resisting forces in the sub-asthenospheric mantle; that viscous drag beneath the oceanic plates was negligible; and that mid-ocean ridges provided a relatively small push. One of the early questions was whether there was buoyant upwelling on a large scale beneath mid-ocean ridges as part of a whole mantle convection system with subduction of the plates representing the downwelling limb. If so, then it would be likely that the plates were just riding on top of large convection cells. Seismic tomography has demonstrated that, on average, there are no deep roots beneath mid-ocean ridges, so that active, buoyant upwelling from the deep mantle does not exist beneath spreading centers. However, more recent tomographic studies have found asymmetry of the shear velocity structure beneath ridges in some areas, pointing to a smaller scale of active convection in the shallow mantle perhaps induced by melt retention buoyancy or the local effects of ridge/hotspot interaction.

  19. Landscapes of human evolution: models and methods of tectonic geomorphology and the reconstruction of hominin landscapes.

    Science.gov (United States)

    Bailey, Geoffrey N; Reynolds, Sally C; King, Geoffrey C P

    2011-03-01

    This paper examines the relationship between complex and tectonically active landscapes and patterns of human evolution. We show how active tectonics can produce dynamic landscapes with geomorphological and topographic features that may be critical to long-term patterns of hominin land use, but which are not typically addressed in landscape reconstructions based on existing geological and paleoenvironmental principles. We describe methods of representing topography at a range of scales using measures of roughness based on digital elevation data, and combine the resulting maps with satellite imagery and ground observations to reconstruct features of the wider landscape as they existed at the time of hominin occupation and activity. We apply these methods to sites in South Africa, where relatively stable topography facilitates reconstruction. We demonstrate the presence of previously unrecognized tectonic effects and their implications for the interpretation of hominin habitats and land use. In parts of the East African Rift, reconstruction is more difficult because of dramatic changes since the time of hominin occupation, while fossils are often found in places where activity has now almost ceased. However, we show that original, dynamic landscape features can be assessed by analogy with parts of the Rift that are currently active and indicate how this approach can complement other sources of information to add new insights and pose new questions for future investigation of hominin land use and habitats. Copyright © 2010 Elsevier Ltd. All rights reserved.

  20. The ultra low frequency electromagnetic radiation observed in the topside ionosphere above boundaries of tectonic plates

    Directory of Open Access Journals (Sweden)

    Michael A. Athanasiou

    2015-01-01

    Full Text Available In this paper we present results of a comparison between ultra low frequency (ULF electromagnetic (EM radiation, recorded by an electric field instrument onboard the satellite detection of electromagnetic emissions transmitted from earthquake regions in the topside ionosphere, and the seismicity of regions with high and low seismic activity. In particular, we evaluated the energy variations of the ULF Ezelectric field component during a period of four years (2006-2009, in order to examine the possible relation of ULF EM radiation with seismogenic regions located in Central America, Indonesia, the Eastern Mediterranean Basin and Greece. As a tool for evaluating the ULF Ez energy variations we used singular spectrum analysis techniques. The results of our analysis clearly show a significant increase of the ULF EM energy emitted from regions of highest seismic activity at the boundaries tectonic plates. Furthermore, we found that higher electromagnetic radiation was detected in a region above the northern- western Greek Arc (R1 than above the adjacent region including Athens and its urban area. We interpret these results of the present study as suggesting that: i the seismogenic regions at the boundary of tectonic plates radiate ULF EM emissions observed by satellites in the topside ionosphere; and ii that this EM radiation is not only related with the occurrence time of great (M≥5 earthquakes, but it is often present in intermediate times and it appears as a quasi-permanent phenomenon.

  1. Interaction between central volcanoes and regional tectonics along divergent plate boundaries: Askja, Iceland

    Science.gov (United States)

    Trippanera, Daniele; Ruch, Joël; Acocella, Valerio; Thordarson, Thor; Urbani, Stefano

    2018-01-01

    Activity within magmatic divergent plate boundaries (MDPB) focuses along both regional fissure swarms and central volcanoes. An ideal place to investigate their mutual relationship is the Askja central volcano in Iceland. Askja consists of three nested calderas (namely Kollur, Askja and Öskjuvatn) located within a hyaloclastite massif along the NNE-SSW trending Icelandic MDPB. We performed an extensive field-based structural analysis supported by a remote sensing study of tectonic and volcanic features of Askja's calderas and of the eastern flank of the hyaloclastite massif. In the massif, volcano-tectonic structures trend N 10° E to N 40° E, but they vary around the Askja caldera being both parallel to the caldera rim and cross-cutting on the Western side. Structural trends around the Öskjuvatn caldera are typically rim parallel. Volcanic vents and dikes are preferentially distributed along the caldera ring faults; however, they follow the NNE-SSW regional structures when located outside the calderas. Our results highlight that the Askja volcano displays a balanced amount of regional (fissure-swarm related) and local (shallow-magma-chamber related) tectonic structures along with a mutual interaction among these. This is different from Krafla volcano (to the north of Askja) dominated by regional structures and Grímsvötn (to the South) dominated by local structures. Therefore, Askja represents an intermediate tectono-magmatic setting for volcanoes located in a slow divergent plate boundary. This is also likely in accordance with a northward increase in the spreading rate along the Icelandic MDPB.

  2. Interaction between central volcanoes and regional tectonics along divergent plate boundaries: Askja, Iceland

    KAUST Repository

    Trippanera, Daniele

    2017-12-04

    Activity within magmatic divergent plate boundaries (MDPB) focuses along both regional fissure swarms and central volcanoes. An ideal place to investigate their mutual relationship is the Askja central volcano in Iceland. Askja consists of three nested calderas (namely Kollur, Askja and Öskjuvatn) located within a hyaloclastite massif along the NNE-SSW trending Icelandic MDPB. We performed an extensive field-based structural analysis supported by a remote sensing study of tectonic and volcanic features of Askja’s calderas and of the eastern flank of the hyaloclastite massif. In the massif, volcano-tectonic structures trend N 10° E to N 40° E, but they vary around the Askja caldera being both parallel to the caldera rim and cross-cutting on the Western side. Structural trends around the Öskjuvatn caldera are typically rim parallel. Volcanic vents and dikes are preferentially distributed along the caldera ring faults; however, they follow the NNE-SSW regional structures when located outside the calderas. Our results highlight that the Askja volcano displays a balanced amount of regional (fissure-swarm related) and local (shallow-magma-chamber related) tectonic structures along with a mutual interaction among these. This is different from Krafla volcano (to the north of Askja) dominated by regional structures and Grímsvötn (to the South) dominated by local structures. Therefore, Askja represents an intermediate tectono-magmatic setting for volcanoes located in a slow divergent plate boundary. This is also likely in accordance with a northward increase in the spreading rate along the Icelandic MDPB.

  3. Cenozoic intraplate tectonics in Central Patagonia: Record of main Andean phases in a weak upper plate

    Science.gov (United States)

    Gianni, G. M.; Echaurren, A.; Folguera, A.; Likerman, J.; Encinas, A.; García, H. P. A.; Dal Molin, C.; Valencia, V. A.

    2017-11-01

    Contraction in intraplate areas is still poorly understood relative to similar deformation at plate margins. In order to contribute to its comprehension, we study the Patagonian broken foreland (PBF) in South America whose evolution remains controversial. Time constraints of tectonic events and structural characterization of this belt are limited. Also, major causes of strain location in this orogen far from the plate margin are enigmatic. To unravel tectonic events, we studied the Cenozoic sedimentary record of the central sector of the Patagonian broken foreland (San Bernardo fold and thrust belt, 44°30‧S-46°S) and the Andes (Meseta de Chalia, 46°S) following an approach involving growth-strata detection, U-Pb geochronology and structural modeling. Additionally, we elaborate a high resolution analysis of the effective elastic thickness (Te) to examine the relation between intraplate contraction location and variations in lithospheric strength. The occurrence of Eocene growth-strata ( 44-40 Ma) suggests that contraction in the Andes and the Patagonian broken foreland was linked to the Incaic phase. Detection of synextensional deposits suggests that the broken foreland collapsed partially during Oligocene to early Miocene. During middle Miocene times, the Quechua contractional phase produced folding of Neogene volcanic rocks and olistostrome deposition at 17 Ma. Finally, the presented Te map shows that intraplate contraction related to Andean phases localized preferentially along weak lithospheric zones (Te < 15 km). Hence, the observed strain distribution in the PBF appears to be controlled by lateral variations in the lithospheric strength. Variations in this parameter could be related to thermo-mechanical weakening produced by intraplate rifting in Paleozoic-Mesozoic times.

  4. CAD-CAM plates versus conventional fixation plates for primary mandibular reconstruction: A biomechanical in vitro analysis.

    Science.gov (United States)

    Rendenbach, Carsten; Sellenschloh, Kay; Gerbig, Lucca; Morlock, Michael M; Beck-Broichsitter, Benedicta; Smeets, Ralf; Heiland, Max; Huber, Gerd; Hanken, Henning

    2017-11-01

    CAD/CAM reconstruction plates have become a viable option for mandible reconstruction. The aim of this study was to determine whether CAD/CAM plates provide higher fatigue strength compared with conventional fixation systems. 1.0 mm miniplates, 2.0 mm conventional locking plates (DePuy Synthes, Umkirch, Germany), and 2.0 mm CAD/CAM plates (Materialise, Leuven, Belgium/DePuy Synthes) were used to reconstruct a polyurethane mandible model (Synbone, Malans, CH) with cortical and cancellous bone equivalents. Mastication was simulated via cyclic dynamic testing using a universal testing machine (MTS, Bionix, Eden Prairie, MN, USA) until material failure reached a rate of 1 Hz with increasing loads on the left side. No significant difference was found between the groups until a load of 300 N. At higher loads, vertical displacement differed increasingly, with a poorer performance of miniplates (p = 0.04). Plate breakage occurred in miniplates and conventional locking plates. Screw breakage was recorded as the primary failure mechanism in CAD/CAM plates. Stiffness was significantly higher with the CAD/CAM plates (p = 0.04). CAD/CAM plates and reconstruction plates provide higher fatigue strength than miniplates, and stiffness is highest in CAD/CAM systems. All tested fixation methods seem sufficiently stable for mandible reconstruction. Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  5. Reconstructing mantle heterogeneity with data assimilation based on the back-and-forth nudging method: Implications for mantle-dynamic fitting of past plate motions

    Science.gov (United States)

    Glišović, Petar; Forte, Alessandro

    2016-04-01

    The paleo-distribution of density variations throughout the mantle is unknown. To address this question, we reconstruct 3-D mantle structure over the Cenozoic era using a data assimilation method that implements a new back-and-forth nudging algorithm. For this purpose, we employ convection models for a compressible and self-gravitating mantle that employ 3-D mantle structure derived from joint seismic-geodynamic tomography as a starting condition. These convection models are then integrated backwards in time and are required to match geologic estimates of past plate motions derived from marine magnetic data. Our implementation of the nudging algorithm limits the difference between a reconstruction (backward-in-time solution) and a prediction (forward-in-time solution) on over a sequence of 5-million-year time windows that span the Cenozoic. We find that forward integration of reconstructed mantle heterogeneity that is constrained to match past plate motions delivers relatively poor fits to the seismic-tomographic inference of present-day mantle heterogeneity in the upper mantle. We suggest that uncertainties in the past plate motions, related for example to plate reorganization episodes, could partly contribute to the poor match between predicted and observed present-day heterogeneity. We propose that convection models that allow tectonic plates to evolve freely in accord with the buoyancy forces and rheological structure in the mantle could provide additional constraints on geologic estimates of paleo-configurations of the major tectonic plates.

  6. 3-D Simulation of Tectonic Evolution in Mariana with a Coupled Model of Plate Subduction and Back-Arc Spreading

    Science.gov (United States)

    Hashima, A.; Matsu'Ura, M.

    2006-12-01

    We obtained the expressions for internal deformation fields due to a moment tensor in an elastic-viscoelastic layered holf-space. This unified formulation of internal deformation fields for shear faulting and crack opening enabled us to deal with the problem of tectonic deformation at a composite type of plate boundary zones. The tectonic deformation can be ascribed to mechanical interaction at plate boundaries, which make a closed circuit with the mode of relative plate motion changing from divergence to convergence through transcurrent motion. One of the rational ways to represent mechanical interaction at plate boundaries is specifying the increase rates of normal or tangential displacement discontinuity across plate interfaces. On the basis of such a basic idea we developed a 3-D simulation model for the nonlinear, coupled system of plate subduction and back-arc spreading in Mariana. Through numerical simulations we revealed the evolution process of back-arc spreading. At the first stage, steady plate subduction (shear faulting at a plate interface) gradually forms tensile stress fields in the back-arc region of the overriding plate. When the accumulated tensile stress reaches a critical level, back-arc spreading (crack opening) starts at a structurally weak portion of the overriding plate. The horizontal motion of the frontal part of the overriding plate due to back-arc spreading pushes out the plate boundary toward the oceanic plate. In steady-state plate subduction the shear stress acting on a plate interface must balance with the maximum frictional resistance (shear strength) of the plate interface. Therefore, the increase of shear stress at the plate interface leads to the increase of slip rate at the plate interface. The local increase of slip rate at the plate interface produces the additional tensile stress in the back-arc region. The increased tensile stress must be canceled out by the additional crack opening. Such a feedback mechanism between plate

  7. A harbinger of plate tectonics: a commentary on Bullard, Everett and Smith (1965) ‘The fit of the continents around the Atlantic’

    Science.gov (United States)

    Dewey, John F.

    2015-01-01

    In the 1960s, geology was transformed by the paradigm of plate tectonics. The 1965 paper of Bullard, Everett and Smith was a linking transition between the theories of continental drift and plate tectonics. They showed, conclusively, that the continents around the Atlantic were once contiguous and that the Atlantic Ocean had grown at rates of a few centimetres per year since the Early Jurassic, about 160 Ma. They achieved fits of the continental margins at the 500 fathom line (approx. 900 m), not the shorelines, by minimizing misfits between conjugate margins and finding axes, poles and angles of rotation, using Euler's theorem, that defined the unique single finite difference rotation that carried congruent continents from contiguity to their present positions, recognizing that the real motion may have been more complex around a number of finite motion poles. Critically, they were concerned only with kinematic reality and were not restricted by considerations of the mechanism by which continents split and oceans grow. Many of the defining features of plate tectonics were explicit or implicit in their reconstructions, such as the torsional rigidity of continents, Euler's theorem, closure of the Tethyan ocean(s), major continental margin shear zones, the rapid rotation of small continental blocks (Iberia) around nearby poles, the consequent opening of small wedge-shaped oceans (Bay of Biscay), and misfit overlaps (deltas and volcanic piles) and underlaps (stretched continental edges). This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750142

  8. Geodynamics of kimberlites on a cooling Earth: Clues to plate tectonic evolution and deep volatile cycles

    Science.gov (United States)

    Tappe, Sebastian; Smart, Katie; Torsvik, Trond; Massuyeau, Malcolm; de Wit, Mike

    2018-02-01

    Kimberlite magmatism has occurred in cratonic regions on every continent. The global age distribution suggests that this form of mantle melting has been more prominent after 1.2 Ga, and notably between 250-50 Ma, than during early Earth history before 2 Ga (i.e., the Paleoproterozoic and Archean). Although preservation bias has been discussed as a possible reason for the skewed kimberlite age distribution, new treatment of an updated global database suggests that the apparent secular evolution of kimberlite and related CO2-rich ultramafic magmatism is genuine and probably coupled to lowering temperatures of Earth's upper mantle through time. Incipient melting near the CO2- and H2O-bearing peridotite solidus at >200 km depth (1100-1400 °C) is the petrologically most feasible process that can produce high-MgO carbonated silicate melts with enriched trace element concentrations akin to kimberlites. These conditions occur within the convecting asthenospheric mantle directly beneath thick continental lithosphere. In this transient upper mantle source region, variable CHO volatile mixtures control melting of peridotite in the absence of heat anomalies so that low-degree carbonated silicate melts may be permanently present at ambient mantle temperatures below 1400 °C. However, extraction of low-volume melts to Earth's surface requires tectonic triggers. Abrupt changes in the speed and direction of plate motions, such as typified by the dynamics of supercontinent cycles, can be effective in the creation of lithospheric pathways aiding kimberlite magma ascent. Provided that CO2- and H2O-fluxed deep cratonic keels, which formed parts of larger drifting tectonic plates, existed by 3 Ga or even before, kimberlite volcanism could have been frequent during the Archean. However, we argue that frequent kimberlite magmatism had to await establishment of an incipient melting regime beneath the maturing continents, which only became significant after secular mantle cooling to below

  9. Miocene uplift of the NE Greenland margin linked to plate tectonics: Seismic evidence from the Greenland Fracture Zone, NE Atlantic

    DEFF Research Database (Denmark)

    Døssing Andreasen, Arne; Japsen, Peter; Watts, Anthony B.

    2016-01-01

    Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses to ...... by plate tectonic forces, induced perhaps by a change in the Iceland plume (a hot pulse) and/or by changes in intra-plate stresses related to global tectonics.......Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses...... backstripping. We explain the thermo-mechanical coupling and the deposition of contourites by the formation of a continuous plate boundary along the Mohns and Knipovich ridges, leading to an accelerated widening of the Fram Strait. We demonstrate that the IMU event is linked to onset of uplift and massive shelf...

  10. Fission track thermochronology : reconstructing the thermal and tectonic evolution of the crust

    International Nuclear Information System (INIS)

    Gleadow, A.J.W.

    1990-01-01

    The basis and current status of fission track analysis is reviewed showing the kinds of patterns of fission track parameters which result from a variety of thermal and tectonic histories. Fission track thermochronology is a well established method for reconstructing the thermal histories of rocks with particularly important applications in tectonic studies. Quantitative modelling of the thermal annealing of tracks in apatite shows that distinctive profiles of apparent fission track age can be related to a number of simple thermal history styles. The main types of profiles observed tend to be either an essentially linear decrease of apparent age with increasing depth, which relates to continuous uplift and denudation, or a concave-upwards profile produced by partial annealing in environments of tectonic stability or burial. More complex thermal histories produce compound profiles which are essentially just combinations of these two elements. Track length information allows the apparent age profiles to be interpreted in much greater detail. Examples of the major profile types have been identified in various geological environments and can be analysed to give information about, for example, uplift and denudation rates, the timing of uplift or low-grade thermal events and maximum palaeotemperatures experienced during burial. 25 refs., 8 figs

  11. From Dearth to El Dorado: Andean Nature, Plate Tectonics, and the Ontologies of Ecuadorian Resource Wealth

    Directory of Open Access Journals (Sweden)

    David Kneas

    2018-03-01

    Full Text Available Since the early 1990s, the Ecuadorian government has pledged to convert the nation into a “mining country” of global standing. Contemporary claims of mineral wealth, however, stand in stark contrast to previous assessments. Indeed, through much of the 20th century, geologists described Ecuador as a country of mineral dearth. Exploring the process through which Ecuador seemingly transitioned from a nation of resource scarcity to one of mineral plenty, I demonstrate how assessments of Ecuador’s resource potential relate to ideas of Andean nature. Promoters of resource abundance have emphasized Andean uniformity and equivalence—the notion that Ecuador’s mineral wealth is inevitable by virtue of the resource richness of its Andean neighbors. Geologists who have questioned Ecuador’s mineral content, on the other hand, have emphasized Andean heterogeneity. In the recent promotion of Ecuador’s resource potential, notions of Andean uniformity have been bolstered by models of subsoil copper that emerged in the in 1970s in the context of plate-tectonic theory. In highlighting the linkage between ideas of Andean nature and appraisals of Ecuadorian resource potential since the late 19th century, I outline the dialectics between nature and natural resources that underpin processes of resource becoming.

  12. Seismic potential of weak, near-surface faults revealed at plate tectonic slip rates.

    Science.gov (United States)

    Ikari, Matt J; Kopf, Achim J

    2017-11-01

    The near-surface areas of major faults commonly contain weak, phyllosilicate minerals, which, based on laboratory friction measurements, are assumed to creep stably. However, it is now known that shallow faults can experience tens of meters of earthquake slip and also host slow and transient slip events. Laboratory experiments are generally performed at least two orders of magnitude faster than plate tectonic speeds, which are the natural driving conditions for major faults; the absence of experimental data for natural driving rates represents a critical knowledge gap. We use laboratory friction experiments on natural fault zone samples at driving rates of centimeters per year to demonstrate that there is abundant evidence of unstable slip behavior that was not previously predicted. Specifically, weak clay-rich fault samples generate slow slip events (SSEs) and have frictional properties favorable for earthquake rupture. Our work explains growing field observations of shallow SSE and surface-breaking earthquake slip, and predicts that such phenomena should be more widely expected.

  13. Emergence of silicic continents as the lower crust peels off on a hot plate-tectonic Earth

    Science.gov (United States)

    Chowdhury, Priyadarshi; Gerya, Taras; Chakraborty, Sumit

    2017-09-01

    The rock record and geochemical evidence indicate that continental recycling has been occurring since the early history of the Earth. The stabilization of felsic continents in place of Earth's early mafic crust about 3.0 to 2.0 billion years ago, perhaps due to the initiation of plate tectonics, implies widespread destruction of mafic crust during this time interval. However, the physical mechanisms of such intense recycling on a hotter, (late) Archaean and presumably plate-tectonic Earth remain largely unknown. Here we use thermomechanical modelling to show that extensive recycling via lower crustal peeling-off (delamination but not eclogitic dripping) during continent-continent convergence was near ubiquitous during the late Archaean to early Proterozoic. We propose that such destruction of the early mafic crust, together with felsic magmatism, may have caused both the emergence of silicic continents and their subsequent isostatic rise, possibly above the sea level. Such changes in the continental character have been proposed to influence the Great Oxidation Event and, therefore, peeling-off plate tectonics could be the geodynamic trigger for this event. A transition to the slab break-off controlled syn-orogenic recycling occurred as the Earth aged and cooled, leading to reduced recycling and enhanced preservation of the continental crust of present-day composition.

  14. A planet in transition: The onset of plate tectonics on Earth between 3 and 2 Ga?

    Directory of Open Access Journals (Sweden)

    Kent C. Condie

    2018-01-01

    Full Text Available Many geological and geochemical changes are recorded on Earth between 3 and 2 Ga. Among the more important of these are the following: (1 increasing proportion of basalts with “arc-like” mantle sources; (2 an increasing abundance of basalts derived from enriched (EM and depleted (DM mantle sources; (3 onset of a Great Thermal Divergence in the mantle; (4 a decrease in degree of melting of the mantle; (5 beginning of large lateral plate motions; (6 appearance of eclogite inclusions in diamonds; (7 appearance and rapid increase in frequency of collisional orogens; (8 rapid increase in the production rate of continental crust as recorded by zircon age peaks; (9 appearance of ophiolites in the geologic record, and (10 appearance of global LIP (large igneous province events some of which correlate with global zircon age peaks. All of these changes may be tied directly or indirectly to cooling of Earth's mantle and corresponding changes in convective style and the strength of the lithosphere, and they may record the gradual onset and propagation of plate tectonics around the planet. To further understand the changes that occurred between 3 and 2 Ga, it is necessary to compare rocks, rock associations, tectonics and geochemistry during and between zircon age peaks. Geochemistry of peak and inter-peak basalts and TTGs needs to be evaluated in terms of geodynamic models that predict the existence of an episodic thermal regime between stagnant-lid and plate tectonic regimes in early planetary evolution.

  15. A harbinger of plate tectonics: a commentary on Bullard, Everett and Smith (1965) ?The fit of the continents around the Atlantic?

    OpenAIRE

    Dewey, John F.

    2015-01-01

    In the 1960s, geology was transformed by the paradigm of plate tectonics. The 1965 paper of Bullard, Everett and Smith was a linking transition between the theories of continental drift and plate tectonics. They showed, conclusively, that the continents around the Atlantic were once contiguous and that the Atlantic Ocean had grown at rates of a few centimetres per year since the Early Jurassic, about 160?Ma. They achieved fits of the continental margins at the 500 fathom line (approx. 900?m),...

  16. Towards absolute plate motions constrained by lower-mantle slab remnants

    NARCIS (Netherlands)

    Meer, D.G. van der; Spakman, W.; Hinsbergen, D.J.J. van; Amaru, M.L.; Torsvik, T.H.

    2010-01-01

    Since the first reconstruction of the supercontinent Pangaea, key advances in plate tectonic reconstructions have been made1. Although the movement of tectonic plates since the start of the mid-Cretaceous period (~100 million years (Myr) ago) is relatively well understood1, 2, the longitudinal

  17. Global crustal movement and tectonic plate boundary deformation constrained by the ITRF2008

    Directory of Open Access Journals (Sweden)

    Zhu Ze

    2012-08-01

    Full Text Available On the basis of the newly released International Terrestrial Reference Frame(ITRF2008 by the International Earth Rotation Service (IERS, a new global plate model ITRF2008 plate for the major plates is established. This ITRF2008-derived model is analyzed in comparison with NNR-NUVEL1A model, which is mainly based on geological and geophysical data. The Eurasia and Pacific plates display obvious differences in terms of the velocity fields derived from the two plate motion models. Plate acceleration is also introduced to characterize the differences of the two velocity fields which obtained from ITRF2008 -plate and NNR-NUVEL1A models for major individual plates. The results show that the Africa, South America and Eurasia plates are undergoing acceleration, while the North America and Australia plates are in the state of deceleration motion.

  18. Archean greenstone-tonalite duality: Thermochemical mantle convection models or plate tectonics in the early Earth global dynamics?

    Science.gov (United States)

    Kerrich, Robert; Polat, Ali

    2006-03-01

    Mantle convection and plate tectonics are one system, because oceanic plates are cold upper thermal boundary layers of the convection cells. As a corollary, Phanerozoic-style of plate tectonics or more likely a different version of it (i.e. a larger number of slowly moving plates, or similar number of faster plates) is expected to have operated in the hotter, vigorously convecting early Earth. Despite the recent advances in understanding the origin of Archean greenstone-granitoid terranes, the question regarding the operation of plate tectonics in the early Earth remains still controversial. Numerical model outputs for the Archean Earth range from predominantly shallow to flat subduction between 4.0 and 2.5 Ga and well-established steep subduction since 2.5 Ga [Abbott, D., Drury, R., Smith, W.H.F., 1994. Flat to steep transition in subduction style. Geology 22, 937-940], to no plate tectonics but rather foundering of 1000 km sectors of basaltic crust, then "resurfaced" by upper asthenospheric mantle basaltic melts that generate the observed duality of basalts and tonalities [van Thienen, P., van den Berg, A.P., Vlaar, N.J., 2004a. Production and recycling of oceanic crust in the early earth. Tectonophysics 386, 41-65; van Thienen, P., Van den Berg, A.P., Vlaar, N.J., 2004b. On the formation of continental silicic melts in thermochemical mantle convection models: implications for early Earth. Tectonophysics 394, 111-124]. These model outputs can be tested against the geological record. Greenstone belt volcanics are composites of komatiite-basalt plateau sequences erupted from deep mantle plumes and bimodal basalt-dacite sequences having the geochemical signatures of convergent margins; i.e. horizontally imbricated plateau and island arc crust. Greenstone belts from 3.8 to 2.5 Ga include volcanic types reported from Cenozoic convergent margins including: boninites; arc picrites; and the association of adakites-Mg andesites- and Nb-enriched basalts. Archean cratons

  19. Patient-specific reconstruction plates are the missing link in computer-assisted mandibular reconstruction: A showcase for technical description.

    Science.gov (United States)

    Cornelius, Carl-Peter; Smolka, Wenko; Giessler, Goetz A; Wilde, Frank; Probst, Florian A

    2015-06-01

    Preoperative planning of mandibular reconstruction has moved from mechanical simulation by dental model casts or stereolithographic models into an almost completely virtual environment. CAD/CAM applications allow a high level of accuracy by providing a custom template-assisted contouring approach for bone flaps. However, the clinical accuracy of CAD reconstruction is limited by the use of prebent reconstruction plates, an analogue step in an otherwise digital workstream. In this paper the integration of computerized, numerically-controlled (CNC) milled, patient-specific mandibular plates (PSMP) within the virtual workflow of computer-assisted mandibular free fibula flap reconstruction is illustrated in a clinical case. Intraoperatively, the bone segments as well as the plate arms showed a very good fit. Postoperative CT imaging demonstrated close approximation of the PSMP and fibular segments, and good alignment of native mandible and fibular segments and intersegmentally. Over a follow-up period of 12 months, there was an uneventful course of healing with good bony consolidation. The virtual design and automated fabrication of patient-specific mandibular reconstruction plates provide the missing link in the virtual workflow of computer-assisted mandibular free fibula flap reconstruction. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  20. Dynamic Error Analysis Method for Vibration Shape Reconstruction of Smart FBG Plate Structure

    Directory of Open Access Journals (Sweden)

    Hesheng Zhang

    2016-01-01

    Full Text Available Shape reconstruction of aerospace plate structure is an important issue for safe operation of aerospace vehicles. One way to achieve such reconstruction is by constructing smart fiber Bragg grating (FBG plate structure with discrete distributed FBG sensor arrays using reconstruction algorithms in which error analysis of reconstruction algorithm is a key link. Considering that traditional error analysis methods can only deal with static data, a new dynamic data error analysis method are proposed based on LMS algorithm for shape reconstruction of smart FBG plate structure. Firstly, smart FBG structure and orthogonal curved network based reconstruction method is introduced. Then, a dynamic error analysis model is proposed for dynamic reconstruction error analysis. Thirdly, the parameter identification is done for the proposed dynamic error analysis model based on least mean square (LMS algorithm. Finally, an experimental verification platform is constructed and experimental dynamic reconstruction analysis is done. Experimental results show that the dynamic characteristics of the reconstruction performance for plate structure can be obtained accurately based on the proposed dynamic error analysis method. The proposed method can also be used for other data acquisition systems and data processing systems as a general error analysis method.

  1. Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria)

    Czech Academy of Sciences Publication Activity Database

    Briestenský, Miloš; Rowberry, Matthew David; Stemberk, Josef; Stefanov, P.; Vozár, J.; Šebela, S.; Petro, L.; Bella, P.; Gaal, L.; Ormukov, Ch.

    2015-01-01

    Roč. 66, č. 5 (2015), s. 427-438 ISSN 1335-0552 R&D Projects: GA MŠk LM2010008; GA MŠk OC 625.10; GA ČR GA205/05/2770; GA ČR GA205/06/1828; GA ČR GA205/09/2024 Institutional support: RVO:67985891 Keywords : Eurasian Plate * Balkan Peninsula * active tectonics research * aseismic transient deformations * slow-slip phenomena Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.523, year: 2015 http://www.geologicacarpathica.com/browse-journal/volumes/66-5/article-780

  2. Accuracy of fibula reconstruction using patient-specific CAD/CAM reconstruction plates and dental implants : A new modality for functional reconstruction of mandibular defects

    NARCIS (Netherlands)

    Schepers, Rutger H.; Raghoebar, Gerry M.; Vissink, Arjan; Stenekes, Martin W.; Kraeima, Joep; Roodenburg, Jan L.; Reintsema, Harry; Witjes, Max J.

    Background: The purpose of this study was to analyze the accuracy of mandibular reconstruction using patient-specific computer-aided designed and computer-aided manufactured (CAD/CAM) reconstruction plates as a guide to place fibula grafts and dental implants in a one-stage procedure using

  3. Segmentation of the eastern North Greenland oblique-shear margin – regional plate tectonic implications

    DEFF Research Database (Denmark)

    Andreasen, Arne Døssing; Stemmerik, Lars; Dahl-Jensen, T.

    2010-01-01

    a highly complex, Paleozoic–early Cenozoic pre-opening setting. However, due to extreme ice conditions, very little is known about the offshore areas seawards of – and between – the peninsulas. Consequently, prevailing structural-tectonic models of the margin tend to be significantly oversimplified...... anticipated. In particular, we interpret strong margin segmentation along N/NE-striking fault structures. The structures are likely to have formed by Late Mesozoic–early Cenozoic strike-slip tectonics and have continued to be active during the late Cenozoic. A more than 8 km deep sedimentary basin...

  4. Orogenesis of the Oman Mountains - a new geodynamic model based on structural geology, plate reconstructions and thermochronology

    Science.gov (United States)

    Grobe, Arne; Virgo, Simon; von Hagke, Christoph; Ralf, Littke; Urai, Janos L.

    2017-04-01

    faults on the northern flank of the anticline. We link these results with the geodynamic framework of the area, constrained by plate tectonic reconstructions. Furthermore, we constrain the exhumation history of the mountain belt using zircon (U-Th-Sm)/He dating. Geodynamic and exhumation events can be linked to structural generations. This results in a new tectonic model of the Oman Mountains. We find a remarkable along-strike consistency of mountain building phases and argue involvement of a micro-plate is not required. Breton, J.P., Béchennec, F., Le Métour, J., Moen-Maurel, L., Razin, P., 2004. Eoalpine (Cretaceous) evolution of the Oman Tethyan continental margin: Insights from a structural field study in Jabal Akhdar (Oman Mountains). GeoArabia 9, 41-58. Fink, R., Virgo, S., Arndt, M., Visser, W., Littke, R., Urai, J.L.L., 2015. Solid bitumen in calcite veins from the Natih Formation in the Oman Mountains: Multiple phases of petroleum migration in a changing stress field. Int. J. Coal Geol. 157, 39-51. doi:10.1016/j.coal.2015.07.012 Grobe, A., Urai, J.L.L., Littke, R., Lünsdorf, N.K.K., 2016. Hydrocarbon generation and migration under a large overthrust: The carbonate platform under the Semail Ophiolite, Jebel Akhdar, Oman. Int. J. Coal Geol. 1-17. doi:10.1016/j.coal.2016.02.007

  5. Deciphering detailed plate kinematics of the Indian Ocean and developing a unified model for East Gondwanaland reconstruction: An Indian-Australian-French initiative

    Digital Repository Service at National Institute of Oceanography (India)

    Yatheesh, V.; Dyment, J.; Bhattacharya, G.C.; Muller, R.D.

    The Indian Ocean formed as a result of the fragmentation and dispersal of Gondwanaland since the Jurassic. The deep ocean basins in the Indian Ocean contain the imprints of this plate tectonic history, which is related with several major tectonic...

  6. 3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments

    Directory of Open Access Journals (Sweden)

    D. Boutelier

    2011-05-01

    Full Text Available We present an experimental apparatus for 3-D thermo-mechanical analogue modeling of plate tectonic processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic analogue materials with strain softening, is submitted to a constant temperature gradient causing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry. Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and adjusted via the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.

  7. A comparative study on the customized design of mandibular reconstruction plates using finite element method

    Directory of Open Access Journals (Sweden)

    Abdulrahman Al-Ahmari

    2015-07-01

    Full Text Available Mandible defects and its deformities are serious complications and its precise reconstruction is one of the most challenging tasks in oral maxillofacial surgery. The commercially available standard mandible implants are manually bended before surgery to custom fit the patient’s jaw. A slight mismatch in the plate and bone alignment may result in the implant failure. However, with the integration of computer-aided design, rapid prototyping, and advanced imaging systems (computed tomography or magnetic resonance imaging, it is possible to produce a customized mandible implant that can precisely fit the patient’s jaw. The aim of this article is to compare a new design of customized mandible implant (sinewave plate and compare it with the commonly used straight implant design. The finite element–simulated results reveal that the commonly used straight reconstruction plates are more prone to loosening of the screws due to its higher strain concentration on the screw hole when compared to newly designed sinewave reconstruction plate. Moreover, the straight plate is more sensitive to the chewing load variations and develops almost 20% increase in the stresses when compared to sinewave plate. The study reveals that the sinewave reconstruction plate can significantly enhance the stability and safety of the mandible implant.

  8. Reconstruction of the nasal septum using polydioxanone plate

    NARCIS (Netherlands)

    Boenisch, Miriam; Nolst Trenité, Gilbert J.

    2010-01-01

    To evaluate the usefulness of resorbable polydioxanone plate attached to nasal septal cartilage in external septoplasty, to assess its mechanical stability until healing of cartilage fragments, and to describe the surgical technique and clinical experience. External septoplasty with polydioxanone

  9. Comparative study of W-shaped angular plate and reconstruction plate in treating posterior wall fractures of the acetabulum.

    Directory of Open Access Journals (Sweden)

    Qi Zhang

    Full Text Available OBJECTIVE: This study aims to assess the medium-term results of the reconstruction of posterior wall fractures using a W-shaped acetabular angular plate (WAAP compared to those fixed using a reconstruction plate. METHODS: Between July 2006 and March 2009, we performed a retrospective study, which collected data for any patient treated for a posterior acetabular wall fracture. At the time of treatment, patients were either treated using a WAAP or a pelvic reconstruction plate. The intraoperative fluoroscopic images for both groups were compared. The quality of reduction and radiological grading were assessed according to the criteria developed by Matta. The clinical assessment was based on a modified Merle d'Aubigne and Postel scoring. RESULTS: 53 patients met the inclusion criteria and were followed up for an average of 38 months. 25 patients were treated with a WAAP (study group, and 28 patients were treated with a pelvic reconstruction plate (control group. The intraoperative fluoroscopic images of the study group confirmed extra-articular screw placement in all cases. In the control group, intra-articular screw placement was observed intraoperatively in 5 patients (17.86%, and the definitive location of the periarticular hardware could not be determined in 4 patients (14.29% during the operation. The differences between the two groups were statistically significant (p = 0.002. In contrast, the quality of fracture reduction, clinical outcomes, and radiological grading in the study group were not significantly different from those of the control group (p>0.05. The radiographic grade was strongly associated with the clinical outcomes in both the study and control groups (p<0.05. CONCLUSION: Reconstruction of posterior wall fractures of the acetabulum using a WAAP can help avoid screw penetration of the hip joint, provide a stable fixation of the posterior wall, and ensure good clinical outcomes.

  10. Paleomagnetic tests of tectonic reconstructions of the India-Asia collision zone

    Science.gov (United States)

    Huang, Wentao; Hinsbergen, Douwe J. J.; Lippert, Peter C.; Guo, Zhaojie; Dupont-Nivet, Guillaume

    2015-04-01

    Several solutions have been proposed to explain the long-standing kinematic observation that postcollisional upper crustal shortening within the Himalaya and Asia is much less than the magnitude of India-Asia convergence. Here we implement these hypotheses in global plate reconstructions and test paleolatitudes predicted by the global apparent polar wander path against independent, and the most robust paleomagnetic data. Our tests demonstrate that (1) reconstructed 600-750 km postcollisional intra-Asian shortening is a minimum value; (2) a 52 Ma collision age is only consistent with paleomagnetic data if intra-Asian shortening was ~900 km; a ~56-58 Ma collision age requires greater intra-Asian shortening; (3) collision ages of 34 or 65 Ma incorrectly predict Late Cretaceous and Paleogene paleolatitudes of the Tibetan Himalaya (TH); and (4) Cretaceous counterclockwise rotation of India cannot explain the paleolatitudinal divergence between the TH and India. All hypotheses, regardless of collision age, require major Cretaceous extension within Greater India.

  11. Plate-Tectonic Circulation is Driven by Cooling From the Top and is Closed Within the Upper Mantle

    Science.gov (United States)

    Hamilton, W. B.

    2001-12-01

    Subduction drives plate tectonics and is due to cooling from the top: circulation is self-organized, and likely is closed above the discontinuity near 660 km. The contrary consensus that plate tectonics is driven by bottom heating and involves the entire mantle combines misunderstood kinematics with flawed concepts of through-the-mantle plumes and subduction. Plume conjecture came from the Emperor-Hawaii progression, the 45 Ma inflection in which was assumed to mark a 60-degree change in direction of that part of the Pacific plate over a fixed plume. Smooth spreading patterns around the east and south margin of the Pacific plate, and paleomagnetic data, disprove such a change. Speculations that plumes move, jump, etc. do not revive falsified conjecture. Geochemical distinctions between enriched island and depleted ridge basalts (which overlap) are expected products of normal upper-mantle processes, not plumes. MORB traverses solidus-T asthenosphere, whereas OIB zone-refines through subsolidus lithosphere and crust, crystallizing refractories to retain T of diminishing melt while assimilating and retaining fusibles. Tomographic inference of deep-mantle subduction is presented misleadingly and may reflect methodological and sampling artifacts (downward smearing, and concentration of recorded body waves in bundles within broad anomalies otherwise poorly sampled). Planetological and other data require hot Earth accretion, and thorough early fractionation, from material much more refractory than primitive meteorites, and are incompatible with the little-fractionated lower mantle postulated to permit whole-mantle circulation. The profound seismic discontinuity near 660 km is a thermodynamic and physical barrier to easy mass transfer in either direction. Refractory lower mantle convects slowly, perhaps in layers, and loses primarily original heat, whereas upper mantle churns rapidly, and the 660 decoupling boundary must have evolved into a compositional barrier also

  12. Impact of uncertain reference-frame motions in plate kinematic reconstructions

    DEFF Research Database (Denmark)

    Iaffaldano, Giampiero; Stein, Seth

    2017-01-01

    Geoscientists infer past plate motions, which serve as fundamental constraints for a range of studies, from observations of magnetic isochrons as well as hotspots tracks on the ocean floor and, for stages older than the Cretaceous, from paleomagnetic data. These observations effectively represent...... time-integrals of past plate motions but, because they are made at present, yield plate kinematics naturally tied to a present-day reference-frame, which may be another plate or a hotspots system. These kinematics are therefore different than those occurred at the time when the rocks acquired...... – in a temporal sense – and prone to noise. This limitation is commonly perceived to hamper the correction of plate kinematic reconstructions for RFAMs, but the extent to which this may be the case has not been explored. Here we assess the impact of uncertain RFAMs on kinematic reconstructions using synthetic...

  13. Faunal breaks and species composition of Indo-Pacific corals: the role of plate tectonics, environment and habitat distribution

    Science.gov (United States)

    Keith, S. A.; Baird, A. H.; Hughes, T. P.; Madin, J. S.; Connolly, S. R.

    2013-01-01

    Species richness gradients are ubiquitous in nature, but the mechanisms that generate and maintain these patterns at macroecological scales remain unresolved. We use a new approach that focuses on overlapping geographical ranges of species to reveal that Indo-Pacific corals are assembled within 11 distinct faunal provinces. Province limits are characterized by co-occurrence of multiple species range boundaries. Unexpectedly, these faunal breaks are poorly predicted by contemporary environmental conditions and the present-day distribution of habitat. Instead, faunal breaks show striking concordance with geological features (tectonic plates and mantle plume tracks). The depth range over which a species occurs, its larval development rate and genus age are important determinants of the likelihood that species will straddle faunal breaks. Our findings indicate that historical processes, habitat heterogeneity and species colonization ability account for more of the present-day biogeographical patterns of corals than explanations based on the contemporary distribution of reefs or environmental conditions. PMID:23698011

  14. Application of plate tectonics to the location of new mineral targets in the Appalachians. Progress report no. 3

    International Nuclear Information System (INIS)

    Kutina, J.

    1979-01-01

    This report is concerned with the application of plate tectonics to the location of new mineral targets in the U.S. It reviews analyses presented in previous reports which suggest that the basement of the Central and Eastern U.S. consists of large crustal blocks separated by major zones of tectonic weakness. The curvature of the Appalachian Fold Belt appears to be related to the east-west boundaries caused by subsiding and uplifting at these zones. A plot of epigenetic uranium occurrences reveals that they tend to cluster along the greater curvatures of the Appalachian orogeny. These findings have led to a systematic study of the regularities in the distribution of ore deposits in the Appalachians presented in this report. They include a description of geologic and geographic base maps, preparation of maps showing distribution of individual minerals, and regularities in the distribution of uranium in the Appalachians. Comments on the segmentation of the Appalachian orogeny by transverse lineaments are presented. The report contains seventeen maps of the eastern half of the U.S. showing specific mineral deposits in relation to geologic formations

  15. Preputial reconstruction and tubularized incised plate urethroplasty in proximal hypospadias with ventral penile curvature

    OpenAIRE

    Bhat, Amilal; Gandhi, Ajay; Saxena, Gajendra; Choudhary, Gautam Ram

    2010-01-01

    Aims : Objective of this study was to assess the feasibility and results of preputial reconstruction and tubularized incised plate urethroplasty (TIP) in patients of proximal hypospadias with ventral penile curvature. Materials and Methods : Twenty-seven patients of proximal hypospadias who underwent preputioplasty with TIP were evaluated retrospectively. Ventral curvature was corrected by mobilization of the urethral plate with the corpus spongiosum and the proximal urethra; dorsal plica...

  16. Comparison of conventional reconstruction plate versus direct metal laser sintering plate: an in vitro mechanical characteristics study.

    Science.gov (United States)

    Xie, Pusheng; Ouyang, Hanbin; Deng, Yuping; Yang, Yang; Xu, Jing; Huang, Wenhua

    2017-09-02

    Additive manufacturing (AM) technology has helped to achieve several advances in the medical field, particularly as far as fabrication of implants is concerned. But the application of direct metal laser sintering (DMLS) bone plate is quite limited due to the indeterminate mechanical property. The purposes of this study were to characterize the biomechanical properties of the polished DMLS reconstruction plate and to compare these with the properties of commonly applied implants and to find whether the mechanical performance of DMLS plate meets the requirements for clinical application. In this study, we fabricated two groups of plates by DMLS and computer numerical control (CNC) techniques. After that, we polished all samples and investigated their roughness, components, hardness, static bending, and torsional performance. Moreover, cyclic bending tests and fractographic analysis were conducted. Statistical comparisons of the group by means of monotonic test data were made, and a qualitative comparison was performed to assess failures in fatigue. We found no differences in surface roughness or components after polishing, but the DMLS plate hardness is 7.42% (p direct application of these AM instruments in the operating room requires further validation including animal and clinical experiment.

  17. Rotational inertia of continents: A proposed link between polar wandering and plate tectonics

    Science.gov (United States)

    Kane, M.F.

    1972-01-01

    A mechanism is proposed whereby displacement between continents and the earth's pole of rotation (polar wandering) gives rise to latitudinal transport of continental plates (continental drift) because of their relatively greater rotational inertia. When extended to short-term polar wobble, the hypothesis predicts an energy change nearly equivalent to the seismic energy rate.

  18. Health-related quality of life after segmental resection of the lateral mandible: Free fibula flap versus plate reconstruction.

    Science.gov (United States)

    van Gemert, Johannes; Holtslag, Irene; van der Bilt, Andries; Merkx, Matthias; Koole, Ron; Van Cann, Ellen

    2015-06-01

    Segmental resection of the mandible causes functional, aesthetic and social problems affecting health-related quality of life (HRQoL). It is often assumed that reconstruction with composite free flaps guarantees better function and aesthetics than bridging the defect with reconstruction plates. Using the European Organization for Research and Treatment of Cancer questionnaires (EORTC QLQ-C30 version 3.0 and EORTC QLQ-H&N35), we compared HRQoL in patients who received free fibula flaps versus reconstruction plates after segmental resection of the lateral mandible. Thirty-seven completed questionnaires (18 fibula reconstructions and 19 patients with reconstruction plates) were available. Reconstruction with a free fibula flap did not provide clear additional benefit to bridging the defect with a reconstruction plate after segmental resection of the lateral mandible. In particular aspects known to have the most impact on HRQoL like swallowing, speech and chewing were not influenced by the type of reconstruction. Reconstruction of segmental defects of the lateral mandible with free fibula flap and reconstruction plate resulted in comparable HRQoL. If dental rehabilitation by means of dental implants is not anticipated in the fibula, then plate reconstruction with adequate soft tissue remains a suitable technique for the reconstruction of segmental defects of the lateral mandible. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  19. Reconstructing Plate Boundaries in the Jurassic Neo-Tethys From the East and West Vardar Ophiolites (Greece and Serbia)

    Science.gov (United States)

    Maffione, Marco; van Hinsbergen, Douwe J. J.

    2018-03-01

    Jurassic subduction initiation in the Neo-Tethys Ocean eventually led to the collision of the Adria-Africa and Eurasia continents and the formation of an 6,000 km long Alpine orogen spanning from Iberia to Iran. Reconstructing the location and geometry of the plate boundaries of the now disappeared Neo-Tethys during the initial moments of its closure is instrumental to perform more realistic plate reconstructions of this region, of ancient ocean basins in general, and on the process of subduction initiation. Neo-Tethyan relics are preserved in an ophiolite belt distributed above the Dinaric-Hellenic fold-thrust belt. Here we provide the first quantitative constraints on the geometry of the spreading ridges and trenches active in the Jurassic Neo-Tethys using a paleomagnetically based net tectonic rotation analysis of sheeted dykes and dykes from the West and East Vardar Ophiolites of Serbia (Maljen and Ibar) and Greece (Othris, Pindos, Vourinos, and Guevgueli). Based on our results and existing geological evidence, we show that initial Middle Jurassic ( 175 Ma) closure of the western Neo-Tethys was accommodated at a N-S trending, west dipping subduction zone initiated near and parallel to the spreading ridge. The West Vardar Ophiolites formed in the forearc parallel to this new trench. Simultaneously, the East Vardar Ophiolites formed above a second N-S to NW-SE trending subduction zone located close to the European passive margin. We tentatively propose that this second subduction zone had been active since at least the Middle Triassic, simultaneously accommodating the closure of the Paleo-Tethys and the back-arc opening of Neo-Tethys.

  20. The Role of Resorbable Plate and Artificial Bone Substitute in Reconstruction of Large Orbital Floor Defect

    Directory of Open Access Journals (Sweden)

    Ho Kwon

    2016-01-01

    Full Text Available It is essential to reduce and reconstruct bony defects adequately in large orbital floor fracture and defect. Among many reconstructive methods, alloplastic materials have attracted attention because of their safety and ease of use. We have used resorbable plates combined with artificial bone substitutes in large orbital floor defect reconstructions and have evaluated their long-term reliability compared with porous polyethylene plate. A total of 147 patients with traumatic orbital floor fracture were included in the study. Surgical results were evaluated by clinical evaluations, exophthalmometry, and computed tomography at least 12 months postoperatively. Both orbital floor height discrepancy and orbital volume change were calculated and compared with preoperative CT findings. The average volume discrepancy and vertical height discrepancies were not different between two groups. Also, exophthalmometric measurements were not significantly different between the two groups. No significant postoperative complication including permanent diplopia, proptosis, and enophthalmos was noted. Use of a resorbable plate with an artificial bone substitute to repair orbital floor defects larger than 2.5 cm2 in size yielded long-lasting, effective reconstruction without significant complications. We therefore propose our approach as an effective alternative method for large orbital floor reconstructions.

  1. Plate tectonics and the origin of the Juan Fernández Ridge: analysis of bathymetry and magnetic patterns

    Directory of Open Access Journals (Sweden)

    Cristián Rodrigo

    2014-10-01

    Full Text Available Juan Fernández Ridge (JFR is a cα. 800 km long alignment of seamounts and islands which is thought to be fed by a deep mantle plume. JFR includes the Friday and Domingo seamounts in the western active edge close to the active hotspot, and the O'Higgins Seamount and Guyot at the eastern limit just in front of the Chile-Perú trench. Recent bathymetric (Global Topography and magnetic (EMAG-2 datasets were interpreted both qualitatively and quantitatively by means of 3D inverse modeling and 2D direct modeling for geometry and susceptibility, together with an interpretation of the synthetic anomalies related to the classical hypothesis of deep seafloor spreading. Topographic and magnetic patterns are used to understand the tectonic evolution and origin of the JFR, especially in the western segment. Results show a continuous corridor with a base at ~3900 m depth formed by four groups of seamounts/islands with a number of summits. The deep ocean floor is ~22 to ~37 Myr old and is younger to the south of the Challenger Fracture Zone that runs in a SW-NE direction. The magnetic pattern of the western JFR segment, which is different than the eastern one, has no correlation with bathymetry and does not present a common polarity nor fit with magnetic models for isolated bodies. This superposition of magnetic patterns indicates a role of the faults/fractures of the Nazca Plate. Geological evidence supports the hypothesis of a fixed mantle plume for the origin of JFR but our data suggest that tectonic processes play a role, thus fueling the global controversy about these competing processes.

  2. Active tectonic deformation of the western Indian plate boundary: A case study from the Chaman Fault System

    Science.gov (United States)

    Crupa, Wanda E.; Khan, Shuhab D.; Huang, Jingqiu; Khan, Abdul S.; Kasi, Aimal

    2017-10-01

    Collision of the Eurasian and Indian plates has resulted in two spatially offset subduction zones, the Makran subduction zone to the south and the Himalayan convergent margin to the north. These zones are linked by a system of left-lateral strike-slip faults known as the Chaman Fault System, ∼1200 km, which spans along western Pakistan. Although this is one of the greatest strike-slip faults, yet temporal and spatial variation in displacement has not been adequately defined along this fault system. This study conducted geomorphic and geodetic investigations along the Chaman Fault in a search for evidence of spatial variations in motion. Four study areas were selected over the span of the Chaman Fault: (1) Tarnak-Rud area over the Tarnak-Rud valley, (2) Spinatizha area over the Spinatizha Mountain Range, (3) Nushki area over the Nushki basin, and (4) Kharan area over the northern tip of the Central Makran Mountains. Remote sensing data allowed for in depth mapping of different components and faults within the Kohjak group. Wind and water gap pairs along with offset rivers were identified using high-resolution imagery and digital-elevation models to show displacement for the four study areas. The mountain-front-sinuosity ratio, valley height-to-width-ratio, and the stream-length-gradient index were calculated and used to determine the relative tectonic activity of each area. These geomorphic indices suggest that the Kharan area is the most active and the Tarnak-Rud area is the least active. GPS data were processed into a stable Indian plate reference frame and analyzed. Fault parallel velocity versus fault normal distance yielded a ∼8-10 mm/yr displacement rate along the Chaman Fault just north of the Spinatizha area. InSAR data were also integrated to assess displacement rates along the fault system. Geodetic data support that ultra-slow earthquakes similar to those that strike along other major strike-slip faults, such as the San Andreas Fault System, are

  3. Paleomagnetic tests for tectonic reconstructions of the Late Jurassic-Early Cretaceous Woyla Group, Sumatra

    Science.gov (United States)

    Advokaat, Eldert; Bongers, Mayke; van Hinsbergen, Douwe; Rudyawan, Alfend; Marshal, Edo

    2017-04-01

    SE Asia consists of multiple continental blocks, volcanic arcs and suture zones representing remnants of closing ocean basins. The core of this mainland is called Sundaland, and was formed by accretion of continental and arc fragments during the Paleozoic and Mesozoic. The former positions of these blocks are still uncertain but reconstructions based on tectonostratigraphic, palaeobiogeographic, geological and palaeomagnetic studies indicate the continental terranes separated from the eastern margin of Gondwana. During the mid-Cretaceous, more continental and arc fragments accreted to Sundaland, including the intra-oceanic Woyla Arc now exposed on Sumatra. These continental fragments were derived from Australia, but the former position of the Woyla Arc is unconstrained. Interpretations on the former position of the Woyla Arc fall in two end-member groups. The first group interprets the Woyla Arc to be separated from West Sumatra by a small back-arc basin. This back arc basin opened in the Late Jurassic, and closed mid-Cretaceous, when the Woyla Arc collided with West Sumatra. The other group interprets the Woyla Arc to be derived from Gondwana, at a position close to the northern margin of Greater India in the Late Jurassic. Subsequently the Woyla Arc moved northwards and collided with West Sumatra in the mid-Cretaceous. Since these scenarios predict very different plate kinematic evolutions for the Neotethyan realm, we here aim to place paleomagnetic constraints on paleolatitudinal evolution of the Woyla Arc. The Woyla Arc consists mainly of basaltic to andesitic volcanics and dykes, and volcaniclastic shales and sandstones. Associated limestones with volcanic debris are interpreted as fringing reefs. This assemblage is interpreted as remnants of an Early Cretaceous intra-oceanic arc. West Sumatra exposes granites, surrounded by quartz sandstones, shales and volcanic tuffs. These sediments are in part metamorphosed. This assemblage is interpreted as a Jurassic

  4. Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria

    Directory of Open Access Journals (Sweden)

    Briestenský Miloš

    2015-10-01

    Full Text Available The EU-TecNet monitoring network uses customized three-dimensional extensometers to record transient deformations across individual faults. This paper presents the first results from two newly established monitoring points in the Balkan Mountains in Bulgaria. The data from Saeva Dupka, recorded across an EEN-WWS striking fault, show sinistral strike-slip along the fault and subsidence of the southern block. Much of the subsidence occurred around the time of the distal MW = 5.6 Pernik Earthquake. An important transient deformation event, which began in autumn 2012, was reflected by significant compression and following extension, across the monitored fault. The data from Bacho Kiro, recorded across a NE–SW striking fault, show sinistral strike-slip along the fault and subsidence of the north-western block. The same important deformation event was reflected by changes in the strike-slip, dip-slip, and horizontal opening/closing trends. These results have been compared to data from other monitoring points in the Western Carpathians, External Dinarides, and Tian Shan. Many of the sites show evidence of simultaneous displacement anomalies and this observation is interpreted as a reflection of the plate-wide propagation of a tectonic pressure pulse towards the end of 2012.

  5. Multi-type Tectonic Responses to Plate Motion Changes of Mega-Offset Transform Faults at the Pacific-Antarctic Ridge

    Science.gov (United States)

    Zhang, F.; Lin, J.; Yang, H.; Zhou, Z.

    2017-12-01

    Magmatic and tectonic responses of a mid-ocean ridge system to plate motion changes can provide important constraints on the mechanisms of ridge-transform interaction and lithospheric properties. Here we present new analysis of multi-type responses of the mega-offset transform faults at the Pacific-Antarctic Ridge (PAR) system to plate motion changes in the last 12 Ma. Detailed analysis of the Heezen, Tharp, and Udintsev transform faults showed that the extensional stresses induced by plate motion changes could have been released through a combination of magmatic and tectonic processes: (1) For a number of ridge segments with abundant magma supply, plate motion changes might have caused the lateral transport of magma along the ridge axis and into the abutting transform valley, forming curved "hook" ridges at the ridge-transform intersection. (2) Plate motion changes might also have caused vertical deformation on steeply-dipping transtensional faults that were developed along the Heezen, Tharp, and Udintsev transform faults. (3) Distinct zones of intensive tectonic deformation, resembling belts of "rift zones", were found to be sub-parallel to the investigated transform faults. These rift-like deformation zones were hypothesized to have developed when the stresses required to drive the vertical deformation on the steeply-dipping transtensional faults along the transform faults becomes excessive, and thus deformation on off-transform "rift zones" became favored. (4) However, to explain the observed large offsets on the steeply-dipping transtensional faults, the transform faults must be relatively weak with low apparent friction coefficient comparing to the adjacent lithospheric plates.

  6. Thrust-wrench interference tectonics in the Gulf of Cadiz (Africa-Iberia plate boundary in the North-East Atlantic): Insights from analog models

    OpenAIRE

    Duarte , João ,; Rosas , Filipe ,; Terrinha , Pedro; Gutscher , Marc-André ,; Malavielle , Jacques; Silva , Sonia; Matias , Luis

    2011-01-01

    International audience; In the Gulf of Cadiz key segment of the Africa-Iberia plate boundary (North-East Atlantic ocean), three main different modes of tectonic interference between a recently identified wrench system (SWIM) and the Gulf of Cadiz Accretionary Wedge (GCAW) were tested through analog sand-box modeling: a) An active accretionary wedge on top of a pre-existent inactive basement fault; b) An active strike-slip fault cutting a previously formed, inactive, accretionary wedge; and c)...

  7. Cytotoxicity difference of 316L stainless steel and titanium reconstruction plate

    OpenAIRE

    Ni Putu Mira Sumarta; Coen Pramono Danudiningrat; Ester Arijani Rachmat; Pratiwi Soesilawati

    2011-01-01

    Background: Pure titanium is the most biocompatible material today and used as a gold standard for metallic implants. However, stainless steel is still being used as implants because of its strength, ductility, lower price, corrosion resistant and biocompatibility. Purpose: This study was done to revealed the cytotoxicity difference between reconstruction plate made of 316L stainless steel and of commercially pure (CP) titanium in baby hamster kidney-21 (BHK-21) fibroblast culture through MTT...

  8. Reconstructing plate-motion changes in the presence of finite-rotations noise.

    Science.gov (United States)

    Iaffaldano, Giampiero; Bodin, Thomas; Sambridge, Malcolm

    2012-01-01

    Understanding lithospheric plate motions is of paramount importance to geodynamicists. Much effort is going into kinematic reconstructions featuring progressively finer temporal resolution. However, the challenge of precisely identifying ocean-floor magnetic lineations, and uncertainties in geomagnetic reversal timescales result in substantial finite-rotations noise. Unless some type of temporal smoothing is applied, the scenario arising at the native temporal resolution is puzzling, as plate motions vary erratically and significantly over short periods (<1 Myr). This undermines our ability to make geodynamic inferences, as the rates at which forces need to be built upon plates to explain these kinematics far exceed the most optimistic estimates. Here we show that the largest kinematic changes reconstructed across the Atlantic, Indian and South Pacific ridges arise from data noise. We overcome this limitation using a trans-dimensional hierarchical Bayesian framework. We find that plate-motion changes occur on timescales no shorter than a few million years, yielding simpler kinematic patterns and more plausible dynamics.

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

    Science.gov (United States)

    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

  10. From Tethyan Oceans to the Western Mediterranean I - Plate reconstructions from the Present back to the Early Mesozoic

    Science.gov (United States)

    Schmid, Stefan; Handy, Mark; Bousquet, Romain; Kissling, Eduard; Bernoulli, Daniel

    2010-05-01

    A new reconstruction of the branches of Alpine Tethys combines available plate kinematic models of Africa-Europe motion with a wealth of new geological and geophysical data (seismic tomography and paleomagnetics) to shed light the evolution of the Western Mediterranean-Alps system, from sea-floor spreading through subduction to collision. Unlike previous models which relate the fate of Alpine Tethys solely to relative motions of the African plate with respect to Europe during opening of the Atlantic, our reconstruction invokes motions and rotations of four additional and temporarily independent microplates: Adria, Iberia, Alcapia and Alkapecia. Translations and rotations of these microplates with respect to Europe are constrained in the following way: (1) The retro-translations of Adria back to 94 Ma are obtained from shortening estimates in the Alps along geological-geophysical transects of the Alpine orogen and from geobarometric estimates of subduction depth in tectonic units that underwent high-pressure and ultrahigh-pressure metamorphism. Rotations are based on paleomagnetic data of Márton et al. (in press); (2) Iberia follows the motion paths of Savostin et al. (1986), based on magnetic anomalies in the Central and Northern Atlantic; the Corsica-Sardinia block later rifted from Iberia leading to Burdigalian opening of the Liguria-Provençal basin (Serranne 1999). (3) The Alcapia microplate, whose name is derived from the acronym ALCAPA (Alps-Carpathians-Pannonian Basin), separated from Adria in Cretaceous times. Its movement with respect to Adria was absorbed by Cretaceous orogeny in the Eastern Alps, constrained by the Adria-Europe displacement and rotation path; later, during Cenozoic orogeny in the Alps, associated with the closing of the Alpine Tethys, it became part of the Adria microplate again. (4) The introduction of an independent Alkapekia continental fragment and independent microplate during the Late Cenozoic only (Alboran

  11. Regional P-wave Tomography in the Caribbean Region for Plate Reconstruction

    Science.gov (United States)

    Li, X.; Bedle, H.; Suppe, J.

    2017-12-01

    The complex plate-tectonic interactions around the Caribbean Sea have been studied and interpreted by many researchers, but questions still remain regarding the formation and subduction history of the region. Here we report current progress towards creating a new regional tomographic model, with better lateral and spatial coverage and higher resolution than has been presented previously. This new model will provide improved constraints on the plate-tectonic evolution around the Caribbean Plate. Our three-dimensional velocity model is created using taut spline parameterization. The inversion is computed by the code of VanDecar (1991), which is based on the ray theory method. The seismic data used in this inversion are absolute P wave arrival times from over 700 global earthquakes that were recorded by over 400 near Caribbean stations. There are over 25000 arrival times that were picked and quality checked within frequency band of 0.01 - 0.6 Hz by using a MATLAB GUI-based software named Crazyseismic. The picked seismic delay time data are analyzed and compared with other studies ahead of doing the inversion model, in order to examine the quality of our dataset. From our initial observations of the delay time data, the more equalized the ray azimuth coverage, the smaller the deviation of the observed travel times from the theoretical travel time. Networks around the NE and SE side of the Caribbean Sea generally have better ray coverage, and smaller delay times. Specifically, seismic rays reaching SE Caribbean networks, such as XT network, generally pass through slabs under South American, Central American, Lesser Antilles, Southwest Caribbean, and the North Caribbean transform boundary, which leads to slightly positive average delay times. In contrast, the Puerto Rico network records seismic rays passing through regions that may lack slabs in the upper mantle and show slightly negative or near zero average delay times. These results agree with previous tomographic

  12. Basic research on tectonic reconstruction on the basis of paleomagnetic methods

    International Nuclear Information System (INIS)

    Itoh, Yasuto

    2003-03-01

    It is of great importance to clarify deformation mode in an extensive tectonic event in order to evaluate stability of rock masses. Although such evaluation is based on structural geology in general, conventional methods are of little use for understanding of the temporal and spatial changes in deformation mode accompanying rotational motions, which are brought about by relatively large fault movements. Therefore, deformation mode of rock masses are quantitatively evaluated in this report on the basis of paleomagnetic data. Arrangements of geologic units in the central Japan form a large northward cusp around the Izu Peninsula, which is interpreted as a result of intense deformation of rock mass by repeated collisions of the Izu-Bonin Arc against the Honshu Arc since the Miocene Period. As the Izu Peninsula is considered to be actively transported northward with slips on the Kannawa Fault, understanding for development process of collisional deformation zone is quite important to evaluate geological stability of rock masses. This report presents the paleomagnetic data of Miocene rocks obtained from a borehole in the Mizunami Underground Research Laboratory, in Mizunami City, Gifu Prefecture. Progressive demagnetization tests separated stable primary remanent magnetizations for the Toki Lignite-Bearing Formation and the Akeyo Formation in the early Miocene. Their declinations are characterized by a significant easterly deflection reflecting a tectonic event probably linked to the Japan Sea opening. Comparison of the contemporaneous paleo-magnetic data reported from the central Japan implies that a boundary of relative rotational motions under the influence of collision of the Izu-Bonin Arc exists between the Mizunami area and eastern areas, for example, Kakegawa area. (author)

  13. Cytotoxicity difference of 316L stainless steel and titanium reconstruction plate

    Directory of Open Access Journals (Sweden)

    Ni Putu Mira Sumarta

    2011-03-01

    Full Text Available Background: Pure titanium is the most biocompatible material today and used as a gold standard for metallic implants. However, stainless steel is still being used as implants because of its strength, ductility, lower price, corrosion resistant and biocompatibility. Purpose: This study was done to revealed the cytotoxicity difference between reconstruction plate made of 316L stainless steel and of commercially pure (CP titanium in baby hamster kidney-21 (BHK-21 fibroblast culture through MTT assay. Methods: Eight samples were prepared from reconstruction plates made of stainless steel type 316L grade 2 (Coen’s reconstruction plate® that had been cut into cylindrical form of 2 mm in diameter and 3 mm long. The other one were made of CP titanium (STEMA Gmbh® of 2 mm in diameter and 2,2 mm long; and had been cleaned with silica paper and ultrasonic cleaner, and sterilized in autoclave at 121° C for 20 minutes.9 Both samples were bathed into microplate well containing 50 μl of fibroblast cells with 2 x 105 density in Rosewell Park Memorial Institute-1640 (RPMI-1640 media, spinned at 30 rpm for 5 minutes. Microplate well was incubated for 24 and 48 hours in 37° C. After 24 hours, each well that will be read at 24 hour were added with 50 μl solution containing 5mg/ml MTT reagent in phosphate buffer saline (PBS solutions, then reincubated for 4 hours in CO2 10% and 37° C. Colorometric assay with MTT was used to evaluate viability of the cells population after 24 hours. Then, each well were added with 50 μl dimethyl sulfoxide (DMSO and reincubated for 5 minutes in 37° C. the wells were read using Elisa reader in 620 nm wave length. Same steps were done for the wells that will be read in 48 hours. Each data were tabulated and analyzed using independent T-test with significance of 5%. Results: This study showed that the percentage of living fibroblast after exposure to 316L stainless steel reconstruction plate was 61.58% after 24 hours and 62

  14. Sternal plate fixation for sternal wound reconstruction: initial experience (Retrospective study

    Directory of Open Access Journals (Sweden)

    Musgrave Melinda

    2011-04-01

    Full Text Available Abstract Background Median sternotomy infection and bony nonunion are two commonly described complications which occur in 0.4 - 5.1% of cardiac procedures. Although relatively infrequent, these complications can lead to significant morbidity and mortality. The aim of this retrospective study is to evaluate the initial experience of a transverse plate fixation system following wound complications associated with sternal dehiscence with or without infection following cardiac surgery. Methods A retrospective chart review of 40 consecutive patients who required sternal wound reconstruction post sternotomy was performed. Soft tissue debridement with removal of all compromised tissue was performed. Sternal debridement was carried using ronguers to healthy bleeding bone. All patients underwent sternal fixation using three rib plates combined with a single manubrial plate (Titanium Sternal Fixation System®, Synthes. Incisions were closed in a layered fashion with the pectoral muscles being advanced to the midline. Data were expressed as mean ± SD, Median (range or number (%. Statistical analyses were made by using Excel 2003 for Windows (Microsoft, Redmond, WA, USA. Results There were 40 consecutive patients, 31 males and 9 females. Twenty two patients (55% were diagnosed with sternal dehiscence alone and 18 patients (45% with associated wound discharge. Thirty eight patients went on to heal their wounds. Two patients developed recurrent wound infection and required VAC therapy. Both were immunocompromised. Median post-op ICU stay was one day with the median hospital stay of 18 days after plating. Conclusion Sternal plating appears to be an effective option for the treatment of sternal wound dehiscence associated with sternal instability. Long-term follow-up and further larger studies are needed to address the indications, benefits and complications of sternal plating.

  15. A Note on the Inverse Reconstruction of Residual Fields in Surface Peened Plates

    Directory of Open Access Journals (Sweden)

    S. Ali Faghidian

    Full Text Available Abstract A modified stress function approach is developed here to reconstruct induced stress, residual stress and eigenstrain fields from limited experimental measurements. The present approach is successfully applied to three experimental measurements set in surface peened plates with shallow shot peening affected zone. The well-rehearsed advantage of the proposed approach is that it not only minimizes the deviation of measurements from its approximations but also will result in an inverse solution satisfying a full range of continuum mechanics requirements. Also, the effect of component thickness as a geometric parameter influencing the residual stress state is comprehensively studied. A key finding of present study is that the plate thickness has no influence on the maximum magnitude of eigenstrain profile and compressive residual stresses within the shot peening affected zone while having a great influence on the magnitude of tensile residual stress and the gradient of linear residual stresses present in deeper regions.

  16. Preputial reconstruction and tubularized incised plate urethroplasty in proximal hypospadias with ventral penile curvature.

    Science.gov (United States)

    Bhat, Amilal; Gandhi, Ajay; Saxena, Gajendra; Choudhary, Gautam Ram

    2010-10-01

    Objective of this study was to assess the feasibility and results of preputial reconstruction and tubularized incised plate urethroplasty (TIP) in patients of proximal hypospadias with ventral penile curvature. Twenty-seven patients of proximal hypospadias who underwent preputioplasty with TIP were evaluated retrospectively. Ventral curvature was corrected by mobilization of the urethral plate with the corpus spongiosum and the proximal urethra; dorsal plication was added according to the severity of curvature. Feasibility of preputial reconstruction was assessed by applying 3 stay sutures-the first to fix the skin at the corona, the second at the junction of the inner and outer preputial skin for pulling up the skin over the glans, and the third stay on penile skin at the level of the corona for retracting the skin. Preputial reconstruction consisted of a standard 3 layered re-approximation of the margins of the dorsal hood. Age of the patients varied from 10 months to 21 years with an average of 6 years and 4 months. Ventral curvature (mild 10, moderate 13, and severe 4 cases) was corrected by the mobilization of the urethral plate and spongiosum in 14 patients, 11 cases had mobilization of the proximal urethra in addition and 2 patients required single stitch dorsal plication with the above-mentioned steps. Two patients developed urethral fistula and 1 had preputial dehiscence. Preputioplasty with TIP is feasible in proximal hypospadias with curvature without increasing the complication rate. Postoperative phimosis can be prevented by on-table testing of the adequacy of preputial skin by 3 stay sutures.

  17. Dinosaur tectonics

    DEFF Research Database (Denmark)

    Graversen, Ole; Milàn, Jesper; B. Loope, David

    2007-01-01

    A dinosaur trackway in the Middle Jurassic eolian Entrada Sandstone of southern Utah, USA, exposes three undertracks that we have modeled as isolated tectonic regimes showing the development of fold-thrust ramp systems induced by the dinosaur's feet. The faulted and folded sequence is comparable...... to crustal scale tectonics associated with plate tectonics and foreland fold-thrust belts. A structural analysis of the dinosaur tracks shows the timing and direction of the forces exercised on the substrate by the animal's foot during the stride. Based on the structural analysis, we establish a scenario...... the back. As the body accelerated, the foot was forced backward. The rotated disc was forced backward along a detachment fault that was bounded by lateral ramps. The interramp segment matches the width of the dinosaur's foot which created an imbricate fan thrust system that extended to the far end...

  18. Reconstruction of the sellar floor using a silicone plate in transsphenoidal surgery and its postoperative appearance on magnetic resonance images

    International Nuclear Information System (INIS)

    Kabuto, Masanori; Kubota, Toshihiko; Kobayashi, Hidenori; Sato, Kazufumi; Ishii, Hisao; Nakagawa, Takao; Arai, Ryowa; Kitai, Ryuhei; Tuchida, Akira

    1993-01-01

    The reconstruction of the sellar floor using a silicone plate in transsphenoidal surgery and its postoperative appearance on magnetic resonance (MR) images are described. Thirty-eight patients with pituitary adenoma and four with Rathke's cleft cyst underwent this operation and postoperative MR imaging over a 4-year period. A fitting silicone plate for closing of the sellar floor window could be easily made from a large silicone block at the operation. The postoperative position of the silicone plate could be clearly detected by MR imaging as a very low intensity plate on both T1- and T2-weighted sagittal images. (author)

  19. Valgus osteotomy of the tibia with a Puddu plate combined with anterior cruciate ligament reconstruction

    Directory of Open Access Journals (Sweden)

    Albuquerque Roberto Freire da Mota e

    2003-01-01

    Full Text Available Anterior knee instability associated with a varus deformity is a complex condition with several treatment possibilities. Among these, anterior cruciate ligament (ACL associated to a simultaneous valgus tibial osteotomy is a increasing indication. This simultaneous procedure adds technical issues to those related to the isolated surgeries. Thus, the osteotomy plane and location of fixation hardware shouldn?t conflict with tibial tunnel and ACL graft fixation. Authors analyze the relations between a opening tibial valgus osteotomy stabilized with a Puddu plate and ACL reconstruction with a patellar tendon graft fixated with interference screws in 10 human cadaver knees. A straight oblique tibial osteotomy starting on the medial tibial cortex and oriented laterally and proximally was performed on all knees with a 10mm opening medially and stabilized with a Puddu plate on the most posterior aspect of the medial tibia, and a tibial tunnel drilled 50° to tibial plateau. With this technique there was no intersection between tibial tunnel or interference screw and the osteotomy or the plate fixation screws.

  20. PaleoMac: A Macintosh™ application for treating paleomagnetic data and making plate reconstructions

    Science.gov (United States)

    Cogné, J. P.

    2003-01-01

    This brief note provides an overview of a new Macintosh™ application, PaleoMac, (MacOS 8.0 or later, 15Mb RAM required) which permits rapid processing of paleomagnetic data, from the demagnetization data acquired in the laboratory, to the treatment of paleomagnetic poles, plate reconstructions, finite rotation computations on a sphere, and characterization of relative plate motions. Capabilities of PaleoMac include (1) high interactivity between the user and data displayed on screen which provides a fast and easy way to handle, add and remove data or contours, perform computations on subsets of points, change projections, sizes, etc.; (2) performance of all standard principal component analysis and statistical processing on a sphere [, 1953] etc.); (3) output of high quality plots, compatible with graphic programs such as Adobe Illustrator, and output of numerical results as ASCII files. Beyond its usefulness in treating paleomagnetic data, its ability to handle plate motion computations should be of large interest to the Earth science community.

  1. Plate flexure and volcanism: Late Cenozoic tectonics of the Tabar-Lihir-Tanga-Feni alkalic province, New Ireland Basin, Papua New Guinea

    Science.gov (United States)

    Lindley, I. D.

    2016-05-01

    Late Cenozoic Tabar-Lihir-Tanga-Feni (TLTF) alkaline volcanism, New Ireland Basin, PNG, is associated with extensional cracks along the crests of flexed ridges developed on the New Ireland Microplate (New name). The tectonic alignment of the TLTF volcanic arc is essentially perpendicular to the flexed ridges, suggesting that fractures parallel to the direction of maximum horizontal compression facilitated the rapid ascent of alkaline magmas from the mantle region, perhaps 60-70 km depth. The mainly Pliocene to Pleistocene volcanoes were localized at the intersection of ridge-parallel Kabang structures and arc-parallel Niffin structures, suggesting that the Kabang-Niffin structural intersections underlying each of the TLTF island groups provided a well developed, clustered network of open conduits which tapped the mantle source region. Periodic post-Miocene locking and unlocking along the strike-slip Kilinailau Fault (New name) are thought to have functioned as a valve, turning on (Pliocene) and then turning off (Pleistocene) volcanic activity, respectively. Partial locking of the Kilinailau Fault during the Pliocene resulted in the accumulation of intraplate stresses within the New Ireland Microplate, and caused plate flexure and ridge development, plate-cracking along ridge crests and the development of arc-parallel regional fractures parallel to the direction of maximum compression. Unlocking of the Kilinailau Fault in the Pleistocene resulted in the release of intraplate stresses in the New Ireland Microplate and a cessation of volcanic activity across most of the TLTF arc. The style and scale of plate flexure and cracking, accompanied by within-plate alkaline volcanism from equally spaced ridge-top eruptive centers confined to a narrow, linear volcanic arc are unknown from any other tectonic province.

  2. A tectonic reconstruction of accreted terranes along the paleo-Pacific margin of Gondwana

    Science.gov (United States)

    Bammel, Brandon

    The southern oceanic margin of Gondwana was nearly 40,000 km long or 24,854.8 miles. The southern margin was the result of the Terra Australis orogen. Spanning 18,000 km or 11,184.7 miles and is proposed as one of the largest and longest lived orogens in Earth history. The paleo-Pacific margin of Gondwana consisted of segments of the Australian-Antarctic craton, southern South America (modern Argentina and Chile), southern South Africa, Marie Byrdland, New Zealand and its adjacent continental shelf, the Ellsworth Mountains, and the Transantarctic Mountains. The process of terrane accretion has played a substantial part in the assembly of the continents as they look today. The paleo-Pacific margin of Gondwana was an active region of terrane accretion from the Neoproterozoic to the Late Mesozoic. This research study examines the accretion of terranes across the paleo-Pacific Gondwana margin to provide a comprehensive reconstruction. A paleogeographic basemap was created using PALEOMAP Project maps and the geology data was provided by the School of Geoscience from the University of Witwatersrand of South Africa. Location and data analyzed for terranes were collected building a PDF library of journal articles across numerous geological publications.

  3. Transformation of graphite by tectonic and hydrothermal processes in an active plate boundary fault zone, Alpine Fault, New Zealand

    Science.gov (United States)

    Kirilova, Matina; Toy, Virginia; Timms, Nicholas; Halfpenny, Angela; Menzies, Catriona; Craw, Dave; Rooney, Jeremy; Giorgetti, Carolina

    2017-04-01

    Graphite is a material with one of the lowest frictional strengths, with coefficient of friction of 0.1 and thus in natural fault zones it may act as a natural solid lubricant. Graphitization, or the transformation of organic matter (carbonaceous material, or CM) into crystalline graphite, is induced by compositional and structural changes during diagenesis and metamorphism. The supposed irreversible nature of this process has allowed the degree of graphite crystallinity to be calibrated as an indicator of the peak temperatures reached during progressive metamorphism. We examine processes of graphite emplacement and deformation in the Alpine Fault Zone, New Zealand's active continental tectonic plate boundary. Raman spectrometry indicates that graphite in the distal, amphibolite-facies Alpine Schist, which experienced peak metamorphic temperatures up to 640 ◦C, is highly crystalline and occurs mainly along grain boundaries within quartzo-feldspathic domains. The subsequent mylonitisation in the Alpine Fault Zone resulted in progressive reworking of CM under lower temperature conditions (500◦C-600◦C) in a structurally controlled environment, resulting in spatial clustering in lower-strain protomylonites, and further foliation-alignment in higher-strain mylonites. Subsequent brittle deformation of the mylonitised schists resulted in cataclasites that contain over three-fold increase in the abundance of graphite than mylonites. Furthermore, cataclasites contain graphite with two different habits: highly-crystalline, foliated forms that are inherited mylonitic graphite; and lower-crystallinity, less mature patches of finer-grained graphite. The observed graphite enrichment and the occurrence of poorly-organised graphite in the Alpine Fault cataclasites could result from: i) hydrothermal precipitation from carbon-supersaturated fluids; and/or ii) mechanical degradation by structural disordering of mylonitic graphite combined with strain-induced graphite

  4. Transpressional Tectonics across the N. American-Caribbean Plate Boundary: Preliminary Results of a Multichannel Seismic Survey of Lake Azuei, Haiti.

    Science.gov (United States)

    Hearn, C. K.; Cormier, M. H.; Sloan, H.; Wattrus, N. J.; Boisson, D.; Brown, B.; Guerrier, K.; King, J. W.; Knotts, P.; Momplaisir, R.; Sorlien, C. C.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.

    2017-12-01

    On January 12, 2010, a Mw 7.0 earthquake struck Haiti, killing over 200,000 people and devastating the Capital city of Port-au-Prince and the surrounding regions. It ruptured a previously unknown blind-thrust fault that abuts the Enriquillo Plantain Garden Fault (EPGF), one of two transform faults that define the North American-Caribbean plate boundary. That earthquake highlighted how transpression across this complex boundary is accommodated by slip partitioning into strike-slip and compressional structures. Because the seismic hazard is higher for a rupture on a reverse or oblique-slip fault than on a vertical strike-slip fault, the need to characterize the geometry of that fault system is clear. Lake Azuei overlies this plate boundary 60 km east of the 2010 epicenter. The lake's 23 km long axis trends NW-SE, parallel to the Haitian fold-and-thrust belt and oblique to the EPGF. This tectonic context makes it an ideal target for investigating the partitioning of plate motion between strike-slip and compressional structures. In January 2017, we acquired 222 km of multichannel seismic (MCS) profiles in the lake, largely concurrent with subbottom seismic (CHIRP) profiles. The MCS data were acquired using a high-frequency BubbleGun source and a 75 m-long, 24-channel streamer, achieving a 24 seismic fold with a penetration of 200 m below lakebed. With the goal of resolving tectonic structures in 3-D, survey lines were laid out in a grid with profiles spaced 1.2 km apart. Additional profiles were acquired at the SE end of the lake where most of the tectonic activity is presumably occurring. The co-located CHIRP and MCS profiles document the continuity of tectonic deformation between the surficial sediments and the deeper strata. Preliminary processing suggests that a SW-dipping blind thrust fault, expressed updip as a large monocline fold, may control the western edge of the lake. Gentle, young folds that protrude from the flat lakebed are also imaged with the CHIRP

  5. Closure of the Africa-Eurasia-North America plate motion circuit and tectonics of the Gloria fault

    Science.gov (United States)

    Argus, Donald F.; Gordon, Richard G.; Demets, Charles; Stein, Seth

    1989-01-01

    The current motions of the African, Eurasian, and North American plates are examined. The problems addressed include whether there is resolvable motion of a Spitsbergen microplate, the direction of motion between the African and North American plates, whether the Gloria fault is an active transform fault, and the implications of plate circuit closures for rates of intraplate deformation. Marine geophysical data and magnetic profiles are used to construct a model which predicts about 4 mm/yr slip across the Azores-Gibraltar Ridge, and west-northwest convergence near Gibraltar. The analyzed data are consistent with a rigid plate model with the Gloria fault being a transform fault.

  6. Misconceptions and Conceptual Changes Concerning Continental Drift and Plate Tectonics among Portuguese Students Aged 16-17.

    Science.gov (United States)

    Marques, Luis; Thompson, David

    1997-01-01

    This study investigates student misconceptions in the areas of continent, ocean, permanence of ocean basins, continental drift, Earth's magnetic field, and plates and plate motions. A teaching-learning model was designed based on a constructivist approach. Results show that students held a substantial number of misconceptions. (Author/DKM)

  7. Combined finite element and multibody musculoskeletal investigation of a fractured clavicle with reconstruction plate

    DEFF Research Database (Denmark)

    Cronskar, Marie; Rasmussen, John; Tinnsten, Mats

    2015-01-01

    This paper addresses the various treatment options for clavicle fractures by means of computational models, more precisely cases with a need for internal fixation: non-unions and certain complex fractures. The motivation for the work is that treatment can be enhanced by a better understanding...... of the loading of the clavicle and fixation device. This study aimed to develop a method for realistic simulation of stresses in the bone and fixation device in the case of a fractured clavicle. A finite element (FE) mesh of the clavicle geometry was created from computer tomography (CT) data and imported...... into the FE solver where the model was subjected to muscle forces and other boundary conditions from a multibody musculoskeletal model performing a typical activity of daily life. A reconstruction plate and screws were also imported into the model. The combination models returned stresses and displacements...

  8. DISCUSSION: When and How did Plate Tectonics Begin, What Came Before, and Why is this Controversy important for Understanding the Earth and Exoplanets?

    Science.gov (United States)

    Stern, R. J.; Gerya, T.; Sobolev, S. V.; Tackley, P.

    2015-12-01

    Because all 5 presentations in the Union session "When and How did Plate Tectonics Begin, What Came Before, and Why is this Controversy important for Understanding the Earth and Exoplanets?" will have 5 minute discussion periods, the scheduled 15 minute end-of-session discussion period is intended to allow other perspectives to be presented by the scientific community. We invite brief (2 powerpoint slides) comments from the community about any aspect of the topic at hand. We encourage anyone who has something pertinent or interesting to say to submit 2 powerpoint slides directly to any one of the four co-convenors listed on this abstract. The first slide should be a simple title with the name and affiliation of the commenter. The second slide should be the content of the comment. The convenors will compile all of these that are submitted up to the noon on the day before the session occurs, when we will upload the compiled files in the order that they were received (if we have received digital scans of signed waivers by that time, see below). During the discussion, we will call on those who have submitted 2 slides to the podium to make their points in 2 minutes or less (total time from being called to leaving the podium). Because this AGU Union session including the discussion period will be live-streamed and recorded, all Discussion Session commenters will be required to sign an AGU waiver acknowledging this and giving permission to be recorded. These will be sent via e-mail to those who submit 2 slide powerpoints. Commenters that do not sign and return the waiver will be scheduled after all commenters who have returned signed waivers and AGU will terminate live streaming and recording accordingly. If no one submits anything then we will have open discussion from the floor. We will also advertise the Monte Verita conference in Locarno Switzerland 17-22 July 2016. This conference will explore in greater detail the 5 key aspects of Plate Tectonic evolution briefly

  9. Comparison of Absorbable Mesh Plate versus Titanium-Dynamic Mesh Plate in Reconstruction of Blow-Out Fracture: An Analysis of Long-Term Outcomes

    Directory of Open Access Journals (Sweden)

    Woon Il Baek

    2014-07-01

    Full Text Available Background A blow-out fracture is one of the most common facial injuries in midface trauma. Orbital wall reconstruction is extremely important because it can cause various functional and aesthetic sequelae. Although many materials are available, there are no uniformly accepted guidelines regarding material selection for orbital wall reconstruction. Methods From January 2007 to August 2012, a total of 78 patients with blow-out fractures were analyzed. 36 patients received absorbable mesh plates, and 42 patients received titanium-dynamic mesh plates. Both groups were retrospectively evaluated for therapeutic efficacy and safety according to the incidence of three different complications: enophthalmos, extraocular movement impairment, and diplopia. Results For all groups (inferior wall fracture group, medial wall fractrue group, and combined inferomedial wall fracture group, there were improvements in the incidence of each complication regardless of implant types. Moreover, a significant improvement of enophthalmos occurred for both types of implants in group 1 (inferior wall fracture group. However, we found no statistically significant differences of efficacy or complication rate in every groups between both implant types. Conclusions Both types of implants showed good results without significant differences in long-term follow up, even though we expected the higher recurrent enophthalmos rate in patients with absorbable plate. In conclusion, both types seem to be equally effective and safe for orbital wall reconstruction. In particular, both implant types significantly improve the incidence of enophthalmos in cases of inferior orbital wall fractures.

  10. The assessment of the transformation of global tectonic plate models and the global terrestrial reference frames using the Velocity Decomposition Analysis

    Science.gov (United States)

    Ampatzidis, Dimitrios; König, Rolf; Glaser, Susanne; Heinkelmann, Robert; Schuh, Harald; Flechtner, Frank; Nilsson, Tobias

    2016-04-01

    The aim of our study is to assess the classical Helmert similarity transformation using the Velocity Decomposition Analysis (VEDA). The VEDA is a new methodology, developed by GFZ for the assessment of the reference frames' temporal variation and it is based on the separation of the velocities into two specified parts: The first is related to the reference system choice (the so called datum effect) and the latter one which refers to the real deformation of the terrestrial points. The advantage of the VEDA is its ability to detect the relative biases and reference system effects between two different frames or two different realizations of the same frame, respectively. We apply the VEDA for the assessment between several modern tectonic plate models and the recent global terrestrial reference frames.

  11. Plate convergence, crustal delamination, extrusion tectonics and minimization of shortening work as main controlling factors of the recent Mediterranean deformation pattern

    Directory of Open Access Journals (Sweden)

    D. Babbucci

    1997-06-01

    Full Text Available It is argued that the time-space distribution of major post middle Miocene deformation events in the Central-Eastern Mediterranean region, deduced from the relevant literature, can be coherently explained as a consequence of the convergence between the Africa/Arabia and Eurasia blocks. This plate convergence has mainly been accommodated by the consumption of the thinnest parts of the Northern African (Ionian and Levantine basins and peri-Adriatic margins. During each evolutionary phase the space distribution of trench zones is controlled by the basic physical requirement of minimizing the work of horizontal forces, induced by plate convergence, against the resisting forces, i.e., the cohesion of the upper brittle crustal layer and the buoyancy forces at the consuming boundaries. The significant changes of tectonic styles which determined the transition from one phase to the next, like those which occurred around the Messinian and the late Pliocene-early Pleistocene, were determined by the suture of consuming boundaries. When such an event occurs, the system must activate alternative consuming processes to accommodate the convergence of the major confining blocks. The observed deformations in the study area suggest that this tectonic reorganization mostly developed by the lateral extrusion of crustal wedges away from the sutured borders. This mechanism allowed the translation of maximum horizontal stresses from the locked collisional fronts to the zones where consumable lithosphere was still present, in order to activate the next consuming processes. The extensional episodes which led to the formation of basins and troughs in the Tyrrhenian and Aegean zones are interpreted as secondary effects of the outward escape of crustal wedges, like those which occurred in response to longitudinal compressional regimes in the Apennines and Aegean regions.

  12. Monitoring tectonic uplift and paleo-environmental reconstruction for marine terraces near Magaracik and Samandag, Hatay Province, Turkey

    International Nuclear Information System (INIS)

    Florentin, Jonathan A.; Blackwell, Bonnie A.B.; Blickstein, Joel I.B.; Skinner, Anne R.; Tueysuez, Okan; Tari, Ufuk; Can Genc, S.; Imren, Caner; Mo, Shirley; Huang, Yiwen E.W.; Kim, Maria

    2014-01-01

    Near Hatay, the Antakya-Samandag-Cyprus Fault (ASCF), East Anatolian and Dead Sea Fault Zones, the large faults that form the edges of the African, Anatolian, Cyprus and Arabian Plates, all produce large earthquakes, which have decimated Hatay repeatedly. Near Samandag, Hatay, differential vertical displacement on the ASCF has uplifted the southeastern side relative to northwestern side, producing large fault scarps that parallel the Asi (Orontes) River. Tectonic uplift coupled with Quaternary sea level fluctuations has produced several stacked marine terraces stranded above current sea level. This study dated 24 mollusc samples from 10 outcrops on six marine terraces near Samandag electron spin resonance (ESR). Ages were calculated using time-averaged and volumetrically averaged external dose rates, modelled by assuming typical water depths for the individual species and sediment thicknesses estimated from geological criteria. Uplift rates were then calculated for each fault block. At all the Magaracik terraces, the dates suggest that many shells were likely reworked. On the 30 m terrace at Magaracik IV (UTM 766588-3999880), Lithophagus burrows with in situ shells cross the unconformity. One such shell dated to 62 ± 6 ka, setting the minimum possible age for the terrace. For all the Magaracik terraces at ∼30 m above mean sea level (amsl), the youngest ages for the reworked shells, which averaged 60 ± 3 ka for six separate analyses, sets the maximum possible age for this unit. Thus, the terrace must date to 60-62 ± 3 ka, at the MIS 3/4 boundary when temperatures and sea levels were fluctuating rapidly. Older units dating to MIS 7, 6, and 5 likely were being eroded to supply some fossils found in this terrace. At Magaracik Dump (UTM 765391-4001048), ∼103 m amsl, Ostrea and other shells were found cemented in growth position to the limestone boulders outcropping there -1 , since MIS 5c. At Samandag Kurt Stream at 38 m amsl, molluscs were deposited fine sandy

  13. End Late Paleozoic tectonic stress field in the southern edge of Junggar Basin

    Directory of Open Access Journals (Sweden)

    Wei Ju

    2012-09-01

    Full Text Available This paper presents the end Late Paleozoic tectonic stress field in the southern edge of Junggar Basin by interpreting stress-response structures (dykes, folds, faults with slickenside and conjugate joints. The direction of the maximum principal stress axes is interpreted to be NW–SE (about 325°, and the accommodated motion among plates is assigned as the driving force of this tectonic stress field. The average value of the stress index R′ is about 2.09, which indicates a variation from strike-slip to compressive tectonic stress regime in the study area during the end Late Paleozoic period. The reconstruction of the tectonic field in the southern edge of Junggar Basin provides insights into the tectonic deformation processes around the southern Junggar Basin and contributes to the further understanding of basin evolution and tectonic settings during the culmination of the Paleozoic.

  14. Understanding seismic heterogeneities in the lower mantle beneath the Americas from seismic tomography and plate tectonic history

    NARCIS (Netherlands)

    Ren, Y.; Stutzmann, E.; Hilst, R.D. van der; Besse, J.

    2007-01-01

    We combine results from seismic tomography and plate motion history to investigate slabs of subducted lithosphere in the lower mantle beneath the Americas. Using broadband waveform cross correlation, we measured 37,000 differential P and S traveltimes, 2000 PcP-P and ScS-S times along a wide

  15. Geochronological and sedimentological evidences of Panyangshan foreland basin for tectonic control on the Late Paleozoic plate marginal orogenic belt along the northern margin of the North China Craton

    Science.gov (United States)

    Li, Jialiang; Zhou, Zhiguang; He, Yingfu; Wang, Guosheng; Wu, Chen; Liu, Changfeng; Yao, Guang; Xu, Wentao; Zhao, Xiaoqi; Dai, Pengfei

    2017-08-01

    Palaeo-uplift also was developed in the Early Permian to Middle Triassic (277-236 Ma), related to the final closure of the Paleo-Asian Ocean. Furthermore, we advocate that the tectonic setting of Inner Mongolia Palaeo-uplift probably belonged to the plate marginal orogenic belt during Early Permian-Middle Triassic.

  16. Posterior fossa reconstruction using titanium plate for the treatment of cerebellar ptosis after decompression for Chiari malformation.

    Science.gov (United States)

    Udani, Vikram; Holly, Langston T; Chow, Daniel; Batzdorf, Ulrich

    2014-01-01

    We describe our use of a perforated titanium plate to perform a partial posterior fossa cranioplasty in the treatment of cerebellar ptosis and dural ectasia after posterior fossa decompression (PFD). Twelve patients who had undergone PFD underwent posterior fossa reconstruction using a titanium plate. Symptoms were related to either descent of the cerebellum into the decompression or to dural ectasia into the craniectomy defect. Twelve patients who had undergone large suboccipital craniectomies and who presented with persistent headaches and some with neurological symptoms related to syringomyelia, underwent reoperation with placement of a small titanium plate. Ten of 12 patients showed symptomatic improvement after reoperation. Placement of a titanium plate appears to be an effective method of treatment of cerebellar ptosis and dural ectasia after PFD for Chiari malformation. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. [Fusion of reconstructed titanic plate, vertebral pedical screws and autogenous granulated cancellous bone graft in posterior occipitocervical region].

    Science.gov (United States)

    Zhong, Dejun; Song, Yueming

    2006-08-01

    To explore the technique of fusing the reconstructed titanic plate, the C2 pedical screws, and the autogenous granulated cancellous bone graft in the occipitocervical region. From April 2002 to January 2005, 19 patients aged 31-67 years with occipitocervical instability underwent the occipitocervical fusion using the reconstructed plate, C2 pedical screws, and autogenous granulated cancellous bone graft. Of the patients, 8 had complex occipitocervical deformity, 8 had old atlantoaxial fracture and dislocation, 2 had rheumatoid arthritis and anterior dislocation of the atlantoaxial joint, and 1 had cancer of the deltoid process of the axis. No complication occurred during and after operation. The follow-up for an average of 16 months in 19 patients showed that all the patients achieved solid bony fusion in the occipitocervical region. There was no broken plate, broken screw, looseness of the internal fixation or neurovascular injury. The fixation of the C2 pedical screws with the reconstructed titanic plate is reliable, the insertion is easy, and the autogenous granulated cancellous bone graft has a high fusion rate, thus resulting in a satisfactory effect in the occipitocervical fusion.

  18. Analysis of clinical efficacy and complications of titanium mini plate internal fixation and reconstructive surgery for patients with orbital fracture

    Directory of Open Access Journals (Sweden)

    Yang Liu

    2016-07-01

    Full Text Available AIM: To analyze the clinical efficacy and complications of titanium mini plate internal fixation and reconstructive surgery for patients with orbital fracture. METHODS: Fifty-seven cases(60 eyeswith orbital fracture from March 2013 to April 2014 in our hospital were researched. According to the random number table method, the patients were divided into observation group(29 cases with 30 eyesand control group(28 cases with 30 eyes. The control group was treated with hydroxyapatite artificial bone plate for internal fixation, and the observation group with titanium mini plate internal fixation and reconstructive surgery. The diplopia grading, grading of ocular movement disorder before and at 1, 3mo after treatment and postoperative complications(prolapse, dislocation, infectionwere compared between the two groups. RESULTS: In both group, all the 60 eyes were healed without scar formation. The rate of diplopia grading as grade 0 1mo postoperatively of observation group and the control groups were 63% and 40%(PPPCONCLUSION: The clinical curative effect of titanium mini plate internal fixation and reconstructive surgery has a good effect for orbital fractures, which can improve the therapeutic effect and reduce the incidence of adverse reactions.

  19. [Use of four kinds of three-dimensional printing guide plate in bone tumor resection and reconstruction operation].

    Science.gov (United States)

    Fu, Jun; Guo, Zheng; Wang, Zhen; Li, Xiangdong; Fan, Hongbin; Li, Jing; Pei, Yanjun; Pei, Guoxian; Li, Dan

    2014-03-01

    To explore the effectiveness of excision and reconstruction of bone tumor by using operation guide plate made by variety of three-dimensional (3-D) printing techniques, and to compare the advantages and disadvantages of different 3-D printing techniques in the manufacture and application of operation guide plate. Between September 2012 and January 2014, 31 patients with bone tumor underwent excision and reconstruction of bone tumor by using operation guide plate. There were 19 males and 12 females, aged 6-67 years (median, 23 years). The disease duration ranged from 15 days to 12 months (median, 2 months). There were 13 cases of malignant tumor and 18 cases of benign tumor. The tumor located in the femur (9 cases), the spine (7 cases), the tibia (6 cases), the pelvis (5 cases), the humerus (3 cases), and the fibula (1 case). Four kinds of 3-D printing technique were used in processing operation guide plate: fused deposition modeling (FDM) in 9 cases, stereo lithography appearance (SLA) in 14 cases, 3-D printing technique in 5 cases, and selective laser sintering (SLS) in 3 cases; the materials included ABS resin, photosensitive resin, plaster, and aluminum alloy, respectively. Before operation, all patients underwent thin layer CT scanning (0.625 mm) in addition to conventional imaging. The data were collected for tumor resection design, and operation guide plate was designed on the basis of excision plan. Preoperatively, the operation guide plates were made by 3-D printing equipment. After sterilization, the guide plates were used for excision and reconstruction of bone tumor. The time of plates processing cycle was recorded to analyse the efficiency of 4 kinds of 3-D printing techniques. The time for design and operation and intraoperative fluoroscopy frequency were recorded. Twenty-eight patients underwent similar operations during the same period as the control group. The processing time of operation guide plate was (19.3 +/- 6.5) hours in FDM, (5.2 +/- 1

  20. Neutron star crustal plate tectonics. I. Magnetic dipole evolution in millisecond pulsars and low-mass X-ray binaries

    International Nuclear Information System (INIS)

    Ruderman, M.

    1991-01-01

    Crust lattices in spinning-up or spinning-down neutron stars have growing shear stresses caused by neutron superfluid vortex lines pinned to lattice nuclei. For the most rapidly spinning stars, this stress will break and move the crust before vortex unpinning occurs. In spinning-down neutron stars, crustal plates will move an equatorial subduction zone in which the plates are forced into the stellar core below the crust. The opposite plate motion occurs in spinning-up stars. Magnetic fields which pass through the crust or have sources in it move with the crust. Spun-up neutron stars in accreting low-mass X-ray binaries LMXBs should then have almost axially symmetric magnetic fields. Spun-down ones with very weak magnetic fields should have external magnetic fields which enter and leave the neutron star surface only near its equator. The lowest field millisecond radiopulsars seem to be orthogonal rotators implying that they have not previously been spun-up in LMXBs but are neutron stars initially formed with periods near 0.001 s that subsequently spin down to their present periods. Accretion-induced white dwarf collapse is then the most plausible genesis for them. 29 refs

  1. How We Got to the Northern Hemisphere Ice Ages: Late Miocene Global Cooling and Plate Tectonic CO2 Forcing

    Science.gov (United States)

    Herbert, T.; Dalton, C. A.; Carchedi, C.

    2017-12-01

    The evolution of Earth's climate between "refrigeration" of East Antarctica and the onset of cyclic Northern Hemisphere glaciation spanned more than 11 Myr. In the latest Miocene (Messinian) time, approximately half way on this journey, changes on land, ranging from the expansion of arid zones to major floral and faunal ecosystem shifts, accelerated. Recent compilations of marine surface temperatures reveal that global cooling from the Miocene Optimum (14-16Ma) also accelerated in late Miocene (7-5.35 Ma) time to reach temperatures not much above Holocene conditions. Both hemispheres cooled in parallel, with the changes amplified at higher latitudes in comparison to the tropics. Despite the strong circumstantial case for CO2 decline as the dominant cause of late Miocene climatic and evolutionary change, proxy indicators of CO2concentrations paint an equivocal picture of greenhouse forcing. Here we provide evidence that global sea floor spreading (SFS) rates decelerated at exactly the times of major climatic cooling, linking a decline in tectonic degassing (at both subduction zones and mid-ocean ridges) to fundamental shifts in the global carbon cycle. Our work utilizes newly available global compilations of seafloor fabric and marine magnetic anomalies provided by the NSF-funded Global Seafloor Fabric and Magnetic Lineation Data Base Project. Previous global compilations of SFS typically binned estimates over 10 Myr increments, losing critical resolution on the timescale of late Neogene climate changes. We further improve the signal:noise of SFS estimates by incorporating recent advances in the astronomical calibration of the Miocene geomagnetic polarity timescale. We use two approaches to compile spreading rate estimates over the past 20 Myr at each spreading system: optimized finite rotation calculations, and averages of sea floor-spreading derived from the distances of magnetic lineations along flow lines on the sea floor. Weighted by ridge length, we find an 25

  2. Structural and Tectonic Map Along the Pacific-North America Plate Boundary in Northern Gulf of California, Sonora Desert and Valle de Mexicali, Mexico, from Seismic Reflection Evidence

    Science.gov (United States)

    Gonzalez-Escobar, M.; Suarez-Vidal, F.; Mendoza-Borunda, R.; Martin Barajas, A.; Pacheco-Romero, M.; Arregui-Estrada, S.; Gallardo-Mata, C.; Sanchez-Garcia, C.; Chanes-Martinez, J.

    2012-12-01

    Between 1978 and 1983, Petróleos Mexicanos (PEMEX) carried on an intense exploration program in the northern Gulf of California, the Sonora Desert and the southern part of the Mexicali Valley. This program was supported by a seismic reflection field operation. The collected seismic data was 2D, with travel time of 6 s recording, in 48 channels, and the source energy was: dynamite, vibroseis and air guns. Since 2007 to present time, the existing seismic data has been re-processing and ire-interpreting as part of a collaboration project between the PEMEX's Subdirección de Exploración (PEMEX) and CICESE. The study area is located along a large portion of the Pacific-North America plate boundary in the northern Gulf of California and the Southern part of the Salton Trough tectonic province (Mexicali Valley). We present the result of the processes reflection seismic lines. Many of the previous reported known faults were identify along with the first time described located within the study region. We identified regions with different degree of tectonic activity. In structural map it can see the location of many of these known active faults and their associated seismic activity, as well as other structures with no associated seismicity. Where some faults are mist placed they were deleted or relocated based on new information. We included historical seismicity for the region. We present six reflection lines that cross the aftershocks zone of the El Mayor-Cucapah earthquake of April 4, 2010 (Mw7.2). The epicenter of this earthquake and most of the aftershocks are located in a region where pervious to this earthquake no major earthquakes are been reported. A major result of this study is to demonstrate that there are many buried faults that increase the seismic hazard.

  3. Exploring the resonant vibration of thin plates: Reconstruction of Chladni patterns and determination of resonant wave numbers.

    Science.gov (United States)

    Tuan, P H; Wen, C P; Chiang, P Y; Yu, Y T; Liang, H C; Huang, K F; Chen, Y F

    2015-04-01

    The Chladni nodal line patterns and resonant frequencies for a thin plate excited by an electronically controlled mechanical oscillator are experimentally measured. Experimental results reveal that the resonant frequencies can be fairly obtained by means of probing the variation of the effective impedance of the exciter with and without the thin plate. The influence of the extra mass from the central exciter is confirmed to be insignificant in measuring the resonant frequencies of the present system. In the theoretical aspect, the inhomogeneous Helmholtz equation is exploited to derive the response function as a function of the driving wave number for reconstructing experimental Chladni patterns. The resonant wave numbers are theoretically identified with the maximum coupling efficiency as well as the maximum entropy principle. Substituting the theoretical resonant wave numbers into the derived response function, all experimental Chladni patterns can be excellently reconstructed. More importantly, the dispersion relationship for the flexural wave of the vibrating plate can be determined with the experimental resonant frequencies and the theoretical resonant wave numbers. The determined dispersion relationship is confirmed to agree very well with the formula of the Kirchhoff-Love plate theory.

  4. Three Plate Reconstruction in the Eastern Indian Ocean: New Constraints on Wharton and Australian-Antarctic basins

    Science.gov (United States)

    Jacob, J.; Dyment, J.

    2012-12-01

    Understanding the continuous seismicity and repeated occurrence of major earthquakes in Sumatra and the neighboring area requires detailed constrains on the subducting plate. In this study we analyze the past plate kinematics evolution of the Wharton basin, eastern Indian Ocean through a three plate reconstruction involving Australia (AUS), Antarctica (ANT), and India (IND). We compile marine magnetic identifications in the Australian-Antarctic Basin [1,2], the Crozet and Central Indian basins (Yatheesh et al, in prep.) and the Wharton Basin [3]. The Wharton Basin is characterized by an extinct spreading center dated by anomaly 18 (38 Ma). The southern flank of the basin exhibits a continuous sequence of anomalies 20n (42 Ma) to 34n (84 Ma), whereas the northern flank lacks some of the older anomalies because a significant part has been subducted in the Sunda Trench. The three-plate reconstructions have provided set of rotation parameters describing the evolution of IND-AUS. Using these parameters, we have reconstructed the missing isochrons of the northern flank and the detailed geometry of the subducted part of the Wharton basin. Such an exercise provides useful constraints on the age and structure of the plate in subduction under Indonesia. As a byproduct, the three plate reconstruction provided set of rotation parameters for AUS-ANT as well, which constrains the conjugate fit between the basins. Previous studies [1,2,4,5] have achieved such a fit on the base of ill-defined fracture zones. We consider the well-defined fracture zones from the Crozet, Central Indian, and Wharton basins, but avoid using the poor fracture zone imprints from the Australian-Antarctic Basin. As a result from this approach, we conclude that the relative motion of AUS with respect to ANT initially followed a north-south direction, then changed to northwest-southeast at anomaly 32ny, and reverted to northeast southwest at anomaly 24no prior to the establishment of the Southeast Indian

  5. Marginal inherited structures impact on the oblique convergent N American Plate/ Central Caribbean plate-boundary in the Northern Caribbean. The tectonic evolution since Miocene times based on Haiti data acquired onshore and offshore since 2012- a step toward an ADP Drilling Proposal (Haiti-DRILL).

    Science.gov (United States)

    Ellouz, N.; Hamon, Y.; Deschamps, R.; Battani, A.; Wessels, R.; Boisson, D.; Prepetit, C.; Momplaisir, R.

    2017-12-01

    Since Early Paleogene times, the North Caribbean plate is colliding obliquely with the south continental part of the old N. American Margins, which is represented by various segments from West to East, inherited from Jurassic times. Location, amount of displacement, rotation and the structural deformation of these margin segments, resulting from the dislocation of the continental N American margin, are not clearly yet established. At present, the plate limits are marked either by two left lateral faults west and inside Haiti (OSF in the North and EPGF in the South), oblique collision front (further west in Cuba), oblique subducted segments (to the East, Porto-Rico). From our recent works operated both offshore (Haiti-SIS and Haiti-BGF surveys 2012-2015) and onshore (field campaigns 2013-2017) in Haitian zone, the position of the present-day and paleo major limits have been redefined. These paleolimits have been reconstructed up to early Miocene times, based on: restoration of regional structural cross-sections, sedimentology and on paleoenvironement studies. In a preliminary way, we analyzed the complexity of the tectonic heritage with possible nature, heterogeneity of the crustal fragments and associated margins close to Haiti (age, structure, environment, location of the dislocated blocks through times) which profoundly impact the partitioning of the deformation along this complex transformed margin. The change in the structure wavelength, decollement level variations are primary constraints in the restoration of the main units and do impose a deep connection along specific segments either related to strike-slip or to splay faults. The asymmetry on the repartition of the fault activity tend to prove that the past motion related to "EPGF transfer zone" is mainly partitioned in Haiti to the North of the present-day EPGF position. At present, these results are still coherent with the distribution of the aftershoks registered after 2010, and with the present

  6. Stress state reconstruction and tectonic evolution of the northern slope of the Baikit anteclise, Siberian Craton, based on 3D seismic data

    Science.gov (United States)

    Moskalenko, A. N.; Khudoley, A. K.; Khusnitdinov, R. R.

    2017-05-01

    In this work, we consider application of an original method for determining the indicators of the tectonic stress fields in the northern Baikit anteclise based on 3D seismic data for further reconstruction of the stress state parameters when analyzing structural maps of seismic horizons and corresponded faults. The stress state parameters are determined by the orientations of the main stress axes and shape of the stress ellipsoid. To calculate the stress state parameters from data on the spatial orientations of faults and slip vectors, we used the algorithms from quasiprimary stress computation methods and cataclastic analysis, implemented in the software products FaultKinWin and StressGeol, respectively. The results of this work show that kinematic characteristics of faults regularly change toward the top of succession and that the stress state parameters are characterized by different values of the Lode-Nadai coefficient. Faults are presented as strike-slip faults with normal or reverse component of displacement. Three stages of formation of the faults are revealed: (1) partial inversion of ancient normal faults, (2) the most intense stage with the predominance of thrust and strike-slip faults at north-northeast orientation of an axis of the main compression, and (3) strike-slip faults at the west-northwest orientation of an axis of the main compression. The second and third stages are pre-Vendian in age and correlate to tectonic events that took place during the evolution of the active southwestern margin of the Siberian Craton.

  7. Hook plate fixation for acute acromioclavicular dislocations without coracoclavicular ligament reconstruction: a functional outcome study in military personnel.

    Science.gov (United States)

    Kumar, Narinder; Sharma, Vyom

    2015-08-01

    The aim of our study was to evaluate the shoulder function after clavicular hook plate fixation of acute acromioclavicular dislocations (Rockwood type III) in a population group consisting exclusively of high-demand military personnel. This prospective study was carried out at a tertiary care military orthopaedic centre during 2012-2013 using clavicular hook plate for management of acromioclavicular injuries without coracoclavicular ligament reconstruction in 33 patients. All patients underwent routine implant removal after 16 weeks. The functional outcome was assessed at 3, 6 and 12 months after hook plate removal and 2 years from the initial surgery using the Constant Murley and UCLA Scores. All the patients were male serving soldiers and had sustained acromioclavicular joint dislocation (Rockwood type III). Mean age of the patient group was 34.24 years (21-55 years). The mean follow-up period in this study was 23.5 months (20-26 months) after hook plate fixation and an average of 19.9 months (17-22 months) after hook plate removal. The average Constant Score at 3 months after hook plate removal was 60.3 as compared to 83.7 and 90.3 at 6 months and 1 year, respectively, and an average of 91.8 at the last follow-up that was approximately 2 years after initial surgery which was statistically significant (p value acromioclavicular dislocations producing excellent medium-term functional results in high-demand soldiers.

  8. Spiral tectonics

    Science.gov (United States)

    Hassan Asadiyan, Mohammad

    2014-05-01

    Spiral Tectonics (ST) is a new window to global tectonics introduced as alternative model for Plate Tectonics (PT). ST based upon Dahw(rolling) and Tahw(spreading) dynamics. Analogues to electric and magnetic components in the electromagnetic theory we could consider Dahw and Tahw as components of geodynamics, when one component increases the other decreases and vice versa. They are changed to each other during geological history. D-component represents continental crust and T-component represents oceanic crust. D and T are two arm of spiral-cell. T-arm 180 degree lags behind D-arm so named Retard-arm with respect to D or Forward-arm. It seems primary cell injected several billions years ago from Earth's center therefore the Earth's core was built up first then mantel and finally the crust was build up. Crust building initiate from Arabia (Mecca). As the universe extended gravitation wave swirled the earth fractaly along cycloid path from big to small scale. In global scale (order-0) ST collect continents in one side and abandoned Pacific Ocean in the other side. Recent researches also show two mantels upwelling in opposite side of the Earth: one under Africa (tectonic pose) and the other under Pacific Ocean (tectonic tail). In higher order (order-1) ST build up Africa in one side and S.America in the other side therefore left Atlantic Ocean meandered in between. In order-n e.g. Khoor Musa and Bandar-Deylam bay are seen meandered easterly in the Iranian part but Khoor Abdullah and Kuwait bay meandered westerly in the Arabian part, they are distributed symmetrically with respect to axis of Persian Gulf(PG), these two are fractal components of easterly Caspian-wing and westerly Black Sea-wing which split up from Anatoly. Caspian Sea and Black Sea make two legs of Y-like structure, this shape completely fitted with GPS-velocity map which start from PG and split up in the Catastrophic Point(Anatoly). We could consider PG as remnants of Ancient Ocean which spent up

  9. Tectonic predictions with mantle convection models

    Science.gov (United States)

    Coltice, Nicolas; Shephard, Grace E.

    2018-04-01

    Over the past 15 yr, numerical models of convection in Earth's mantle have made a leap forward: they can now produce self-consistent plate-like behaviour at the surface together with deep mantle circulation. These digital tools provide a new window into the intimate connections between plate tectonics and mantle dynamics, and can therefore be used for tectonic predictions, in principle. This contribution explores this assumption. First, initial conditions at 30, 20, 10 and 0 Ma are generated by driving a convective flow with imposed plate velocities at the surface. We then compute instantaneous mantle flows in response to the guessed temperature fields without imposing any boundary conditions. Plate boundaries self-consistently emerge at correct locations with respect to reconstructions, except for small plates close to subduction zones. As already observed for other types of instantaneous flow calculations, the structure of the top boundary layer and upper-mantle slab is the dominant character that leads to accurate predictions of surface velocities. Perturbations of the rheological parameters have little impact on the resulting surface velocities. We then compute fully dynamic model evolution from 30 and 10 to 0 Ma, without imposing plate boundaries or plate velocities. Contrary to instantaneous calculations, errors in kinematic predictions are substantial, although the plate layout and kinematics in several areas remain consistent with the expectations for the Earth. For these calculations, varying the rheological parameters makes a difference for plate boundary evolution. Also, identified errors in initial conditions contribute to first-order kinematic errors. This experiment shows that the tectonic predictions of dynamic models over 10 My are highly sensitive to uncertainties of rheological parameters and initial temperature field in comparison to instantaneous flow calculations. Indeed, the initial conditions and the rheological parameters can be good enough

  10. Hyperspectral image reconstruction using RGB color for foodborne pathogen detection on agar plates

    Science.gov (United States)

    Yoon, Seung-Chul; Shin, Tae-Sung; Park, Bosoon; Lawrence, Kurt C.; Heitschmidt, Gerald W.

    2014-03-01

    This paper reports the latest development of a color vision technique for detecting colonies of foodborne pathogens grown on agar plates with a hyperspectral image classification model that was developed using full hyperspectral data. The hyperspectral classification model depended on reflectance spectra measured in the visible and near-infrared spectral range from 400 and 1,000 nm (473 narrow spectral bands). Multivariate regression methods were used to estimate and predict hyperspectral data from RGB color values. The six representative non-O157 Shiga-toxin producing Eschetichia coli (STEC) serogroups (O26, O45, O103, O111, O121, and O145) were grown on Rainbow agar plates. A line-scan pushbroom hyperspectral image sensor was used to scan 36 agar plates grown with pure STEC colonies at each plate. The 36 hyperspectral images of the agar plates were divided in half to create training and test sets. The mean Rsquared value for hyperspectral image estimation was about 0.98 in the spectral range between 400 and 700 nm for linear, quadratic and cubic polynomial regression models and the detection accuracy of the hyperspectral image classification model with the principal component analysis and k-nearest neighbors for the test set was up to 92% (99% with the original hyperspectral images). Thus, the results of the study suggested that color-based detection may be viable as a multispectral imaging solution without much loss of prediction accuracy compared to hyperspectral imaging.

  11. Passive detection and localization of fatigue cracking in aluminum plates using Green's function reconstruction from ambient noise.

    Science.gov (United States)

    Yang, Yang; Xiao, Li; Qu, Wenzhong; Lu, Ye

    2017-11-01

    Recent theoretical and experimental studies have demonstrated that a local Green's function can be retrieved from the cross-correlation of ambient noise field. This technique can be used to detect fatigue cracking in metallic structures, owing to the fact that the presence of crack can lead to a change in Green's function. This paper presents a method of structural fatigue cracking characterization method by measuring Green's function reconstruction from noise excitation and verifies the feasibility of crack detection in poor noise source distribution. Fatigue cracks usually generate nonlinear effects, in which different wave amplitudes and frequency compositions can cause different nonlinear responses. This study also undertakes analysis of the capacity of the proposed approach to identify fatigue cracking under different noise amplitudes and frequency ranges. Experimental investigations of an aluminum plate are conducted to assess the cross-correlations of received noise between sensor pairs and finally to detect the introduced fatigue crack. A damage index is proposed according to the variation between cross-correlations obtained from the pristine crack closed state and the crack opening-closure state when sufficient noise amplitude is used to generate nonlinearity. A probability distribution map of damage is calculated based on damage indices. The fatigue crack introduced in the aluminum plate is successfully identified and oriented, verifying that a fatigue crack can be detected by reconstructing Green's functions from an imperfect diffuse field in which ambient noise sources exist locally. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. The Silurian Hoedongri Formation in the Taebaeksan Basin of Korea Revisited: its Significance in the Tectonic Reconstruction of East Asia

    Science.gov (United States)

    Chae, S.; Hong, J.; Jung, S.; Ree, J.

    2011-12-01

    The Silurian Hoedongri Formation of the Taebaeksan Basin of South Korea has been used as a key unit to the correlation of tectonic provinces of East Asia since the South China craton (or Yangtz block) contains Silurian-Devonian sequences as well as Cambrian-Ordovician ones in the Paleozoic basins while the North China craton (or Sino-Korea block) is devoid of Silurian-Devonian sequences. In the Biryongdong area near the type locality of the Hoedongri Formation, it has been reported that the gray limestone of the Hoedongri Formation unconformably overlies brownish gray limestone of the Ordovician Haengmae Formation. However, our detailed examination on the Biryongdong section reveals that both of the brownish gray and gray limestones are mylonitic marbles with the boundary between the two units being a healed fault breccia zone (~ 12 m thick). The main difference of the two units is that repeated cycles of plastic deformation and fracturing occurred in the underlying brownish gray marble ('Haengmae') while the gray marble ('Hoedongri') deformed mainly by intracrystalline plasticity. The mylonitic foliation strikes NW with a low to moderate dip angle (20-60°) to NE. The ridge-in-groove type lineation on foliation surface trends NNW. The shape-preferred foliation of elongated calcite grains are oblique to the mylonitic foliation defined by layers with a grain-size variation, indicating a top-to-the-SSE shear sense. The mylonitic marble consists of elongated remnant grains (80-120 μm) with deformation twins and dynamically recrystallized matrix grains (10-40 μm). Grain boundaries and twin boundaries are lobate or wavy, indicating dynamic boundary migration. Some layers of the gray mylonitic marble are composed entirely of larger (80-120 μm) elongated calcite grains. In the brownish gray mylonitic marble unit, layers of brittle fracturing overprinting mylonitic foliation occur. In some of these layers, fragments (several cm - tens of cm) of the mylonitic marble are

  13. Plate tectonics: A supercontinental boost

    Science.gov (United States)

    Lenardic, Adrian

    2017-01-01

    180 million years ago Earth's continents were amalgamated into one supercontinent called Pangaea. Analysis of oceanic crust formed since that time suggests that the cooling rate of Earth was enhanced in the wake of Pangaea's dispersal.

  14. Thermal History of Planetary Objects: From Asteroids to super-Earths, from plate-tectonics to life (Runcorn-Florensky Medal Lecture)

    Science.gov (United States)

    Spohn, Tilman

    2013-04-01

    planets - like the Earth - the volatile budget matters for the interior evolution. With plate tectonics, large-scale volatile cycles are invoked. On the Earth, even the biosphere is speculated to interact with the interior. It has been argued (e.g., Rosing et al. 2006; Sleep et al, 2012) that the formation of continents could be a consequence of bioactivity harvesting solar energy through photosynthesis to help build the continents and that the mantle should carry a chemical biosignature. A model is presented that includes mantle convection, mantle water vapor degassing at mid-oceanic ridges and regassing through subduction zones, continental crust formation and erosion and water storage and transport in a porous oceanic crust that includes hydrous mineral phases. The biosphere enters the model through its effect on continental erosion and through a reduction of the activation barrier to metamorphic reactions (e.g., Kim et al., 2004) in sediment layers. An abiotic world is found to have a much drier mantle than the present Earth but may have a similar surface coverage by continents. The reduced rate of continental crust production on the abiotic world would be balanced by a reduced rate of continent erosion. Through the effect of water on the mantle rheology, the biotic world would tend to be tectonically more active and have a more rapid long-term carbon-silicate cycle. J. Kim, H. Dong, J. Seabaugh, S. W. Newell, D. D. Eberl, Science 303, 830-832, 2004 N. H. Sleep, D. K. Bird, E. Pope, Annu. Rev. Earth Planet. Sci. 40, 277-300, 2012 M. T. Rosing, D. K. Bird, N. H. Sleep, W. Glassley, F. Albarede, Paleo3 232, 90-113, 2006

  15. Simulation of tectonic evolution of the Kanto basin of Japan since 1 Ma due to subduction of the Pacific and Philippine sea plates and collision of the Izu-Bonin arc

    Science.gov (United States)

    Hashima, Akinori; Sato, Toshinori; Sato, Hiroshi; Asao, Kazumi; Furuya, Hiroshi; Yamamoto, Shuji; Kameo, Koji; Miyauchi, Takahiro; Ito, Tanio; Tsumura, Noriko; Kaneda, Heitaro

    2015-04-01

    The Kanto basin, the largest lowland in Japan, developed by flexure as a result of (1) the subduction of the Philippine Sea (PHS) and the Pacific (PAC) plates and (2) the collision of the Izu-Bonin arc with the Japanese island arc. Geomorphological, geological, and thermochronological data on long-term vertical movements over the last 1 My suggest that subsidence initially affected the entire Kanto basin after which the area of subsidence gradually narrowed until, finally, the basin began to experience uplift. In this study, we modelled the tectonic evolution of the Kanto basin following the method of Matsu'ura and Sato (1989) for a kinematic subduction model with dislocations, in order to quantitatively assess the effects of PHS and PAC subduction. We include the steady slip-rate deficit (permanent locking rate at the plate interface) in our model to account for collision process. We explore how the arc-arc collision process has been affected by a westerly shift in the PHS plate motion vector with respect to the Eurasian plate, thought to have occurred between 1.0-0.5 Ma, using long-term vertical deformation data to constrain extent of the locked zone on the plate interface. We evaluated the change in vertical deformation rate for two scenarios: (1) a synchronous shift in the orientation of the locked zone as PHS plate motion shifts and (2) a delayed shift in the orientation of the locked zone following a change in plate motion. Observed changes in the subsidence/uplift pattern are better explained by scenario (2), suggesting that recent (<1 My) deformation in the Kanto basin shows a lag in crustal response to the shift in plate motion. We also calculated recent stress accumulation rates and found a good match with observed earthquake mechanisms, which shows that intraplate earthquakes serve to release stress accumulated through long-term plate interactions.

  16. Simulation of tectonic evolution of the Kanto Basin of Japan since 1 Ma due to subduction of the Pacific and Philippine Sea plates and the collision of the Izu-Bonin arc

    Science.gov (United States)

    Hashima, Akinori; Sato, Toshinori; Sato, Hiroshi; Asao, Kazumi; Furuya, Hiroshi; Yamamoto, Shuji; Kameo, Koji; Miyauchi, Takahiro; Ito, Tanio; Tsumura, Noriko; Kaneda, Heitaro

    2016-06-01

    The Kanto Basin, the largest lowland in Japan, developed by flexure as a result of (1) the subduction of the Philippine Sea (PHS) and the Pacific (PAC) plates and (2) the repeated collision of the Izu-Bonin arc fragments with the Japanese island arc. Geomorphological, geological, and thermochronological data on vertical movements over the last 1 My suggest that subsidence initially affected the entire basin after which the area of subsidence gradually narrowed until, finally, the basin began to experience uplift. In this study, we modeled the tectonic evolution of the Kanto Basin following the method of Matsu'ura and Sato (1989) for a kinematic subduction model with dislocations, in order to quantitatively assess the effects of PHS and PAC subduction. We include the steady slip-rate deficit (permanent locking rate at the plate interface) in our model to account for collision process. We explore how the latest collision of the Izu Peninsula block has been affected by a westerly shift in the PHS plate motion vector with respect to the Eurasian plate, thought to have occurred between 1.0-0.5 Ma, using long-term vertical deformation data to constrain extent of the locked zone on the plate interface. We evaluated the change in vertical deformation rate for two scenarios: (1) a synchronous shift in the orientation of the locked zone as PHS plate motion shifts and (2) a delayed shift in the orientation of the locked zone following the shift in plate motion. Observed changes in the uplift/subsidence pattern are better explained by scenario (2), suggesting that recent (< 1 My) deformation in the Kanto Basin shows a lag in crustal response to the plate motion shift. We also calculated stress accumulation rates and found a good match with observed earthquake mechanisms, which shows that intraplate earthquakes serve to release stress accumulated through long-term plate interactions.

  17. Global tectonics and space geodesy

    Science.gov (United States)

    Gordon, Richard G.; Stein, Seth

    1992-01-01

    Much of the success of plate tectonics can be attributed to the near rigidity of tectonic plates and the availability of data that describe the rates and directions of motion across narrow plate boundaries of about 1 to 60 kilometers. Nonetheless, many plate boundaries in both continental and oceanic lithosphere are not narrow but are hundreds to thousands of kilometers wide. Wide plate boundary zones cover approximately 15 percent of earth's surface area. Space geodesy, which includes very long baseline radio interferometry, satellite laser ranging, and the global positioning system, provides the accurate long-distance measurements needed to estimate the present motion across and within wide plate boundary zones. Space geodetic data show that plate velocities averaged over years are remarkably similar to velocities avaraged over millions of years.

  18. Acromioclavicular joint reconstruction by coracoid process transfer augmented with hook plate.

    Science.gov (United States)

    Wang, Yeming; Zhang, Jianguo

    2014-06-01

    Various techniques have been reported for the treatment of chronic acromioclavicular (AC) joint separation. The purpose of this study was to evaluate the results of surgical construction of coracoclavicular ligament using coracoid process transfer augmented with a hook plate fixation. Twenty-one patients treated with coracoid process transfer augmented with a hook plate fixation for chronic type III and V AC injuries were retrospectively analysed in 2003-2009. The age of the patients ranged from 23 to 58 years with an average age of 41.6 years. The patients were followed up clinically and radiographically, with an average of 33.0 months. Functional status and the ability to return to work were recorded during follow-up. Constant score and visual analogue scale (VAS) for pain were measured. The mean Constant score has increased from 70.9 points preoperatively to 90.7 points at follow-up. The mean VAS score has decreased from 4.7 preoperatively to 1.2 at follow-up. The average abduction was 172°, forward flexion was 170° and external rotation was 56°. There were 10 excellent results, 10 good results and one fair result. All patients had resumed their job or returned to original sport activity at mean 3.7 months postoperatively. No reduction loss was observed after plate removal and the final follow-up. Despite retrospective nature of the study, the outcomes of surgical construction with process transfer augmented with hook plate fixation are promising for chronic type III and V AC injuries. Therapeutic level IV. Retrospective case series, treatment study. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Mantle constraints on the plate tectonic evolution of the Tonga-Kermadec-Hikurangi subduction zone and the South Fiji Basin region

    NARCIS (Netherlands)

    Schellart, W. P.; Spakman, W.

    The Tonga-Kermadec-Hikurangi subduction zone is a major plate boundary in the Southwest Pacific region, where the Pacific plate subducts westward underneath the Australian plate. Considerable controversy exists regarding the Cenozoic evolution of this subduction zone, its connection with the

  20. Mantle constraints on the plate tectonic evolution of the Tonga-Kermadec-Hikurangi subduction zone and the South Fiji Basin region

    NARCIS (Netherlands)

    Schellart, W.P.; Spakman, W.

    2012-01-01

    The Tonga–Kermadec–Hikurangi subduction zone is a major plate boundary in the Southwest Pacific region, where the Pacific plate subducts westward underneath the Australian plate. Considerable controversy exists regarding the Cenozoic evolution of this subduction zone, its connection with

  1. Reconstruction of large upper eyelid defects with a free tarsal plate graft and a myocutaneous pedicle flap plus a free skin graft.

    Science.gov (United States)

    Toft, Peter B

    2016-01-01

    To review and present the results of a one-step method employing a free tarsal plate graft and a myocutaneous pedicle flap plus a free skin graft for reconstruction of large upper eyelid defects after tumour surgery. This was a retrospective case-series of 8 patients who underwent reconstruction of the upper eyelid after tumour removal. The horizontal defect involved 50-75% of the lid (3 pts.), more than 75% (3 pts.), and more than 75% plus the lateral canthus (2 pts.). The posterior lamella was reconstructed with contralateral upper eyelid tarsal plate. The anterior lamella was reconstructed with a laterally based myocutaneous pedicle flap in 7 patients, leaving a raw surface under the brow which was covered with a free skin graft. In 1 patient with little skin left under the brow, the anterior lamella was reconstructed with a bi-pedicle orbicularis muscle flap together with a free skin graft. All patients healed without necrosis, did not suffer from lagophthalmos, achieved reasonable cosmesis, and did not need lubricants. In one patient, a contact lens was necessary for three weeks because of corneal erosion. One patient still needs a contact lens 3 months after excision to avoid eye discomfort. Large upper eyelid defects can be reconstructed with a free tarsal plate graft and a laterally based myocutaneous pedicle flap in combination with a free skin graft. Two-step procedures can probably be avoided in most cases.

  2. Seafloor morphology of the Eurasia-Nubia (Africa) plate boundary between the Tore-Madeira Rise and the Straits of Gibraltar: a case of coexistent Mesozoic through Present day features of tectonic, oceanographic and sedimentary origin

    Science.gov (United States)

    Terrinha, Pedro; Duarte, João.; Valadares, Vasco; Batista, Luis; Zitellini, Nevio; Grácia, Eulalia; Lourenço, Nuno; Rosas, Filipe; Roque, Cristina

    2010-05-01

    The joint use of more than 10.000 km multichannel seismic reflection profiles and 180.000km2 of multibeam swath bathymetry and backscatter allowed for a new vision of the seafloor tectonic and geomorphic processes of the area that encompasses the present day plate boundary between Africa and Eurasia, between the Gibraltar Straits and the Tore-Madeira Rise, in the southern sector of the North Atlantic Ocean. The interpretation of this data allowed for the detailed description of the seafloor morphology (i.e. a morphologic map) and the classification of the morphologic features in what respects the genetic process and age. It can be seen that in the same region coexist morphologic features that result from tectonic processes associated with the Triassic-Cretaceous break-up of Pangea, the Paleogene-Miocene compressive phase, the Miocene through Present subduction under the Gibraltar Arc (Gutscher et al., 2002), the Pliocene-Quaternary wrench tectonics and possible coeval plate boundary (Zitellini et al., 2009), the Present day mud volcanism and propagation of the compressive deformation along the West Continental Margin of Portugal (Terrinha et al., 2009). Interpretation of the seismic profiles together with the bathymetry allows the understanding of endogenous and exogenous processes that creates reliefs associated with active structures (related to the Miocene through Present compressive stress field). Other reliefs generated in Mesozoic times by analogous processes can be as well preserved as these active ones. In what concerns exogenous processes, the analysis of the two datasets (reflection seismics and bathymetry) allowed for the description of morphologic features associated with oceanic currents that interact with the seafloor forming these important features. As is the case of the well known active contourites but also less known features, like giant scours at 4 km water depth that have recently been described, suggesting the interaction of deep currents and

  3. Petrogenesis and tectonic association of rift-related basic Panjal dykes from the northern Indian plate, North-Western Pakistan: evidence of high-Ti basalts analogous to dykes from Tibet

    Science.gov (United States)

    Sajid, Muhammad; Andersen, Jens; Arif, Mohammad

    2017-10-01

    Rift related magmatism during Permian time in the northern margin of Indian plate is represented by basic dykes in several Himalayan terranes including north western Pakistan. The field relations, mineralogy and whole rock geochemistry of these basic dykes reveal significant textural, mineralogical and chemical variation between two major types (a) dolerite and (b) amphibolite. Intra-plate tectonic settings for both rock types have been interpreted on the basis of low Zr/Nb ratios (primitive mantle using Dy/Yb, La/Yb, Sm/Yb and La/Sm ratios show that amphibolite formed by smaller degrees (< 5%) of partial melting than the dolerites (< 10%). The trace elements ratios suggest the origination of dolerites from the subcontinental lithospheric mantle with some crustal contamination. This is consistent with a petrogenetic relationship with Panjal trap magmatism, reported from Kashmir and other parts of north western India. The amphibolites, in contrast, show affinity towards Ocean Island basalts (OIB) with a relatively deep asthenospheric mantle source and minimal crustal contribution and are geochemically similar to the High-Ti mafic dykes of southern Qiangtang, Tibet. These similarities combined with Permian tectonic restoration of Gondwana indicate the coeval origin for both dykes from distinct mantle source during continental rifting related to formation of the Neotethys Ocean.

  4. Petrogenesis and tectonic association of rift-related basic Panjal dykes from the northern Indian plate, North-Western Pakistan: evidence of high-Ti basalts analogous to dykes from Tibet

    Science.gov (United States)

    Sajid, Muhammad; Andersen, Jens; Arif, Mohammad

    2018-06-01

    Rift related magmatism during Permian time in the northern margin of Indian plate is represented by basic dykes in several Himalayan terranes including north western Pakistan. The field relations, mineralogy and whole rock geochemistry of these basic dykes reveal significant textural, mineralogical and chemical variation between two major types (a) dolerite and (b) amphibolite. Intra-plate tectonic settings for both rock types have been interpreted on the basis of low Zr/Nb ratios (evolution of dolerites, which also show depletion in rare earth elements (REEs) and other incompatible elements compared to the amphibolites. The equilibrium partial melting models from primitive mantle using Dy/Yb, La/Yb, Sm/Yb and La/Sm ratios show that amphibolite formed by smaller degrees (< 5%) of partial melting than the dolerites (< 10%). The trace elements ratios suggest the origination of dolerites from the subcontinental lithospheric mantle with some crustal contamination. This is consistent with a petrogenetic relationship with Panjal trap magmatism, reported from Kashmir and other parts of north western India. The amphibolites, in contrast, show affinity towards Ocean Island basalts (OIB) with a relatively deep asthenospheric mantle source and minimal crustal contribution and are geochemically similar to the High-Ti mafic dykes of southern Qiangtang, Tibet. These similarities combined with Permian tectonic restoration of Gondwana indicate the coeval origin for both dykes from distinct mantle source during continental rifting related to formation of the Neotethys Ocean.

  5. Ensemble Kalman filter for the reconstruction of the Earth's mantle circulation

    Science.gov (United States)

    Bocher, Marie; Fournier, Alexandre; Coltice, Nicolas

    2018-02-01

    Recent advances in mantle convection modeling led to the release of a new generation of convection codes, able to self-consistently generate plate-like tectonics at their surface. Those models physically link mantle dynamics to surface tectonics. Combined with plate tectonic reconstructions, they have the potential to produce a new generation of mantle circulation models that use data assimilation methods and where uncertainties in plate tectonic reconstructions are taken into account. We provided a proof of this concept by applying a suboptimal Kalman filter to the reconstruction of mantle circulation (Bocher et al., 2016). Here, we propose to go one step further and apply the ensemble Kalman filter (EnKF) to this problem. The EnKF is a sequential Monte Carlo method particularly adapted to solve high-dimensional data assimilation problems with nonlinear dynamics. We tested the EnKF using synthetic observations consisting of surface velocity and heat flow measurements on a 2-D-spherical annulus model and compared it with the method developed previously. The EnKF performs on average better and is more stable than the former method. Less than 300 ensemble members are sufficient to reconstruct an evolution. We use covariance adaptive inflation and localization to correct for sampling errors. We show that the EnKF results are robust over a wide range of covariance localization parameters. The reconstruction is associated with an estimation of the error, and provides valuable information on where the reconstruction is to be trusted or not.

  6. Mandibular Reconstruction Using Pectoralis Major Myocutaneous Flap and Titanium Plates after Ablative Surgery for Locally Advanced Tumors of the Oral Cavity

    International Nuclear Information System (INIS)

    El-Zohairy, M.A.F.; Mostafa, A.; Amin, A.; Abd El-Fattah, H.; Khalifa, Sh.

    2009-01-01

    The most common indication for mandible resection remains ablative surgery for cancer of the oral cavity and oropharynx. The use of vascularized bone grafts has become state-of-the-art for mandibular reconstruction. However, the high cost of such surgery may not be justified in patients with advanced disease and poor prognosis, or poor performance status. Objective: The purpose of this study was to evaluate outcomes of mandibular reconstruction using titanium plates covered with a pedicled pectoralis major myocutaneous flap after ablative surgery for locally advanced tumors of the oral cavity. Patients and methods: The study involves a total of 33 patients with locally advanced tumors of the oral cavity that were treated over 5 year period (2003-2008) at the National Cancer Institute, Cairo University, Egypt. Mandibular resections were performed for treatment of patients with primary oral cavity tumors invading the mandible followed by mandibular reconstruction using titanium plates covered with a pedicled pectoralis major myocutaneous flap. Results: Of 33 patients, 25 (75.75%) were males and 8 (24.25%) were females. The age ranged from 42 to 70 years (mean 52.3±5.9 years). Tongue cancer was the most common tumor, it affects 17 (51.5%) of the patients, 24 patients received post operative radiation therapy. The flap survival was 100%; partial necrosis of the flap skin was observed in 3 patients. One patient developed wound dehiscence. Oro-cutaneous fistula occurred in 5 patients that closed spontaneously. There were 4 cases of plate failure, one patient experienced plate fracture at 13 months after reconstruction. Three patients developed external plate exposure. All patients achieved good functional and acceptable aesthetic outcome. The overall cause-specific cumulative survival was 72.7% at one year and 56.1% at two years. Conclusions: Titanium plate and pedicled pectoralis major myocutaneous flap is a safe and reliable option for composite mandibular defects

  7. Segmental Mirroring: Does It Eliminate the Need for Intraoperative Readjustment of the Virtually Pre-Bent Reconstruction Plates and Is It Economically Valuable?

    Science.gov (United States)

    Khalifa, Ghada Amin; Abd El Moniem, Nahed Adly; Elsayed, Shadia Abd-ElHameed; Qadry, Yara

    2016-03-01

    The aim of this study was to compare segmental mirroring with mirroring of the entire unaffected side to determine which method obviates intraoperative readjustment of virtually planned pre-bent plates and to evaluate the effect on costs. Patients eligible for inclusion in this prospective study had unilateral mandibular discontinuity defects. Patients were randomly divided into 2 groups. In group I, models were constructed by mirroring the entire unaffected side of the mandible at the midsagittal plane. In group II, only the resected segments were cut and replaced by the corresponding mirrored healthy segments. The lesions were resected, and their sites were reconstructed using pre-bent reconstruction plates. The need for intraoperative plate readjustment, plate placement time, operation time, and operation costs were reviewed. Fifty patients were enrolled in this study. All but 5 plates in group I required readjustment. In group II, plates were placed without intraoperative handling. Average operating times were 4.20 ± 0.56 hours in group I and 3.186 ± 0.28 hours in group II (P = .00002). Mean times for plate placement were 33.36 ± 8.20 and 21.88 ± 5.73 minutes in groups I and II, respectively. The difference resulted in an average time gain of 11.48 minutes. Average personal costs per minute were US$740.77 for group I and US$560.87 for group II. The difference resulted in an average saving of approximately US$179.90. Segmental mirroring is superior in reflecting the bone anatomy in 3-dimensional models, thus eliminating intraoperative plate readjustment and providing better plate adaptation with better contour. It decreases operating time and costs and thus can be recommended for lesions that do not cross the midline. Copyright © 2016 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  8. Tectonic Geomorphology.

    Science.gov (United States)

    Bull, William B.

    1984-01-01

    Summarizes representative quantitative tectonic-geomorphology studies made during the last century, focusing on fault-bounded mountain-front escarpments, marine terraces, and alluvial geomorphic surfaces (considering stream terraces, piedmont fault scarps, and soils chronosequences). Also suggests where tectonic-geomorphology courses may best fit…

  9. Textile Tectonics

    DEFF Research Database (Denmark)

    Mossé, Aurélie

    2008-01-01

    of the discipline. Inspiring time gathering some of the most exciting architects of the moment, Lars Spuybroeck, Mark Burry, Evan Douglis, Michael Hensel and Cecil Balmond were invited to discuss their understanding of tectonics. Full text available at http://textilefutures.co.uk/exchange/bin/view/TextileFutures/TextileTectonics...

  10. New aero-gravity results from the Arctic: Linking the latest Cretaceous-early Cenozoic plate kinematics of the North Atlantic and Arctic Ocean

    DEFF Research Database (Denmark)

    Døssing, Arne; Hopper, J.R.; Olesen, Arne Vestergaard

    2013-01-01

    The tectonic history of the Arctic Ocean remains poorly resolved and highly controversial. Details regarding break up of the Lomonosov Ridge from the Barents-Kara shelf margins and the establishment of seafloor spreading in the Cenozoic Eurasia Basin are unresolved. Significantly, the plate...... tectonic evolution of the Mesozoic Amerasia Basin is essentially unknown. The Arctic Ocean north of Greenland is at a critical juncture that formed at the locus of a Mesozoic three-plate setting between the Lomonosov Ridge, Greenland, and North America. In addition, the area is close to the European plate...... plateau against an important fault zone north of Greenland. Our results provide new constraints for Cretaceous-Cenozoic plate reconstructions of the Arctic. Key Points Presentation of the largest aero-gravity survey acquired over the Arctic Ocean Plate tectonic link between Atlantic and Arctic spreading...

  11. The Additively Manufactured Porous NiTi and Ti-6Al-4V in Mandibular Reconstruction: Introducing the Stiffness-Matched and the Variable Stiffness Options for the Reconstruction Plates

    Science.gov (United States)

    Jahadakbar, Ahmadreza

    Mandibular reconstruction surgery is a part of treatment for cancer, tumor, and all the cases that involve segmental defects. One of the most common approaches for the reconstruction surgery is to resect the segmental defect and use a double barrel fibula graft to fill the resected region and recover the mandible's normal functions, such as chewing. The grafted bone is connected to the host mandible, using the standard of the care Ti-6Al-4V fixation plates. The fixation plates are available in the form of prefabricated plates and also patient-specific plates in the market. Due to the high stiffness of the Ti-6Al-4V plates in comparison with the mandible bone and the grafted bone, the loading distribution on the whole reconstructed mandible will be different from a healthy mandible. The high stiffness fixation hardware carries a great portion of the loading and causes stress shielding on the grafted bone and the surrounding host bone. Based on the bone remodeling theory, the stress shielding on the cortical bone causes bone resorption and may lead to implant failure. A solution to reduce the risk of implant failure is to use a low stiffness biocompatible material for the mandibular fixation plates. We have proposed the use of stiffness-matched, porous NiTi fixation plates either in the form of patient-specific or prefabricated, instead of the standard of the care Ti-6Al-4V plates. NiTi is a biocompatible material that has a low stiffness in comparison with Ti-6Al-4V and also benefits from the superelastic feature. Superelasticity, which can also be found in bone tissues, allows the material to recover large strains (up to 8%) and increases the shock absorption. In this thesis, we have evaluated the use of proposed fixation hardware by comparing it with a healthy mandible and a reconstructed mandible using the standard method. To this end, first different models including a healthy mandible, a reconstructed mandible using patient-specific Ti-6Al-4V fixation hardware

  12. Note on: "Inevitability of Plate Tectonics on Super-Earths" by Valencia, O Connell and Sasselov, arXiv preprint 0710.0699

    OpenAIRE

    Omerbashich, Mensur

    2008-01-01

    Valencia et al. recently claimed that the mass of a Super-Earth (SE) is a sole factor in determining whether a SE is tectonically active or not. However, mass resolving astrometry is unable to discern between a SE and its moons if any. The fact that no exomoons have been discovered yet is rather a matter of instrumentation imperfection at the present, not of physical absence of exomoons. This, with recently discovered relationships between geometric and physical properties in astronomical bod...

  13. Tectonic and metamorphic discontinuities in the Greater Himalayan Sequence in Central Himalaya: in-sequence shearing by accretion from the Indian plate

    Science.gov (United States)

    Carosi, Rodolfo

    2016-04-01

    The Greater Himalayan Sequence (GHS) is the main metamorphic unit of the Himalayas, stretching for over 2400 km, bounded to the South by the Main Central Thrust (MCT) and to the North by the South Tibetan Detachment (STD) whose contemporanous activity controlled its exhumation between 23 and 17 Ma (Godin et al., 2006). Several shear zones and/or faults have been recognized within the GHS, usually regarded as out of sequence thrusts. Recent investigations, using a multitechnique approach, allowed to recognize a tectonic and metamorphic discontinuity, localized in the mid GHS, with a top-to-the SW sense of shear (Higher Himalayan Discontinuity: HHD) (Carosi et al., 2010; Montomoli et al., 2013). U-(Th)-Pb in situ monazite ages provide temporal constraint of the acitivity of the HHD from ~ 27-25 Ma to 18-17 Ma. Data on the P and T evolution testify that this shear zone affected the tectono-metamorphic evolution of the belt and different P and T conditions have been recorded in the hanging-wall and footwall of the HHD. The HHD is a regional tectonic feature running for more than 700 km, dividing the GHS in two different portions (Iaccarino et al., 2015; Montomoli et al., 2015). The occurrence of even more structurally higher contractional shear zone in the GHS (above the HHD): the Kalopani shear zone (Kali Gandaki valley, Central Nepal), active from ~ 41 to 30 Ma (U-Th-Pb on monazite) points out to a more complex deformation pattern in the GHS characterized by in sequence shearing. The actual proposed models of exhumation of the GHS, based exclusively on the MCT and STD activities, are not able to explain the occurrence of the HHD and other in-sequence shear zones. Any model of the tectonic and metamorphic evolution of the GHS should account for the occurrence of the tectonic and metamorphic discontinuities within the GHS and its consequences on the metamorphic paths and on the assembly of Himalayan belt. References Godin L., Grujic D., Law, R. D. & Searle, M. P. 2006

  14. Digital Tectonics

    DEFF Research Database (Denmark)

    Christiansen, Karl; Borup, Ruben; Søndergaard, Asbjørn

    2014-01-01

    Digital Tectonics treats the architectonical possibilities in digital generation of form and production. The publication is the first volume of a series, in which aspects of the strategic focus areas of the Aarhus School of Architecture will be disseminated.......Digital Tectonics treats the architectonical possibilities in digital generation of form and production. The publication is the first volume of a series, in which aspects of the strategic focus areas of the Aarhus School of Architecture will be disseminated....

  15. The free vascularized flap and the flap plate options: comparative results of reconstruction of lateral mandibular defects

    NARCIS (Netherlands)

    Shpitzer, T.; Gullane, P. J.; Neligan, P. C.; Irish, J. C.; Freeman, J. E.; van den Brekel, M.; Gur, E.

    2000-01-01

    OBJECTIVES/HYPOTHESIS: Reconstruction of the mandible and oral cavity after segmental resection is a challenging surgical problem. Although osteocutaneous free flaps are generally accepted to be optimal for reconstruction of anterior defects, the need for bony reconstruction for a pure lateral

  16. Everyday Tectonics?

    DEFF Research Database (Denmark)

    Beim, Anne; Hvejsel, Marie Frier

    2016-01-01

    Frascari and Kenneth Frampton (Harris & Berke 1997, Read 2000, Frascari 1984, Frampton 1995kilder). Whereas the focus upon everyday architecture seems to have lost its momentum too quickly, tectonic theory in architecture has been steadily growing as a field of research in architecture, especially related...

  17. [EFFECTIVENESS COMPARISON OF CORACOCLAVICULAR LIGAMENT RECONSTRUCTION BETWEEN BY AUTOLOGOUS AND ALLOGENEIC TENDON GRAFTS COMBINED WITH HOOK PLATE FIXATION FOR TREATING ACROMIOCLAVICULAR JOINT DISLOCATION].

    Science.gov (United States)

    Yin, Fei; Sun, Zhenzhong; Wei, Xuming; Liu, Xueguang; Zhou, Ming; Zhuang, Yin; Song, Sheng

    2016-05-08

    To compare the effectiveness of coracoclavicular ligament reconstruction between by using autologous plantaris tendon graft combined with hook plate fixation and allogeneic tendon graft combined with hook plate fixation for treating acromiocavicular joint dislocation. Thirty-three patients with acromioclavicular joint dislocation who accorded with the inclusion criteria between January 2013 and June 2014 were assigned into 2 groups. The patients were treated with autologous plantaris tendon graft combined with hook plate fixation in group A ( n =17), and with allogeneic tendon graft combined with hook plate fixation in group B ( n =16). Thirteen-one patients was followed up more than 12 months (15 in group A and 16 in group B). There was no significant difference in gender, age, cause of injury, sides, time between injury and surgery, and type of dislocation ( P >0.05). The assessments included operation time, hospitalization time, hospitalization expenses, shoulder range of motion, gap of acromioclavicular, Constant-Murley scores, and visual analogue scale (VAS) for pain. The operation time of group A was significantly longer than that of group B, and the hospitalization expense was significantly lower than that of group B ( P 0.05). No redislocation of acromioclavicular joint and rejection reaction occurred during follow-up. At last follow-up, there was no significant difference in shoulder range of motion, Constant-Murley score, and VAS score between 2 groups ( P >0.05). Coracoclavicular ligament reconstruction by autologous plantaris tendon or allogeneic tendon graft combined with hook plate fixation for the treatment of acromioclavicular joint dislocation can achieve good effectiveness. The appropriate treatment should be chosen according to the patient's economic situation.

  18. Chest wall stabilization and reconstruction: short and long-term results 5 years after the introduction of a new titanium plates system.

    Science.gov (United States)

    De Palma, Angela; Sollitto, Francesco; Loizzi, Domenico; Di Gennaro, Francesco; Scarascia, Daniele; Carlucci, Annalisa; Giudice, Giuseppe; Armenio, Andrea; Ludovico, Rossana; Loizzi, Michele

    2016-03-01

    We report short and long-term results with the dedicated Synthes(®) titanium plates system, introduced 5 years ago, for chest wall stabilization and reconstruction. We retrospectively analyzed (January 2010 to December 2014) 27 consecutive patients (22 males, 5 females; range 16-83 years, median age 60 years), treated with this system: primary [3] and secondary [8] chest wall tumor; flail chest [5]; multiple ribs fractures [5]; sternal dehiscence-diastasis [3]; sternal fracture [1]; sternoclavicular joint dislocation [1]; Poland syndrome [1]. Short-term results were evaluated as: operating time, post-operative morbidity, mortality, hospital stay; long-term results as: survival, plates-related morbidity, spirometric values, chest pain [measured with Verbal Rating Scale (VRS) and SF12 standard V1 questionnaire]. Each patient received from 1 to 10 (median 2) titanium plates/splints; median operating time was 150 min (range: 115-430 min). Post-operative course: 15 patients (55.6%) uneventful, 10 (37%) minor complications, 2 (7.4%) major complications; no post-operative mortality. Median post-operative hospital stay was 13 days (range: 5-129 days). At a median follow-up of 20 months (range: 1-59 months), 21 patients (78%) were alive, 6 (22%) died. Three patients presented long-term plates-related morbidity: plates rupture [2], pin plate dislodgment [1]; two required a second surgical look. One-year from surgery median spirometric values were: FVC 3.31 L (90%), FEV1 2.46 L (78%), DLCO 20.9 mL/mmHg/min (76%). On 21 alive patients, 7 (33.3%) reported no pain (VRS score 0), 10 (47.6%) mild (score 2), 4 (19.1%) moderate (score 4), no-one severe (score >4); 15 (71.5%) reported none or mild, 6 (28.5%) moderate pain influencing quality of life. An optimal chest wall stabilization and reconstruction was achieved with the Synthes(®) titanium plates system, with minimal morbidity, no post-operative mortality, acceptable operating time and post-operative hospital stay. Long

  19. Sea level and shoreline reconstructions for the Red Sea: isostatic and tectonic considerations and implications for hominin migration out of Africa

    Science.gov (United States)

    Lambeck, Kurt; Purcell, Anthony; Flemming, Nicholas. C.; Vita-Finzi, Claudio; Alsharekh, Abdullah M.; Bailey, Geoffrey N.

    2011-12-01

    The history of sea level within the Red Sea basin impinges on several areas of research. For archaeology and prehistory, past sea levels of the southern sector define possible pathways of human dispersal out of Africa. For tectonics, the interglacial sea levels provide estimates of rates for vertical tectonics. For global sea level studies, the Red Sea sediments contain a significant record of changing water chemistry with implications on the mass exchange between oceans and ice sheets during glacial cycles. And, because of its geometry and location, the Red Sea provides a test laboratory for models of glacio-hydro-isostasy. The Red Sea margins contain incomplete records of sea level for the Late Holocene, for the Last Glacial Maximum, for the Last Interglacial and for earlier interglacials. These are usually interpreted in terms of tectonics and ocean volume changes but it is shown here that the glacio-hydro-isostatic process is an additional important component with characteristic spatial variability. Through an iterative analysis of the Holocene and interglacial evidence a separation of the tectonic, isostatic and eustatic contributions is possible and we present a predictive model for palaeo-shorelines and water depths for a time interval encompassing the period proposed for migrations of modern humans out of Africa. Principal conclusions include the following. (i) Late Holocene sea level signals evolve along the length of the Red Sea, with characteristic mid-Holocene highstands not developing in the central part. (ii) Last Interglacial sea level signals are also location dependent and, in the absence of tectonics, are not predicted to occur more than 1-2 m above present sea level. (iii) For both periods, Red Sea levels at 'expected far-field' elevations are not necessarily indicative of tectonic stability and the evidence points to a long-wavelength tectonic uplift component along both the African and Arabian northern and central sides of the Red Sea. (iv) The

  20. On the Marija Reka mercury deposit and on its comparison with the Litija and Idrija deposits from the aspect of plate tectonics

    Directory of Open Access Journals (Sweden)

    Ivan Mlakar

    1995-12-01

    Full Text Available The surroundings of the Marija Reka deposit were studied in detail, and on the basis of literature data its geologic structure was reconstructed.The chemical elements Ni and Hg are correlated, and therefore comparisons were made with the deposits in Sava folds in which also mercury occurs. Positive correlation was established between the intensity of extension of the Earth's crust, occurrence of basic volcanics, and nickel and native mercury. Results indicatethe deep-seated source of these elements, and the Permian age of the Marija Reka deposit.By considering numerous geochemical data new views on the perspective of the deposit were expressed.

  1. Formwork tectonics

    DEFF Research Database (Denmark)

    Manelius, Anne-Mette

    2012-01-01

    På engelsk: Based on the concept of techné and framed in architectural studies of tectonics and an experimental practice of making, this paper investigates the multiple technological roles of textiles in fabric formwork for concrete in four analytical studies of experimental data of the author......’s doctoral dissertation Fabric Formwork for Concrete – Investigations into Formwork Tectonics and Stereogeneity in Architectural Constructions. In the paper only textile roles are discussed but it is suggested that a study of multiple technological roles of key formwork elements will emphasize...... their potential as ‘common denominators’ between architects, engineers and builders. Findings include textile used for the ‘textilization’ of concrete and the ‘concretization’ of textiles as two opposite starting points in fabric-forming. Recent research into thin-shell construction using fabric formwork is shown...

  2. Tectonic tremor

    Science.gov (United States)

    Shelly, David R.

    2016-01-01

    Tectonic, non-volcanic tremor is a weak vibration of ground, which cannot be felt by humans but can be detected by sensitive seismometers. It is defined empirically as a low-amplitude, extended duration seismic signal associated with the deep portion (∼20–40 km depth) of some major faults. It is typically observed most clearly in the frequency range of 2–8 Hz and is depleted in energy at higher frequencies relative to regular earthquakes.

  3. Essai de reconstitution de l'histoire géologique et structurale de la Méditerranée centrale Attempt to Reconstruct the Geological Tectonics and Intraplate Deformations

    Directory of Open Access Journals (Sweden)

    Schuster J. -M.

    2006-11-01

    Full Text Available La Méditerranée centrale (mer Ionienne occupe une position charnière entre le craton africain au sud et les chaînes de l'arc alpin au nord. La zone étudiée s'étend globalement de l'escarpement maltais à l'ouest, à l'extrémité orientale de la Crête à l'est. Elle se localise à l'aplomb du secteur profond de la Méditerranée centrale. On y distingue cinq unités structurales majeures : le bassin de Syrte, la plaine abyssale ionienne, le cône de Messine, la ride méditerranéenne et le fossé hellénique. La synthèse des éléments géophysiques et géologiques et des mouvements supposés des plaques africaine et eurasienne permet d'esquisser une reconstitution de l'histoire géologique et structurale de la Méditerranée centrale que l'on peut diviser en trois périodes: Trias-Paléocène, Éocène-Miocène, Plio-Quaternaire. Deux tectoniques y prennent place. L'une, protoméditerranéenne (téthysienne, mésogéenne, créatrice des chaînes périméditerranéennes s'étend tout au long des deux premières périodes (Trias à Miocène. L'autre, méditerranéenne, édificatrice de la Mer Méditerranée couvre la deuxième et la troisième période (Éocène à Quaternaire. The central Mediterranean (lonian Sea forms the uncture between the African croton in the S and the ranges of the Alpine arc in the . The zone examined stretches from the Maltese escarpment in the W ta the eastern M of Crete in the E. It is situated directly on top of the deep sector of the central editerranean. Five major structural units can be distinguished there, i.e. the Syrtis Basin, the lonian abyssal plain, the Messina cone, the Mediterranean ridge and the Hellenic trough. A synthesis of the geophysical and geological elements and of the assumed move-mentsoftheAfrican and Eurasion plates has been used ta sketch out a reconstruction of the geological and structural history of the central Mediterranean which can be divided into three periods : Trias

  4. Reconstruction of large upper eyelid defects with a free tarsal plate graft and a myocutaneous pedicle flap plus a free skin graft

    DEFF Research Database (Denmark)

    Toft, Peter B

    2016-01-01

    skin graft. RESULTS: All patients healed without necrosis, did not suffer from lagophthalmos, achieved reasonable cosmesis, and did not need lubricants. In one patient, a contact lens was necessary for three weeks because of corneal erosion. One patient still needs a contact lens 3 months after...... excision to avoid eye discomfort. CONCLUSION: Large upper eyelid defects can be reconstructed with a free tarsal plate graft and a laterally based myocutaneous pedicle flap in combination with a free skin graft. Two-step procedures can probably be avoided in most cases....

  5. Numerical Simulation of the Borehole Magnetic Field for Resolving the Possible Rotation of Tectonic Basins and Plates during ICDP and IODP Experiments

    Science.gov (United States)

    Lee, S. M.; Parq, J. H.

    2017-12-01

    An accurate measurement of magnetic field inside the borehole, together with a right set of paleomagnetic measurements on the recovered core samples, should allow one to resolve important elements such as the rotation of the basin or the plate on which the basin is located. The ability to resolve the rotation of the basin can be crucial during drilling experiments by International Continental Scientific Drilling Program (ICDP) and International Ocean Discovery Program (IODP). A good example where the rotation is a central question is the Philippine Sea Plate, which is thought to have rotated about 90° clockwise during the last 55 million years. Despite the significance, previous borehole magnetometers were not accurate enough to achieve such a goal because, among various technical issues, determining the orientation of the sensor inside the borehole to a very high level of accuracy was not easy. The next-generation (third-generation) borehole magnetometer (3GBM) was developed to overcome this difficulty and to bring paleomagnetic investigations to a new level. Even with the new development, however, there are still concerns whether the new instrument can really resolve the rotation because the magnetic field anomalies generated by the sediment is generally very low. In this paper, we present numerical simulations based on finite element method of the magnetic field inside the borehole that were conducted as part of a test to demonstrate that, despite low levels of magnetization, the magnetic fields can be resolved. The results also served as an important input on the design requirements of the borehole magnetometer. Various cases were considered, including the situation where the sedimentary layer is horizontal and inclined. We also explored the cases where volcanic sills were present within the sedimentary layer as they may provide a greater magnetic signature than having sediment alone, and thus improving our chances of determining the rotation. Simulations are

  6. Middle-term follow-up results of Pipkin type IV femoral head fracture patients treated by reconstruction plate and bioabsorbable screws

    Directory of Open Access Journals (Sweden)

    Shan-Xi Wang

    2018-06-01

    Full Text Available Purpose: To investigate the mid-term curative effects of the treatment of Pipkin type IV femoral head fractures using a reconstruction plate and bioabsorbable screws and provide the evidence for clinical practice. Methods: From February 2010 to September 2014, 21 patients with Pipkin type IV femoral head fractures were treated surgically. There were 13 males and 8 females with an average age of 41.1 years (range, 20–65 years. The causes of the fractures included traffic accidents (13 cases, falls from a height (four cases, heavy lifting injuries (three cases, and sport injury (one case. All patients were followed up with radiography and three-dimensional reconstruction computed tomography and other checks and any complications were actively managed. Closed reduction of fracture-dislocation of the hip was attempted under general anesthesia using the Kocher-Langenbeck approach. Femoral head fractures were treated with internal fixation or excision based on the size of the fracture fragments, whereas acetabular fractures were fixed with a reconstruction plate and screws following anatomic reduction. Results: The incisions healed by primary intention in all patients after surgery, without any infection, deep venous thrombosis, or other complications. All 21 patients were followed up for 36–76 months, with an average follow-up duration of 49 months. Postoperative imaging data showed that all dislocations and fractures were anatomically reduced, and bony union of the fractures was achieved. Heterotopic ossification was found in four patients, post-traumatic osteoarthritis in three, and avascular necrosis of the femoral head in two. At the final follow-up, the assessment of hip joint function according to the Thompson-Epstein scoring scale was excellent in 10 cases, good in six cases, fair in three cases, and poor in two cases. The rate of excellent and good functional outcomes was 76.1%. Conclusion: The mid-term curative effects of a

  7. [Efficacy of Sacroiliac Joint Anterior Approach with Double Reconstruction Plate and Computer Assisted Navigation Percutaneous Sacroiliac Screw for Treating Tile C1 Pelvic Fractures].

    Science.gov (United States)

    Tan, Zhen; Fang, Yue; Zhang, Hui; Liu, Lei; Xiang, Zhou; Zhong, Gang; Huang, Fu-Guo; Wang, Guang-Lin

    2017-09-01

    To compare the efficacy of sacroiliac joint anterior approach with double reconstruction plate and computer assisted navigation percutaneous sacroiliac screw for treating Tile C1 pelvic fractures. Fifty patients with pelvic Tile C1 fractures were randomly divided into two groups ( n =25 for each) in the orthopedic department of West China Hospital of Sichuan University from December 2012 to November 2014. Patients in group A were treated by sacroiliac joint dislocation with anterior plate fixation. Patients in group B were treated with computerized navigation for percutaneous sacroiliac screw. The operation duration,intraoperative blood loss,incision length,and postoperative complications (nausea,vomiting,pulmonary infection,wound complications,etc.) were compared between the two groups. The postoperative fracture healing time,postoperative patient satisfaction,and postoperative fractures MATTA scores (to evaluate fracture reduction),postoperative MAJEED function scores,and SF36 scores of the patients were also recorded and compared. No significant differences in baseline characteristics were found between the two groups of patients. All of the patients in both groups had their operations successfully completed. Patients in group B had significantly shorter operations and lower intraoperative blood loss,incision length and postoperative complications than those in group A ( P 0.05). Sacroiliac joint anterior approach with double reconstruction plate and computer assisted navigation percutaneous sacroiliac screws are both effective for treating Tile C1type pelvic fractures,with similar longterm efficacies. However,computer assisted navigation percutaneous sacroiliac screw has the advantages of less trauma,less bleeding,and quicker.

  8. [EFFECTIVENESS OF CLAVICULAR HOOK PLATE COMBINED WITH TRAPEZIUS MUSCLE FASCIA FOR RECONSTRUCTION OF ACROMIOCLAVICULAR AND CORACOCLAVICULAR LIGAMENTS TO TREAT COMPLETE ACROMIOCLAVICULAR JOINT DISLOCATION].

    Science.gov (United States)

    Wang, Chaoliang; Wang, Yingzhen; Zhu, Tao; Sun, Xuesheng; Lin, Chu; Gao, Bo; Li, Xinxia

    2015-02-01

    To explore the effectiveness of the clavicular hook plate combined with trapezius muscle fascia for reconstruction of acromioclavicular and coracoclavicular ligaments to treat acute complete acromioclavicular dislocations. Between January 2008 and April 2012, 66 patients with acromioclavicular dislocation were treated with the clavicular hook plate combined with trapezius muscle fascia for reconstruction of acromioclavicular and coracoclavicular ligaments in 32 cases (experimental group) and with the clavicular hook plate in 34 cases (control group). There was no significant difference in gender, age, injured side, the cause of injury, and the time from injury to operation between 2 groups (P > 0.05). Visual analogue scale (VAS), Constant shoulder scores, and coracoid clavi-cledistance (CC. Dist) were measured at preoperation and at 2 years after operation. Signal/noise quotiem (SNQ) was measured by MRI at 2 years after operation. The operation complications were observed. The patients of 2 groups obtained primary healing of incision. The morbidity of complication in experimental group (12.5%, 4/32) was significantly lower than that in control group (91.2%, 31/34) (Χ2 = 40.96, P = 0.00). All the cases were followed up 2.8 years on average (range, 2 to 4 years). VAS scores and CC.Dist significantly decreased at 2 years after operation when compared with preoperative values in the 2 groups (P acromioclavicular and coracoclavicular ligaments is successful in treating acute complete acromioclavicular dislocations, with the advantages of higher ligament healing, less complication, and early improvement of shoulder functions.

  9. Interdisciplinary approach to exploit the tectonic memory in the continental crust of collisional belts.

    Science.gov (United States)

    Gosso, G.; Marotta, A. M.; Rebay, G.; Regorda, A.; Roda, M.; Spalla, M. I.; Zanoni, D.; Zucali, M.

    2015-12-01

    Collisional belts result by thoroughly competing thermo-mechanical disaggregation and coupling within both continental and oceanic lithospheric slices, during construction of tectono-metamorphic architectures. In multiply reworked metamorphics, tectonic units may be contoured nowadays on the base of coherent thermo-baric and structural time-sequences rather than simply relying on lithologic affinities. Sequences of equilibrium assemblages and related fabric imprints are an approach that appears as a more reliable procedure, that enables to define tectonic units as the volume of crustal slices that underwent corresponding variations during the dynamics of an active margin and takes into account a history of physical imprints. The dimensions of these tectonic units may have varied over time and must be reconstructed combining the tracers of structural and metamorphic changes of basement rocks, since such kind of tectono-metamorphic units (TMUs) is a realistic configuration of the discrete portions of orogenic crust that experienced a coherent sequence of metamorphic and textural variations. Their translational trajectories, and bulk shape changes during deformation, cannot simply be derived from the analysis of the geometries and kinematics of tectonic units, but are to be obtained by adding the reconstruction of quantitative P-T-d-t paths making full use of fossil mineral equilibria. The joint TMU field-and-laboratory definition is an investigation procedure that bears a distinct thermo-tectonic connotation, that, through modelling, offers the opportunity to test the physical compatibilities of plate-scale interconnected variables, such as density, viscosity, and heat transfer, with respect to what current interpretative geologic histories may imply. Comparison between predictions from numerical modelling and natural data obtained by this analytical approach can help to solve ambiguities on geodynamic significance of structural and thermal signatures, also as a

  10. Post-Jurassic tectonic evolution of Southeast Asia

    Science.gov (United States)

    Zahirovic, Sabin; Seton, Maria; Dietmar Müller, R.; Flament, Nicolas

    2014-05-01

    The accretionary growth of Asia, linked to long-term convergence between Eurasia, Gondwana-derived blocks and the Pacific, resulted in a mosaic of terranes for which conflicting tectonic interpretations exist. Here, we propose solutions to a number of controversies related to the evolution of Sundaland through a synthesis of published geological data and plate reconstructions that reconcile both geological and geophysical constraints with plate driving forces. We propose that West Sulawesi, East Java and easternmost Borneo rifted from northern Gondwana in the latest Jurassic, collided with an intra-oceanic arc at ~115 Ma and subsequently sutured to Sundaland by 80 Ma. Although recent models argue that the Southwest Borneo core accreted to Sundaland at this time, we use volcanic and biogeographic constraints to show that the core of Borneo was on the Asian margin since at least the mid Jurassic. This northward transfer of Gondwana-derived continental fragments required a convergent plate boundary in the easternmost Tethys that we propose gave rise to the Philippine Archipelago based on the formation of latest Jurassic-Early Cretaceous supra-subduction zone ophiolites on Halmahera, Obi Island and Luzon. The Late Cretaceous marks the shift from Andean-style subduction to back-arc opening on the east Asian margin. Arc volcanism along South China ceased by ~60 Ma due to the rollback of the Izanagi slab, leading to the oceanward migration of the volcanic arc and the opening of the Proto South China Sea (PSCS). We use the Apennines-Tyrrhenian system in the Mediterranean as an analogue to model this back-arc. Continued rollback detaches South Palawan, Mindoro and the Semitau continental blocks from the stable east Asian margin and transfers them onto Sundaland in the Eocene to produce the Sarawak Orogeny. The extrusion of Indochina and subduction polarity reversal along northern Borneo opens the South China Sea and transfers the Dangerous Grounds-Reed Bank southward to

  11. Tectonic reactivation in the Indian Ocean: Evidences from seamount morphology and manganese nodule characteristics

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Khadge, N.H.

    The Central Indian Ocean Basin (CIOB) was subjected to tectonic reactivation in geological past which is unusual for a basin occurring on an apparently single tectonic plate. ENE-WSW trending latitude parallel zone of reactivation across the central...

  12. Differential preservation in the geologic record of intraoceanic arc sedimentary and tectonic processes

    Science.gov (United States)

    Draut, Amy; Clift, Peter D.

    2013-01-01

    Records of ancient intraoceanic arc activity, now preserved in continental suture zones, are commonly used to reconstruct paleogeography and plate motion, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records from ancient terranes after arc–continent collision is complicated by preferential preservation of evidence for some arc processes and loss of evidence for others. In this synthesis we examine what is lost, and what is preserved, in the translation from modern processes to the ancient record of intraoceanic arcs. Composition of accreted arc terranes differs as a function of arc–continent collision geometry. ‘Forward-facing’ collision can accrete an oceanic arc on to either a passive or an active continental margin, with the arc facing the continent and colliding trench- and forearc-side first. In a ‘backward-facing’ collision, involving two subduction zones with similar polarity, the arc collides backarc-first with an active continental margin. The preservation of evidence for contemporary sedimentary and tectonic arc processes in the geologic record depends greatly on how well the various parts of the arc survive collision and orogeny in each case. Preservation of arc terranes likely is biased towards those that were in a state of tectonic accretion for tens of millions of years before collision, rather than tectonic erosion. The prevalence of tectonic erosion in modern intraoceanic arcs implies that valuable records of arc processes are commonly destroyed even before the arc collides with a continent. Arc systems are most likely to undergo tectonic accretion shortly before forward-facing collision with a continent, and thus most forearc and accretionary-prism material in ancient arc terranes likely is temporally biased toward the final stages of arc activity, when sediment flux to the trench was greatest and tectonic accretion prevailed. Collision geometry

  13. Ensemble Kalman filter for the reconstruction of the Earth's mantle circulation

    Directory of Open Access Journals (Sweden)

    M. Bocher

    2018-02-01

    Full Text Available Recent advances in mantle convection modeling led to the release of a new generation of convection codes, able to self-consistently generate plate-like tectonics at their surface. Those models physically link mantle dynamics to surface tectonics. Combined with plate tectonic reconstructions, they have the potential to produce a new generation of mantle circulation models that use data assimilation methods and where uncertainties in plate tectonic reconstructions are taken into account. We provided a proof of this concept by applying a suboptimal Kalman filter to the reconstruction of mantle circulation (Bocher et al., 2016. Here, we propose to go one step further and apply the ensemble Kalman filter (EnKF to this problem. The EnKF is a sequential Monte Carlo method particularly adapted to solve high-dimensional data assimilation problems with nonlinear dynamics. We tested the EnKF using synthetic observations consisting of surface velocity and heat flow measurements on a 2-D-spherical annulus model and compared it with the method developed previously. The EnKF performs on average better and is more stable than the former method. Less than 300 ensemble members are sufficient to reconstruct an evolution. We use covariance adaptive inflation and localization to correct for sampling errors. We show that the EnKF results are robust over a wide range of covariance localization parameters. The reconstruction is associated with an estimation of the error, and provides valuable information on where the reconstruction is to be trusted or not.

  14. River history and tectonics.

    Science.gov (United States)

    Vita-Finzi, C

    2012-05-13

    The analysis of crustal deformation by tectonic processes has gained much from the clues offered by drainage geometry and river behaviour, while the interpretation of channel patterns and sequences benefits from information on Earth movements before or during their development. The interplay between the two strands operates at many scales: themes which have already benefited from it include the possible role of mantle plumes in the breakup of Gondwana, the Cenozoic development of drainage systems in Africa and Australia, Himalayan uplift in response to erosion, alternating episodes of uplift and subsidence in the Mississippi delta, buckling of the Indian lithospheric plate, and changes in stream pattern and sinuosity along individual alluvial channels subject to localized deformation. Developments in remote sensing, isotopic dating and numerical modelling are starting to yield quantitative analyses of such effects, to the benefit of geodymamics as well as fluvial hydrology. This journal is © 2012 The Royal Society

  15. The effect orientation of features in reconstructed atom probe data on the resolution and measured composition of T1 plates in an A2198 aluminium alloy.

    Science.gov (United States)

    Mullin, Maria A; Araullo-Peters, Vicente J; Gault, Baptiste; Cairney, Julie M

    2015-12-01

    Artefacts in atom probe tomography can impact the compositional analysis of microstructure in atom probe studies. To determine the integrity of information obtained, it is essential to understand how the positioning of features influences compositional analysis. By investigating the influence of feature orientation within atom probe data on measured composition in microstructural features within an AA2198 Al alloy, this study shows differences in the composition of T1 (Al2CuLi) plates that indicates imperfections in atom probe reconstructions. The data fits a model of an exponentially-modified Gaussian that scales with the difference in evaporation field between solutes and matrix. This information provides a guide for obtaining the most accurate information possible. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Quaternary tectonics of recent basins in northwestern Armenia

    Science.gov (United States)

    Trifonov, V. G.; Shalaeva, E. A.; Saakyan, L. Kh.; Bachmanov, D. M.; Lebedev, V. A.; Trikhunkov, Ya. I.; Simakova, A. N.; Avagyan, A. V.; Tesakov, A. S.; Frolov, P. D.; Lyubin, V. P.; Belyaeva, E. V.; Latyshev, A. V.; Ozherelyev, D. V.; Kolesnichenko, A. A.

    2017-09-01

    New data on the stratigraphy, faults, and formation history of lower to middle Pleistocene rocks in Late Cenozoic basins of northwestern Armenia are presented. It has been established that the low-mountain topography created by tectonic movements and volcanic activity existed in the region by the onset of the Pleistocene. The manifestations of two geodynamic structure-forming factors became clear in Pleistocene: (i) collisional interaction of plates due to near-meridional compression and (ii) deep tectogenesis and magma formation expressed in the distribution of vertical movements and volcanism. The general uplift of the territory, which was also related to deep processes, reached 350-500 m in basins and 600-800 m in mountain ranges over the last 0.5 Ma. The early Pleistocene ( 1.8 Ma) low- and medium-mountain topography has been reconstructed by subtraction of the latest deformations and uplift of the territory. Ancient human ancestry appeared at that time.

  17. Locking plate and fibular strut-graft augmentation in the reconstruction of unicameral bone cyst of proximal femur in the paediatric population.

    Science.gov (United States)

    Jamshidi, Khodamorad; Mirkazemi, Masoud; Izanloo, Azra; Mirzaei, Alireza

    2018-01-01

    Several therapeutic strategies have been used for managing unicameral bone cyst (UBC) of the proximal femur. However, there is insufficient evidence to support one treatment over another, and the optimal treatment is controversial. This study aims at describing our experience with surgical reconstruction of paediatric UBCs of the proximal femur using a proximal locking plate and fibular strut allograft. In total, 14 consecutive paediatric patients with Dormans types IB (four cases) and IIB (10 cases) UBC were assessed. Mean patient age was 8.6 ± 2.3 years, and mean follow-up period was 41.7 ± 29.8 months. Six patients (42.8%) were referred with a pathologic fracture. Clinical/radiological outcome and complication rates were evaluated at the final follow-up session. No cysts were Capanna's class III (recurrence) or IV (no response). Complete healing (Capanna's class I) was seen in ten cysts, while four other cysts healed with residual radiolucent areas (Capanna's class II). Mean healing period was 14.1 ± 5.1 (9-24 months). One patient had superficial infection, one heterotopic ossification, and one mild coxa vara, and mean Musculoskeletal Tumor Society (MSTS) score was 99.5%. According to our results, locking plate and fibular strut graft in Dormans classification types IB and IIB results in a favorable outcome in managing UBC of the proximal femur in the paediatric population.

  18. Plate Tectonics and Europa's Icy Shell

    Indian Academy of Sciences (India)

    defence of his theory with the 1915 publication of The Origin of Continents and Oceans. Wegener .... is one of the most promising places in our solar system to search .... Universe, Paperback Edition, Copernicus Books, pp.191–216, 2003.

  19. The seismicity of Ethiopia; active plate tectonics

    Science.gov (United States)

    Mohr, P.

    1981-01-01

    "But I tell you, when you look at the way the pieces of the northeastern portion of the African continent seem to fit together, separated by a narrow gulf, you could almost make a believer [in continental drift] of anybody" Astronaut Harrison Schmidt, on the view from Apollo 17.

  20. Petrology, geochemistry and tectonic settings of the mafic dikes and ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    margins of the basin, whereas, others are aligned .... areas of mantle upwelling, igneous intrusions, deep ... to and during the sedimentary accumulation, and ...... The development of continental margins in plate tectonic theory; J. Aust. Petrol.

  1. The tectonic stress field evolution of India since the Oligocene

    Digital Repository Service at National Institute of Oceanography (India)

    Müller, R.D.; Yatheesh, V.; Shuhail, M.

    reconstructed plate geometries following Seton et al. (2012). We reconstruct the plate boundary configuration and age-area distribution of ocean crust around Australia through time to obtain estimates for ridge push, slab pull and collisional forces acting... on the Indo-Australian Plate since the early Cretaceous, following the methodology outlined in Dyksterhuis et al. (2005a; 2005b). In the case of the Indo-Australian Plate the dominant plate driving forces are the ridge push, slab pull and collisional forces...

  2. Continental tectonics and continental kinetics

    International Nuclear Information System (INIS)

    Allegre, C.J.; Jaupart, C.; Paris-7 Univ., 75

    1985-01-01

    We present a model of continental growth which combines the results of geochemical studies and tectonic ideas about the evolution of continents through geological time. The process of continental growth is mainly controlled by surface phenomena. Continental material is extracted from the mantle along subduction zones at the periphery of oceans, and is destroyed in collision zones where it is remobilized and made available for subduction. We derive an equation for S, the portion of the Earth's surface occupied by continents, which reads as follows: dS/dt=a . √(1-S)-b . S. Coefficients a and b depend on the geometry of plates, on their number and on their velocities. We assume that they decrease exponentially with time with the same time-scale α. This model satisfies both geochemical and tectonic constraints, and allows the integration of several current observations in a single framework. (orig.)

  3. TERRAIN TECTONICS OF THE CENTRAL ASIAN FOLDED BELT

    Directory of Open Access Journals (Sweden)

    M. M. Buslov

    2014-01-01

    Full Text Available The terrain analysis concept envisages primarily a possibility of approximation of fragments / terrains of various geodynamic settings which belong to different plates. The terrain analysis can supplement the theory of plate tectonics in solving problems of geodynamics and tectonics of regions of the crust with complex structures. The Central Asian belt is among such complicated regions. Terrain structures occurred as a result of combined movements in the system of 'frontal' and/or oblique subduction – collision. In studies of geological objects, it is required first of all to prove their (vertical and horizontal autochthony in relations to each other and then proceed to paleogeodynamic, paleotectonic and paleogeographic reconstructions. Obviously, such a complex approach needs data to be obtained by a variety of research methods, including those applied to study geologic structures, stratigraphy, paleontology, paleogeography, lithothlogy, geochemistry, geochronology, paleomagnetism etc. Only by correlating such data collected from inter-disciplinary studies of the regions, it is possible to establish reliable characteristics of the geological settings and avoid mistakes and misinterpretations that may be associated with the 'stratigraphic' approach to solutions of both regional and global problems of geodynamics and tectonics of folded areas. The terrain analysis of the Central Asian folded belt suggests that its tectonic structure combines marginal continental rock complexes that were formed by the evolution of two major oceanic plates. One of them is the plate of the Paleo-Asian Ocean. As the analogue of the current Indo-Atlantic segment of Earth, it is characterised by the presence of continental blocks in the composition of the oceanic crust and the formation of oceanic basins resulting from the breakup of Rodinia and Gondvana. In the course of its evolution, super-continents disintegrated, and the blocks were reunited into the Kazakhstan

  4. The alternative concept of global tectonics

    Science.gov (United States)

    Anokhin, Vladimir; Kholmyansky, Mikhael

    2016-04-01

    The existing plate tectonic paradigm becomes more questionable in relation to the new facts of the Earth. The most complete to date criticism of plate tectonics provisions contained in the article (Pratt, 2000). Authors can recall a few facts that contradict the idea of long-range movement of plates: - The absence of convection cells in the mantle, detected by seismic tomography; - The presence of long-lived deep regmatic network in the crust, not distorted by the movement of plates; - The inability of linking the global geometry of the of mutual long-distance movement of plates. All this gives reason to believe that correct, or at least a satisfactory concept of global tectonics are not exist now. After overcoming the usual inertia of thinking the plate paradigm in the foreseeable future will replace by different concept, more relevant as the observable facts of the Earth and the well-known physical laws. The authors suggest that currently accumulated sufficient volume of facts and theoretical ideas for the synthesis of a new general hypothesis of the structure and dynamics of the Earth. Analysis of the existing tectonic theory suggests that most of their provisions are mutually compatible. Obviously, plume tectonics perfectly compatible with any of classical models. It contradicts the only plate tectonics (movement of hot spots in principle not linked either with each other or with the general picture of the plate movements, the presence of mantle convection and mantle streams are mutually exclusive, and so on). The probable transfer of the heated material down up within the Earth may occur in various forms, the simplest of which (and, consequently, the most probable) are presented plumes. The existence in the mantle numerous large volumes of decompressed substances (detected seismic tomography), can be correlated with the bodies of plumes at different stages of uplift. Plumes who raise to the bottom of the lithosphere, to spread out to the sides and form a set

  5. Tectonic implications of Mesozoic magmatism to initiation of Cenozoic basin development within the passive South China Sea margin

    Science.gov (United States)

    Mai, Hue Anh; Chan, Yu Lu; Yeh, Meng Wan; Lee, Tung Yi

    2018-04-01

    The South China Sea (SCS) is one of the classical example of a non-volcanic passive margin situated within three tectonic plates of the Eurasian, Indo-Australian and Philippine Sea plate. The development of SCS resulted from interaction of various types of plate boundaries, and complex tectonic assemblage of micro blocks and accretionary prisms. Numerous models were proposed for the formation of SCS, yet none can fully satisfy different aspects of tectonic forces. Temporal and geographical reconstruction of Cretaceous and Cenozoic magmatism with the isochrones of major basins was conducted. Our reconstruction indicated the SE margin of Asia had gone through two crustal thinning events. The sites for rifting development are controlled by localized thermal weakening of magmatism. NW-SE extension setting during Late Cretaceous revealed by magmatism distribution and sedimentary basins allow us to allocate the retreated subduction of Pacific plate to the cause of first crustal thinning event. A magmatic gap between 75 and 65 Ma prior to the initiation of first basin rifting suggested a significant modification of geodynamic setting occurred. The Tainan basin, Pearl River Mouth basin, and Liyue basins started to develop since 65 Ma where the youngest Late Cretaceous magmatism concentrated. Sporadic bimodal volcanism between 65 and 40 Ma indicates further continental extension prior to the opening of SCS. The E-W extension of Malay basin and West Natuna began since late Eocene followed by N-S rifting of SCS as Neotethys subducted. The SCS ridge developed between Pearl River Mouth basin and Liyue basin where 40 Ma volcanic activities concentrated. The interaction of two continental stretching events by Pacific followed by Neotethys subduction with localized magmatic thermal weakening is the cause for the non-volcanic nature of SCS.

  6. Andean tectonics: Implications for Satellite Geodesy

    Science.gov (United States)

    Allenby, R. J.

    1984-01-01

    Current knowledge and theories of large scale Andean tectonics as they relate to site planning for the NASA Crustal Dynamics Program's proposed high precision geodetic measurements of relative motions between the Nazca and South American plates are summarized. The Nazca Plate and its eastern margin, the Peru-Chile Trench, is considered a prototype plate marked by rapid motion, strong seismicity and well defined boundaries. Tectonic activity across the Andes results from the Nazca Plate subducting under the South American plate in a series of discrete platelets with different widths and dip angles. This in turn, is reflected in the tectonic complexity of the Andes which are a multitutde of orogenic belts superimposed on each other since the Precambrian. Sites for Crustal Dynamics Program measurements are being located to investigate both interplate and extraplate motions. Observing operations have already been initiated at Arequipa, Peru and Easter Island, Santiago and Cerro Tololo, Chile. Sites under consideration include Iquique, Chile; Oruro and Santa Cruz, Bolivia; Cuzco, Lima, Huancayo and Bayovar, Peru; and Quito and the Galapagos Islands, Ecuador. Based on scientific considerations, Santa Cruz, Huancayo (or Lima), Quito and the Galapagos Islands should be replaced by Isla San Felix, Chile; Brazilia or Petrolina, Brazil; and Guayaquil, Ecuador. If resources permit, additional important sites would be Buenaventura and Villavicencio or Puerto La Concordia, Colombia; and Mendoza and Cordoba, Argentina.

  7. Survey explores active tectonics in northeastern Caribbean

    Science.gov (United States)

    Carbó, A.; Córdoba, D.; Muñoz-Martín, A.; Granja, J.L.; Martín-Dávila, J.; Pazos, A.; Catalán, M.; Gómez, M.; ten Brink, Uri S.; von Hillebrandt, Christa; Payero, J.

    2005-01-01

    There is renewed interest in studying the active and complex northeastern Caribbean plate boundary to better understand subduction zone processes and for earthquake and tsunami hazard assessments [e.g., ten Brink and Lin, 2004; ten Brink et al., 2004; Grindlay et al., 2005]. To study the active tectonics of this plate boundary, the GEOPRICO-DO (Geological, Puerto Rico-Dominican) marine geophysical cruise, carried out between 28 March and 17 April 2005 (Figure 1), studied the active tectonics of this plate boundary.Initial findings from the cruise have revealed a large underwater landslide, and active faults on the seafloor (Figures 2a and 2c). These findings indicate that the islands within this region face a high risk from tsunami hazards, and that local governments should be alerted in order to develop and coordinate possible mitigation strategies.

  8. Habitability from Tidally Induced Tectonics

    Science.gov (United States)

    Valencia, Diana; Tan, Vivian Yun Yan; Zajac, Zachary

    2018-04-01

    The stability of Earth’s climate on geological timescales is enabled by the carbon–silicate cycle that acts as a negative feedback mechanism stabilizing surface temperatures via the intake and outgassing of atmospheric carbon. On Earth, this thermostat is enabled by plate tectonics that sequesters outgassed CO2 back into the mantle via weathering and subduction at convergent margins. Here we propose a separate tectonic mechanism—vertical recycling—that can serve as the vehicle for CO2 outgassing and sequestration over long timescales. The mechanism requires continuous tidal heating, which makes it particularly relevant to planets in the habitable zone of M stars. Dynamical models of this vertical recycling scenario and stability analysis show that temperate climates stable over timescales of billions of years are realized for a variety of initial conditions, even as the M star dims over time. The magnitude of equilibrium surface temperatures depends on the interplay of sea weathering and outgassing, which in turn depends on planetary carbon content, so that planets with lower carbon budgets are favored for temperate conditions. The habitability of planets such as found in the Trappist-1 system may be rooted in tidally driven tectonics.

  9. Introduction to Plate Boundaries and Natural Hazards

    NARCIS (Netherlands)

    Duarte, João C.; Schellart, Wouter P.

    2016-01-01

    A great variety of natural hazards occur on Earth, including earthquakes, volcanic eruptions, tsunamis, landslides, floods, fires, tornadoes, hurricanes, and avalanches. The most destructive of these hazards, earthquakes, tsunamis, and volcanic eruptions, are mostly associated with tectonic plate

  10. The tectonics of Mercury

    International Nuclear Information System (INIS)

    Melosh, H.J.; Mckinnon, W.B.

    1988-01-01

    The probable tectonic history of Mercury and the relative sequence of events are discussed on the basis of data collected by the Mariner-10 spacecraft. Results indicate that Mercury's tectonic activity was confined to its early history; its endogenic activity was principally due to a small change in the shape of its lithosphere, caused by tidal despinning, and a small change in area caused by shrinkage due to cooling. Exogenic processes, in particular the impact activity, have produced more abundant tectonic features. Many features associated with the Caloris basin are due to loading of Mercury's thick lithosphere by extrusive lavas or subsidence due to magma withdrawal. It is emphasized that tectonic features observed on Mercury yield insight into the earliest tectonic events on planets like Mars and, perhaps, the earth, where subsequent events obscured or erased the most ancient tectonic records

  11. The Tectonic Practice

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due

    has the consequence that it is difficult to create architecture where the technical concerns are an inherent part of the architectural expression. The aim of the thesis is to discuss the role of digital tools in overcoming the distance between the professional specializations and thereby support...... a tectonic practice. The project develops a framework to understand the role of digital tools in the tectonic practice from and discusses how and in which areas the tectonic practice could become supported by digital tools....

  12. Geomorphology, tectonics, and exploration

    Science.gov (United States)

    Sabins, F. F., Jr.

    1985-01-01

    Explorationists interpret satellite images for tectonic features and patterns that may be clues to mineral and energy deposits. The tectonic features of interest range in scale from regional (sedimentary basins, fold belts) to local (faults, fractures) and are generally expressed as geomorphic features in remote sensing images. Explorationists typically employ classic concepts of geomorphology and landform analysis for their interpretations, which leads to the question - Are there new and evolving concepts in geomorphology that may be applicable to tectonic analyses of images?

  13. Active Deformation in the Overriding Plate Associated with Temporal Changes of the Philippine Sea Plate Motion

    Science.gov (United States)

    Ishiyama, T.; Sato, H.; Van Horne, A.

    2015-12-01

    We present detailed geologic evidence linking changes over time in Philippine Sea plate (PHS) motion and intracontinental deformation in central and southwest (SW) Japan during the Pliocene and after. In the early Pliocene, subduction of the PHS plate under SW Japan restarted in a northerly direction after period of deceleration or cessation. Later, motion changed to a more westerly direction. Corresponding geological changes found in the overriding plate include unconformities in the forearc basins, changes in slip sense on faults, depocenter migration, re-organization of drainage systems and volcanism. Quaternary intraplate deformation is prominent north of the Median Tectonic Line (MTL) inactive segment, above a shallow flat slab. In contrast, less Quaternary tectonic activity is found north of the MTL active segment which lies over a steadily-slipping portion of the subducting slab that behaves as a less-deformed rigid block. Depocenters and active thrusting have migrated north/northwestward over the past 5 My above the shallow flat slab segment of the PHS. We reconstructed the Plio-Pleistocene migration history using Neogene stratigraphy and shallow seismic reflection profiles. We see shallow PHS slab contact with the lower continental crust in our deep seismic reflection profiles, which may explain its enhanced downward drag of the overriding plate and synchronous strong compression in the crust. We find evidence of more westerly PHS plate subduction since the middle Pleistocene in (1) unconformities in the Kumano forearc basin deposits in SW Japan, (2) drastic stream captures in Shikoku, and (3) concordant changes in fault slip sense from thrust to dextral slip along the MTL. Oblique subduction could have induced stronger horizontal stress in the overriding plate above the shallow flat slab which could account for the increasing geologic slip rate observed on active structures. During four repetitions of megathrust earthquake sequences since the 17th century

  14. Tectonic and metallogenic model for northeast Asia

    Science.gov (United States)

    Parfenov, Leonid M.; Nokleberg, Warren J.; Berzin, Nikolai A.; Badarch, Gombosuren; Dril, Sergy I.; Gerel, Ochir; Goryachev, Nikolai A.; Khanchuk, Alexander I.; Kuz'min, Mikhail I.; Prokopiev, Andrei V.; Ratkin, Vladimir V.; Rodionov, Sergey M.; Scotese, Christopher R.; Shpikerman, Vladimir I.; Timofeev, Vladimir F.; Tomurtogoo, Onongin; Yan, Hongquan; Nokleberg, Warren J.

    2011-01-01

    scientific goals and benefits of the projects are to: (1) provide a comprehensive international data base on the mineral resources of the region that is the first extensive knowledge available in English; (2) provide major new interpretations of the origin and crustal evolution of mineralizing systems and their host rocks, thereby enabling enhanced, broad-scale tectonic reconstructions and interpretations; and (3) promote trade and scientific and technical exchanges between North America and eastern Asia.

  15. Towards a Tectonic Approach

    DEFF Research Database (Denmark)

    Hvejsel, Marie Frier; Kirkegaard, Poul Henning; Mortensen, Sophie Bondgaard

    2015-01-01

    through this transformation is inevitably a tectonic question. By analyzing three historical examples, Adolf Loos’ Villa Moller, Le Corbusier’s Unité d’Habitation, and Frank Lloyd Wright’s Johnson Wax Administration Building, chosen for their tectonic ability to exploit the technical ‘principle’ defining...

  16. Digital Tectonic Tools

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due

    2005-01-01

    Tectonics has been an inherent part of the architectural field since the Greek temples while the digital media is new to the field. This paper is built on the assumption that in the intermediate zone between the two there is a lot to be learned about architecture in general and the digital media...... in particular. A model of the aspects in the term tectonics – epresentation, ontology and culture – will be presented and used to discuss the current digital tools’ ability in tectonics. Furthermore it will be discussed what a digital tectonic tool is and could be and how a connection between the digital...... and tectonic could become a part of the architectural education....

  17. Active tectonics and earthquake potential of the Myanmar region

    OpenAIRE

    Wang, Yu; Sieh, Kerry; Tun, Soe Thura; Lai, Kuang-Yin; Myint, Than

    2014-01-01

    This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subd...

  18. WAVE TECTONICS OF THE EARTH

    Directory of Open Access Journals (Sweden)

    Tatiana Yu. Tveretinova

    2010-01-01

    Full Text Available In the Earth's lithosphere, wavy alternation of positive and negative heterochronous structures is revealed; such structures are variable in ranks and separated by vergence zones of fractures and folds. In the vertical profile of the lithosphere, alternating are layers characterized by relatively plastic or fragile rheological properties and distinguished by different states of stress. During the Earth’s evolution, epochs of compression and extension are cyclically repeated, including planetary-scale phenomena which are manifested by fluctuating changes of the planet’s volume. Migration of geological and geophysical (geodynamic processes takes place at the Earth's surface and in its interior. The concept of the wave structure and evolution of the Earth's lithosphere provides explanations to the abovementioned regularities. Wavy nature of tectonic structures of the lithosphere, the cyclic recurrence of migration and geological processes in space and time can be described in terms of the multiple-order wave geodynamics of the Earth's lithosphere that refers to periodical variations of the state of stress. Effects of structure-forming tectonic forces are determined by «interference» of tangential and radial stresses of the Earth. The tangential stresses, which occur primarily due to the rotational regime of the planet, cause transformations of the Earth’s shape, redistributions of its substance in depths, the westward drift of the rock mass in its upper levels, and changes of structural deformation plans. The radial stresses, which are largely impacted by gravity, determine the gravitational differentiation of the substance, vertical flattening and sub-horizontal flow of the rock masses, and associated fold-rupture deformation. Under the uniform momentum geodynamic concept proposed by [Vikulin, Tveritinova, 2004, 2005, 2007, 2008], it is possible to provide consistent descriptions of seismic and volcanic, tectonic and geological processes

  19. Extending Whole-earth Tectonics To The Terrestrial Planets

    Science.gov (United States)

    Baker, V. R.; Maruyama, S.; Dohm, J. M.

    Based on the need to explain a great many geological and geophysical anomalies on Mars, and stimulated by the new results from the Mars Global Surveyor Mission, we propose a conceptual model of whole-EARTH (Episodic Annular Revolving Thermal Hydrologic) tectonics for the long-term evolution of terrestrial planets. The theory emphasizes (1) the importance of water in planetary evolution, and (2) the physi- cal transitions in modes of mantle convection in relation to planetary heat produc- tion. Depending on their first-order geophysical parameters and following accretion and differentiation from volatile-rich planetessimals, terrestrial planets should evolve through various stages of mantle convection, including magma ocean, plate tectonic, and stagnant lid processes. If a water ocean is able to condense from the planet's early steam atmosphere, an early regime of plate tectonics will follow the initial magma ocean. This definitely happened on earth, probably on Mars, and possibly on Venus. The Mars history led to transfer of large amounts of water to the mantle during the pe- riod of heavy bombardment. Termination of plate tectonics on Mars during the heavy bombardment period led to initiation of superplumes at Tharsis and Elysium, where long-persistent volcanism and water outbursts dominated much of later Martian his- tory. For Venus, warming of the early sun made the surface ocean unstable, eliminating its early plate-tectonic regime. Although Venus now experiences stagnant-lid convec- tion with episodic mantle overturns, the water subducted to its lower mantle during the ancient plate-tectonic regime manifests itself in the initation of volatile-rich plumes that dominate its current tectonic regime.

  20. Scaling and spatial complementarity of tectonic earthquake swarms

    KAUST Repository

    Passarelli, Luigi

    2017-11-10

    Tectonic earthquake swarms (TES) often coincide with aseismic slip and sometimes precede damaging earthquakes. In spite of recent progress in understanding the significance and properties of TES at plate boundaries, their mechanics and scaling are still largely uncertain. Here we evaluate several TES that occurred during the past 20 years on a transform plate boundary in North Iceland. We show that the swarms complement each other spatially with later swarms discouraged from fault segments activated by earlier swarms, which suggests efficient strain release and aseismic slip. The fault area illuminated by earthquakes during swarms may be more representative of the total moment release than the cumulative moment of the swarm earthquakes. We use these findings and other published results from a variety of tectonic settings to discuss general scaling properties for TES. The results indicate that the importance of TES in releasing tectonic strain at plate boundaries may have been underestimated.

  1. Remembering myth and ritual in the everyday tectonics of hospitals

    DEFF Research Database (Denmark)

    Tvedebrink, Tenna Doktor Olsen

    2015-01-01

    When discussing tectonics, the book Studies in tectonic culture by Kenneth Frampton (2001) is often mentioned for linking the ethics of architecture with a focus on structural genius. Another reference is the paper The tell-the-tale detail by Marco Frascari (1984), which in addition to Frampton put...... emphasis on both the physical construction and mental construing of architecture. With this dual perspective Frascari established a discourse in tectonic thinking which brings the tectonic expression beyond structural genius into socio-cultural realms of storytelling, myth and ritual. However, in everyday...... architecture like hospitals this perspective of construing is often neglected. In this paper, I explore if it is possible through a re-reading of Frascari’s words to inspire for a re-construction of everyday tectonics? Based on project MORE at Aalborg Hospital, I argue that the perspective of construing...

  2. News and Views: Keep it down! AU becomes au, and is defined in metres; Kepler survey announces two planets in a binary star system; Is there plate tectonics on Mars? Vaporizing Earth - for research!

    Science.gov (United States)

    2012-10-01

    Division 1 of the IAU recommended that the astronomical unit - originally the length of the semi-major axis of the Earth's orbit - be redefined as a fixed number of kilometres. A team of observers using data from NASA's Kepler space observatory announced at the IAU General Assembly that they had discovered two planets orbiting a pair of binary stars, and that such planets could exist in the habitable zone of their system. The Red Planet has long been considered something of a dead planet as far as tectonic movements of its crust, but careful analysis of thermal and topographic images of the surface suggest the existence of major faults with horizontal slip along the Valles Marineris. The question of what would happen if Earth were to approach the Sun and start vaporizing has been modelled in order to help to model the composition of super-Earths.

  3. Lesser Himalayan sequences in Eastern Himalaya and their deformation: Implications for Paleoproterozoic tectonic activity along the northern margin of India

    Directory of Open Access Journals (Sweden)

    Dilip Saha

    2013-05-01

    Full Text Available Substantial part of the northern margin of Indian plate is subducted beneath the Eurasian plate during the Caenozoic Himalayan orogeny, obscuring older tectonic events in the Lesser Himalaya known to host Proterozoic sedimentary successions and granitic bodies. Tectonostratigraphic units of the Proterozoic Lesser Himalayan sequence (LHS of Eastern Himalaya, namely the Daling Group in Sikkim and the Bomdila Group in Arunachal Pradesh, provide clues to the nature and extent of Proterozoic passive margin sedimentation, their involvement in pre-Himalayan orogeny and implications for supercontinent reconstruction. The Daling Group, consisting of flaggy quartzite, meta-greywacke and metapelite with minor mafic dyke and sill, and the overlying Buxa Formation with stromatolitic carbonate-quartzite-slate, represent shallow marine, passive margin platformal association. Similar lithostratigraphy and broad depositional framework, and available geochronological data from intrusive granites in Eastern Himalaya indicate strikewise continuity of a shallow marine Paleoproterozoic platformal sequence up to Arunachal Pradesh through Bhutan. Multiple fold sets and tectonic foliations in LHS formed during partial or complete closure of the sea/ocean along the northern margin of Paleoproterozoic India. Such deformation fabrics are absent in the upper Palaeozoic–Mesozoic Gondwana formations in the Lesser Himalaya of Darjeeling-Sikkim indicating influence of older orogeny. Kinematic analysis based on microstructure, and garnet composition suggest Paleoproterozoic deformation and metamorphism of LHS to be distinct from those associated with the foreland propagating thrust systems of the Caenozoic Himalayan collisional belt. Two possibilities are argued here: (1 the low greenschist facies domain in the LHS enveloped the amphibolite to granulite facies domains, which were later tectonically severed; (2 the older deformation and metamorphism relate to a Pacific type

  4. Deformation of the Northwestern Okhotsk Plate: How is it happening?

    OpenAIRE

    Hindle, D.; Fujita, K.; Mackey, K.

    2009-01-01

    The Eurasia (EU) – North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on ...

  5. GEOMAGNETIC CONJUGACY OF MODERN TECTONIC STRUCTURES

    Directory of Open Access Journals (Sweden)

    G. Ya. Khachikyan

    2013-01-01

    Full Text Available An earthquake is an element of the global electric circuit (GEC –  this new idea suggested in the space age is tested in our study. In the frame of the GEC concept, one may expect that tectonic structures of the northern and southern hemispheres may be magnetically conjugated. It is found that the midocean ridges of the southern hemisphere, located along the boundary of the Antarctic lithosphere plate, are magnetically conjugated with the areas of the junction of continental orogens and platforms in the northern hemisphere. The closest geomagnetic conjugacy exists between the southern boundary of Nazca lithospheric plate and the northern boundaries of Cocos and Caribbean lithospheric plates.

  6. Pre-Cenozoic basement rocks of the Proto-Philippine Sea Plate: Constraints for the birthplace of the Izu-Bonin-Mariana Arc

    Science.gov (United States)

    Tani, K.; Ishizuka, O.; Horie, K.; Barth, A. P.; Harigane, Y.; Ueda, H.

    2016-12-01

    The Izu-Bonin-Mariana Arc is widely regarded to be a typical intra-oceanic arc, with the oceanic Pacific Plate subducting beneath the Philippine Sea Plate, an evolving complex of active and inactive arcs and back-arc basins. However, little is known about the origin of the proto-Philippine Sea Plate, which existed along with the Pacific Plate at the time of subduction initiation in the Eocene. To investigate the crustal structures of the proto-Philippine Sea Plate, we conducted manned-submersible and dredge surveys in the Daito Ridges and the Kyushu-Palau Ridge. The Daito Ridges comprise the northwestern Philippine Sea Plate along with what are regarded as remnants of the proto-Philippine Sea Plate. Submersible observations and rock sampling revealed that the Daito Ridges expose deep crustal sections of gabbroic, granitic, metamorphic, and ultra-mafic rocks, along with volcanic rocks ranging from basalt to andesite. Mesozoic magmatic zircon U-Pb ages have been obtained from the plutonic rocks, and whole-rock geochemistry of the igneous rocks indicates arc origins. Furthermore, mafic schist collected from the Daito Ridge has experienced amphibolite facies metamorphism, with phase assemblages suggesting that the crust was thicker than 20 km at the time. Similar amphibolite-facies metamorphic rocks with Proterozoic zircons have been recovered in the southern Kyushu-Palau Ridge, indicating that such distinctively older basement rocks exist as isolated tectonic blocks within the present Philippine Sea Plate. These finds show that the parts of the Daito Ridges and Kyushu-Palau Ridge represent developed crustal sections of the Pre-Cenozoic arc that comprises part of the proto-Philippine Sea Plate, and, together with the tectonic reconstruction of the proto-Philippine Sea Plate (Deschamps and Lallemand 2002, JGR), they suggest that subduction of the Izu-Bonin-Mariana Arc initiated at the continental margin of the Southeast Asia.

  7. Tectonic design strategies

    DEFF Research Database (Denmark)

    Beim, Anne

    2000-01-01

    as the poetics of construction, thus it may be considered as an essential activity in the development of the architectural design process.  Similar to the complex nature of the tectonic, the design process is an ongoing movement of interpretation, mediation, and decision making where the skills of the architect...

  8. Tectonic vision in architecture

    DEFF Research Database (Denmark)

    Beim, Anne

    1999-01-01

    By introducing the concept; Tectonic Visions, The Dissertation discusses the interrelationship between the basic idea, the form principles, the choice of building technology and constructive structures within a given building. Includes Mies van der Rohe, Le Corbusier, Eames, Jorn Utzon, Louis Kahn...

  9. Cretacic tectonics in Uruguay

    International Nuclear Information System (INIS)

    Gomez Rifas, C.

    2012-01-01

    This work is about Cretacic tectonics in Uruguay, this formation is characterized by high level cortex because the basament is cratonized since Middle Devonian. There were formed two main grabens such as Santa Lucia and Mirim-Pelotas which are filled with basalt and sediments.

  10. The breakup of East Gondwana: Assimilating constraints from Cretaceous ocean basins around India into a best-fit tectonic model

    Science.gov (United States)

    Gibbons, Ana D.; Whittaker, Joanne M.; Müller, R. Dietmar

    2013-03-01

    models for the Cretaceous seafloor-spreading history of East Gondwana result in unlikely tectonic scenarios for at least one of the plate boundaries involved and/or violate particular constraints from at least one of the associated ocean basins. We link East Gondwana spreading corridors by integrating magnetic and gravity anomaly data from the Enderby Basin off East Antarctica within a regional plate kinematic framework to identify a conjugate series of east-west-trending magnetic anomalies, M4 to M0 ( 126.7-120.4 Ma). The mid-ocean ridge that separated Greater India from Australia-Antarctica propagated from north to south, starting at 136 Ma northwest of Australia, and reached the southern tip of India at 126 Ma. Seafloor spreading in the Enderby Basin was abandoned at 115 Ma, when a ridge jump transferred the Elan Bank and South Kerguelen Plateau to the Antarctic plate. Our revised plate kinematic model helps resolve the problem of successive two-way strike-slip motion between Madagascar and India seen in many previously published reconstructions and also suggests that seafloor spreading between them progressed from south to north from 94 to 84 Ma. This timing is essential for tectonic flow lines to match the curved fracture zones of the Wharton and Enderby basins, as Greater India gradually began to unzip from Madagascar from 100 Ma. In our model, the 85-East Ridge and Kerguelen Fracture Zone formed as conjugate flanks of a "leaky" transform fault following the 100 Ma spreading reorganization. Our model also identifies the Afanasy Nikitin Seamounts as products of the Conrad Rise hotspot.

  11. Tectonic feedback and the earthquake cycle

    Science.gov (United States)

    Lomnitz, Cinna

    1985-09-01

    The occurrence of cyclical instabilities along plate boundaries at regular intervals suggests that the process of earthquake causation differs in some respects from the model of elastic rebound in its simplest forms. The model of tectonic feedback modifies the concept of this original model in that it provides a physical interaction between the loading rate and the state of strain on the fault. Two examples are developed: (a) Central Chile, and (b) Mexico. The predictions of earthquake hazards for both types of models are compared.

  12. Extrusive and Intrusive Magmatism Greatly Influence the Tectonic Mode of Earth-Like Planets

    Science.gov (United States)

    Lourenco, D.; Tackley, P. J.; Rozel, A.; Ballmer, M.

    2017-09-01

    Plate tectonics on Earth-like planets is typically modelling using a strongly temperature-dependent visco-plastic rheology. Previous analyses have generally focussed on purely thermal convection. However, we have shown that the influence of compositional heterogeneity in the form of continental or oceanic crust can greatly influence plate tectonics by making it easier (i.e. it occurs at a lower yield stress or friction coefficient). Here we present detailed results on this topic, in particular focussing on the influence of intrusive vs. extrusive magmatism on the tectonic mode.

  13. Deciphering Detailed Plate Kinematics of the Indian Ocean: A Combined Indian-Australian-French Initiative

    Science.gov (United States)

    Vadakkeyakath, Y.; Müller, R.; Dyment, J.; Bhattacharya, G.; Lister, G. S.; Kattoju, K. R.; Whittaker, J.; Shuhail, M.; Gibbons, A.; Jacob, J.; White, L. T.; Bissessur, P. D.; Kiranmai, S.

    2012-12-01

    -Australian and the Antarctic-Australian plate boundaries. These new studies also revealed the existence of several complexities, which need to be resolved in order to decipher plate kinematics of the Indian Ocean as a whole. Any improved model of plate kinematics of the Indian Ocean region should be compatible with the motions that are evident at all the above-mentioned plate boundaries and also is able to explain the identified complexities. With an aim to develop such a unified model for the plate tectonic evolution of the Indian Ocean in high resolution, a project was initiated for the synthesis of available data and results with the above groups of Indian, Australian and French scientists. The planned work under the auspices of this project will allow examining different reconstruction models to iteratively arrive at a model that is compatible with motions across different plate circuits and also accommodates various microcontinents and continental fragments and other hitherto identified complexities.

  14. Comparison of reconstruction plate screw fixation and percutaneous cannulated screw fixation in treatment of Tile B1 type pubic symphysis diastasis: a finite element analysis and 10-year clinical experience.

    Science.gov (United States)

    Yu, Ke-He; Hong, Jian-Jun; Guo, Xiao-Shan; Zhou, Dong-Sheng

    2015-09-22

    The objective of this study is to compare the biomechanical properties and clinical outcomes of Tile B1 type pubic symphysis diastasis (PSD) treated by percutaneous cannulated screw fixation (PCSF) and reconstruction plate screw fixation (RPSF). Finite element analysis (FEA) was used to compare the biomechanical properties between PCSF and RPSF. CT scan data of one PSD patient were used for three-dimensional reconstructions. After a validated pelvic finite element model was established, both PCSF and RPSF were simulated, and a vertical downward load of 600 N was loaded. The distance of pubic symphysis and stress were tested. Then, 51 Tile type B1 PSD patients (24 in the PCSF group; 27 in the RPSF group) were reviewed. Intra-operative blood loss, operative time, and the length of the skin scar were recorded. The distance of pubic symphysis was measured, and complications of infection, implant failure, and revision surgery were recorded. The Majeed scoring system was also evaluated. The maximum displacement of the pubic symphysis was 0.408 and 0.643 mm in the RPSF and PCSF models, respectively. The maximum stress of the plate in RPSF was 1846 MPa and that of the cannulated screw in PCSF was 30.92 MPa. All 51 patients received follow-up at least 18 months post-surgery (range 18-54 months). Intra-operative blood loss, operative time, and the length of the skin scar in the PCSF group were significantly different than those in the RPSF group. No significant differences were found in wound infection, implant failure, rate of revision surgery, distance of pubic symphysis, and Majeed score. PCSF can provide comparable biomechanical properties to RPSF in the treatment of Tile B1 type PSD. Meanwhile, PCSF and RPSF have similar clinical and radiographic outcomes. Furthermore, PCSF also has the advantages of being minimally invasive, has less blood loss, and has shorter operative time and skin scar.

  15. Seismicity and tectonics of Bangladesh

    International Nuclear Information System (INIS)

    Hossain, K.M.

    1989-05-01

    Northern and eastern Bangladesh and surrounding areas belong to a seismically active zone and are associated with the subduction of the Indian plate. The seismicity and tectonics have been studied in detail and the observations have been correlated to understand the earthquake phenomenon in the region. The morphotectonic behaviour of northern Bangladesh shows that it is deeply related to the movement of the Dauki fault system and relative upliftment of the Shillong plateau. Contemporary seismicity in the Dauki fault system is relatively quiet comparing to that in the Naga-Disang-Haflong thrust belt giving rise to the probability of sudden release of energy being accumulated in the vicinity of the Dauki fault system. This observation corresponds with the predicted average return period of a large earthquake (1897 type) and the possibility of M > 8 earthquake in the vicinity of the Dauki fault within this century should not be ruled out. The seismicity in the folded belt in the east follows the general trend of Arakan-Yoma anticlinorium and represents shallow and low-angled thrust movements in conformity with the field observation. Seismotectonic behaviour in the deep basin part of Bangladesh demonstrates that an intraplate movement in the basement rock has been taking place along the deep-seated faults causing relative upliftment and subsidence in the basin. Bangladesh has been divided into three seismic zones on the basis of morphotectonic and seismic behaviour. Zone-I has been identified as the zone of high seismic risk. (author). 43 refs, 5 figs, 3 tabs

  16. High complication rate in reconstruction of Paprosky type IIIa acetabular defects using an oblong implant with modular side plates and a hook.

    Science.gov (United States)

    Babis, G C; Sakellariou, V I; Chatziantoniou, A N; Soucacos, P N; Megas, P

    2011-12-01

    We report the results of 62 hips in 62 patients (17 males, 45 females) with mean age of 62.4 years (37 to 81), who underwent revision of the acetabular component of a total hip replacement due to aseptic loosening between May 2003 and November 2007. All hips had a Paprosky type IIIa acetabular defect. Acetabular revision was undertaken using a Procotyl E cementless oblong implant with modular side plates and a hook combined with impaction allografting. At a mean follow-up of 60.5 months (36 to 94) with no patients lost to follow-up and one died due to unrelated illness, the complication rate was 38.7%. Complications included aseptic loosening (19 hips), deep infection (3 hips), broken hook and side plate (one hip) and a femoral nerve palsy (one hip). Further revision of the acetabular component was required in 18 hips (29.0%) and a further four hips (6.4%) are currently loose and awaiting revision. We observed unacceptably high rates of complication and failure in our group of patients and cannot recommend this implant or technique.

  17. Cold plate

    Energy Technology Data Exchange (ETDEWEB)

    Marroquin, Christopher M.; O' Connell, Kevin M.; Schultz, Mark D.; Tian, Shurong

    2018-02-13

    A cold plate, an electronic assembly including a cold plate, and a method for forming a cold plate are provided. The cold plate includes an interface plate and an opposing plate that form a plenum. The cold plate includes a plurality of active areas arranged for alignment over respective heat generating portions of an electronic assembly, and non-active areas between the active areas. A cooling fluid flows through the plenum. The plenum, at the non-active areas, has a reduced width and/or reduced height relative to the plenum at the active areas. The reduced width and/or height of the plenum, and exterior dimensions of cold plate, at the non-active areas allow the non-active areas to flex to accommodate surface variations of the electronics assembly. The reduced width and/or height non-active areas can be specifically shaped to fit between physical features of the electronics assembly.

  18. Plating laboratory

    International Nuclear Information System (INIS)

    Seamster, A.G.; Weitkamp, W.G.

    1984-01-01

    The lead plating of the prototype resonator has been conducted entirely in the plating laboratory at SUNY Stony Brook. Because of the considerable cost and inconvenience in transporting personnel and materials to and from Stony Brook, it is clearly impractical to plate all the resonators there. Furthermore, the high-beta resonator cannot be accommodated at Stony Brook without modifying the set up there. Consequently the authors are constructing a plating lab in-house

  19. Stagnant lid tectonics: Perspectives from silicate planets, dwarf planets, large moons, and large asteroids

    Directory of Open Access Journals (Sweden)

    Robert J. Stern

    2018-01-01

    Full Text Available To better understand Earth's present tectonic style–plate tectonics–and how it may have evolved from single plate (stagnant lid tectonics, it is instructive to consider how common it is among similar bodies in the Solar System. Plate tectonics is a style of convection for an active planetoid where lid fragment (plate motions reflect sinking of dense lithosphere in subduction zones, causing upwelling of asthenosphere at divergent plate boundaries and accompanied by focused upwellings, or mantle plumes; any other tectonic style is usefully called “stagnant lid” or “fragmented lid”. In 2015 humanity completed a 50+ year effort to survey the 30 largest planets, asteroids, satellites, and inner Kuiper Belt objects, which we informally call “planetoids” and use especially images of these bodies to infer their tectonic activity. The four largest planetoids are enveloped in gas and ice (Jupiter, Saturn, Uranus, and Neptune and are not considered. The other 26 planetoids range in mass over 5 orders of magnitude and in diameter over 2 orders of magnitude, from massive Earth down to tiny Proteus; these bodies also range widely in density, from 1000 to 5500 kg/m3. A gap separates 8 silicate planetoids with ρ = 3000 kg/m3 or greater from 20 icy planetoids (including the gaseous and icy giant planets with ρ = 2200 kg/m3 or less. We define the “Tectonic Activity Index” (TAI, scoring each body from 0 to 3 based on evidence for recent volcanism, deformation, and resurfacing (inferred from impact crater density. Nine planetoids with TAI = 2 or greater are interpreted to be tectonically and convectively active whereas 17 with TAI <2 are inferred to be tectonically dead. We further infer that active planetoids have lithospheres or icy shells overlying asthenosphere or water/weak ice. TAI of silicate (rocky planetoids positively correlates with their inferred Rayleigh number. We conclude that some type of stagnant lid tectonics is

  20. Tectonic Vocabulary & Materialization

    DEFF Research Database (Denmark)

    Hvejsel, Marie Frier; Beim, Anne; Bundgaard, Charlotte

    2015-01-01

    . On the occasion of the Second International Conference on Structures & Architecture held in July 2013 in Portugal the authors organized a special session entitled From open structures to the cladding of control bringing together researchers from the Nordic countries to discuss this issue. Likewise the initiative......By referring to the fundamental question of how we unite aesthetics and technology – tectonic theory is necessarily a focal point in the development of the architectural discipline. However, a critical reconsideration of the role of tectonic theory seems necessary when facing the present everyday...... conditions of the built environment. We see an increasing number of square meters in ordinary housing, in commercial buildings and in public buildings such as hospitals and schools that are dealt with as performative structural frameworks rather than qualitative spaces for habitation and contemplation...

  1. A palaeomagnetic perspective of Precambrian tectonic styles

    Science.gov (United States)

    Schmidt, P. W.; Embleton, B. J. J.

    1986-01-01

    The considerable success derived from palaeomagnetic studies of Phanerozoic rocks with respect to the tectonic styles of continental drift and plate tectonics, etc., have not been repeated by the many palaeomagnetic studies of Precambrian rocks. There are 30 years of research with results covering the major continents for Precambrian times that overlap considerably yet there is no concensus. There is good evidence that the usual assumptions employed by palaeomagnetism are valid for the Precambrian. The exisence of magnetic reversals during the Precambrian, for instance, is difficult to explain except in terms of a geomagnetic field that was predominantly dipolar in nature. It is a small concession to extend this notion of the Precambrian geomagnetic field to include its alignment with the Earth's spin axis and the other virtues of an axial geocentric dipole that characterize the recent geomagnetic field. In terms of greenstone terranes it is obvious that tectonic models postulated to explain these observations are paramount in understanding Precambrian geology. What relevance the current geographical relationships of continents have with their Precambrian relationships remains a paradox, but it would seem that the ensialic model for the development of greenstone terranes is favored by the Precambrian palaeomagnetic data.

  2. Treatment of unstable sacral fractures with percutaneous reconstruction plate internal fixation Tratamento de fraturas sacrais instáveis com reconstrução percutânea com fixação de placa interna

    Directory of Open Access Journals (Sweden)

    Hong-Wei Chen

    2012-05-01

    Full Text Available PURPOSE: To study the effects of percutaneous reconstruction plate internal fixation in the treatment of unstable sacral fractures. METHODS: Percutaneous reconstruction plate internal fixation was applied on 21 cases of unstable sacral fracture (15 males and six females, at age range of 16-65 years, mean 38.3 years including four cases of Denis Zone I, 14 cases of Zone II and three cases of Zone III. In operation, an arc incision (about 3-5 cm long was made along the iliac crest on the outside border of posterior superior iliac spine (PSIS on both sides, and then the plate was transported from the wounded side to the opposite one through the subcutaneous tunnel. RESULTS: The mean incision length, operation time, intraoperative blood loss was 4.3cm, 45.2min, and 160.8ml respectively. All these patients were followed up for 12-33 months (average 16.3 months, which showed no incision infection, intraoperative neurovascular injury, internal fixation loose or breakage, disunion, or obvious lower limb length inequality. The function result was rated as excellent in six cases, good in 12 and fair in 3, with excellence rate of 85.7%, according to the Majeed scoring system. CONCLUSION: Percutaneous reconstruction plate internal fixation is an ideal surgical approach to unstable sacral fractures, as it is easy, safe, causing less trauma and fewer complications, and conducive to quicker recovery.OBJETIVO: Estudar os efeitos da reconstrução percutânea com fixação de placa interna no tratamento de fraturas sacrais instáveis. MÉTODOS: A reconstrução percutânea com fixação de placa interna foi aplicada em 21 casos de fratura sacral instável (15 homens e seis mulheres, com idade variando entre 16 e 65 anos, média de 38,3 anos incluindo quatro casos de Zona I de Denis, 14 casos de Zona II e três casos de Zona III. No ato operatório, uma incisão arqueada (cerca de 3 a 5cm de comprimento foi feita ao longo da crista ilíaca na borda externa da

  3. Crustal structure and active tectonics in the Eastern Alps

    DEFF Research Database (Denmark)

    Brückl, E.; Behm, M.; Decker, K.

    2010-01-01

    fragment (PA), was interpreted and a triple junction was inferred. The goal of this study has been to relate these deep crustal structures to active tectonics. We used elastic plate modeling to reconsider the Moho fragmentation. We interpret subduction of EU below AD and PA from north to south......During the last decade, a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the Eastern Alps and their adjacent tectonic provinces. A fragmentation of the lithosphere into three blocks, Europe (EU), Adria (AD), and the new Pannonian...

  4. Identifying tectonic parameters that influence tsunamigenesis

    Science.gov (United States)

    van Zelst, Iris; Brizzi, Silvia; van Dinther, Ylona; Heuret, Arnauld; Funiciello, Francesca

    2017-04-01

    The role of tectonics in tsunami generation is at present poorly understood. However, the fact that some regions produce more tsunamis than others indicates that tectonics could influence tsunamigenesis. Here, we complement a global earthquake database that contains geometrical, mechanical, and seismicity parameters of subduction zones with tsunami data. We statistically analyse the database to identify the tectonic parameters that affect tsunamigenesis. The Pearson's product-moment correlation coefficients reveal high positive correlations of 0.65 between, amongst others, the maximum water height of tsunamis and the seismic coupling in a subduction zone. However, these correlations are mainly caused by outliers. The Spearman's rank correlation coefficient results in more robust correlations of 0.60 between the number of tsunamis in a subduction zone and subduction velocity (positive correlation) and the sediment thickness at the trench (negative correlation). Interestingly, there is a positive correlation between the latter and tsunami magnitude. In an effort towards multivariate statistics, a binary decision tree analysis is conducted with one variable. However, this shows that the amount of data is too scarce. To complement this limited amount of data and to assess physical causality of the tectonic parameters with regard to tsunamigenesis, we conduct a numerical study of the most promising parameters using a geodynamic seismic cycle model. We show that an increase in sediment thickness on the subducting plate results in a shift in seismic activity from outerrise normal faults to splay faults. We also show that the splay fault is the preferred rupture path for a strongly velocity strengthening friction regime in the shallow part of the subduction zone, which increases the tsunamigenic potential. A larger updip limit of the seismogenic zone results in larger vertical surface displacement.

  5. Dynamic response to strike-slip tectonic control on the deposition and evolution of the Baranof Fan, Gulf of Alaska

    Science.gov (United States)

    Walton, Maureen A. L.; Gulick, Sean P. S.; Reece, Robert S.; Barth, Ginger A.; Christeson, Gail L.; VanAvendonk, Harm J.

    2014-01-01

    The Baranof Fan is one of three large deep-sea fans in the Gulf of Alaska, and is a key component in understanding large-scale erosion and sedimentation patterns for southeast Alaska and western Canada. We integrate new and existing seismic reflection profiles to provide new constraints on the Baranof Fan area, geometry, volume, and channel development. We estimate the fan’s area and total sediment volume to be ∼323,000 km2 and ∼301,000 km3, respectively, making it among the largest deep-sea fans in the world. We show that the Baranof Fan consists of channel-levee deposits from at least three distinct aggradational channel systems: the currently active Horizon and Mukluk channels, and the waning system we call the Baranof channel. The oldest sedimentary deposits are in the northern fan, and the youngest deposits at the fan’s southern extent; in addition, the channels seem to avulse southward consistently through time. We suggest that Baranof Fan sediment is sourced from the Coast Mountains in southeastern Alaska, transported offshore most recently via fjord to glacial sea valley conduits. Because of the translation of the Pacific plate northwest past sediment sources on the North American plate along the Queen Charlotte strike-slip fault, we suggest that new channel formation, channel beheadings, and southward-migrating channel avulsions have been influenced by regional tectonics. Using a simplified tectonic reconstruction assuming a constant Pacific plate motion of 4.4 cm/yr, we estimate that Baranof Fan deposition initiated ca. 7 Ma.

  6. Spatial distribution of the earthquakes in the Vrancea zone and tectonic correlations

    International Nuclear Information System (INIS)

    Bala, Andrei; Diaconescu, Mihai; Biter, Mircea

    2001-01-01

    The tectonic plate evolution of the whole Carpathian Arc and Pannonian back-arc Basin indicates that at least three tectonic units have been in contact and at the same time in relative motion: the East European Plate, the Moesian plate and the Intra-Alpine plate. There were plotted graphically all the earthquake hypocentres from the period 1982-2000 situated in an area which includes Vrancea zone. Because of the great number of events plotted, they were found to describe well the limits of the tectonic plate (plate fragment?) which is supposed to be subducted in this region down to 200 km depth. The hypothesis of a plate fragment delaminated from an older subduction can not be overruled. These limits were put in direct relations with the known geology and tectonics of the area. Available fault plane solutions for the crustal earthquakes are analyzed in correlation with the main faults of the area. A graphic plot of the sunspot number is correlated with the occurrence of the earthquakes with magnitudes greater than 5. (authors)

  7. Numerical modeling of intraplate seismicity with a deformable loading plate

    Science.gov (United States)

    So, B. D.; Capitanio, F. A.

    2017-12-01

    We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ = ηI/ηL the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ = σY/σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

  8. Active tectonics and earthquake potential of the Myanmar region

    Science.gov (United States)

    Wang, Yu; Sieh, Kerry; Tun, Soe Thura; Lai, Kuang-Yin; Myint, Than

    2014-04-01

    This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subduction and collision associated with the Sunda megathrust beneath and within the Indoburman range and Naga Hills accommodate most of the shortening across the transpressional plate boundary. The Sagaing fault system is the predominant locus of dextral motion associated with the northward translation of India. Left-lateral faults of the northern Shan Plateau, northern Laos, Thailand, and southern China facilitate extrusion of rocks around the eastern syntaxis of the Himalaya. All of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region.

  9. Tectonic evolution of the North Patagonian Andes (41°-44° S) through recognition of syntectonic strata

    Science.gov (United States)

    Echaurren, A.; Folguera, A.; Gianni, G.; Orts, D.; Tassara, A.; Encinas, A.; Giménez, M.; Valencia, V.

    2016-05-01

    The North Patagonian fold-thrust belt (41°-44° S) is characterized by a low topography, reduced crustal thickness and a broad lateral development determined by a broken foreland system in the retroarc zone. This particular structural system has not been fully addressed in terms of the age and mechanisms that built this orogenic segment. Here, new field and seismic evidence of syntectonic strata constrain the timing of the main deformational stages, evaluating the prevailing crustal regime for the different mountain domains through time. Growth strata and progressive unconformities, controlled by extensional or compressive structures, were recognized in volcanic and sedimentary rocks from the cordilleran to the extra-Andean domain. These data were used to construct a balanced cross section, whose deep structure was investigated through a thermomechanical model that characterizes the upper plate rheology. Our results indicate two main compressive stages, interrupted by an extensional relaxation period. The first contractional stage in the mid-Cretaceous inverted Jurassic-Lower Cretaceous half graben systems, reactivating the western Cañadón Asfalto rift border ~ 500 km away from the trench, at a time of arc foreland expansion. For this stage, available thermochronological data reveal forearc cooling episodes, and global tectonic reconstructions indicate mid-ocean ridge collisions against the western edge of an upper plate with rapid trenchward displacement. Widespread synextensional volcanism is recognized throughout the Paleogene during plate reorganization; retroarc Paleocene--Eocene flare up activity is interpreted as product of a slab rollback, and fore-to-retroarc Oligocene slab/asthenospheric derived products as an expression of enhanced extension. The second stage of mountain growth occurred in Miocene time associated with Nazca Plate subduction, reaching nearly the same amplitude than the first compressive stage. Extensional weakening of the upper plate

  10. Net Rotation of the Lithosphere in Mantle Convection Models with Self-consistent Plate Generation

    Science.gov (United States)

    Gerault, M.; Coltice, N.

    2017-12-01

    Lateral variations in the viscosity structure of the lithosphere and the mantle give rise to a discordant motion between the two. In a deep mantle reference frame, this motion is called the net rotation of the lithosphere. Plate motion reconstructions, mantle flow computations, and inferences from seismic anisotropy all indicate some amount of net rotation using different mantle reference frames. While the direction of rotation is somewhat consistent across studies, the predicted amplitudes range from 0.1 deg/Myr to 0.3 deg/Myr at the present-day. How net rotation rates could have differed in the past is also a subject of debate and strong geodynamic arguments are missing from the discussion. This study provides the first net rotation calculations in 3-D spherical mantle convection models with self-consistent plate generation. We run the computations for billions of years of numerical integration. We look into how sensitive the net rotation is to major tectonic events, such as subduction initiation, continental breakup and plate reorganisations, and whether some governing principles from the models could guide plate motion reconstructions. The mantle convection problem is solved with the finite volume code StagYY using a visco-pseudo-plastic rheology. Mantle flow velocities are solely driven by buoyancy forces internal to the system, with free slip upper and lower boundary conditions. We investigate how the yield stress, the mantle viscosity structure and the properties of continents affect the net rotation over time. Models with large lateral viscosity variations from continents predict net rotations that are at least threefold faster than those without continents. Models where continents cover a third of the surface produce net rotation rates that vary from nearly zero to over 0.3 deg/Myr with rapide increase during continental breakup. The pole of rotation appears to migrate along no particular path. For all models, regardless of the yield stress and the

  11. Crustal Magnetic Field Anomalies and Global Tectonics

    Science.gov (United States)

    Storetvedt, Karsten

    2014-05-01

    A wide variety of evidence suggests that the ruling isochron (geomagnetic polarity versus age) hypothesis of marine magnetic lineations has no merit - undermining therefore one of the central tenets of plate tectonics. Instead, variable induction by the ambient geomagnetic field is likely to be the principal agent for mega-scale crustal magnetic features - in both oceanic and continental settings. This revitalizes the fault-controlled susceptibility-contrast model of marine magnetic lineations, originally proposed in the late 1960s. Thus, the marine magnetic 'striping' may be ascribed to tectonic shearing and related, but variable, disintegration of the original iron-oxide mineralogy, having developed primarily along one of the two pan-global sets of orthogonal fractures and faults. In this way, fault zones (having the more advanced mineral alteration) would be characterized by relatively low susceptibility, while more moderately affected crustal sections (located between principal fault zones) would be likely to have less altered oxide mineralogy and therefore higher magnetic susceptibility. On this basis, induction by the present geomagnetic field is likely to produce oscillating magnetic field anomalies with axis along the principal shear grain. The modus operandi of the alternative magneto-tectonic interpretation is inertia-driven wrenching of the global Alpine age palaeo-lithosphere - triggered by changes in Earth's rotation. Increasing sub-crustal loss to the upper mantle during the Upper Mesozoic had left the ensuing Alpine Earth in a tectonically unstable state. Thus, sub-crustal eclogitization and associated gravity-driven delamination to the upper mantle led to a certain degree of planetary acceleration which in turn gave rise to latitude-dependent, westward inertial wrenching of the global palaeo-lithosphere. During this process, 1) the thin and mechanically fragile oceanic crust were deformed into a new type of broad fold belts, and 2) the continents

  12. Tectonic Theory and Practice

    DEFF Research Database (Denmark)

    Frier, Marie; Fisker, Anna Marie; Kirkegaard, Poul Henning

    2010-01-01

    ’ is an example of this sensuous interior transformation of a house into a home, a level of detailing which is, however, seldom represented in the prefabricated house. Consequently, this paper investigates whether interiority can be developed as a tectonic theory and design principle for uniting home and system...... and assembly processes, seems a paradoxical challenge which has left prefabricated houses raw constructions rather than inhabitable homes. Based on the hypothesis that home is determined spatially via sensuous impressions of interiority at the threshold of furniture: The bath in Le Corbusier’s ‘Villa Savoye...... in the development of novel prefab solutions. This is pursued trough a deductive study comparing Gottfried Semper’s theories on the origins of construction with Werner Blaser’s technical and practical studies of the joint. In combining Blaser’s constructive understanding of the joint with the interior softness...

  13. Alfred Wegener - From Continental Drift to Plate Tectonics

    Indian Academy of Sciences (India)

    rise to such incredible heights? What makes ... pattern of land and sea throughout the geological history of the. Earth. ..... eventually reaches a level that exceeds the slipping-point of rocks on either .... Clement of Florida International. University ...

  14. Water in geodynamical models of mantle convection and plate tectonics

    Science.gov (United States)

    Rodríguez-González, J.; Van Hunen, J.; Chotalia, K.; Lithgow-Bertelloni, C. R.; Rozel, A.; Tackley, P. J.; Nakagawa, T.

    2017-12-01

    The presence of water in the the mantle has a significant effect in the dynamical and thermal evolution of Earth, which partially explains the differences with other planets and is a key factor for the presence of life on Earth. First, a small amount of water can decrease the mantle viscosity by a several orders of magnitude, thereby changing the convection regime and affecting the thermal evolution. Second, the presence of water significantly changes the solidus curve, with crucial implications for melting. Third, water in the mantle can change the Clapeyron slope of mantle materials, which changes the depth at which phase transitions take place. The thermal and dynamical evolution of Earth under the presence of water in the mantle has been the focus of recent studies, but many questions remain unanswered. In this project we intend to investigate how the maximum water capacity of different mantle regions affects water transport and Earth's convective regime. We will study the effect phase transitions under the presence of water, which can change the buoyancy of slabs in the transition zone. We present preliminary results numerical models of global mantle convection for the whole history of earth using the numerical geodynamics software tool StagYY. We will use a new parametrisation of dehydration processes, obtained from high-resolution numerical simulations, to implement a more accurate description of the water released from the slab as it travels through the mantle. We have integrated recent experimental results of the water capacity of deep mantle minerals to study the water circulation and the total water budget. We use data from the most recent experiments and ab-inito calculations to implement a realistic rheology.

  15. Learning about Plate Tectonics through Argument-Writing

    Science.gov (United States)

    Klein, Perry D.; Samuels, Boba

    2010-01-01

    In a quasi-experimental study (N = 60), grade 7/8 teachers students were taught to write arguments in content-area subjects. After instruction, students drew on document portfolios to write on a new topic: "Do the continents drift?" In a MANCOVA, students who participated in argument instruction scored significantly higher than a control…

  16. The tectonic plates are shifting: cultural change vs. mural dyslexia.

    Science.gov (United States)

    Cohn, Kenneth; Friedman, Leonard H; Allyn, Thomas R

    2007-01-01

    In response to a rapidly changing healthcare marketplace, a variety of new business models have arisen, including new specialties (hospitalists), selective care (concierge medicine), and joint ventures (ambulatory surgical centers, specialty hospitals), some with hospitals and others with independent vendors. Since both hospitals and physicians are feeling the squeeze of rising expenses, burdensome regulations, heightened consumer expectations, and stagnant or decreasing reimbursement, the response to global economic competition and the need to improve clinical and financial outcomes can bring physicians and hospitals together rather than drive them farther apart. In response to perceived threats, physicians and hospital executives can engage in defensive reasoning that may feel protective but can also lead to mural dyslexia, the inability or unwillingness to see the handwriting on the wall. The strategies of positive deviance (finding solutions that already exist in the community rather than importing best practices), appreciative inquiry (building on success rather than relying solely on root-cause analyses of problems), and structured dialogue (allowing practicing physicians to articulate clinical priorities rather than assuming they lack the maturity and will to come to consensus) are field-tested approaches that allow hospital leaders to engage practicing physicians and that can help both parties work more interdependently to improve patient care in a dynamically changing environment. Physician-hospital collaboration based on transparency, active listening, and prompt implementation can offer sustainable competitive advantage to those willing to embark on a lifetime learning journey.

  17. Dynamics of subduction and continental collision: Influence of the nature of the plate contact. Geologica Ultraiectina (284)

    NARCIS (Netherlands)

    De Franco, R.

    2008-01-01

    At convergent plate boundaries, the properties of the actual plate contact are important for the overall dynamics. Convergent plate boundaries both mechanically decouple and link tectonic plates and accommodate large amounts of strain. We investigate two fundamental physical states of the subduction

  18. GEODYNAMIC ACTIVITY OF MODERN STRUCTURES AND TECTONIC STRESS FIELDS IN NORTHEAST ASIA

    Directory of Open Access Journals (Sweden)

    L. P. Imaeva

    2017-01-01

    Full Text Available Based on the analysis of changes in the stress-strain state of the crust at the boundary of the Eurasian and North American tectonic plates, we develop a dynamic model of the main seismogenerating structures inNortheast Asia. We have established a regularity in changes of geodynamic regimes within the interplate boundary between the Kolyma-Chukotka crustal plate and the Eurasian, North American and Pacific tectonic plates: spreading in the Gakkel Ridge area; rifting in the Laptev Sea shelf; a mixture of tectonic stress types in the Kharaulakh segment; transpression in the Chersky seismotectonic zone, in the segment from the Komandor to the Aleutian Islands, and in the Koryak segment; and crustal stretching in the Chukotka segment.

  19. Tectonics in the Northwestern West Philippine Basin

    Institute of Scientific and Technical Information of China (English)

    Ni Xianglong; Wu Shiguo; Shinjo Ryuichi

    2008-01-01

    The West Philippine basin (WPB) is a currently inactive marginal basin belonging to Philippine Sea plate, which has a complex formation history and various crust structures. Based on gravity, magnetic and seismic data, the tectonics in West Philippine basin is characterized by amagnma spreading stage and strike slip fractures. NNE trending Okinawa-Luzon fracture zone is a large fracture zone with apparent geomorphology and shows a right-handed movement. The results of joint gravity-magnetic-seismic inversion suggest that the Okinawa-Luzon fracture zone has intensive deformation and is a transform fault. Western existence of the NW trending fractures under Ryukyu Islands Arc is the main cause of the differences between south and north Okinawa Trough. The Urdaneta plateau is not a remained arc, but remnant of mantle plume although its lava chemistry is similar to oceanic island basalt (OIB).

  20. Teaching Tectonics to Undergraduates with Web GIS

    Science.gov (United States)

    Anastasio, D. J.; Bodzin, A.; Sahagian, D. L.; Rutzmoser, S.

    2013-12-01

    Geospatial reasoning skills provide a means for manipulating, interpreting, and explaining structured information and are involved in higher-order cognitive processes that include problem solving and decision-making. Appropriately designed tools, technologies, and curriculum can support spatial learning. We present Web-based visualization and analysis tools developed with Javascript APIs to enhance tectonic curricula while promoting geospatial thinking and scientific inquiry. The Web GIS interface integrates graphics, multimedia, and animations that allow users to explore and discover geospatial patterns that are not easily recognized. Features include a swipe tool that enables users to see underneath layers, query tools useful in exploration of earthquake and volcano data sets, a subduction and elevation profile tool which facilitates visualization between map and cross-sectional views, drafting tools, a location function, and interactive image dragging functionality on the Web GIS. The Web GIS platform is independent and can be implemented on tablets or computers. The GIS tool set enables learners to view, manipulate, and analyze rich data sets from local to global scales, including such data as geology, population, heat flow, land cover, seismic hazards, fault zones, continental boundaries, and elevation using two- and three- dimensional visualization and analytical software. Coverages which allow users to explore plate boundaries and global heat flow processes aided learning in a Lehigh University Earth and environmental science Structural Geology and Tectonics class and are freely available on the Web.

  1. Two possibilities for New Siberian Islands terrane tectonic history during the Early Paleozoic based on paleomagnetic data

    Science.gov (United States)

    Metelkin, Dmitry V.; Chernova, Anna I.; Vernikovsky, Valery A.; Matushkin, Nikolay Yu.

    2017-04-01

    The New Siberian Islands (NSI), located in the East Siberian Sea in the junction region of various structural elements, are a key target for deciphering the tectonic evolution of the Eastern Arctic. In recent years, we went on several expeditions and gathered an extensive geological material for this territory. Among other things, we could prove that the basement of the De Long and Anjou archipelagos structures is Precambrian and the overlying Paleozoic sections formed within the same terrane. The form of the boundaries of the NSI terrane are actively debated and are probably continued from the Lyakhovsky islands in the south-west to the southern parts of the submerged Mendeleev Ridge, for which there is increasing evidence of continental crust. Today there are several models that interpret the Paleozoic-Mesozoic tectonic history and structural affiliation of the NSI terrane. Some propose that the Paleozoic sedimentary section formed in a passive margin setting of the Siberian paleocontinent. Others compare its history with marginal basins of the Baltica and Laurentia continents or consider the NSI terrane as an element of the Chukotka-Alaska microplate. These models are mainly based on results of paleobiogeographical and lithological-facies analyses, including explanations of probable sources for detrital zircons. Our paleomagnetic research on sedimentary, volcanogenic-sedimentary and igneous rocks of the Anjou (Kotelny and Bel'kovsky islands) and De Long (Bennett, Jeannette and Henrietta islands) archipelagos let us calculate an apparent polar wander path for the early Paleozoic interval of geological history, which allows us to conclude that the NSI terrane could not have been a part of the continental plates listed above, but rather had active tectonic boundaries with them. Our paleomagnetic data indicate that the NSI terrane drifted slowly and steadily in the tropical and subtropical regions no higher than 40 degrees. However, the main uncertainty for the

  2. Convergent plate margin dynamics : New perspectives from structural geology, geophysics and geodynamic modelling

    NARCIS (Netherlands)

    Schellart, W. P.; Rawlinson, N.

    2010-01-01

    Convergent plate margins occur when two adjoining tectonic plates come together to form either a subduction zone, where at least one of the converging plates is oceanic and plunges beneath the other into the mantle, or a collision zone, where two continents or a continent and a magmatic arc collide.

  3. Three-dimensional dynamic laboratory models of subduction with an overriding plate and variable interplate rheology

    NARCIS (Netherlands)

    Duarte, João C.; Schellart, Wouter P.; Cruden, Alexander R.

    2013-01-01

    Subduction zones are complex 3-D features in which one tectonic plate sinks underneath another into the deep mantle. During subduction the overriding plate (OP) remains in physical contact with the subducting plate and stresses generated at the subduction zone interface and by mantle flowforce the

  4. Teaching And Learning Tectonics With Web-GIS

    Science.gov (United States)

    Anastasio, D. J.; Sahagian, D. L.; Bodzin, A.; Teletzke, A. L.; Rutzmoser, S.; Cirucci, L.; Bressler, D.; Burrows, J. E.

    2012-12-01

    Tectonics is a new curriculum enhancement consisting of six Web GIS investigations designed to augment a traditional middle school Earth science curriculum. The investigations are aligned to Disciplinary Core Ideas: Earth and Space Science from the National Research Council's (2012) Framework for K-12 Science Education and to tectonics benchmark ideas articulated in the AAAS Project 2061 (2007) Atlas of Science Literacy. The curriculum emphasizes geospatial thinking and scientific inquiry and consists of the following modules: Geohazards, which plate boundary is closest to me? How do we recognize plate boundaries? How does thermal energy move around the Earth? What happens when plates diverge? What happens when plate move sideways past each other? What happens when plates collide? The Web GIS interface uses JavaScript for simplicity, intuition, and convenience for implementation on a variety of platforms making it easier for diverse middle school learners and their teachers to conduct authentic Earth science investigations, including multidisciplinary visualization, analysis, and synthesis of data. Instructional adaptations allow students who are English language learners, have disabilities, or are reluctant readers to perform advanced desktop GIS functions including spatial analysis, map visualization and query. The Web GIS interface integrates graphics, multimedia, and animation in addition to newly developed features, which allow users to explore and discover geospatial patterns that would not be easily visible using typical classroom instructional materials. The Tectonics curriculum uses a spatial learning design model that incorporates a related set of frameworks and design principles. The framework builds on the work of other successful technology-integrated curriculum projects and includes, alignment of materials and assessments with learning goals, casting key ideas in real-world problems, engaging students in scientific practices that foster the use of key

  5. Biological modulation of tectonics

    Science.gov (United States)

    Sleep, N. H.; Bird, D. K.

    2008-12-01

    Photosynthesis has had geologic consequences over the Earth's history. In addition to modifying Earth's atmosphere and ocean chemistry, it has also modulated tectonic processes through enhanced weathering and modification of the nature and composition of sedimentary rocks within fold mountain belts and convergent margins. Molecular biological studies indicate that bacterial photosynthesis evolved just once and that most bacterial clades descend from this photosynthetic common ancestor. Iron-based photosynthesis (ideally 4FeO + CO2 + H2O = 2Fe2O3 + CH2O) was the most bountiful anoxygenic niche on land. The back reaction provided energy to heterotrophic microbes and returned FeO to the photosynthetic microbes. Bacterial land colonists evolved into ecosystems that effectively weathered FeO-bearing minerals and volcanic glass. Clays, sands, and dissolved cations from the weathering process entered the ocean and formed our familiar classes sedimentary rocks: shales, sandstones, and carbonates. Marine photosynthesis caused organic carbon to accumulate in black shales. In contrast, non-photosynthetic ecosystems do not cause organic carbon to accumulate in shale. These evolutionary events occurred before 3.8 Ga as black shales are among the oldest rock types (Rosing and Frei, Earth Planet. Sci. Lett. 217, 237-244, 2004). Thick sedimentary sequences deformed into fold mountain belts. They remelted at depth to form granitic rocks (Rosing et al., Palaeoclimatol. Palaeoecol. 232, 99-11, 2006). Regions of outcropping low-FeO rocks including granites, quartzites, and some shales were a direct result. This dearth of FeO favored the evolution of oxic photosynthesis of cyanobacteria from photosynthetic soil bacteria. Black shales have an additional modulation effect on tectonics as they concentrate radioactive elements, particularly uranium (e.g. so that the surface heat flow varies by a factor of ca. 2). Thick sequences of black shales at continental rises of passive margins are

  6. Phanerozoic tectonic evolution of the Circum-North Pacific

    Science.gov (United States)

    Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Norton, Ian O.; Khanchuk, Alexander I.; Stone, David B.; Scotese, Christopher R.; Scholl, David W.; Fujita, Kazuya

    2000-01-01

    the ancestral margins of present-day Northeast Asia and northwestern North America. The rifting resulted in the fragmentation of each continent and the formation of cratonal and passive continental-margin terranes that eventually migrated and accreted to other sites along the evolving margins of the original or adjacent continents. (2) From about the Late Triassic through the mid-Cretaceous, a succession of island arcs and tectonically paired subduction zones formed near the continental margins. (3) From about mainly the mid-Cretaceous through the present, a succession of igneous arcs and tectonically paired subduction zones formed along the continental margins. (4) From about the Jurassic to the present, oblique convergence and rotations caused orogenparallel sinistral and then dextral displacements within the upper-plate margins of cratons that have become Northeast Asia and North America. The oblique convergences and rotations resulted in the fragmentation, displacement, and duplication of formerly more nearly continuous arcs, subduction zones, and passive continental margins. These fragments were subsequently accreted along the expanding continental margins. (5) From the Early Jurassic through Tertiary, movement of the upper continental plates toward subduction zones resulted in strong plate coupling and accretion of the former island arcs and subduction zones to the continental margins. Accretions were accompanied and followed by crustal thickening, anatexis, metamorphism, and uplift. The accretions resulted in substantial growth of the North Asian and North American Continents. (6) During the middle and late Cenozoic, oblique to orthogonal convergence of the Pacifi c plate with present-day Alaska and Northeast Asia resulted in formation of the modern-day ring of volcanoes around the Circum-North Pacific. Oblique convergence between the Pacific plate and Alaska also resulted in major dextral-slip faulting in interior and southern Alaska and along the western p

  7. Posterior column acetabular fracture fixation using a W-shaped angular plate: A biomechanical analysis.

    Directory of Open Access Journals (Sweden)

    Ke Su

    Full Text Available The purpose of this study was to compare the stability and feasibility of four fixation constructs in a posterior column acetabular fracture: one reconstruction plate, one reconstruction plate and lag screw, two reconstruction plates, and a W-shaped acetabular angular plate.Twenty embalmed cadaveric pelvises with a posterior column acetabular fractures were allocated to one of four groups: 1 a reconstruction plate, 2 a reconstruction plate with a posterior column lag screw, 3 double reconstruction plates, and 4 a W-shaped acetabular angular plate. These constructs were mechanically loaded on a testing machine, and construct stiffness values were measured. Strain gauges were utilized to measure the mechanical behavior in the condition of compressive force.Final stiffness was not different between the two reconstruction plates (445.81±98.30 N/mm and the W-shaped acetabular angular plate (447.43±98.45 N/mm, p = 0.524, both of which were superior to a single reconstruction plate (248.90±61.95 N/mm and a combined plate and lag screw (326.41±94.34 N/mm. Following the fixation of the W-shaped acetabular angular plate, the strain distribution was similar to the intact condition around the acetabulum. The parameters of the W-shaped acetabular angular plate that were observed at the superior region of the acetabulum were less than those of a single reconstruction plate (p<0.05, a single reconstruction plate with lag screw (p<0.05, and two reconstruction plates (p<0.05.The novel W-shaped acetabular angular plate fixation technique was able to provide the biomechanically stiffest construct for stabilization of a posterior column acetabular fracture; it also resulted in a partial restoration of joint loading parameters toward the intact state.

  8. Tectonic evolution of Mars

    International Nuclear Information System (INIS)

    Wise, D.U.; Golombek, M.P.; McGill, G.E.

    1979-01-01

    Any model for the tectonic evolution of Mars must account for two major crustal elements: the Tharsis bulge and the topographically low and lightly crated northern third of the planet. Ages determined by crater density indicate that both of these elements came into existence very early in Martian history, a conclusion that holds no matter which of the current crater density versus age curves is used. The size of these two major crustal elements and their sequential development suggest that both may be related to a global-scale internal process. It is proposed that the resurfacing of the northern third of Mars is related to subcrustal erosion and isostatic foundering during the life of a first-order convection cell. With the demise of the cell, denser segregations of metallic materials began to coalesce as a gravitatively unstable layer which finally overturned to form the core. In the overturn, lighter crustal materials was shifted laterally and underplated beneath Tharsis to cause rapid and permanent isostatic rise. This was followed by a long-lived thermal phase produced by the hot underplate and by the gravitative energy of core formation slowly making its way to the surface to produce the Tharsis volcanics

  9. The Ecology of Urban Tectonics

    DEFF Research Database (Denmark)

    Beim, Anne; Hvejsel, Marie Frier

    2016-01-01

    This paper is related to previous research by the authors that examine the phenomenon of tectonics as architectural design theory and method. These studies have shown that the notion of tectonics at large is associated with exclusive architecture, and that, as a profession architects have...... to develop methods for applying tectonic knowledge extracted from significant existing examples for developing future practical methods (Frampton 2002: 81). The specific intention of this paper is to push the understanding of tectonics further, into the scale of the urban context and thereby to discuss...... using Hansen’s work as a case study. (Beim & Madsen (ed.) 2014) Methodologically this has been done by applying the notion of ‘urban tectonics’ inspired by the work of Eduard F. Sekler, as a critical lens. (Sekler 1964, Sekler 1965) Through this lens we study how Hansen was able to treat culture...

  10. A Possible Differentially Shortened Strike-slip Plate Boundary: the Okhotsk Plate Example.

    Science.gov (United States)

    Hindle, D.; Egorov, V.; Mackey, K. G.; Fujita, K.

    2004-12-01

    The Okhotsk plate has been postulated based on a combination of GPS geodetic inversions (REVEL1), seimsicity, geologic and lineament data. Lying between the North American and Eurasian plates, its northwestern corner would appear to be undergoing compression in a scissors motion between the two bounding plates. Extrusion tectonics along multiple, large strike-slip faults within the Okhotsk plate itself have been suggested to allow the escape of material away from the apex of Eurasia-North America. The plate boundary between Okhotsk and North America has been suggested to be diffuse, based on widely scattered minor seismicity. However, the large, left lateral, Ulakhan fault has also been suggested as a candidate plate boundary. We present field geological and geomorphological evidence of the partitioning of deformation between the Ulakhan fault, and several parallel and oblique, linked faults. The Ulakhan fault strand appears to have a maximum displacement of 24 km based on river valley offsets and closing large pull apart basins. Some of the displacement from the Ulakhan fault appears relayed into the plate margin along oblique trending, thrust/oblique slip faults. Estimated shortening over these faults is equivalent to the amount of shortening relayed into the plate margin from the plate boundary. There may be several thrust/oblique slip faults along the Ulakhan fault, which leads to the interesting situation of a segmented, strike-slip plate boundary being actively shortened in a margin parallel direction. This may be the result of postulated extrusion of the Okhotsk plate due to North America/Eurasia convergence. Such a situation would have important consequences for the interpretation of GPS data in a plate tectonic context.

  11. New 40Ar-39Ar dating of Lower Cretaceous basalts at the southern front of the Central High Atlas, Morocco: insights on late Mesozoic tectonics, sedimentation and magmatism

    Science.gov (United States)

    Moratti, G.; Benvenuti, M.; Santo, A. P.; Laurenzi, M. A.; Braschi, E.; Tommasini, S.

    2018-04-01

    This study is based upon a stratigraphic and structural revision of a Middle Jurassic-Upper Cretaceous mostly continental succession exposed between Boumalne Dades and Tinghir (Southern Morocco), and aims at reconstructing the relation among sedimentary, tectonic and magmatic processes that affected a portion of the Central High Atlas domains. Basalts interbedded in the continental deposits have been sampled in the two studied sites for petrographic, geochemical and radiogenic isotope analyses. The results of this study provide: (1) a robust support to the local stratigraphic revision and to a regional lithostratigraphic correlation based on new 40Ar-39Ar ages (ca. 120 Ma) of the intervening basalts; (2) clues for reconstructing the relation between magma emplacement in a structural setting characterized by syn-depositional crustal shortening pre-dating the convergent tectonic inversion of the Atlasic rifted basins; (3) a new and intriguing scenario indicating that the Middle Jurassic-Lower Cretaceous basalts of the Central High Atlas could represent the first signal of the present-day Canary Islands mantle plume impinging, flattening, and delaminating the base of the Moroccan continental lithosphere since the Jurassic, and successively dragged passively by the Africa plate motion to NE. The tectono-sedimentary and magmatic events discussed in this paper are preliminarily extended from their local scale into a peculiar geodynamic setting of a continental plate margin flanked by the opening and spreading Central Atlantic and NW Tethys oceans. It is suggested that during the late Mesozoic this setting created an unprecedented condition of intraplate stress for concurrent crustal shortening, related mountain uplift, and thinning of continental lithosphere.

  12. Earth's glacial record and its tectonic setting

    Science.gov (United States)

    Eyles, N.

    1993-09-01

    Glaciations have occurred episodically at different time intervals and for different durations in Earth's history. Ice covers have formed in a wide range of plate tectonic and structural settings but the bulk of Earth's glacial record can be shown to have been deposited and preserved in basins within extensional settings. In such basins, source area uplift and basin subsidence fulfill the tectonic preconditions for the initiation of glaciation and the accomodation and preservation of glaciclastic sediments. Tectonic setting, in particular subsidence rates, also dictates the type of glaciclastic facies and facies successions that are deposited. Many pre-Pleistocene glaciated basins commonly contain well-defined tectonostratigraphic successions recording the interplay of tectonics and sedimentation; traditional climatostratigraphic approaches involving interpretation in terms of either ice advance/retreat cycles or glacio-eustatic sea-level change require revision. The direct record of continental glaciation in Earth history, in the form of classically-recognised continental glacial landforms and "tillites", is meagre; it is probable that more than 95% of the volume of preserved "glacial" strata are glacially-influenced marine deposits that record delivery of large amounts of glaciclastic sediment to offshore basins. This flux has been partially or completely reworked by "normal" sedimentary processes such that the record of glaciation and climate change is recorded in marine successions and is difficult to decipher. The dominant "glacial" facies in the rock record are subaqueous debris flow diamictites and turbidites recording the selective preservation of poorly-sorted glaciclastic sediment deposited in deep water basins by sediment gravity flows. However, these facies are also typical of many non-glacial settings, especially volcanically-influenced environments; numerous Archean and Proterozoic diamictites, described in the older literature as tillites, have no

  13. Plate Speed-up and Deceleration during Continental Rifting: Insights from Global 2D Mantle Convection Models.

    Science.gov (United States)

    Brune, S.; Ulvrova, M.; Williams, S.

    2017-12-01

    The surface of the Earth is divided into a jigsaw of tectonic plates, some carrrying continents that disperse and aggregate through time, forming transient supercontinents like Pangea and Rodinia. Here, we study continental rifting using large-scale numerical simulations with self-consistent evolution of plate boundaries, where continental break-up emerges spontaneously due to slab pull, basal drag and trench suction forces.We use the StagYY convection code employing a visco-plastic rheology in a spherical annulus geometry. We consider an incompressible mantle under the Boussinesq approximation that is basally and internally heated.We show that continental separation follows a characteristic evolution with three distinctive phases: (1) A pre-rift phase that typically lasts for several hundreds of millions of years with tectonic quiescence in the suture and extensional stresses that are slowly building up. (2) A rift phase that further divides into a slow rift period of several tens of millions of years where stresses continuously increase followed by a rift acceleration period featuring an abrupt stress drop within several millions of years. The speed-up takes place before lithospheric break-up and therefore affects the structural architecture of the rifted margins. (3) The drifting phase with initially high divergence rates persists over tens of millions of years until the system adjust to new conditions and the spreading typically slows down.By illustrating the geodynamic connection between subduction dynamics and rift evolution, our results allow new interpretations of plate tectonic reconstructions. Rift acceleration within the second phase of rifting is compensated by enhanced convergence rates at subduction zones. This model outcome predicts enhanced subduction velocities, e.g. between North America and the Farallon plate during Central Atlantic rifting 200 My ago, or closure of potential back-arc basins such as in the proto-Andean ranges of South America

  14. Strike-slip tectonics during rift linkage

    Science.gov (United States)

    Pagli, C.; Yun, S. H.; Ebinger, C.; Keir, D.; Wang, H.

    2017-12-01

    The kinematics of triple junction linkage and the initiation of transforms in magmatic rifts remain debated. Strain patterns from the Afar triple junction provide tests of current models of how rifts grow to link in area of incipient oceanic spreading. Here we present a combined analysis of seismicity, InSAR and GPS derived strain rate maps to reveal that the plate boundary deformation in Afar is accommodated primarily by extensional tectonics in the Red Sea and Gulf of Aden rifts, and does not require large rotations about vertical axes (bookshelf faulting). Additionally, models of stress changes and seismicity induced by recent dykes in one sector of the Afar triple junction provide poor fit to the observed strike-slip earthquakes. Instead we explain these patterns as rift-perpendicular shearing at the tips of spreading rifts where extensional strains terminate against less stretched lithosphere. Our results demonstrate that rift-perpendicular strike-slip faulting between rift segments achieves plate boundary linkage during incipient seafloor spreading.

  15. An Integrated Age Model for the Cocos Plate using IODP CRISP Drilling Data

    Science.gov (United States)

    Baxter, A. T.; Kutterolf, S.; Schindlbeck, J. C.; Sandoval, M. I.; Barckhausen, U.; Li, Y. X.; Petronotis, K. E.

    2017-12-01

    We present an integrated age model for the incoming Cocos Plate sediments offshore Costa Rica. The data, collected over two IODP Expeditions (334 and 344), provides a medium- to high-resolution record from the initial formation of the ocean crust in the Miocene to the present day. This study provides >50 age control points for the CRISP sediments from Sites U1381 and U1414. Although the two sites are just 10 km apart, there are distinct differences in the sediment and tephra record. Most notable is the presence of a hiatus at Site U1381. The hiatus, which is seen at other sites on the Cocos Plate, but not at Site U1414, may be related to erosion due to bottom water currents, mass wasting from Cocos Ridge subduction or may be related to the closure of the Central American Seaway (CAS). Sediment accumulation rates in the Miocene are comparable to modern abyssal plain rates. However, an increase is observed in the Pleistocene, when detritus from the forearc basin appears at Site U1414 2 Ma, shortly after the initiation of Cocos Ridge subduction. A tectonic model is presented that reconstructs the Cocos Plate, from its formation at 23 Ma to the present day. Eastern Equatorial Pacific (EEP) paleoceanographic events, such as the Miocene `carbonate crash' and the Late Miocene-Early Pliocene `biogenic bloom' observed at Site U1414, are also discussed.

  16. Current deformation in the Tibetan Plateau: a stress gauge in the large-scale India-Asia collision tectonics

    Science.gov (United States)

    Capitanio, F. A.

    2017-12-01

    The quantification of the exact tectonic forces budget on Earth has remained thus far elusive. Geodetic velocities provide relevant constraints on the current dynamics of the coupling between collision and continental tectonics, however in the Tibetan plateau these support contrasting, non-unique models. Here, we compare numerical models of coupled India-Asia plate convergence, collision and continent interiors tectonics to the geodetically-constrained motions in the Tibetan Plateau to provide a quantitative assessment of the driving forces of plate tectonics in the area. The models develop a range of long-term evolutions remarkably similar to the Asian tectonics in the Cenozoic, reproducing the current large-scale motions pattern under a range of conditions. Balancing the convergent margin forces, following subduction, and the far-field forcing along the trail of the subducting continent, the geodetic rates in the Tibetan Plateau can be matched. The comparisons support the discussion on the likely processes at work, allowing inferences on the drivers of plateau formation and its role on the plate margin-interiors tectonics. More in general, the outcomes highlight the unique role of the Tibetan Plateau as a pressure gauge for the tectonic forces on Earth.

  17. Revisit of Criteria and Evidence for the Tectonic Erosion vs Accretion in East Asian Margin

    Science.gov (United States)

    Kimura, G.; Hamahashi, M.

    2015-12-01

    Accretionary and erosive margins provide tectonic end-members in subduction zone and how these tectonic processes might be recorded and recognizable in ancient subduction complexes remains a challenging issue. Tectonic erosion includes sediment subduction and basal erosion along the plate boundary megathrust and drags down the crust of the upper plate into the mantle. Geologic evidence for the erosion is commonly based on lost geological tectono-stratigraphic data, i.e. gaps in the record and indirect phenomena such as subsidence of the forearc slopes. A topographically rough surface such as seamount has been suggested to work like an erosive saw carving the upper plate. Another mechanism of basal erosion has been suggested to be hydrofracturing of upper plate materials due to dehydration-induced fluid pressures, resulting in entrainment of upper plate materials into the basal décollement. Considering the interaction between the ~30 km thick crust of the upper plate and subducting oceanic plate, a subduction dip angle of ~15°, and convergent rate of ~10 cm/year, at least ~1 Ma of continuous basal erosion is necessary to induce clear subsidence of the forearc because the width of plate interface between the upper crustal and subducting plates is about 115 km (30/cos15°). In several examples of subduction zones, for example the Japan Trench and the Middle America Trench off Costa Rica, the subsidence of a few thousand metres of the forearc, combined with a lack of accretionary prism over a period of several million years, suggest that the erosive condition needs to be maintained for several to tens of million years.Such age gaps in the accretionary complex, however, do not automatically imply that tectonic erosion has taken place, as other interpretations such as no accretion, cessation of subduction, and/or later tectonic modification, are also possible. Recent drilling in the forearc of the Nankai Trough suggests that the accretion was ceased between ~12 Ma to

  18. How the continents deform: The evidence from tectonic geodesy

    Science.gov (United States)

    Thatcher, Wayne R.

    2009-01-01

    Space geodesy now provides quantitative maps of the surface velocity field within tectonically active regions, supplying constraints on the spatial distribution of deformation, the forces that drive it, and the brittle and ductile properties of continental lithosphere. Deformation is usefully described as relative motions among elastic blocks and is block-like because major faults are weaker than adjacent intact crust. Despite similarities, continental block kinematics differs from global plate tectonics: blocks are much smaller, typically ∼100–1000 km in size; departures from block rigidity are sometimes measurable; and blocks evolve over ∼1–10 Ma timescales, particularly near their often geometrically irregular boundaries. Quantitatively relating deformation to the forces that drive it requires simplifying assumptions about the strength distribution in the lithosphere. If brittle/elastic crust is strongest, interactions among blocks control the deformation. If ductile lithosphere is the stronger, its flow properties determine the surface deformation, and a continuum approach is preferable.

  19. Tectonics: The meaning of form

    DEFF Research Database (Denmark)

    Christiansen, Karl; Brandt, Per Aage

    Tectonics – The meaning of form deals with one of the core topics of architecture: the relationship between form and content. In the world of architecture, form is not only made from brick, glass and wood. Form means something. When a material is processed with sufficient technical skill and insi...... perspectives. You can read the chapters in any order you like – from the beginning, end or the middle. There is no correct order. The project is methodologically inductive: the more essays you read, the broader your knowledge of tectonics get....

  20. Accessory mineral records of tectonic environments? (Invited)

    Science.gov (United States)

    Storey, C.; Marschall, H. R.; Enea, F.; Taylor, J.; Jennings, E. S.

    2010-12-01

    Accessory mineral research continues to gather momentum as we seek to unleash their full potential. It is now widely recognised that robust accessory minerals, such as zircon, rutile, titanite, allanite and monazite, are archives of important trace elements that can help deduce metamorphic reaction history in metapelites, metabasites and other rock types. Moreover, they are important carriers of certain trace elements and govern or influence the products of partial melting and of fluid-rock interaction (e.g. magmas and mineralisation) in settings like subduction zones and hydrothermal systems. Perhaps most importantly, they can often be dated using the U-Th-Pb system. More recently, radiogenic (Lu-Hf, Sm-Nd, Rb-Sr) and stable (O) isotope systems have been applied and have further pushed the utility of accessory mineral research. In this talk I will discuss some of these advances towards one particular aim: the use of detrital accessory minerals for fingerprinting tectonic environments. This is a particularly laudable aim in Precambrian rocks, for which the preservation potential of orogenic belts and fossil subduction zones and their diagnostic metamorphic rocks is low. The implication is that our understanding of plate tectonics, particularly in the Archaean, is biased by the preserved in-tact rock record. An analogy is that Jack Hills zircons record evidence of Earth’s crust some 400 Ma before the preserved rock record begins. I will focus on some recent advances and new data from rutile and also the mineral inclusion record within zircon, which shows great promise for petrologic interpretation.

  1. Do cratons preserve evidence of stagnant lid tectonics?

    Directory of Open Access Journals (Sweden)

    Derek Wyman

    2018-01-01

    Full Text Available Evidence for episodic crustal growth extending back to the Hadean has recently prompted a number of numerically based geodynamic models that incorporate cyclic changes from stagnant lid to mobile lid tectonics. A large part of the geologic record is missing for the times at which several of these cycles are inferred to have taken place. The cratons, however, are likely to retain important clues relating to similar cycles developed in the Mesoarchean and Neoarchean. Widespread acceptance of a form of plate tectonics by ∼3.2 Ga is not at odds with the sporadic occurrence of stagnant lid tectonics after this time. The concept of scale as applied to cratons, mantle plumes and Neoarchean volcanic arcs are likely to provide important constraints on future models of Earth's geodynamic evolution. The Superior Province will provide some of the most concrete evidence in this regard given that its constituent blocks may have been locked into a stagnant lid relatively soon after their formation and then assembled in the next global plate tectonic interval. Perceived complexities associated with inferred mantle plume – volcanic arc associations in the Superior Province and other cratons may be related to an over estimation of plume size. A possible stagnant lid episode between ∼2.9 Ga and ∼2.8 Ga is identified by previously unexplained lapses in volcanism on cratons, including the Kaapvaal, Yilgarn and Superior Province cratons. If real, then mantle dynamics associated with this episode likely eliminated any contemporaneous mantle plume incubation sites, which has important implications for widespread plumes developed at ∼2.7 Ga and favours a shallow mantle source in the transition zone. The Superior Province provides a uniquely preserved local proxy for this global event and could serve as the basis for detailed numerical models in the future.

  2. Applicability of dinoflagellate cyst stratigraphy to the analyses of passive and active tectonic settings

    NARCIS (Netherlands)

    Wilpshaar, M.

    1995-01-01

    The notion that fluctuating tectonic stress patterns within or between continental plates directly influence the development of a given sedimentary basin is a well-established concept in geotectonics. In recent years it has become increasingly understood that notably the phase of relative

  3. Create Your Plate

    Medline Plus

    Full Text Available ... Plate Share Create Your Plate ! Share: Seven Simple Steps to Create Your Plate It's simple and effective ... foods within each food category. Try these seven steps to get started: Using your dinner plate, put ...

  4. Tectonic phase separation applied to the Sudetic Marginal Fault Zone (NE part of the Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Nováková, Lucie

    2015-01-01

    Roč. 12, č. 2 (2015), s. 251-267 ISSN 1672-6316 R&D Projects: GA ČR GA205/09/1244 Institutional support: RVO:67985891 Keywords : Sudetic Marginal Fault Zone * paleostress reconstruction * active tectonics * frequency analysis Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.017, year: 2015

  5. Reconstructing Rodinia by Fitting Neoproterozoic Continental Margins

    Science.gov (United States)

    Stewart, John H.

    2009-01-01

    Reconstructions of Phanerozoic tectonic plates can be closely constrained by lithologic correlations across conjugate margins by paleontologic information, by correlation of orogenic belts, by paleomagnetic location of continents, and by ocean floor magmatic stripes. In contrast, Proterozoic reconstructions are hindered by the lack of some of these tools or the lack of their precision. To overcome some of these difficulties, this report focuses on a different method of reconstruction, namely the use of the shape of continents to assemble the supercontinent of Rodinia, much like a jigsaw puzzle. Compared to the vast amount of information available for Phanerozoic systems, such a limited approach for Proterozoic rocks, may seem suspect. However, using the assembly of the southern continents (South America, Africa, India, Arabia, Antarctica, and Australia) as an example, a very tight fit of the continents is apparent and illustrates the power of the jigsaw puzzle method. This report focuses on Neoproterozoic rocks, which are shown on two new detailed geologic maps that constitute the backbone of the study. The report also describes the Neoproterozoic, but younger or older rocks are not discussed or not discussed in detail. The Neoproterozoic continents and continental margins are identified based on the distribution of continental-margin sedimentary and magmatic rocks that define the break-up margins of Rodinia. These Neoproterozoic continental exposures, as well as critical Neo- and Meso-Neoproterozoic tectonic features shown on the two new map compilations, are used to reconstruct the Mesoproterozoic supercontinent of Rodinia. This approach differs from the common approach of using fold belts to define structural features deemed important in the Rodinian reconstruction. Fold belts are difficult to date, and many are significantly younger than the time frame considered here (1,200 to 850 Ma). Identifying Neoproterozoic continental margins, which are primarily

  6. Mechanics and Partitioning of Deformation of the Northwestern Okhostk Plate, Northeast Russia

    Science.gov (United States)

    Hindle, D.; Mackey, K.; Fujita, K.

    2007-12-01

    The tectonic evolution and present day deformation of northeastern Russia remains one of the major challenges in plate tectonics. Arguments over the existence of at least a separate Okhotsk plate between North America and Eurasia appear to be resolved on the basis of the latest GPS studies combined with elastic modeling. The question of the mechanical behaviour of the Okhotsk plate, caught between the slowly, obliquely converging North American and Eurasian plates now becomes important. We present an analysis of geological lineaments, micro-seismicity, total seismic moment release and seismic deformation rate and GPS campaign data and global plate tectonic model data (REVEL) to estimate the likelihood of future seismicity and the relative amount of elastic and viscous deformation of the lithosphere of the northwestern Okhotsk plate. We find that it is likely that the Okhotsk plate is cracked into slivers, but that rates of relative motion of these slivers are close to indistinguishable from the behaviour of a single, rigid plate. The analysis also suggests the upper bound for large earthquakes in the region to be Mw 7-7.5 which we expect to occur only on the plate boundary fault itself. This fits geological evidence for a long term offset rate 5-10 times higher on the major plate boundary fault than other lineaments cutting the Okhotsk plate itself.

  7. Global Models of Ridge-Push Force, Geoid, and Lithospheric Strength of Oceanic plates

    Science.gov (United States)

    Mahatsente, Rezene

    2017-12-01

    An understanding of the transmission of ridge-push related stresses in the interior of oceanic plates is important because ridge-push force is one of the principal forces driving plate motion. Here, I assess the transmission of ridge-push related stresses in oceanic plates by comparing the magnitude of the ridge-push force to the integrated strength of oceanic plates. The strength is determined based on plate cooling and rheological models. The strength analysis includes low-temperature plasticity (LTP) in the upper mantle and assumes a range of possible tectonic conditions and rheology in the plates. The ridge-push force has been derived from the thermal state of oceanic lithosphere, seafloor depth and crustal age data. The results of modeling show that the transmission of ridge-push related stresses in oceanic plates mainly depends on rheology and predominant tectonic conditions. If a lithosphere has dry rheology, the estimated strength is higher than the ridge-push force at all ages for compressional tectonics and at old ages (>75 Ma) for extension. Therefore, under such conditions, oceanic plates may not respond to ridge-push force by intraplate deformation. Instead, the plates may transmit the ridge-push related stress in their interior. For a wet rheology, however, the strength of young lithosphere (stress may dissipate in the interior of oceanic plates and diffuses by intraplate deformation. The state of stress within a plate depends on the balance of far-field and intraplate forces.

  8. HVDC Ground Electrodes and Tectonic Setting

    Science.gov (United States)

    Freire, P. F.; Pereira, S. Y.

    2017-12-01

    Ground electrodes in HVDC transmission are huge grounding systems for the DC part of the converter substation, about 1 km wide, sized to inject in the ground DC currents up to 3.5 kA. This work presents an analysis of how the tectonic setting at converter substation location is determinant for the search of the best electrode location (Site Selection) and on its design and performance. It will briefly present the author experience on HVDC electrode design, summarized as follows: Itaipu - Foz do Iguaçu electrodes (transmitter side) located in the middle of Paraná Sedimentary Basin, and Ibiúna electrodes (receiving side) on the border of the basin, 6 km from the geological strike, where the crystalline basement outcrops in São Paulo state; Madeira River - North electrodes (transmitting side) located on the Northwest border of South Amazon Craton, where the crystalline basement is below a shallow sediments layer, and South electrodes (receiving side) located within Paraná Sedimentary Basin; Chile - electrodes located on the Andean forearc, where the Nazca Plate plunges under the South American Plate; Kenya - Ethiopia - electrodes located in the African Rift; Belo Monte - North electrodes (transmitter side) located within the Amazonian Sedimentary Basin, about 35 km of its South border, and South electrodes (receiving side) within Paraná Sedimentary Basin (bipole 1) and on crystalline metamorphic terrain "Brasília Belt" (bipole 2). This diversity of geological conditions results on ground electrodes of different topologies and dimensions, with quite different electrical and thermal performances. A brief study of the geology of the converter stations regions, the so-called Desktop Study, allows for the preview of several important parameters for the site selection and design of the electrodes, such as localization, type, size and estimate of the interference area, which are important predictors of the investment to be made and indications of the design to be

  9. Cenozoic tectonic jumping and implications for hydrocarbon accumulation in basins in the East Asia Continental Margin

    Science.gov (United States)

    Suo, Yanhui; Li, Sanzhong; Yu, Shan; Somerville, Ian D.; Liu, Xin; Zhao, Shujuan; Dai, Liming

    2014-07-01

    Tectonic migration is a common geological process of basin formation and evolution. However, little is known about tectonic migration in the western Pacific margins. This paper focuses on the representative Cenozoic basins of East China and its surrounding seas in the western Pacific domain to discuss the phenomenon of tectonic jumping in Cenozoic basins, based on structural data from the Bohai Bay Basin, the South Yellow Sea Basin, the East China Sea Shelf Basin, and the South China Sea Continental Shelf Basin. The western Pacific active continental margin is the eastern margin of a global convergent system involving the Eurasian Plate, the Pacific Plate, and the Indian Plate. Under the combined effects of the India-Eurasia collision and retrogressive or roll-back subduction of the Pacific Plate, the western Pacific active continental margin had a wide basin-arc-trench system which migrated or ‘jumped’ eastward and further oceanward. This migration and jumping is characterized by progressive eastward younging of faulting, sedimentation, and subsidence within the basins. Owing to the tectonic migration, the geological conditions associated with hydrocarbon and gashydrate accumulation in the Cenozoic basins of East China and its adjacent seas also become progressively younger from west to east, showing eastward younging in the generation time of reservoirs, seals, traps, accumulations and preservation of hydrocarbon and gashydrate. Such a spatio-temporal distribution of Cenozoic hydrocarbon and gashydrate is significant for the oil, gas and gashydrate exploration in the East Asian Continental Margin. Finally, this study discusses the mechanism of Cenozoic intrabasinal and interbasinal tectonic migration in terms of interplate, intraplate and underplating processes. The migration or jumping regimes of three separate or interrelated events: (1) tectonism-magmatism, (2) basin formation, and (3) hydrocarbon-gashydrate accumulation are the combined effects of the

  10. Reorganization of convergent plate boundaries. Geologica Ultraiectina (340)

    NARCIS (Netherlands)

    Baes, M.

    2011-01-01

    It is still unclear where a subduction is initiated and what are the responsible mechanisms involved in subduction initiation process. Understanding of subduction initiation will advance our knowledge of how and when plate tectonics started on Earth. Another issue concerning the subduction process

  11. Long-term evolution of the Campine area in Northern Belgium: past and expected future evolution of tectonics and climate

    International Nuclear Information System (INIS)

    De Craen, M.; Beerten, K.; Brassinnes, S.; Wouters, L.

    2012-01-01

    Document available in extended abstract form only. Disposal of radioactive waste in a geological repository involves the reliance, now and in the long-term future, on the geological and hydrogeological environment. In preparation of the safety and feasibility case 1 (SFC1), the long-term geodynamic evolution of Boom Clay and its geological environment in the Campine area in northern Belgium is studied. Time frames considered are the geological past and the future 1 million year. The idea is that the past long-term evolution can be extended to predict what might happen in the future. In this paper, we first focusses on the past long-term tectonic evolution of the Campine area, and make an extrapolation for the future 1 Ma. We then focus on past climate evolution, and similarly, an assessment of possible future climate conditions is made for the Campine area within the next 1 Ma. Another paper focusses on the combined effect of tectonics and climate on the evolution of the surface environment in the Campine area for the next 1 Ma, with respect to geomorphological, pedological and hydrological processes. During the Palaeozoic, the geodynamic evolution of the Campine area was mainly determined by tectonics. A large intermittently subsiding sedimentary basin existed in which large amounts of sediments were deposited, and which was protected by the Brabant Massif from major oro-genetic compressive processes. Palaeozoic sediments in the Campine Basin reach a maximum thickness of 4000 m. During Mesozoic and Cenozoic, its geodynamic evolution was the interactive result of plate tectonics, sea level changes and climate evolution. Further subsidence resulted in a thick sequence of sedimentary deposits. Mesozoic sediments are found throughout the Campine area while remains of Jurassic-Triassic sediments are found only in the central Roer Valley Graben in the east. The Cenozoic is characterised by a succession of sub-horizontal layers of Tertiary clays and sands and covered by

  12. Is There Really A North American Plate?

    Science.gov (United States)

    Krill, A.

    2011-12-01

    Lithospheric plates are typically identified from earthquake epicenters and evidence such as GPS movements. But no evidence indicates a plate boundary between the North American and South American Plates. Some plate maps show them separated by a transform boundary, but it is only a fracture zone. Other maps show an "undefined plate boundary" or put no boundary between these two plates (check Google images). Early plate maps showed a single large American Plate, quite narrow east of the Caribbean Plate (Le Pichon 1968, Morgan 1968). The North and South American Plates became established by the leading textbook Earth (Press & Siever 1974). On their map, from a Scientific American article by John Dewey (1972), these new plates were separated by an "uncertain plate boundary." The reasons for postulating a North American Plate were probably more psychological than geological. Each of the other continents of the world had its own plate, and North American geologists naturally wanted theirs. Similarly, European geographers used to view Europe as its own continent. A single large plate should again be hypothesized. But the term American Plate would now be ambiguous ("Which plate, North or South?") Perhaps future textbook authors could call it the "Two-American Plate." Textbook authors ultimately decide such global-tectonic matters. I became aware of textbook authors' opinions and influence from my research into the history of Alfred Wegener's continental drift (see Fixists vs. Mobilists by Krill 2011). Leading textbook author Charles Schuchert realized that continental drift would abolish his cherished paleogeographic models of large east-west continents (Eria, Gondwana) and small oceans (Poseiden, Nereis). He and his junior coauthors conspired to keep drift evidence out of their textbooks, from the 1934-editions until the 1969-editions (Physical Geology by Longwell et al. 1969, Historical Geology by Dunbar & Waage 1969). Their textbooks ruled in America. Textbooks

  13. Geoprospective study of a nuclear waste repository. Prospective tectonics: convergent and divergent episodes, evolution of stress during the next 100,000 years

    International Nuclear Information System (INIS)

    Gros, Y.

    1985-01-01

    Within the frame of a contract with the CEC, dealing with storage and disposal of radioactive wastes in geological formations, the B.R.G.M. has been involved in a research on prospective tectonics. Within the Western European continental plate, since Mesozoic times, one sees the alternation or succession of convergent and divergent tectonic episodes. These tectonic episodes, although representing geologically discontinuous phenomena, still have time periods of between 4 to 40 millions years. These tectonic phenomena are the cause of the formation or reactivation, at all scales in the continental plate, of brittle, fault-like structures. Tectonic analysis and the in situ measures of stress and the earthquake focal phenomena show that, from the lower Quaternary to the present, the Western European continental plate has been subjected to NNW to SSE convergent stress. A study of the arrangement of European and African plates in the Western Mediterranean shows that the entire region, is undergoing a period of continental collision. The change in the process implies a westerly continental drift of the Spanish plate, a movement which would take several million years. On the Western European scale, the most likely hypothesis during the next 100,000 years is the persistance of the present stress trending approximately N-5. On the other hand, on a local scale, reorganisations of this stress are possible, owing to the presence of tectonic or lithological heterogeneities

  14. How sea level change mediates genetic divergence in coastal species across regions with varying tectonic and sediment processes.

    Science.gov (United States)

    Dolby, Greer A; Ellingson, Ryan A; Findley, Lloyd T; Jacobs, David K

    2018-02-01

    Plate tectonics and sediment processes control regional continental shelf topography. We examine the genetic consequences of how glacial-associated sea level change interacted with variable nearshore topography since the last glaciation. We reconstructed the size and distribution of areas suitable for tidal estuary formation from the last glacial maximum, ~20 thousand years ago, to present from San Francisco, California, USA (~38°N) to Reforma, Sinaloa, Mexico (~25°N). We assessed range-wide genetic structure and diversity of three codistributed tidal estuarine fishes (California Killifish, Shadow Goby, Longjaw Mudsucker) along ~4,600 km using mitochondrial control region and cytB sequence, and 16-20 microsatellite loci from a total of 524 individuals. Results show that glacial-associated sea level change limited estuarine habitat to few, widely separated refugia at glacial lowstand, and present-day genetic clades were sourced from specific refugia. Habitat increased during postglacial sea level rise and refugial populations admixed in newly formed habitats. Continental shelves with active tectonics and/or low sediment supply were steep and hosted fewer, smaller refugia with more genetically differentiated populations than on broader shelves. Approximate Bayesian computation favoured the refuge-recolonization scenarios from habitat models over isolation by distance and seaway alternatives, indicating isolation at lowstand is a major diversification mechanism among these estuarine (and perhaps other) coastal species. Because sea level change is a global phenomenon, we suggest this top-down physical control of extirpation-isolation-recolonization may be an important driver of genetic diversification in coastal taxa inhabiting other topographically complex coasts globally during the Mid- to Late Pleistocene and deeper timescales. © 2018 John Wiley & Sons Ltd.

  15. Rheological and structural inheritance : key parameters for intra-plate deformation. A study based on analogue models

    NARCIS (Netherlands)

    Calignano, E.

    2015-01-01

    Mountain ranges are impressive tectonic features that characterize the Earth’s surface. Their formation is often associated with regions where two tectonic plates, making up the Earth surface, collide, as in the case of the Himalaya. While the surface is forced to uplift, the displacement of rocks

  16. Cyclic Sequences, Events and Evolution of the Sino-Korean Plate,with a Discussion on the Evolution of Molar-tooth Carbonates,Phosphorites and Source Rocks

    Institute of Scientific and Technical Information of China (English)

    MENG Xianghua; GE Ming

    2003-01-01

    This paper gives an account of the research that the authors conducted on the cyclic sequences, events and evolutionary history from Proterozoic to Meso-Cenozoic in the Sino-Korean plate based on the principle of the Cosmos-Earth System. The authors divided this plate into 20 super-cyclic or super-mega-cyclic periods and more than 100 Oort periods. The research focused on important sea flooding events, uplift interruption events, tilting movement events, molar-tooth carbonate events, thermal events, polarity reversal events, karst events, volcanic explosion events and storm events, as well as types of resource areas and paleotectonic evolution. By means of the isochronous theory of the Cosmos-Earth System periodicity and based on long-excentricity and periodicity, the authors elaborately studied the paleogeographic evolution of the aulacogen of the Sino-Korean plate, the oolitic beach platform formation, the development of foreland basin and continental rift valley basin, and reconstructed the evolution of tectonic paleogeography and stratigraphic framework in the Sino-Korean plate in terms of evolutionary maps. Finally, the authors gave a profound discussion on the formation and development of molar-tooth carbonates, phosphorites and source rocks.

  17. Satellite Gravity Transforms Unmask Tectonic Pattern of Arabian-African Region

    Science.gov (United States)

    Eppelbaum, Lev; Katz, Youri

    2017-04-01

    central parts of the Arabian and Somalian plates. Both these plates are countered by low-thickness lithospheric zones corresponding to the active rift zones. As it is indicated in the map, the thick lithospheric zones are associated with collisional zones at boundaries between the cratons and mobile belts. We suggest that the lowered values in the northern boundaries of the Arabian Plate correspond to subduction zones. The zones of lowered values in the middle of western part of the region correspond to the Neoproterozoic belt where ophiolitic and back-arc complexes with a thinned crust (e.g., Stern et al., 2004) are developed. Compiled satellite derived gravity field and a set of SGT were utilized for development of a novel tectono-geophysical zonation map of the Arabian-African region. Structurally- geodynamically this region is one of the key Earth's megastructures where are closely disposed remain elements of the Tethys Ocean crust (Ben-Avraham et al., 2002; Robertson, 2004), most ancient Early Permian reversly magnetized Kiama zone (Eppelbaum and Katz, 2012b; Eppelbaum et al., 2014), and the youngest modern oceanic crust of the Afar triangle developed among the continental lumps (Yirgu et al., 2006; Bastow et al., 2011). The tectonic zonation was carried out with application of three main principles of tectonic analysis: (1) classic basis of space-temporary reflection of structural complexes, (2) modern structural-geodynamic approach derived from the plate tectonic reconstructions where essential role plays analysis of rift, tectonic transform and collision forms of Earth's development, (3) revealing of intricate correlation between the mapped tectono-structural elements and lithospheric-mantle complexes delineated by using both conventional geophysical methods (seismic, seismological, thermal data, etc.) and comprehensive analysis of satellite derived gravity data. Compiled tectonic map of the region (00 - 35.60 north, and 300 - 570 east) indicates that Precambrian

  18. Measurements of Active Tectonic Deformation on the Guerrero Coast, Mexico

    Science.gov (United States)

    Ramirez, T.; Cundy, A.; Carranza-Edwards, A.; Morales, E.; Kostoglodov, V.; Urrutia-Fucugauchi, J.

    2004-12-01

    The study of tectonic deformation rates using displaced shoreline features is relatively well-established, and has provided much useful information on seismic hazard. Such studies have frequently been complemented by analysis of the coastal sedimentary record, where past marine to terrestrial environmental changes (and vice versa) may be recorded by clear changes in stratigraphy. Studies of this type are particularly valuable for tectonically-active areas where the preservation of former shoreline features is poor, or where long-term subsidence has resulted in their erosion, drowning or burial. The specific objective of this study is to derive rates of tectonic deformation from geomorphic and stratigraphic studies of the Guerrero coastal area, and to examine the feasibility of this stratigraphic approach in the coastal lagoons of the Mexican Pacific coast, in the Guerrero gap. The Guerrero gap coastal area, where a major earthquake is expected to occur, parallels the Cocos plate subduction zone. Here convergence rates vary from 5.2 cm/yr to 5.8 cm/yr. The Guerrero gap has experienced several historical earthquakes, notably the 1911 (7.8 Ms). However, no large magnitude events since the 1911 earthquake and only a few Ms~6 events have occurred near the Guerrero gap edges. It is expected that a major interplate earthquake of estimated magnitude Mw=8.1 to 8.4 has a high probability to occur. Landforms within the Guerrero gap indicate that the coast is subsiding. A series of key indicators such as elongated islands reminiscent of ancient barriers, submerged barriers island, extensive marshy environments, increased depths in the lagoons, and submerged anthropogenic features (shell mounds), among others, suggest active tectonic subsidence of the coast. In contrast, the adjacent northwest area off the Guerrero gap exhibits landforms characteristic of tectonic uplift (marine terraces and uplifted beach ridges), indicating a different seismo-tectonic regime northwest of the

  19. Integrated geographic information systems (IGIS) analysis and definition of the tectonic framework of northern Mexico

    Science.gov (United States)

    Martinez Pina, Carlos Manuel

    Crustal rupture structures reactivated in the course of the tectonic history of northern Mexico are the surface expressions of planes of weakness, in the form of simple or composite rectilinear features or slightly curved, defined as lineaments. Unless otherwise defined as strike-slip faults, lineaments are part of parallel and sub-parallel oblique convergent or oblique divergent tectonic zones cross cutting the Sierra Madre Occidental and northern Mexico, in a NW trend. These shear zones are the response to the oblique subduction of the Farallon plate beneath North America. Kinematic analysis of five selected sites in northern Mexico, three basins and two compressional shear zones, proved possible a combination of shear mechanism diagram and models from analogue materials, with satellite imagery and geographic information systems, as an aid to define strike-slip fault motion. This was done using a reverse engineering process by comparing geometries. One of the sites assessed, involving the Parras Basin, Coahuila Block (CB), San Marcos fault, a postulated PBF-1 fault, allowed for palinpastic reconstruction of the CB that corroborated the results of the vector motion defined, in addition to an extension of ˜25% in a northwest southeast direction. A GIS-based compilation and georeferenced regional structural studies by several researchers were used as ground control areas (GCA); their interpolation and interpretation, resulted in a tectonic framework map of northern Mexico. In addition, shaded relief models overlaid by the lineaments / fault layer allowed structural analyses of basins related to these major structures. Two important results were obtained from this study: the Tepehuanes-San Luis-fault (TSL) and the Guadalupe fault, named herein, displaces the Villa de Reyes graben, and the Aguascalientes graben, respectively, to the SE, confirming their left lateral vector motion; afterwards TSL was displaced south by the right lateral strike slip Taxco-San Miguel de

  20. Dynamic computer model for the metallogenesis and tectonics of the Circum-North Pacific

    Science.gov (United States)

    Scotese, Christopher R.; Nokleberg, Warren J.; Monger, James W.H.; Norton, Ian O.; Parfenov, Leonid M.; Khanchuk, Alexander I.; Bundtzen, Thomas K.; Dawson, Kenneth M.; Eremin, Roman A.; Frolov, Yuri F.; Fujita, Kazuya; Goryachev, Nikolai A.; Pozdeev, Anany I.; Ratkin, Vladimir V.; Rodinov, Sergey M.; Rozenblum, Ilya S.; Scholl, David W.; Shpikerman, Vladimir I.; Sidorov, Anatoly A.; Stone, David B.

    2001-01-01

    The digital files on this report consist of a dynamic computer model of the metallogenesis and tectonics of the Circum-North Pacific, and background articles, figures, and maps. The tectonic part of the dynamic computer model is derived from a major analysis of the tectonic evolution of the Circum-North Pacific which is also contained in directory tectevol. The dynamic computer model and associated materials on this CD-ROM are part of a project on the major mineral deposits, metallogenesis, and tectonics of the Russian Far East, Alaska, and the Canadian Cordillera. The project provides critical information on bedrock geology and geophysics, tectonics, major metalliferous mineral resources, metallogenic patterns, and crustal origin and evolution of mineralizing systems for this region. The major scientific goals and benefits of the project are to: (1) provide a comprehensive international data base on the mineral resources of the region that is the first, extensive knowledge available in English; (2) provide major new interpretations of the origin and crustal evolution of mineralizing systems and their host rocks, thereby enabling enhanced, broad-scale tectonic reconstructions and interpretations; and (3) promote trade and scientific and technical exchanges between North America and Eastern Asia.

  1. Petrogenesis of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan: Provenance, tectonic, and climatic implications

    Science.gov (United States)

    Amireh, Belal S.

    2018-04-01

    Detrital framework modes of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan are determined employing the routine polarized light microscope. The lower part of this sequence constitutes a segment of the vast lower Paleozoic siliciclastic sheet flanking the northern Gondwana margin that was deposited over a regional unconformity truncating the outskirts of the East African orogen in the aftermath of the Neoproterozoic amalgamation of Gondwana. The research aims to evaluate the factors governing the detrital light mineral composition of this sandstone. The provenance terranes of the Arabian craton controlled by plate tectonics appear to be the primary factor in most of the formations, which could be either directly inferred employing Dickinson's compositional triangles or implied utilizing the petrographic data achieved and the available tectonic and geological data. The Arabian-Nubian Shield constitutes invariably the craton interior or the transitional provenance terrane within the NE Gondwana continental block that consistently supplied sandy detritus through northward-flowing braided rivers to all the lower Paleozoic formations. On the other hand, the Lower Cretaceous Series received siliciclastic debris, through braided-meandering rivers having same northward dispersal direction, additionally from the lower Paleozoic and lower-middle Mesozoic platform strata in the Arabian Craton. The formations making about 50% of the siliciclastic sequence represent a success for Dickinson's plate tectonics-provenance approach in attributing the detrital framework components primarily to the plate tectonic setting of the provenance terranes. However, even under this success, the varying effects of the other secondary sedimentological and paleoclimatological factors are important and could be crucial. The inapplicability of this approach to infer the appropriate provenance terranes of the remaining formations could be ascribed either to the

  2. Navigating Towards Digital Tectonic Tools

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due; Kirkegaard, Poul Henning

    2006-01-01

    The computer holds a great potential to break down the barriers between architecture and the technical aspects relating to architecture, thus supporting innovative architecture with an inner correspondence between form and technique. While the differing values in architecture and technique can seem...... a tectonic tool should encompass. Secondly the ability and validity of the model are shown by applying it to a case study of Jørn Utzon’s work on Minor Hall in Sydney Opera House - for the sake of exemplification the technical field focused on in this paper is room acoustics. Thirdly the relationship between...

  3. The Tectonic Potentials of Concrete

    DEFF Research Database (Denmark)

    Egholm Pedersen, Ole

    2013-01-01

    tectonic thinking. The ideas of German Theorist Gottfried Semper are presented as a strategy for describing form as a result of materials and technical matter. Furthermore the idea of poetic construction are presented. Set forth by the english / american theorist Kenneth Frampton, the idea is that poetic...... techniques are used in an iterative process, exploring boundaries rather than defining solutions. The Object Oriented design paradigm is found to support such development, allowing for structuring of code into ’classes’ such as: concept, geometry / material, and fabrication. Based on an analysis...

  4. Tectonic setting of the Seychelles, Mascarene and Amirante Plateaus in the Western Equatorial Indian Ocean

    International Nuclear Information System (INIS)

    Mart, Y.

    1988-01-01

    A system of marine plateaus occurs in the western equatorial Indian Ocean, forming an arcuate series of wide and shallow banks with small islands in places. The oceanic basins that surround the Seychelles - Amirante region are of various ages and reflect a complex seafloor spreading pattern. The structural analysis of the Seychelle - Amirante - Mascarene region reflects the tectonic evolution of the western equatorial Indian Ocean. It is suggested that due to the seafloor spreading during a tectonic stage, the Seychelles continental block drifted southwestwards to collide with the oceanic crust of the Mascarene Basin, forming an elongated folded structure at first, and then a subduction zone. The morphological similarity, the lithological variability and the different origin of the Seychelles Bank, the Mascarene Plateau and the Amirante Arc emphasizes the significant convergent effects of various plate tectonic processes on the development of marine plateaus

  5. Impacts and tectonism in Earth and moon history of the past 3800 million years

    Science.gov (United States)

    Stothers, Richard B.

    1992-01-01

    The moon's surface, unlike the Earth's, displays a comparatively clear record of its past bombardment history for the last 3800 Myr, the time since active lunar tectonism under the massive premare bombardment ended. From Baldwin's (1987) tabulation of estimated ages for a representative sample of large lunar craters younger than 3800 Ma, six major cratering episodes can be discerned. These six bombardment episodes, which must have affected the Earth too, appear to match in time the six major episodes of orogenic tectonism on Earth, despite typical resolution errors of +/- 100 Myr and the great uncertainties of the two chronologies. Since more highly resolved events during the Cenozoic and Mesozoic Eras suggest the same correlation, it is possible that large impacts have influenced plate tectonics and other aspects of geologic history, perhaps by triggering flood basalt eruptions.

  6. Sandbox Tectonics As A Teaching Tool

    Science.gov (United States)

    Delaughter, J.

    2005-12-01

    Students are typically introduced to the relative motions of plates and its effects either through text-based descriptions, paper models, or both. However, though students may learn to repeat the description of the effects, many students still do not show a deeper understanding of the process, as shown by examinations of students before and after an introductory geology course (DeLaughter et al, 1998). This is because students are rarely affected by the information on a visceral level; because their preconceptions are never challenged, they never internalize the information as part of their model of how the world works. However, when concepts such as plate motions and their effects are presented to students as part of a tangible, physical experiment, the ideas can have a much greater impact (Carey et al, 1989). The students use the new information to build more complete mental models while learning that such models can and must change in response to new information (Herbert, 2003). When such experiments are performed in a geology class, they afford the students a direct and visceral experience that may enhance the learning process. In this exercise for middle school students, the effects of relative plate motions on overlying sediments are modeled through a simple and inexpensive set of experiments using sand and newspaper. These experiments provide qualitatively the same results as those performed by geologists researching various aspects of faulting and folding (e.g., Horsfield, 1977, Domingez et al., 2000). A secondary benefit of these experiments is that when the students do not pull the papers perfectly the combination of effects can mimic real terrains (e.g., transpressional) very closely. This intrusion of methodological errors can also lead to a lively discussion of how science is done and what the results of an experiment imply, thereby providing a pedagogical benefit as well. Thus students can be shown the effects of relative plate motions in a direct and

  7. ON THE NOTION OF WELL-DEFINED TECTONIC REGIMES FOR TERRESTRIAL PLANETS IN THIS SOLAR SYSTEM AND OTHERS

    International Nuclear Information System (INIS)

    Lenardic, A.; Crowley, J. W.

    2012-01-01

    A model of coupled mantle convection and planetary tectonics is used to demonstrate that history dependence can outweigh the effects of a planet's energy content and material parameters in determining its tectonic state. The mantle convection-surface tectonics system allows multiple tectonic modes to exist for equivalent planetary parameter values. The tectonic mode of the system is then determined by its specific geologic and climatic history. This implies that models of tectonics and mantle convection will not be able to uniquely determine the tectonic mode of a terrestrial planet without the addition of historical data. Historical data exists, to variable degrees, for all four terrestrial planets within our solar system. For the Earth, the planet with the largest amount of observational data, debate does still remain regarding the geologic and climatic history of Earth's deep past but constraints are available. For planets in other solar systems, no such constraints exist at present. The existence of multiple tectonic modes, for equivalent parameter values, points to a reason why different groups have reached different conclusions regarding the tectonic state of extrasolar terrestrial planets larger than Earth ( s uper-Earths ) . The region of multiple stable solutions is predicted to widen in parameter space for more energetic mantle convection (as would be expected for larger planets). This means that different groups can find different solutions, all potentially viable and stable, using identical models and identical system parameter values. At a more practical level, the results argue that the question of whether extrasolar terrestrial planets will have plate tectonics is unanswerable and will remain so until the temporal evolution of extrasolar planets can be constrained.

  8. Late Mesozoic basin and range tectonics and related magmatism in Southeast China

    Directory of Open Access Journals (Sweden)

    Dezi Wang

    2012-03-01

    Full Text Available During the Late Mesozoic Middle Jurassic–Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic (Type I and intra-continental extensional basins (Type II. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tuffs and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous–Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geodynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc extensional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range

  9. The Okhotsk Plate and the Eurasia-North America plate boundary zone.

    Science.gov (United States)

    Hindle, David; Mackey, Kevin

    2014-05-01

    The Eurasia-North America plate boundary zone transitions from spreading at rates of ~ 25mm/yr in the North Atlantic, to compression at rates of ~ 5mm/yr in the region of the Okhotsk plate. Because the pole of rotation between Eurasia and North America lies more or less on their mutual boundary, there is a linear change in rate along the boundary, and regions near the euler pole are subject to extremely low deformation rates. The Okhotsk - Eurasia - North America triple junction lies slightly south of the rotation pole, placing the Okhotsk plate entirely in a weakly contractional setting. Regions near the triple junction absorb 1mm/yr contraction. Further south, towards the shoreline of the Okhotsk sea, up to 5 mm/yr contraction may be absorbed within the plate. How shortening is accommodated across the boundary remains an open question. One possibility is wholesale extrusion of the entire Okhotsk plate (or possibly its northwestern corner) along two plate boundary strike slip faults (Eurasia-Okhostk and North America Okhotsk). The problem with this model is that the seismic record does not presently clearly support it, with the largest events distributed both within the plate interior and on its boundaries. This may suggest that instead, the Okhotsk plate, and particularly its north-western end, consists of a series of smaller blocks which shuffle against each other, partially accommodating extrusion, but also permitting some internal deformation and change of shape of the Okhotsk plate itself. We present analyses of the very sparse seismic record from the region, as well as geometric-kinematic, tectonic models of the possible deformation of northwest Okhotsk to try to better understand the different probabilities of how this slowly deforming plate boundary zone is behaving.

  10. Seafloor Tectonic Fault Fabric and the Evolution of the Walvis Ridge-Rio Grande Rise Hot Spot Twins in the South Atlantic

    Science.gov (United States)

    Sager, W. W.; Engfer, D.; Thoram, S.; Koppers, A. A. P.; Class, C.

    2015-12-01

    Walvis Ridge (WR) and Rio Grande Rise (RGR) are Cretaceous-Cenozoic large igneous provinces (LIPs) formed by the Tristan-Gough hot spot interacting with the Mid-Atlantic Ridge (MAR). Although hot spot-ridge interaction has long been considered a primary factor controlling WR-RGR morphology, details are fuzzy owing to sparse geophysical data. We examined tectonic fabric revealed in satellite altimetry-derived gravity data to infer details about RGR-WR evolution. Plate tectonic reconstructions indicate that the main RGR plateau and large N-S plateau in the eastern WR erupted at the same point at ~90 Ma. Over the next ~8 Myr, these conjunct LIPs formed a "V" shape with a basin in between. Curved fracture zones within the basin imply the two LIPs formed around a microplate. The prominent rift in the middle of RGR formed nearly perpendicular to the RGR-WR intersection, suggesting an extensional microplate boundary. Hot spot eruptions continued at the MAR, emplacing the eastern WR and two main RGR plateaus until ~60 Ma. During this period, the N-S trending Eastern Rio Grande Rise (ERGR) was erupted along the MAR. Both the ERGR and WR formed bathymetric lineaments parallel to seafloor fault fabric and were likely connected. This resulted in WR seamounts with a "tadpole" shape, the head being small to medium seamounts on the WR track and the tails being low, spreading-fabric-parallel ridges extending up to ~150 km northward. Similar, small seamounts are found in the contemporaneous ERGR. Another critical observation is that the WR-RGR formed at a large crustal discontinuity (~700 km at anomaly C33, ~84 Ma) at one or more fracture zone offsets. By late Cenozoic time (anomaly C5, ~10 Ma), the offset was reduced by half while several new fracture zones formed at the junction between RGR and WR. This implies a connection between ridge reorganization and RGR-WR volcanism that may have resulted from the fracture zones becoming oblique to the spreading direction as Euler poles

  11. Automatic reconstruction of fault networks from seismicity catalogs including location uncertainty

    International Nuclear Information System (INIS)

    Wang, Y.

    2013-01-01

    Within the framework of plate tectonics, the deformation that arises from the relative movement of two plates occurs across discontinuities in the earth's crust, known as fault zones. Active fault zones are the causal locations of most earthquakes, which suddenly release tectonic stresses within a very short time. In return, fault zones slowly grow by accumulating slip due to such earthquakes by cumulated damage at their tips, and by branching or linking between pre-existing faults of various sizes. Over the last decades, a large amount of knowledge has been acquired concerning the overall phenomenology and mechanics of individual faults and earthquakes: A deep physical and mechanical understanding of the links and interactions between and among them is still missing, however. One of the main issues lies in our failure to always succeed in assigning an earthquake to its causative fault. Using approaches based in pattern-recognition theory, more insight into the relationship between earthquakes and fault structure can be gained by developing an automatic fault network reconstruction approach using high resolution earthquake data sets at largely different scales and by considering individual event uncertainties. This thesis introduces the Anisotropic Clustering of Location Uncertainty Distributions (ACLUD) method to reconstruct active fault networks on the basis of both earthquake locations and their estimated individual uncertainties. This method consists in fitting a given set of hypocenters with an increasing amount of finite planes until the residuals of the fit compare with location uncertainties. After a massive search through the large solution space of possible reconstructed fault networks, six different validation procedures are applied in order to select the corresponding best fault network. Two of the validation steps (cross-validation and Bayesian Information Criterion (BIC)) process the fit residuals, while the four others look for solutions that

  12. DELP Symposium: Tectonics of eastern Asia and western Pacific Continental Margin

    Science.gov (United States)

    Eastern Asia and the western Pacific make up a broad region of active plate tectonic interaction. The area is a natural laboratory for studying the processes involved in the origin and evolution of volcanic island arcs, marginal basins, accretionary prisims, oceanic trenches, accreted terranes, ophiolite emplacement, and intracontinental deformation. Many of our working concepts of plate tectonics and intraplate deformation were developed in this region, even though details of the geology and geophysics there must be considered of a reconnaissance nature.During the past few years researchers have accumulated a vast amount of new and detailed information and have developed a better understanding of the processes that have shaped the tectonic elements in this region. To bring together scientists from many disciplines and to present the wide range of new data and ideas that offer a broader perspective on the interrelations of geological, geochemical, geophysical and geodetic studies, the symposium Tectonics of Eastern Asia and Western Pacific Continental Margin was held December 13-16, 1988, at the Tokyo Institute of Technology in Japan, under the auspicies of DELP (Dynamics and Evolution of the Lithosphere Project).

  13. Plain formation on Mercury: tectonic implications

    International Nuclear Information System (INIS)

    Thomas, P.

    1980-01-01

    Four major plain units, plus intermediates, are distinguished on Mercury. The chronologic relationships between these plains indicate that plains formation was a permanent process on Mercury. Their location and morphology seem to indicate a possible volcanic origin for these plains. The relationships between tectonism and volcanism seems to indicate the global contraction is not the only tectonic process on Mercury. (Auth.)

  14. Framework for Tectonic Thinking, a Conceptual Approach

    DEFF Research Database (Denmark)

    Garritzmann, Udo

    2017-01-01

    This research paper is a contribution to the field of architectural design theory in the area of tectonics. From the designer’s point of view, it will develop an overarching conceptual framework for tectonic thinking (FTT), which will serve as a tool for the comparative analysis and interpretation...

  15. Global Paleobathymetry Reconstruction with Realistic Shelf-Slope and Sediment Wedge

    Science.gov (United States)

    Goswami, A.; Hinnov, L. A.; Gnanadesikan, A.; Olson, P.

    2013-12-01

    We present paleo-ocean bathymetry reconstructions in a 0.1°x0.1° resolution, using simple geophysical models (Plate Model Equation for oceanic lithosphere), published ages of the ocean floor (Müller et al. 2008), and modern world sediment thickness data (Divins 2003). The motivation is to create realistic paleobathymetry to understand the effect of ocean floor roughness on tides and heat transport in paleoclimate simulations. The values for the parameters in the Plate Model Equation are deduced from Crosby et al. (2006) and are used together with ocean floor age to model Depth to Basement. On top of the Depth to Basement, we added an isostatically adjusted multilayer sediment layer, as indicated from sediment thickness data of the modern oceans and marginal seas (Divins 2003). We also created another version of the sediment layer from the Müller et al. dataset. The Depth to Basement with the appropriate sediment layer together represent a realistic paleobathymetry. A Sediment Wedge was modeled to complement the reconstructed paleobathymetry by extending it to the coastlines. In this process we added a modeled Continental Shelf and Continental Slope to match the extent of the reconstructed paleobathymetry. The Sediment Wedge was prepared by studying the modern ocean where a complete history of seafloor spreading is preserved (north, south and central Atlantic Ocean, Southern Ocean between Australia-Antarctica, and the Pacific Ocean off the west coast of South America). The model takes into account the modern continental shelf-slope structure (as evident from ETOPO1/ETOPO5), tectonic margin type (active vs. passive margin) and age of the latest tectonic activity (USGS & CGMW). Once the complete ocean bathymetry is modeled, we combine it with PALEOMAP (Scotese, 2011) continental reconstructions to produce global paleoworld elevation-bathymetry maps. Modern time (00 Ma) was assumed as a test case. Using the above-described methodology we reconstructed modern ocean

  16. Cenozoic tectonic and climatic events in southern Iberian Peninsula: Implications for the evolutionary history of freshwater fish of the genus Squalius (Actinopterygii, Cyprinidae).

    Science.gov (United States)

    Perea, Silvia; Cobo-Simon, Marta; Doadrio, Ignacio

    2016-04-01

    Southern Iberian freshwater ecosystems located at the border between the European and African plates represent a tectonically complex region spanning several geological ages, from the uplifting of the Betic Mountains in the Serravalian-Tortonian periods to the present. This area has also been subjected to the influence of changing climate conditions since the Middle-Upper Pliocene when seasonal weather patterns were established. Consequently, the ichthyofauna of southern Iberia is an interesting model system for analyzing the influence of Cenozoic tectonic and climatic events on its evolutionary history. The cyprinids Squalius malacitanus and Squalius pyrenaicus are allopatrically distributed in southern Iberia and their evolutionary history may have been defined by Cenozoic tectonic and climatic events. We analyzed MT-CYB (510 specimens) and RAG1 (140 specimens) genes of both species to reconstruct phylogenetic relationships and to estimate divergence times and ancestral distribution ranges of the species and their populations. We also assessed their levels of genetic structure and diversity as well as the amount of gene flow between populations. To investigate recent paleogeographical and climatic factors in southern Iberia, we modeled changes-through-time in sea level from the LGM to the present. Phylogenetic, geographic and population structure analyses revealed two well-supported species (S. malacitanus and S. pyrenaicus) in southern Iberia and two subclades (Atlantic and Mediterranean) within S. malacitanus. The origin of S. malacitanus and the separation of its Atlantic and Mediterranean populations occurred during the Serravalian-Tortonian and Miocene-Pliocene periods, respectively. These divergence events occurred in the Middle Pliocene and Pleistocene in S. pyrenaicus. In both species, Atlantic basins possessed populations with higher genetic diversity than Mediterranean, which may be explained by the Janda Lagoon. The isolation of S. malacitanus was

  17. Tectonic signatures on active margins

    Science.gov (United States)

    Hogarth, Leah Jolynn

    High-resolution Compressed High-Intensity Radar Pulse (CHIRP) surveys offshore of La Jolla in southern California and the Eel River in northern California provide the opportunity to investigate the role of tectonics in the formation of stratigraphic architecture and margin morphology. Both study sites are characterized by shore-parallel tectonic deformation, which is largely observed in the structure of the prominent angular unconformity interpreted as the transgressive surface. Based on stratal geometry and acoustic character, we identify three sedimentary sequences offshore of La Jolla: an acoustically laminated estuarine unit deposited during early transgression, an infilling or "healing-phase" unit formed during the transgression, and an upper transparent unit. The estuarine unit is confined to the canyon edges in what may have been embayments during the last sea-level rise. The healing-phase unit appears to infill rough areas on the transgressive surface that may be related to relict fault structures. The upper transparent unit is largely controlled by long-wavelength tectonic deformation due to the Rose Canyon Fault. This unit is also characterized by a mid-shelf (˜40 m water depth) thickness high, which is likely a result of hydrodynamic forces and sediment grain size. On the Eel margin, we observe three distinct facies: a seaward-thinning unit truncated by the transgressive surface, a healing-phase unit confined to the edges of a broad structural high, and a highly laminated upper unit. The seaward-thinning wedge of sediment below the transgressive surface is marked by a number of channels that we interpret as distributary channels based on their morphology. Regional divergence of the sequence boundary and transgressive surface with up to ˜8 m of sediment preserved across the interfluves suggests the formation of subaerial accommodation during the lowstand. The healing-phase, much like that in southern California, appears to infill rough areas in the

  18. Overview of the Education and Public Outreach (EPO) program of the Caltech Tectonics Observatory

    Science.gov (United States)

    Kovalenko, L.; Jain, K.; Maloney, J.

    2009-12-01

    The Caltech Tectonics Observatory (TO) is an interdisciplinary center, focused on geological processes occurring at the boundaries of Earth's tectonic plates (http://www.tectonics.caltech.edu). Over the past year, the TO has made a major effort to develop an Education and Public Outreach (EPO) program. Our goals are to (1) stimulate the interest of students and the general public in Earth Sciences, particularly in the study of tectonic processes, (2) inform and educate the general public about science in the context of TO discoveries and advancements, and (3) provide opportunities for graduate students, postdocs, and faculty to do outreach in the local K-12 schools. We have hosted local high school students and teachers to provide them with research experience (as part of Caltech’s “Summer Research Connection”); participated in teacher training workshops (organized by the local school district); hosted tours for local elementary school students; and brought hands-on activities into local elementary and middle school classrooms, science clubs, and science nights. We have also led local school students and teachers on geology field trips through nearby parks. In addition, we have developed education modules for undergraduate classes (as part of MARGINS program), and have written educational web articles on TO research (http://www.tectonics.caltech.edu/outreach). The presentation will give an overview of these activities and their impact on our educational program.

  19. Strain transformation between tectonic extrusion and crustal thickening in the growth of the Tibetan Plateau

    Science.gov (United States)

    Liu, M.; Li, Y.; Sun, Y.; Shen, X.

    2017-12-01

    The Indo-Eurasian continental collision since 50 Ma has thickened the crust to raise the Himalayan-Tibetan Plateau and driven lateral extrusion of Asian lithospheric blocks to affect Cenozoic tectonics in central and east Asia. The relative roles of crustal thickening and tectonic extrusion, and the strain partitioning between them over time and space, remain controversial. We have analyzed the strain rates using GPS velocities, and correlated the results with vertical motion derived from precise leveling. We found that tectonic extrusion largely transforms to crustal thickening near the margins of the Tibetan Plateau. Near the NW margin of the Tibetan Plateau, the shear stain transforms to compressive strain, consistent with neotectonic studies that indicate crustal shortening and uplift. Around the SE margin, shear stain largely terminates in the southern Yunnan province of China. The present-day crustal motion in SE Tibetan Plateau can be well explained by gravitational spreading without invoking plate-edge push as envisioned in the tectonic extrusion model. Using data collected from local seismic arrays, we derived receiver functions to image the lithospheric structures across the Tibetan Plateau and the Alashan block to its north and the Ordos block to its east. Our results indicate that the mantle lithosphere of these bounding Asian blocks has not been reworked by Tibetan tectonics; instead they have acted as restrictive walls to the growing Tibetan Plateau. Our finite element modeling shows that crustal deformation along the margins of the Tibetan Plateau are consistent with the notion that the east- and southeastward extrusion of the Tibetan lithosphere is largely confined to the Tibetan Plateau because of the restrictive bounding blocks of the Asian lithosphere. Thus the tectonic impact of the Indo-Eurasian collision on the Cenozoic Asian tectonics may not be as extensive as previously thought.

  20. The role of farfield tectonic stress in oceanic intraplate deformation, Gulf of Alaska

    Science.gov (United States)

    Reece, Robert S.; Gulick, Sean P. S.; Christesen, Gail L.; Horton, Brian K.; VanAvendonk, Harm J.; Barth, Ginger

    2013-01-01

    An integration of geophysical data from the Pacific Plate reveals plate bending anomalies, massive intraplate shearing and deformation, and a lack of oceanic crust magnetic lineaments in different regions across the Gulf of Alaska. We argue that farfield stress from the Yakutat Terrane collision with North America is the major driver for these unusual features. Similar plate motion vectors indicate that the Pacific plate and Yakutat Terrane are largely coupled along their boundary, the Transition Fault, with minimal translation. Our study shows that the Pacific Plate subduction angle shallows toward the Yakutat Terrane and supports the theory that the Pacific Plate and Yakutat Terranemaintain coupling along the subducted region of the Transition Fault. We argue that the outboard transfer of collisional stress to the Pacific Plate could have resulted in significant strain in the NE corner of the Pacific Plate, which created pathways for igneous sill formation just above the Pacific Plate crust in the Surveyor Fan. A shift in Pacific Plate motion during the late Miocene altered the Yakutat collision with North America, changing the stress transfer regime and potentially terminating associated strain in the NE corner of the Pacific Plate. The collision further intensified as the thickest portion of the Yakutat Terrane began to subduct during the Pleistocene, possibly providing the impetus for the creation of the Gulf of Alaska Shear Zone, a>200 km zone of intraplate strike-slip faults that extend from the Transition Fault out into the Pacific Plate. This study highlights the importance of farfield stress from complex tectonic regimes in consideration of large-scale oceanic intraplate deformation.

  1. Tectonically asymmetric Earth: From net rotation to polarized westward drift of the lithosphere

    Directory of Open Access Journals (Sweden)

    Carlo Doglioni

    2015-05-01

    Full Text Available The possibility of a net rotation of the lithosphere with respect to the mantle is generally overlooked since it depends on the adopted mantle reference frames, which are arbitrary. We review the geological and geophysical signatures of plate boundaries, and show that they are markedly asymmetric worldwide. Then we compare available reference frames of plate motions relative to the mantle and discuss which is at best able to fit global tectonic data. Different assumptions about the depths of hotspot sources (below or within the asthenosphere, which decouples the lithosphere from the deep mantle predict different rates of net rotation of the lithosphere relative to the mantle. The widely used no-net-rotation (NNR reference frame, and low (1°/Ma net rotation (shallow hotspots source, all plates, albeit at different velocity, move westerly along a curved trajectory, with a tectonic equator tilted about 30° relative to the geographic equator. This is consistent with the observed global tectonic asymmetries.

  2. Syn-kinematic palaeogeographic evolution of the West European Platform: correlation with Alpine plate collision and foreland deformation

    NARCIS (Netherlands)

    Sissingh, W.

    Sequence stratigraphic correlations indicate that intermittent changes of the kinematic far-field stress-field regimes, and the associated geodynamic re-organisations at the plate-tectonic contacts of the African, Apulian, Iberian and European plates, affected the Tertiary palaeogeographic evolution

  3. Radiation shielding plate

    International Nuclear Information System (INIS)

    Kobayashi, Torakichi; Sugawara, Takeo.

    1983-01-01

    Purpose: To reduce the weight and stabilize the configuration of a radiation shielding plate which is used in close contact with an object to be irradiated with radiation rays. Constitution: The radiation shielding plate comprises a substrate made of lead glass and a metallic lead coating on the surface of the substrate by means of plating, vapor deposition or the like. Apertures for permeating radiation rays are formed to the radiation shielding plate. Since the shielding plate is based on a lead glass plate, a sufficient mechanical strength can be obtained with a thinner structure as compared with the conventional plate made of metallic lead. Accordingly, if the shielding plate is disposed on a soft object to be irradiated with radiation rays, the object and the plate itself less deform to obtain a radiation irradiation pattern with distinct edges. (Moriyama, K.)

  4. Metallogenic relationships to tectonic evolution - the Lachlan Orogen, Australia

    Science.gov (United States)

    Bierlein, Frank P.; Gray, David R.; Foster, David A.

    2002-08-01

    Placing ore formation within the overall tectonic framework of an evolving orogenic system provides important constraints for the development of plate tectonic models. Distinct metallogenic associations across the Palaeozoic Lachlan Orogen in SE Australia are interpreted to be the manifestation of interactions between several microplates and three accretionary complexes in an oceanic back-arc setting. In the Ordovician, significant orogenic gold deposits formed within a developing accretionary wedge along the Pacific margin of Gondwana. At the same time, major porphyry Cu-Au systems formed in an oceanic island arc outboard of an evolved magmatic arc that, in turn, gave rise to granite-related Sn-W deposits in the Early Silurian. During the ongoing evolution of the orogen in the Late Silurian to Early Devonian, sediment-hosted Cu-Au and Pb-Zn deposits formed in short-lived intra-arc basins, whereas a developing fore-arc system provided the conditions for the formation of several volcanogenic massive sulphide deposits. Inversion of these basins and accretion to the Australian continental margin triggered another pulse of orogenic gold mineralisation during the final consolidation of the orogenic belt in the Middle to Late Devonian.

  5. Theory of denudation tectonics and practice in prospecting. Pt.1

    International Nuclear Information System (INIS)

    Tong Hangshou

    1994-01-01

    The theory of denudation tectonics--earth science frontiers--upsurged in the 1980's of the century and a great mass fervor of its research has spread to the uranium geology. For the studying and applying the theory of denudation tectonics and on the invitation of the Editorial Department of 'Uranium Geology', this paper has been written and will be published in several issues with the following contents accordingly: (1) New progress in the research on denudation tectonics in China; (2) The evolution of denudation tectonics' concept and layer zoning of the Earth; (3) The fundamental implication of the denudation tectonics and relevant tectonic terminology; (4) Discussion on dynamics of the formation of denudation tectonics; (5) Definition and discrimination of denudation tectonics; (6) Research method of denudation tectonics; (7) Ore control theory of denudation tectonics and prospecting; (8) Outlook on the research of denudation tectonics

  6. Motion of the Rivera plate since 10 Ma relative to the Pacific and North American plates and the mantle

    Science.gov (United States)

    DeMets, Charles; Traylen, Stephen

    2000-03-01

    To better understand the influence of Rivera plate kinematics on the geodynamic evolution of western Mexico, we use more than 1400 crossings of seafloor spreading magnetic lineations along the Pacific-Rivera rise and northern Mathematician ridge to solve for rotations of the Rivera plate relative to the underlying mantle and the Pacific and North American plates at 14 times since 9.9 Ma. Our comparison of magnetic anomaly crossings from the undeformed Pacific plate to their counterparts on the Rivera plate indicates that significant areas of the Rivera plate have deformed since 9.9 Ma. Dextral shear along the southern edge of the plate from 3.3-2.2 Ma during a regional plate boundary reorganization deformed the Rivera plate farther into its interior than previously recognized. In addition, seafloor located north of two rupture zones within the Rivera plate sutured to North America after 1.5 Ma. Anomaly crossings from these two deformed regions thus cannot be used to reconstruct motion of the Rivera plate. Finite rotations that best reconstruct Pacific plate anomaly crossings onto their undeformed counterparts on the Rivera plate yield stage spreading rates that decrease gradually by 10% between 10 and 3.6 Ma, decrease rapidly by 20% after ˜3.6 Ma, and recover after 1 Ma. The slowdown in Pacific-Rivera seafloor spreading at 3.6 Ma coincided with the onset of dextral shear across the then-incipient southern boundary of the Rivera plate with the Pacific plate. The available evidence indicates that the Rivera plate has been an independent microplate since at least 10 Ma, contrary to published assertions that it fragmented from the Cocos plate at ˜5 Ma. Motion of the Rivera plate relative to North America has changed significantly since 10 Ma, in concert with significant changes in Pacific-Rivera motion. A significant and robust feature of Rivera-North America motion not previously recognized is the cessation of margin-normal convergence and thus subduction from 2

  7. Crustal structure and tectonic deformation of the southern Ecuadorian margin

    Science.gov (United States)

    Calahorrano, Alcinoe; Collot, Jean-Yves; Sage, Françoise; Ranero, César R.

    2010-05-01

    Multichannel seismic lines acquired during the SISTEUR cruise (2000) provide new constraints on the structure and deformation of the subduction zone at the southern Ecuadorian margin, from the deformation front to the continental shelf of the Gulf of Guayaquil. The pre-stack depth migrated images allows to characterise the main structures of the downgoing and overriding plates and to map the margin stratigraphy in order to propose a chronology of the deformation, by means of integrating commercial well data and industry seismic lines located in the gulf area. The 100-km-long seismic lines show the oceanic Nazca plate underthrusting the South American plate, as well as the subduction channel and inter-plate contact from the deformation front to about 90 km landward and ~20 km depth. Based on seismic structure we identify four upper-plate units, consisting of basement and overlaying sedimentary sequences A, B and C. The sedimentary cover varies along the margin, being few hundreds of meters thick in the lower and middle slope, and ~2-3 km thick in the upper slope. Exceptionally, a ~10-km -thick basin, here named Banco Peru basin, is located on the upper slope at the southernmost part of the gulf. This basin seems to be the first evidence of the Gulf of Guayaquil opening resulting from the NE escaping of the North Andean Block. Below the continental shelf, thick sedimentary basins of ~6 to 8 km occupy most of the gulf area. Tectonic deformation across most of the upper-plate is dominated by extensional regime, locally disturbed by diapirism. Compression evidences are restricted to the deformation front and surrounding areas. Well data calibrating the seismic profiles indicate that an important portion of the total thickness of the sedimentary coverage of the overriding plate are Miocene or older. The data indicate the extensional deformation resulting from the NE motion of the North Andean Block and the opening of the Gulf of Guayaquil, evolves progressively in age

  8. Euro-African MAGSAT anomaly-tectonic observations

    Science.gov (United States)

    Hinze, W. J.; Olivier, R.; Vonfrese, R. R. B.

    1985-01-01

    Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.

  9. Climate Reconstructions

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Paleoclimatology Program archives reconstructions of past climatic conditions derived from paleoclimate proxies, in addition to the Program's large holdings...

  10. The Jurassic of Denmark and Greenland: key elements in the reconstruction of the North Atlantic Jurassic rift system

    Directory of Open Access Journals (Sweden)

    Surlyk, Finn

    2003-10-01

    Full Text Available The Jurassic succession of Denmark is largely confined to the subsurface with the exception of exposures on the island of Bornholm in the Baltic Sea. In East Greenland, in contrast, the Jurassic is extensively exposed. Comparison of basin evolution in the two regions, which now occur on two separate plates, thus relies on highly different datasets. It is possible nevertheless to construct an integrated picture allowing testing of hypotheses concerning basin evolution, regional uplift, onset and climax of rifting, relative versus eustatic sea-level changes and sequence stratigraphic subdivision and correlation. On a smaller scale, it is possible to compare the signatures of sequence stratigraphic surfaces as seen on well logs, in cores and at outcrop and of sequences recognised and defined on the basis of very different data types. Breakdown of the successions into tectonostratigraphic megasequences highlights the high degree of similarity in overall basin evolution and tectonic style. An important difference, however, lies in the timing. Major events such as late Early - Middle Jurassic uplift, followed by onset of rifting, basin reorganisation and rift climax were delayed in East Greenland relative to the Danish region. This has important implications both for regional reconstructions of the rift system and for the understanding and testing of classical sequence stratigraphic concepts involving eustatic versus tectonic controls of basin evolution and stratigraphy.

  11. Mapping Tectonic Stress Using Earthquakes

    International Nuclear Information System (INIS)

    Arnold, Richard; Townend, John; Vignaux, Tony

    2005-01-01

    An earthquakes occurs when the forces acting on a fault overcome its intrinsic strength and cause it to slip abruptly. Understanding more specifically why earthquakes occur at particular locations and times is complicated because in many cases we do not know what these forces actually are, or indeed what processes ultimately trigger slip. The goal of this study is to develop, test, and implement a Bayesian method of reliably determining tectonic stresses using the most abundant stress gauges available - earthquakes themselves.Existing algorithms produce reasonable estimates of the principal stress directions, but yield unreliable error bounds as a consequence of the generally weak constraint on stress imposed by any single earthquake, observational errors, and an unavoidable ambiguity between the fault normal and the slip vector.A statistical treatment of the problem can take into account observational errors, combine data from multiple earthquakes in a consistent manner, and provide realistic error bounds on the estimated principal stress directions.We have developed a realistic physical framework for modelling multiple earthquakes and show how the strong physical and geometrical constraints present in this problem allow inference to be made about the orientation of the principal axes of stress in the earth's crust

  12. The Tectonic Potentials of Concrete

    DEFF Research Database (Denmark)

    Egholm Pedersen, Ole

    2013-01-01

    Contemporary techniques for concrete casting in an architectural context are challenged by demands of increased individualization in our built environment, reductions in the use of resources and waste generation. In recent years, new production technologies and strategies that break with the indu......Contemporary techniques for concrete casting in an architectural context are challenged by demands of increased individualization in our built environment, reductions in the use of resources and waste generation. In recent years, new production technologies and strategies that break...... with the industrial paradigm of standardization, have been put forward. This development is carried forward by computers and digital fabrication, but has yet to find its way into the production of building components. With regards to concrete casting, however, existing research do offer advancement towards...... an increased customisation of casting moulds. The hypothesis of this research is that the techniques used in this research do not fully address the tectonic potentials of concrete which gives rise to the primary research question: Is it possible to enhance existing or develop new concrete casting techniques...

  13. Create Your Plate

    Medline Plus

    Full Text Available ... foods you want, but changes the portion sizes so you are getting larger portions of non-starchy ... plate. Then on one side, cut it again so you will have three sections on your plate. ...

  14. Create Your Plate

    Medline Plus

    Full Text Available ... of the differences in types of vegetables. When creating your plate at home, remember that half of ... effective for both managing diabetes and losing weight. Creating your plate lets you still choose the foods ...

  15. Create Your Plate

    Medline Plus

    Full Text Available ... Index Low-Calorie Sweeteners Sugar and Desserts Fitness Exercise & Type 1 Diabetes Get Started Safely Get And ... Plate Create Your Plate is a simple and effective way to manage your blood glucose levels and ...

  16. Create Your Plate

    Medline Plus

    Full Text Available ... Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with ... Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart-Healthy ...

  17. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal ... Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook ...

  18. Reconstruction of 3D PIV data in complicated experimental arrangements

    Directory of Open Access Journals (Sweden)

    Pavlík David

    2017-01-01

    Full Text Available In this paper a three-dimensional reconstruction of flow field behind flat plate representing a wing is presented. The reconstruction is always performed for pair of 2D vector maps obtained by 3D PIV with two cameras which record measurement area from different locations. Three-dimensional reconstruction can be obtained in various ways. This paper summarizes two: the reconstruction based on the known correspondences and the reconstruction based on the knowledge of intrinsic and extrinsic parameters of cameras. The methods can be used in the cases when it is impossible to use a calibration pattern or when reconstruction by commercial software fails.

  19. The importance of continent tectonic study

    International Nuclear Information System (INIS)

    Carneiro, C.D.R.

    1992-01-01

    Some aspects of tectonic study in the continents are presented, including the use of methods that measure the isotope radioactive disintegration of some elements presents in rocks and the mineral distribution in African and South American continents. (author)

  20. Towards a Tectonic Sustainable Building Practice

    DEFF Research Database (Denmark)

    Bech-Danielsen, Claus

    and environmental problems? The objective of the project is to analyse and develop the tectonic practice based on case studies, in relation to: • Cultural anchoring and identity creation • Building culture and creative processes • Sustainability, lifecycle and resource management The research project is divided...... into a main project and various subprojects, respectively, two levels that mutually feed each other.The main project, which constitutes the general level, seeks to identify a coherent strategy towards a new tectonically sustainable building culture.The subprojects look at partial issues and go into specific......Can a tectonic building practice be strengthened through new creation processes, where resources are used more purposefully, deliberately and systematically? Which new measures are necessary if we are to develop a strong tectonic building practice with due consideration for increasing climate...

  1. Tomographic Imaging of the Lesser Antilles Subducted Slab and its Significance for Estimating the Age and Amount of Eastward Motion of the Overriding Caribbean Plate

    Science.gov (United States)

    Mann, P.; Chen, Y. W.; Wu, J.; Suppe, J.

    2017-12-01

    The idea of a Pacific-derived and eastward-transported Caribbean and Scotia plates was first proposed by J. Tuzo Wilson in 1966. Wilson proposed that the motion of these two, small plates was analogous to "ice rafting" observed on frozen lakes and oceans when a narrow ( 50 m) strip of ice is forced over a lower plate of ice. In the Caribbean the upper plate corresponds to the 750 km-long, north-south length of the Lesser Antilles volcanic arc ranging in thickness from 20-30 km while its subducting plate is Atlantic Cretaceous oceanic crust of 8-10 km thickness and subducting at an angle of 45º to a depth of 300 km into the mantle. We estimated the length of the Lesser Antilles slab from MIT P-wave global tomography (MITP08; Li et al., 2008) and compared to published transects from Utrecht UUP-07 global tomography (van Bentham et al., 2013). The measured slab lengths vary from 1550 km (Utrecht) to 1250 km (MIT). We then unfolded both slabs to the Earth's surface, and used GPlates to restore the leading edge of the Caribbean plate at the time of the Lesser Antilles slab's initial subduction. The Middle Eocene (49 Ma) reconstruction realigns the proto-Lesser Antilles arc and leading edge of the Caribbean plate in a continuous arc with older arc rocks in Cuba. During this Middle Eocene period of abrupt tectonic transition, the Cuban arc segment was terminated on its northeastward path by collision with the Bahama carbonate platform with subsequent reorientation onto its present, east-west path into the central Atlantic Ocean from 49-0 Ma. This collision/plate reorientation event is independently recorded by: 1) a poorly defined Greater Antilles slab seen on tomography that is aligned with the Cuban arc; 2) identical initiation ages of 49 Ma for the Cayman trough pull-apart and the Lesser Antilles slab; and 3) similarity in lengths for the length of the subducted, Lesser Antilles slab ( 1250-1550 km) and the length of the Cayman trough pull-apart basin ( 1100 km). East

  2. ON TECTONIC PROBLEMS OF THE OKINAWA TROUGH

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Okinawa Trough is a very active tectonic zone at the margin of the Northwest Pacific and is typical of back-arc rifting at the young stage of tectonic evolution. Many scientists from Japan, China, Germany, France, the U.S.A. and Russia have done a lot of geologic and geophysical investigations there. It is well known that the Okinawa Trough is an active back-arc rift with extremely high heat flow, very strong hydrothermal circulation, strong volcanic and magmatic activity, frequent earthquakes, rapid subsidence and rifting, well-developed fault and central graben. But up to now, there are still some important tectonic problems about the Okinawa Trough that require clarification on some aspects such as the type of its crust, its forming time, its tectonic evolution, the distribution of its central grabens, the relationship between its high heat flow and tectonic activity. Based on the data obtained from seismic survey, geomagnetic and gravity measurements, submarine sampling and heat flow measurements in the last 15 years, the author discusses the following tectonic problems about the Okinawa Trough: (1) If the Okinawa Trough develops oceanic crust or not. (2) Is the South Okinawa Trough tectonically more active than the North Okinawa Trough with shallower water and few investigation data on it. (3) The formation time of the Okinawa Trough and its tectonic evolution. The Okinawa Trough has a very thin continental crust. Up to now, there is no evidence of oceanic crust in the Okinawa Trough. The North, Middle and South Okinawa Trough are all very strongly active areas. From 6 Ma B.P., the Okinawa Trough began to form. Since 2 Ma, the Okinawa Trough has been very active.

  3. ON TECTONIC PROBLEMS OF THE OKINAWA TROUGH

    Institute of Scientific and Technical Information of China (English)

    李乃胜

    2001-01-01

    The Okinawa Trough is a very active tectonic zone at the margin of the Northwest Pacific and is typical of back-arc rifting at the young stage of tectonic evolution. Many scientists from Japan,China, Germany, France, the U. S.A. and Russia have done a lot of geologic and geophysical investigations there. It is well known that the Okinawa Trough is an active back-arc rift with extremely high heat flow, very strong hydrothermal circulation, strong volcanic and magmatic activity, frequent earthquakes,rapid subsidence and rifting, well-developed fault and central graben. But up to now, there are still some important tectonic problems about the Okinawa Trough that require clarification on some aspects such as the type of its crust, its forming time, its tectonic evolution, the distribution of its central grabens, the relationship between its high heat flow and tectonic activity. Based on the data obtained from seismic sur-vey, geomagnetic and gravity measurements, submarine sampling and heat flow measurements in the last 15 years, the author discusses the following tectonic problems about the Okinawa Trough: (1) If the Okinawa Trough develops oceanic crust or not. (2) Is the South Okinawa Trough tectonically more active than the North Okinawa Trough with shallower water and few investigation data on it. (3) The formation time of the Okinawa Trough and its tectonic evolution. The Okinawa Trough has a very thin continental crust. Up to now, there is no evidence of oceanic crust in the Okinawa Trough. The North, Middle and South Okinawa Trough are all very strongly active areas. From 6 Ma B.P. , the Okinawa Trough began to form. Since 2 Ma, the Okinawa Trough has been very active.

  4. Radon emanation in tectonically active areas

    International Nuclear Information System (INIS)

    King, C.Y.

    1980-01-01

    Subsurface radon emanation has been continuously monitored for up to three years by the Track Etch method in shallow dry holes at more than 60 sites along several tectonic faults in central California and at 9 sites near the Kilauea volcano in Hawaii. The measured emanation in these tectonically active areas shows large long-term variations that may be related mainly to crustal strain changes

  5. Validation of the Gate simulation platform in single photon emission computed tomography and application to the development of a complete 3-dimensional reconstruction algorithm; Validation de la plate-forme de simulation GATE en tomographie a emission monophotonique et application au developpement d'un algorithme de reconstruction 3D complete

    Energy Technology Data Exchange (ETDEWEB)

    Lazaro, D

    2003-10-01

    Monte Carlo simulations are currently considered in nuclear medical imaging as a powerful tool to design and optimize detection systems, and also to assess reconstruction algorithms and correction methods for degrading physical effects. Among the many simulators available, none of them is considered as a standard in nuclear medical imaging: this fact has motivated the development of a new generic Monte Carlo simulation platform (GATE), based on GEANT4 and dedicated to SPECT/PET (single photo emission computed tomography / positron emission tomography) applications. We participated during this thesis to the development of the GATE platform within an international collaboration. GATE was validated in SPECT by modeling two gamma cameras characterized by a different geometry, one dedicated to small animal imaging and the other used in a clinical context (Philips AXIS), and by comparing the results obtained with GATE simulations with experimental data. The simulation results reproduce accurately the measured performances of both gamma cameras. The GATE platform was then used to develop a new 3-dimensional reconstruction method: F3DMC (fully 3-dimension Monte-Carlo) which consists in computing with Monte Carlo simulation the transition matrix used in an iterative reconstruction algorithm (in this case, ML-EM), including within the transition matrix the main physical effects degrading the image formation process. The results obtained with the F3DMC method were compared to the results obtained with three other more conventional methods (FBP, MLEM, MLEMC) for different phantoms. The results of this study show that F3DMC allows to improve the reconstruction efficiency, the spatial resolution and the signal to noise ratio with a satisfactory quantification of the images. These results should be confirmed by performing clinical experiments and open the door to a unified reconstruction method, which could be applied in SPECT but also in PET. (author)

  6. The revised tectonic history of Tharsis

    Science.gov (United States)

    Bouley, Sylvain; Baratoux, David; Paulien, Nicolas; Missenard, Yves; Saint-Bézar, Bertrand

    2018-04-01

    Constraining the timing of the emplacement of the volcano-tectonic province of Tharsis is critical to understanding the evolution of mantle, surface environment and climate of Mars. The growth of Tharsis had exerted stresses on the lithosphere, which were responsible for tectonic deformation, previously mapped as radial or concentric faults. Insights into the emplacement history of Tharsis may be gained from an analysis of the characteristics and ages of these tectonic features. The number, total length, linear density of extensional or compressional faults in the Tharsis region and deformation rates are reported for each of the following 6 stages: Early and Middle Noachian (stage 1); Late Noachian (stage 2); Early Hesperian (stage 3); Late Hesperian (stage 4), Early Amazonian (stage 5) and Middle Amazonian to Late Amazonian (stage 6). 8571 Tharsis-related tectonic features (radial or concentric to the center of Tharsis) were assigned to one of these periods of time based on their relationship with stratigraphic units defined in the most recent geological map. Intense faulting at Tempe Terra, Claritas and Coracis Fossae and Thaumasia Planum confirms that tectonic deformation started during the Noachian. However, we report a peak in both compressive and extensive rates of deformation during the Early Hesperian whereas the quantitative indicators for compressional and extensional tectonics vary within less than one order of magnitude from the Late Noachian to the Late Hesperian. These observations indicate a protracted growth of Tharsis during the first quarter of Mars evolution and declining from 3 Gyrs ago.

  7. Tectonics earthquake distribution pattern analysis based focal mechanisms (Case study Sulawesi Island, 1993–2012)

    International Nuclear Information System (INIS)

    Ismullah M, Muh. Fawzy; Lantu,; Aswad, Sabrianto; Massinai, Muh. Altin

    2015-01-01

    Indonesia is the meeting zone between three world main plates: Eurasian Plate, Pacific Plate, and Indo – Australia Plate. Therefore, Indonesia has a high seismicity degree. Sulawesi is one of whose high seismicity level. The earthquake centre lies in fault zone so the earthquake data gives tectonic visualization in a certain place. This research purpose is to identify Sulawesi tectonic model by using earthquake data from 1993 to 2012. Data used in this research is the earthquake data which consist of: the origin time, the epicenter coordinate, the depth, the magnitude and the fault parameter (strike, dip and slip). The result of research shows that there are a lot of active structures as a reason of the earthquake in Sulawesi. The active structures are Walannae Fault, Lawanopo Fault, Matano Fault, Palu – Koro Fault, Batui Fault and Moluccas Sea Double Subduction. The focal mechanism also shows that Walannae Fault, Batui Fault and Moluccas Sea Double Subduction are kind of reverse fault. While Lawanopo Fault, Matano Fault and Palu – Koro Fault are kind of strike slip fault

  8. Tectonics earthquake distribution pattern analysis based focal mechanisms (Case study Sulawesi Island, 1993–2012)

    Energy Technology Data Exchange (ETDEWEB)

    Ismullah M, Muh. Fawzy, E-mail: mallaniung@gmail.com [Master Program Geophysical Engineering, Faculty of Mining and Petroleum Engineering (FTTM), Bandung Institute of Technology (ITB), Jl. Ganesha no. 10, Bandung, 40116, Jawa Barat (Indonesia); Lantu,; Aswad, Sabrianto; Massinai, Muh. Altin [Geophysics Program Study, Faculty of Mathematics and Natural Sciences, Hasanuddin University (UNHAS), Jl. PerintisKemerdekaan Km. 10, Makassar, 90245, Sulawesi Selatan (Indonesia)

    2015-04-24

    Indonesia is the meeting zone between three world main plates: Eurasian Plate, Pacific Plate, and Indo – Australia Plate. Therefore, Indonesia has a high seismicity degree. Sulawesi is one of whose high seismicity level. The earthquake centre lies in fault zone so the earthquake data gives tectonic visualization in a certain place. This research purpose is to identify Sulawesi tectonic model by using earthquake data from 1993 to 2012. Data used in this research is the earthquake data which consist of: the origin time, the epicenter coordinate, the depth, the magnitude and the fault parameter (strike, dip and slip). The result of research shows that there are a lot of active structures as a reason of the earthquake in Sulawesi. The active structures are Walannae Fault, Lawanopo Fault, Matano Fault, Palu – Koro Fault, Batui Fault and Moluccas Sea Double Subduction. The focal mechanism also shows that Walannae Fault, Batui Fault and Moluccas Sea Double Subduction are kind of reverse fault. While Lawanopo Fault, Matano Fault and Palu – Koro Fault are kind of strike slip fault.

  9. State-of-the-art for evaluating the potential impact of tectonism and volcanism on a radioactive waste repository

    International Nuclear Information System (INIS)

    1980-01-01

    Most estimates of the time required for safe isolation of radioactive wastes from the biosphere range from 100,000 to 1,000,000 years. For such long time spans, it is necessary to assess the potential effects of geologic processes such as volcanism and tectonic activity on the integrity of geologic repositories. Predictions of geologic phenomena can be based on probabilistic models, which assume a random distribution of events. The necessary historic and geologic records are rarely available to provide an adequate data base for such predictions. The observed distribution of volcanic and tectonic activity is not random, and appears to be controlled by extremely complex deterministic processes. The advent of global plate tectonic theory in the past two decades has been a giant step toward understanding these processes. At each potential repository site, volcanic and tectonic processes should be evaluated to provide the most thorough possible understanding of those deterministic processes. Based on this knowledge, judgements will have to be made as to whether or not the volcanic and tectonic processes pose unacceptable risk to the integrity of the repository. This report describes the potential hazards associated with volcanism and tectonism, and the means for evaluating these processes

  10. Earthquake recurrence and magnitude and seismic deformation of the northwestern Okhotsk plate, northeast Russia

    Science.gov (United States)

    Hindle, D.; Mackey, K.

    2011-02-01

    Recorded seismicity from the northwestern Okhotsk plate, northeast Asia, is currently insufficient to account for the predicted slip rates along its boundaries due to plate tectonics. However, the magnitude-frequency relationship for earthquakes from the region suggests that larger earthquakes are possible in the future and that events of ˜Mw 7.5 which should occur every ˜100-350 years would account for almost all the slip of the plate along its boundaries due to Eurasia-North America convergence. We use models for seismic slip distribution along the bounding faults of Okhotsk to conclude that relatively little aseismic strain release is occurring and that larger future earthquakes are likely in the region. Our models broadly support the idea of a single Okhotsk plate, with the large majority of tectonic strain released along its boundaries.

  11. Paper microzone plates.

    Science.gov (United States)

    Carrilho, Emanuel; Phillips, Scott T; Vella, Sarah J; Martinez, Andres W; Whitesides, George M

    2009-08-01

    This paper describes 96- and 384-microzone plates fabricated in paper as alternatives to conventional multiwell plates fabricated in molded polymers. Paper-based plates are functionally related to plastic well plates, but they offer new capabilities. For example, paper-microzone plates are thin (approximately 180 microm), require small volumes of sample (5 microL per zone), and can be manufactured from inexpensive materials ($0.05 per plate). The paper-based plates are fabricated by patterning sheets of paper, using photolithography, into hydrophilic zones surrounded by hydrophobic polymeric barriers. This photolithography used an inexpensive formulation photoresist that allows rapid (approximately 15 min) prototyping of paper-based plates. These plates are compatible with conventional microplate readers for quantitative absorbance and fluorescence measurements. The limit of detection per zone loaded for fluorescence was 125 fmol for fluorescein isothiocyanate-labeled bovine serum albumin, and this level corresponds to 0.02 the quantity of analyte per well used to achieve comparable signal-to-noise in a 96-well plastic plate (using a solution of 25 nM labeled protein). The limits of detection for absorbance on paper was approximately 50 pmol per zone for both Coomassie Brilliant Blue and Amaranth dyes; these values were 0.4 that required for the plastic plate. Demonstration of quantitative colorimetric correlations using a scanner or camera to image the zones and to measure the intensity of color, makes it possible to conduct assays without a microplate reader.

  12. Geomorphic Response to Spatial and Temporal Tectonic uplift on the Kenya Rift of East African Rift System

    Science.gov (United States)

    Xue, L.; Abdelsalam, M. G.

    2017-12-01

    Tectonic uplifts of the shoulders of the East Africa Rift System (EARS) have significant impact on the geological record by reorganizing drainage systems, increasing sediment supply, and changing climate and biogeography. Recent studies in geochronology, geomorphology and geophysics have provided some understanding of the timing of tectonic uplift and its distribution pattern of the (EARS). We do not know how the vertical motion is localized along the rift axis and the relative roles of upwelling of magma and rift extensional processes play in tectonic uplift history. This work presents detailed morphometric study of the fluvial landscape response to the tectonic uplift and climate shifting of the Kenya Rift shoulders in order to reconstruct their incision history, with special attention to timing, location, and intensity of uplift episodes. This work compiles the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) and Sentinel-2A data, summarized previous 39Ar-40Ar and thermochronology data, and calculates long-term incision rate and geomorphic proxies (normalized steepness and chi-integral) along the Kenya Rift. It also models the age of tectonic/climatic events by using knickpoint celerity model and R/SR integrative approach. It found that the maximum long-term incision rates of 300 mm/kyr to be at the central Kenya Rift, possibly related to the mantle-driven process and rapid tectonic uplift. The geomorphic proxies indicate southward decreasing pattern of the short-term incision rate, possibly related to the migration of the mantle plume.

  13. Peculiarity of the Relationship between the Seismicity and Tectonic Structure of the Pyrenees

    Science.gov (United States)

    Lukk, A. A.; Shevchenko, V. I.

    2018-05-01

    The geotectonic position of the Pyrenees mountain massif in the Alpine-Indonesian mobile belt is considered. The geological data testify to the formation of the structure of the Pyrenees in the setting of a subhorizontal compression perpendicular to the ridge. The commonly accepted interpretation considers this compression in the context of plate tectonic notions related to the collision between the Iberian and Eurasian lithospheric plates resulting from the convergence of the Eurasian and African plates. However, this interpretation is challenged by the the geodetic and seismological measurements. The GPS measurements suggest a certain cross-strike spreading rather than shortening of the Earth's crust; the focal mechanisms of the earthquakes indicate the predominance of a subhorizontal extension perpendicular to the strike of the Pyrenees mountain range. The processes of the gravitational collapse of the mountain chain during the isostatic upwelling of the orogenic crust are considered as the most probable cause of this spreading by a number of the authors.

  14. Secondary reconstruction of maxillofacial trauma.

    Science.gov (United States)

    Castro-Núñez, Jaime; Van Sickels, Joseph E

    2017-08-01

    Craniomaxillofacial trauma is one of the most complex clinical conditions in contemporary maxillofacial surgery. Vital structures and possible functional and esthetic sequelae are important considerations following this type of trauma and intervention. Despite the best efforts of the primary surgery, there are a group of patients that will have poor outcomes requiring secondary reconstruction to restore form and function. The purpose of this study is to review current concepts on secondary reconstruction to the maxillofacial complex. The evaluation of a posttraumatic patient for a secondary reconstruction must include an assessment of the different subunits of the upper face, middle face, and lower face. Virtual surgical planning and surgical guides represent the most important innovations in secondary reconstruction over the past few years. Intraoperative navigational surgery/computed-assisted navigation is used in complex cases. Facial asymmetry can be corrected or significantly improved by segmentation of the computerized tomography dataset and mirroring of the unaffected side by means of virtual surgical planning. Navigational surgery/computed-assisted navigation allows for a more precise surgical correction when secondary reconstruction involves the replacement of extensive anatomical areas. The use of technology can result in custom-made replacements and prebent plates, which are more stable and resistant to fracture because of metal fatigue. Careful perioperative evaluation is the key to positive outcomes of secondary reconstruction after trauma. The advent of technological tools has played a capital role in helping the surgical team perform a given treatment plan in a more precise and predictable manner.

  15. Optimisation and validation of a 3D reconstruction algorithm for single photon emission computed tomography by means of GATE simulation platform; Optimisation et validation d'un algorithme de reconstruction 3D en Tomographie d'Emission Monophotonique a l'aide de la plate forme de simulation GATE

    Energy Technology Data Exchange (ETDEWEB)

    El Bitar, Ziad [Ecole Doctorale des Sciences Fondamentales, Universite Blaise Pascal, U.F.R de Recherches Scientifiques et Techniques, 34, avenue Carnot - BP 185, 63006 Clermont-Ferrand Cedex (France); Laboratoire de Physique Corpusculaire, CNRS/IN2P3, 63177 Aubiere (France)

    2006-12-15

    Although time consuming, Monte-Carlo simulations remain an efficient tool enabling to assess correction methods for degrading physical effects in medical imaging. We have optimized and validated a reconstruction method baptized F3DMC (Fully 3D Monte Carlo) in which the physical effects degrading the image formation process were modelled using Monte-Carlo methods and integrated within the system matrix. We used the Monte-Carlo simulation toolbox GATE. We validated GATE in SPECT by modelling the gamma-camera (Philips AXIS) used in clinical routine. Techniques of threshold, filtering by a principal component analysis and targeted reconstruction (functional regions, hybrid regions) were used in order to improve the precision of the system matrix and to reduce the number of simulated photons as well as the time consumption required. The EGEE Grid infrastructures were used to deploy the GATE simulations in order to reduce their computation time. Results obtained with F3DMC were compared with the reconstruction methods (FBP, ML-EM, MLEMC) for a simulated phantom and with the OSEM-C method for the real phantom. Results have shown that the F3DMC method and its variants improve the restoration of activity ratios and the signal to noise ratio. By the use of the grid EGEE, a significant speed-up factor of about 300 was obtained. These results should be confirmed by performing studies on complex phantoms and patients and open the door to a unified reconstruction method, which could be used in SPECT and also in PET. (author)

  16. A new tectonic model for southern Alaska

    Science.gov (United States)

    Reeder, J. W.

    2013-12-01

    S Alaska consists of a complex tectonic boundary that is gradational from subduction of Pacific Plate (PAC) beneath N American Plate (NA) in the W to a transform fault between these two plates in the SE. Adding complexity, the Yakutat Plate (YAK) is in between. The YAK is exposed in NE Gulf of Alaska and has been well mapped (Plafker, 1987). It is bound by the NA to the E at the Fairweather fault and by the PAC to the S. Relative to NA, YAK is moving 47 mm/yr N30°W and PAC is moving 51 mm/yr N20°W (Fletcher & Freymueller, 2003). The YAK and deeper PAC extend NW beneath the NA as flat slabs (Brocher et al., 1994). They subduct to the W and NW in Cook Inlet region (Ratchkovsky et al., 1997), resulting in the Cook Inlet volcanic arc. They also subduct farther NNW toward the Denali volcanic gap and fault. The subducted part of the YAK is split by a transform fault exposed at Montana Creek (MC) at 62°06'N to 62°10'N at 150°W. It extends S60°W toward the most N Cook Inlet volcano, Hayes, and extends N60°E beyond Talkeetna Mts. Right-lateral WSW motion and thick fault gauge have been documented by McGee (1978) on MC and a S60°W fault scarp cutting Quaternary deposits has been mapped (Reed & Nelson, 1980). Fuis et al. (2008) seismically recognized 110 km of missing YAP NW of Talkeetna Mts, which he thought was due to a 'tear' in the YAK to the far S. Nikoli Greenstone has been found in the Talkeetna Mts just S of this transform (Schmidt, 2003) that is 70 km SW of any other mapped Nikoli. This fault offset is also shown by 7.8 km/sec Vp depth contours, which represent the YAK (Eberhart-Phillips et al., 2006), as 110 km at N60°W. Based on magnetic data (Csejtey & Griscom, 1978; Saltus et al., 2007), the fault is regionally recognized as a 10× km zone on the WSW margin of the large S Alaska magnetic high. The fault zone has narrow WSW magnetic highs and depressions. This fault is also recognized on digital relief (Riehle et al., 1996); but, another pronounced N60

  17. The tectonic evolution of the southeastern Terceira Rift/São Miguel region (Azores)

    Science.gov (United States)

    Weiß, B. J.; Hübscher, C.; Lüdmann, T.

    2015-07-01

    The eastern Azores Archipelago with São Miguel being the dominant subaerial structure is located at the intersection of an oceanic rift (Terceira Rift) with a major transform fault (Gloria Fault) representing the westernmost part of the Nubian-Eurasian plate boundary. The evolution of islands, bathymetric highs and basin margins involves strong volcanism, but the controlling geodynamic and tectonic processes are currently under debate. In order to study this evolution, multibeam bathymetry and marine seismic reflection data were collected to image faults and stratigraphy. The basins of the southeastern Terceira Rift are rift valleys whose southwestern and northeastern margins are defined by few major normal faults and several minor normal faults, respectively. Since São Miguel in between the rift valleys shows an unusual W-E orientation, it is supposed to be located on a leaky transform. South of the island and separated by a N120° trending graben system, the Monacco Bank represents a N160° oriented flat topped volcanic ridge dominated by tilted fault blocks. Up to six seismic units are interpreted for each basin. Although volcanic ridges hamper a direct linking of depositional strata between the rift and adjacent basins, the individual seismic stratigraphic units have distinct characteristics. Using these units to provide a consistent relative chrono-stratigraphic scheme for the entire study area, we suggest that the evolution of the southeastern Terceira Rift occurred in two stages. Considering age constrains from previous studies, we conclude that N140° structures developed orthogonal to the SW-NE direction of plate-tectonic extension before ~ 10 Ma. The N160° trending volcanic ridges and faults developed later as the plate tectonic spreading direction changed to WSW-ENE. Hence, the evolution of the southeastern Terceira Rift domain is predominantly controlled by plate kinematics and lithospheric stress forming a kind of a re-organized rift system.

  18. Triassic to Cenozoic multi-stage intra-plate deformation focused near the Bogd Fault system, Gobi Altai, Mongolia

    Directory of Open Access Journals (Sweden)

    Douwe J.J. van Hinsbergen

    2015-09-01

    Full Text Available The Gobi Altai region of southern Mongolia has been in the Eurasian plate interior since the mid-Mesozoic, yet has experienced episodic phases of deformation since that time. In this paper, we document field evidence to characterize and date the intra-plate tectonic history of the Gobi Altai region from the Triassic to the present. To this end, we provide detailed mapping of the structure and stratigraphy of the eastern flanks of Mt. Ih Bogd that contains the widest variety of rock-time units in the area. We carry out geochronological analysis of basaltic lavas and basement granite in the area. We demonstrate that a crystalline basement with a 502 ± 8 Ma granitoid (U/Pb underwent two phases of basin formation in the Mesozoic, which we date with new 40Ar/39Ar lava ages of 218.5 ± 1.5, 123.2 ± 0.7 and 124.8 ± 1.2 Ma, respectively. Both phases are linked to deposition of fluvio-lacustrine sediments and trap-like basaltic volcanics, with cumulative thicknesses of 1000–1500 m. Both basins were likely north-facing half-grabens that developed under ∼N–S extension, but were subsequently overthrusted by Paleozoic and older crystalline basement during a less well constrained, but likely mid-Cretaceous phase of N–S shortening and basin inversion. Our results are consistent with recent seismic imaging of rift basins ∼100 km to the NE of the study area where a similar history was reconstructed. The multiple phases of intra-plate deformation appear to have parallel structural trends, most likely due to reactivated Paleozoic basement structures created during the original terrane amalgamation of the Central Asian Orogenic Belt continental crust. This strong basement heterogeneity may predispose it to reactivation, and make it sensitive to changes in the overall stress field of the Eurasian plate driven by forces at its margins and base. Detailed study of Mongolia's multi-stage tectonic history may thus provide a key proxy for the long

  19. Tectonic, Climatic and Anthropogenic Vertical Land Movements in Western Europe by Repeated Absolute Gravity Measurements

    Science.gov (United States)

    van Camp, M. J.; de Viron, O.; Lecocq, T.; Hinzen, K. G.; Quinif, Y.; Williams, S. D.; Camelbeeck, T.

    2010-12-01

    In continental plate interiors, tectonic deformations are small and the associated ground surface movements remain close to or below the accuracy of current geodetic techniques, and at the limit of the noise level. An absolute gravimeter is an appropriate tool to quantify slow vertical movements, as this instrument, based on length and time standards, is drift free and does not depend on any terrestrial reference frame. Repeated absolute gravity (AG) measurements have been performed in Oostende (Belgian coastline) and at 8 stations along a southwest-northeast profile across the Belgian Ardennes and the Roer Valley Graben (Germany), in order to estimate the tectonic deformations in the area. After 7-13 years (depending on the station), we find evidence that the movements are no larger than a few millimeter per year and result from a combination of anthropogenic, climatic, tectonic, and Glacial Isostatic Adjustment (GIA) effects. This demonstrates the importance of precisely modeling the GIA effects in order to investigate intraplate tectonic deformations at the sub-millimeter level. This study also shows that AG measurements, repeated once or twice a year, can resolve vertical velocities at the 1.0 mm/yr level after 10 years, even in difficult conditions, provided that the gravimeter is carefully maintained.

  20. Pre-operative planning for mandibular reconstruction - A full digital planning workflow resulting in a patient specific reconstruction

    Science.gov (United States)

    2011-01-01

    Objectives Reconstruction of large mandiblular defects following ablative oncologic surgery could be done by using vascularized bone transfer or, more often, primarily with simultaneous or delayed bone grafting, using load bearing reconstruction plates. Bending of these reconstruction plates is typically directed along the outer contour of the original mandible. Simultaneously or in a second operation vascularized or non-vascularized bone is fixed to the reconstruction plate. However, the prosthodontic-driven backward planning to ease bony reconstruction of the mandible in terms of dental rehabilitation using implant-retained overdentures might be an eligible solution. The purpose of this work was to develop, establish and clinically evaluate a novel 3D planning procedure for mandibular reconstruction. Materials and methods Three patients with tumors involving the mandible, which included squamous cell carcinoma in the floor of the mouth and keratocystic odontogenic tumor, were treated surgically by hemimandibulectomy. Results In primary alloplastic mandible reconstruction, shape and size of the reconstruction plate could be predefined and prebent prior to surgery. Clinical relevance This study provides modern treatment strategies for mandibular reconstruction. PMID:21968330

  1. Easy handling of tectonic data: the programs TectonicVB for Mac and TectonicsFP for Windows™

    Science.gov (United States)

    Ortner, Hugo; Reiter, Franz; Acs, Peter

    2002-12-01

    TectonicVB for Macintosh and TectonicsFP for Windows TM operating systems are two menu-driven computer programs which allow the shared use of data on these environments. The programs can produce stereographic plots of orientation data (great circles, poles, lineations). Frequently used statistical procedures like calculation of eigenvalues and eigenvectors, calculation of mean vector with concentration parameters and confidence cone can be easily performed. Fault data can be plotted in stereographic projection (Angelier and Hoeppener plots). Sorting of datasets into homogeneous subsets and rotation of tectonic data can be performed in interactive two-diagram windows. The paleostress tensor can be calculated from fault data sets using graphical (calculation of kinematic axes and right dihedra method) or mathematical methods (direct inversion or numerical dynamical analysis). The calculations can be checked in dimensionless Mohr diagrams and fluctuation histograms.

  2. The Importance of Lower Mantle Structure to Plate Stresses and Plate Motions

    Science.gov (United States)

    Holt, W. E.; Wang, X.; Ghosh, A.

    2016-12-01

    Plate motions and plate stresses are widely assumed as the surface expression of mantle convection. The generation of plate tectonics from mantle convection has been studied for many years. Lithospheric thickening (or ridge push) and slab pull forces are commonly accepted as the major driving forces for the plate motions. However, the importance of the lower mantle to plate stresses and plate motions remains less clear. Here, we use the joint modeling of lithosphere and mantle dynamics approach of Wang et al. (2015) to compute the tractions originating from deeper mantle convection and follow the method of Ghosh et al. (2013) to calculate gravitational potential energy per unit area (GPE) based on Crust 1.0 (Laske et al., 2013). Absolute values of deviatoric stresses are determined by the body force distributions (GPE gradients and traction magnitudes applied at the base of the lithosphere). We use the same relative viscosity model that Ghosh et al. (2013) used, and we solve for one single adjustable scaling factor that multiplies the entire relative viscosity field to provide absolute values of viscosity throughout the lithosphere. This distribution of absolute values of lithosphere viscosities defines the magnitudes of surface motions. In this procedure, the dynamic model first satisfies the internal constraint of no-net-rotation of motions. The model viscosity field is then scaled by the single factor until we achieve a root mean square (RMS) minimum between computed surface motions and the kinematic no-net-rotation (NNR) model of Kreemer et al. (2006). We compute plate stresses and plate motions from recently published global tomography models (over 70 based on Wang et al., 2015). We find that RMS misfits are significantly reduced when details of lower mantle structure from the latest tomography models are added to models that contain only upper and mid-mantle density distributions. One of the key reasons is that active upwelling from the Large Low Shear

  3. Iapetus: Tectonic structure and geologic history

    Science.gov (United States)

    Croft, Steven K.

    1991-01-01

    Many papers have been written about the surface of Iapetus, but most of these have discussed either the nature of the strongly contrasting light and dark materials or the cratering record. Little has been said about other geologic features on Iapetus, such as tectonic structures, which would provide constraints on Iapetus' thermal history. Most references have suggested that there is no conclusive evidence for any tectonic activity, even when thermal history studies indicate that there should be. However, a new study of Iapetus' surface involving the use of stereo pairs, an extensive tectonic network has been recognized. A few new observations concerning the craters and dark material were also made. Thus the geology and geologic history of Iapetus can be more fully outlined than before. The tectonic network is shown along with prominent craters and part of the dark material in the geologic/tectonic sketch map. The topology of crater rims and scarps are quite apparent and recognizable in the different image pairs. The heights and slopes of various features given are based on comparison with the depths of craters 50 to 100 km in diameter, which are assumed to have the same depths as craters of similar diameter on Rhea and Titania.

  4. Vaginal reconstruction

    International Nuclear Information System (INIS)

    Lesavoy, M.A.

    1985-01-01

    Vaginal reconstruction can be an uncomplicated and straightforward procedure when attention to detail is maintained. The Abbe-McIndoe procedure of lining the neovaginal canal with split-thickness skin grafts has become standard. The use of the inflatable Heyer-Schulte vaginal stent provides comfort to the patient and ease to the surgeon in maintaining approximation of the skin graft. For large vaginal and perineal defects, myocutaneous flaps such as the gracilis island have been extremely useful for correction of radiation-damaged tissue of the perineum or for the reconstruction of large ablative defects. Minimal morbidity and scarring ensue because the donor site can be closed primarily. With all vaginal reconstruction, a compliant patient is a necessity. The patient must wear a vaginal obturator for a minimum of 3 to 6 months postoperatively and is encouraged to use intercourse as an excellent obturator. In general, vaginal reconstruction can be an extremely gratifying procedure for both the functional and emotional well-being of patients

  5. ACL Reconstruction

    Science.gov (United States)

    ... in moderate exercise and recreational activities, or play sports that put less stress on the knees. ACL reconstruction is generally recommended if: You're an athlete and want to continue in your sport, especially if the sport involves jumping, cutting or ...

  6. Researches on tectonic uplift and denudation with relation to geological disposal of HLW in Japan

    International Nuclear Information System (INIS)

    Fujiwara, Osamu; Sanga, Tomoji; Moriya, Toshifumi

    2005-01-01

    This paper reviews the present state of researches on tectonic uplift and denudation, and shows perspective goals and direction of future researches from the viewpoint of geological disposal of HLW in Japan. Detailed history of tectonics and denudation in geologic time scale, including the rates, temporal and spatial distributions and processes, reconstructed from geologic and geomorphologic evidences will enable us to make the geological predictions. Improvements of the analytic methods for the geological histories, e.g. identification of the tectonic and denudational imprints and age determinations, are indispensable for the accurate prediction. Developments of the tools and methodologies for assessments of the degree and extension of influences by the tectonic uplift, subsidence and denudation on the geological environments such as ground water flows are also fundamental problem in the study field of the geological disposal of HLW. Collaboration of scientific researches using the geological and geomorphological methods and applied technology, such as numerical simulations of ground water flows, is important in improving the safety and accuracy of the geological disposal of HLW. (author)

  7. Preface of special issue on ;tectonics, volcanism and geo-energy in East Asia;

    Science.gov (United States)

    Song, Sheng-Rong; Chen, Cheng-Hong; Ryu, Byong-Jae; Lin, Saulwood

    2017-11-01

    The East Asia, from north to south, including Russia, China, Korea, Japan, Taiwan, Philippines and Indonesia etc., is one of the most active tectonic and natural hazardous regions in the world. The subduction and collision zones, such as the Pacific Plate subducting into the Japan Arc and the Philippine Sea, and the Philippine Sea Plate subducting into the Eurasia Plate, and the collision zones of the Philippine Sea Plate with the Asian continental margin in the Taiwan mountain belt, and the India Plate with the Eurasia Plate in Himalaya mountain belts, distribute widely in this region. It is also the most densely populated areas in the world. More than two billion people (one/third populations of the world) live in East Asia. Most of disastrous natural hazards, such as volcanic eruptions, earthquakes and debris flows induced by floods occur frequently and cause many building collapses and causalities in this area. Geoscientists, therefore, must seriously consider and endeavor for mitigations of the natural hazards and reduction of the properties lose and human death.

  8. Positron emission zone plate holography for particle tracking

    Energy Technology Data Exchange (ETDEWEB)

    Gundogdu, O. [University of Birmingham, School of Physics and Astronomy, Birmingham B15 2TT (United Kingdom)]. E-mail: o.gundogdu@surrey.ac.uk

    2006-01-15

    Positron Emission Particle Tracking (PEPT) is a powerful non-invasive technique that has been used extensively for tracking a single particle. In this paper, we present a study of zone plate holography method in order to track multiple particles, mainly two particles. The main aim is to use as small number of events as possible in the order to make it possible to track particles in fast moving industrial systems. A zone plate with 100% focal efficiency is simulated and applied to the Positron Emission Tomography (PET) data for multiple particle tracking. A simple trajectory code was employed to explore the effects of the nature of the experimental trajectories. A computer holographic reconstruction code that simulates optical reconstruction was developed. The different aspects of the particle location, particle activity ratios for enabling tagging of particles and zone plate and hologram locations are investigated. The effect of the shot noise is investigated and the limitations of the zone plate holography are reported.

  9. Positron emission zone plate holography for particle tracking

    International Nuclear Information System (INIS)

    Gundogdu, O.

    2006-01-01

    Positron Emission Particle Tracking (PEPT) is a powerful non-invasive technique that has been used extensively for tracking a single particle. In this paper, we present a study of zone plate holography method in order to track multiple particles, mainly two particles. The main aim is to use as small number of events as possible in the order to make it possible to track particles in fast moving industrial systems. A zone plate with 100% focal efficiency is simulated and applied to the Positron Emission Tomography (PET) data for multiple particle tracking. A simple trajectory code was employed to explore the effects of the nature of the experimental trajectories. A computer holographic reconstruction code that simulates optical reconstruction was developed. The different aspects of the particle location, particle activity ratios for enabling tagging of particles and zone plate and hologram locations are investigated. The effect of the shot noise is investigated and the limitations of the zone plate holography are reported

  10. Multi-phase structural and tectonic evolution of the Andaman Sea Region

    Science.gov (United States)

    Masterton, Sheona; Hill, Catherine; Sagi, David Adam; Webb, Peter; Sevastjanova, Inga

    2017-04-01

    We present a new regional tectonic interpretation for Myanmar and the Andaman Sea, built within the framework of global plate motions. In our model the Present Day Andaman Sea region has been subjected to multiple phases of extension, culminating in its mid-Miocene to Present Day opening as a rhomboidal pull-apart basin. The Andaman Sea region is historically thought to have developed as a consequence of back-arc opening associated with plate convergence at the Andaman-Nicobar subduction system. We have undertaken detailed structural interpretation of potential field, Landsat and SRTM data, supported by 2-D crustal models of the Andaman Sea. From this analysis we identified several major north-south striking faults and a series of northeast-southwest striking structures across the region. We have also mapped the extent of the Andaman-Nicobar Accretionary Prism, a fore arc trough and volcanic arc, which we associate with a phase of traditional trench-parallel back-arc extension from the Paleocene to the middle Miocene. A regional tectonic event occurred during the middle Miocene that caused the cessation of back-arc extension in the Present Day Andaman Sea and an eastward shift in the locus of arc-related volcanism. At that time, N-S striking faults onshore and offshore Myanmar were reactivated with widespread right-lateral motion. This motion, accompanied by extension along new NE-SW striking faults, facilitated the opening of the Central Andaman Basin as a pull-apart basin (rhombochasm) in which a strike-slip tectonic regime has a greater impact on the mode of opening than the subduction process. The integration of our plate model solution within a global framework allows identification of major plate reorganisation events and their impact on a regional scale. We therefore attribute the onset of pull-apart opening in the Andaman Sea to ongoing clockwise rotation of the western Sundaland margin throughout the late Paleogene and early Miocene, possibly driven by the

  11. What drives microplate motion and deformation in the northeastern Caribbean plate boundary region?

    NARCIS (Netherlands)

    van Benthem, S.A.C.; Govers, R.; Wortel, R.

    2014-01-01

    The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the “Bahamas Collision”) is generally invoked as a cause of this fragmentation. We propose that a second

  12. Summary of the stretching tectonics research

    International Nuclear Information System (INIS)

    Yu Dagan

    1994-01-01

    The rise of stretching tectonics is established on the basis of recent structural geology theory, the establishment of metamorphic nucleus complex structural model on one hand plays an important promoting art to the development of stretching structure, on the other hand, it needs constant supplement and perfection in practice. Metamorphic nucleus complex is the carrier of comparatively deep geological information in vertical section of the crust and has wide distribution in the era of south China. Evidently, it can be taken as the 'key' to understanding the deep and studying the basement, Strengthening the study will play the important promoting role to the deep prospecting. The study of stretching tectonics is not only limited within the range of structure and metamorphism, but combine with the studies of sedimentation, magmatism, metamorphism and mineralization, thus form a new field of tectonic geology of self-developing system

  13. Create Your Plate

    Medline Plus

    Full Text Available ... Type 2 Diabetes Know Your Rights Employment Discrimination Health Care Professionals Law ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart- ...

  14. Create Your Plate

    Medline Plus

    Full Text Available ... Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday ... Carbohydrates Types of Carbohydrates Carbohydrate Counting Make Your Carbs ...

  15. Limestone and chert in tectonic blocks from the Esk Head subterrane, South Island, New Zealand

    Science.gov (United States)

    Silberling, Norman J.; Nichols, K.M.; Bradshaw, J.D.; Blome, C.D.

    1988-01-01

    The Esk Head subterrane is a continuous belt, generally 10-20 km wide, of tectonic melange and broken formation on the South Island of New Zealand. This subterrane separates older and younger parts of the Torlesse terrane which is an extensive accretionary prism composed mostly of quartzo-feldspathic, submarine-fan deposits ranging from Permian to Early Cretaceous in age. The Esk Head subterrane of the Torlesse is especially informative because it includes within it conspicuous tectonic blocks of submarine basalt and a variety of basalt-associated seamount and sea-floor limestones and cherty rocks thought to be representative of the subducted plate. Paleogeographic inferences drawn from megafossils, bioclasts, and radiolarians, as well as from carbonate cements, indicate deposition of the oceanic sedimentary rocks at paleolatitudes somewhat lower than that of the New Zealand part of the Gondwana margin, but higher than paleoequatorial latitudes. -Authors

  16. The evolution of volcanism, tectonics, and volatiles on Mars - An overview of recent progress

    Science.gov (United States)

    Zimbelman, James R.; Solomon, Sean C.; Sharpton, Virgil L.

    1991-01-01

    Significant results of the 'Mars: Evolution of Volcanism, Tectonics, and Volatiles' (MEVTV) project are presented. The data for the project are based on geological mapping from the Viking images, petrologic and chemical analyses of SNC meteorites, and both mapping and temporal grouping of major fault systems. The origin of the planet's crustal dichotomy is examined in detail, the kinematics and formation of wrinkle ridges are discussed, and some new theories are set forth. Because the SNC meteorites vary petrologically and isotopically, the sources of the parental Martian magma are heterogeneous. Transcurrent faulting coupled with the extensional strains that form Valles Marineris suggest early horizontal movement of lithospheric blocks. A theory which connects the formation of the crustal dichotomy to the Tharsis region associates the horizontal motions with plate tectonics that generated a new lithosphere.

  17. Swath sonar mapping of Earth's submarine plate boundaries

    Science.gov (United States)

    Carbotte, S. M.; Ferrini, V. L.; Celnick, M.; Nitsche, F. O.; Ryan, W. B. F.

    2014-12-01

    The recent loss of Malaysia Airlines flight MH370 in an area of the Indian Ocean where less than 5% of the seafloor is mapped with depth sounding data (Smith and Marks, EOS 2014) highlights the striking lack of detailed knowledge of the topography of the seabed for much of the worlds' oceans. Advances in swath sonar mapping technology over the past 30 years have led to dramatic improvements in our capability to map the seabed. However, the oceans are vast and only an estimated 10% of the seafloor has been mapped with these systems. Furthermore, the available coverage is highly heterogeneous and focused within areas of national strategic priority and community scientific interest. The major plate boundaries that encircle the globe, most of which are located in the submarine environment, have been a significant focus of marine geoscience research since the advent of swath sonar mapping. While the location of these plate boundaries are well defined from satellite-derived bathymetry, significant regions remain unmapped at the high-resolutions provided by swath sonars and that are needed to study active volcanic and tectonic plate boundary processes. Within the plate interiors, some fossil plate boundary zones, major hotspot volcanoes, and other volcanic provinces have been the focus of dedicated research programs. Away from these major tectonic structures, swath mapping coverage is limited to sparse ocean transit lines which often reveal previously unknown deep-sea channels and other little studied sedimentary structures not resolvable in existing low-resolution global compilations, highlighting the value of these data even in the tectonically quiet plate interiors. Here, we give an overview of multibeam swath sonar mapping of the major plate boundaries of the globe as extracted from public archives. Significant quantities of swath sonar data acquired from deep-sea regions are in restricted-access international archives. Open access to more of these data sets would

  18. Crustal deformation and volcanism at active plate boundaries

    Science.gov (United States)

    Geirsson, Halldor

    Most of Earth's volcanoes are located near active tectonic plate boundaries, where the tectonic plates move relative to each other resulting in deformation. Likewise, subsurface magma movement and pressure changes in magmatic systems can cause measurable deformation of the Earth's surface. The study of the shape of Earth and therefore studies of surface deformation is called geodesy. Modern geodetic techniques allow precise measurements (˜1 mm accuracy) of deformation of tectonic and magmatic systems. Because of the spatial correlation between tectonic boundaries and volcanism, the tectonic and volcanic deformation signals can become intertwined. Thus it is often important to study both tectonic and volcanic deformation processes simultaneously, when one is trying to study one of the systems individually. In this thesis, I present research on crustal deformation and magmatic processes at active plate boundaries. The study areas cover divergent and transform plate boundaries in south Iceland and convergent and transform plate boundaries in Central America, specifically Nicaragua and El Salvador. The study is composed of four main chapters: two of the chapters focus on the magma plumbing system of Hekla volcano, Iceland and the plate boundary in south Iceland; one chapter focuses on shallow controls of explosive volcanism at Telica volcano, Nicaragua; and the fourth chapter focuses on co- and post-seismic deformation from a Mw = 7.3 earthquake which occurred offshore El Salvador in 2012. Hekla volcano is located at the intersection of a transform zone and a rift zone in Iceland and thus is affected by a combination of shear and extensional strains, in addition to co-seismic and co-rifting deformation. The inter-eruptive deformation signal from Hekla is subtle, as observed by a decade (2000-2010) of GPS data in south Iceland. A simultaneous inversion of this data for parameters describing the geometry and source characteristics of the magma chamber at Hekla, and

  19. Drilling to investigate processes in active tectonics and magmatism

    Science.gov (United States)

    Shervais, J.; Evans, J.; Toy, V.; Kirkpatrick, J.; Clarke, A.; Eichelberger, J.

    2014-12-01

    convergent plate margins (subduction zones). This workshop brought together a diverse group of scientists with a broad range of scientific experience and interests. A particular strength was the involvement of both early-career scientists, who will initiate and carry out these new research programs, and more senior researchers with many years of experience in scientific drilling and active tectonics research. Each of the themes and questions outlined above has direct benefits to society, including improving hazard assessment, direct monitoring of active systems for early warning, renewable and non-renewable resource and energy exploitation, and predicting the environmental impacts of natural hazards, emphasizing the central role that scientific drilling will play in future scientific and societal developments.

  20. Maxillary reconstruction

    Directory of Open Access Journals (Sweden)

    Brown James

    2007-12-01

    Full Text Available This article aims to discuss the various defects that occur with maxillectomy with a full review of the literature and discussion of the advantages and disadvantages of the various techniques described. Reconstruction of the maxilla can be relatively simple for the standard low maxillectomy that does not involve the orbital floor (Class 2. In this situation the structure of the face is less damaged and the there are multiple reconstructive options for the restoration of the maxilla and dental alveolus. If the maxillectomy includes the orbit (Class 4 then problems involving the eye (enopthalmos, orbital dystopia, ectropion and diplopia are avoided which simplifies the reconstruction. Most controversy is associated with the maxillectomy that involves the orbital floor and dental alveolus (Class 3. A case is made for the use of the iliac crest with internal oblique as an ideal option but there are other methods, which may provide a similar result. A multidisciplinary approach to these patients is emphasised which should include a prosthodontist with a special expertise for these defects.

  1. Create Your Plate

    Medline Plus

    Full Text Available ... In Memory In Honor Become a Member En Español Type 1 Type 2 About Us Online Community ... Page Text Size: A A A Listen En Español Create Your Plate Create Your Plate is a ...

  2. Create Your Plate

    Medline Plus

    Full Text Available ... Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal Planning ... Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets ...

  3. Create Your Plate

    Medline Plus

    Full Text Available ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart- ... Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart-Healthy Foods ...

  4. Create Your Plate

    Medline Plus

    Full Text Available ... ready, you can try new foods within each food category. Try these seven steps to get started: Using your dinner plate, put a line down the middle of the plate. Then on one side, cut it ... and starchy foods. See this list of grains and starchy foods . ...

  5. Understanding the Tectonic Features in the South China Sea By Analyzing Magnetic Anomalies

    Science.gov (United States)

    Guo, L.; Meng, X.; Shi, L.; Yao, C.

    2011-12-01

    The South China Sea (SCS) is surrounded by the Eurasia, Pacific and India-Australia plates. It formed during Late Oligocene-Early Miocene, and is one of the largest marginal seas in the Western Pacific. The collision of Indian subcontinent and Eurasian plate in the northwest, back-arc spreading in the centre and subduction beneath the Philippine plate along Manila trench in the east and along Palawan trough in the south had produced the complex tectonic features in the SCS that we can see today. In the past few decades, a variety of geophysical methods were conducted to study geological tectonics and evolution of the SCS. Here, we analyzed the magnetic data of this area using new data enhancement techniques to understand the regional tectonic features. We assembled the magnetic anomalies data with a resolution of two arc-minute from the World Digital Magnetic Anomaly Map, and then gridded the data on a regular grid. Then we used the method of reduction to the pole at low latitude with varying magnetic inclinations to stably reduce the magnetic anomalies. Then we used the preferential continuation method based on Wiener filtering and Green's equivalence principle to separate the reduced-to-pole (RTP) magnetic anomalies, and subsequently analyze the regional and residual anomalies. We also calculated the directional horizontal derivatives and the tilt-angle derivative of the data to derive clearer geological structures with more details. Then we calculated the depth of the magnetic basement surface in the area by 3D interface inversion. From the results of the preliminary processing, we analyzed the main faults, geological structures, magma distribution and tectonic features in the SCS. In the future, the integrated interpretation of the RTP magnetic anomalies, Bouguer gravity anomalies and other geophysical methods will be performed for better understanding the deep structure , the tectonic features and evolution of the South China Sea. Acknowledgment: We

  6. Developing an Education and Public Outreach (EPO) program for Caltech's Tectonics Observatory

    Science.gov (United States)

    Kovalenko, L.; Jain, K.; Maloney, J.

    2012-12-01

    The Caltech Tectonics Observatory (TO) is an interdisciplinary center, focused on geological processes occurring at the boundaries of Earth's tectonic plates (http://www.tectonics.caltech.edu). Over the past four years, the TO has made a major effort to develop an Education and Public Outreach (EPO) program. Our goals are to (1) inspire students to learn Earth Sciences, particularly tectonic processes, (2) inform and educate the general public about science in the context of TO discoveries, and (3) provide opportunities for graduate students, postdocs, and faculty to do outreach in the local K-12 schools and community colleges. Our work toward these goals includes hosting local high school teachers and students each summer for six weeks of research experience (as part of Caltech's "Summer Research Connection"); organizing and hosting an NAGT conference aimed at Geoscience teachers at community colleges; participating in teacher training workshops (organized by the local school district); hosting tours for K-12 students from local schools as well as from China; and bringing hands-on activities into local elementary, middle, and high school classrooms. We also lead local school students and teachers on geology field trips through nearby canyons; develop education modules for undergraduate classes (as part of MARGINS program); write educational web articles on TO research (http://www.tectonics.caltech.edu/outreach/highlights/), and regularly give presentations to the general public. This year, we started providing content expertise for the development of video games to teach Earth Science, being created by GameDesk Institute. And we have just formed a scientist/educator partnership with a 6th grade teacher, to help in the school district's pilot program to incorporate new national science standards (NSTA's Next Generation Science Standards, current draft), as well as use Project-Based Learning. This presentation gives an overview of these activities.

  7. Paleomagnetic Constraints on the Tectonic History of the Mesozoic Ophiolite and Arc Terranes of Western Mexico

    Science.gov (United States)

    Boschman, L.; Van Hinsbergen, D. J. J.; Langereis, C. G.; Molina-Garza, R. S.; Kimbrough, D. L.

    2017-12-01

    The North American Cordillera has been shaped by a long history of accretion of arcs and other buoyant crustal fragments to the western margin of the North American Plate since the Early Mesozoic. Accretion of these terranes resulted from a complex tectonic history interpreted to include episodes of both intra-oceanic subduction within the Panthalassa/Pacific Ocean, as well as continental margin subduction along the western margin of North America. Western Mexico, at the southern end of the Cordillera, contains a Late Cretaceous-present day long-lived continental margin arc, as well as Mesozoic arc and SSZ ophiolite assemblages of which the origin is under debate. Interpretations of the origin of these subduction-related rock assemblages vary from far-travelled exotic intra-oceanic island arc character to autochthonous or parautochthonous extended continental margin origin. We present new paleomagnetic data from four localities: (1) the Norian SSZ Vizcaíno peninsula Ophiolite; (2) its Lower Jurassic sedimentary cover; and (3) Barremian and (4) Aptian sediments derived from the Guerrero arc. The data show that the Mexican ophiolite and arc terranes have a paleolatitudinal plate motion history that is equal to that of the North American continent. This suggests that these rock assemblages were part of the overriding plate and were perhaps only separated from the North American continent by temporal fore- or back-arc spreading. These spreading phases resulted in the temporal existence of tectonic plates between the North American and Farallon Plates, and upon closure of the basins, in the growth of the North American continent without addition of any far-travelled exotic terranes.

  8. New Ages for Gorgona Island, Colombia: Implications for Previous Petrogenetic and Tectonic Models

    Science.gov (United States)

    Serrano Duran, L.; Lopez Martinez, M.; Ferrari, L.

    2007-05-01

    The Gorgona Island, located 50 km to the west of the Colombian Pacific coast, is the only known site with Phanerozoic komatiites in the world besides a key element in several reconstruction of the interaction between the Caribbean and the South America Plate. The Gorgona komatiites are part of an igneous complex that also includes picritic basalts and breccias, gabbros and peridotites (dunites and wherlites), and is covered by deformed mid-Eocene and younger underformed marine sediments. Datings of the igneous rocks were only performed on basalts and include an 86 Ma K-Ar age, an 88.9 ± 1.2 Ma weighted mean of four Ar-Ar ages and an 89.2 ± 5.2 Ma Re-Os isochron age from basalts. Gorgona rocks are affected by reverse faulting with a general eastward vergence. The island is the only subaerially exposed part of a NE elongated sliver accreted in a dextral transpressional regime to the South America continental margin between the Late Eocene and the Early Miocene. Petrologic studies found large spread in radiogenic isotopes and incompatible trace element ratios in Gorgona ultramafic rocks, which have been interpreted as requiring at least two different sources of: 1) a depleted mantle responsible for the generation of the komatiites and most basalts, and 2) an enriched mantle responsible for some rarer enriched basalts and picrites. Despite the large compositional and isotopic heterogeneity the most common interpretation is that the Gorgona ultramafic rocks are the product of a single mantle plume, although it has recently proposed that this would be a separate plume from that generating the bulk of the Caribbean plateau at ~90 Ma. Our new study focused on the geochronology of the Gorgona igneous suite as we consider that this tectonically and petrologically complex island is unlike to have such a narrow age range. We attempted to date eight samples of komatiites, basalts and gabbros by Ar-Ar laser step heating. For four of these samples we successfully obtain

  9. Towards stacked zone plates

    International Nuclear Information System (INIS)

    Werner, S; Rehbein, S; Guttman, P; Heim, S; Schneider, G

    2009-01-01

    Fresnel zone plates are the key optical elements for soft and hard x-ray microscopy. For short exposure times and minimum radiation load of the specimen the diffraction efficiency of the zone plate objectives has to be maximized. As the efficiency strongly depends on the height of the diffracting zone structures the achievable aspect ratio of the nanostructures determines these limits. To reach aspect ratios ≥ 20:1 for high efficient optics we propose to superimpose zone plates on top of each other. With this multiplication approach the final aspect ratio is only limited by the number of stacked zone plate layers. For the stack process several nanostructuring process steps have to be developed and/or improved. Our results show for the first time two layers of zone plates stacked on top of each other.

  10. Tectonic and climatic considerations for deep geological disposal of radioactive waste: A UK perspective

    International Nuclear Information System (INIS)

    McEvoy, F.M.; Schofield, D.I.; Shaw, R.P.; Norris, S.

    2016-01-01

    Identifying and evaluating the factors that might impact on the long-term integrity of a deep Geological Disposal Facility (GDF) and its surrounding geological and surface environment is central to developing a safety case for underground disposal of radioactive waste. The geological environment should be relatively stable and its behaviour adequately predictable so that scientifically sound evaluations of the long-term radiological safety of a GDF can be made. In considering this, it is necessary to take into account natural processes that could affect a GDF or modify its geological environment up to 1 million years into the future. Key processes considered in this paper include those which result from plate tectonics, such as seismicity and volcanism, as well as climate-related processes, such as erosion, uplift and the effects of glaciation. Understanding the inherent variability of process rates, critical thresholds and likely potential influence of unpredictable perturbations represent significant challenges to predicting the natural environment. From a plate-tectonic perspective, a one million year time frame represents a very short segment of geological time and is largely below the current resolution of observation of past processes. Similarly, predicting climate system evolution on such time-scales, particularly beyond 200 ka AP is highly uncertain, relying on estimating the extremes within which climate and related processes may vary with reasonable confidence. The paper highlights some of the challenges facing a deep geological disposal program in the UK to review understanding of the natural changes that may affect siting and design of a GDF. - Highlights: • Natural processes are key to developing a safety case for geological disposal. • Key factors include plate tectonic and climate-mediated processes. • Process variability is a challenge to predicting the natural environment. • We highlight the challenges for geological disposal programs using

  11. Geomorphology and Neogene tectonic evolution of the Palomares continental margin (Western Mediterranean)

    Science.gov (United States)

    Gómez de la Peña, Laura; Gràcia, Eulàlia; Muñoz, Araceli; Acosta, Juan; Gómez-Ballesteros, María; R. Ranero, César; Uchupi, Elazar

    2016-10-01

    The Palomares continental margin is located in the southeastern part of Spain. The margin main structure was formed during Miocene times, and it is currently part of the wide deformation zone characterizing the region between the Iberian and African plates, where no well-defined plate boundary occurs. The convergence between these two plates is here accommodated by several structures, including the left lateral strike-slip Palomares Fault. The region is characterized by sparse, low to moderate magnitude (Mw shallow instrumental earthquakes, although large historical events have also occurred. To understand the recent tectonic history of the margin we analyze new high-resolution multibeam bathymetry data and re-processed three multichannel seismic reflection profiles crossing the main structures. The analysis of seafloor morphology and associated subsurface structure provides new insights of the active tectonic features of the area. In contrast to other segments of the southeastern Iberian margin, the Palomares margin contains numerous large and comparatively closely spaced canyons with heads that reach near the coast. The margin relief is also characterized by the presence of three prominent igneous submarine ridges that include the Aguilas, Abubacer and Maimonides highs. Erosive processes evidenced by a number of scars, slope failures, gullies and canyon incisions shape the present-day relief of the Palomares margin. Seismic images reveal the deep structure distinguishing between Miocene structures related to the formation of the margin and currently active features, some of which may reactivate inherited structures. The structure of the margin started with an extensional phase accompanied by volcanic accretion during the Serravallian, followed by a compressional pulse that started during the Latemost Tortonian. Nowadays, tectonic activity offshore is subdued and limited to few, minor faults, in comparison with the activity recorded onshore. The deep Algero

  12. Tectonic and climatic considerations for deep geological disposal of radioactive waste: A UK perspective

    Energy Technology Data Exchange (ETDEWEB)

    McEvoy, F.M., E-mail: fmcevoy@bgs.ac.uk [British Geological Survey, Keyworth, Nottingham NG12 5GG (United Kingdom); Schofield, D.I. [British Geological Survey, Tongwynlais, CF15 7NE (United Kingdom); Shaw, R.P. [British Geological Survey, Keyworth, Nottingham NG12 5GG (United Kingdom); Norris, S. [Radioactive Waste Management Limited, B587, Curie Avenue, Harwell, Didcot OX11 0RH (United Kingdom)

    2016-11-15

    Identifying and evaluating the factors that might impact on the long-term integrity of a deep Geological Disposal Facility (GDF) and its surrounding geological and surface environment is central to developing a safety case for underground disposal of radioactive waste. The geological environment should be relatively stable and its behaviour adequately predictable so that scientifically sound evaluations of the long-term radiological safety of a GDF can be made. In considering this, it is necessary to take into account natural processes that could affect a GDF or modify its geological environment up to 1 million years into the future. Key processes considered in this paper include those which result from plate tectonics, such as seismicity and volcanism, as well as climate-related processes, such as erosion, uplift and the effects of glaciation. Understanding the inherent variability of process rates, critical thresholds and likely potential influence of unpredictable perturbations represent significant challenges to predicting the natural environment. From a plate-tectonic perspective, a one million year time frame represents a very short segment of geological time and is largely below the current resolution of observation of past processes. Similarly, predicting climate system evolution on such time-scales, particularly beyond 200 ka AP is highly uncertain, relying on estimating the extremes within which climate and related processes may vary with reasonable confidence. The paper highlights some of the challenges facing a deep geological disposal program in the UK to review understanding of the natural changes that may affect siting and design of a GDF. - Highlights: • Natural processes are key to developing a safety case for geological disposal. • Key factors include plate tectonic and climate-mediated processes. • Process variability is a challenge to predicting the natural environment. • We highlight the challenges for geological disposal programs using

  13. Integrating EarthScope Data to Constrain the Long-Term Effects of Tectonism on Continental Lithosphere

    Science.gov (United States)

    Porter, R. C.; van der Lee, S.

    2017-12-01

    One of the most significant products of the EarthScope experiment has been the development of new seismic tomography models that take advantage of the consistent station design, regular 70-km station spacing, and wide aperture of the EarthScope Transportable Array (TA) network. These models have led to the discovery and interpretation of additional compositional, thermal, and density anomalies throughout the continental US, especially within tectonically stable regions. The goal of this work is use data from the EarthScope experiment to better elucidate the temporal relationship between tectonic activity and seismic velocities. To accomplish this, we compile several upper-mantle seismic velocity models from the Incorporated Research Institute for Seismology (IRIS) Earth Model Collaboration (EMC) and compare these to a tectonic age model we compiled using geochemical ages from the Interdisciplinary Earth Data Alliance: EarthChem Database. Results from this work confirms quantitatively that the time elapsed since the most recent tectonic event is a dominant influence on seismic velocities within the upper mantle across North America. To further understand this relationship, we apply mineral-physics models for peridotite to estimate upper-mantle temperatures for the continental US from tomographically imaged shear velocities. This work shows that the relationship between the estimated temperatures and the time elapsed since the most recent tectonic event is broadly consistent with plate cooling models, yet shows intriguing scatter. Ultimately, this work constrains the long-term thermal evolution of continental mantle lithosphere.

  14. 3D monitoring of active tectonic structures

    Czech Academy of Sciences Publication Activity Database

    Stemberk, Josef; Košťák, Blahoslav; Vilímek, V.

    2003-01-01

    Roč. 36, 1-2 (2003), s. 103-112 ISSN 0264-3707 R&D Projects: GA MŠk OC 625.10 Institutional research plan: CEZ:AV0Z3046908 Keywords : tectonics * monitoring * active structures Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.754, year: 2003

  15. Discriminating four tectonic settings: Five new geochemical ...

    Indian Academy of Sciences (India)

    of basic and ultrabasic rocks from four tectonic settings of island arc, continental rift, ocean-island, and mid-ocean ridge. These diagrams were ...... 9. Macdonald et al (1995). 8. 1. 35.9. 3.7. Kenya, Turkana Rift (Bird Nest,. Central). 3 ...... reproduction in diverse applications. 4.2 Comparison of linear discriminant analysis.

  16. Venus tectonics: another Earth or another Mars

    International Nuclear Information System (INIS)

    McGill, G.E.

    1979-01-01

    The presence of presumably primordial large craters has led to the suggestion that Venus may have a thick lithosphere like that of Mars despite its similarities to Earth in size and density. However, crust and upper mantle temperatures on Venus are very likely higher than on Earth so that a dry Venus could have a lithosphere with a thickness similar to that of Earth. If a trace of volatiles is present in the mantle, the lithosphere of Venus could be thinner. Due to the absence of liquid water, erosion and deposition will be much slower on Venus than on Earth, favoring retention of primordial cratered surfaces on portions of the crust that have not been destroyed or buried by tectonic and volcanic activity. Geochemical models of solar system origin and petrological considerations suggest that K is about as abundant in Venus as in Earth. The abundance of 40 Ar in the atmosphere of Venus lies somewhere between the Earth value and one-tenth of the Earth value. Because erosional liberation of 40 Ar on Venus will be relatively inefficient, this range for 40 Ar abundance at least permits an active tectonic history, and if the 40 Ar abundance is towards the high end of the range, it may well require an active tectonic history. Thus we are not constrained to a Mars-like model of Venus tectonics by craters and possible mantle dryness; an Earth-like model is equally probable

  17. Tectonic studies in the Lansjaerv region

    International Nuclear Information System (INIS)

    Henkel, H.

    1987-10-01

    This report contains the results and the analysis of ground geophysical measurements and the tectonic interpretation in the 150x200 km Lansjaerv study area. It describes the data and methods used. The significance of strike slip fault patterns in relation to the surface morphology is discussed. The obtained results are used to suggest a tentative model for the present tectonic deformation. The report is part of the bedrock stability programme of SKB. The major conclusions regarding the tectonic structure are: Three regional fault systems are identified, two steep NW and N trending and a third NNE trending with gentle ESE dips, the steep fault systems have strike slip generated deformation patterns both in the Precambrian structures and in the surface morphology, the post-glacial faults of the area are part of this fault pattern and represent movements mainly on reactivated, gently dipping zones, several suspected late or post-glacial, fault related features are found along the steep NW and N faults. Sites for drilling and geodetic networks for deformation measurements are suggested. Detailed background data are documented in additional 4 reports. The basic geophysical and geological datasets are documented in color plotted 1:250 000 maps. A tectonic interpretation map in the same scale has been produced by combined interpretation of magnetic, elevation, elevation relief and gravity data. (orig./HP) With 6 maps

  18. Earthquakes and Tectonics Expert Judgment Elicitation Project

    International Nuclear Information System (INIS)

    Coppersmith, K.J.; Perman, R.C.; Youngs, R.R.

    1993-02-01

    This report summarizes the results of the Earthquakes and Tectonics Expert Judgement Excitation Project sponsored by the Electric Power Research Institute (EPRI). The objectives of this study were two-fold: (1) to demonstrate methods for the excitation of expert judgement, and (2) to quantify the uncertainties associated with earthquake and tectonics issues for use in the EPRI-HLW performance assessment. Specifically, the technical issue considered is the probability of differential fault displacement through the proposed repository at Yucca Mountain, Nevada. For this study, a strategy for quantifying uncertainties was developed that relies on the judgements of multiple experts. A panel of seven geologists and seismologists was assembled to quantify the uncertainties associated with earthquake and tectonics issues for the performance assessment model. A series of technical workshops focusing on these issues were conducted. Finally, each expert was individually interviewed in order to elicit his judgement regarding the technical issues and to provide the technical basis for his assessment. This report summarizes the methodologies used to elicit the judgements of the earthquakes and tectonics experts (termed ''specialists''), and summarizes the technical assessments made by the expert panel

  19. Tectonic vocabulary and materialization: Discourse on the future of tectonic architectural research in the Nordic countries

    DEFF Research Database (Denmark)

    Beim, Anne; Bundgaard, Charlotte; Hvejsel, Marie Frier

    2015-01-01

    By referring to the fundamental question of how we unite aesthetics and technology – tectonic theory is necessarily a focal point in the development of the architectural discipline. However, a critical reconsideration of the role of tectonic theory seems necessary when facing the present everyday....... On the occasion of the Second International Conference on Structures & Architecture held in July 2013 in Portugal the authors organized a special session entitled From open structures to the cladding of control bringing together researchers from the Nordic countries to discuss this issue. Likewise the initiative...... to establish a Nordic Network for Research and Teaching in Tectonics is currently forming. This paper seeks to jointly reflect upon these initiatives in order to bring them further, with the intention to clad a discourse on the future of tectonic architectural research that addresses the conditions of everyday...

  20. Stress states in the Zagros fold-and-thrust belt from passive margin to collisional tectonic setting

    Science.gov (United States)

    Navabpour, Payman; Barrier, Eric

    2012-12-01

    The present-day Zagros fold-and-thrust belt of SW-Iran corresponds to the former Arabian passive continental margin of the southern Neo-Tethyan basin since the Permian-Triassic rifting, undergoing later collisional deformation in mid-late Cenozoic times. In this paper an overview of brittle tectonics and palaeostress reconstructions of the Zagros fold-and-thrust belt is presented, based on direct stress tensor inversion of fault slip data. The results indicate that, during the Neo-Tethyan oceanic opening, an extensional tectonic regime affectedthe sedimentary cover in Triassic-Jurassic times with an approximately N-S trend of the σ3 axis, oblique to the margin, which was followed by some local changes to a NE-SW trend during Jurassic-Cretaceous times. The stress state significantly changed to thrust setting, with a NE-SW trend of the σ1 axis, and a compressional tectonic regime prevailed during the continental collision and folding of the sedimentary cover in Oligocene-Miocene times. This compression was then followed by a strike-slip stress state with an approximately N-S trend of the σ1 axis, oblique to the belt, during inversion of the inherited extensional basement structures in Pliocene-Recent times. The brittle tectonic reconstructions, therefore, highlighted major changes of the stress state in conjunction with transitions between thin- and thick-skinned structures during different extensional and compressional stages of continental deformation within the oblique divergent and convergent settings, respectively.

  1. Transient magmatic control in a tectonic domain: the central Aeolian volcanic arc (South Italy)

    KAUST Repository

    Ruch, Joel; Vezzoli, Luigina; Di Lorenzo, Riccardo; De Rosa, Rosanna; Acocella, Valerio

    2015-01-01

    The background stress field in volcanic areas may be overprinted by that produced by transient magmatic intrusions, generating local faulting. These events are rarely monitored and thus not fully understood, generating debate about the role of magma and tectonics in any geodynamic setting. Here we carried out a field structural analysis on the NNW-SSE strike-slip system of the central Aeolian Arc, Italy (Lipari and Vulcano islands) with ages constrained by stratigraphy to better capture the tectonic and magmatic evolution at the local and regional scales. We consider both islands as a single magmatic system and define 5 principal stratigraphic units based on magmatic and tectonic activity. We collected >500 measurements of faults, extension fractures and dikes at 40 sites, mostly NNE-SSW to NNW-SSE oriented with a dominant NS orientation. These structures are governed quasi exclusively by pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral slip, the latter being mostly related to old deposits (>50 ka). We further reconstructed the evolution of the Vulcano-Lipari system during the last ~20 ka and find that it consists of an overall half-graben-like structure, with faults with predominant eastward dips. Field evidence suggests that faulting occurs often in temporal and spatial relation with magmatic events, suggesting that most of the observable deformation derived from transient magmatic activity, rather than from steady regional tectonics. To explain the dominant magmatic and episodic extension in a tectonic dominant domain, we propose a model where the regional N-S trending maximum horizontal stress, responsible for strike-slip activity, locally rotates to vertical in response to transient pressurization of the magmatic system and magma rise below Lipari and Vulcano. This has possibly generated the propagation of N-S trending dikes in the past 1 ka along a 10 km long by 1 km wide crustal corridor, with important

  2. Transient magmatic control in a tectonic domain: the central Aeolian volcanic arc (South Italy)

    KAUST Repository

    Ruch, Joel

    2015-04-01

    The background stress field in volcanic areas may be overprinted by that produced by transient magmatic intrusions, generating local faulting. These events are rarely monitored and thus not fully understood, generating debate about the role of magma and tectonics in any geodynamic setting. Here we carried out a field structural analysis on the NNW-SSE strike-slip system of the central Aeolian Arc, Italy (Lipari and Vulcano islands) with ages constrained by stratigraphy to better capture the tectonic and magmatic evolution at the local and regional scales. We consider both islands as a single magmatic system and define 5 principal stratigraphic units based on magmatic and tectonic activity. We collected >500 measurements of faults, extension fractures and dikes at 40 sites, mostly NNE-SSW to NNW-SSE oriented with a dominant NS orientation. These structures are governed quasi exclusively by pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral slip, the latter being mostly related to old deposits (>50 ka). We further reconstructed the evolution of the Vulcano-Lipari system during the last ~20 ka and find that it consists of an overall half-graben-like structure, with faults with predominant eastward dips. Field evidence suggests that faulting occurs often in temporal and spatial relation with magmatic events, suggesting that most of the observable deformation derived from transient magmatic activity, rather than from steady regional tectonics. To explain the dominant magmatic and episodic extension in a tectonic dominant domain, we propose a model where the regional N-S trending maximum horizontal stress, responsible for strike-slip activity, locally rotates to vertical in response to transient pressurization of the magmatic system and magma rise below Lipari and Vulcano. This has possibly generated the propagation of N-S trending dikes in the past 1 ka along a 10 km long by 1 km wide crustal corridor, with important

  3. Modeling tectonic heat flow and source rock maturity in the Rub' Al-Khali Basin (Saudi Arabia), with the help of GOCE satellite gravity data

    NARCIS (Netherlands)

    Abdul Fattah, R.; Meekes, S.; Bouman, J.; Ebbing, J.; Haagmans, R.

    2014-01-01

    A 3D basin modeling study was carried out to reconstruct the regional heat flow and source rock maturity in the Rub'al-Khali basin. Gravity gradient data from the GOCE satellite were used to model deep structures, such as the Moho interface. Tectonic heat flow was modeled using the GOCE-based Moho

  4. Deformation of the Northwestern Okhotsk Plate: How is it happening?

    Science.gov (United States)

    Hindle, D.; Fujita, K.; Mackey, K.

    2009-09-01

    The Eurasia (EU) - North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on the EU-OK-NA triple junction and is thus caught and compressed between converging EU and NA. We suggest that this leads to a coherent and understandable large scale deformation pattern of mostly northwest-southeast trending strike-slip faults which split Northwest OK into several extruding slivers. When the fault geometry is analysed together with space geodetic and focal mechanism data it suggests a central block which is extruding faster bordered east and west by progressively slower extruding blocks until the OK plate boundary faults are encountered. Taking into account elastic loading from both the intra-OK faults and the OK-Pacific (PA) boundary reconciles geodetic motions with geologic slip rates on at least the OK-NA boundary which corresponds to the Ulakhan fault.

  5. Kinematics and age of Early Tertiary trench parallel volcano-tectonic lineaments in southern Mexico: Tectonic implications

    Science.gov (United States)

    Martini, M.; Ferrari, L.; Lopez Martinez, M.; Cerca Martinez, M.; Serrano Duran, L.

    2007-05-01

    We present new geological, structural, and geochronological data that constrain the timing and geometry of Early Tertiary strike slip deformation in southwestern Mexico and its relation with the concurrent magmatic activity. Geologic mapping in Guerrero and Michoacan States documented two regional WNW trending volcano-tectonic lineaments sub parallel to the present trench. The southernmost lineament runs for ~140 km from San Miguel Totolapan area (NW Guerrero) to Sanchiqueo (SE Michoacan), and passes through Ciudad Altamirano. Its southeastern part is marked by the alignment of at least eleven silicic to intermediate major domes as well as by the course of the Balsas River. The northwestern part of the lineament is characterized by ductile left lateral shear zones in Early Tertiary plutonic rocks observed in the Rio Chiquito valley. Domes near Ciudad Altamirano are unaffected by ductile shearing and yielded a ~42 Ma 40Ar/39Ar age, setting a minimum age for this deformation. The northern volcano-tectonic lineament runs for ~190 km between the areas of Huitzuco in northern Guerrero and the southern part of the Tzitzio fold in eastern Michoacan. The Huautla, Tilzapotla, Taxco, La Goleta and Nanchititla silicic centers (all in the range 37-34 Ma) are emplaced along this lineament, which continues to the WNW trough a mafic dike swarm exposed north of Tiquicheo (37-35 Ma) and the Purungueo subvolcanic body (~42 Ma). These rocks, unaffected by ductile shearing, give a minimum age of deformation similar to the southern Totolapan-Sanquicheo lineament. Post ~42 Ma deformation is essentially brittle and is characterized by several left lateral and right lateral transcurrent faults with typical Riedel patterns. Other trench-parallel left lateral shear zones active in pre-Oligocene times were recently reported in western Oaxaca. The recognizing of Early Tertiary trench-parallel and left-lateral ductile shearing in internal areas of southern Mexico suggest a field of widely

  6. Global Plate Velocities from the Global Positioning System

    Science.gov (United States)

    Larson, Kristine M.; Freymueller, Jeffrey T.; Philipsen, Steven

    1997-01-01

    We have analyzed 204 days of Global Positioning System (GPS) data from the global GPS network spanning January 1991 through March 1996. On the basis of these GPS coordinate solutions, we have estimated velocities for 38 sites, mostly located on the interiors of the Africa, Antarctica, Australia, Eurasia, Nazca, North America, Pacific, and South America plates. The uncertainties of the horizontal velocity components range from 1.2 to 5.0 mm/yr. With the exception of sites on the Pacific and Nazca plates, the GPS velocities agree with absolute plate model predictions within 95% confidence. For most of the sites in North America, Antarctica, and Eurasia, the agreement is better than 2 mm/yr. We find no persuasive evidence for significant vertical motions (less than 3 standard deviations), except at four sites. Three of these four were sites constrained to geodetic reference frame velocities. The GPS velocities were then used to estimate angular velocities for eight tectonic plates. Absolute angular velocities derived from the GPS data agree with the no net rotation (NNR) NUVEL-1A model within 95% confidence except for the Pacific plate. Our pole of rotation for the Pacific plate lies 11.5 deg west of the NNR NUVEL-1A pole, with an angular speed 10% faster. Our relative angular velocities agree with NUVEL-1A except for some involving the Pacific plate. While our Pacific-North America angular velocity differs significantly from NUVEL-1A, our model and NUVEL-1A predict very small differences in relative motion along the Pacific-North America plate boundary itself. Our Pacific-Australia and Pacific- Eurasia angular velocities are significantly faster than NUVEL-1A, predicting more rapid convergence at these two plate boundaries. Along the East Pacific Pise, our Pacific-Nazca angular velocity agrees in both rate and azimuth with NUVFL-1A.

  7. Anisotropic elastic plates

    CERN Document Server

    Hwu, Chyanbin

    2010-01-01

    As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a

  8. High loading uranium plate

    International Nuclear Information System (INIS)

    Wiencek, T.C.; Domagala, R.F.; Thresh, H.R.

    1990-01-01

    Two embodiments of a high uranium fuel plate are disclosed which contain a meat comprising structured uranium compound confined between a pari of diffusion bonded ductile metal cladding plates uniformly covering the meat, the meat hiving a uniform high fuel loading comprising a content of uranium compound greater than about 45 Vol. % at a porosity not greater than about 10 Vol. %. In a first embodiment, the meat is a plurality of parallel wires of uranium compound. In a second embodiment, the meat is a dispersion compact containing uranium compound. The fuel plates are fabricated by a hot isostatic pressing process

  9. Heat insulating plates

    Energy Technology Data Exchange (ETDEWEB)

    Allan, J.A.F.

    1976-10-28

    Micro-porous insulation plates are dealt with, for example, how they are used in the insulation of heat storage devices. Since one side of such plates is exposed to a temperature of over 700/sup 0/C, a shrinkage of the glass texture of the covering can occur, which can exceed the shrinkage of the inner micro-porous material, so that cracks and splits in the high temperature side of the covering can come about. The task of the invention is to design the plate in such a way as to prevent this from happening. For this purpose the plate is provided, according to invention specifications, with flutes, waves, ribs, waffle or grid patterns and the covering is set into the recesses originating from this.

  10. Create Your Plate

    Medline Plus

    Full Text Available ... Plate is a simple and effective way to manage your blood glucose levels and lose weight. With ... been easier. It can be a challenge to manage portion control wherever you are. Now, our best- ...

  11. Create Your Plate

    Medline Plus

    Full Text Available ... Food Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart-Healthy Foods donate en -- A Future Without Diabetes - a- ...

  12. Create Your Plate

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    Full Text Available ... Risk Test Lower Your Risk Healthy Eating Overweight Smoking High Blood Pressure Physical Activity High Blood Glucose ... Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart- ...

  13. Create Your Plate

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    Full Text Available ... Risk Test Lower Your Risk Healthy Eating Overweight Smoking High Blood Pressure Physical Activity High Blood Glucose ... Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets ...

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    Full Text Available ... Children and Type 2 Diabetes Know Your Rights Employment Discrimination Health Care Professionals Law Enforcement Driver's License ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  15. Create Your Plate

    Medline Plus

    Full Text Available ... diabetes. Other Ways to Give Become a Member Vehicle Donation Planned Giving Options Memorial Giving Brochures & Envelopes ... to manage your blood glucose levels and lose weight. With this method, you fill your plate with ...

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    Full Text Available ... breast cancer and AIDS combined. Your gift today will help us get closer to curing diabetes and ... on one side, cut it again so you will have three sections on your plate. Fill the ...

  17. Create Your Plate

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    Full Text Available ... Recipes Association Cookbook Recipes Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning ... serving of dairy or both as your meal plan allows. Choose healthy fats in small amounts. For ...

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    Full Text Available ... Count Glycemic Index Low-Calorie Sweeteners Sugar and Desserts Fitness Exercise & Type 1 Diabetes Get Started Safely ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  19. Create Your Plate

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    Full Text Available ... these seven steps to get started: Using your dinner plate, put a line down the middle of ... Fitness Food Recipes Planning Meals What Can I Eat Weight Loss Fitness In My Community Calendar of ...

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    Full Text Available ... Food MyFoodAdvisor Recipes Association Cookbook Recipes Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal ...

  1. Create Your Plate

    Medline Plus

    Full Text Available ... for Association Events Messaging Tools Recruiting Advocates Local Market Planning Training Webinars News & Events Advocacy News Call ... Meals > Create Your Plate Share: Print Page Text Size: A A A Listen En Español Create Your ...

  2. Create Your Plate

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  3. Create Your Plate

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  4. Create Your Plate

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    Full Text Available ... 800-342-2383) Give by Mail Close ... your plate with more non-starchy veggies and smaller portions of starchy foods and protein—no special tools or counting required! You can ...

  5. Humvee Armor Plate Drilling

    National Research Council Canada - National Science Library

    2004-01-01

    When drilling holes in hard steel plate used in up-armor kits for Humvee light trucks, the Anniston Army Depot, Anniston, Alabama, requested the assistance of the National Center for Defense Manufacturing and Machining (NCDMM...

  6. Create Your Plate

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    Full Text Available ... Easy Advocacy Checklists for Association Events Messaging Tools Recruiting Advocates Local Market Planning Training Webinars News & Events ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  7. Create Your Plate

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    Full Text Available ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ... Complications Health Insurance For Parents & Kids Know Your Rights We Can Help Enroll in the Living WIth ...

  8. Create Your Plate

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    Full Text Available ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ... today and help fund grants supporting next generation scientists. Donate Today We Can Help - we-can-help. ...

  9. Morphological expression of active tectonics in the Southern Alps

    Science.gov (United States)

    Robl, Jörg; Heberer, Bianca; Neubauer, Franz; Hergarten, Stefan

    2015-04-01

    Evolving drainage pattern and corresponding metrics of the channels (e.g. normalized steepness index) are sensitive indicators for tectonic or climatic events punctuating the evolution of mountain belts and their associated foreland basins. The analysis of drainage systems and their characteristic properties represents a well-established approach to constrain the impact of tectonic and climatic drivers on mountainous landscapes in the recent past. The Southern Alps (SA) are one of the seismically most active zones in the periphery of northern Adria. Recent deformation is caused by the ongoing convergence of the Adriatic and European plate and is recorded by numerous earthquakes in the domain of the SA. Deformation in the SA is characterized by back-thrusting causing crustal thickening and should therefore result in uplift and topography formation. The vertical velocity field determined by GPS-data clearly indicates a belt of significant uplift in the south South alpine indenter between Lake Garda in the west and the Triglav in the east and strong subsidence of the foreland basin surrounding the Mediterranean Sea near Venice, although subsidence is often related to ongoing subduction of the Adriatic microplate underneath Appennines. Despite of these short term time series, timing, rates and drivers of alpine landscape evolution are not well constrained and the linkage between crustal deformation and topographic evolution of this highly active alpine segment remains unclear for the following reasons: (1) The eastern Southern Alps were heavily overprinted by the Pleistocene glaciations and tectonic signals in the alpine landscape are blurred. Only the transition zone to the southern foreland basin remained unaffected and allows an analysis of a glacially undisturbed topography. (2) The major part of this domain is covered by lithology (carbonatic rocks) which is unsuitable for low temperature geochronology and cosmogenic isotope dating so that exhumation and erosion

  10. BAO Plate Archive Project

    Science.gov (United States)

    Mickaelian, A. M.; Gigoyan, K. S.; Gyulzadyan, M. V.; Paronyan, G. M.; Abrahamyan, H. V.; Andreasyan, H. R.; Azatyan, N. M.; Kostandyan, G. R.; Samsonyan, A. L.; Mikayelyan, G. A.; Farmanyan, S. V.; Harutyunyan, V. L.

    2017-12-01

    We present the Byurakan Astrophysical Observatory (BAO) Plate Archive Project that is aimed at digitization, extraction and analysis of archival data and building an electronic database and interactive sky map. BAO Plate Archive consists of 37,500 photographic plates and films, obtained with 2.6m telescope, 1m and 0.5m Schmidt telescopes and other smaller ones during 1947-1991. The famous Markarian Survey (or the First Byurakan Survey, FBS) 2000 plates were digitized in 2002-2005 and the Digitized FBS (DFBS, www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on this low-dispersion spectroscopic material. Several other smaller digitization projects have been carried out as well, such as part of Second Byurakan Survey (SBS) plates, photographic chain plates in Coma, where the blazar ON 231 is located and 2.6m film spectra of FBS Blue Stellar Objects. However, most of the plates and films are not digitized. In 2015, we have started a project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage. Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) database will accommodate all new data. The project runs in collaboration with the Armenian Institute of Informatics and Automation Problems (IIAP) and will continues during 4 years in 2015-2018. The final result will be an Electronic Database and online Interactive Sky map to be used for further research projects. ArVO will provide all standards and tools for efficient usage of the scientific output and its integration in international databases.

  11. Tectonics of the southern escarpment of Ishtar Terra on Venus from observations of morphology and gravity

    International Nuclear Information System (INIS)

    Janle, P.; Jannsen, D.

    1984-01-01

    Maxima of calculated topographical line-of-sight (LOS) gravity attractions caused by Ishtar Terra are shifted to the north with respect to the measured LOS free air gravity maxima south of the highland. This implies a tendency to isostatic compensation of central Ishtar and mass surpluses at the continental border and the southern forelands. The authors present a scenario compatible with the interpretation of the gravity anomalies and morphological features. The existence of global plate tectonics on Venus like on Earth is not necessarily implied, but at least limited horizontal movements of the Venusian lithosphere seem to be likely. This result shows that plate recycling must be considered for heat transfer through the lithosphere beside conduction and hot spot volcanism. (Auth.)

  12. Neutron imaging plates

    International Nuclear Information System (INIS)

    Niimura, Nobuo

    1995-01-01

    Imaging plates have been used in the field of medical diagnosis since long ago, but their usefulness was verified as the two-dimensional detector for analyzing the X-ray crystalline structure of high bio molecules like protein, and they have contributed to the remarkable progress in this field. The great contribution is due to the excellent features, such as the detection efficiency of about 100%, the positional resolution smaller than 0.2 mm, the dynamic range of five digits, and the area of several hundreds mm square. The neutron imaging plates have not yet obtained the sufficient results. It was planned to construct the neutron diffractometer for biological matters, and to put imaging plate neutron detectors (IP-ND) to practical use as the detector. The research on the development of IP-NDs was carried out, and the IPp-NDs having the performance comparable with that for X-ray were able to be produced. Imaging plates are the integral type two-dimensional radiation detector using photostimulated luminescence matters, and their principle is explained. As to neutron imaging plates, the converter, neutron detection efficiency and the flight of secondary particles in photo-stimulated luminescence matters are described. As for the present state of development of neutron imaging plates, the IP-NDs made for trial, the dynamic range, the positional resolution, the detection efficiency and the kinds of converters, and the application of IP-NDs are reported. (K.I.)

  13. Earthquakes, Cities, and Lifelines: lessons integrating tectonics, society, and engineering in middle school Earth Science

    Science.gov (United States)

    Toke, N.; Johnson, A.; Nelson, K.

    2010-12-01

    Earthquakes are one of the most widely covered geologic processes by the media. As a result students, even at the middle school level, arrive in the classroom with preconceptions about the importance and hazards posed by earthquakes. Therefore earthquakes represent not only an attractive topic to engage students when introducing tectonics, but also a means to help students understand the relationships between geologic processes, society, and engineering solutions. Facilitating understanding of the fundamental connections between science and society is important for the preparation of future scientists and engineers as well as informed citizens. Here, we present a week-long lesson designed to be implemented in five one hour sessions with classes of ~30 students. It consists of two inquiry-based mapping investigations, motivational presentations, and short readings that describe fundamental models of plate tectonics, faults, and earthquakes. The readings also provide examples of engineering solutions such as the Alaskan oil pipeline which withstood multi-meter surface offset in the 2002 Denali Earthquake. The first inquiry-based investigation is a lesson on tectonic plates. Working in small groups, each group receives a different world map plotting both topography and one of the following data sets: GPS plate motion vectors, the locations and types of volcanoes, the location of types of earthquakes. Using these maps and an accompanying explanation of the data each group’s task is to map plate boundary locations. Each group then presents a ~10 minute summary of the type of data they used and their interpretation of the tectonic plates with a poster and their mapping results. Finally, the instructor will facilitate a class discussion about how the data types could be combined to understand more about plate boundaries. Using student interpretations of real data allows student misconceptions to become apparent. Throughout the exercise we record student preconceptions

  14. Public regulations towards a tectonic architecture

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due

    2006-01-01

    's activities has primarily been to support the optimization of the building process through ‘trimmed building’ and ‘partnering’ that only takes the immediate economic benefits of the changes to the building process into account and as such has no measures for architectural quality. The public initiatives so......Public regulations can support tectonic architecture by changes to the tendering system, supporting new organizational structures of the building industry in public building projects and suggesting a focus on innovation through increased research and development activity. The Danish state...... are happening very slowly which is understandable when there is no economic incitement for the industry to change. A change of these public regulations from sticks to carrots could create the economic incitement for the building industry to create tectonic architecture and thereby develop the building industry...

  15. PET reconstruction

    International Nuclear Information System (INIS)

    O'Sullivan, F.; Pawitan, Y.; Harrison, R.L.; Lewellen, T.K.

    1990-01-01

    In statistical terms, filtered backprojection can be viewed as smoothed Least Squares (LS). In this paper, the authors report on improvement in LS resolution by: incorporating locally adaptive smoothers, imposing positivity and using statistical methods for optimal selection of the resolution parameter. The resulting algorithm has high computational efficiency relative to more elaborate Maximum Likelihood (ML) type techniques (i.e. EM with sieves). Practical aspects of the procedure are discussed in the context of PET and illustrations with computer simulated and real tomograph data are presented. The relative recovery coefficients for a 9mm sphere in a computer simulated hot-spot phantom range from .3 to .6 when the number of counts ranges from 10,000 to 640,000 respectively. The authors will also present results illustrating the relative efficacy of ML and LS reconstruction techniques

  16. Gneiss Macuira: tectonic evolution of Paleozoic metamorphic rocks of the Alta Guajira, Colombia

    International Nuclear Information System (INIS)

    Lopez I; A Julian; Zuluaga C; A, Carlos

    2012-01-01

    The Macuira Gneiss is a Paleozoic metamorphic unit that outcrops in the Simarua, Jarara and Macuira ranges, Alta Guajira. It is composed by a lithologies metamorphosed under amphibolite facies P-T conditions and consist of amphibolitic and quartz feldspathic gneisses, amphibolites, schists, pegmatites, calc-silicated rocks and marbles, with migmatization evidences in gneisses and amphibolites. Five foliations (S1-5) and three folding events (F1-3) were identified and interpreted as product of two metamorphic events, developed in a progressive barrovian metamorphic gradient of intermediate pressure with intermediate P-T ratio, interpreted as product of continental collision tectonics. This unit is important in understanding of the tectonic evolution of the Alta Guajira and Caribbean because it records different deformational phases pre-, syn- and post-migmatitic, that could be related with different tectonic episodes: the first associated with the collision between Laurasia and Gondwana (Alleghanian Orogeny - Late Paleozoic), and the second related with the Caribbean Plate evolution (Andean Orogeny - Meso-Cenozoic).

  17. Presentation of new tectonic map (and accompanying sections) of Trinidad and Tobago

    Energy Technology Data Exchange (ETDEWEB)

    Persad, K.M.

    1984-04-01

    The Geologic Map of Trinidad, compiled by H.G. Kugler and published in 1961, is currently out of print. While it is the most widely available geologic map, it is confined to onshore Trinidad. This map remains an important reference source, but there have been significant increases in our knowledge of Trindad and Tobago geology since its publication. In particular, there has been: (1) considerable geophysical work, on land and offshore, including 20,000 km (12,400 mi) of seismic lines; (2) approximately 1000 exploration and development wells drilled, including wells in the previously unexplored north and east coast of Trinidad; and (3) significant advances in our understanding of the tectonic evolution of the area, which has resulted largely from the development of the plate tectonic theory. The following items, which take into account many of these new data and concepts, have been compiled. (1) A geologic tectonic map of the entire territory of Trinidad and Tobago, at a scale of 1:200,000. Apart from the surface geology of the land areas, this map shows the major faults and their displacements and locations, total depths and status of exploration wells, and the positions of major petroleum fields. (2) Five accompanying geologic sections at the same scale. (3) A new stratigraphic correlation chart. These new compilations attempt to fill the gap in the published literature on the petroleum geology of Trinidad and Tobago.

  18. Tectonic evolution of Lavinia Planitia, Venus

    Science.gov (United States)

    Squyres, Steven W.; Frank, Sharon L.; Mcgill, George E.; Solomon, Sean C.

    1991-01-01

    High resolution radar images from the Magellan spacecraft have revealed the first details of the morphology of the Lavinia Planitia region of Venus. Lavinia is a broad lowland over 2000 km across, centered at about 45 deg S latitude, 345 deg E longitude. Herein, the tectonic evolution of Lavinia is discussed, and its possible relationship to processes operating in the planet's interior. The discussion is restricted to the region from 37.3 to 52.6 deg S latitude and from about 340 to 0 deg E longitude. One of the most interesting characteristics of Lavinia is that the entire region possesses a regional tectonic framework of striking regularity. Lavinia is also transected by a complex pattern of belts of intense tectonic deformation known as ridge belts. Despite the gross topographic similarity of all of the ridge belts in Lavinia, they exhibit two rather distinct styles of near surface deformation. One is composed of sets of broad, arch-like ridges rising above the surrounding plains. In the other type, obvious fold-like ridges are rare to absent in the radar images. Both type show evidence for small amounts of shear distributed across the belts.

  19. Mimas: Tectonic structure and geologic history

    Science.gov (United States)

    Croft, Steven K.

    1991-01-01

    Mimas, the innermost of the major saturnian satellites, occupies an important place in comparative studies of icy satellites. It is the smallest icy satellite known to have a mostly spherical shape. Smaller icy objects like Hyperion and Puck are generally irregular in shape, while larger ones like Miranda and Enceladus are spherical. Thus Mimas is near the diameter where the combination of increasing surface gravity and internal heating begin to have a significant effect on global structure. The nature and extent of endogenic surface features provide important constraints on the interior structure and history of this transitional body. The major landforms on Mimas are impact craters. Mimas has one of the most heavily cratered surfaces in the solar system. The most prominent single feature on Mimas is Herschel, an unrelaxed complex crater 130 km in diameter. The only other recognized landforms on Mimas are tectonic grooves and lineaments. Groove locations were mapped by Schenk, but without analysis of groove structures or superposition relationships. Mimas' tectonic structures are remapped here in more detail than previously has been done, as part of a general study of tectonic features on icy satellites.

  20. Free vascularized flaps for reconstruction of the mandible: complications, success, and dental rehabilitation.

    Science.gov (United States)

    van Gemert, Johannes T M; van Es, Robert J J; Rosenberg, Antoine J W P; van der Bilt, Andries; Koole, Ron; Van Cann, Ellen M

    2012-07-01

    To evaluate complications and success of mandibular reconstruction with free fibula flaps, iliac crest flaps, and forearm flaps with reconstruction plates and to evaluate dental rehabilitation after these reconstructions. Eighty-three patients with segmental mandibular defects were included. Correlation analyses were used to determine the relationship between reconstruction type and clinical parameters with recipient-site complications and success. The dental rehabilitation was evaluated in successfully reconstructed survivors. Multivariate analyses showed significant correlations between flap type and success (P < .0001). Of the patients, 51 (61%) were alive 2 years after the reconstruction. Mandibular reconstruction with a free forearm flap and reconstruction plate was associated with higher complication rates at the recipient site and higher failure rates compared with reconstruction with free vascularized bone flaps. Of the 32 successfully reconstructed survivors, 14 (44%) had a complete dental rehabilitation, of which 10 had dental implants and 4 did not. Only 6 (29%) of the edentulous survivors ultimately had an implant-supported prosthesis. Reconstruction of the mandible with a free vascularized bone flap is superior to reconstruction with a free forearm flap with a reconstruction plate. Complete dental rehabilitation was reached in fewer than half of the surviving patients. Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  1. Simulation of the CMS Resistive Plate Chambers

    CERN Document Server

    Hadjiiska, R; Pavlov, B; Petkov, P; Dimitrov, A; Beernaert, K; Cimmino, A; Costantini, S; Garcia, G; Lellouch, J; Marinov, A; Ocampo, A; Strobbe, N; Thyssen, F; Tytgat, M; Verwilligen, P; Yazgan, E; Zaganidis, N; Aleksandrov, A; Genchev, V; Iaydjiev, P; Rodozov, M; Shopova, M; Sultanov, G; Ban, Y; Cai, J; Xue, Z; Ge, Y; Li, Q; Qian, S; Avila, C; Chaparro, L F; Gomez, J P; Moreno, B Gomez; Oliveros, A F Osorio; Sanabria, J C; Assran, Y; Sharma, A; Abbrescia, M; Colaleo, A; Pugliese, G; Loddo, F; Calabria, C; Maggi, M; Benussi, L; Bianco, S; Colafranceschi, S; Piccolo, D; Carrillo, C; Iorio, O; Buontempo, S; Paolucci, P; Vitulo, P; Berzano, U; Gabusi, M; Kang, M; Lee, K S; Park, S K; Shin, S; Kim, M S; Seo, H; Goh, J; Choi, Y; Shoaib, M

    2013-01-01

    The Resistive Plate Chamber (RPC) muon subsystem contributes significantly to the formation of the trigger decision and reconstruction of the muon trajectory parameters. Simulation of the RPC response is a crucial part of the entire CMS Monte Carlo software and directly influences the final physical results. An algorithm based on the parametrization of RPC efficiency, noise, cluster size and timing for every strip has been developed. Experimental data obtained from cosmic and proton-proton collisions at $\\sqrt{s}=7$ TeV have been used for determination of the parameters. A dedicated validation procedure has been developed. A good agreement between the simulated and experimental data has been achieved.

  2. El neopaleozoico de la Sierra de Castaño (Cordillera Frontal andina, San Juan, Argentina: Reconstrucción tectónica y paleoambiental The neopaleozoic of the Sierra de Castaño (Andean Cordillera Frontal, San Juan, Argentina: Tectonic and paleoenviromental reconstruction

    Directory of Open Access Journals (Sweden)

    Pedro Busquets

    2013-01-01

    demonstrates the existence of two mayor deformational events during the Carboniferous and Permian in the Andean region. The older one took place close to the Carboniferous-Permian boundary or during the earliest Permian. The second tectonic event, occurred at the end of the early Permian, correlates with the San Rafael Tectonic Phase that pointed out the onset of the large permotriassic volcanism (Choiyoi Group extensively developed along the Andean region.

  3. Tabletop Tectonics: Diverse Mountain Ranges Using Flour and Graphite

    Science.gov (United States)

    Davis, D. M.

    2006-12-01

    It has been recognized for some time that the frontal deformation zones where plates converge (foreland fold- and-thrust belts on continents and accretionary wedges at subduction zones) involve shortening over a decoupling layer, or decollement. A simple but successful way of explaining many aspects of their behavior is called the critical Coulomb wedge model, which regards these contractional wedges as analogous to the wedge-shaped mass of soil accreted in front of a bulldozer, or the wedge of snow that piles up in front of a snow plow. The shape and deformation history of the accreted wedge of soil or snow will depend upon the frictional strength of the material being plowed up and the surface over which it is being plowed. The same is true of `bulldozer' wedges consisting of many km thick piles of sediment at convergent plate margins. Using flour (or powdered milk), sandpaper, graphite, transparency sheets, and athletic field marker chalk, manipulated with sieves, brushes, pastry bags and blocks and sheets of wood, it is possible to demonstrate a wide variety of processes and tectonic styles observed at convergent plate boundaries. Model fold-and-thrust belts that behave like natural examples with a decollement that is strong (e.g., in rock without high pore fluid pressure) or weak (e.g., in a salt horizon or with elevated pore fluid pressure) can be generated simply by placing wither sandpaper or graphite beneath the flour that is pushed across the tabletop using a block of wood (the strong basement and hiterland rocks behind the fold-thrust belt). Depending upon the strength of the decollement, the cross-sectional taper of the deforming wedge will be thin or broad, the internal deformation mild or intense, and the structures either close to symmetric or strongly forward-vergent, just as at the analogous natural fold-thrust belts. Including a horizontal sheet of wood or Plexiglas in front of the pushing block allows generation of an accretionary wedge, outer

  4. Post-Neogene tectonism along the Aravalli Range, Rajasthan, India

    Science.gov (United States)

    Sen, Deepawati; Sen, Saurindranath

    1983-03-01

    The Aravalli Range runs southwest from Delhi for a distance of about 700 km. Its western margin is well defined, but the eastern margin is diffuse. Five geomorphic provinces are recognized in the study area: the western piedmont plains; the ridge and valley province which in the Central Aravallis occurs at two different heights separated by a fault scarp; the plateau province demarcated from the former by a fault scarp, confined to the Southern Aravallis, and occurring for a short stretch at two heights across another fault scarp; the BGC rolling plains east of the Range; and the BGC uplands south of the above. The scarps coincide with Precambrian faults. A series of rapids and water-falls, together with deeply entrenched river courses across the scarps and the youthful aspects of the escarpments with no projecting spurs, or straight river courses along their feet, all point unmistakably to a recent or post-Neogene vertical uplift along pre-existing faults. Presence of knickpoints at a constant distance from the Range in all west-flowing rivers, the ubiquitous terraces, and river courses entrenched within their own flood-plain deposits of thick gritty to conglomeratic sand, are indicative of a constant disturbance with a gradual rise of the Range east of the knickpoint, wherefrom the coarse materials were carried by the fast west-flowing streams. There is a differential uplift across the plateau scarp together with a right-lateral offset. This epeirogenic tectonism is ascribed to the collision of the Eurasian and the subducting Indian plates and to a locking of their continental crusts. By early Pleistocene, with the MBT gradually dying off, continued plate movement caused a flexural bending of the plate by a moment generated at the back, and a possible delinking of the continental crust along the zone of subduction. The felexural bending ripped open the Precambrian regional faults. The differential uplift and the difference in the distances of the nodes on two

  5. New tectonic data constrain the mechanisms of breakup along the Gulf of California

    Science.gov (United States)

    Bot, Anna; Geoffroy, Laurent; Authemayou, Christine; Graindorge, David

    2014-05-01

    The Gulf of California is resulting from an oblique-rift system due to the separation of the Pacific and the North American plates in the ~N110E to ~N125E trend. The age, nature and orientation of strain which ended with continental break-up and incipient oceanization at ~3.6 Ma, is largely misunderstood. It is generally proposed that early stages of extension began at around 12 Ma with strain partitioning into two components: a pure ENE directed extension in the Gulf Extensional Province (which includes Sonora and the eastern Baja California Peninsula in Mexico) and a dextral strike-slip displacement west of the Baja California Peninsula along the San Benito and Tosco-Abreojos faults. This evolution would have lasted ~5-6 Ma when a new transtensional strain regime took place. This regime, with extension trending ~N110E +/-10° , led to the final break-up and the subsequent individualization of a transform-fault system and subordoned short oceanic ridges. This two-steps interpretation has recently been challenged by authors suggesting a continuous transtensional extension from 12Ma in the trend of the PAC-NAM plates Kinematic. We question both of those models in term of timing and mode of accommodation basing ourselves on field investigations in Baja California Sur (Mexico). The volcano-sedimentary formations of the Comondù group dated 25 to 20 Ma exhibit clear examples of syn-sedimentary and syn-magmatic extensive deformations. This extension, oriented N65° E+/-15° , is proposed to initiate during the Magdalena Plate subduction. It would be related to the GOC initialization. In addition to this finding, we present tectonic and dating evidences of complex detachment-faulting tectonics varying in trend and kinematics with time and space for the development to the south of Baja California Sur. The extension associated with the early detachment-fault system trended ~N110E. From ~17 Ma to, probably, ~7-8 Ma, this extension controlled the early development of the San

  6. Mesozoic to Cenozoic tectonic transition process in Zhanhua Sag, Bohai Bay Basin, East China

    Science.gov (United States)

    Cheng, Yanjun; Wu, Zhiping; Lu, Shunan; Li, Xu; Lin, Chengyan; Huang, Zheng; Su, Wen; Jiang, Chao; Wang, Shouye

    2018-04-01

    The Zhanhua sag is part of the Bohai Bay intracontinental basin system that has developed since the Mesozoic in East China. The timing of this basin system coincides with the final assembly of East Asia and the development of Western Pacific-type plate margin. Here we use 3-D seismic and core log data to investigate the evolution of this basin and discuss its broad tectonic settings. Our new structural study of Zhanhua sag suggests that there are four major tectonic transitions occurred in the Bohai Bay Basin during Mesozoic and Cenozoic: (1) The first tectonic transition was from stable Craton to thrusting during the Triassic, mainly caused by the South China Block's subduction northward beneath the North China Block, which induced the formation of the NW-striking thrust faults. (2) The second tectonic transition was mainly characterized by a change from compression to extension, which can be further divided into two-stages. At the first stage, two episodes of NW-SE shortening occurred in East Asia during Early-Middle Jurassic and Late Jurassic-earliest Cretaceous, respectively. At the second stage, the extension and left-lateral shearing took place during Early Cretaceous while compression occurred during Late Cretaceous. The NW-striking thrust faults changed to normal faults and the NNE-striking left-lateral strike-slip faults started to influence the eastern part of the basin. (3) The third transition occurred when the NW-SE extension and NNE-striking right-lateral shearing started to form during Paleogene, and the peak deformation happen around 40 Ma due to the change of the subduction direction of Pacific Plate relative to Eurasia Plate. The NE-striking normal faults are the main structure, and the pre-existing NNE-striking strike-slip faults changed from left-lateral to right-lateral. (4) The fourth transition saw the regional subsidence during Neogene, which was probably caused by the India-Asia "Hard collision" between 25 and 20 Ma.

  7. Crustal-scale alpine tectonic evolution of the western Pyrenees - eastern Cantabrian Mountains (N Spain) from integration of structural data, low-T thermochronology and seismic constraint

    Science.gov (United States)

    DeFelipe, I.; Pedreira, D.; Pulgar, J. A.; Van der Beek, P.; Bernet, M.; Pik, R.

    2017-12-01

    The Pyrenean-Cantabrian Mountain belt extends in an E-W direction along the northern border of Spain and resulted from the convergence between the Iberian and European plates from the Late Cretaceous to the Miocene, in the context of the Alpine orogeny. The main aim of this work is to characterize the tectonic evolution at a crustal-scale of the transition zone from the Pyrenees to the Cantabrian Mountains, in the eastern Basque-Cantabrian Basin (BCB). We integrate structural work, thermochronology (apatite fission track and zircon (U-Th)/He) and geophysical information (shallow seismic reflection profiles, deep seismic refraction/wide-angle reflection profiles and seismicity distribution) to propose an evolutionary model since the Jurassic to the present. During the Albian, hyperextension related to the opening of the Bay of Biscay yielded to mantle unroofing to the base of the BCB. This process was favored by a detachment fault that connected the mantle in its footwall with the base of a deep basin in its hanging wall. During this process, the basin experienced HT metamorphism and fluid circulation caused the serpentinization of the upper part of the mantle. There is no evidence of seafloor mantle exhumation before the onset of the Alpine orogeny. The thermochronological study points to a N-vergent phase of contractional deformation in the late Eocene represented by the thin-skinned Leiza fault system followed in the early Oligocene by the S-vergent, thick-skinned, Ollín thrust. Exhumation rates for the late Eocene-early Oligocene are of 0.2-0.7 km/Myr. After that period, deformation continues southwards until the Miocene. The crustal-scale structure resultant of the Alpine orogeny consists of an Iberian plate that subducts below the European plate. The crust is segmented into four blocks separated by three S-vergent crustal faults inherited from the Cretaceous extensional period. The P-wave velocities in this transect show anomalous values (7.4 km/s) in the

  8. Editorial: Introduction to the Special Issue ;Slope Tectonics: Inherited Structures, Morphology of Deformation and Catastrophic Failure;

    Science.gov (United States)

    Hermanns, R. L.; Oppikofer, T.; Jaboyedoff, M.; Clague, J. J.; Scarascia-Mugnozza, G.

    2017-07-01

    The "Conference on Slope Tectonics" has become an international scientific meeting point to present and discuss a variety of topics related to slope deformation and the deposits of related failures. The first conference took place on February 15-16, 2008 at University of Lausanne (Switzerland). It was followed by a second conference on September 6-10, 2011, in Austria (organized by the Geological Survey of Austria) and a third on September 8-12, 2014, in Norway (organized by the Geological Survey of Norway). The two later events included field trips. It has become a tradition that selected papers from these conference are published - papers from the first conference were published by the Geological Society as Special Publication 351 (Jaboyedoff, 2011), and those from the second conference were published in a special issue of Tectonophysics (Baron and Jaboyedoff, 2013). This special issue of Geomorphology is a collection of papers presented at the Norwegian Conference on Slope Tectonics. This collection of papers focuses on the role of tectonics in gravitationally induced rock-slope instabilities. The slopes either deform over long periods as deep-seated gravitational slope deformation (DSGSD) or more rapidly as rockslides or rock avalanches. The reconstruction of slope deformation is an integral part of the studies captured in this special issue.

  9. Remote sensing revealed drainage anomalies and related tectonics of South India

    Science.gov (United States)

    Ramasamy, SM.; Kumanan, C. J.; Selvakumar, R.; Saravanavel, J.

    2011-03-01

    Drainages have characteristic pattern and life histories with youthful stage in hilly areas, mature stage in plains and old stage in the coastal zones. The deviations from their normal life histories, especially aberrations in their flow pattern in the form of various drainage anomalies have been inferred to be the indications of dominantly the Eustatic and Isostatic changes. This, especially after the advent of Earth Observing Satellites, has attracted the geoscientists from all over the world, for studying such drainage anomalies. In this connection, a study has been undertaken in parts of South India falling south of 14° south latitude to comprehensively map some drainage anomalies like deflected drainages, eyed drainages and compressed meanders and to evolve the tectonic scenario therefrom. The mapping of such mega drainage anomalies and the related lineaments/faults from the satellite digital data and the integration of such lineaments/faults with the overall lineament map of South India showed that the study area is marked by active N-S block faults and NE-SW sinistral and NW-SE dextral strike slip faults. Such an architecture of active tectonic grains indicates that the northerly directed compressive force which has originally drifted the Indian plate towards northerly is still active and deforming the Indian plate.

  10. Breast Reconstruction After Mastectomy

    Science.gov (United States)

    ... Cancer Prevention Genetics of Breast & Gynecologic Cancers Breast Cancer Screening Research Breast Reconstruction After Mastectomy On This Page What is breast reconstruction? How do surgeons use implants to reconstruct a woman’s breast? How do surgeons ...

  11. Breast reconstruction - implants

    Science.gov (United States)

    Breast implants surgery; Mastectomy - breast reconstruction with implants; Breast cancer - breast reconstruction with implants ... harder to find a tumor if your breast cancer comes back. Getting breast implants does not take as long as breast reconstruction ...

  12. Surveys on environmental tectonics. Special volume.

    NARCIS (Netherlands)

    Cloetingh, S.A.P.L.; Cornu, T.

    2005-01-01

    Until now, research on neotectonics and related seismicity has mostly focused on active plate boundaries characterized by generally high earthquake activity. Current seismic hazard estimates for intraplate areas are commonly based on probabilistic analyses of historical and instrumental earthquake

  13. Cadmium plating replacements

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, M.J.; Groshart, E.C.

    1995-03-01

    The Boeing Company has been searching for replacements to cadmium plate. Two alloy plating systems seem close to meeting the needs of a cadmium replacement. The two alloys, zinc-nickel and tin-zinc are from alloy plating baths; both baths are neutral pH. The alloys meet the requirements for salt fog corrosion resistance, and both alloys excel as a paint base. Currently, tests are being performed on standard fasteners to compare zinc-nickel and tin-zinc on threaded hardware where cadmium is heavily used. The Hydrogen embrittlement propensity of the zinc-nickel bath has been tested, and just beginning for the tin-zinc bath. Another area of interest is the electrical properties on aluminum for tin-zinc and will be discussed. The zinc-nickel alloy plating bath is in production in Boeing Commercial Airplane Group for non-critical low strength steels. The outlook is pr