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Sample records for alpine tectonic evolution

  1. Interactions between tectonics, erosion, and sedimentation during the recent evolution of the alpine orogen: analogue modeling insights

    OpenAIRE

    Bonnet, Cécile; Malavieille, Jacques; Mosar, Jon

    2008-01-01

    On the basis of a section across the northwestern Alpine wedge and foreland basin, analogue modeling is used to investigate the impact of surface processes on the orogenic evolution. The basis model takes into account both structural and lithological heritages of the wedge. During shortening, erosion and sedimentation are performed to maintain a critical wedge. Frontal accretion leads to the development of a foreland thrust belt; underplating leads to the formation of an antiformal nappe stac...

  2. Complex tectonic and tectonostratigraphic evolution of an Alpine foreland basin: The western Duero Basin and the related Tertiary depressions of the NW Iberian Peninsula

    Science.gov (United States)

    Martín-González, F.; Heredia, N.

    2011-04-01

    The tectonic and tectonostratigaphic evolution of foreland basins and related Tertiary depressions are the key to investigate deformation history and the uplifting of the continental lithosphere of the Alpine-Pyrenean Orogeny. The northern part of the Duero basin is the foreland basin of the Cantabrian Mountains, which are, in turn, the western part of the Pyrenean Orogen. We have studied the western sharp end of the Duero foreland basin, and its relation to the Tertiary deposits of the NW Iberian Peninsula and the topography evolution. In order to propose a coherent tectonic and tectonosedimentary model that could explain all Tertiary deposits, we have analysed the depositional environment, stratigraphic sequences, paleocurrents and established a correlation of the main outcrops. Besides, a detailed structural mapping of the Alpine structures that limit and affect the main Tertiary outcrops has been carried out. The Tertiary deposits of the NW Iberian Peninsula depressions are affected and fragmented by Alpine structures that limit their extensions and locations. The stratigraphic succession is similar in the NW Tertiary outcrops; they are mainly terrigenous and carbonated continental deposits formed by assemblage of alluvial fans developed at the mountains front, in arid or semiarid conditions. Three formations can be identified in the main depressions: Toral Fm, Santalla Fm and Médulas Fm. The NW Tertiary outcrops were the western deposits of the Duero foreland basin that surrounded the lateral termination of the Pyrenean Orogen. These deposits were fragmented and eroded by the subsequent uplift of the Galaico-Leoneses Mountains and the NE-SW strike-slip faults activity (broken foreland basin). Only the latest stages of some of these outcrops can be considered as intramontane basins as traditionally have been interpreted. The sedimentation started in the northeast (Oviedo-Infiesto) during the Eocene and migrated to the west (As Pontes) during the Late Oligocene

  3. Magnetic fabric study of rock deformation during alpine tectonic evolution on a cross section through the Eastern Alps (Austria)

    Science.gov (United States)

    Gruber, K.; Scholger, R.; Pueyo, E. L.

    2010-05-01

    Measurements of anisotropy of magnetic susceptibility (AMS) were carried out on samples from more than seventy sites collected in the Eastern Alps. The sites were taken alongside a North-South transect (about 15°30` East Longitude) from Scheibbs in the North to Kapfenberg in the South, comprising most of the Northern Calcareous Alps (NCA) nappes, Helvetic and Penninic Flysh units as well as the greywacke zone. Samples were taken in detail mostly in Mesozoic rocks of the NCA, from North to South: Bajuvaric (Frankenfels, Lunz, Sulzbach and Reisalpen nappes), Tirolic (Ötscher, Göller, Rotwald-Gindelstein nappes) and Juvavic (Mürzalpen nappe) system. Two to six sites per thrust sheet or nappe were analysed for a structural investigation of the relationship between magnetic fabric and tectonic strain. Standard paleomagnetic drill cores were taken. All measurements were performed in the Petrophysics and Paleomagnetic laboratories of the University of Leoben using AGICO MFK1-Kappabridge susceptibility system and a 2-G cryogenic magnetometer. Statistical evaluation of the AMS data was perfomed using the software package AGICO ANISOFT 4.2. (Chadima et al., 2009). Throughout the Eastern Alps transect distinct changes of the magnetic fabric are observed. Primary sedimentary fabrics and very low susceptibility values are dominant in most cases in the northernmost and southernmost part of the transect. Some inverse fabrics were found in few sites of the nappes and the percentage increases towards the south which might be related to tectonic events. Contrastingly, isotropic fabrics dominate in the middle part. The Helvetic and Penninic Flysh units yield in general weak oblate fabrics. A few sites show a tendency to inverse fabrics which indicate the presence of a certain amount of strain within this unit. The oblate fabrics of the Helvetic and Flysh units show either shallow NE dipping or slightly steeper SW dipping k1-axis orientation. Within the inverse fabrics, even

  4. Subsidence, stress regime and rotation(s) of a tectonically active sedimentary basin within the western Alpine Orogen: the Tertiary Piedmont Basin (Alpine domain, NW Italy)

    NARCIS (Netherlands)

    Carrapa, B.; Bertotti, G.; Krijgsman, W.

    2003-01-01

    The Oligocene to Miocene Tertiary Piedmont Basin (TPB) is located in the NW part of Italy at the junction between the Apennine and the Alpine thrust belts. The position of the TPB on top of the Alpine/Apennine Orogen poses fundamental questions as to the tectonics of the basin subsidence. Having und

  5. Plio-Pleistocene evolution of the north Alpine drainage system: new constraints from detrital thermochronology of foreland deposits

    Science.gov (United States)

    Reiter, Wolfgang; Elfert, Simon; Glotzbach, Christoph; Spiegel, Cornelia

    2015-04-01

    The evolution of drainage systems in and around active orogens may be strongly affected by climatic or tectonic processes. Information on the drainage evolution is stored in the sediments of the foreland depocentres. We investigated the provenance of two key deposits adjacent to the Central Alps, the Pliocene Sundgau gravels and the Pleistocene Höhere Deckenschotter by applying detrital thermochronology. Combined with provenance information from Rhine Graben deposits, we propose a reconstruction of the north Alpine drainage system since the middle Pliocene and discuss potential controlling mechanisms. Our data show that the Rhine Graben received detritus from the Alpine realm already during the Pliocene, indicating two different river systems—the proto-Rhine and the Aare-Doubs—draining the Alpine realm toward the North Sea and Mediterranean Sea. The investigated sediments contain detritus from two central Alpine sources, one showing a regional exhumational equilibrium and the other characterized by increasing exhumation rates. Discharge of the latter source ceased after ~2 Ma, reflecting a northward shift of the main Alpine drainage divide. Between ~2.0 and 1.2 Ma, the drainage system was affected by a major change, which we explain as resulting from a change in the Alpine stress field leading to tectonic exhumation and topography reduction in the area of the southern Aar massif. Generally, it seems that between ~4 and 1.2 Ma, the drainage system was mainly controlled by tectonic processes, despite first glaciations that already affected the north-Alpine foreland by ~2 Ma. The drainage system only seems to have reacted to the late Cenozoic climate changes after ~1.2 Ma, i.e., at the time of the most intense Alpine glaciation. At that time, the course of the Rhine River shifted toward the area of the Hegau volcanics, and the size of the Rhine River catchment became strongly reduced.

  6. Subsidence, stress regime and rotation(s) of a tectonically active sedimentary basin within the western Alpine Orogen: the Tertiary Piedmont Basin (Alpine domain, NW Italy)

    OpenAIRE

    Carrapa, B.; Bertotti, G.; Krijgsman, W.

    2003-01-01

    The Oligocene to Miocene Tertiary Piedmont Basin (TPB) is located in the NW part of Italy at the junction between the Apennine and the Alpine thrust belts. The position of the TPB on top of the Alpine/Apennine Orogen poses fundamental questions as to the tectonics of the basin subsidence. Having undergone little deformation, the TPB sediments provide an insight into the stress regime and rotations in the kinematically very complex area surrounding the basin itself. In this study we integrate ...

  7. Tectonic evolution of mercury; comparison with the moon

    International Nuclear Information System (INIS)

    With regard to the Earth or to Mars, the Moon and Mercury look like tectonicless planetary bodies, and the prominent morphologies of these two planets are due to impact and volcanic processes. Despite these morphologies, several types of tectonic activities may be shown. Statistical studies of lineaments direction indicate that Mercury, as well as the Moon, have a planet wide lineament pattern, known as a ''grid''. Statistical studies of Mercury scarps and the Moon grabens indicate an interaction between planetary lithospheric evolution and large impact basins. Detailed studies of the largest basins indicate specific tectonic motions directly or indirectly related to impacts. These three tectonic types have been compared on each planet. The first tectonic type seems to be identical for Mercury and the Moon. But the two other types seem to be different, and are consistent with the planets' thermal evolution

  8. Rapid biological speciation driven by tectonic evolution in New Zealand

    Science.gov (United States)

    Craw, Dave; Upton, Phaedra; Burridge, Christopher P.; Wallis, Graham P.; Waters, Jonathan M.

    2016-02-01

    Collisions between tectonic plates lead to the rise of new mountain ranges that can separate biological populations and ultimately result in new species. However, the identification of links between tectonic mountain-building and biological speciation is confounded by environmental and ecological factors. Thus, there are surprisingly few well-documented examples of direct tectonic controls on terrestrial biological speciation. Here we present examples from New Zealand, where the rapid evolution of 18 species of freshwater fishes has resulted from parallel tectonic landscape evolution. We use numerical models to reconstruct changes in the deep crustal structure and surface drainage catchments of the southern island of New Zealand over the past 25 million years. We show that the island and mountain topography evolved in six principal tectonic zones, which have distinct drainage catchments that separated fish populations. We use new and existing phylogenetic analyses of freshwater fish populations, based on over 1,000 specimens from more than 400 localities, to show that fish genomes can retain evidence of this tectonic landscape development, with a clear correlation between geologic age and extent of DNA sequence divergence. We conclude that landscape evolution has controlled on-going biological diversification over the past 25 million years.

  9. Multiagent simulation of evolutive plate tectonics applied to the thermal evolution of the Earth

    OpenAIRE

    Combes, M. (M.); Grigné, C.; HUSSON, Laurent; Conrad, C. P.; Le Yaouanq, Sébastien; Parenthoën, M.; Tisseau, C.; Tisseau, Jacques

    2012-01-01

    International audience [1] The feedback between plate tectonics and mantle convection controls the Earth's thermal evolution via the seafloor age distribution. We therefore designed the MACMA model to simulate time-dependent plate tectonics in a 2D cylindrical geometry with evolutive plate boundaries, based on multiagent systems that express thermal and mechanical interactions. We compute plate velocities using a local force balance and use explicit parameterizations to treat tectonic proc...

  10. A window for plate tectonics in terrestrial planet evolution?

    Science.gov (United States)

    O'Neill, Craig; Lenardic, Adrian; Weller, Matthew; Moresi, Louis; Quenette, Steve; Zhang, Siqi

    2016-06-01

    The tectonic regime of a planet depends critically on the contributions of basal and internal heating to the planetary mantle, and how these evolve through time. We use viscoplastic mantle convection simulations, with evolving core-mantle boundary temperatures, and radiogenic heat decay, to explore how these factors affect tectonic regime over the lifetime of a planet. The simulations demonstrate (i) hot, mantle conditions, coming out of a magma ocean phase of evolution, can produce a "hot" stagnant-lid regime, whilst a cooler post magma ocean mantle may begin in a plate tectonic regime; (ii) planets may evolve from an initial hot stagnant-lid condition, through an episodic regime lasting 1-3 Gyr, into a plate-tectonic regime, and finally into a cold, senescent stagnant lid regime after ∼10 Gyr of evolution, as heat production and basal temperatures wane; and (iii) the thermal state of the post magma ocean mantle, which effectively sets the initial conditions for the sub-solidus mantle convection phase of planetary evolution, is one of the most sensitive parameters affecting planetary evolution - systems with exactly the same physical parameters may exhibit completely different tectonics depending on the initial state employed. Estimates of the early Earth's temperatures suggest Earth may have begun in a hot stagnant lid mode, evolving into an episodic regime throughout most of the Archaean, before finally passing into a plate tectonic regime. The implication of these results is that, for many cases, plate tectonics may be a phase in planetary evolution between hot and cold stagnant states, rather than an end-member.

  11. Variscan tectonics in the Holy Cross Mountains (Poland) and the role of structural inheritance during Alpine tectonics

    Science.gov (United States)

    Lamarche, J.; Mansy, J. L.; Bergerat, F.; Averbuch, O.; Hakenberg, M.; Lewandowski, M.; Stupnicka, E.; Swidrowska, J.; Wajsprych, B.; Wieczorek, J.

    1999-11-01

    The present study was carried out in the Holy Cross Mountains (HCM) of south-central Poland and includes computation of palaeostresses following Angelier's method and field structural analysis. The Palaeozoic basement of the HCM comprises two tectonic units separated by the major WNW-ESE-striking Holy Cross Fault (HCF). Fold analysis indicates a N-S to NNE-SSW direction of Variscan shortening. Micro-structures and fold analysis from Upper Devonian rocks further reveal: (1) a brittle tectonic event due to a NW-SE compression preceding folding that could be related to pre-Late Carboniferous tectonics, due to block transport within the Tornquist-Teisseyre Zone (TTZ), and (2) polyphase Variscan folding comprising (a) an early stage of N-S shortening marked by north-verging ramps, (b) a main folding event and axial cleavage formation involving N-S to NNE-SSW shortening, and (c) a late stage of shortening deforming older folds and cleavage. A mainly extensional tectonic regime dominated from the Permian until the Cretaceous, during which time the HCF was reactivated as a normal fault. Large NW-SE faults bordering the Mid-Polish Trough (MPT) developed. Subsequent tectonic inversion of the MPT resulted in basin uplift (`Mid-Polish Swell', MPS). Palaeostress computations from Mesozoic strata suggest a NE-SW direction for the main Maastrichtian-Paleocene shortening phase, in addition to two minor brittle events resulting from N-S and E-W compression. Analysis of local folds in the Mesozoic cover indicates a causal relationship with the Maastrichtian-Paleocene reactivation of older faults. In particular, en-échelon folds in the Radomsko Elevation suggest a sinistral reactivation of the Palaeozoic HCF. Folds in the southwestern part of the HCM argue for reactivation in the reverse mode of a NW-SE-trending fault bordering the MPS that originated in the Mesozoic. In Palaeozoic strata, post-Variscan brittle deformation and micro-fault reactivation are attributed to the tectonic

  12. Geochronological evidence for the Alpine tectono-thermal evolution of the Veporic Unit (Western Carpathians, Slovakia)

    Science.gov (United States)

    Vojtko, Rastislav; Králiková, Silvia; Jeřábek, Petr; Schuster, Ralf; Danišík, Martin; Fügenschuh, Bernhard; Minár, Jozef; Madarás, Ján

    2016-01-01

    Tectono-thermal evolution of the Veporic Unit was revealed by multiple geochronological methods, including 87Rb/86Sr on muscovite and biotite, zircon and apatite fission-track, and apatite (U-Th)/He analysis. Based on the new data, the following Alpine tectono-thermal stages can be distinguished: The Eo-Alpine Cretaceous nappe stacking (~ 135-95 Ma) resulted in burial of the Veporic Unit beneath the northward overthrusting Gemeric Unit and overlying Jurassic Meliata accretionary wedge. During this process the Veporic Unit reached metamorphic peak of greenschist- to amphibolite facies accompanied by orogen-parallel flow in its lower and middle crust. The subsequent evolution of this crust is associated with two distinct exhumation mechanisms related to collision with the northerly Tatric-Fatric basement. The first mechanism (~ 90-80 Ma) is associated with internal subhorizontal shortening of the Veporic Unit reflected by large-scale upright folding and heterogeneous exhumation of the Veporic lower crust in the cores of crustal-scale antiforms. This led to juxtaposition of the higher and lower grade parts of basement, all cooled down to ~ 350 °C by ~ 80 Ma. The second mechanism is associated with the overthrusting of the Veporic Unit over the attenuated Fatric crust. This led to a passive en-block exhumation of the Veporic crust from ~ 350 °C to 60 °C between ~ 80 and 55 Ma followed by erosion (~ 55-35 Ma). The erosion processes resulted in formation of planation surface before the Late Eocene transgression. After erosion and planation, a new sedimentary cycle of the Central Carpathian Palaeogene Basin was deposited with the sedimentary strata thickness of ~ 1.5-2.0 km (~ 21-17 Ma). The early to middle Miocene is characterised by destruction tectonic disintegration and erosion of this basin (~ 20-13 Ma) and formation of the Neogene Vepor Stratovolcano (~ 13 Ma). The final shaping of the area has been linked to erosional processes of the volcanic structure since

  13. Role of fluids in the tectonic evolution of Titan

    Science.gov (United States)

    Liu, Zac Yung-Chun; Radebaugh, Jani; Harris, Ron A.; Christiansen, Eric H.; Rupper, Summer

    2016-05-01

    Detailed analyses of slopes and arcuate planform morphologies of Titan's equatorial mountain ridge belts are consistent with formation by contractional tectonism. However, contractional structures in ice require large stresses (4-10 MPa), the sources of which are not likely to exist on Titan. Cassini spacecraft imagery reveals a methane-based hydrological cycle on Titan that likely includes movement of fluids through the subsurface. These crustal liquids may enable contractional tectonic features to form as groundwater has for thrust belts on Earth. In this study, we show that liquid hydrocarbons in Titan's near subsurface can lead to fluid overpressures that facilitate contractional deformation at smaller stresses (reducing the shear strength of materials. Titan's crustal conditions with enhanced pore fluid pressures favor the formation of thrust faults and related folds in a contractional stress field. Thus, surface and near-surface hydrocarbon fluids made stable by a thick atmosphere may play a key role in the tectonic evolution of Titan.

  14. Polyphase tectonic subsidence evolution of the Vienna Basin inferred from quantitative subsidence analysis of the northern and central parts

    Science.gov (United States)

    Lee, Eun Young; Wagreich, Michael

    2016-04-01

    The Vienna Basin is a tectonically complex Neogene basin situated at the Alpine-Carpathian transition. This study analyzes a detailed quantification of subsidence in the northern and central parts of the Vienna Basin to understand its tectonic subsidence evolution. About 200 wells were used to arrange stratigraphic setting, and wells reaching the pre-Neogene basement were analyzed for subsidence. To enhance the understanding of the regional subsidences, the wells were sorted into ten groups based on their position on major fault blocks. In the Early Miocene, subsidence was slow and along E-W to NE-SW trending axis, indicating the development of thrust-controlled piggyback basins. During the late Early Miocene data show abruptly increasing subsidence, making the initiation of the Vienna pull-apart basin system. From the Middle Miocene, the tectonic subsidence curves show regionally different patterns. The tectonic subsidence during the Middle Miocene varies laterally across the Vienna Basin, and the differential subsidence can be related to the changing tensional regime of weakening transtension and strengthening extension toward the late Middle Miocene. From the late Middle Miocene to the Late Miocene, the tectonic subsidence occurred dominantly along the regional active faults, and corresponds to the axis of E-W trending extension of the western parts of the Pannonian Basin system. In the Quaternary the Vienna Basin has been reactivated, and resulted in subsidence along the NE-SW trending Vienna Basin transfer fault system.

  15. Tectonic evolution of the Tombel graben basement, southwestern Cameroon

    Institute of Scientific and Technical Information of China (English)

    M.S.Njome; C.E.Suh

    2005-01-01

    Planar structures (foliations and fractures) around the Tombel graben (southwestern end of the Central African Shear zone system) have been investigated and analyzed with the aim of unraveling the tectonic evolution of the basement. The foliations show two major trends, an older N-S-trending gneissose layering of uncertain agereworked by a later Pan-African (600 + 50 Ma) NE-SW ductile trend that is contemporaneous with sinistral shearing and mylonitization. The brittle phase characterized by NW-SE-trending open and partially filled fractures is younger than the mylonitization event and although it has not been dated, it is suggested that the origin of these fractures is linked to the onset of volcanism along the Cameroon volcanic line-31 m.y. ago.The mylonitic foliation is recognized for the first time and supports a tectonic evolution model for the Tombel graben in which ductile non-coaxial deformation was succeeded by brittle failure.

  16. Tectonic Evolution of China and Its Control over Oil Basins

    Institute of Scientific and Technical Information of China (English)

    Wang Hongzhen; Li Sitian

    2004-01-01

    This paper is a brief review of the tectonic frame and crustal evolution of China and their control over the oil basins. China is subdivided into three regions by the Hercynian Ertix-Almantai (EACZ) and Hegenshan (HGCZ) convergent zones in the north, and the Indosinian Muztagh-Maqen (MMCZ) and the Fengxiang-Shucheng (FSCZ) convergent zones in the south. The northern region represents the southern marginal tract of the Siberian platform. The middle region comprises the Sino-Korea (SKP), Tarim (TAP) platforms and surrounding Paleozoic orogenic belts. The southern region includes the Yangtze platform (YZP), the Cathaysia (CTA) paleocontinent and the Caledonides between them in the eastern part, and the Qinghai-Tibet plateau composed of the Gondwana-affiliated massifs and Meso- and Cenozoic orogenic belts in the western part. The tectonic evolutions of China are described in three stages: Jinningian and pre-Jinningian, Caledonian to Indosinian, and post-Indosinian. Profound changes occurred at the end of Jinningian (ca. 830 Ma) and the Indosinian (ca. 210 Ma) tectonic epochs, which had exerted important influence on the formation of different types of basins. The oil basins distribute in four belts in China, the large superimposed basins ranging from Paleozoic to Cenozoic (Tarim and Junggar) in the western belt, the large superimposed basins ranging from Paleozoic to Mesozoic (Ordos and Sichuan) in the central belt, the extensional rift basins including the Cretaceous rift basins (Songliao) and the Cenozoic basin (Bohaiwan) in the eastern belt, and the Cenozoic marginal basins in the easternmost belt in offshore region. The tectonic control over the oil basins consists mainly in three aspects: the nature of the basin basement, the coupling processes of basin and orogen due to the plates interaction, and the mantle dynamics, notably the mantle upwelling resulting in crustal and lithospheric thinning beneath the oil basins.

  17. Cretaceous—Quaternary tectonic evolution of the Tatra Mts (Western Carpathians: constraints from structural, sedimentary, geomorphological, and fission track data

    Directory of Open Access Journals (Sweden)

    Králiková Silvia

    2014-08-01

    Full Text Available The Tatra Mts area, located in the northernmost part of Central Western Carpathians on the border between Slovakia and Poland, underwent a complex Alpine tectonic evolution. This study integrates structural, sedimentary, and geomorphological data combined with fission track data from the Variscan granite rocks to discuss the Cretaceous to Quaternary tectonic and landscape evolution of the Tatra Mts. The presented data can be correlated with five principal tectonic stages (TS, including neotectonics. TS-1 (~95-80 Ma is related to mid-Cretaceous nappe stacking when the Tatric Unit was overlain by Mesozoic sequences of the Fatric and Hronic Nappes. After nappe stacking the Tatric crystalline basement was exhumed (and cooled in response to the Late Cretaceous/Paleogene orogenic collapse followed by orogen-parallel extension. This is supported by 70 to 60 Ma old zircon fission track ages. Extensional tectonics were replaced by transpression to transtension during the Late Paleocene to Eocene (TS-2; ~80-45 Ma. TS-3 (~45-20 Ma is documented by thick Oligocene-lowermost Miocene sediments of the Central Carpathian Paleogene Basin which kept the underlying Tatric crystalline basement at elevated temperatures (ca. > 120 °C and < 200 °C. The TS-4 (~20-7 Ma is linked to slow Miocene exhumation rate of the Tatric crystalline basement, as it is indicated by apatite fission track data of 9-12 Ma. The final shaping of the Tatra Mts has been linked to accelerated tectonic activity since the Pliocene (TS-5; ~7-0 Ma.

  18. Tectonic evolution of the Brooks Range ophiolite, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Harris, R.A. (West Virginia Univ., Morgantown, WV (United States). Dept. of Geology)

    1993-04-01

    Detailed studies of the composition, internal structure, and age of the Brooks Range ophiolite (BRO) and its metamorphic sole reveal new constraints for its tectonic evolution. The BRO consists of six separate thrust masses of consanguineous composition, internal organization, structure and age. Subophiolite metamorphic rocks are locally preserved along its structural base, which is well exposed in several places. The metamorphic sole is locally transitional with mafic volcanic sequences, chert, tuffs, and minor clastic sedimentary material of the Copter Peak Complex, which is correlative with the Angayucham terrane. This terrane is much older than, and chemically distinct from the BRO. The internal structure of the BRO is characterized by NE-SW trending igneous layers that expose the transition zone from crust to mantle. Residual mantle material consists of tectonized peridotite in abrupt contact with dunite pods up to 4 km thick. Ductile and brittle structures of the BRO preserve various phases of its dynamic evolution from a magma body to a fragmented thrust sheet. The earliest deformational effects are recorded by ductile lattice and shape fabrics in dunites and the layered series of the BRO. Magmatic flow planes generally parallel the petrologic moho, and dip 40[degree]--70[degree] to the NW and SE. Flow lineations consistently plunge ESE-ENE from 39[degree]--54[degree]. Igneous laminations and compositional layers represent patterns of magmatic flow in, and plastic deformation of, a cumulate sequence -- not the deposition pattern of cumulate layers. In the upper layered series, amphiboles with a shape-preferred orientation yield Ar/Ar plateau ages of 163--169 Ma. These ages overlap with plateau ages of the same kind from amphibolite of the metamorphic sole. This concordance in age indicates that cooling of the BRO coincided with its tectonic emplacement.

  19. Tectonic subsidence history and thermal evolution of the Orange Basin

    Science.gov (United States)

    Hirsch, K. K.; Scheck-Wenderoth, M.; van Wees, J.; Paton, D. A.; Kuhlmann, G.

    2008-12-01

    The Orange Basin offshore southwest Africa appears to represent a classical example of continental rifting and break up associated with large-scale, transient volcanism. The presence of lower crustal bodies of high seismic velocities indicates that large volumes of igneous crust formed as a consequence of lithospheric extension. We present results of a combined approach using subsidence analysis and basin history inversion models. Our results show that a classical uniform stretching model does not account for the observed tectonic subsidence. Moreover we find that that the thermal and subsidence implications of underplating need to be considered. Another departure from the uniform stretching model is re-newed sub-crustal stretching and linked to that uplift in the Cenozoic which is necessary to reproduce the observed phases of erosion and the present day depth of the basin. The dimension of these events has been examined and quantified in terms of tectonic uplift and sub-crustal stretching. Based on these forward models we predict the heat flow evolution not only for the available real wells but also for virtual wells over the entire study area. Finally the hydrocarbon potential and the temperature evolution is presented and shown in combination with inferred maturation of the sediments for depth intervals which comprise potential source rocks.

  20. Contribution of the fission-track method to the study of the Alpine chains: relationship between tectonics and metamorphism

    International Nuclear Information System (INIS)

    The fission-track method allows geologists to date rocks and to get information on the thermal history of rocks. Fission tracks in minerals are essentially due to the spontaneous fission of uranium 238. The knowledge of the density of tracks and the concentration of uranium 238 lead to the determination of the age of the rock. The irradiation in a neutron flux of a sample of the rock allows the determination of the concentration of uranium. The age obtained is in fact an apparent age that does not take into account possible geological annealing process that may erase fission tracks, some corrections are then necessary. The first part of this work details the fission-track method, its scope and limitations. It is shown that fission-track method on apatites can reveal the thermal evolution of the rock and that the same method used on zircons can give information of the setting of volcanic rocks. The second part is dedicated to the contribution of the fission-track method to a both dating and thermal evolution study of a french-italian part of the Alpine chain

  1. Tectonic evolution of Kashmir basin in northwest Himalayas

    Science.gov (United States)

    Alam, Akhtar; Ahmad, Shabir; Bhat, M. Sultan; Ahmad, Bashir

    2015-06-01

    Geomorphology has long been recognised as a key to evaluate the interplay between tectonics and landscape geometry in the regions of active deformation. We use geomorphic signatures at varied spatial scales interpreted from SRTM-DEM/Landsat-ETM data, supplemented with field observations to review the tectonic evolution of Kashmir basin in northwest Himalayas. Geomorphic evidence is persuasive of a credible NNW-SSE trending dextral strike-slip structure (central Kashmir Fault - CKF), with the strike length of ~ 165 km, stretched centrally over the NNW-SSE length of the Kashmir basin. As a result of the strike-slip motion and subsequent erosion, significant deformation has taken place along the CKF. In addition, broad geomorphic architecture of the basin reveals typical pull-apart characteristics. Hence, we deduce that the Kashmir basin has evolved as a pull-apart Quaternary sediment depression owing to the deformation along the central Kashmir Fault. The spatial distribution pattern of seismic events (NEIC-catalogue, 1973-2013) and GPS measurements (published), collectively substantiate our geomorphic interpretations.

  2. Tectonic geomorphological characteristics for evolution of the Manas Lake

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Owing to global climatic changes and human activities,the lakes have changed dramatically in the Junggar Basin of Xinjiang in recent 50 years. Based on the remote sensing images from Beijing Satellite No.1 in 2006 together with the measured topographical data in 1999 and other data since the 1950s,this paper analyzes mainly the features of landforms around the Manas Lake and the changes of feeding sources of the lake. The results are as follows:(1) Tectonic movement brought about the fundamental geomorphological basis for lacustrine evolution,and the Manas Lake is one of small lakes broken up from the Old Manas Lake due to tectonic movement and drought climate; the Manas Lake had existed before the Manas River flowed into it in 1915. The geomorphologic evidences for evolution of the Manas Lake include:(a) Diluvial fans and old channels at the north of the lake indicate that the rivers originating from the north mountains of the Junggar Basin had fed the Old Manas Lake and now still feed the lake as seasonal rivers; (b) The Old Manas Lake was fed by many rivers originating from the mountains,except for the Manas River,from the evidence of small lakes around the Manas Lake,old channels,alluvial fans,etc.; (c) The elevations of the alluvial and diluvial fans are near to the 280 m a.s.l. and all of the small lakes and lacustrine plains are within the range of the 280 m a.s.l.,which may prove that the elevation of the Old Manas Lake was about 280 m a.s.l.; (d) Core analysis of the Manas Lake area also indicates that the Manas Lake has existed since Late Pleistocene epoch. (2) Analysis on the feeding relations between the lakes and the lacustrine evolution shows that human activities are one of main driving forces of the lacustrine evolution in recent 50 years,and it is the precondition of restoring and maintaining the lacutrine wetlands in the study area to satisfy the feeding of the Baiyang and Manas rivers to the Manas Lake.

  3. Surge-tectonic evolution of southeastern Asia: a geohydrodynamics approach

    Science.gov (United States)

    Meyerhoff, Arthur A.

    The repeated need for ad hoc modifications in plate-tectonic models to explain the evolution of southeastern Asia reveals their inability to fully explain the complex features and dynamics of this region. As one example, the hypothesis does not provide a mechanism to explain the 180° turns and twists along the strike of several foldbelts and island arcs in the region (e.g. Banda arc). Convection-cell configuration renders such 180° contortions and Rayleigh-Bénard-type convection impossible. However, during the last 10 years, new data bearing on the convection-cell problem have become available in the form of seismotomographic images of the earth's interior. These images show that (i) mantle diapirs as proposed by traditional plate-tectonic models do not exist; (ii) there is no discernible pattern of upper or lower mantle convection, and thus no longer an adequate mechanism to move plates; and (iii) the lithosphere above a depth of about 80 km is permeated by an interconnected network of low-velocity channels. Seismic-reflection studies of the low-velocity channels discovered on the seismotomographic images reveal that these channels have walls with a 7.1-7.8 km s -1 P-wave velocity. Commonly, the interiors of the channels are acoustically transparent, with much slower P-wave velocities, in places as low as 5.4 km s -1. The author and co-workers have interpreted the low velocities as evidence for the presence of partial melt in the channels, and they postulated that this melt moves preferentially eastward as a result of the earth's rotation. They named these channels "surge channels" and their new hypothesis for earth dynamics "surge tectonics". Surge channels underlie every type of tectonic belt, which includes mid-ocean ridges, aseismic ridges, continental rifts, strike-slip fracture zones, and foldbelts. In southeastern Asia, surge channels—mainly foldbelts—lie between all platform and cratonic massifs. These massifs, platforms, and tectonics belts

  4. Tectonic evolution of Tethyan tectonic field, formation of Northern Margin basin and explorative perspective of natural gas in Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Analyzing the characteristics of the Tethyan tectonic field, the authors think that the Tethyan tectonic field underwent three evolutional stages: closing of Paleo-Tethys and rifting of Neo-Tethys from early Permian to late Triassic, subduction of Neo-Tethys and collision between the Indian plate and the Eurasia plate from Jurassic to early of low Tertiary, and collision between the Arab plate and the Eurasia plate and the A-type subduction of Indian plate from late of low Tertiary to the present. Combining the evolution of the Tethyan orogenic belt with the characteristics of the Northern Margin basin, it is suggested that the sedimentary and tectonic characteristics and types of the Northern Mar-gin basin are controlled by the formation and evolution of the Tethyan orogenic belt and the ingression of Tethys. The evolution of Northern Margin basin can be divided into three development stages: back-arc foreland basin from late Permian to Triassic, the back-arc fault subsidence and depression from Jurassic to the early of low Tertiary, and the reactive foreland basin from the late of low Tertiary to the present. The Northern Margin basin in the Tethyan tectonic field is an important region for natural gas accumulation, and the Tarim Basin is a part of this region.

  5. Paleomagnetism and Tectonic Evolution of Mexico: Precambrian to Recent

    Science.gov (United States)

    Fucugauchi, J. U.

    2007-05-01

    It is 20yr since publication of the last synthesis of country-wide paleomagnetic data and almost 30yr of first attempt to construct an apparent polar wander path for Mexico. During this time, data has increased ten-fold and a new synthesis may appear long overdue. Mexico constitutes the southern portion of the North American plate, and tectonic models long suggested a complex evolution involving ocean-basin closure, continental collision/break-up, terrane accretion, large-scale motions, orogenic deformation, oceanic plate reorganizations and oceanic basin development. Paleoreconstructions of Atlantic-bordering continents show major overlap of northern South America onto Mexico, highlighting the geometric problem, allocthonous nature and opening room for a diversity of models. Paleomagnetism appears well-suited to tackle these problems, and data had early been used to evaluate tectonic models. Likewise, the larger database is now used to assess models and develop alternatives. This task is greatly aided by new available geochronological, geophysical and geological data. Our new synthesis still shows data gaps, with Paleozoic and Precambrian units poorly represented. Paleomagnetic data and tectonic models require complex large-scale motions of Precambrian and Paleozoic blocks, solutions for opening of Gulf of Mexico and Caribbean Sea, and post-Triassic-Jurassic amalgamation of Mexico and Central America. The southern edge of the North American craton is positioned in northern Mexico, marking the limit for accreted terranes to the south. Possible southern extension of Marathon-Ouachita Paleozoic belt, obscured or truncated when it comes into Mexico, remains unstudied paleomagnetically. Left-lateral motions along faults related to opening of Gulf of Mexico are not supported by paleomagnetism. The Western Cordilleran belt appears laterally displaced in southern US and into Mexico, where the paleomagnetic signature of northward latitudinal translations and clockwise

  6. The Cretaceous and Cenozoic tectonic evolution of Southeast Asia

    Science.gov (United States)

    Zahirovic, S.; Seton, M.; Müller, R. D.

    2014-04-01

    Tectonic reconstructions of Southeast Asia have given rise to numerous controversies that include the accretionary history of Sundaland and the enigmatic tectonic origin of the proto-South China Sea. We assimilate a diversity of geological and geophysical observations into a new regional plate model, coupled to a global model, to address these debates. Our approach takes into account terrane suturing and accretion histories, the location of subducted slabs imaged in mantle tomography in order to constrain the evolution of regional subduction zones, as well as plausible absolute and relative plate velocities and tectonic driving mechanisms. We propose a scenario of rifting from northern Gondwana in the latest Jurassic, driven by northward slab pull from north-dipping subduction of Tethyan crust beneath Eurasia, to detach East Java, Mangkalihat, southeast Borneo and West Sulawesi blocks that collided with a Tethyan intra-oceanic subduction zone in the mid-Cretaceous and subsequently accreted to the Sunda margin (i.e., southwest Borneo core) in the Late Cretaceous. In accounting for the evolution of plate boundaries, we propose that the Philippine Sea plate originated on the periphery of Tethyan crust forming this northward conveyor. We implement a revised model for the Tethyan intra-oceanic subduction zones to reconcile convergence rates, changes in volcanism and the obduction of ophiolites. In our model the northward margin of Greater India collides with the Kohistan-Ladakh intra-oceanic arc at ∼53 Ma, followed by continent-continent collision closing the Shyok and Indus-Tsangpo suture zones between ∼42 and 34 Ma. We also account for the back-arc opening of the proto-South China Sea from ∼65 Ma, consistent with extension along east Asia and the formation of supra-subduction zone ophiolites presently found on the island of Mindoro. The related rifting likely detached the Semitau continental fragment from South China, which accreted to northern Borneo in the mid

  7. Into thin air: Physiology and evolution of alpine insects.

    Science.gov (United States)

    Dillon, Michael E; Frazier, Melanie R; Dudley, Robert

    2006-02-01

    Numerous physical parameters that influence insect physiology vary substantially with altitude, including temperature, air density, and oxygen partial pressure. Here, we review existing literature and present new empirical data to better characterize the high-altitude environment, and then consider how this environment affects the physiology and evolution of insects. Using weather balloon data from fifty-three sites across the globe, we estimate a mean altitudinal temperature lapse rate of 6.0 °C/km. We also present empirically determined lapse rates for P(o(2)) and air density. The temperature decline with elevation may substantially compromise insect thermoregulation at high altitude. However, heat-transfer models predict that lower air density at elevation reduces convective heat loss of insects by to a surprisingly large degree. This effect combined with behavioral thermoregulation and the availability of buffered microhabitats make the net thermal consequences of high-altitude residence strongly context-specific. The decline in P(o(2)) with elevation may compromise insect development and physiology, but its effects are difficult to predict without simultaneously considering temperature and air density. Flying insects compensate for low air densities with both short-term responses, such as increased stroke amplitude (but not wingbeat frequency), and with long-term developmental and/or evolutionary increases in wing size relative to body size. Finally, in contrast to predictions based on Bergmann's Rule, a literature survey of thirty-six insect species suggests that those living in colder, higher altitudes do not tend to have larger body sizes. PMID:21672722

  8. Landscape evolution and bedrock incision in the northern Alpine Foreland since the last 2 Ma

    Science.gov (United States)

    Claude, Anne; Akçar, Naki; Schlunegger, Fritz; Ivy-Ochs, Susan; Kubik, Peter; Christl, Marcus; Vockenhuber, Christof; Dehnert, Andreas; Kuhlemann, Joachim; Rahn, Meinert; Schlüchter, Christian

    2016-04-01

    The landscape evolution of the Swiss Alpine Foreland since the early Pleistocene is of utmost importance for modelling the long-term safety of deep geological repositories for nuclear waste disposal in the northern Alpine Foreland. The oldest Quaternary sediments in the northern foreland are proximal glaciofluvial sediments lying unconformably on Tertiary Molasse or Mesozoic carbonate bedrock. These deposits form topographically distinct and discontinuous isolated plateaus. Terrace morphostratigraphy has a reversed stratigraphic relationship, i.e. today older sediments are located at higher altitudes and vice versa. In this study, we focus on the landscape evolution and long-term bedrock incision in the Swiss Alpine Foreland. We reconstruct the terrace chronology in the foreland at six key locations at different altitudes ranging from 433 m a.s.l. to 675 m a.s.l. by applying cosmogenic depth-profile and isochron-burial dating techniques. First results from these sites indicate that the gravels at studied sites were accumulated in the foreland between 1 and 2 Ma. Based on this reconstructed chronology, long-term bedrock incision rates between 0.1 and 0.2 mm/a were calculated. Thus, we inferred a landscape at that time that was most likely characterized by smoother hillslopes than at present. During the Mid-Pleistocene Revolution (ca. 0.95 Ma), a re-organization of the drainage systems occurred in the Alpine Foreland with a significant lowering of the base level of stream channels. Existing data suggest slightly increased incision rates after this drainage network re-organisation compared to our results. The reconstruction of the chronology at the remaining sites may allow quantifying a pronounced incision as well as the exact timing of the acceleration in the incision rates. REFERENCES Heuberger, S. & Naef, H. (2014). NAB 12-35: Regionale GIS-Kompilation und -Analyse der Deckenschotter-Vorkommen im nördlichen Alpenvorland. Nagra Arbeitsbericht. Kuhlemann, J. & Rahn

  9. Dynamic evolution of shear - extensional tectonics in South China and uranium resource exploration strategic analysis

    International Nuclear Information System (INIS)

    A variety of multi- types, multi-level, multi-era shear - extensional tectonics in south China is developed, the main form of shear-extensional tectonics, and developmental characteristics and metallogenic geodynamic evolution is discovered, and thus uranium resource exploration strategic analysis is conducted

  10. Tectonics

    Science.gov (United States)

    John Dewey will complete his term as editor-in-chief of Tectonics at the end of 1984. Clark Burchfiel's term as North American Editor will also end. Tectonics is published jointly with the European Geophysical Society. This newest of AGU's journals has already established itself as an important journal bridging the concerns of geophysics and geology.James A. Van Allen, president of AGU, has appointed a committee to recommend candidates for both editor-in-chief and North American editor for the 1985-1987 term.

  11. Tectonic and climatic evolution of the Arabian Sea region: an introduction

    OpenAIRE

    Clift, Peter D.; Kroon, Dirk; Gaedicke, Christoph; Craig, Jonathan

    2002-01-01

    ExtractThe evolution of the global oceanic and atmospheric circulation systems has been affected by several forcing processes, with orbital variations being dominant on shorter geological time scales. Over longer periods of time (> 10 Ma) the tectonic evolution of the solid Earth has been recognized as the major control on the development of the global climate system. Tectonic activity acts in one of two different ways to influence regional and global climate. The earliest solid Earth-clim...

  12. 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

  13. Eastern Ishtar Terra: Tectonic evolution derived from recognized features

    Science.gov (United States)

    Vorderbruegge, R. W.; Head, James W.

    Previous analyses have recognized several styles and orientations of compressional deformation, crustal convergence, and crustal thickening in Eastern Ishtar Terra. An east to west sense of crustal convergence through small scale folding, thrusting, and buckling is reflected in the high topography and ridge-and-valley morphology of Maxwell Montes and the adjacent portion of Fortuna Tessera. This east to west convergence was accompanied by up to 1000 km of lateral motion and large scale strike-slip faulting within two converging shear zones which has resulted in the present morphology of Maxwell Montes. A more northeast to southwest sense of convergence through large scale buckling and imbrication is reflected in large, northwest-trending scarps along the entire northern boundary of Ishtar Terra, with up to 2 km of relief present at many of the scarps. It was previously suggested that both styles of compression have occurred at the expense of pre-existing tessera regions which have then been overprinted by the latest convergence event. The difference in style is attributed mostly to differences in the properties of the crust converging with the tessera blocks. If one, presumably thick, tessera block converges with another tessera region, then the widespread, distributed style of deformation occurs, as observed in western Fortuna Tessera. However, if relatively thin crust (such as suggested for the North Polar Plains converges with thicker tessera regions, then localized deformation occurs, as reflected in the scarps along Northern Ishtar Terra. The purpose is to identify the types of features observed in Eastern Ishtar Terra. Their potential temporal and spatial relationships, is described, possible origins for them is suggested, and how the interpretation of some of these features has led to the multiple-style tectonic evolution model described is shown.

  14. Eastern Ishtar Terra: Tectonic evolution derived from recognized features

    International Nuclear Information System (INIS)

    Previous analyses have recognized several styles and orientations of compressional deformation, crustal convergence, and crustal thickening in Eastern Ishtar Terra. An east to west sense of crustal convergence through small scale folding, thrusting, and buckling is reflected in the high topography and ridge-and-valley morphology of Maxwell Montes and the adjacent portion of Fortuna Tessera. This east to west convergence was accompanied by up to 1000 km of lateral motion and large scale strike-slip faulting within two converging shear zones which has resulted in the present morphology of Maxwell Montes. A more northeast to southwest sense of convergence through large scale buckling and imbrication is reflected in large, northwest-trending scarps along the entire northern boundary of Ishtar Terra, with up to 2 km of relief present at many of the scarps. It was previously suggested that both styles of compression have occurred at the expense of pre-existing tessera regions which have then been overprinted by the latest convergence event. The difference in style is attributed mostly to differences in the properties of the crust converging with the tessera blocks. If one, presumably thick, tessera block converges with another tessera region, then the widespread, distributed style of deformation occurs, as observed in western Fortuna Tessera. However, if relatively thin crust such as suggested for the North Polar Plains converges with thicker tessera regions, then localized deformation occurs, as reflected in the scarps along Northern Ishtar Terra. The purpose is to identify the types of features observed in Eastern Ishtar Terra. Their potential temporal and spatial relationships, is described, possible origins for them is suggested, and how the interpretation of some of these features has led to the multiple-style tectonic evolution model described is shown

  15. Tectonic and climatic control on geomorphological and sedimentary evolution of the Mercure basin, southern Apennines, Italy

    Science.gov (United States)

    Robustelli, Gaetano; Ermolli, Elda Russo; Petrosino, Paola; Jicha, Brian; Sardella, Raffaele; Donato, Paola

    2014-06-01

    The morpho-tectonic and sedimentary evolution of the Mercure intramontane basin (Calabria-Lucania boundary, southern Apennines) has been assessed through facies analysis, morphostratigraphy and geomorphological correlation with adjacent areas. The Mercure basin, one of the most active seismogenic zones of the southern Apennines, is a favorable area for reconstructing the main stages of landscape evolution of the axial zone because of its capability to record changes in base level during the Quaternary. In addition, the presence of both erosional and depositional Palaeosurfaces is a useful marker for reconstructing tectonic and morphogenetic events, and hence to detect the role played by tectonics and climate in its genesis, evolution and extinction. The present study identifies the key role of tectonics and denudation, combined with high-frequency floods, as mechanisms controlling alluvial sedimentation in the study area. During endorheic conditions, denudational processes driven by pulses of extensional deformation of the basin margin caused strong alluvial inputs that resulted in the development of alluvial fans. Alluvial facies are mainly characterized by turbulent, subaerial, hyperconcentrated flood flows deposited during the glacial, semi-arid conditions of MIS 14. The retrogradational stacking pattern of the alluvial system indicates decreasing rates of tectonic activity along with declining river gradients. The Mercure coalescing alluvial fans were inundated by lake transgression during MIS 13 in response to (i) abrupt tectonic subsidence at the basin margins and (ii) large decrease of coarse sediment supply due to the interplay among climate, tectonics and catchment size changes. In this regard, it is suggested that tectonic control on the drainage network along with climate and long-term slope evolution may have caused marked pulses in sediment supply, thus influencing the arrangement of facies associations in the sedimentary succession. In addition, the

  16. Linking basin evolution to plate tectonic processes in (northern) Africa

    OpenAIRE

    Gravråk, Mariann

    2011-01-01

    Several sedimentary basins in Africa are classified as intracratonic basins, but no conclusive formation mechanism has been identified for these basin types. Tectonic subsidence curves may help in unraveling formation mechanisms or identify tectonic forcing for these basins. This thesis presents and analyses basin subsidence curves for basins in the interior of Africa and near its passive margins. A backstripping program has been written to solve the backstripping equations needed to make the...

  17. Preliminary discussion on tectonic-magmatic evolution with respect to metallogenesis of rich uranium deposits in Xiazhuang ore-field

    International Nuclear Information System (INIS)

    The regional tectonic setting and main geologic features are described. It is suggested that Xiazhuang ore-field is characterized by shallow thermo-upwelling extensional tectonics, and the occurrence and the distribution of rich-large uranium deposits are controlled by the specific tectonic-magmatic evolution under shallow thermo-upwelling extensional tectonics, and those of late-stage rich-large uranium deposits are constrained by the tectonic-magmatic evolution of taphrogenic extensional tectonics. On the above basis, a metallogenic model for rich-large uranium deposit has been set up, and four metallogenically prospective area for rich-large uranium deposits have been predicted

  18. Igneous and tectonic evolution of Venusian and terrestrial coronae

    Science.gov (United States)

    Kargel, J. S.; Komatsu, G.

    1992-01-01

    A great variety of tectonic and volcanic features have been documented on Venus. It is widely appreciated that there are close spatial associations among certain types of tectonic structures and some classes of volcanic flows and constructs. Coronae are endowed with a particularly rich variety of volcanism. It is thought that coupled tectonic and volcanic aspects of coronae are cogenetic manifestations of mantle plumes. An outstanding feature of most venusian coronae is their circular or elliptical shape defined by peripheral zones of fracturing and/or folding. Some coronae are composite, consisting of two or more small coronae within a larger enclosing corona, suggesting complex histories of structured diapirism analogous in some ways to salt dome tectonics. Coronae range widely in size, from smaller than 100 km to over 1000 km in diameter. Volcanic features associated with venusian coronae include lunar-like sinuous rilles, thin lava flows, cinder cone-like constructs, shield volcanos, and pancake domes. Several types of volcanic features are often situated within or near a single corona, in many instances including land-forms indicating effusions of both low- and high-viscosity lavas. In some cases stratigraphic evidence brackets emplacement of pancake domes during the period of tectonic development of the corona, thus supporting a close link between the igneous and tectonic histories of coronae. These associations suggest emplacement of huge diapirs and massive magmatic intrusions, thus producing the tectonic deformations defining these structures. Igneous differentiation of the intrusion could yield a range of lava compositions. Head and Wilson suggested a mechanism that would cause development of neutral buoyancy zones in the shallow subsurface of Venus, thereby tending to promote development of massive igneous intrusions.

  19. Geodynamic controls on a salt giant formation. The Messinian salinity crisis and the tectonic evolution of the westernmost Mediterranean

    Science.gov (United States)

    Garcia-Castellanos, Daniel

    2016-04-01

    The landlocked location of the Mediterranean is presumed to be the result of the southward retreat of subducted Tethyan lithospheric slabs after the collision between Europe and Africa. The western end of the Alpine orogeny (the Gibraltar Arc) shaped the last marine connection to the ocean during the upper Miocene, but in this complex tectonic region, the dominant polarity of subduction (Tethys underneath Iberia/Europe/Anatolia) might not be accomplished, based on plate reconstructions, mantle tomography, and the present position of the Kabylies and the Alboran nappes. This tectonic evolution determined the vertical motions purportedly responsible for the restriction of the Mediterranean and the widespread salt accumulation during the Messinian Salinity Crisis. Following the concept of isostasy, the enormous and rapid mass redistribution implied by the crisis should have induced in turn remarkable vertical motions of the Mediterranean margins. While the predicted isostatic motions during the crisis range in the order of hundreds of meters, little evidence has been documented so far. The mechanical response of the Iberian margins can be inferred by using crustal and lithospheric cross sections derived from potential fields (gravity and geoid anomalies), heatflow, and topography modeling. The preliminary results are consistent with a low rigidity of the lithosphere, in agreement with their young thermomechanical age. These rigidity values are then used for a first-order estimation of the vertical motions associated to the accumulation of salt and the possible partial evaporation of the water column during the crisis. Recent seismic stratigraphic data show that the Balearic promontory hosts a unique set of intermediate-depth basins where halite deposited in smaller amounts than in the deeper basins. If future drillings provide more precise constraints on the paleobathymetry of the sedimentary units before and after the crisis, the various proposed models for its

  20. The Tectonic and Climatic Evolution of High Plateaux

    Science.gov (United States)

    Bershaw, John

    High topography significantly affects climate and atmospheric circulation, often separating areas of intense precipitation from relatively arid rainshadows inland. Temporal variations in climate on high plateaux have been inferred from both rocks and ice and may be related to changes in global climate, local atmospheric circulation, and/or changes in surface elevation. Constraints on how and when surface topography was generated not only provide insight into the relationship between high plateaux and climate, but help us distinguish between different geodynamic mechanisms responsible for their formation. The following research employs multiple techniques across the Andean Plateau, the Pamir, and Tibetan Plateau, to better understand both the tectonic evolution of high plateaux and how they affect climate and atmospheric circulation, particularly in continental settings. The Andean Plateau in South America is the second highest and most extensive topographic feature on Earth. Paleoelevation constraints from fossil leaf physiognomy and stable isotopes of sedimentary carbonate suggest that significant surface uplift of the northern Andean plateau, on the order of 2.5 +/- 1 km, occurred between ˜10.3 and 6.4 million years ago (Ma). South American teeth from modem and extinct mammal taxa spanning from the Oligocene (˜29 Ma) to present were collected as they preserve a record of surface water isotopes and the type of plants that animals ingested. Previous studies have shown that the isotopic composition of oxygen (delta18O) in modern precipitation and surface waters decreases systematically with increasing elevations across the central Andes. Results from high elevation sites show substantially more positive delta18O values for late Oligocene tooth samples compared to <10 Ma tooth delta18O values. Late Oligocene teeth collected from low elevation sites in southeast Brazil show delta18O values within 2 per mil (‰) of contemporaneous teeth collected at high elevation

  1. Volcanism and Tectonic Evolution in the North Qilian Mountains during Ordovician Period

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The Ordovician marine volcanic rocks in the north Qilian mountains are discussed in this paper. According to geology, petrotectonic assemblage and geochemistry, a new model about plate tectonic evolution of the north Qilian mountains is set up. The Ordovician marine volcanic rocks in the north Qilian mountains which characterized by the geological features of tectonic melange of continent to continent collision underwent complicated tectonic movement, and can be classified into three main kinds of petrotectonic assemblages. During Ordovician period, north Qilian area was a polyisland ocean which consisted of three ocean basins separated by the middle microcontinental blocks.

  2. Tectonic evolution and mantle structure of the Caribbean

    NARCIS (Netherlands)

    van Benthem, S.; Govers, R.; Spakman, W.; Wortel, R.

    2013-01-01

    We investigate whether predictions of mantle structure from tectonic reconstructions are in agreement with a detailed tomographic image of seismic P wave velocity structure under the Caribbean region. In the upper mantle, positive seismic anomalies are imaged under the Lesser Antilles and Puerto Ric

  3. Holocene Tectonic and Sedimentary Evolution of Coastal San Diego

    Science.gov (United States)

    Maloney, J. M.; Driscoll, N. W.; Brothers, D. S.; Babcock, J. M.; Kent, G.

    2010-12-01

    The shelf and nearshore region of San Diego, California, between La Jolla cove in the north and the U.S.- Mexico border in the south, is an important ecological and economic resource. It contains two of the largest kelp forests in southern California and lies offshore miles of popular beaches. Understanding the interplay between tectonic and sedimentary processes in this area is critical because it will allow us to assess how other forcing functions such as the rapid sea level rise (2 - 3 mm/yr) and predicted climate change associated with global warming are impacting the kelp and nearshore environments. The fault architecture and sedimentary deposits offshore San Diego have been mapped using high-resolution seismic CHIRP profiling. The mapped area lies within the inner California Continental Borderland (CCB), which is characterized by a system of basins and ridges and extensive strike-slip faulting. The CHIRP data clearly images several splays of the Coronado Bank Fault Zone (CBFZ), a major fault in the area, which show recent activity in the upper 30 m of sediment with the most recent deformation at ~4 m below seafloor. Several sediment packages as deep as 50 m below the seafloor are imaged and place important constraints on tectonic deformation and sediment dispersal in the region as well as the earthquake recurrence interval on the CBFZ. Exposed and buried wavecut terraces identified on numerous CHIRP profiles, which can be correlated to terraces mapped regionally, provide insight into tectonic uplift rates and sea-level fluctuations. Finally, the extensive kelp forests offshore Mount Soledad and Point Loma occur where hardgrounds are exposed at the seafloor as a consequence of tectonic uplift. High resolution mapping offshore San Diego is providing new insight into the complex interplay between tectonics, sedimentation, and biology in this ecologically diverse region.

  4. Sequence stratigraphy and paleogene tectonic evolution of the Transylvanian Basin (Romania, eastern Europe)

    Science.gov (United States)

    Proust, Jean-Noël; Hosu, Alexandru

    1996-09-01

    The Transylvanian Basin of Romania belongs to the 800 × 400 km wide Pannonian domain of the European Alpine megasuture bordered to the east and the north by the Carpathians. It represents a digitation of the epicontinental Tethyan seaways locally connected during the Palaeogene to the peripheral foredeep troughs. During that time, it was filled up by a 500-m-thick sediment pile organized into three shallow marine and non-marine facies alternations. Each evolved from alluvial fans to restricted marine and outer marine environments. They are dated from Lutetian to Chattian times. The study is focused on the lowermost alternation onlapping the basal, post-Maastrichtian unconformity. This alternation consists of the superimpossition of a thick retrogradational and a thin progradational depositional system. The retrogradational depositional system grades upwards from stacked, fault-controlled deposits of alluvial fan, ephemeral stream, salina and sabkha, and restricted marine bioclastic shales. The progradational depositional system is composed of outer marine to estuarine sandstones and shales. The two depositional systems are bounded at their tops by two baselevel change unconformities underlain by highly mobile, low relief sandstone bodies that were deposited in shoal belts. These two unconformities mark significant changes in the regime of the subsidence. These are, respectively, a baselevel rise or 'drowning' unconformity where the shoal deposits were associated with oolitic ironstones and glauconitic shales that typify basin starvation during a period of maximum basin drowning, and a baselevel fall or 'uplifting' unconformity where the bioclastic shoal deposits were buried by alluvial flood plain deposits that characterize periods of relief rejuvenation tentatively attributed to compressive events. This bimodal succession is interpreted in terms of underfilled-overfilled stages related to intraplate tectonic deformation. The underfilled stage corresponds to the

  5. Formation and evolution of mesozoic volcanic basins in Gan-Hang tectonic belt

    International Nuclear Information System (INIS)

    The author mainly discusses the principle model for the formation and the evolution of Mesozoic volcanic basins in the Gan-Hang Tectonic Belt, and describes the distinct evolution features between the internal and external sites of volcanic basins, the natural relation between the down-warped, down-faulted, collapse volcanic basins and volcanic domes, the relationship between the formation of inter layered fractured zones of the volcanic cover and the evolution of volcanic basins

  6. Tectonic evolution of chagannuoer basin and its relationship to uranium metallogenetic process

    International Nuclear Information System (INIS)

    Starting from the tectonic evolution of the basin, authors expound the controlling role of the tectonic evolution of the basin upon factors closely associated with uranium metallogenesis in the basing such as the structure of the basin, filling sequence of cover deposit, hydrologic conditions and the mobilization and migration of uranium etc. It is suggested that the basin structure created favorable conditions for uranium ore-formation in Chagannuoer basin, it also controlled the genetic types of uranium mineralization, the distribution area and development intensity of uranium mineralization in the basin. Features of tectonic evolution resulted in the development of two type uranium mineralizations in the basin, i.e. phreatic oxidation and local interlayer oxidation types. (authors)

  7. DETERMINATION OF TECTONIC EVOLUTION OF A SEDIMENTARY BASIN FROM SANDSTONE COMPONENTS

    Institute of Scientific and Technical Information of China (English)

    Lei SHAO; Chuanlian LIU; Karl STATTEGGER

    2001-01-01

    Terrigenous sedimentary rocks are the dominant rock types in continental sedimentary basin, the components of these rocks are mainly controlled by source rocks. Through systematically analyzing the components of terrigenous sedimentary rocks, the tectonic evolution of a sedimentary basin can be reconstructed. The Turpan Basin was examined using sandstone petrological and geochemical methods.The consistency of the petrographical and geochemical results shows that the tectonic evolution of the basin can be subdivided into four stages: the first stage covers the Permian; the second stage the Triassic;the third stage from the Lower Jurassic to Upper Jurassic and the fourth stage from the Cretaceous to Tertiary. The components of sandstones among these stages are different, which reflect the influence of tectonics movements on the evolution of the basin and surrounding areas.

  8. Active tectonics west of New Zealand's Alpine Fault: South Westland Fault Zone activity shows Australian Plate instability

    Science.gov (United States)

    De Pascale, Gregory P.; Chandler-Yates, Nicholas; Dela Pena, Federico; Wilson, Pam; May, Elijah; Twiss, Amber; Cheng, Che

    2016-04-01

    The 300 km long South Westland Fault Zone (SWFZ) is within the footwall of the Central Alpine Fault (<20 km away) and has 3500 m of dip-slip displacement, but it has been unknown if the fault is active. Here the first evidence for SWFZ thrust faulting in the "stable" Australian Plate is shown with cumulative dip-slip displacements up to 5.9 m (with 3 m throw) on Pleistocene and Holocene sediments and gentle hanging wall anticlinal folding. Cone penetration test (CPT) stratigraphy shows repeated sequences within the fault scarp (consistent with thrusting). Optically stimulated luminescence (OSL) dating constrains the most recent rupture post-12.1 ± 1.7 ka with evidence for three to four events during earthquakes of at least Mw 6.8. This study shows significant deformation is accommodated on poorly characterized Australian Plate structures northwest of the Alpine Fault and demonstrates that major active and seismogenic structures remain uncharacterized in densely forested regions on Earth.

  9. Geodynamic evolution of the Earth over the Phanerozoic:Plate tectonic activity and palaeoclimatic indicators

    Institute of Scientific and Technical Information of China (English)

    Christian Vérard; Cyril Hochard; Peter O. Baumgartner; Gérard M. Stamplfi

    2015-01-01

    During the last decades, numerous local reconstructions based on ifeld geol-ogy were developed at the University of Lausanne (UNIL). Team members of the UNIL partici-pated in the elaboration of a 600 Ma to present global plate tectonic model deeply rooted in geological data, controlled by geometric and kinematic constraints and coherent with forces acting at plate boundaries. In this paper, we compare values derived from the tectonic model (ages of oceanic lfoor, production and subduction rates, tectonic activity) with a combination of chemical proxies (namely CO2, 87Sr/86Sr, glaciation evidence, and sea-level variations) known to be strongly in-lfuenced by tectonics. One of the outstanding results is the observation of an overall decreas-ing trend in the evolution of the global tectonic activity, mean oceanic ages and plate velocities over the whole Phanerozoic. We speculate that the decreasing trend relfects the global cooling of the Earth system. Additionally, the parallel between the tectonic activity and CO2 together with the extension of glaciations conifrms the generally accepted idea of a primary control of CO2 on climate and highlights the link between plate tectonics and CO2 in a time scale greater than 107 yr. Last, the wide variations observed in the reconstructed sea-lfoor production rates are in contradiction with the steady-state model hypothesized by some.

  10. High Alpine landscape evolution in Val di Sole (Trentino, Italy) during the Holocene based on charcoal, soil chemistry and mineralogy

    OpenAIRE

    Favilli, F; Egli, M; P. Cherubini; Mirabella, A; Sartori, G; Giaccai, D

    2008-01-01

    We investigated five soil profiles developed on subalpine and alpine environment in northern Italy (Val di Sole, Trentino) with respect to their radiocarbon ages, soil mineralogy and chemistry. The purpose of this research was to document chemical weathering in a periglacial environment and to use the clay mineralogy and radiocarbon ages to explain landscape evolution. The time of developing of the soil horizons, obtained by the extraction of the stable pool of the soil organic matter (SOM) r...

  11. Understanding the Interior Evolution of Mercury from Its Tectonic History

    Science.gov (United States)

    Byrne, P. K.; Klimczak, C.; Sengor, A. M. C.; Hauck, S. A., II; Solomon, S. C.

    2015-12-01

    The surface of Mercury provides compelling insight into the planet's interior. Excluding impact craters and basins, the most prominent landforms on Mercury are tectonic; these features are distributed globally and crosscut all major surface units. More than seven years of flyby and orbital observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft show that tectonism on Mercury is overwhelmingly shortening in nature; extensional structures occur only within volcanically flooded impact craters and basins, in part the result of thermal contraction of thick plains units. Shortening structures show no coherent, planet-wide pattern, although many have an approximately north-south orientation, and some form fold-and-thrust belts thousands of kilometers long. Even so, their widespread distribution points to a global source of stress, primarily from global contraction in response to secular interior cooling. Some of the largest such landforms are 2-3 km in relief and hundreds of kilometers long, their underlying thrust faults penetrating 30-40 km into the lithosphere. Shortening landforms as small as hundreds of meters in length have been identified during MESSENGER's low-altitude campaign; the crisp morphology of these features indicates that thrust faulting, and thus global contraction, continued until the geologically recent. Displacement-length scaling analysis shows that Mercury's shortening landforms have accommodated a reduction in planetary radius of up to 7 km since the end of the late heavy bombardment. Such a magnitude of contraction is more consistent with models of global contraction from interior cooling and partial core crystallization than pre-MESSENGER estimates of tectonic shortening. Notably, the emplacement of major volcanic plains deposits on Mercury ended globally by 3.6 Ga, consistent with the onset of a state of net horizontal lithospheric compression that served to inhibit the vertical ascent and

  12. Evolution of ancient Lake Ohrid: a tectonic perspective

    Science.gov (United States)

    Hoffmann, N.; Reicherter, K.; Fernández-Steeger, T.; Grützner, C.

    2010-10-01

    Lake Ohrid Basin is a graben structure situated in the Dinarides at the border of the Former Yugoslavian Republic of Macedonia (FYROM) and Albania. It hosts one of the oldest lakes in Europe and is characterized by a basin and range-like geological setting together with the halfgraben basins of Korca, Erseka and Debar. The basin is surrounded by Paleozoic metamorphics in the northeast and north and Mesozoic ultramafic, carbonatic and magmatic rocks in the east, northwest, west and south. Paleocene to Pliocene units are present in the southwest. With the basin development, Neogene sediments from Pliocene to recent deposited in the lows. There are three major deformation phases: (A) NW-SE shortening from Late Cretaceous to Miocene; (B) uplift and diminishing compression during Messinian - Pliocene; (C) vertical uplift and (N)E-(S)W extension from Pliocene to recent led to the basin formation. Neotectonic activity of the study area concentrates on N-S trending normal faults that bound the Ohrid Basin eastwards and westwards. Seismic activity with moderate to strong events is documented during the last 2000 yrs; the seismic hazard level is among the highest in Albania and Macedonia. Activity of the youngest faults is evidenced by earthquake data and field observations. Morphotectonic features like fault scarps, a stepped series of active normal faults, deformed paleosols, a wind gap and fault-related hydrothermal activity are preserved around Lake Ohrid and allow delineating the tectonic history. It is shown that the Lake Ohrid Basin can be characterized as a seismogenic landscape. This paper presents a tectonic history of the Lake Ohrid Basin and describes tectonic features that are preserved in the recent landscape. The analysis of morphotectonic features is used to derive the deformation history. The stratigraphy of the area is summarized and concentrates on the main units.

  13. Evolution of ancient Lake Ohrid: a tectonic perspective

    Directory of Open Access Journals (Sweden)

    N. Hoffmann

    2010-10-01

    Full Text Available Lake Ohrid Basin is a graben structure situated in the Dinarides at the border of the Former Yugoslavian Republic of Macedonia (FYROM and Albania. It hosts one of the oldest lakes in Europe and is characterized by a basin and range-like geological setting together with the halfgraben basins of Korca, Erseka and Debar. The basin is surrounded by Paleozoic metamorphics in the northeast and north and Mesozoic ultramafic, carbonatic and magmatic rocks in the east, northwest, west and south. Paleocene to Pliocene units are present in the southwest. With the basin development, Neogene sediments from Pliocene to recent deposited in the lows. There are three major deformation phases: (A NW–SE shortening from Late Cretaceous to Miocene; (B uplift and diminishing compression during Messinian – Pliocene; (C vertical uplift and (NE–(SW extension from Pliocene to recent led to the basin formation. Neotectonic activity of the study area concentrates on N–S trending normal faults that bound the Ohrid Basin eastwards and westwards. Seismic activity with moderate to strong events is documented during the last 2000 yrs; the seismic hazard level is among the highest in Albania and Macedonia. Activity of the youngest faults is evidenced by earthquake data and field observations. Morphotectonic features like fault scarps, a stepped series of active normal faults, deformed paleosols, a wind gap and fault-related hydrothermal activity are preserved around Lake Ohrid and allow delineating the tectonic history. It is shown that the Lake Ohrid Basin can be characterized as a seismogenic landscape. This paper presents a tectonic history of the Lake Ohrid Basin and describes tectonic features that are preserved in the recent landscape. The analysis of morphotectonic features is used to derive the deformation history. The stratigraphy of the area is summarized and concentrates on the main units.

  14. Evolution of ancient Lake Ohrid: a tectonic perspective

    Directory of Open Access Journals (Sweden)

    N. Hoffmann

    2010-06-01

    Full Text Available Lake Ohrid Basin is a graben structure situated in the Dinarides at the border of the Former Yugoslavian Republic of Macedonia (FYROM and Albania. It hosts one of the oldest lakes in Europe and is characterized by a basin and range-like geological setting together with the half-graben basins of Korca, Erseka and Debar. The basin is surrounded by Palaeozoic metamorphics in the northeast and north and Mesozoic ultramafic, carbonatic and magmatic rocks in the east, northwest, west and south. Palaeocene to Pliocene units are present in the southwest. With the basin development, Neogene sediments from Pliocene to recent deposited in the lows. Three major deformation phases lead to the basin formation: A NW–SE shortening from Late Cretaceous to Miocene; B uplift and diminishing compression during Messinian - Pliocene; C vertical uplift and (NE–(SW extension from Pliocene to recent. Neotectonic activity of the study area concentrates on N–S trending normal faults that flank the Ohrid Basin on the east and west. Seismic activity with moderate to strong events is documented during the last 2000 y; the seismic hazard level is among the highest of the Balkan Peninsula. Activity of the youngest faults is evidenced by earthquake data and field observations. Morphotectonic features like a wind-gap, fault scarps, a stepped series of active normal faults, deformed palaeosols, and fault-related hydrothermal activity are preserved around Lake Ohrid and allow delineating the tectonic history. It is shown that the Lake Ohrid Basin can be characterized as a seismogenic landscape. This paper presents a tectonic history of the Lake Ohrid Basin and describes tectonic features that are preserved in the recent landscape. The analysis of morphotectonic features is used to derive the deformation history. The stratigraphy of the area is summarized and concentrates on the main units.

  15. Regional geologic-tectonic evolution and its relation to sandstone-type uranium mineralization in Shamai area

    International Nuclear Information System (INIS)

    The basic regional geologic-tectonic framework and the evolution of Shamai area are introduced in this paper, and two (NE-and NNE-trending) tectonic belts are recognized in the study region. It is suggested that Meso-Cenozoic basins in the region are originated from the NWW-SEE extension. The relation of tectonic evolution to sandstone-type uranium mineralization is discussed in this paper as well

  16. Molecular bases for parallel evolution of translucent bracts in an alpine "glasshouse" plant Rheum alexandrae (Polygonaceae)

    Institute of Scientific and Technical Information of China (English)

    Bing-Bing LIU; Lars OPGENOORTH; Georg MIEHE; Dong-Yuan ZHANG; Dong-Shi WAN; Chang-Ming ZHAO; Dong-Rui JIA

    2013-01-01

    Parallel evolution provides an excellent framework to infer the genetic bases of adaptive traits and understand the importance of natural selection in shaping current biodiversity.The upper leaves of the "glasshouse plants" transform into translucent bracts that show numerous adaptions in alpine habitats.It remains unknown whether similar molecular changes occur under the parallel bract evolution of different "glasshouse" species.In this study,we compared the results on phenotypic and physiological differences and presented the results of cDNA-AFLP analyses of transcriptional changes between translucent bracts and normal leaves in Rheum alexandrae.We also examined the homologous candidate genes with the same expression changes between this species and another "glasshouse" species,R.nobile.We found that bracts ofR.alexandrae are similar to those ofR.nobile in anatomical features:chloroplasts have degenerated and chlorophyll contents are greatly reduced,which suggests that foliar photosynthetic functions in bracts of both species have been reduced or totally altered.Among the 6000 transcript-derived fragments (TDFs) in bracts and leaves of R.alexandrae,420 (7%) were differentially expressed (up-or downregulated) between bracts and normal leaves.There were a total of 13 homologous TDFs with the same expression changes between R.alexandrae and the previously studied R.nobile.Except for the two that were not functionally annotated,eight of the homologous TDFs were found to be involved in stress and defense responses whereas the other three were related to photosynthesis.The up-or downregulation of these candidate genes was highly congruent with anatomical characteristics and adaptive functions of the bracts found for "glasshouse" plants.These findings suggested that the "glasshouse" phenotypes may have common molecular bases underlying their parallel evolution of similar adaptive functions and highlighted the importance of the natural selection in producing such

  17. Mesozoic basin evolution and tectonic mechanism in Yanshan, China

    Institute of Scientific and Technical Information of China (English)

    LIU; Shaofeng; LI; Zhong; ZHANG; Jinfang

    2004-01-01

    The Mesozoic basins in Yanshan, China underwent several important tectonic transformations, including changes from a pre-Late Triassic marginal cratonic basin to a Late Triassic-Late Jurassic flexural basin and then to a late Late Jurassic-Early Cretaceous rift basin. In response to two violent intraplate deformation at Late Triassic and Late Jurassic, coarse fluvial depositional systems in Xingshikou and Tuchengzi Formations were deposited in front of thrust belts. Controlled by transform and extension faulting, fan deltas and lacustrine systems were deposited in Early Cretaceous basins. The composition of clastic debris in Late Triassic and Late Jurassic flexural basins respectively represents unroofing processes from Proterozoic to Archean and from early deposited, overlying pyroclastic rocks to basement rocks in provenance areas. Restored protobasins were gradually migrated toward nearly NEE to EW-trending from Early Jurassic to early Late Jurassic. The Early Cretaceous basins with a NNE-trending crossed over early-formed basins. The Early-Late Jurassic and Early Cretaceous basins were respectively controlled by different tectonic mechanisms.

  18. Tectonic evolution of the Sicilian Maghrebian Chain inferred from stratigraphic and petrographic evidences of Lower Cretaceous and Oligocene flysch

    Directory of Open Access Journals (Sweden)

    Puglisi Diego

    2014-08-01

    Full Text Available The occurrence of a Lower Cretaceous flysch group, cropping out from the Gibraltar Arc to the Balkans with a very similar structural setting and sedimentary provenance always linked to the dismantling of internal areas, suggests the existence of only one sedimentary basin (Alpine Tethys s.s., subdivided into many other minor oceanic areas. The Maghrebian Basin, mainly developed on thinned continental crust, was probably located in the westernmost sector of the Alpine Tethys. Cretaceous re-organization of the plates triggered one (or more tectonic phases, well recorded in almost all the sectors of the Alpine Tethys. However, the Maghrebian Basin seems to have been deformed by Late- or post-Cretaceous tectonics, connected with a “meso-Alpine” phase (pre-Oligocene, already hypothesized since the beginning of the nineties. Field geological evidence and recent biostratigraphic data also support this important meso- Alpine tectonic phase in the Sicilian segment of the Maghrebian Chain, indicated by the deformations of a Lower Cretaceous flysch sealed by Lower Oligocene turbidite deposits. This tectonic development is emphasized here because it was probably connected with the onset of rifting in the southern paleomargin of the European plate, the detaching of the so-called AlKaPeCa block (Auct.; i.e. Alboran + Kabylian + Calabria and Peloritani terranes and its fragmentation into several microplates. The subsequent early Oligocene drifting of these microplates led to the progressive closure of the Maghrebian Basin and the opening of new back-arc oceanic basins, strongly controlled by extensional processes, in the western Mediterranean (i.e. Gulf of Lion, Valencia Trough, Provençal Basin and Alboran Sea.

  19. Natural selection and neutral evolution jointly drive population divergence between alpine and lowland ecotypes of the allopolyploid plant Anemone multifida (Ranunculaceae.

    Directory of Open Access Journals (Sweden)

    Jamie R McEwen

    Full Text Available Population differentiation can be driven in large part by natural selection, but selectively neutral evolution can play a prominent role in shaping patters of population divergence. The decomposition of the evolutionary history of populations into the relative effects of natural selection and selectively neutral evolution enables an understanding of the causes of population divergence and adaptation. In this study, we examined heterogeneous genomic divergence between alpine and lowland ecotypes of the allopolyploid plant, Anemone multifida. Using peak height and dominant AFLP data, we quantified population differentiation at non-outlier (neutral and outlier loci to determine the potential contribution of natural selection and selectively neutral evolution to population divergence. We found 13 candidate loci, corresponding to 2.7% of loci, with signatures of divergent natural selection between alpine and lowland populations and between alpine populations (Fst  = 0.074-0.445 at outlier loci, but neutral population differentiation was also evident between alpine populations (FST  = 0.041-0.095 at neutral loci. By examining population structure at both neutral and outlier loci, we determined that the combined effects of selection and neutral evolution are associated with the divergence of alpine populations, which may be linked to extreme abiotic conditions and isolation between alpine sites. The presence of outlier levels of genetic variation in structured populations underscores the importance of separately analyzing neutral and outlier loci to infer the relative role of divergent natural selection and neutral evolution in population divergence.

  20. Time constraints on the tectonic evolution of the eastern Sierras Pampeanas (Central Argentina)

    DEFF Research Database (Denmark)

    Siegesmund, Siegfried; Steenken, A; Martino, R D;

    2010-01-01

    cycle in the neighbouring Sierra de San Luis and has not affected the titanite ages. The PTt evolution can be correlated with the plate tectonic processes responsible for the formation of the Pampean orogene, i.e., the accretion of the Pampean basement to the Río de La Plata craton (M2) and the later...

  1. The tectonic evolution of a critical segment of the Dinarides-Alps connection: Kinematic and geochronological inferences from the Medvednica Mountains, NE Croatia

    Science.gov (United States)

    Gelder, I. E.; Matenco, L.; Willingshofer, E.; Tomljenović, B.; Andriessen, P. A. M.; Ducea, M. N.; Beniest, A.; Gruić, A.

    2015-09-01

    The transition zone between the Alps and Dinarides is a key area to investigate kinematic interactions of neighboring orogens with different subduction polarities. A study combining field kinematic and sedimentary data, microstructural observations, thermochronological data (Rb-Sr and fission track), and regional structures in the area of Medvednica Mountains has revealed a complex polyphase tectonic evolution. We document two novel stages of extensional exhumation. The first stage of extension took place along a Late Cretaceous detachment following the late Early Cretaceous nappe stacking, burial, and greenschist facies metamorphism. Two other shortening events that occurred during the latest Cretaceous-Oligocene were followed by a second event of extensional exhumation, characterized by asymmetric top-NE extension during the Miocene. Top-NW thrusting took place subsequently during the Pliocene inversion of the Pannonian Basin. The Cretaceous nappe burial, Late Cretaceous extension, and the Oligocene(-Earliest Miocene) contraction are events driven by the Alps evolution. In contrast, the latest Cretaceous-Eocene deformation reflects phases of Dinaridic contraction. Furthermore, the Miocene extension and subsequent inversion display kinematics similar with observations elsewhere in the Dinarides and Eastern Alps. All these processes demonstrate that the Medvednica Mountains were affected by Alpine phases of deformations to a much higher degree than previously thought. Similarly with what has been observed in other areas of contractional polarity changes, such as the Mediterranean, Black Sea, or New Guinea systems, the respective tectonic events are triggered by rheological weak zones which are critical for localizing the deformation created by both orogens.

  2. Multiphase salt tectonic evolution in NW Germany: seismic interpretation and retro-deformation

    Science.gov (United States)

    Mohr, M.; Kukla, P. A.; Urai, J. L.; Bresser, G.

    2005-12-01

    The Central European Basin is a classic area of salt tectonics, characterized by heterogeneous structural evolution and complex salt movement history. We studied an area on its SW margin, based on prestack depth-migrated 2D and 3D seismic data. We use seismic interpretation and retro-deformation to obtain a better understanding of salt tectonics, structural control, and sedimentary response in this region. The first phase of salt tectonic evolution started with two main events of NW-SE extension and rafting in the Triassic before the Upper Bunter and before the Upper Muschelkalk. Rafting was accompanied by first salt diapirism and an increased sedimentary thickness adjacent to the salt structure. After salt supply ceased updip to the salt structure, a mini-basin grew in the intra-raft area. This sedimentary differential loading caused salt movement and growth of a pillow structure basinward. The second phase of salt movement was initiated by the formation of a NNW-SSE striking basement graben in the Middle Keuper that triggered reactive diapirism, the breakthrough of the pillow’s roof and salt extrusion. The following downbuilding process was characterized by sedimentary wedges with basal unconformities, onlap structures and salt extrusions that ceased in the Jurassic. The third and latest phase of salt tectonic evolution was activated in the Late Cretaceous to Lower Tertiary by compressional tectonics indicated by salt rise and a small horizontal shortening of the diapir. The interpreted salt tectonic processes and the resulting geometries can now be better tied in with the regional heterogeneous framework of the basin.

  3. The Records of the Tectonic Evolution From the Volcanics in Qiangtang Basin, Tibet

    Institute of Scientific and Technical Information of China (English)

    He Zhonghua; Yang Deming; Li Cai; Pu Zhongyu

    2000-01-01

    The volcanism in Qiangtang Basin is very frequent due to the divergence and subduction of the various plates. The study indicates that these volcanics are formed in different tectonic settings: 1 )Hercynian volcanics are mainly basalts and are formed in the intraplate and intercontinental rift. 2 ) Indosinian volcanics markedly vary in the distribution and composition and reflect transitional MORB and island are environments respectively. 3) Yanshanian volcanics consist predominantly of basalts, andesites, dacites and rhyolites and are characterized by calc- alkaline volcanic suite, indicating island arc setting. 4)Himalayan volcanics are complicated and associated with intraplate orogency. The volcanism provides important tectonic information for recognizing the evolution of Qiangtang Basin.

  4. Tectonic evolution and mantle structure of the Caribbean

    Science.gov (United States)

    Benthem, Steven; Govers, Rob; Spakman, Wim; Wortel, Rinus

    2013-06-01

    investigate whether predictions of mantle structure from tectonic reconstructions are in agreement with a detailed tomographic image of seismic P wave velocity structure under the Caribbean region. In the upper mantle, positive seismic anomalies are imaged under the Lesser Antilles and Puerto Rico. These anomalies are interpreted as remnants of Atlantic lithosphere subduction and confirm tectonic reconstructions that suggest at least 1100 km of convergence at the Lesser Antilles island arc during the past ~45 Myr. The imaged Lesser Antilles slab consists of a northern and southern anomaly, separated by a low-velocity anomaly across most of the upper mantle, which we interpret as the subducted North America-South America plate boundary. The southern edge of the imaged Lesser Antilles slab agrees with vertical tearing of South America lithosphere. The northern Lesser Antilles slab is continuous with the Puerto Rico slab along the northeastern plate boundary. This results in an amphitheater-shaped slab, and it is interpreted as westward subducting North America lithosphere that remained attached to the surface along the northeastern boundary of the Caribbean plate. At the Muertos Trough, however, material is imaged until a depth of only 100 km, suggesting a small amount of subduction. The location and length of the imaged South Caribbean slab agrees with proposed subduction of Caribbean lithosphere under the northern South America plate. An anomaly related to proposed Oligocene subduction at the Nicaragua rise is absent in the tomographic model. Beneath Panama, a subduction window exists across the upper mantle, which is related to the cessation of subduction of the Nazca plate under Panama since 9.5 Ma and possibly the preceding subduction of the extinct Cocos-Nazca spreading center. In the lower mantle, two large anomaly patterns are imaged. The westernmost anomaly agrees with the subduction of Farallon lithosphere. The second lower mantle anomaly is found east of

  5. Balanced Cross Section for Restoration of Tectonic Evolution in the Southwest Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    Wu Shiguo; Ni Xianglong; Guo Junhua

    2007-01-01

    On the basis of the multi-channel seismic data and the other data, using 2DMove software,the tectonic evolution in three seismic profiles was restored since Pliocene. The tectonic restoration results show that: (1) the initial active center lay in the west slope and then was transferred to east and south via trough center during the evolution process; (2) several main normal faults controlled the evolution of the southern Okinawa Trough; (3) since Late Pliocene, the southern Okinawa Trough has experienced two spreading stages. The early is depression in Early-Middle Pleistocene and the late is back-arc spreading in Late Pleistocene and Holocene, which is in primary oceanic crust spreading stage.

  6. Tectonic evolution of chagandelesu area and uranium concentration, Inner Mongolia

    International Nuclear Information System (INIS)

    The Chagandelesu area is located at the convergence site of two tectonic units. It accepted thick littoral and shallow marine sediments composed of carbonaceous dolomitic and volcanic materials--Zhartai Group during Middle Proterozoic period in an EW-trending aulacogen, and uranium showed the first time preconcentration. In the region, considerable intrusion of acid-intermediate magma and extensive regional metamorphism and migmatization appeared at above 1.4 Ga age, and uranium was pre-concentrated for the second time. The second episode of Middle Hercynian orogeny at the end of Late Carboniferous resulted in the formation of Hanula and Yingba batholithic massifs making the uranium be pre-concentrated for the third time. In the early period of Early Cretaceous, the continental down-faulted basins were formed, the sediments which contained abundant organic matter and uranium was pre-concentrated for the fourth time. At last, during the Himalayan neotectonic period, there occurred the acidization of paleoclimate and by the action of surface water and ground-water, uranium was extensively re-mobilized, transported and concentrated forming major sandstone-hosted uranium deposits in Chagandelesu area

  7. Escape tectonics and foreland basin evolution: The Austrian-German Molasse basin

    Science.gov (United States)

    Ortner, Hugo

    2016-04-01

    The Alpine peripheral foreland basin formed during Eocene collision of the lower, European plate and the upper, Adriatic plate. Two marine to continental megasequences fill the basin. The transition form deep marine to continental deposits of the first megasequence at the Early - Late Oligocene boundary has been related to a change from predominant horizontal to vertical movements in the core of the orogenic wedge. The second megasequence is, however, poorly understood, and different models have been put forward. I present an alternative explanation for the development of this second megacycle, based on an analysis of the Subalpine Molasse thrust belt east of the Rhine river (Ortner et al., 2015). The main characteristics of the Subalpine Molasse thrust belt are: 1) A frontal anticline/thrust started to develop during deposition of the older, marine portion of the second megasequence. Structures continued to grow throughout deposition of the younger, continental part of the megasequence. Structural growth is documented by growth strata. 2) The thrusts in the Subalpine Molasse evolved in a break-back sequence. 3) The amount of shortening during depositon of the second megasequence reduces from 40-50 km near the Rhine valley to zero in the east in the Salzburg area. The onset of the second megasequence in the foreland north of the Subalpine Molasse thrust belt is characterized by an angular unconformity documenting a tilt of the foreland toward the orogen, and therefore ongoing flexure of the lower plate. East of the eastern end of the Subalpine Molasse thrust belt, the deposits of the second megasequence are in a horizontal position, lower plate flexure had stopped. In the internal part of the Alpine orogenic wedge, shortening, exhumation and E-directed stretching of the Tauern Window as a consequence of escape tectonics was active. Most probably shortening was transferred from the Alpine front into the zone of lateral escape, causing the break-back thrust sequence

  8. Cenozoic structures and the tectonic evolution of the eastern North Sea

    DEFF Research Database (Denmark)

    Clausen, O.R.; Nielsen, S.B.; Egholm, D.L.;

    2011-01-01

    or cover tectonism took place. Our objectives are thus 1) to analyze the interaction between basement and cover structures, and if possible 2) to relate the structures to the regional tectonic evolution. The Zechstein evaporites pinch out onto the Ringkøbing-Fyn High, which in the eastern North Sea...... including decompaction in the Central Graben along the Arne-Elin trend shows that two phases of basement related inversion took place duringthe Paleocene-Eocene and the Oligocene. Halokinetics and differential compaction across the Paleogene inversion structure explain later tectonic signals...... detachment surfaces withinthe sedimentary succession and basement structures. Here we define basement structures by offsets in the pre Zechstein succession. Cover structures are confined to the post Zechstein succession, or part hereof, and detach internally along surfaces in the post Zechstein succession...

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

    NARCIS (Netherlands)

    Sissingh, W.

    2006-01-01

    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

  10. Tectonic Evolution and Petroleum Systems in the Junggar Basin

    Institute of Scientific and Technical Information of China (English)

    WANG Weifeng; CHEN Yequan

    2004-01-01

    The Junggar basin is located in the northern part of Xinjiang of China. It is part of the Kazakstan plate,surrounded by the Paleozoic folded mountains: the Halaart, Zayier and Chepaizi Mountains in the northwest, the Qingelidi and Karamaili Mountains in the northeast, and the Tianshan Mountains in the south. In different evolution stages, the basin's types are different, and the stratigraphy and deposition are also different. From the Carboniferous to Tertiary the basin has in turn gone through rift basin, collision foreland basin, intraplate depression basin and regenerated foreland basin. Based on an analysis of thermal evolution history and buried history of the source rocks, three major periods of oil generation are found in the basin. According to the characteristics of source rock distribution, evolution, oil-source correlation, structure and multi-phase and mixed pools, the Junggar basin could be divided into 4 composite petroleum systems. Due to the variation in sedimentary facies, difference in structural patterns and development histories, the petroleum pool-forming conditions in different areas and horizons are greatly different, so are the petroleum pool types,the accumulation mechanisms in different areas and horizons.

  11. High-resolution seismic analysis of the coastal Mecklenburg Bay (North German Basin): the pre-Alpine evolution

    Science.gov (United States)

    Zöllner, H.; Reicherter, K.; Schikowsky, P.

    2008-09-01

    The pre-Alpine structural and geological evolution in the northern part of the North German Basin have been revealed on the basis of a very dense reflection seismic profile grid. The study area is situated in the coastal Mecklenburg Bay (Germany), part of the southwestern Baltic Sea. From the central part of the North German Basin to the northern basin margin in the Grimmen High area a series of high-resolution maps show the evolution from the base Zechstein to the Lower Jurassic. We present a map of basement faults affecting the pre-Zechstein. The pre-Alpine structural evolution of the region has been determined from digital mapping of post-Permian key horizons traced on the processed seismic time sections. The geological evolution of the North German Basin can be separated into four distinct periods in the Rerik study area. During Late Permian and Early Triassic evaporites and clastics were deposited. Salt movement was initiated after the deposition of the Middle Triassic Muschelkalk. Salt pillows, which were previously unmapped in the study area, are responsible for the creation of smaller subsidence centers and angular unconformities in the Late Triassic Keuper, especially in the vicinity of the fault-bounded Grimmen High. In this area, partly Lower Jurassic sediments overlie the Keuper unconformably. The change from extension to compression in the regional stress field remobilized the salt, leading to a major unconformity marked at the base of the Late Cretaceous.

  12. Geology and Tectonic Evolution of the Kazdaǧ Massif (NW Anatolia)

    Science.gov (United States)

    Erdoğan, B.; Akay, E.; Hasözbek, A.; Satır, M.; Siebel, W.

    2009-04-01

    and paleogeographic evolution of the southern part of the northwestern Anatolia. Geologica Romana 27, 13-80 Bingöl, E. (1971) Classification of age determination methods and application of Rb/Sr and K/Ar methods in Kazdağ. Bulletin of the Mineral Research and Exploration Institute of Turkey 14, 1-16 (in Turkish) Duru, M., Pehlivan, Ş., Şentürk, Y., Yavaş, F. ve Kar, H. (2004) New results on the lithostratigraphy of the Kazdağ Massif in northwest Turkey. Turkish Journal of Earth Sciences 13, 177-186 Okay, A.I and Monie, P. (1997) Early Mesozoic subduction in the eastern Mediterranean: Evidence from Triassic eclogite in northwest Turkey. Geology 25, 595-598 Okay, A.I and Satır, M. (2000) Coeval plutonism and metamorphism in a latest Oligocene metamorphic core complex in northwestern Turkey. Geological Magazine 137, 495-516 Okay, A.I, Siyako, M and Burkan, K.A. (1991) Geology and tectonic evolution of the Biga Peninsula, northwestern Turkey. Bulletin of the Technical University of İstanbul 44, 191-256 Okay, A.I, Monod, O and Monie, P. (2002) Triaasic blueschists and eclogites from northwestern Turkey: vestiges of the Paleo-Tethyan subduction. Lithos 64, 155-178 Okay, A.I, Satır, M., Maluski, H., Sıyako, M., Monie, P., Metzger, R., Akyüz, S., (1996) Paleo- and Neo-Tethyan events in northwestern Turkey: Geologic and geochronologic constrains. The Tectonic Evolution of Asia, 420-441 Topuz, G, Altıner, D, Satır, M, and Schwartz, W.H. (2004) Low-grade metamorphic rocks from the Pulur Complex, NE Turkey: implications for the pre-Liassic evolution of the Eastern Pontides. International Journal of Earth Science, 93, 72-91 Yaltırak C. and Okay A.İ (1994) Geology of the Paleo-Tethyan units in the north of Edremit Bay. Bulletin of the Technical University of İstanbul , 3/1, 67-79 (in Turkish)

  13. Sedimentary and tectonic evolution of ancient Lake Ohrid (Macedonia / Albania)

    OpenAIRE

    Lindhorst, Katja; Krastel, Sebastian; Wagner, Bernd

    2010-01-01

    Lake Ohrid (Macedonia / Albania) is probably the oldest lake in Europe (2-5 Ma), and is considered an important sedimentary archive to study the evolution of a graben system over several million years. Multichannel seismic profiles were acquired in 2007 and 2008 showing that the lake can be divided into two main parts, the slope areas and a large, deep central basin. The basin is bordered by the major eastern and western graben fault, additional faults were identifi ed in the northern part...

  14. Overview of geology and tectonic evolution of the Baikal-Tuva area.

    Science.gov (United States)

    Gladkochub, Dmitry; Donskaya, Tatiana

    2009-01-01

    This chapter provides the results of geological investigations of the main tectonic units of the Baikal-Tuva region (southwestern part of Siberia) during the last decades: the ancient Siberian craton and adjacent areas of the Central Asian Orogenic belt. In the framework of these main units we describe small-scale blocks (terranes) with focus on details of their inner structure and evolution through time. As well as describing the geology and tectonics of the area studied, we give an overview of underwater sediments, neotectonics, and some phenomena of history and development of the Baikal, Khubsugul, Chargytai, and Tore-Chol Lakes basins of the Baikal-Tuva region. It is suggested that these lakes' evolution was controlled by neotectonic processes, modern seismic activity, and global climate changes. PMID:19198771

  15. Towards an Integrated Model of Earth's Thermo-Chemical Evolution and Plate Tectonics

    Science.gov (United States)

    Tackley, P. J.; Xie, S.

    2001-05-01

    It has long been a challenge for geodynamicists, who have typically modeled homogeneous mantles, to explain the geochemical evidence for the existence of several distinct chemical reservoirs, in terms of a dynamically and chemically self-consistent model. While the mixing behavior of generalized tracers has received much attention in the modeling community, a recent trend has been towards mantle convection models that track the evolution of specific chemical species, both major and minor, and can thus be related to geochemical observations. However, obtaining realistic chemical evolution in such models is dependent on their having a reasonable representation of plate tectonic behavior since the recycling of oceanic crust and complementary depleted residuum is a key process in Earth that other terrestrial planets may lack. In general, this has required inserting plate motions by hand in models. In recent years, however, we have learned how to perform numerical simulations of mantle convection in which plate tectonic behavior is introduced self-consistently through plastic yielding of the lithosphere. In this presentation, models of mantle convection that combine a treatment of geochemical evolution with self-consistently generated plate tectonics, will be presented. Preliminary results indicate that the system can self-consistently evolve regions which have a HIMU-like signature as well as regions with a high He3/He4 ratio.

  16. Basaltic Magmatism: The Dominant Factor in the Petrologic and Tectonic Evolution of the Earth

    Science.gov (United States)

    Lowman, Paul D., Jr.

    2003-01-01

    Silicate bodies such as the Moon, Mars, probably Mercury, and possibly Venus, appear to have evolved in three main stages: a first (felsic) differentiation, a late heavy bombardment, and a second (basaltic) differentiation. It has been proposed that the Earth underwent a similar sequence. This paper argues that the second differentiation, basaltic magmatism, has dominated the petrologic and tectonic evolution of the Earth for four billion years. A global andesitic crust, formed during and after accretion of the planet, was disrupted by major impacts that triggered mantle upwelling and sea-floor spreading about 4 billion years ago. The oceanic crust collectively has since been formed by basaltic volcanism, from spreading centers and mantle plumes. However, the continental crust has also been greatly affected. Basaltic underplating has promoted anatexis and diapiric intrusion of granitoids in granite-greenstone terrains, as well as providing heat for regional metamorphism. Basaltic intrusions, such as the Nipissing diabase of the Sudbury area, have added to the thickness of continental crust. Satellite magnetic surveys suggest that there are more such basaltic intrusions than previously realized; examples include the Bangui anomaly of central Africa and the Kentucky anomaly. Basaltic overplating from mafic dike swarms has repeatedly flooded continents; had it not been for erosion, they would be covered with basalt as Venus is today. The tectonic effects of basaltic volcanism on continents have only recently been realized. The World Stress Map project has discovered that continents are under horizontal compressive stress, caused by push from mid-ocean ridges, i.e., by basaltic volcanism. The stress fields are generally uniform over large intraplate areas, and could contribute to intraplate tectonism. Seafloor spreading has demonstrably been effective for at least 200 million years, and ridge push thus a contributor to tectonic activity for that long. Collectively, the

  17. Pre-collisional extensional tectonics in convergent continental margins: the cretaceous evolution of the central cordillera of the Colombian Andes

    OpenAIRE

    Zapata Henao, Sebastian

    2015-01-01

    Abstract: The Cretaceous tectonic evolution of the Northern Andes continental margin is characterized by continuous convergence that allowed the formation of continental volcanic arcs, back arc basins, extensional divergent tectonics and accretion of exotic terranes. Such a record, particularly the extensional phases, is commonly hidden by the overimposition of deformational events associated with evolution of the subduction configuration, collision of exotic terranes and strike slip fragment...

  18. The relationship between tectonic-thermal evolution and sandstone-type uranium ore-formation in Ordos basin

    International Nuclear Information System (INIS)

    The comprehensive study of the volcanic activities, the geothermal field, the thermal flow field, the paleogeo-thermal activity and the tectonic evolution of the Ordos basin indicates that the tectonic-thermal evolution of the Ordos basin has offered the basis for the fluid-fluid and fluid-rock mutual reactions, and has created favourable conditions for the formation of organic mineral resources and sandstone-type uranium deposits. Especially, the tectonic-thermal event during middle-Late Jurassic to Cretaceous played an important role in providing uranium source material, and assisting the migration, the concentration and precipitation of uranium and uranium ore-formation. (authors)

  19. Alpine tourism

    Directory of Open Access Journals (Sweden)

    Andrea Macchiavelli

    2009-06-01

    Full Text Available The spectacular increase in tourism in the Alps in recent decades has been founded mainly on the boom in skiing, resulting in both strong real estate development and an increasing array of infrastructures and ski runs. Today the ski market seems to have virtually reached saturation point and the winter sports sector needs to diversify its offer through innovation. After a review of the main factors of change in mountain tourism, the paper presents a grid for interpreting the life cycle of alpine destinations, identifying the phases that characterize their evolution. The conditions that may favour innovation in alpine tourism are then identified, as well as the contradictions that frequently accompany them. In most cases, innovation is the result of a process that begins within the alpine community, frequently encouraged and supported by national and international institutions and with whose help structural difficulties are successfully overcome.La forte croissance qu’ont connue les pays alpins dans les dernières décennies a surtout été fondée sur l’offre des activités du ski, avec comme conséquence, un massif développement immobilier et la multiplication d’infrastructures et de pistes. Aujourd’hui, le marché du ski semble arriver à saturation, la Convention alpine a mis un frein à la poursuite du développement des domaines skiables et on observe donc avec intérêt la diversification de l’offre soutenue par l’innovation. Après avoir rappelé les facteurs de changement en cours les plus significatifs dans le tourisme montagnard, l’article présente une grille interprétative de l’évolution des destinations touristiques alpines, identifiant les phases qui ont caractérisé son développement. Ensuite, l’article propose une réflexion sur certaines conditions qui peuvent favoriser l’innovation dans le tourisme alpin, ainsi que sur les contradictions qui accompagnent souvent ces conditions. Dans la plupart des cas

  20. 水星构造特征及演化%Tectonic Features and Evolution of Mercury

    Institute of Scientific and Technical Information of China (English)

    闫丹; 曾佐勋; 胡才志; 徐大良; 胡烨

    2009-01-01

    Mercury, the innermost terrestrial planet of the solar system, has the similar surface to the Moon and the similar interior to the Earth. It exhibits five important tectonic features: (1)pervasive impact craters, (2)a global grid system, (3)lobate scarps, only found on Mercury, (4)structures associated with the Caloris Basin and (5)local extensional feature. Most of the structural features of terrestrial planet except the Earth is formed in the early-middle history of the planets. The tectonic evolution of small planetary bodies is usually interpreted as the result of their thermal evolution with external perturbations such as large impacts or tidal effects. On this basis this paper discusses the tectonic history of Mercury by summaring and analysing its tectonic features.%水星是离太阳最近的类地行星,它有着类似月球的外表和类似地球的内部,其重要的构造特征主要表现在以下方面:广泛分布的撞击坑;全球线性构造(格子构造)体系;叶片状悬崖;与Caloris盆地相关的构造;局部的拉张构造,其中叶片状悬崖是仅存在于水星的独特构造.类地行星(除地球以外)的构造形迹主要形成于星球历史的早、中期,同时小行星体的构造演化通常被认为是行星热演化以及外部作用(如强烈撞击或者潮汐)共同作用的结果.

  1. A new model for the dynamic evolution of Chinese lithosphere: 'continental roots-plume tectonics'

    Science.gov (United States)

    Deng, J. F.; Mo, X. X.; Zhao, H. L.; Wu, Z. X.; Luo, Z. H.; Su, S. G.

    2004-05-01

    continental rifting, such a relationship is inherent to the continental roots-plume tectonics model. It is further proposed that the formation of orogenic lithosphere roots triggered eastward extrusion of the asthenosphere along the 400-km depth mantle interface, and, in response to subduction at the eastern margin, produces plume-like upwelling beneath eastern China. We suggest that processes involved in continental roots-plume tectonics are directly responsible for the formation and evolution of the Eurasian supercontinent.

  2. Space-time evolution of meso-cenozoic extensional tectonics and distributions of uranium mineralizations in southeastern China

    International Nuclear Information System (INIS)

    With the theory of continental extensional tectonics, the distribution regularities of Meso-Cenozoic extensional tectonics of different types in southeastern China and their space-time evolution were discussed. then according to the known isotope age data of uranium mineralizations in the area, the relationship between the process of extensional tectonics and regional uranium metallogenesis, as well as the corresponding relations in space and time between extensional tectonics and uranium deposits of different types are analyzed. Based on the analysis above, the authors believe that the favourable tectonic environment created by the extensional tectonics is the fundamental reason that results in uranium metallogenesis. The pulse activities of the extensional tectonics and its subsequent magmatism determine the multi-stage processes of uranium mineralizations. The successive development of the extensional tectonics in different areas decides the temporal sequence and spatial distribution of uranium deposits of different types. The authors suggest that the uranium mineralizations of different types in southeastern China are characterized by an united ore-forming mechanism due to the apparent control of extensional tectonics to the regional uranium metallogenesis

  3. Sill genesis in the Paleoproterozoic tectonic evolution of the Onega Trough, Baltic shield

    Science.gov (United States)

    Poleshchuk, A. V.

    2011-07-01

    This study considers the role of sill genesis in the tectonic evolution of the Onega Trough during the Middle to Late Paleoproterozoic (Jatulian-Vepsian). The evolution of the Onega Trough is divided into three stages: pre-sill, or preparatory, subsynchronous, and post-sill. Sill magmatism manifested itself most completely at the subsynchronous stage of the evolution of the Onega Trough within the initial, principal, and final phases of sill genesis. Sill formation followed the stage of regional downwarping of the area reaching its maximum during the Early Ludicovian. Paragenesis of sills and high carbon shungite rocks was accompanied by the formation of peperites, while sills influenced the structure of the host rocks. A model reflecting the regular patterns of manifestations of sill genesis identified in the Onega Trough has been proposed.

  4. Andean subduction orogeny: feedbacks between tectonics, relief evolution and global climate

    Science.gov (United States)

    Lacassin, Robin; Armijo, Rolando; Coudurier-Curveur, Aurélie; Carrizo, Daniel

    2016-04-01

    The Andean subduction margin, largest tectonic relief on the Earth (13 km vertically from the trench to the Altiplano) has a stepped morphology, which results of the evolution over the past 50 Myr of two parallel flat-ramp thrust systems, at the - previously unidentified - West Andean Thrust (WAT), and at the subduction interface. The evolution of those thrusts appears concomitant with increasing aridity in the Atacama Desert, which keeps a large-scale record of interplaying tectonics and Cenozoic climate change. The coastal morphology is dominated by the Atacama Bench, a giant uplifted terrace at 1-2km asl. Geomorphic and climatic data, numerical experiments of drainage formation are consistent with the development of a flat Atacama morphology close to sea level, interrupted at ≤10 Ma by tectonic uplift prevailing to the present. This suggests recent trench-ward relief growth by incorporation of the coastal Atacama Bench to the Andes reliefs. Thrust splay structures and other complexities above the subduction interface may explain this relief growth, as well as the distribution of asperities under the oceanward forearc, and the down-dip segmentation of coupling and seismicity on the megathrust. Combining those results with geological knowledge at the scale of the whole Central Andes, we show that the Andean orogeny results from protracted processes of bivergent crustal shortening in a wide region squeezed between the rigid Marginal Block and the S America Plate. The overall growth curve of Andean orogeny over the past 50 Myr appears synchronous with the onset of the "ramp-shaped" temperature decrease since the Early Eocene climatic optimum. Andean growth and global cooling may have operated under the same forcing mechanism at plate-scale, involving viscous flow in the mantle. But Andean growth appears modulated by climatic feedbacks causative of stepwise reductions of erosive power over the Andean margin. The first of such events is coeval with Late Eocene

  5. Integrating Geochemical and Geodynamic Numerical Models of Mantle Evolution and Plate Tectonics

    Science.gov (United States)

    Tackley, P. J.; Xie, S.

    2001-12-01

    The thermal and chemical evolution of Earth's mantle and plates are inextricably coupled by the plate tectonic - mantle convective system. Convection causes chemical differentiation, recycling and mixing, while chemical variations affect the convection through physical properties such as density and viscosity which depend on composition. It is now possible to construct numerical mantle convection models that track the thermo-chemical evolution of major and minor elements, and which can be used to test prospective models and hypotheses regarding Earth's chemical and thermal evolution. Model thermal and chemical structures can be compared to results from seismic tomography, while geochemical signatures (e.g., trace element ratios) can be compared to geochemical observations. The presented, two-dimensional model combines a simplified 2-component major element model with tracking of the most important trace elements, using a tracer method. Melting is self-consistently treated using a solidus, with melt placed on the surface as crust. Partitioning of trace elements occurs between melt and residue. Decaying heat-producing elements and secular cooling of the mantle and core provide the driving heat sources. Pseudo-plastic yielding of the lithosphere gives a first-order approximation of plate tectonics, and also allows planets with a rigid lid or intermittent plate tectonics to be modeled simply by increasing the yield strength. Preliminary models with an initially homogeneous mantle show that regions with a HIMU-like signature can be generated by crustal recycling, and regions with high 3He/4He ratios can be generated by residuum recycling. Outgassing of Argon is within the observed range. Models with initially layered mantles will also be investigated. In future it will be important to include a more realistic bulk compositional model that allows continental crust as well as oceanic crust to form, and to extend the model to three dimensions since toroidal flow may alter

  6. Miocene to recent tectonic and sedimentary evolution of the Anaximander Seamounts; eastern Mediterranean Sea

    Science.gov (United States)

    Cranshaw, Jennifer

    This thesis is focused on the Messinian to Recent tectonic and sedimentary evolution of the Anaximander Mountains and surrounding environs in the eastern Mediterranean Sea. It is based on processing of high-resolution seismic reflection data and the interpretation and mapping of seismic reflection profiles collected from this area during the 2001 and 2007 research cruises. The data show that the greater Anaximander Mountains region experienced a short interval of tectonic quiescence during the Messinian when a thin evaporite unit was deposited across a major erosional surface. This phase of limited tectonic activity ended in the latest Miocene and was replaced by an erosional phase. Major unconformities in the area are interpreted to develop during the desiccation of the eastern Mediterranean associated with the so-called Messinian salinity crisis. During the early Pliocene, the region experienced an increase in tectonic activity, dominated by transpression. Small amounts of growth observed in Pliocene-Quaternary sediments suggested that the tectonic activity remained low during the early Pliocene-Quaternary. However, the extensive growth strata wedges developed in older sediments indicate a period of accelerated tectonic activity during the mid-late Pliocene-Quaternary. This study suggests that the Anaximander Mountain (sensu stricto ) and the Anaximenes Mountain developed during the Pliocene-Quaternary as the result of a crustal-scale thick-skinned linked imbricate thrust fan. The development of back thrusts in both mountains heightened the seafloor morphology of these submarine mountains and brought Eocene-Oligocene sediments into the core of these mountains. The Sim Erinc Plateau represents a 30-40 km wide transpressional fault zone developed during the Pliocene-Quaternary. In this region the corrugated seafloor morphology observed in the multibeam bathymetry map is the reflection of high-angle faults. It is speculated that this transpressional fault zone

  7. Tectonic evolution of the western boundary of the Attico-Cycladic complex (Lavrio, Greece)

    Science.gov (United States)

    Scheffer, Christophe; Vanderhaeghe, Olivier; Tarantola, Alexandre; Lanari, Pierre; Ponthus, Leandre; France, Lyderic; Photiades, Adonis

    2015-04-01

    The Lavrio peninsula, South East of Athens, is located along the western boundary of the Attic-Cycladic Metamorphic Complex in the internal zone of the Hellenic orogenic belt, at the intersection between thrusts and detachments. It is thus a perfect target to decipher the tectonic evolution of an orogenic wedge from tectonic accretion to gravitational collapse. The nappe stack is overlain by a non-metamorphic limestone and is made, from top to bottom by (i) an ophiolitic melange, (ii) the Lavrio tectonic unit dominated by schists and displaying mineral paragenesis typical of blueschist facies, (iii) the Kamariza tectonic unit dominated by marbles and affected by pervasive greenschist facies metamorphism. The Lavrio and Kamariza tectonic units are juxtaposed by a low-angle mylonitic to cataclastic detachement. A more detailed investigation of the relationships between mineral paragenesis and microstructures indicates that the transition from the Lavrio to the Kamariza tectonic units, across the low-angle detachment, is marked by progressive transposition of the blueschist facies fabric coeval with retrogression under greenschist facies conditions. Indeed, the Kamariza unit is characterized by a relatively steep foliation associated with isoclinal folds of weakly organized axial orientation that is partially to totally transposed into a shallow dipping foliation bearing a N-S trending lineation. The degree of transposition increases from top to bottom and is particularly marked at the transition from the Lavrio to the Kamariza unit across the low-angle detachement. The blueschist facies foliation of the Lavrio schists is underlined by glaucophane and HP phengite intergrown with chlorite crystals. The Kamariza tectonic unit is dominated by LP phengite intergrown with chlorite but contains relics of the blueschist mineral paragenesis. Detailed microprobe mapping of the composition of the phengite and chlorite crystals reveal distinct variations of the PT conditions

  8. Hinterland tectonics and drainage evolution recorded by foreland basin archives: the Neogene Siwaliks of the Himalaya

    Science.gov (United States)

    Huyghe, Pascale; van der Beek, Peter; Matthias, Bernet; Catherine, Chauvel; Jean-Louis, Mugnier; Laurent, Husson; François, Chirouze

    2014-05-01

    Provenance analysis and detrital thermochronology of detrital synorogenic sediments, derived from erosion of mountain belts and deposited in surrounding sedimentary basins, are well-established methods to examine the exhumation history of convergent zones, tectonic activity and the associated evolution of the drainage network. We have conducted multidisciplinary studies on magnetostratigraphically dated sections throughout the Neogene Siwalik foreland basin of the Himalayan belt since more than 10 years. Sr, Nd and Hf isotopes are used as provenance indicators, providing information on the nature and size of catchment basins and their evolution through time in response to tectonics. Detrital zircon and apatite thermochronology provides constraints on exhumation rates in the hinterland of the Himalaya and the deformation of the Sub-Himalayan foreland basin. Throughout the Himalaya, detrital zircons from the Siwaliks generally show three age peaks: two static peaks (i.e., displaying constant peak ages through time), and a moving peak. The latter shows a constant lag time of ~4 m.y. corresponding to source-area exhumation rates on the order of 1.8 km/my, while the two static peaks respectively reveal a major 15-20 Ma exhumation event in the belt, the significance of which is still debated, and inheritance of pre-Himalayan ages that indicate recycling of Tethyan sediments. Therefore, our ZFT results suggest that the exhumation dynamics are broadly similar throughout the Himalaya since at least 13 m.y, as also shown by the Bengal Fan detrital sediment record. We relate this switch in tectonic regime to the destabilization of the Himalayan wedge that is rendered overcritical as a response to the transience of dynamic topography caused by the deforming underlying Indian slab. Nonetheless, in detail, the timing of thrusting in the Siwalik domain is delayed by about 1 my eastward as demonstrated by both structural and apatite fission-track data, suggesting overall eastward

  9. Wave characteristics and tectonic-sedimentation evolution of foreland thrust fault of Micang Mountain

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper,the technology of wave process method for sedimentation is first adopted in the research of the foreland thrust fault of Micang Mountain with respect of oil and reservoir’s formation and tectonic and sedimentary evolution. From the fluctuation characteristics,we could make conclusions in the foreland thrust belt of Micang Mountain that,there existed 2 first-order sedimentary cycles (220 Ma),corresponding to Caledonian-Hercynian and Indo-Chinese-Yanshan-Himalayan tectonic cycles respec-tively; there existed 4 second-order sedimentary cycles (10 Ma),corresponding to two sedimentation peak period and two denudation peak periods in research zone; there existed 12 third-order sedimen-tary cycles (35 Ma) and 21 fourth-sedimentary cycles (20 Ma). These 33 cycles in the research zone corresponded to the sedimentation-denudation process in different periods,furthermore,their fluctua-tion characteristics bore the genetic relationship with the development law of source,reservoir and cap rocks: the source rock had the tendency to develop at the turning part between wave crest and wave trough,or at the superposition of wave turning part in different periods,presenting like "X"; most res-ervoir rocks developed at the place of wave peak; the development of cap rock was located in the wave trough on the right of sedimentation-denudation datum line. As a result,through the application of wave process method for sedimentation,we could rediscover the understanding of the tectonic and sedimentary evolution from another prospective,meanwhile,it enables to make prediction about the development rule of source,reservoir and cap rocks,which means a significant importance to the re-search of oil and reservoir’s forming condition.

  10. Tectonic-thermal evolution from the northeast region of Minas Gerais and South of Bahia

    International Nuclear Information System (INIS)

    The northeast region of Minas Gerais and South Bahia are centered to the east of 420 00'WGr, between parallels 150 and 180. Its tectonic-thermal evolution is presented here with the support of stratigraphy/lithology, structural analysis, petrography, petrochemistry, regional metamorphism/retro metamorphism and radio chronology. It is pointed out that the evolution occurred in a mobile belt initiating its history in the terminal Archean up to Inferior Proterozoic. The northeast of the region attained crustal stability during 1700 My up to 1800 My (Sao Francisco Craton) meanwhile the rest of the zone kept mobilized till upper proterozoic times. Radio chronological studies suggest for the post tectonic granitic rocks, ages from the brasiliano cycle as well as for those pre-existing rocks which suffered isotopic regeneration and metamorphose in that same cycle an original age from Archean to inferior proterozoic times, except for those which are situated in the northeast part of the region. Petrochemical data point to an origin from sedimentary processes for the majority of the metamorphosed rocks in this region. (author)

  11. Tectonic evolution of Caledonian Palaeohigh in the Sichuan Basin and its relationship with hydrocarbon accumulation

    Directory of Open Access Journals (Sweden)

    Li Wei

    2014-10-01

    Full Text Available The Caledonian Palaeohigh is an important gas exploration domain of Sinian and Lower Paleozoic in western Central Sichuan Basin where gas discoveries have been made successively in recent years. In order to sort out the relationship between the tectonic evolution of this Palaeohigh and hydrocarbon accumulation there, we carried out a new round of research based on previous study results. The evolution history of this Palaeohigh can be divided into seven episodes: the Late Sinian overall tilting and the youth form development of this Palaeohigh, the Cambrian-Ordovician syndepositional uplifting, the Silurian joint uplifting, the Devonian-Carboniferous uplifting and erosion, the Permian overall subsidence and deposition of regional caprock, the Triassic-Jurassic migration of structural high of the eastern segment of this Palaeohigh, and Cretaceous-Neogene strong deformation of the western segment of this Palaeohigh. The hydrocarbon accumulation in the Sinian-Lower Paleozoic experienced three evolution stages, namely the formation of ancient oil reservoirs in the Silurian-Triassic period, the development of the paleo-gas reservoirs in the Jurassic-Oligocene period, and differential evolution of gas reservoirs since the Miocene era. The Sinian-Lower Paleozoic paleo-reservoirs mainly occur in the Leshan-Ziyang-Gaoshiti-Longnǚsi zone and in the area to its north. The tectonic movement of the western segment of the Palaeohigh was strong, while its eastern segment was relatively stable since the later Himalayan epoch, which is favorable for gas accumulation and preservation. It is believed that the Gaoshiti-Moxi-Longnǚsi structural belt and its northern flank are not only favorable for the development of structural gas reservoirs in the Lower Paleozoic but also for gas reservoirs of karstic-lithologic type on the top of the Cambrian and Ordovician. The later type will be the major exploration target of this area in the future.

  12. Late Quaternary evolution of the Alpine Fault Zone at Paringa, South Westland, New Zealand

    International Nuclear Information System (INIS)

    Recent mapping of the Alpine Fault trace in the Paringa region has revealed the existence of an extensive Haast Schist-derived thrust nappe resting on Western Province basement rock and moraine. Erosion of the nappe by the Paringa River and its tributaries, however, has resulted in eastward propagation of the active fault zone, forming southeast-dipping thrust faults linked by swarms of steeply dipping strike-slip faults. Late Quaternary sediments of the Paringa Formation have been intensely deformed along a newly developed zone of shortening and uplift on the northeast side of Paringa River. Marine, fluviatile, lacustrine, and terrestrial sediments record progressive uplift east of the Alpine Fault. The occurrence of lake deposits rhythmically interbedded with forest horizons may have resulted from damming of the Paringa River behind the zone of rapid uplift. The uplift rate for this region over the last 16 ka has been calculated at 13.7 ±1 mm/yr. After removing the effects of tilting due to localised uplift, a regional uplift rate of 7-8 ±1 mm/yr can be obtained. Estimated average uplift rates for the intervals between 16 ka and the present, and between 11 ka and the present are statistically indistinguishable. (author). 29 refs., 8 figs., 2 tabs

  13. Temporal stability of pollinator preference in an alpine plant community and its implications for the evolution of floral traits.

    Science.gov (United States)

    Gong, Yan-Bing; Huang, Shuang-Quan

    2011-07-01

    A traditional view of diverse floral traits is that they reflect differences in foraging preferences of pollinators. The role of pollinators in the evolution of floral traits has been questioned recently by broad community surveys, especially studies concerning variation in pollinator assemblages and visitation frequency, which suggest a diminished role of pollinators in floral evolution. Here, we investigate the relationships between six categories of floral traits of 29 species and 10 pollinator functional groups in an alpine meadow in the Hengduan Mountains of China, over three consecutive years. Simpson's diversity index was used to estimate the level of pollinator generalization of each plant species by considering both pollinator groups and their relative visitation frequencies. Multivariate analyses indicated that eight of the ten pollinator groups showed constant preferences for at least two floral traits, leading to a relatively stable level of ecological generalization for most floral traits (two out of three categories), despite the fact that the level of generalization of the entire community varied across years. Shape preferences of butterflies, honeybees and beeflies varied such that open flowers exhibited a lower level of ecological generalization in 2007 than closed flowers, in contrast with the other 2 years. These results suggest that temporally stabilized preferences of diverse pollinators may contribute to the evolution of specialized versus generalized floral traits; however, their role may be moderated by variation in community structure, including both the composition and abundance of plants and pollinators. PMID:21253770

  14. Interactions between recent tectonic activity and the evolution of mountain relief of the Inner Cottians Alps (Western Alps): preliminary morphotectonic map.

    Science.gov (United States)

    Bacenetti, Marco; Morelli, Michele; Cadoppi, Paola; Giardino, Marco; Perotti, Luigi; Perrone, Gianluigi

    2014-05-01

    Possible interactions between recent tectonic activity and the evolution of mountain relief have been investigated at the regional (1:50,000) and local (1:5,000) scale in the Germanasca Valley (Cottian Alps, NW-Italy) through an integrated, multidisciplinary approach combining Structural analysis, Quaternary Geology, Geomorphology and Geomatics. The inner edge of the Cottians Alps and the adjacent Po Plain are among the most densely populated portions of the Piemonte Region (NW-Italy). This area corresponds to the junction between the Alpine and Apennine chains and it is affected by a diffuse low- to moderate- seismicity (MlAGEA Orthophoto 2009), aerial stereo couples and DEMs (LiDAR5x5 meters, Regione Piemonte 2009). The morphotectonic lineament analysis was conducted using TerraExplorer® Software Systems, Inc. For the field mapping activities, it was used an application called "SRG2" (Support to Geological / Geomorphological Surveys), an extension for ArcPad (ESRI mobile GIS). Into ArcPad, the SRG2 application adds a toolbar made up of several functions for a useful mapping and classification of geological/geomorphological features. Currently, all data collected were included in a GIS project in order to obtain a preliminary morphotectonic map whose interpretation showed a significant tectonic uplift of the area. Data verified the existence of strong geomorphological anomalies which affected the stream network, the slope morphology and the distribution of Quaternary deposits.Results are particularly important for this sector of the Alps, where "active structures", capable of generating earthquakes of this magnitude, have not been identified so far.

  15. The relationship between tectonic evolution and oil-cracking gas accumulation in late stage for marine superimposed basins

    Science.gov (United States)

    Zheng, Min; Wu, Xiaozhi

    2015-04-01

    The marine superimposed basins are rich in oil-cracking gas resources. Their hydrocarbon accumulation processes of late stage have experienced early paleo-oil reservoir accumulation period and late oil-cracking gas period, which are apparently controlled by tectonic evolution. Studying the relationship between tectonic evolution and oil-cracking gas accumulation of late stage has great significance to guide the exploration of oil-cracking gas reservoirs. Taking the relationship between tectonic evolution and oil-cracking gas accumulation of late stage for the Shunan area in the Sichuan Basin as example, through the analysis on the respons of structural evolution to deposition, the relationship between hydrocarbon generation process of ancient source rocks, initial hydrocarbon accumulation, oil cracking and gas accumulation of late stage was studied. The source rocks of the Cambrian Qiongzhusi Fm in the Shunan area experienced three periods of hydrocarbon generation and two periods of hydrocarbon generation lag. During the large-scale tectonic uplift and thick erosion event in the periods of the Caledonian and the Hercynian, the source rocks of the Qiongzhusi Fm had experienced two times of hydrocarbon generation and two times of hydrocarbon generation lag. The overlying super-thick strata deposited during the Indosinian and Yanshan periods made the source rocks of the Qiongzhusi Fm continuously generate oil and gas. The crude oil in the paleo-reservoir of the Longwangmiao Fm had experienced one time of oil-cracking gas process. After the Indo-Chinese epoch, the burial depth of the Triassic strata was deep enough to promote the crude oil in the paleo-reservoir of the Longwangmiao Fm to be cracked gas. This process continued to the late Yanshan period, providing sufficient gas source. The following five conclusions are obtained: The tectonic and depositional evolution of the marine superimposed basins controlled the development of the basic hydrocarbon geology

  16. Structural characteristics of Pavonis Mons, Mars, and implications for its volcano-tectonic evolution

    Science.gov (United States)

    Gwinner, Klaus; Head, James W.; Wilson, Lionel

    2010-05-01

    Pavonis Mons is the smallest of the three large Tharsis Montes volcanic edifices on Mars. While Viking-based studies have already revealed main structural features of these shields and have provided a framework on their evolution, detailed information on major aspects of their volcano-tectonic structure and evolution is still incomplete. In particular this is the case for the nature of asymmetries that develop along a NE direction, roughly coincident with the crest line of the Tharsis rise, as well as the evolution of the magma reservoir as the shields were built above the ground, and the related consequences for caldera formation and edifice stability. In addition, different morpho-structural features of the Martian shields have been discussed controversially, such as flank "terraces", rillelike channels, and evidence of flank instabilities. We have analyzed recently available high-resolution data, in particular DTMs with up to 50 m grid spacing derived from HRSC data, as well as high-resolution imagery (HRSC, CTX, HIRISE) and regional-scale MOLA DTMs for obtaining new constraints on the volcano-tectonic structure and evolution of Pavonis. We mapped tectonic elements (faults and fractures, wrinkle ridges, collapse pits), main volcanic elements (vent locations, limits of shield, apron and caldera floor units), and elements of flank morphology. Analysis of edifice morphometry is based on slope maps and slope statistics. We were able to identify several major fault systems affecting flanks and base of the edifice. Widespread occurrence of normal faulting from 2-3 km below the summit plateau to the base shows that the middle and lower flanks are characterized by extension. While the summit plateau and uppermost flanks show evidence for compressional deformation, including wrinkle ridges and downslope-convex flank facets interpreted as surface expression of flank thrusts, the system of intersecting flank facets that have been denoted as compressional "terraces" instead

  17. Tectonic evolution of the Anadyr Basin, northeastern Eurasia, and its petroleum resource potential

    Science.gov (United States)

    Antipov, M. P.; Bondarenko, G. E.; Bordovskaya, T. O.; Shipilov, E. V.

    2009-09-01

    The published data on the sedimentation conditions, structure, and tectonic evolution of the Anadyr Basin in the Mesozoic and Cenozoic are reviewed. These data are re-examined in the context of modern tectonic concepts concerning the evolution of the northwestern Circum-Pacific Belt. The re-examination allows us not only to specify the regional geology and tectonic history, but also to forecast of the petroleum resource potential of the sedimentary cover based on a new concept. The sedimentary cover formation in the Anadyr Basin is inseparably linked with the regional tectonic evolution. The considered portion of the Chukchi Peninsula developed in the Late Mesozoic at the junction of the ocean-type South Anyui Basin, the Asian continental margin, and convergent zones of various ages extending along the Asia-Pacific interface. Strike-slip faulting and pulses of extension dominated in the Cenozoic largely in connection with oroclinal bending of structural elements pertaining to northeastern Eurasia and northwestern North America against the background of accretion of terranes along the zone of convergence with the Pacific oceanic plates. Three main stages are recognized in the formation of the sedimentary cover in the Anadyr Basin. (1) The lower portion of the cover was formed in the Late Cretaceous-Early Eocene under conditions of alternating settings of passive and active continental margins. The Cenomanian-lower Eocene transitional sedimentary complex is located largely in the southern Anadyr Basin (Main River and Lagoonal troughs). (2) In the middle Eocene and Oligocene, sedimentation proceeded against the background of extension and rifting in the northern part of the paleobasin and compression in its southern part. The compression was caused by northward migration of the foredeep in front of the accretionary Koryak Orogen. The maximum thickness of the Eocene-Oligocene sedimentary complex is noted mainly in the southern part of the basin and in the Central and

  18. Ice-load induced tectonics controlled tunnel valley evolution - instances from the southwestern Baltic Sea

    Science.gov (United States)

    Al Hseinat, M.; Hübscher, C.

    2014-08-01

    Advancing ice sheets have a strong impact on the earth's topography. For example, they leave behind an erosional unconformity, bulldozer the underlying strata and form tunnel valleys, primarily by subglacial melt-water erosion and secondarily by direct glacial erosion. The conceptual models of the reactivation of faults within the upper crust, due to the ice sheets' load, are also established. However, this phenomenon is also rather under-explored. Here, we propose a causal link between ice-load induced tectonics, the generation of near-vertical faults in the upper crust above an inherited deep-rooted fault and the evolution of tunnel valleys. The Kossau tunnel valley in the southeastern Bay of Kiel has been surveyed by means of high-resolution multi-channel seismic and echosounder data. It strikes almost south to north and can be mapped over a distance of ca 50 km. It is 1200-8000 m wide with a valley of up to 200 m deep. Quaternary deposits fill the valley and cover the adjacent glaciogenic unconformity. A near-vertical fault system with an apparent dip angle of >80°, which reaches from the top Zechstein upwards into the Quaternary, underlies the valley. The fault partially pierces the seafloor and growth is observed within the uppermost Quaternary strata only. Consequently, the fault evolved in the Late Quaternary. The fault is associated with an anticline that is between 700 and 3000 m wide and about 20-40 m high. The fault-anticline assemblage neither resembles any typical extensional, compressional or strike-slip deformation pattern, nor is it related to salt tectonics. Based on the observed position and deformation pattern of the fault-anticline assemblage, we suggest that these structures formed as a consequence of the differential ice-load induced tectonics above an inherited deep-rooted sub-salt fault related to the Glückstadt Graben. Lateral variations in the ice-load during the ice sheet's advance caused differential subsidence, thus rejuvenating the

  19. Tectonic evolution of the Proto-Tehtyan Ocean in Central China

    Science.gov (United States)

    Li, S.; Zhao, S.; Cao, H.; Liu, X.; Xiao, W.; Lai, S.; Zhao, G.; Zhang, G.

    2013-12-01

    Global reconstruction of Early Paleozoic Paleogeography recently got a big progress, however, the detailed Early Paleozoic Paleogeography and tectonic evolution in East Asia is poorly known. As a complex ocean located between Tarim-North China and the Sibamusu/Baoshan blocks, the Proto-Tethyan Ocean was opened from the rifting of the Rodinia supercontinent and mainly closed until the Early Paleozoic. The known studies suggest that there were many continents and micro-continents in the Proto-Tethyan Ocean such as the Central Qilian, Qaidam, Yangtze, Cathaysia, Indochina and Lanping-Simao blocks. Some Early Paleozoic ophiolites and HP-UHP metamorphic rocks developed among these continents/micro-continents. However, some academic debates are still remained on the boundaries of the Proto-Tethys ocean and the nature, relations and assembly processes of these continents/micro-continents to the northern Tarim-North China Continent. These problems are important for unrevealing and reconstructing tectonic settings before the initial assembly of the Supercontinent Pangea. Obviously, the Proto-Tethys tectonic domain is characterized by a complex ocean-continent framework, assembly and dispersal of continents from the rifting of the Supercontinent Rodinia to the assembly of the Supercontinent Pangea. Therefore, this study focuses on summarying and discussing the northern part of the Proto-Tethys tectonic domain based on the field geology, structures, magamatism, sedimentary rocks, geochemistry, geochronology and tomography, in order to reveal three key aspects: 1) identifying the northern boundaries of the Proto-Tethyan Ocean; 2) establishing affinities of continents/micro-continents north of the Proto-Tethyan Ocean and ocean-continent configuration; and 3) clarifying the temporal sequence and styles of micro-continental assembly north of the Proto-Tethysan Ocean. Especially our 3-year detailedly structural study reveals that the Early Paleozoic assembly of small blocks to the

  20. Multikinetic modeling for tectonic evolution of Hefei Basin by apatite fission-track (AFT) analyses

    International Nuclear Information System (INIS)

    Apatite fission-track (AFT) analyses of Jurassic sandstones from Yuantongshan Formation (J2y) at Dazitang area of Feixi County in the central part of Hefei Basin suggested that its fission-track (FT)age is (32.5±2.4)Ma (the average of 22 grains) which is apparently younger than the strata age (176∼168 Ma), their mean confined track length is (12.43±0.18)μm (the average of 126 tracks length), and displays a unimodal distribution. The modeling thermal history can be divided into five stages: 176∼152 Ma before present with the cooling rate of -21.4 degree C per million years, 152∼85 Ma before present with the cooling rate -0.1 degree C per million years, 85∼32 Ma before present with the cooling rate 1.4 degree C per million years, 32∼10 Ma before present with the cooling rate 1.6 degree C per million years, and 10 Ma to present with the cooling rate 5.0 degree C per million years. Five stages are corresponded respectively to the rapid subsidence and heating of sediment, the stable tectonic and thermal evolution, rapid basin uplifting and cooling. The rapid subsidence of sediment (176∼152 Ma) means that Hefei Basin is controlled by compression of Late Dabie Orogeny and subsided rapidly. The stage of stable sedimentary tectonic evolution (152∼85 Ma) shows that Hefei Basin is mainly controlled by dome extension and magmatism of Dabie Orogeny. The cooling stage of (85∼25 Ma) is controlled by the strike-slipping of Tanlu Fault and regional extension. The last stage (since 25 Ma) is characterized by compression, uplift and rapid erosion of Hefei Basin. (authors)

  1. Tectonic, magmatic, and metallogenic evolution of the Late Cretaceous arc in the Carpathian-Balkan orogen

    Science.gov (United States)

    Gallhofer, Daniela; Quadt, Albrecht von; Peytcheva, Irena; Schmid, Stefan M.; Heinrich, Christoph A.

    2015-09-01

    The Apuseni-Banat-Timok-Srednogorie Late Cretaceous magmatic arc in the Carpathian-Balkan orogen formed on the European margin during closure of the Neotethys Ocean. It was subsequently deformed into a complex orocline by continental collisions. The Cu-Au mineralized arc consists of geologically distinct segments: the Apuseni, Banat, Timok, Panagyurishte, and Eastern Srednogorie segments. New U-Pb zircon ages and geochemical whole rock data for the Banat and Apuseni segments are combined with previously published data to reconstruct the original arc geometry and better constrain its tectonic evolution. Trace element and isotopic signatures of the arc magmas indicate a subduction-enriched source in all segments and variable contamination by continental crust. The magmatic arc was active for 25 Myr (~92-67 Ma). Across-arc age trends of progressively younger ages toward the inferred paleo-trench indicate gradual steepening of the subducting slab away from the upper plate European margin. This leads to asthenospheric corner flow in the overriding plate, which is recorded by decreasing 87Sr/86Sr (0.70577 to 0.70373) and increasing 143Nd/144Nd (0.51234 to 0.51264) ratios over time in some segments. The close spatial relationship between arc magmatism, large-scale shear zones, and related strike-slip sedimentary basins in the Timok and Pangyurishte segments indicates mild transtension in these central segments of the restored arc. In contrast, the Eastern Srednogorie segment underwent strong orthogonal intraarc extension. Segmental distribution of tectonic stress may account for the concentration of rich porphyry Cu deposits in the transtensional segments, where lower crustal magma storage and fractionation favored the evolution of volatile-rich magmas.

  2. Analyses on the tectonic thermal evolution and influence factors in the deep-water Qiongdongnan Basin

    Institute of Scientific and Technical Information of China (English)

    WANG Zhenfeng; SHI Xiaobin; YANG Jun; HUANG Baojia; SUN Zhen; WANG Yahui; JIANG Haiyan; YU Chuanhai; YANG Xiaoqiu

    2014-01-01

    To reveal the tectonic thermal evolution and influence factors on the present heat flow distribution, based on 154 heat flow data, the present heat flow distribution features of the main tectonic units are first analyzed in detail, then the tectonic thermal evolution histories of 20 profiles are reestablished crossing the main deep-water sags with a structural, thermal and sedimentary coupled numerical model. On the basis of the present geothermal features, the Qiongdongnan Basin could be divided into three regions: the northern shelf and upper slope region with a heat flow of 50–70 mW/m2, most of the central depression zone of 70–85 mW/m2, and a NE trending high heat flow zone of 85–105 mW/m2 lying in the eastern basin. Numerical modeling shows that during the syn-rift phase, the heat flow increases generally with time, and is higher in basement high area than in its adjacent sags. At the end of the syn-rift phase, the heat flow in the deep-water sags was in a range of 60–85 mW/m2, while in the basement high area, it was in a range of 75–100 mW/m2. During the post-rift phase, the heat flow decreased gradually, and tended to be more uniform in the basement highs and sags. However, an extensive magmatism, which equivalently happened at around 5 Ma, has greatly increased the heat flow values, and the relict heat still contributes about 10–25 mW/m2to the present surface heat flow in the central depression zone and the southern uplift zone. Further analyses suggested that the present high heat flow in the deep-water Qiongdongnan Basin is a combined result of the thermal anomaly in the upper mantle, highly thinning of the lithosphere, and the recent extensive magma-tism. Other secondary factors might have affected the heat flow distribution features in some local regions. These factors include basement and seafloor topography, sediment heat generation, thermal blanketing, local magmatic injecting and hydrothermal activities related to faulting and

  3. Metamorphic and tectonic evolution of Ceuta peninsula (Internal Rif): new interpretation in the framework of arc and back arc evolution

    Science.gov (United States)

    Homonnay, Emmanuelle; Lardeaux, Jean-Marc; Corsini, Michel; Cenki-Tok, Bénédicte; Bosch, Delphine; Munch, Philippe; Romagny, Adrien; Ouazzani-Touhami, Mohamed

    2016-04-01

    In the last twenty years, various geophysical investigations have established that the Western Mediterranean opened in a subduction context as a back arc domain. In the Alboran basin the dip of the subduction plane is eastwards or southeastwards depending of considered models. If the geological records of back-arc opening are well-known, the arc-related tectonic and petrologic evolutions are still poorly documented. In order to decipher these markers, we focalised structural, petrological and thermo-chronological studies on the Ceuta peninsula located in the Rif belt, on the western part of the Gibraltar arc to the North of Morocco. The present-day tectonic pile is constituted by: (1) the upper Ceuta unit, composed of High Pressure and High Temperature metapelites retromorphosed under Amphibolite-facies condition, with Ultra-High Pressure relicts, and pyrigarnite and spinel bearing peridotites boudins at its base, (2) the lower Monte Hacho unit, with orthogneisses metamorphosed under Amphibolite-facies conditions. Structural analysis indicates a polyphase tectonic evolution: (1) an earlier deformation phase only observed in the UHP metapelites and characterized by a steep S1 foliation plane, (2) a main deformation phase associated to a pervasive gently dipping S2 foliation plane bearing a L2 stretching lineation and synschistose folds whose axes are parallel to L2 and (3) a late deformation phase which developed S3 foliation plane and L3 stretching lineation coeval with development of narrow normal ductile shear zones. A zone of increasing deformation, several dozen meters wide, is identified as a major ductile shear zone involving the peridotitic lenses at the base of the metapelites of the Ceuta unit and overlaying this upper unit on top of the orthogneisses of the Monte Hacho lower unit. The attitude of mylonitic foliation and stretching and mineral lineations as well as the numerous shear sense indicators observed in the shear zone are consistent with a

  4. Diagenetic Evolution and Reservoir Quality of Sandstones in the North Alpine Foreland Basin: A Microscale Approach.

    Science.gov (United States)

    Gross, Doris; Grundtner, Marie-Louise; Misch, David; Riedl, Martin; Sachsenhofer, Reinhard F; Scheucher, Lorenz

    2015-10-01

    Siliciclastic reservoir rocks of the North Alpine Foreland Basin were studied focusing on investigations of pore fillings. Conventional oil and gas production requires certain thresholds of porosity and permeability. These parameters are controlled by the size and shape of grains and diagenetic processes like compaction, dissolution, and precipitation of mineral phases. In an attempt to estimate the impact of these factors, conventional microscopy, high resolution scanning electron microscopy, and wavelength dispersive element mapping were applied. Rock types were established accordingly, considering Poro/Perm data. Reservoir properties in shallow marine Cenomanian sandstones are mainly controlled by the degree of diagenetic calcite precipitation, Turonian rocks are characterized by reduced permeability, even for weakly cemented layers, due to higher matrix content as a result of lower depositional energy. Eocene subarkoses tend to be coarse-grained with minor matrix content as a result of their fluvio-deltaic and coastal deposition. Reservoir quality is therefore controlled by diagenetic clay and minor calcite cementation.Although Eocene rocks are often matrix free, occasionally a clay mineral matrix may be present and influence cementation of pores during early diagenesis. Oligo-/Miocene deep marine rocks exhibit excellent quality in cases when early cement is dissolved and not replaced by secondary calcite, mainly bound to the gas-water contact within hydrocarbon reservoirs. PMID:26365327

  5. Alpine endemic spiders shed light on the origin and evolution of subterranean species.

    Science.gov (United States)

    Mammola, Stefano; Isaia, Marco; Arnedo, Miquel A

    2015-01-01

    We designed a comparative study to unravel the phylogeography of two Alpine endemic spiders characterized by a different degree of adaptation to subterranean life: Troglohyphantes vignai (Araneae, Linyphiidae) and Pimoa rupicola (Araneae, Pimoidae), the latter showing minor adaptation to hypogean life. We sampled populations of the model species in caves and other subterranean habitats across their known geographical range in the Western Alps. By combining phylogeographic inferences and Ecological Niche Modeling techniques, we inferred the biogeographic scenario that led to the present day population structure of the two species. According to our divergent time estimates and relative uncertainties, the isolation of T. vignai and P. rupicola from their northern sister groups was tracked back to Middle-Late Miocene. Furthermore, the fingerprint left by Pleistocene glaciations on the population structure revealed by the genetic data, led to the hypothesis that a progressive adaptation to subterranean habitats occurred in T. vignai, followed by strong population isolation. On the other hand, P. rupicola underwent a remarkable genetic bottleneck during the Pleistocene glaciations, that shaped its present population structure. It seems likely that such shallow population structure is both the result of the minor degree of specialization to hypogean life and the higher dispersal ability characterizing this species. The simultaneous study of overlapping spider species showing different levels of adaptation to hypogean life, disclosed a new way to clarify patterns of biological diversification and to understand the effects of past climatic shift on the subterranean biodiversity. PMID:26734503

  6. Polyploid evolution and Pleistocene glacial cycles: A case study from the alpine primrose Primula marginata (Primulaceae

    Directory of Open Access Journals (Sweden)

    Casazza Gabriele

    2012-04-01

    Full Text Available Abstract Background Recent studies highlighted the role of Pleistocene climatic cycles in polyploid speciation and of southern Alpine refugia as reservoirs of diversity during glacial maxima. The polyploid Primula marginata, endemic to the southwestern Alps, includes both hexaploid and dodecaploid cytotypes that show no ecological or morphological differences. We used flow cytometry to determine variation and geographic distribution of cytotypes within and between populations and analyses of chloroplast (cp and nuclear ribosomal (nr DNA sequences from the Internal Transcribed Spacer (ITS region to infer the evolutionary history of the two cytotypes and the auto- vs. allopolyploid origin of dodecaploid populations. Results We did not detect any intermediate cytotypes or variation of ploidy levels within populations. Hexaploids occur in the western and dodecaploids in the eastern part of the distributional range, respectively. The cpDNA and nrDNA topologies are in conflict, for the former supports shared ancestry between P. marginata and P. latifolia, while the latter implies common origins between at least some ITS clones of P. marginata and P. allionii. Conclusions Our results suggest an initial episode of chloroplast capture involving ancestral lineages of P. latifolia and P. marginata, followed by polyploidization between P. marginata-like and P. allionii-like lineages in a southern refugium of the Maritime Alps. The higher proportion of ITS polymorphisms in dodecaploid than in hexaploid accessions of P. marginata and higher total nucleotide diversity of ITS clones in dodecaploid vs. hexaploid individuals sequences are congruent with the allopolyploid hypothesis of dodecaploid origin.

  7. Drainage response to active tectonics and evolution of tectonic geomorphology across the Himalayan Frontal Thrust, Kumaun Himalaya

    Science.gov (United States)

    Luirei, Khayingshing; Bhakuni, Surendra S.; Kothyari, Girish Ch.

    2015-06-01

    We present the results of integrated studies of geomorphic indices of drainage networks and landforms developed across the mountain front along the Himalayan Frontal Thrust (HFT) between the Dabka and Baur rivers, Kumaun Himalaya. The HFT is a morphogenic structure in nature, creating a 100-m-high E-W trending escarpment that extends ~ 21 km. Geomorphological evidence indicates ~ 10.5 km westward migration of the Dabka River and ~ 5.2 km eastward migration of the Baur River. These migrations are a result of uplift of the hanging wall along the HFT. The HFT is offset by a transverse fault, which suggests that the latter postdates the reactivation of the HFT between 500 and 100 ka. Presence of different levels of strath terraces along the mountain front suggests the active nature of the HFT. To assess the relative tectonic activity, morphometric indices such as stream-gradient (SL) index, mountain front sinuosity (Smf) index, and ratio of valley floor width to valley height (Vf) have been analyzed. Results of the former two are consistent with the tectonic landforms developed in thrust zones. Paleochannels of the Dabka and Baur rivers are characterized by high Vf values while other valleys show low Vf values. Quaternary alluvial sediments have been deformed along the Pawalgarth Thrust, a splay of the HFT. Deformation has resulted in the formation of the Pawalgarh Anticline, a thrust-related asymmetric fold.

  8. Molecular bases for parallel evolution of translucent bracts in an alpine "glasshouse" plant Rheum alexandrae (Polygonaceae)

    Czech Academy of Sciences Publication Activity Database

    Liu, B. B.; Opgenoorth, L.; Miehe, G.; Zhang, D.-Y.; Wan, D.-S.; Zhao, C.-M.; Jia, Dong-Rui; Liu, J.-Q.

    2013-01-01

    Roč. 51, č. 2 (2013), s. 134-141. ISSN 1674-4918 Institutional support: RVO:67985939 Keywords : cDNA-AFLPs * parallel evolution * adaptations, mutations, diversity Subject RIV: EF - Botanics Impact factor: 1.648, year: 2013

  9. Genome evolution in alpine oat-like grasses through homoploid hybridization and polyploidy

    Science.gov (United States)

    Winterfeld, Grit; Wölk, Alexandra; Röser, Martin

    2016-01-01

    Hybridization and polyploidization can radically impact genome organization from sequence level to chromosome structure. As a result, often in response to environmental change and species isolation, the development of novel traits can arise and will tend to result in the formation of homoploid or polyploid hybrid species. In this study we focus on evidence of hybridization and polyploidization by ascertaining the species parentage of the endemic alpine Helictotrichon parlatorei group. This group comprises five taxa; the diploids H. parlatorei, Helictotrichon setaceum subsp. setaceum and subsp. petzense, their putative hybrid Helictotrichon ×krischae and the hexaploid Helictotrichon sempervirens. For molecular analyses, cloned nuclear Topoisomerase VI genes of H. sempervirens and H. ×krischae were sequenced and compared with sequences of the diploids to estimate the evolutionary history in this group. In addition, detailed chromosome studies were carried out including fluorescence in situ hybridization (FISH) with 5S and 45S ribosomal and satellite DNA probes, and fluorochrome staining with chromomycin and DAPI. Two distinct types of Topoisomerase VI sequences were identified. One of them (SET) occurs in both subspecies of H. setaceum, the other (PAR) in H. parlatorei. Both types were found in H. ×krischae and H. sempervirens. Karyotypes of H. parlatorei and H. setaceum could be distinguished by chromosomes with a clearly differentiated banding pattern of ribosomal DNAs. Both patterns occurred in the hybrid H. ×krischae. Hexaploid H. sempervirens shares karyotype features with diploid H. parlatorei, but lacks the expected chromosome characteristics of H. setaceum, possibly an example of beginning diploidization after polyploidization. The geographic origin of the putative parental species and their hybrids and the possible biogeographical spread through the Alps are discussed. PMID:27255513

  10. Genome evolution in alpine oat-like grasses through homoploid hybridization and polyploidy.

    Science.gov (United States)

    Winterfeld, Grit; Wölk, Alexandra; Röser, Martin

    2016-01-01

    Hybridization and polyploidization can radically impact genome organization from sequence level to chromosome structure. As a result, often in response to environmental change and species isolation, the development of novel traits can arise and will tend to result in the formation of homoploid or polyploid hybrid species. In this study we focus on evidence of hybridization and polyploidization by ascertaining the species parentage of the endemic alpine Helictotrichon parlatorei group. This group comprises five taxa; the diploids H. parlatorei, Helictotrichon setaceum subsp. setaceum and subsp. petzense, their putative hybrid Helictotrichon ×krischae and the hexaploid Helictotrichon sempervirens. For molecular analyses, cloned nuclear Topoisomerase VI genes of H. sempervirens and H. ×krischae were sequenced and compared with sequences of the diploids to estimate the evolutionary history in this group. In addition, detailed chromosome studies were carried out including fluorescence in situ hybridization (FISH) with 5S and 45S ribosomal and satellite DNA probes, and fluorochrome staining with chromomycin and DAPI. Two distinct types of Topoisomerase VI sequences were identified. One of them (SET) occurs in both subspecies of H. setaceum, the other (PAR) in H. parlatorei. Both types were found in H. ×krischae and H. sempervirens Karyotypes of H. parlatorei and H. setaceum could be distinguished by chromosomes with a clearly differentiated banding pattern of ribosomal DNAs. Both patterns occurred in the hybrid H. ×krischae Hexaploid H. sempervirens shares karyotype features with diploid H. parlatorei, but lacks the expected chromosome characteristics of H. setaceum, possibly an example of beginning diploidization after polyploidization. The geographic origin of the putative parental species and their hybrids and the possible biogeographical spread through the Alps are discussed. PMID:27255513

  11. The Cretaceous Songliao Basin: Volcanogenic Succession,Sedimentary Sequence and Tectonic Evolution, NE China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Songliao basin (SB) is a superposed basin with two different kinds of basin fills. The lower one is characterized by a fault-bounded volcanogenic succession comprising of intercalated volcanic, pyroclastic and epiclastic rocks. The volcanic rocks, dating from 110 Ma to 130 Ma, are of geochemically active continental margin type. Fast northward migration of the SB block occurred during the major episodes of the volcanism inferred from their paleomagnetic information. The upper one of the basin fill is dominated by non-marine sag-style sedimentary sequence of siliciclastics and minor carbonates. The basin center shifted westwards from the early to late Cretaceous revealed by the GGT seismic velocity structure suggesting dynamic change in the basin evolution. Thus, a superposed basin model is proposed. Evolution of the SB involves three periods including (1) Alptian and preAptian: a retroarc basin and range system of Andes type related to Mongolia-Okhotsk collisional belt (MOCB); (2) Albian to Companian: a sag-like strike-slip basin under transtension related to oblique subduction of the Pacific plate along the eastern margin of the Eurasian plate; (3) since Maastrichtian:a tectonic inverse basin under compression related to normal subduction of the Pacific plate under the Eurasian plate, characterized by overthrust, westward migration of the depocenter and eastward uplifting of the basin margin.

  12. Mesozoic Tertiary tectonic evolution of Albania in its regional Eastern Mediterranean context

    Science.gov (United States)

    Robertson, Alastair; Shallo, Minella

    2000-01-01

    Research carried out since the opening of Albania to the 'western' geological community in the 1990s allows the geology and tectonics of this small Balkan country to be integrated into an overall interpretation of Neotethys in the Eastern Mediterranean region, specifically Greece and the former Yugoslavia region. Albanian geology is most famous for the occurrence of contrasting ophiolites of Jurassic age. The country is sub-divided into three main geotectonic units. Those in the west (i.e. Sazani, Ionian, Kruja, Krasta-Cukali and the Albanian Alps) relate to the western margin of Apulia, effectively part of North Africa from Early Mesozoic time onwards. In the east is the Korabi zone, interpreted as a microcontinent located further northeast within Neotethys. Between the two is the Mirdita zone, dominated by two contrasting Jurassic ophiolites: the 'Western-type' ophiolite and the 'Eastern-type' ophiolite. Taking account of evidence from Greece and former Yugoslavia, the following tectonic evolution is proposed. From Early Mesozoic time onwards, Neotethys in Albania existed as a northward continuation of the Pindos oceanic basin in Greece (Pindos-Mirdita ocean). A Korabi microcontinent was rifted off Apulia in the Early-Mid Triassic, followed by passive margin subsidence until late Middle Jurassic time. A rifted, slow-spreading, MOR-type ophiolite formed within the western Pindos-Mirdita oceanic basin in Late Triassic?-early Late Jurassic time (using present co-ordinates). The Shkoder-Peje (Scutari-Peć) lineament in the north of Albania is interpreted as an important transform fault zone that influenced the regional tectonic evolution during the entire Mesozoic-Early Tertiary rift/drift/emplacement history of the Pindos-Mirdita ocean. Taking account of evidence from the Greek and former Yugoslavia ophiolites, the easterly Albanian ophiolites formed within the Pindos-Mirdita ocean above a westward-dipping intra-oceanic subduction zone in the early Late Jurassic

  13. Thermochronology and tectonics of the Leeward Antilles: Evolution of the southern Caribbean Plate boundary zone

    Science.gov (United States)

    van der Lelij, Roelant; Spikings, Richard A.; Kerr, Andrew C.; Kounov, Alexandre; Cosca, Michael; Chew, David; Villagomez, Diego

    2010-01-01

    Tectonic reconstructions of the Caribbean Plate are severely hampered by a paucity of geochronologic and exhumation constraints from anastomosed basement blocks along its southern margin. New U/Pb, 40Ar/39Ar, apatite fission track, and apatite (U-Th)/He data constrain quantitative thermal and exhumation histories, which have been used to propose a model for the tectonic evolution of the emergent parts of the Bonaire Block and the southern Caribbean Plate boundary zone. An east facing arc system intruded through an oceanic plateau during ~90 to ~87 Ma and crops out on Aruba. Subsequent structural displacements resulted in >80°C of cooling on Aruba during 70–60 Ma. In contrast, exhumation of the island arc sequence exposed on Bonaire occurred at 85–80 Ma and 55–45 Ma. Santonian exhumation on Bonaire occurred immediately subsequent to burial metamorphism and may have been driven by the collision of a west facing island arc with the Caribbean Plate. Island arc rocks intruded oceanic plateau rocks on Gran Roque at ~65 Ma and exhumed rapidly at 55–45 Ma. We attribute Maastrichtian-Danian exhumation on Aruba and early Eocene exhumation on Bonaire and Gran Roque to sequential diachronous accretion of their basement units to the South American Plate. Widespread unconformities indicate late Eocene subaerial exposure. Late Oligocene–early Miocene dextral transtension within the Bonaire Block drove subsidence and burial of crystalline basement rocks of the Leeward Antilles to ≤1 km. Late Miocene–recent transpression caused inversion and ≤1 km of exhumation, possibly as a result of the northward escape of the Maracaibo Block.

  14. The late Mesozoic-Cenozoic tectonic evolution of the South China Sea: A petrologic perspective

    Science.gov (United States)

    Yan, Quanshu; Shi, Xuefa; Castillo, Paterno R.

    2014-05-01

    This paper presents a review of available petrological, geochonological and geochemical data for late Mesozoic to Recent igneous rocks in the South China Sea (SCS) and adjacent regions and a discussion of their petrogeneses and tectonic implications. The integration of these data with available geophysical and other geologic information led to the following tectono-magmatic model for the evolution of the SCS region. The geochemical characteristics of late Mesozoic granitic rocks in the Pearl River Mouth Basin (PRMB), micro-blocks in the SCS, the offshore continental shelf and Dalat zone in southern Vietnam, and the Schwaner Mountains in West Kalimantan, Borneo indicate that these are mainly I-type granites plus a small amount of S-type granites in the PRMB. These granitoids were formed in a continental arc tectonic setting, consistent with the ideas proposed by Holloway (1982) and Taylor and Hayes (1980, 1983), that there existed an Andean-type volcanic arc during later Mesozoic era in the SCS region. The geochonological and geochemical characteristics of the volcanics indicate an early period of bimodal volcanism (60-43 Ma or 32 Ma) at the northern margin of the SCS, followed by a period of relatively passive style volcanism during Cenozoic seafloor spreading (37 or 30-16 Ma) within the SCS, and post-spreading volcanism (tholeiitic series at 17-8 Ma, followed by alkali series from 8 Ma to present) in the entire SCS region. The geodynamic setting of the earlier volcanics was an extensional regime, which resulted from the collision between India and Eurasian plates since the earliest Cenozoic, and that of the post-spreading volcanics may be related to mantle plume magmatism in Hainan Island. In addition, the nascent Hainan plume may have played a significant role in the extension along the northern margin and seafloor spreading in the SCS.

  15. Tectonic Evolution of the Junggar Foreland Basin in the Late Carboniferous-Permian

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A comprehensive study has been carried out to subdivide andcorrelate the Upper Carboniferous and Permian sedimentary successions in the Junggar basin based on outcrops and drilling and geophysical data. The study results, combined with geological analyses of the basin's periphery and the basement, as well as studies of the sedimentary rocks within the basin, the unconformities, tectonic geometry, kinematics and geodynamics, lead to the conclusion that the Junggar basin was characterized by the development of foreland basin systems during the Late Carboniferous and Per mian, During that period, three foreland basin systems were developed: (1) the northwest foreland basin system, which trended nearly north-south from Mahu to the Chepaizi Palaeo-mountain during its early stage of development and thus it was also referred to as the west foreland basin system; (2) the Karamaili foreland basin system in the east and (3) the Northern Tianshan foreland basin system in the south. These systems are different in size, development stage and time of formation. The first two are developed earlier than the third, but they are smaller in size. All the structures in the Junggar basin have resulted from the integration and superposition of structural elements in the above three systems. In general, the development of the Junggar basin can be divided into four stages. Stage I was marked by the creation and evolution of the marginal western foreland and the peripheral Karamaili foreland basin systems during the Late Carboniferous-early Early Permian (C3-Pja). Stage Ⅱ was characterized by the development of complicated foreland basin systems during the mid dle-late Early Permian (Pjb-Pf) when the three foreland basin systems took their shapes. Stage Ⅲ was the integration stage of peripheral foreland basin systems during the Middle Permian (P2) in which steady and slow tectonic subsidence prevailed. Stage Ⅳ coincided with the shrinking of foreland basin development during the Late

  16. The climatic, biotic and tectonic evolution of the Paleogene Renova formation of southwestern Montana

    Science.gov (United States)

    Lielke, Kevin John

    The Renova Formation of southwestern Montana contains an important record of Paleogene floral, faunal, climate and tectonic change in the northern Rocky Mountains. The period between the end of the early Eocene and the early Oligocene (˜49--32 Ma) was a time of rapid and far-reaching climate change. This period saw the end of global greenhouse climate and the establishment of icehouse conditions across the Earth. These changes led to profound alterations in both marine and terrestrial ecosystems. This study examines the late Eocene/early Oligocene history of the northern Rocky Mountains by means of an integrated study of the sedimentology, tectonics and fossil content of the Renova Formation. The first part of this study examines plant fossils found in the Renova Formation in order to examine changes in the composition of the vegetation across the late Eocene/ early Oligocene (E/O) boundary. Plant remains are an effective proxy for climate and are used to estimate multiple climatic parameters across the E/O boundary. The second part of this study examines the paleotopography and paleodrainage patterns of the basins which accumulated the Renova sediments. This is accomplished by a combination of sedimentary facies and detrital zircon analysis. The third part of this study examines the tectonic underpinnings of Paleogene southwestern Montana through a combination of geologic field work and geodynamic modeling. The results of this study indicate that a seasonal summer dry climate became established in the northern Rocky Mountains by early Oligocene time. This is indicated by the elimination of subtropical plant species, the establishment of dry-adapted species and by paleoclimate parameters calculated from leaf physiognomy. Geodynamic calculations and field data indicate that the Renova Formation was deposited in a series of sub-basins separated by relict paleotopography and inverted topography formed by contemporary lava flows. Normal faulting was not active until

  17. Tectonic metallogenesis of uranium and its time-space evolution in uranium metallogenic provinces of south China

    International Nuclear Information System (INIS)

    The paper discusses grade-sequences and clusters of linear structures and ore-concentrating structures controlling uranium mineralization. Time-space evolutional model of uranium in metalogenic provinces is suggested. The time-bound interval of uranium commercial concentration is about 35 Ma. It is just in the transitional period between two tectonic episodes of Yanshanian and Himalayan tectonic cycles respectively, and it is consistent with maximum mobility period and residual mobility period of the Diwa stage. Economic concentration of uranium took place in Mesozoic period which was a relatively stable period for the continental crust changing from the stage of compression into tension under the action of plate tectonics. With the strong tectonic reactivation in Mesozoic and Cenozoic period, uranium was further increased in the tectonic-geochemical environments of uranium-rich strata (body). Under the mutual action of various uranium sources, fluid sources and heat sources, uranium in the particular tectono-geochemical barriers was enriched and uranium deposits were formed

  18. Tectonic evolution of the continental crust of South America and its importance in the characterization of uraniferous provinces

    International Nuclear Information System (INIS)

    The tectonic evolution of the South American Continent and its relationship with uranium mineralization is discussed. During the Phanerozoic at least three phases are identified as related to the Andean chain, namely, in the lower Palaeozoic, in the upper Palaeozoic and in the Meso-Cenozoic. Recent systematic age dating of the Precambrian indicates the period of 450-700 million years (m.y.) (Brazilian Cycle) as one of the most important tectonic events in South America. Another age-dating cluster corresponds to the 1700-2100 m.y. interval (Transamazonic Cycle). An even older event within the Archean is identified with datings older than 2600 m.y. in Venezuela (Estado Bolivar), Surinam and Brazil (Bahia, Santa Catarina, Goias). All the Brazilian uranium deposits related to the Brazilian platform, such as Amorinopolis, are located on the eastern border of the platform where the Brazilian tectonic cycle is dominant. The uranium source rocks are of alkaline granitic nature. Other deposits (Itataia, Campos Belos) are associated with polycyclic rocks belonging to the basement of the Brazilian Cycle but were affected by the 450-700 m.y. tectonic event; these amphibolitic facies rocks show alkaline metamorphism and magmatization processes which indicate large geochemical mobility during which important uranium mobilization has taken place. Finally, the Pocos de Caldas deposit is excellent evidence of the important relationship of tectonic reactivations and uranium enrichments within the Brazilian platform. (author)

  19. Meso-Cenozoic tectonic evolution and uranium potential evaluations of basins in Beishan-Gansu corridor region

    International Nuclear Information System (INIS)

    Beishan-Gansu Corridor region is located at the intersection of the plates of Tarim, North China, Kazakhstan, Siberia and Qaidam. During the Meso-Cenozoic, the region experienced movements of Indo-sinian, Yanshanian, Sichuanian, North China, Himalayan and Neotectonic, and over 20 medium-small size superimposed continental basins were formed. On the basis of analyzing the tectonic stress field, sediment-filling and structure-deformation; the general trending of tectonic evolution in the Meso-Cenozoic is summarized as three-time compressional uplifting and two-time extensional down-faulting. The different evolution of basins under the above mentioned setting can be divided into six stages according to characteristics of filled sediment. The sand bodies developed in down-faulted basins are favorable for uranium ore-formation as they are formed under humid paleoclimates, and rich in reducing matter. Therefore, the Lower-Middle Jurassic is selected as the main target horizon for sandstone-hosted uranium deposit, and the Lower Cretaceous as the minor one. Although the tectonic reactivation of the target horizon after its deposition was generally strong, the slopes formed in some basins could be favorable for the infiltration of uranium-and oxygen-bearing groundwater into sand bodies and form uranium deposits. According to the favorable sand bodies and tectonic reactivation, the northern parts of Chaoshui and Bayingobi basins are regarded as potential regions which are worthy of further exploration. (authors)

  20. Periodic Vesicle Formation in Tectonic Fault Zones—an Ideal Scenario for Molecular Evolution

    Science.gov (United States)

    Mayer, Christian; Schreiber, Ulrich; Dávila, María J.

    2015-06-01

    Tectonic fault systems in the continental crust offer huge networks of interconnected channels and cavities. Filled mainly with water and carbon dioxide (CO2), containing a wide variety of hydrothermal chemistry and numerous catalytic surfaces, they may offer ideal reaction conditions for prebiotic chemistry. In these systems, an accumulation zone for organic compounds will develop at a depth of approximately 1 km where CO2 turns sub-critical and dissolved components precipitate. At this point, periodic pressure changes caused for example by tidal influences or geyser activity may generate a cyclic process involving repeated phase transitions of carbon dioxide. In the presence of amphiphilic compounds, this will necessarily lead to the transient formation of coated water droplets in the gas phase and corresponding vesicular structures in the aqueous environment. During this process, the concentration of organic components inside the droplets and vesicles would be drastically increased, allowing for favorable reaction conditions and, in case of the vesicles generated, large trans-membrane concentration gradients. Altogether, the process of periodic formation and destruction of vesicles could offer a perfect environment for molecular evolution in small compartments and for the generation of protocells. The basic process of vesicle formation is reproduced experimentally with a lipid in a water/CO2 system.

  1. Study on dynamics of tectonic evolution in the Fushun Basin, Northeast China

    Institute of Scientific and Technical Information of China (English)

    WU; Chonglong(吴冲龙); WANG; Xinqing(汪新庆); LIU; Gang(刘刚); LI; Shaohu(李绍虎); MAO; Xiaoping(毛小平); LI; Xing(李星)

    2002-01-01

    The updated study shows that the taphrogenesis of basement of the Fushun Basin is not a kind of instantaneous process. It intensified gradually and went to extreme in the sedimentary stage of the Guchengzi formation, and then, it weakened rapidly and stopped soon afterwards; the depression did not take place after the taphrogenesis. On the contrary, it almost happened simultaneously with the taphrogenesis. The depression went at a high speed from the beginning of the sedimentary period of the Xilutian formation, and then weakened gradually in the sedimentary period of the Gengjiajie formation. The evolution course of the synsedimentary structure of the Fushun Basin can be summarized as the following six stages: slow taphrogenesis and high speed depression to accelerated taphrogenesis and high speed depression to high speed taphrogenesis and high speed depression to retarded taphrogenesis and high speed depression to gradual halt of taphrogenesis and reduced depression to slow depression and gradual halt of depression. The tectonic evolution resulted in the formation of the "lower taphrogenesis and upper depression" structure. The formation of the binary structure might be due to the suspension of taphrogenesis and the change of the regional structure stress field, but the depression kept going. The result of calculation combining the analysis of the synsedimentary structural frame, the back-stripping method of the subsidence history of the basin basement and the simulation of thermo-settlement history indicates that the great sedimentary space required by the "upper depression part" consists of two parts, namely, 40% from compaction of sediments and 60% from slow depression of the basin basement during a long period of time. Gradual halt of the depression in the Fushun Basin may be attributed to the reversal of the lithosphere hot-recession and gravity isostasy adjustment which may be the result of new hot-events in the depths and accompanied invasion of extremely

  2. Tectonics and sedimentary evolution of the Sandino forearc basin off Nicaragua, Central America

    Science.gov (United States)

    Costa Pisani, P.; Silver, E.; McIntosh, K.; Ahmed, I.; Ranero, C. R.; Taylor, B.

    2003-04-01

    The Sandino basin is the Nicaragua sector of the Central American forearc, where the Cocos plate subducts beneath the Middle America trench. Recently, Ranero et al. have interpreted a seismic section across the margin and proposed a history of formation of the forearc which is constrained by industry drilling in the basin. They suggested a late Cretaceous to Paleocene accretion event, followed by later subduction erosion processes. The margin wedge consists of the ophiolitic Nicoya complex. The seismic units, unconformities and tectonic features record a rich history of both local and regional vertical movements occurring since the Middle Eocene, which are linked to the evolution of the Pacific convergent margin. During June, 2000, 2800 kms of multichannel seismic reflection data were collected on the R/V Ewing off Nicaragua. Analysis of the 240 channels dataset indicates rapid changes along strike in the Sandino basin. The basin is relatively thin in the southern part, thinning quite rapidly southward against the Nicoya complex of the Santa Elena peninsula of Costa Rica. The forearc sediments thickness approaches and locally exceeds 10 kms in the central and northern parts of the Sandino basin. The oldest units (Upper Cretaceous-Middle Eocene) are very thick off northern Nicaragua, with relatively thin middle to late Cenozoic deposits. However, off central Nicaragua the latter units (Middle-Upper Miocene) attain great thicknesses and the older units appear to thin. This pattern suggests a history of successive deepening of the basin from north to south, after the convergent system evolved from accretion to subduction erosion processes. Present efforts are devoted to quantifying this change in development and using it to understand the dynamics of forearc basin evolution offshore of Central America.

  3. Tectonic evolution of the Brusque Group, Dom Feliciano belt, Santa Catarina, Southern Brazil

    Science.gov (United States)

    Basei, M. A. S.; Campos Neto, M. C.; Castro, N. A.; Nutman, A. P.; Wemmer, K.; Yamamoto, M. T.; Hueck, M.; Osako, L.; Siga, O.; Passarelli, C. R.

    2011-12-01

    The Dom Feliciano Belt constitutes the main geotectonic unit of the southeastern portion of Brazil and Uruguay. It was formed by the end of the Neoproterozoic as a result of the interaction among the Rio de La Plata, Paranapanema, Congo and Kalahari cratons during the formation of Western Gondwana. The Brusque Group represents the supracrustal units of the Dom Feliciano Belt that occur in its northernmost part, which ends in the Brazilian coast and probable continuity in the Kaoko Belt in southwestern Africa. It is possible to constrain the evolution of the Brusque Group paleobasin to the Neoproterozoic, with the rift phase starting in the Tonian (940-840 Ma) and the main sedimentation occurring until 640 Ma, as indicated by the ages of the acid volcanic rocks intercalated with the metasedimentary sequence. The supracrustal rocks can be grouped in three main units lithostratigraphically organized from the oldest to the youngest: Rio Oliveira Formation (rift phase, predominating metavolcanic units), Botuverá Formation (metasedimentary) and Rio da Areia Formation (metavolcano-carbonatic). Between 640 and 600 Ma several metamorphism and deformation phases affected the Brusque Group. Around 600 ± 10 Ma the three granitic suites (São João Batista, Valsungana and Nova Trento) were emplaced within regional metamorphites, producing post-foliation S2 metamorphic aureoles. S2 represents the main foliation observed in the metavolcanosedimentary rocks that constitute the Brusque Group. The tectonic model for the evolution of Brusque Group can be better achieved only when the geochemical, isotopic and geochronologic information available for the Dom Feliciano Belt in Santa Catarina, is considered as a whole. Therefore it is here suggested that the Brusque Group initially evolved in an independent peri-cratonic basin setting separated from the Florianópolis - Pelotas-Aiguá magmatic arc by the Adamastor ocean, having been juxtaposed to it only around 600 Ma, when Brusque

  4. Teaching about the Early Earth: Evolution of Tectonics, Life, and the Early Atmosphere

    Science.gov (United States)

    Mogk, D. W.; Manduca, C. A.; Kirk, K.; Williams, M. L.

    2007-12-01

    The early history of the Earth is the subject of some of the most exciting and innovative research in the geosciences, drawing evidence from virtually all fields of geoscience and using a variety of approaches that include field, analytical, experimental, and modeling studies. At the same time, the early Earth presents unique opportunities and challenges in geoscience education: how can we best teach "uncertain science" where the evidence is either incomplete or ambiguous? Teaching about early Earth provides a great opportunity to help students understand the nature of scientific evidence, testing, and understanding. To explore the intersection of research and teaching about this enigmatic period of Earth history, a national workshop was convened for experts in early Earth research and undergraduate geoscience education. The workshop was held in April, 2007 at the University of Massachusetts at Amherst as part of the On the Cutting Edge faculty professional development program. The workshop was organized around three scientific themes: evolution of global tectonics, life, and the early atmosphere. The "big scientific questions" at the forefront of current research about the early Earth were explored by keynote speakers and follow-up discussion groups: How did plate tectonics as we know it today evolve? Were there plates in the Hadean Eon? Was the early Earth molten? How rapidly did it cool? When and how did the atmosphere and hydrosphere evolve? How did life originate and evolve? How did all these components interact at the beginning of Earth's history and evolve toward the Earth system we know today? Similar "big questions" in geoscience education were addressed: how to best teach about "deep time;" how to help students make appropriate inferences when geologic evidence is incomplete; how to engage systems thinking and integrate multiple lines of evidence, across many scales of observation (temporal and spatial), and among many disciplines. Workshop participants

  5. Tectonic interpretation of an inverse gradient of zircon fission-track ages with respect to altitude: Alpine thermal history of the Gran Paradiso basement

    International Nuclear Information System (INIS)

    Extensive sampling along vertical and north-south cross-sections in the Gran Paradiso basement (internal crystalline massif, Western Alps) reveals an inverse gradient of zircon fission-track ages with respect to altitude, which is explained by an ''inverted metamorphism'' during Eocene time. Subsequent to the obduction of the Schistes Lustres nappe (high pressure Eoalpine phase), the Gran Paradiso massif cooled down 90-80 Myrs ago. The Austro-Alpine nappe of Monte Emilius - Dent Blanche overthrust the Gran Paradiso massif 38-40 Myrs ago, inducing in its basement an inverted metamorphism or, more precisely, a ''nappe emplacement metamorphism'' (greenschist facies). The last cooling below 1000C occurred as early as 35-40 Myrs ago in the southern Gran Paradiso massif; in the northern part, this last cooling occurred 20 Myrs ago, accompanied by an important uplift phase (2 mm/year). (orig.)

  6. Determination of the tectonic evolution from fractures, faults, and calcite twins on the southwestern margin of the Indochina Block

    Science.gov (United States)

    Arboit, Francesco; Amrouch, Khalid; Collins, Alan S.; King, Rosalind; Morley, Christopher

    2015-08-01

    In polyphase tectonic zones, integrating a study of fault and fracture with calcite twin analysis can determine the evolving paleostress magnitudes and principle stress directions that affected the area. This paper presents the results of the analyses of fractures, striated faults, and calcite twins collected within the Khao Khwang Fold-Thrust Belt in central Thailand (SE Asia). Here we attempt to reconstruct the orientation of the principal stresses that developed during the tectonic evolution of this highly deformed, polyphase orogen. Tectonic data were collected in the Permian carbonates of the Khao Khad Formation of the Saraburi Group, and five successive tectonic stages are determined that are interpreted to have developed before, during, and after, the Triassic Indosinian Orogeny. The first three stages predate the main deformation event: the first stage is interpreted as a pre-Indosinian N-S extensional stage, the second stage described a N-S strike-slip and compressional regime, largely perpendicular to the fold axes of the main structures, while the third stage is associated with an E-W compressional strike-slip phase. A further two stages took place after, or during, the main folding event and correspond to N-S compression and to an E-W composite strike-slip/contractional stage, the latter which is interpreted to represent Cenozoic deformation related to the India-Asia collision.

  7. Evolution characteristics of Quaternary tectonic stress field in the north and east margin of Qinghai-Xizang plateau

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    By inversion of fault slip data for Quaternary tectonic stress field and the analysis of crustal deformation after late Teriary, we explained the evolution of crustal dynamic about the north and east margin of Qinghai-Xizang (Tibet) plateau since Miocene. From middle or late Miocene to early Pleistocene, the tectonic stress field was featured by a maximum principal compression which was coming from the collision of India Plate perpendicular to the boundary of the plateau, and was basically of reverse faulting type. Since the late period of early Pleistocene, India Plate continued to push northward and the compressional deformation of the plateau interior increased continuously, meanwhile, NW-SE extension appeared on the east side of the plateau. This formed a favorable condition for the interior block of the plateau to slide towards east and southeast, causing the faults surrounding the plateau to change from thrust to strike-slip. The contemporary tectonic stress field was formed from the late period of early Pleistocene and continued to present. The direction of maximum principal compressional stress rotated clockwise with respect to the previous tectonic stress field, the stress field was mainly of strike-slip type.

  8. The Alegre Lineament and its role over the tectonic evolution of the Campos Basin and adjacent continental margin, Southeastern Brazil

    Science.gov (United States)

    Calegari, Salomão Silva; Neves, Mirna Aparecida; Guadagnin, Felipe; França, George Sand; Vincentelli, Maria Gabriela Castillo

    2016-08-01

    The structural framework and tectonic evolution of the sedimentary basins along the eastern margin of the South American continent are closely associated with the tectonic framework and crustal heterogeneities inherited from the Precambrian basement. However, the role of NW-SE and NNW-SSE structures observed at the outcropping basement in Southeastern Brazil and its impact over the development of those basins have not been closely investigated. In the continental region adjacent to the Campos Basin, we described a geological feature with NNW-SSE orientation, named in this paper as the Alegre Fracture Zone (AFZ), which is observed in the onshore basement and can be projected to the offshore basin. The main goal of this work was to study this structural lineament and its influence on the tectonic evolution of the central portion of the Campos Basin and adjacent mainland. The onshore area was investigated through remote sensing data joint with field observations, and the offshore area was studied through the interpretation of 2-D seismic data calibrated by geophysical well logs. We concluded that the AFZ occurs in both onshore and offshore as a brittle deformation zone formed by multiple sets of fractures that originated in the Cambrian and were reactivated mainly as normal faults during the rift phase and in the Cenozoic. In the Campos Basin, the AFZ delimitates the western side of the Corvina-Parati Low, composing a complex fault system with the NE-SW faults and the NW-SE transfer faults.

  9. The role of the Anaxagoras Mountain in the Miocene to Recent tectonic evolution of the eastern Mediterranean

    Science.gov (United States)

    Colbourne, Mark; Hall, Jeremy; Aksu, Ali; Çifçi, Günay

    2014-05-01

    The Anaximander Mountains are one of the many enigmatic structures situated along the morphologically and structurally complicated junction between the Hellenic and Cyprus Arcs, in the eastern Mediterranean. Interpretation of ~750 km of marine multi-channel seismic reflection data show that the present day Anaximander Mountains underwent several distinct phases of tectonic activity since Miocene. During the mid-late Miocene, a protracted, contractional tectonic regime produced the east-west trending, south-verging fold-thrust belt observed in the area. The Messinian was a period of relatively low tectonic activity, and is marked by the deposition of an evaporite layer. This phase lasted until the latest Miocene - earliest Pliocene, when a major erosional event associated with the Messinian salinity crisis occurred. Beginning in the early-mid Pliocene-Quaternary a transpressional and rotational tectonic regime prevailed over the area. The Anaximander Mountain (sensu stricto) and Anaximenes Mountain developed in the Pliocene-Quaternary associated with the reactivation, uplift and rotation of a linked, thick skinned pre-Messinian imbricate thrust fan. Back thrusting in the region accentuated the morphology of these mountains. The Anaxagoras Mountain differs both lithologically and morphologically from the Anaximander Mountain (sensu stricto) and the Anaximenes Mountain. It is probably developed associated with the emplacement of the ophiolitic Antalya Nappe Complex. Faulting in the Anaxagoras region is characterized by southwest striking thrust and/or oblique thrust faults. Due to the similarities in morphology between the Isparta Angle of southwestern Turkey and the Anaximander Mountains (sensu lato), it is hypothesized that the tectonic evolution of the two regions are similar in nature. The Anaximander Mountains (sensu lato) can thus be considered the offshore replication of the Isparta Angle, produced by similar mechanisms, but being of a younger age.

  10. Geologic-tectonic evolutional characteristics and prospecting potential for ISL-amenable sandstone-type uranium deposits; in Sichuan basin

    International Nuclear Information System (INIS)

    Through the analysis on geologic-tectonic evolution of Sichuan basin, authors of this paper suggest: because of the heterogeneity of the basin basement and cover structures resulting from the lateral dividing, those segments in the basin that experienced only weak tectonic activation, and those that were uplifted and eroded earlier have not been intensely deformed, and have not experienced long-period burying. Rocks in those segments are poorly consolidated and there exist conditions for the formation of large-area artesian slope at the transitional sites between uplifted and subsided areas, possessing favourable hydrogeologic conditions for long-term infiltration of groundwater. These areas must be the targets for prospecting for ISL-amenable sandstone-type uranium deposits. Correspondingly, the Triassic and Jurassic where loose sand bodies are hosted are prospecting target horizons for uranium. (authors)

  11. Tectonic-structural systems of Mars: Is it possible to use them to reconstruct its thermal evolution?

    Directory of Open Access Journals (Sweden)

    J. F. Valdés-Galicia

    2004-12-01

    Full Text Available This work tries to establish the possible relationship among cortical stresses evidenced by faults mapped in the surface and thermal evolution on Mars. To achieve it, we made an initial classification of the tectonic-structural systems that appear in surface, which were detected by diverse missions from orbit. This classification was based on the association of the tectonic-structural features with specific geologic features, which allows to divide them in four groups: I Grabens and normal faults parallel and radially associated to the Tharsis volcanic bulge. II Tectonic systems associated to the volcanoes that crown the Tharsis bulge, to the volcanic mons of Elysium and the surroundings of the Isidis, Argyre and Hellas impact basins. III Wrinkle ridges that extend for almost the entire planet. IV A series of secondary ridges associated to the crustal dichotomy. Later we suggest a classification based on the surface extension and on the possible geologic processes that could have originated the different tectonic structures. This last classification allows to associate stresses to specific processes and it contemplates three groups of deformations: local, regional and global deformations. Finally the possible causes of the stresses are suggested, which include: global stresses due to expansion or thermal contraction, regional or local stresses due to thermal anomalies in the mantle and to lithospheric loads, stresses due to impacts, among others. This allowed to suggest a possible thermal evolution that outlines an initial heating for accretion, followed by an abrupt cooling in a very short period of time and a later secular cooling, which remains in the present time.

  12. Metamorphic and tectonic evolution of the Greater Himalayan Crystalline Complex in Nyalam region, south Tibet

    Science.gov (United States)

    Wang, Jia-Min; Zhang, Jin-Jiang; Rubatto, Daniela

    2016-04-01

    Recent studies evoke dispute whether the Himalayan metamorphic core - Greater Himalayan Crystalline Complex (GHC) - was exhumed as a lateral crustal flow or a critical taper wedge during the India-Asia collision. This contribution investigated the evolution of the GHC in the Nyalam region, south Tibet, with comprehensive studies on structural kinematics, metamorphic petrology and geochronology. The GHC in the Nyalam region can be divided into the lower and upper GHC. Phase equilibria modelling and conventional thermobarometric results show that peak temperature conditions are lower in the lower GHC (~660-700°C) and higher in the upper GHC (~740-780°C), whereas corresponding pressure conditions at peak-T decrease from ~9-13 kbar to ~4 kbar northward. Monazite, zircon and rutile U-Pb dating results reveal two distinct blocks within the GHC of the Nyalam region. The upper GHC underwent higher degree of partial melting (15-25%, via muscovite dehydration melting) that initiated at ~32 Ma, peaked at ~29 Ma to 25 Ma, possibly ended at ~20 Ma. The lower GHC underwent lower degree of melting (0-10%) that lasted from 19 to 16 Ma, which was produced mainly via H2O-saturated melting. At different times, both the upper and lower blocks underwent initial slow cooling (35 ± 8 and 10 ± 5°C/Myr, respectively) and subsequent rapid cooling (120 ± 40°C/Myr). The established timescale of metamorphism suggests that high-temperature metamorphism within the GHC lasted a long duration (~15 Myr), whereas duration of partial melting lasted for ~3 Myr in the lower GHC and lasted for 7-12 Myr in the upper GHC. The documented diachronous metamorphism and discontinuity of peak P-T conditions implies the presence of the Nyalam Thrust in the study area. This thrust is probably connected to the other thrusts in Nepal and Sikkim Himalaya, which extends over ~800 km and is named the "High Himalayan Thrust". Timing of activity along this thrust is at ~25-16 Ma, which is coeval with active

  13. Rift architecture and evolution: The Sirt Basin, Libya: The influence of basement fabrics and oblique tectonics

    Science.gov (United States)

    Abdunaser, K. M.; McCaffrey, K. J. W.

    2014-12-01

    zones and adjoining highs. Late Eocene rocks exposed in the western part of the basin exhibit a complex network of branching segmented normal and strike-slip faults, generally with a NNW-SSE structural orientations. Many surface structural features have been interpreted from satellite images which confirm sinistral strike-slip kinematics. Relay ramp structures, numerous elongate asymmetric synclines associated with shallow west limbs and steeper dipping east limbs are developed in the hangingwalls adjacent to west downthrowing normal faults. These structural patterns reflect Cretaceous/Tertiary extensional tectonics with additional control by underlying pre-existing Pan-African basement fabrics and ENE-WSW trending Hercynian structures. We relate the Sirt Basin rift development as exemplified in our study area to the break-up of Gondwana represented by the structural evolution of the West-Central African rift system, and the South and Central Atlantic, the Tethys and the Indian Oceans.

  14. Quantifying Tectonic Controls on Regional Cenozoic Surface Evolution in the Eastern Lhasa Block

    Science.gov (United States)

    Schmidt, J. L.; Zeitler, P. K.; Shuster, D. L.; Tremblay, M. M.; Harrison, M.

    2013-12-01

    and their frequent coincidence with major N-S trending rifts suggests a coupling of plateau-scale tectonics and local-scale erosional patterns. We propose that a change in river base level drove Jiacha knickpoint formation and subsequent upstream migration and that its present-day spatial correlation with the Nari Yun Chu Rift indicates that additional headward cutting is accommodated by motion on the rift, thereby pinning the knickpoint and preventing further incision of the Tsangpo and dissection of the Tibetan plateau. Preliminary geomorphic analysis of the Tsangpo and Nyang rivers and their tributaries including SL-indices and slope-area plots indicates that a set of ~3500 m elevation knickpoints remnant of the migration of the Jiacha knickpoint exists through the drainage network. Additional 4He/3He apatite analyses are in progress to determine the time-temperature evolution of bedrock samples downstream of the knickpoint to constrain the timing of gorge incision along the Yarlung Tsangpo, testing the hypothesis that if the knickpoint evolved by upstream migration samples downstream of the knickpoint, the onset of rapid cooling should be positively correlated with distance from the knickpoint.

  15. Tectonic evolution of Tarim basin in Cambrian–Ordovician and its implication for reservoir development, NW China

    Indian Academy of Sciences (India)

    Yu Bingsong; Ruan Zhuang; Zhang Cong; Pan Yinglu; Lin Changsong; Wang Lidong

    2016-03-01

    In order to find the impact of regional tectonic evolution of Tarim basin on the inside distribution of sedimentary facies and reservoir development, this paper, based on the research of plate-tectonic evolution of Tarim basin, conducts an in-depth analysis on the basin’s inside sedimentary response to the Eopaleozoicregional geodynamic reversion from extension to convergence around Tarim plate, and concludes that the regional geodynamic environment of surrounding areas closely contributes to the formation and evolution of paleo-uplifts, differentiation of sedimentary facies in platform, distribution of high-energyreef and bank facies belts, conversion of sedimentary base level from fall to rise, obvious change of lithology from dolomite to limestone, and formation of several unconformity surfaces in Ordovician system in the basin. A series of sedimentary responses in the basin are controlled by regional dynamic setting, which not only controls the distribution of reservoirs in reef and bank facies but also restricts the development and distribution of karst reservoirs controlled by the unconformity surfaces. This offers the macro geological evidences for us to further analyze and evaluate the distribution of favorable reservoirs.

  16. Tectonic evolution of Tarim basin in Cambrian-Ordovician and its implication for reservoir development, NW China

    Science.gov (United States)

    Bingsong, Yu; Zhuang, Ruan; Cong, Zhang; Yinglu, Pan; Changsong, Lin; Lidong, Wang

    2016-03-01

    In order to find the impact of regional tectonic evolution of Tarim basin on the inside distribution of sedimentary facies and reservoir development, this paper, based on the research of plate-tectonic evolution of Tarim basin, conducts an in-depth analysis on the basin's inside sedimentary response to the Eopaleozoic regional geodynamic reversion from extension to convergence around Tarim plate, and concludes that the regional geodynamic environment of surrounding areas closely contributes to the formation and evolution of paleo-uplifts, differentiation of sedimentary facies in platform, distribution of high-energy reef and bank facies belts, conversion of sedimentary base level from fall to rise, obvious change of lithology from dolomite to limestone, and formation of several unconformity surfaces in Ordovician system in the basin. A series of sedimentary responses in the basin are controlled by regional dynamic setting, which not only controls the distribution of reservoirs in reef and bank facies but also restricts the development and distribution of karst reservoirs controlled by the unconformity surfaces. This offers the macro geological evidences for us to further analyze and evaluate the distribution of favorable reservoirs.

  17. Evolution of the Central Indian tectonic zone: Geochemical and isotope-geochronological data

    Directory of Open Access Journals (Sweden)

    Kaulina T.V.

    2015-06-01

    Full Text Available In the framework of the Russian-Indian joint research projects geochemical and geochronological study of granitoid rocks across the Central Indian Tectonic Zone has been carried out. Geochronological data suggest that the Central Indian Tectonic Zone is composed primarily of Proterozoic rocks, formed as a result of several stages of granitoid magmatism: at 2.43, 2.34-2.31, 1.73-1.72 and 1.53-1.51 Ga. Metamorphic transformations reflected by Sm–Nd and Rb–Sr systems of rocks and minerals occurred 1.37-1.1 Ga ago that allows comparing the final processes in the Central Indian Tectonic Zone with the Grenville orogeny and it can be used for the reconstruction of Rodinia

  18. Cenozoic paleoaltimetry of the SE margin of the Tibetan Plateau: Constraints on the tectonic evolution of the region

    Science.gov (United States)

    Li, Shanying; Currie, Brian S.; Rowley, David B.; Ingalls, Miquela

    2015-12-01

    An improved understanding of the elevation history of the Tibetan Plateau is crucial in discriminating among the various tectonic models for the evolution of the India-Asia continental collision. We reconstruct the paleoelevation history for three Cenozoic sedimentary basins from SE Tibet and Yunnan, China, to provide more constraints on the tectonic processes for raising the SE margin of the Tibetan Plateau. The results presented here, together with those of previous studies, indicate that (1) the plateau margin of NW Yunnan was near its elevation (˜ 2.6 km) by the latest middle Eocene (˜ 40 Ma); (2) the plateau margin of SE Yunnan reached its current elevation (˜ 1.6 km) by the middle Miocene (˜ 13 Ma). Interpretations of the tectonic processes responsible for this inferred surface uplift of the region are made in the context of well-documented surface geology. We conclude that high landscape (˜ 2.6 km elevation) in NW Yunnan may represent the remnants of the Eocene Tibetan plateau that originally formed in the northeastern Qiangtang Block by crustal thickening associated with the India-Asia continental collision. The near-modern elevation of SE Yunnan since ˜ 13 Ma probably reflects the initiation of lower crustal flow in this area by at least that time. Collectively, our paleoaltimetric interpretations disagree with previously proposed models of middle Miocene to Pliocene crustal flow acting as a sole tectonic process for raising the SE margin of the plateau, but support a protracted history of surface uplift that most likely involved crustal thickening during the Eocene, southeastward extrusion of a portion of Eocene Tibetan plateau during the Oligocene to early Miocene, and lower crustal flow beneath this region since at least the early Miocene.

  19. Late Quaternary displacement rate, paleoseismicity, and geomorphic evolution of the Alpine Fault : evidence from Hokuri Creek, south Westland, New Zealand

    International Nuclear Information System (INIS)

    A 400 ± 100 m offset of Lake McKerrow, South Westland, New Zealand, combined with dated (15.6 ka) glacial lake silts, requires an Alpine Fault displacement rate of 26 ± 7 mm/yr. Moraines associated with Hokuri Creek (assumed to be 17 ± 2 ka) are offset by 440 ± 40 m and require a displacement rate on the Alpine Fault of 26 ± 6 mm/yr. Slickensides, fault exposure, and offset topography are consistent with an almost pure dextral sense of movement on a vertical or subvertical fault. Locally, a small vertical component of up-to-the-west movement is observed. Folding in late Quaternary sediments indicates active tilting of sediments at up to 0.4 degrees/ka and variations in local uplift/subsidence rates of up to 4 mm/yr. At one locality c.1 km northwest of the Alpine Fault and near the core of an anticline, uplifted shells require an uplift rate of 1.4 ± 0.5 mm/yr relative to sea level. Displaced river channels provide estimates of the last two coseismic displacements on the fault of 9 m (penultimate) and 8 m. This suggests characteristic earthquake behaviour with a recurrence interval of 330 ± 90 yr and probable Mw > 7.5. Radiocarbon dating suggests the last coseismic displacement occurred just after 370 ± 150 cal yr B.P. (author). 34 refs., 10 figs., 3 tabs

  20. Tectonic evolution, structural styles, and oil habitat in Campeche Sound, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Angeles-Aquino, F.J.; Reyes-Nunez, J.; Quezada-Muneton, J.M.; Meneses-Rocha, J.J. [Pemex Exploracion-Produccion, Mexico City (Mexico)

    1994-12-31

    Campeche Sound is located in the southern part of the Gulf of Mexico. This area is Mexico`s most important petroleum province. The Mesozoic section includes Callovian salt deposits; Upper Jurassic sandstones, anhydrites, limestones, and shales; and Cretaceous limestones, dolomites, shales, and carbonate breccias. The Cenozoic section is formed by bentonitic shales and minor sandstones and carbonate breccias. Campeche Sound has been affected by three episodes of deformation: first extensional tectonism, then compressional tectonism, and finally extensional tectonism again. The first period of deformation extended from the middle Jurassic to late Jurassic and is related to the opening of the Gulf of Mexico. During this regime, tilted block faults trending northwest-southwest were dominant. The subsequent compressional regime occurred during the middle Miocene, and it was related to northeast tangential stresses that induced further flow of Callovian salt and gave rise to large faulted, and commonly overturned, anticlines. The last extensional regime lasted throughout the middle and late Miocene, and it is related to salt tectonics and growth faults that have a middle Miocene shaly horizon as the main detachment surface. The main source rocks are Tithonian shales and shaly limestones. Oolite bars, slope and shelf carbonates, and regressive sandstones form the main reservoirs. Evaporites and shales are the regional seals. Recent information indicates that Oxfordian shaly limestones are also important source rocks.

  1. Tectonic and hydrogeological evolution and its relation to sandstone-type uranium ore-formation in Xihulitu basin, Inner Mongolia

    International Nuclear Information System (INIS)

    The Xihulitu basin is an Early Cretaceous down-faulted basin. It was disintegrated into three sub-basins (blocks) by the post-depositional fault displacement. Owing to the connection resulting from the fault structure, a complete groundwater recharge-run off-discharge system was developed leading to the formation of apparent hydrogeologic zonation and different geochemical environments, and creating favourable conditions for the uranium migration, concentration and ore-formation. The tectonic-hydrogeologic evolution of the basin includes the following three stages: (1) the open cycle of down-faulted basin formation; (2) the close cycle sedimentation and diagenesis, and (3) the run-off cycle of epigenetic reworking. Of them, the paleohydrogeologic evolution of epigenetic reworking run-off stage is the main period for the formation of sandstone-type uranium deposit. (authors)

  2. Triple junction orogeny: tectonic evolution of the Pan-African Northern Damara Belt, Namibia

    Science.gov (United States)

    Lehmann, Jérémie; Saalmann, Kerstin; Naydenov, Kalin V.; Milani, Lorenzo; Charlesworth, Eugene G.; Kinnaird, Judith A.; Frei, Dirk; Kramers, Jan D.; Zwingmann, Horst

    2014-05-01

    Trench-trench-trench triple junctions are generally geometrically and kinematically unstable and therefore can result at the latest stages in complicated collisional orogenic belts. In such geodynamic sites, mechanism and timescale of deformations that accommodate convergence and final assembly of the three colliding continental plates are poorly studied. In western Namibia, Pan-African convergence of three cratonic blocks led to pene-contemporaneous closure of two highly oblique oceanic domains and formation of the triple junction Damara Orogen where the NE-striking Damara Belt abuts to the west against the NNW-striking Kaoko-Gariep Belt. Detailed description of structures and microstructures associated with remote sensing analysis, and dating of individual deformation events by means of K-Ar, Ar-Ar (micas) and U-Pb (zircon) isotopic studies from the Northern Damara Belt provide robust constraints on the tectonic evolution of this palaeo-triple junction orogeny. There, passive margin sequences of the Neoproterozoic ocean were polydeformed and polymetamorphosed to the biotite zone of the greenschist facies to up to granulite facies and anatexis towards the southern migmatitic core of the Central Damara Belt. Subtle relict structures and fold pattern analyses reveal the existence of an early D1 N-S shortening event, tentatively dated between ~635 Ma and ~580 Ma using published data. D1 structures were almost obliterated by pervasive and major D2 E-W coaxial shortening, related to the closure of the Kaoko-Gariep oceanic domain and subsequent formation of the NNW-striking Kaoko-Gariep Belt to the west of the study area. Early, km-scale D1 E-W trending steep folds were refolded during this D2 event, producing either Type I or Type II fold interference patterns visible from space. The D2 E-W convergence could have lasted until ~533 Ma based on published and new U-Pb ages. The final D3 NW-SE convergence in the northernmost Damara Belt produced a NE-striking deformation

  3. Gravity sliding in basinal setting, a surficial record of tectonic and geodynamic evolution; examples from the southern W. Alps and their foreland

    Science.gov (United States)

    Dumont, T.; Franzi, V.; Matthews, S. J.

    2012-04-01

    The occurrence of large-scale submarine landslides, although commonly observed in the present basins, is only exceptionally mentioned in the Alpine orogen and foreland. The southern part of the Western Alpine arc and the SE basin of France provide examples of such features which could be related with particular geodynamic events, in relation with the motion of the Iberian and Adriatic microplates : - A >50km2 slump scar formed in Aptian times at the northwestern edge of the SE France (so-called Vocontian) basin, giving a low-angle detachment surface which was onlapped by Albian hemipelagic marls (Ferry & Flandrin, 1979). The latter mark the maximum deepening stage of the basin, and the head of the scar is located over a deep-seated fault bounding the platform, which strongly suggest that sliding was caused by differential subsidence due to Middle Cretaceous extension, as a consequence of Iberia-Europe divergence. - Later on, a deep-marine erosion surface developed further down the basin over a >100km2 area (Dévoluy massif; Michard et al., 2010), which had been previously affected by Mid-Cretaceous extension. Typical inversion structures are found beneath the surface, which indicate that NS shortening overprinted the extensional pattern. The removal of up to 400m of Mesozoic sediments was controlled by gravity processes, probably triggered by the deformation of the basin floor following tectonic inversion. The overlying pelagic carbonates indicate that shortening occurred before the Campanian, which is closely comparable with the earliest stages of tectonic inversion in the Pyrenees. - The transition slope between the Paleogene Alpine flexural basin and the NW-ward propagating accretionary prism provides examples of basin floor degradation and of gravity-driven emplacement of large-scale blocks, generally regarded as thrust-sheets in the Alps. These features allow to reconstruct the early stages of the Adria-Europe collision, which strongly differ from the Oligo

  4. Hillslope morphology as an indicator of landscape evolution in tectonically active landscapes

    OpenAIRE

    Hurst, Martin David

    2013-01-01

    Hillslopes comprise the majority of unglaciated upland landscapes; they are the primary source for the production of sediment from bedrock, and the routing system by which sediment is delivered to the channel network. Yet the nature of hillslope response to changes in tectonic, climatic or base-level boundary conditions is poorly understood in terms of the spatial and temporal distribution of hillslope morphology. Here I exploit a previously published framework for exploring hi...

  5. Plate-tectonic evolution of the western U.S.A.

    Science.gov (United States)

    Hamilton, W.

    1987-01-01

    Changing interactions of lithospheric plates provide the framework for this review of the 3100 m.y. geological history of some 3 million km2 of mountains, deserts, plateaux and plains. The Precambrian to Neogene development of the western U.S.A. is outlined in terms of plate collisions, subduction events and deformation of lithospheric slabs, with some interpretations based on SE Asia and other regions of complex tectonics.-R.A.H.

  6. Paleomagnetic constraints for the tectonic evolution of the southern Apennines belt (Italy)

    OpenAIRE

    Gattacceca, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia

    2007-01-01

    The southern Apennine belt is formed by nappes that have undergone large (i. e. hundreds of kms) horizontal displacements. In such tectonic scenario, orogenic rotations of nappes are clearly expected, and paleomagnetism may represent a key tool to constrain displacements and understand the pre-orogenic paleogeography. Recent paleomagnetic data have shown that the Apenninic carbonate platform, on top of the nappe pile, has rotated ~80° counterclockwise (CCW) after Langhian...

  7. Tectonic evolution of the Gaoua region, Burkina Faso : implications for mineralization

    OpenAIRE

    Baratoux, Lenka; Metelka, V.; Naba, S.; Ouiya, P.; Siebenaller, Luc; Jessell, Mark; Nare, A.; Salvi, S.; Beziat, D.; De Franceschi, G.

    2015-01-01

    The interpretation of high-resolution airborne geophysical data integrated with field structural and lithological observations were employed in the creation of a litho-structural framework for the Gaoua region, Burkina Faso. The granite-greenstone domain of Paleoproterozoic age was affected by multiple deformation and mineralization events. The early tectonic phase is characterized by the emplacement of voluminous tholeiitic and calc-alkaline lavas, probably in a volcanic arc setting. The cop...

  8. Periodic Vesicle Formation in Tectonic Fault Zones—an Ideal Scenario for Molecular Evolution

    OpenAIRE

    Mayer, Christian; Schreiber, Ulrich; Dávila, María J.

    2015-01-01

    Tectonic fault systems in the continental crust offer huge networks of interconnected channels and cavities. Filled mainly with water and carbon dioxide (CO2), containing a wide variety of hydrothermal chemistry and numerous catalytic surfaces, they may offer ideal reaction conditions for prebiotic chemistry. In these systems, an accumulation zone for organic compounds will develop at a depth of approximately 1 km where CO2 turns sub-critical and dissolved components precipitate. At this poin...

  9. Polyphase tectonic evolution of the Aksu Basin, Isparta Angle (Southern Turkey)

    Science.gov (United States)

    Üner, Serkan; Özsayin, Erman; Kutluay, Alkor; Dirik, Kadir

    2015-04-01

    The Aksu Basin, within the Isparta Angle, is located to the north of the intersection of the Aegean and Cyprus arcs and has been evolving since the Middle Miocene. Correlation of: (1) kinematic analysis of fault planes that cut the basin fill, (2) the reactivation/inversion of fault planes and (3) sedimentological data indicate that the Aksu Basin has evolved by four alternating compressional and extensional tectonic phases since its formation. The first phase was NW-SE oriented compression caused by the emplacement of the Lycian Nappe units which ended in Langhian. This compressional phase that induced the formation and the initial deformation of the basin was followed by a NW-SE extensional phase. This tectonic phase prevailed between the Langhian and Messinian and was terminated by a NE-SW compressional regime known as the Aksu Phase. The neotectonic period is characterized by NE-SW extension and began in the Late Pliocene. Correlation with the existing tectonic literature shows that the order of deformational phases proposed in this study might also be valid for the entire Isparta Angle area.

  10. Evolution of 3D tectonic stress field and fault movement in North China

    Institute of Scientific and Technical Information of China (English)

    陈连旺; 陆远忠; 郭若眉; 许桂林; 张杰

    2001-01-01

    Based on data of fault movement surveying, we simulate the evolution process of three dimensional stress field in North China by three dimensional finite element method. Evolutional patterns in one-year time scale from 1986 to 1997 have been illustrated and the evolution characteristics of stress field have been analyzed. In comparison with the seismic activity among that time interval in North China, we have primarily discussed the relationship between the evolution of stress field and seismic activity.

  11. Large Sanjiang basin groups outside of the Songliao Basin Meso-Senozoic Tectonic-sediment evolution and hydrocarbon accumulation

    Science.gov (United States)

    Zheng, M.; Wu, X.

    2015-12-01

    The basis geological problem is still the bottleneck of the exploration work of the lager Sanjiang basin groups. In general terms, the problems are including the prototype basins and basin forming mechanism of two aspects. In this paper, using the field geological survey and investigation, logging data analysis, seismic data interpretation technical means large Sanjiang basin groups and basin forming mechanism of the prototype are discussed. Main draw the following conclusions: 1. Sanjiang region group-level formation can be completely contrasted. 2. Tension faults, compressive faults, shear structure composition and structure combination of four kinds of compound fracture are mainly developed In the study area. The direction of their distribution can be divided into SN, EW, NNE, NEE, NNW, NWW to other groups of fracture. 3. Large Sanjiang basin has the SN and the EW two main directions of tectonic evolution. Cenozoic basins in Sanjiang region in group formation located the two tectonic domains of ancient Paleo-Asian Ocean and the Pacific Interchange. 4. Large Sanjiang basin has experienced in the late Mesozoic tectonic evolution of two-stage and nine times. The first stage, developmental stage basement, they are ① Since the Mesozoic era and before the Jurassic; ② Early Jurassic period; The second stage, cap stage of development, they are ③ Late Jurassic depression developmental stages of compression; ④ Early Cretaceous rifting stage; ⑤ depression in mid-Early Cretaceous period; ⑥ tensile Early Cretaceous rifting stage; ⑦ inversion of Late Cretaceous tectonic compression stage; ⑧ Paleogene - Neogene; ⑨ After recently Ji Baoquan Sedimentary Ridge. 5. Large Sanjiang basin group is actually a residual basin structure, and Can be divided into left - superimposed (Founder, Tangyuan depression, Hulin Basin), residual - inherited type (Sanjiang basin), residual - reformed (Jixi, Boli, Hegang basin). there are two developed depression and the mechanism

  12. Chronostratigraphy and sediment evolution in an alpine karst : the Aranzadi Gallery (Gouffre de la Pierre Saint Martin, Pyrenees, France)

    International Nuclear Information System (INIS)

    In the ''Gouffre de la Pierre Saint Martin'', the Aranzadi Gallery is a notable sediment trap. A thick filling consists of three discordant detrital sets: a lower unit mainly made of round-stones, a main unit with largely predominant carbonated clays, river terrace deposits covering successive steps hollowed in the main unit. This set took place during glacial periods and shows how evolves the sedimentology in a high alpine cave during glacial periods. Dates obtained from the speleothems cover the period between 300 000 B.P. and the Holocene. (Author)

  13. The preliminarily exploration of area uranium mineralization tectonic evolution IN320 deposit

    International Nuclear Information System (INIS)

    320 deposit locates at middle south in Gan-Xiang-Gui Diwa series and west south in Xiang-Dong Diwa in southeastern China Diwa region in east-Asia crust. It is controlled by paleographic zone of lithofacies environment and relates to regional Diwa tectonic action closely. Especially it relies closely on the growing and developing of the several times active Xiang-Dong Rifts and forms a series of Uranium mineralization that relates to rift structure. The rifts controls the distribution of area band deposit in which 320 deposit is center

  14. New insights into the tectonic evolution of the Andaman basin, northeast Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    KameshRaju, K.A.; Ramprasad, T.; Rao, P.S.; Rao, B; Varghese, J.

    .A. Kamesh Raju), rprasad@darya.nio.org (T. Ramprasad), psrao@darya.nio.org (P.S. Rao), brrao@darya.nio.org (B. Ramalingeswara Rao), juby_v@yahoo.com (J. Varghese). EPSL 7024 25-3-04 Cyaan Magenta Geel Zwart Earth and Planetary Science Letters 221 (2004) 145...^162 R Available online at www.sciencedirect.com www.elsevier.com/locate/epsl Fig. 1. Geodynamic setting of the northeastern Indian Ocean, encompassing the Andaman Islands. (a) Tectonic elements of the region compiled from previous studies [3]. Stippled...

  15. Magmatic responses to Late Cretaceous through Oligocene tectonic evolution of the western Alaska Range

    Science.gov (United States)

    Todd, E.; Jones, J. V., III; Karl, S.; Ayuso, R. A.; Bradley, D. C.; Box, S. E.; Haeussler, P. J.

    2014-12-01

    New geochemistry, U/Pb geochronology, and radiogenic isotopes, together with existing datasets, contribute to a refined model of the petrogenetic history of magmatism in the western Alaska Range. Plutons within the study area were emplaced into Kahiltna basin Mesozoic turbiditic strata. The Kahiltna sequence overlies Mesozoic Peninsular oceanic terrane rocks in the SE half of the basin and Proterozoic to Paleozoic Farewell continental terrane rocks to the NW. This study focuses on successive intrusion suites, most of which are thought to intrude Kahiltna or underlying Farewell terrane rocks, but include older, perhaps more deeply exhumed rocks emplaced in Peninsular terrane basement to the SE. The chemically diverse sequence records magmatism associated with major tectonic reorganization events on the southern Alaska circum-Pacific subduction margin. The oldest pluton suite (~100-80 Ma) is mostly intermediate to evolved calcalkaline granite and coincides with final closure of the Kahiltna basin and a regional transition to transpression-dominated tectonics. The post-closure magmatic pulse (~75-67 Ma) is compositionally varied, including primitive subalkaline melts, peraluminous high-K granites, and a subset of sodic, adakite-like granites. A Paleocene (~63-57 Ma) magmatic flare-up follows, dominated by extremely fractionated subalkaline melts. Rare, more primitive melts of this suite are metaluminous, from gabbro to syenite. This stage may represent relaxed melt productivity or shallowing of the slab dip, yielding more laterally diffuse melting. An early Eocene magmatic hiatus precedes middle Eocene circum-Pacific tectonic reorganization, regionally resulting in initiation of proto-Aleutian/Meshik arc magmatism, and locally in the 44-37 Ma emplacement of subalkaline intermediate to felsic plutons associated with andesite to rhyolite volcanic deposits. An Oligocene (~31-25 Ma) magmatic pulse involved emplacement of a compositionally variable suite ranging from

  16. Active tectonics and Quaternary landscape evolution across the western Panama block, Costa Rica, Central America

    Science.gov (United States)

    Marshall, Jeffrey Scott

    Three aspects of active tectonism are examined across central Costa Rica: (1) fault kinematics; (2) volcanic arc retreat; and (3) spatially variable coastal uplift. Diffuse faulting along the Central Costa Rica Deformed Belt (CCRDB) defines the western margin of the Panama block and aligns with the rough-smooth boundary (RSB) on the subducting Cocos plate. Sub-horizontal subduction of rough, hotspot thickened crust (Cocos Ridge and seamounts) shifts active shortening into the volcanic arc along the CCRDB. Mesoscale faults express variable kinematics across three domains: transtension in the forearc, transcurrent motion across the volcanic arc, and transpression in the back arc. Fault kinematics agree with seismicity and GPS data, and isotopic ages confirm that faulting postdates the late Neogene onset of shallow subduction. Stratigraphic correlation augmented by 40Ar/39Ar dating constrain the timing of Quaternary arc migration from the Neogene Aguacate range to the modern Cordillera Central. The Valle Central basin, between the cordilleras, filled with thick sequences of lavas, pyroclastic flows, and lahars. Middle Pleistocene drainage capture across the Aguacate arc linked the Valle Central with the Pacific slope and ash flows descended onto the coastal Orotina debris fan. Arc retreat reflects slab shallowing and enhanced tectonic erosion as rough crust entered the subduction zone. Differing subduction parameters across the RSB (crustal age, slab dip, roughness) produce marked contrasts in coastal tectonism. Varying uplift rates across coastal faults reflect sub-horizontal subduction of seamount roughness. Three groups (I--III) of fluvial terraces are correlated along the coast by isotopic ages and geomorphic characteristics. Base level fluctuations and terrace genesis reflect interaction between eustatic sea level and spatially variable rock uplift. Low uplift rates (north of RSB), yield one surface per terrace group, whereas moderate rates (south of RSB

  17. The 1590-1520 Ma Cachoeirinha magmatic arc and its tectonic implications for the Mesoproterozoic SW Amazonian craton crustal evolution

    Directory of Open Access Journals (Sweden)

    Ruiz Amarildo S.

    2004-01-01

    Full Text Available Isotopic and chemical data of rocks from the Cachoeirinha suite provide new insights on the Proterozoic evolution of the Rio Negro/Juruena Province in SW Amazonian craton. Six U-Pb and Sm-Nd analyses in granitoid rocks of the Cachoeirinha suite yielded ages of 1587-1522 Ma and T DM model ages of 1.88-1.75 Ga (EpsilonNd values of -0.8 to +1.0. In addition, three post-tectonic plutonic rocks yielded U-Pb ages from 1485-1389 Ma (T DM of 1.77-1.74 Ga and EpsilonNd values from -1.3 to +1.7. Variations in major and trace elements of the Cachoeirinha suite rocks indicate fractional crystallization process and magmatic arc geologic setting. These results suggest the following interpretations: (1 The interval of 1590-1520 Ma represents an important magmatic activity in SW Amazonian craton. (2 T DM and arc-related chemical affinity supportthe hypothesis that the rocks are genetically associated with an east-dipping subduction zone under the older (1.79-1.74 Ga continental margin. (3 The 1590-1520 Ma age of intrusive rocks adjacent to an older crust represents similar geological framework along the southern margin of Baltica, corroborating the hypothesis of tectonic relationship at that time.

  18. Laurentian origin for the North Slope of Alaska: Implications for the tectonic evolution of the Arctic

    Science.gov (United States)

    Strauss, J. V.; Macdonald, F. A.; Taylor, J. F.; Repetski, John E.; McClelland, W. C.

    2013-01-01

    The composite Arctic Alaska–Chukotka terrane plays a central role in tectonic reconstructions of the Arctic. An exotic, non-Laurentian origin of Arctic Alaska–Chukotka has been proposed based on paleobiogeographic faunal affinities and various geochronological constraints from the southwestern portions of the terrane. Here, we report early Paleozoic trilobite and conodont taxa that support a Laurentian origin for the North Slope subterrane of Arctic Alaska, as well as new Neoproterozoic–Cambrian detrital zircon geochronological data, which are both consistent with a Laurentian origin and profoundly different from those derived from similar-aged strata in the southwestern subterranes of Arctic Alaska–Chukotka. The North Slope subterrane is accordingly interpreted as allochthonous with respect to northwestern Laurentia, but it most likely originated farther east along the Canadian Arctic or Atlantic margins. These data demonstrate that construction of the composite Arctic Alaska–Chukotka terrane resulted from juxtaposition of the exotic southwestern fragments of the terrane against the northern margin of Laurentia during protracted Devonian(?)–Carboniferous tectonism.

  19. Seismo-stratigraphic evolution of the northern Austral Basin and its possible relation to the Andean tectonics, onshore Argentina.

    Science.gov (United States)

    Sachse, Victoria; Anka, Zahie; Pagan, Facundo; Kohler, Guillermina; Cagnolatti, Marcelo; di Primio, Rolando; Rodriguez, Jorge

    2013-04-01

    The Austral Basin is situated in a formerly and recently high active tectonic zone in southern Argentina. The opening of the South Atlantic to the east, the opening of the Drake Passage in the south, and the subduction related to the rise of the Andes to the west, had major influence on the study area. To identify the impact of the tectonic events on basin geometry, sediment thickness and depocenter migration through time, 2D seismic interpretation was performed for an area of approx. 180.000 km² covering the onshore northern Austral Basin. A total of 10 seismic horizons were mapped and tied to the stratigraphy from well reports, representing 9 syn- and post- rift sequences. The main units are: Basement (U1), Jurassic Tobifera Formation (U2), Early Cretaceous (U3), Late Cretaceous (U4), sub-unit Campanian (U4A), Paleocene (U5), Eocene (U6), Oligocene (U7), Miocene (U8), and Plio-Pleistocene (U9). Main tectonic events are identified representing the break-up phase forming graben systems and the evolution from the ancient backarc Rocas Verdes Basin to the foreland Austral Basin. Inversion and changes in the tectonic regime are concomitant with onlapping and thinning of the base of the Upper Cretaceous to Campanian sediments, while the Top of the Upper Cretaceous represents a Maastrichtian unconformity. Units depth maps show a triangular geometry since the Jurassic, tracing the north-eastern basement high and deepening to the south. Since the Campanian the former geometry of basin fill changed and deepening to the south stopped. Beginning of the foreland phase is assigned to this time as well as changes in the stress regime. Paleogene times are marked by a relatively high sedimentation rate coupled with enduring thermal subsidence, on-going rise of the Andes and changes in the convergence rates of the Nazca relative to the South American plate. Onset of sediment supply from the Andes (Incaic phase) resulted in enhanced sedimentation rates during the Paleocene

  20. Meso-cenozoic tectonic evolution character and metallogenesis of sandstone-type uranium deposits in Tarim Basin

    International Nuclear Information System (INIS)

    Based on comprehensive analyses on tectonic evolution of Tarim Basin and combined with isotopic ages of ores, the metallogenic stages of sandstone-type uranium deposits in the basin have been divided, the control of structures on ore-bearing strata and epigenetically altered metallogenic processes have been studied and it is believed that the structures before the last large-scale Himalayan Orogeny(before N2) are favorable for metallogenesis of sandstone-type uranium deposits and those after the Himalayan Orogeny mainly altered the ore bodies formed earlier. The metallogenic models for deposits controlled by structures have been studied and it is concluded that Kujieertai-type uranium deposits were formed in weakly deformed parts of structures, Sawabuqi-type uranium deposits were formed in strongly deformed parts of structures and however, Bashibulake-type uranium deposits were formed in the original red or mottled strata of K-N. (authors)

  1. The 1590-1520 Ma Cachoeirinha magmatic arc and its tectonic implications for the Mesoproterozoic SW Amazonian craton crustal evolution

    OpenAIRE

    Ruiz Amarildo S.; Geraldes Mauro C.; Matos João B.; Teixeira Wilson; Van Schumus William R.; Schmitt Renata S.

    2004-01-01

    Isotopic and chemical data of rocks from the Cachoeirinha suite provide new insights on the Proterozoic evolution of the Rio Negro/Juruena Province in SW Amazonian craton. Six U-Pb and Sm-Nd analyses in granitoid rocks of the Cachoeirinha suite yielded ages of 1587-1522 Ma and T DM model ages of 1.88-1.75 Ga (EpsilonNd values of -0.8 to +1.0). In addition, three post-tectonic plutonic rocks yielded U-Pb ages from 1485-1389 Ma (T DM of 1.77-1.74 Ga and EpsilonNd values from -1.3 to +1.7). Vari...

  2. Impact of Cenozoic strike-slip tectonics on the evolution of the northern Levant Basin (offshore Lebanon)

    Science.gov (United States)

    Ghalayini, Ramadan; Daniel, Jean-Marc; Homberg, Catherine; Nader, Fadi H.; Comstock, John E.

    2014-11-01

    Sedimentary basins adjacent to plate boundaries contain key tectonic and stratigraphic elements to understand how stress is transmitted through plates. The Levant Basin is a place of choice to study such elements because it flanks the Levant Fracture System and the Africa/Anatolia boundary. This paper uses new high-quality 3-D seismic reflection data to unravel the tectonic evolution of the margin of this basin during the Cenozoic, the period corresponding to the formation of the Levant Fracture System, part of the Africa/Arabia plate boundary. Four major groups of structures are identified in the interpreted Cenozoic units: NW-SE striking normal faults, NNE-SSW striking thrust-faults, ENE-WSW striking dextral strike-slip faults, and NNE trending anticlines. We demonstrate that all structures, apart of the NW-SE striking normal faults, are inherited from Mesozoic faults. Their reactivation and associated folding started during the late Miocene prior to the Messinian salinity crisis due to a NW-SE compressional stress field. No clear evidence of shortening at present-day offshore Lebanon and no large NNE-SSW strike-slip faults parallel to the restraining bend are found indicating that the Levant Fracture System is mainly contained onshore at present day. The intermittent activity of the interpreted structures correlates with the two stages of Levant Fracture System movement during late Miocene and Pliocene. This paper provides a good example of the impact of the evolution of plate boundaries on adjacent basins and indicates that any changes in the stress field, as controlled by the plate boundary, will affect immediately the preexisting structures in adjacent basins.

  3. The Geomorphological Evolution of a Landscape in a Tectonically Active Region: the Sennwald Landslide

    Science.gov (United States)

    Aksay, Selçuk; Ivy-Ochs, Susan; Hippe, Kristina; Graemiger, Lorenz; Vockenhuber, Christof

    2016-04-01

    The Säntis nappe is a fold-and-thrust structure in eastern Switzerland consisting of numerous tectonic discontinuities that make rocks vulnerable to rock failure. The Sennwald landslide is one of those events that occurred due to the failure of Lower Cretaceous Helvetic limestones. This study reveals the surface exposure age of the event in relation to geological and tectonic setting, earthquake frequency of the Central Alps, and regional scale climate/weather influence. Our study comprises detailed mapping of landform features, thin section analysis of landslide boulder lithologies, landslide volume estimation, numerical DAN-3D run-out modelling, and the spatial and temporal relationship of the event. In the Sennwald landslide, 92 million m3 of limestones detached from the south-eastern wall of the Säntis nappe and slid with a maximum travel distance of ~4'500 m and a "fahrboeschung" angle of 15° along the SE-dipping sliding plane almost parallel to the orientation of the bedding plane. Numerical run-out modelling results match the extent and the thickness of landslide deposits as observed in the field. The original bedrock stratigraphy was preserved as geologically the top layer in the bedrock package travelled the farthest and the bottom layer came to rest closest to the release bedrock wall during the landslide. Velocities of maximum 90 m/s were obtained from the numerical run-out modelling. Total Cl and 36Cl were determined at ETH AMS facility with isotope dilution methods defined in the literature (Ivy-Ochs et al., 2004). Surface exposure ages of landslide deposits in the accumulation area are revealed from twelve boulders. The distribution of limestone boulders in the accumulation area, the exposure ages, and the numerical run-out modelling support the hypothesis that the Sennwald landslide was a single catastrophic event. The event is likely to have been triggered by at least light to moderate earthquakes (Mw=4.0-6.0). The historical and the last 40-year

  4. Consequences of Chixculub Impact for the Tectonic and Geodynamic Evolution of the Gulf of Mexico North Carribean Region

    Science.gov (United States)

    Rangin, C.; Crespy, A.; Martinez-Reyes, J.

    2013-05-01

    The debate for Pacific exotic origin versus in situ inter American plate Atlantic origin of the Caribbean plate is active in the scientific community since decades. Independently of the origin of this plate, its fast motion towards the east at a present rate of 2cm/yr is accepted to have been initiated during the early-most Cenozoic. The Paleocene is a key period in the global evolution of Central America mainly marked also by the Chicxulub multiring meteor impact in Yucatan. We question here the genetic relationship between this impact event and the incipient tectonic escape of the Caribbean plate. The mostly recent published models suggest this impact has affected the whole crust down to the Moho, the upper mantle being rapidly and considerably uplifted. The crust was then fragmented 600km at least from the point of impact, and large circular depressions were rapidly filled by clastic sediments from Cantarell to Western Cuba via Chiapas and Belize. North of the impact, the whole Gulf of Mexico was affected by mass gravity sliding, initiated also during the Paleocene in Texas, remaining active in this basin up to present time. South of the impact, in the Caribbean plate, the Yucatan basin was rapidly opened, indicating a fast escape of the crustal material towards the unique free boundary, the paleo-Antilles subduction zone. Shear waves velocity data below the Caribbean plate suggest this crustal tectonic escape was enhanced by the fast eastward flowing mantle supporting a fragmented and stretched crust. The proposed model suggests Chicxulub impact (but also the hypothetic Beata impact) have fragmented brittle crust, then easily drifted towards the east. This could explain the Paleogene evolution of the Caribbean plate largely stretched during its early evolution. Geologically, this evolution could explain the absence of evident Paleogene oblique subduction along the Caribbean plate northern and southern margins, marked only by Mid Cretaceous dragged volcanic

  5. Interaction of tectonic and depositional processes that control the evolution of the Iberian Gulf of Cadiz margin

    Science.gov (United States)

    Maldonado, A.; Nelson, C.H.

    1999-01-01

    This study provides an integrated view of the growth patterns and factors that controlled the evolution of the Gulf of Cadiz continental margin based on studies of the tectonic, sedimentologic and oceanographic history of the area. Seven sedimentary regimes are identified, but there are more extensive descriptions of the late Cenozoic regimes because of the larger data base. The regimes of the Mesozoic passive margin include carbonate platforms, which become mixed calcareous-terrigenous deposits during the Late Cretaceous-early Tertiary. The Oligocene and Early Miocene terrigenous regimes developed, in contrast, over the active and transcurrent margins near the African-Iberian plate boundary. The top of the Gulf of Cadiz olistostrome, emplaced in the Late Miocene, is used as a key horizon to define the 'post-orogenic' depositional regimes. The Late Miocene progradational margin regime is characterized by a large terrigenous sediment supply to the margin and coincides with the closing of the Miocene Atlantic-Mediterranean gateways. The terrigenous drift depositional regime of the Early Pliocene resulted from the occurrence of high eustatic sea level and the characteristics of the Mediterranean outflow currents that developed after the opening of the Strait of Gibraltar. The Late Pliocene and Quaternary regimes are dominated by sequences of deposits related to cycles of high and low sea levels. Deposition of shelf-margin deltas and slope wedges correlate with regressive and low sea level regimes caused by eustasy and subsidence. During the highstand regimes of the Holocene, inner shelf prograding deltas and deep-water sediment drifts were developed under the influence of the Atlantic inflow and Mediterranean outflow currents, respectively. A modern human cultural regime began 2000 years ago with the Roman occupation of Iberia; human cultural effects on sedimentary regimes may have equalled natural factors such as climate change. Interplay of tectonic and

  6. A numerical model of continental topographic evolution integrating thin sheet tectonics, river transport, and climate

    Science.gov (United States)

    Garcia-Castellanos, D.; Jimenez-Munt, I.

    2013-12-01

    How much does the erosion and sedimentation at the crust's surface influence on the patterns and distribution of tectonic deformation? This question has been mostly addressed from a numerical modelling perspective, at scales ranging from local to orogenic. Here we present a model that aims at constraining this phenomenon at the continental scale. With this purpose, we couple a thin-sheet viscous model of continental deformation with a stream-power surface transport model. The model also incorporates flexural isostatic compensation that permits the formation of large sedimentary foreland basins and a precipitation model that reproduces basic climatic effects such as continentality and orographic rainfall and rain shadow. We quantify the feedbacks between these 4 processes in a synthetic scenario inspired by the India-Asia collision. The model reproduces first-order characteristics of the growth of the Tibetan Plateau as a result of the Indian indentation. A large intramountain basin (comparable to the Tarim Basin) develops when predefining a hard inherited area in the undeformed foreland (Asia). The amount of sediment trapped in it is very sensitive to climatic parameters, particularly to evaporation, because it crucially determines its endorheic/exorheic drainage. We identify some degree of feedback between the deep and the surface processes occurs, leading locally to a <20% increase in deformation rates if orographic precipitation is account for (relative to a reference model with evenly-distributed precipitation). These enhanced thickening of the crust takes place particularly in areas of concentrated precipitation and steep slope, i.e., at the upwind flank of the growing plateau. This effect is particularly enhanced at the corners of the indenter (syntaxes). We hypothesize that this may provide clues for better understanding the mechanisms underlying the intriguing tectonic aneurisms documented in the syntaxes of the Himalayas.

  7. Le tourisme alpin

    Directory of Open Access Journals (Sweden)

    Andrea Macchiavelli

    2009-06-01

    Full Text Available La forte croissance qu’ont connue les pays alpins dans les dernières décennies a surtout été fondée sur l’offre des activités du ski, avec comme conséquence, un massif développement immobilier, la multiplication d’infrastructures et l’extension des domaines. Aujourd’hui, le marché du ski semble arriver à saturation, la Convention alpine a mis un frein à la poursuite du développement des domaines skiables et on observe donc avec intérêt la diversification de l’offre soutenue par l’innovation. Après avoir rappelé les facteurs de changement en cours les plus significatifs dans le tourisme montagnard, l’article présente une grille interprétative de l’évolution des destinations touristiques alpines, identifiant les phases qui ont caractérisé son développement. Puis il propose une réflexion sur certaines conditions qui peuvent favoriser l’innovation dans le tourisme alpin, ainsi que sur les contradictions qui les accompagnent souvent. Dans la plupart des cas l’innovation est le résultat d’un processus qui a été lancé et qui s’est développé au sein de la communauté alpine, souvent favorisé et soutenu par des institutions nationales et internationales, et grâce auquel les difficultés structurelles qui ont déjà été abordées précédemment ont pu être surmontées avec succès.The spectacular increase in tourism in the Alps in recent decades has been founded mainly on the boom in skiing, resulting in both strong real estate development and an increasing array of infrastructures and ski runs. Today the ski market seems to have virtually reached saturation point and the winter sports sector needs to diversify its offer through innovation. After a review of the main factors of change in mountain tourism, the paper presents a grid for interpreting the life cycle of alpine destinations, identifying the phases that characterize their evolution. The conditions that may favour innovation in alpine

  8. Paleogeographic and tectonic controls on the evolution of Cenozoic basins in the Altiplano and Western Cordillera of southern Peru

    Science.gov (United States)

    Carlotto, Víctor

    2013-03-01

    Integrated studies of stratigraphy, sedimentology, paleogeography and tectonic controls on Cenozoic basins provide the basis for a series of time-slice reconstructions of basin evolution in the Andes of southern Peru. The Altiplano and adjacent margin of the Western Cordillera are characterized by several Paleocene-Miocene synorogenic continental basins with thicknesses locally exceeding 10 km. The evolution of these basins has been controlled by NW-trending tectonic features that mark the Altiplano-Western Cordillera and Altiplano-Eastern Cordillera boundaries and the Condoroma structural high. Sedimentary deposits of Paleocene age preserved in the Altiplano are the result of nonmarine sedimentation in a distal foreland basin. During the early Eocene, predominantly dextral strike-slip movements in the Altiplano between the Cusco-Lagunillas and Urcos-Ayaviri fault systems created the transpressional Kayra basin. The Soncco and Anta basins (middle Eocene-early Oligocene) are related to NE shortening (43-30 Ma) and represent proximal, wedge-top and foredeep basin environments preserved on the Altiplano. At ~ 29-28 Ma, a change to predominantly E-W shortening produced sinistral strike-slip motion along NW-striking faults, resulting in intermontane, transpressional basins. In the Altiplano, the Tinajani and Punacancha (29-5 Ma), and Paruro (12-6 Ma) basins were controlled by the Cusco-Lagunillas and the Urcos-Ayaviri fault systems. The Maure, Tincopalca-Huacochullo and Condoroma basins (22-5 Ma) of the Western Cordillera developed between the Condoroma high and the Cusco-Lagunillas fault system. Oligocene-Miocene sedimentation commonly evolved from proximal (alluvial) facies along the borders to distal (lacustrine) facies. These basins were linked to sinistral strike-slip faults that evolved into reverse-sinistral structures. Plate kinematics may play a role in Andean basin evolution, with deformation influenced by major preexisting faults that dictated paleogeographic

  9. Structural evolution and strike-slip tectonics off north-western Sumatra

    OpenAIRE

    Berglar, Kai; Gaedicke, Christoph; Franke, Dieter; Ladage, Stefan; Klingelhoefer, Frauke; Djajadihardja, Yusuf S.

    2010-01-01

    Based on new multi-channel seismic data, swath bathymetry, and sediment echosounder data we present a model for the interaction between strike-slip faulting and forearc basin evolution off north-western Sumatra between 2 degrees N and 7 degrees N. We examined seismic sequences and sea floor morphology of the Simeulue- and Aceh forearc basins and the adjacent outer arc high. We found that strike-slip faulting has controlled the forearc basin evolution since the Late Miocene. The Mentawai Fault...

  10. A hypothesis for Proterozoic-Phanerozoic supercontinent cyclicity, with implications for mantle convection, plate tectonics and Earth system evolution

    Science.gov (United States)

    Grenholm, Mikael; Scherstén, Anders

    2015-11-01

    We present a conceptual model for supercontinent cycles in the Proterozoic-Phanerozoic Eons. It is based on the repetitive behavior of C and Sr isotopes in marine carbonates and U-Pb ages and εHf of detrital zircons seen during the Neoproterozoic-Paleozoic and Paleoproterozoic Eras, respectively. These records are considered to reflect secular changes in global tectonics, and it is hypothesized that the repetitive pattern is caused by the same type of changes in global tectonics. The fundamental premise of this paper is that such repetitive changes should also be recorded in orogenic belts worldwide. This carries the implication that Neoproterozoic-Paleozoic orogenic belts should have Paleoproterozoic equivalents. It is proposed that this is the case for the East African, Uralides and Ouachita-Alleghanian orogens, which have Paleoproterozoic analogs in the West African-Amazon, Laurentian and East European cratons, respectively. The Neoproterozoic-Paleozoic orogenic belts are not isolated features but occur in a specific global context, which correspond to the relatively well-constrained Neoproterozoic break-up of Rodinia, and the subsequent Late Paleozoic assembly of Pangea. The existence of Paleoproterozoic equivalents to Neoproterozoic-Paleozoic orogens requires that the same cycle defined the Paleoproterozoic. We therefore hypothesize that there were Paleoproterozoic supercontinents equivalent to Rodinia and Pangea, and that Proterozoic-Phanerozoic supercontinents are comprised of two basic types of configurations, equivalent to Rodinia (R-type) and Pangea (P-type). The Paleoproterozoic equivalent of Rodinia is likely the first supercontinent to have formed, and Proterozoic-Phanerozoic supercontinent cycles are therefore defined by R- to R-type cycles, each lasting approximately 1.5 Gyr. We use this cyclic pattern as a framework to develop a conceptual model that predicts the configuration and cycles of Proterozoic-Phanerozoic supercontinents, and their

  11. Tectonic control on Pleistocene basin-filling processes and landscape evolution: the intermontane Kangra Basin, NW Sub-Himalaya, India

    Science.gov (United States)

    Dey, Saptarshi; Thiede, Rasmus; Schildgen, Taylor; Strecker, Manfred

    2015-04-01

    The growth of a collisional mountain belt like the Himalaya is dynamically coupled both to tectonics and climate and can result in strong temporal variations in the delivery of sediment to intermontane basins and the foreland. Orogenic critical taper models have been helpful to explain the processes controlling the evolution of mountain fronts in such settings. Rapid and voluminous sediment accumulations might destabilize the orogenic wedge and force architectural re-organization by outward propagation of the deformation front, while basin evacuation can induce out-of-sequence-thrusting to return the wedge to a critical taper. Structural reentrants along the Himalayan front are promising locations to study sediment delivery, storage, and sediment-evacuation mechanisms, as those areas commonly expose extensive transiently stored foreland-basin sediments. The Kangra re-entrant in the NW Sub-Himalaya hosts intermontane valley fills of Pleistocene age, eroded from the Dhauladhar Range. The sediments were unconformably deposited on top of Neogene foreland-basin sediments (i.e. the Siwaliks) in the hanging wall of the NW-SE striking Jwalamukhi Thrust. This major sediment accumulation phase appears to have preceded a phase of sediment evacuation in the course of episodic re-incision into the fill unit, which carved a series of fill-terrace levels. Angular unconformities, differential fluvial incision, tilted fluvial terraces, drainage re-organization, and steepened river segments in the hanging wall of the Jwalamukhi Thrust indicate post-depositional shortening and uplift in the Kangra re-entrant. From this evidence, we infer a primary importance of the Jwalamukhi Thrust in controlling the Quaternary sediment deposition in the Kangra re-entrant - however, we cannot exclude the influence of climate as the main trigger for sediment aggradation and subsequent excavation. However, knickpoints and steep river-channel gradients crossing other tectonic structures within the

  12. Origin and evolution of marginal basins of the NW Pacific: Diffuse-plate tectonic reconstructions

    CERN Document Server

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

    2012-01-01

    Formation of the gigantic linked dextral pull-apart basin system in the NW Pacific is due to NNE- to ENE-ward motion of east Eurasia. This mainly was a response to the Indo-Asia collision which started about 50 Ma ago. The displacement of east Eurasia can be estimated using three aspects: (1) the magnitude of pull-apart of the dextral pull-apart basin system, (2) paleomagnetic data from eastern Eurasia and the region around the Arctic, and (3) the shortening deficits in the Large Tibetan Plateau. All the three aspects indicate that there was a large amount (about 1200 km) of northward motion of the South China block and compatible movements of other blocks in eastern Eurasia during the rifting period of the basin system. Such large motion of the eastern Eurasia region contradicts any traditional rigid plate tectonic reconstruction, but agrees with the more recent concepts of non-rigidity of both continental and oceanic lithosphere over geological times. Based on these estimates, the method developed for resto...

  13. A review of the pressure temperature time evolution of the Limpopo Belt: Constraints for a tectonic model

    Science.gov (United States)

    Rigby, M.; Mouri, H.; Brandl, G.

    2008-02-01

    clockwise evolution. Granitoid magmatism is broadly contemporaneous in all three zones at ca. 2.7-2.5 suggesting a possible causal geodynamic link. P- T contrasts between and within the respective zones prevent, at present, the construction of a coherent and inter-related tectonic model that can account for all of the available evidence. Detailed and fully-integrated petrological and geochronological studies are required to produce reliable P- T- t paths that may resolve some of these pertinent issues.

  14. Paleozoic archipelagic tectonic evolution of Western Junggar, NW China: implications for continental growth of southern Altaids

    Science.gov (United States)

    Zhang, Jien; Xiao, Wenjiao; Han, Chunming; Ma, Chong; Song, Dongfang

    2013-04-01

    The Western Junggar, NW China, a dominant site for continental growth in Southern Altaids, bridges the Circum-Balkhash and Junggar belts and exposes ophiolite, igneous rocks and strata from Cambrian to Carboniferous. Recent updated data on structure, geochronology, geochemisty and paleomagnetism, integrated with previous data, present a newly Paleozoic spatial and temporal framework of Western Junggar. In Cambrian, the Western Junggar begins to birth at the Tangbale area to south, where occurs Ordovician blueschist and top-to-south vergence structures, indicating north-dipping subduction. This event triggers intra-arc extension to generate Ordovician island arc in the Hongguleleng-Xiemisitai area to north and seamount in the Mayile area, middle of Western Junggar. Until Silurian, a southeastward subduction begins in the extended back-arc basin to west of Mayile, occurring blueschist at the Barleik trench and the Nalunsuo magmatic arc, at the rear of which generates Devonian back-arc basin around the Durbut area. Meanwhile, a Silurian Xiemisitai magmatic arc has been developed at the northern part of Western Junggar, along which a northward subduction has emplaced the Tarbahatai ophiolite and generates the Carboniferous Sawur magmatic arc. At the middle part of Western Junggar, the coeval adakite and sanukitic dykes, charnockite, multiple properties of ophiolite and plutons, SSZ-like andesite, dacite and rhyolite and regional structures suggest that there develop double-subduction systems with ridge-trench interaction in Carboniferous. These features suggest that the Western Junggar experiences rollback, intra-oceanic extension and subduction polarity reversal/flip in back-arc basin settings. Furthermore, positive ɛNd(t) values and no huge movements of blocks suggest that the Western Junggar is amalgamated by juvenile elements with different orientations. Therefore, we conclude that the Western Junggar enlarges from an island arc to Paleozoic tectonic regime with

  15. Tectonic Evolution of the Patagonian Orocline: New Insights from a Paleomagnetic Study in Southernmost America

    Science.gov (United States)

    Roperch, P. J.; Poblete, F.; Arriagada, C.; Herve, F.; Ramirez de Arellano, C.

    2015-12-01

    One of the most noteworthy features of the Southern Andes is its bend, where the orogenic trend and main tectonic provinces change from Andean N-S oriented structures to W-E orientations in Tierra del Fuego. Few paleomagnetic studies have been carried out, and whether the bending is a primary curvature or a true orocline is still matter of controversy; also the mechanism of its formation. We have conducted a paleomagnetic study between 50°S to ~56°S, where 146 sites were drilled. Paleomagnetic data were obtained in 44 sites. Results in Early Cretaceous sediments and volcanics rocks confirm a remagnetization event during the mid-Cretaceous and record ~90° of counterclockwise rotation. Paleomagnetic results in mid-Cretaceous intrusives rocks record large counterclockwise rotation (>90°) while Late Cretaceous-Early Eocene intrusive rocks only record ~45° to ~30°. The paleomagnetic results reveal a systematic pattern of rotation—the Fueguian rotation pattern—suggesting that the curvature of Patagonia would have occurred in two stages: the first stage during the collapse and obduction of the Rocas Verdes basin in the mid-Cretaceous and a second stage between the Late Cretaceous and the Paleocene, concomitant with exhumation of Cordillera Darwin and propagation of the fold and thrust belt into the Magallanes foreland. Integrating this result in plate reconstructions shows the Antarctic Peninsula as a prolongation of Patagonia and would have acted as a non-rotational rigid block, facilitating the development of the Patagonia Bend. This land bridge could be a dispersal mechanism for fauna between Australia and South America and would have restricted deep ocean water circulation.

  16. Magmatic and tectonic evolution of the Ladakh Block from field studies

    Science.gov (United States)

    Raz, U.; Honegger, K.

    1989-04-01

    The Ladakh Block is in an intermediate position between the Indian plate in the south and the Karakorum-Tibetan plate in the north. To the west it is separated from the Kohistan Arc by the Nanga Parbat Syntaxis, to the east it is cut off from the Lhasa Block by the Gartok-Nubra Fault. Present data, together with previously published results, show, that the Ladakh Block consists of an island arc in the south and a calc-alkaline batholith in the north with remnants of a continental crust. Migmatitic gneisses and metasedimentary sequences, such as quartzites and metapelites, interbedded with basaltic volcanics and overlain by thick platform carbonates were found as evidence of a continental crust. Remnants of megafossils ( Megalodon and Lithiotis) within the high-grade metamorphic marbles indicate a probable age of Late Triassic to Early Jurassic. These sediments were intruded by a faintly layered hornblende-gabbro, which preceded the calc-alkaline magmatic episode. Gabbro and gabbronorites are found as roof pendants and large inclusions within diorites and granodiorites. The major part of the batholith consists of granodiorite and biotite-granite plutons, ranging from Late Cretaceous to Tertiary. Associated with the intrusives are volcanic rocks with trachyandesite to alkalibasalt and basalt-andesite to rhyolite compositions. Garnet-bearing leucogranites succeeded the emplacement of the major plutons. The magmatic stage ended, finally, by intense fracturing and injections of NE-SW striking andesitic dykes. The southernmost unit of the Ladakh Block is formed by oceanic crust with serpentinized peridotite and hornblende-gabbro and is covered by volcanics of an island-arc type (Dras volcanics). These units are intruded by gabbronorite, as well as Middle and Upper Cretaceous granodiorite and coarse-grained biotite-granite. In a plate tectonic view the Ladakh Block represents a transitional sector between the pure island arc of Kohistan in the west and the Andean type

  17. Northwest trending tectonic belt in the middle Yanshan Orogenic Belt of northeast Hebei Province, North China:Tectonic evolution and geochronology

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Changhou; WU; Ganguo; WANG; Genhou; ZHANG; Weijie

    2004-01-01

    The northwest trending tectonic belt in the middle part of the Mesozoic intraplate Yanshan Orogenic Belt, northeast Hebei Province, is composed of thrusts, extensional faults,strike-slip faults and syntectonic sedimentations as well. The northeastward basement-involved major thrusting deformation occurred between 174Ma and 168MaBP and was followed by an intrusion of the granitic plutonic rocks. As a part of the post-thrusting extensional deformations a northwest extending volcano-sedimentation system of Late Jurassic and Early Cretaceous formed in the southwest side of the belt. These volcano-sedimentary sequences are divided into Tuchengzi Formation, Zhangjiakou Formation, Yixian Formation and Jiufotang Formation respectively. They are characterized by southeastward migration as a result of the increasing down-dip slip displacement along the major extensional fault toward the southeast of the belt.The provenance area of the Jiufotang Formation north to it experienced southwestward thrusting during and after its later sedimentation. The thrusting in this stage resulted in the formation of an asymmetric footwall syncline with vergence to SW in the Jiufotang Formation in the NE side of the basin. Finally a dextral strike-slip deformation occurred along the NW tectonic belt. The striking tectono-geomorphological features and present seismic activities along this belt indicate that it has been being active since Cenozoic era and is still in the active state at present. This northwest extending tectonic belt was following the same direction and location as the existing fault systems within the basement as revealed by former geological and geophysical studies. So it is reasonable to infer the Mesozoic deformation along this belt to be a result of reactivation of the basement structures in a favorable tectonic stress field. The reactivation of basement structures might be taken as one of the mechanisms of intraplate deformation and orogeny.

  18. Cenozoic volcanism and lithospheric tectonic evolution in Qiangtang area, northern Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    CHI; Xiaoguo; LI; Cai; JIN; Wei

    2005-01-01

    and the stress relaxation in hinterland plateau caused by large-scale regional strike-slip tectonic pulsing activities in northern and eastern Qinghai-Tibet Plateau.

  19. Volcanic field elongation, vent distribution and tectonic evolution of continental rift: The Main Ethiopian Rift example

    Science.gov (United States)

    Mazzarini, Francesco; Le Corvec, Nicolas; Isola, Ilaria; Favalli, Massimiliano

    2015-04-01

    Magmatism and faulting operate in continental rifts and interact at a variety of scales, however their relationship is complex. The African rift, being the best example for both active continental rifting and magmatism, provides the ideal location to study the interplay between the two mechanisms. The Main Ethiopian Rift (MER), which connects the Afar depression in the north with the Turkana depression and Kenya Rift to the south, consists of two distinct systems of normal faults and its floor is scattered with volcanic fields formed by tens to several hundreds monogenetic, generally basaltic, small volcanoes and composite volcanoes and small calderas. The distribution of vents defines the overall shape of the volcanic field. Previous work has shown that the distribution of volcanic vents and the shape of a field are linked to its tectonic environment and its magmatic system. In order to distinguish the impact of each mechanism, we analyzed four volcanic fields located at the boundary between the central and northern MER, three of them (Debre Zeyit, Wonji and Kone) grew in the rift valley and one (Akaki) on the western rift shoulder. The elongation and shape of the fields were analyzed based on their vent distribution using the Principal Component Analysis (PCA), the Vent-to-Vent Distance (VVD), and the two dimensional symmetric Gaussian kernel density estimate methods. We extracted from these methods several parameters characterizing the spatial distribution of points (e.g., eccentricity (e), eigenvector index (evi), angular dispersion (Da)). These parameters allow to define at least three types of shape for volcanic fields: strong elongate (line and ellipse), bimodal/medium elongate (ellipse) and dispersed (circle) shapes. Applied to the natural example, these methods well differentiate each volcanic field. For example, the elongation of the field increases from shoulder to rift axis inversely to the angular dispersion. In addition, the results show that none of

  20. The tectonic evolution of Southeast Asia through accretionary and extensional episodes since the Cretaceous

    Science.gov (United States)

    Seton, M.; Zahirovic, S.; Müller, R.

    2012-12-01

    Although a number of tectonic reconstructions exist that document the development of the present-day complex assemblage of exotic terranes in Southeast Asia, very few describe the continuously evolving plate boundaries and the geodynamic driving forces in the region. We propose a plate motion model that attempts to reconcile evidence from both surface geology and the subsurface mantle structure, and implement continuously closing plate polygons using our open-source plate reconstruction software, GPlates, for the eastern Asian margin and eastern Tethyan domain since the Cretaceous. We link the change from a compressional to an extensional regime along eastern Asia in the Late Cretaceous as the likely opening of the Proto South China Sea in a back-arc setting to account for obducted ophiolite sections on Palawan that are Cretaceous in age, with a likely Miocene emplacement resulting from subduction of the Proto South China Sea crust. Such an interpretation is also consistent with the timing of accretionary episodes along northern Borneo and the upper mantle slab visible in P-wave seismic tomography models. The development of Sundaland is also intricately linked to the opening of the Proto South China Sea and the accretion of Gondwana-derived micro-continental blocks, including East Java and West Sulawesi, in the Cretaceous. Whether Sundaland behaved as a rigid cohesive block, or whether Borneo rotated and moved relative to Sundaland has been a matter of debate due to inconsistencies between paleomagnetic and structural data. Paleomagnetic results indicate significant rotations of Borneo that are accommodated by oroclinal bending without the need for bounding transform faults, which are not obvious in both seismic and potential field data. In the absence of preserved seafloor, we use geological evidence such as ophiolite emplacements, magmatic episodes, paleomagnetic constraints, structural reactivation and deformation as proxies to build a self-consistent plate

  1. Post-glacial landform evolution in the middle Satluj River valley, India: Implications towards understanding the climate tectonic interactions

    Science.gov (United States)

    Sharma, Shubhra; Bartarya, S. K.; Marh, B. S.

    2016-04-01

    Late Quaternary landform evolution in monsoon-dominated middle Satluj valley is reconstructed using the fragmentary records of fluvial terraces, alluvial fans, debris flows, paleo-flood deposits, and epigenetic gorges. Based on detailed field mapping, alluvial stratigraphy, sedimentology and optical chronology, two phases of fluvial aggradations are identified. The older aggradation event dated between ˜13 and 11 ka (early-Holocene), occurred in the pre-existing topography carved by multiple events of erosion and incision. Climatically, the event corresponds to the post-glacial strengthened Indian summer monsoon (ISM). The younger aggradation event dated between ˜5 and 0.4 ka (mid- to late-Holocene), was during the declining phase of ISM. The terrain witnessed high magnitude floods during transitional climate (˜6.5-7 ka). The fluvial sedimentation was punctuated by short-lived debris flows and alluvial fans during the LGM (weak ISM), early to mid-Holocene transition climate and mid- to late-Holocene declining ISM. Based on the terrace morphology, an event of relatively enhanced surface uplift is inferred after late Holocene. The present study suggests that post-glacial landforms in the middle Satluj valley owe their genesis to the interplay between the climate variability and local/regional tectonic interactions.

  2. Post-glacial landform evolution in the middle Satluj River valley, India: Implications towards understanding the climate tectonic interactions

    Indian Academy of Sciences (India)

    Shubhra Sharma; S K Bartarya; B S Marh

    2016-04-01

    Late Quaternary landform evolution in monsoon-dominated middle Satluj valley is reconstructed using the fragmentary records of fluvial terraces, alluvial fans, debris flows, paleo-flood deposits, and epigenetic gorges. Based on detailed field mapping, alluvial stratigraphy, sedimentology and optical chronology, two phases of fluvial aggradations are identified. The older aggradation event dated between ∼13 and 11 ka (early-Holocene), occurred in the pre-existing topography carved by multiple events of erosion and incision. Climatically, the event corresponds to the post-glacial strengthened Indian summer monsoon (ISM). The younger aggradation event dated between ∼5 and 0.4 ka (mid- to late-Holocene), was duringthe declining phase of ISM. The terrain witnessed high magnitude floods during transitional climate (∼6.5–7 ka). The fluvial sedimentation was punctuated by short-lived debris flows and alluvial fans during the LGM (weak ISM), early to mid-Holocene transition climate and mid- to late-Holocene decliningISM. Based on the terrace morphology, an event of relatively enhanced surface uplift is inferred after late Holocene. The present study suggests that post-glacial landforms in the middle Satluj valley owe their genesis to the interplay between the climate variability and local/regional tectonic interactions.

  3. Tectonic-stratigraphic evolution of Espirito Santo Basin - Brazil; Evolucao tectono-estratigrafica da Bacia do Espirito Santo

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Eric Zagotto; Fernandes, Flavio L.; Lobato, Gustavo; Ferreira Neto, Walter Dias [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE). Lab. de Modelagem de Bacias (LAB2M); Petersohn, Eliane [Agencia Nacional do Petroleo, Gas Natural e Biocombustiveis (ANP), Brasilia, DF (Brazil)

    2008-07-01

    This paper documents the analysis of seismic data of the Espirito Santo basin obtained during the project realized through partnership between COPPE/UFRJ/Lab2M with the Agencia Nacional do Petroleo, Gas Natural e Biocombustiveis (ANP) during 2006 and 2007. The major objective of the seismic data interpretation in the project was to define the main structural and stratigraphic features in order to build a sedimentation model and a tectonic-stratigraphic evolution model of the Espirito Santo basin. Thus, the sedimentary package has been divided into eight genetic units (UN), grouped into five third order stratigraphic sequences, namely: UN-B, represented by siliciclastics rocks of the rift stage and evaporitic sag-rift stage, deposited during the Aptian; UN-C, which represents the carbonatic rocks deposited in a marine environment, and siliciclastics rocks located in the proximal portions during the Albian; and UN-D, represented by sediments, composed mainly by pelites, deposited in between the Cenomanian and Recent, and includes the Eocene volcanic event, which one changed the sedimentation pattern of the basin. (author)

  4. Southern Brasilia Belt (SE Brazil): tectonic discontinuities, K-Ar data and evolution during the Neoproterozoic Brasiliano orogeny

    International Nuclear Information System (INIS)

    This paper focuses the tectonic evolution of the southern brasilia belt, with emphasis on the Furnas segment, along the 21 deg C S parallel. The uppermost structural unit (Passos Nappe - PN) comprises a highly deformed metasedimentary succession interpreted as a fragment of the Neoproterozoic passive margin of western Sao francisco craton. An inverted metamorphic gradient ranging from greensvhits to lower granulite facies of medium to high-pressure regime characterizes the PN as relict of a subduction zone. The External Domain display a complex imbrication of basement rocks (Archean Piumhi greenstones, a turbiditic gaywacke succession and a calc-alkaline granitoid suite) with undated siliciclast low-grade metasedimentary rocks. The Sao Francisco Craton (SFC) comprises pre-1.8 Ga basement rocks covered by anchimetamorphic Neoproterozoic carbonatic shallow marine platform deposits of the Bambui group. The Brasiliano thrust stacking generated a coarse clastic influx of molassic character on the foreland zone of Sao Francisco Craton, coeval with the exhumation of the External Domain thrust sheets. New K-Ar determinations on mineral separates are presented an interpreted among previous data. The SFC basement rocks display Paleo-to Meesoproterozoic cooling ages. The allochthonous units, in contrast, display K-Ar ages within the 560-675 Ma range. Brasiliano thrust stacking is therefore interpreted to have taken place onto a cold Sao Francisco craton foreland, in a thin-skinned style, as basement rocks were not heated enough to have their-K-ar systems reset during the allochthony. (author)

  5. Alpine dams

    Directory of Open Access Journals (Sweden)

    Alain Marnezy

    2009-03-01

    Full Text Available Les barrages-réservoirs de montagne ont été réalisés initialement dans les Alpes pour répondre à la demande d’énergie en période hivernale. Une certaine diversification des usages de l’eau s’est ensuite progressivement développée, en relation avec le développement touristique des collectivités locales. Aujourd’hui, la participation des ouvrages d’Électricité De France à la production de neige de culture représente une nouvelle étape. Dans les régions où les aménagements hydroélectriques sont nombreux, les besoins en eau pour la production de neige peuvent être résolus par prélèvements à partir des adductions EDF. Les gestionnaires de stations échappent ainsi aux inconvénients liés à la construction et à la gestion des « retenues collinaires ». Cette évolution, qui concerne déjà quelques régions alpines comme la haute Maurienne ou le Beaufortin, apparaît comme une forme renouvelée d’intégration territoriale de la ressource en eau.Mountain reservoirs were initially built in the Alps to meet energy needs in the winter. A certain diversification in the uses of water then gradually developed, related to tourism development in the local communities. Today, the use of facilities belonging to EDF (French Electricity Authority to provide water for winter resorts to make artificial snow represents a new phase. By taking water from EDF resources to supply snow-making equipment, resort managers are thus able to avoid the problems related to the construction and management of small headwater dams. This new orientation in the use of mountain water resources already affects a number of alpine regions such as the Upper Maurienne valley and Beaufortain massif and represents a renewed form of the territorial integration of water resources.

  6. Geologic Evolution of the eastern Panama Isthmus from biostratigraphic, tectonic and geophysical data

    Science.gov (United States)

    Barat, F.; Mercier de Lépinay, B.; Sosson, M.; Müller, C.

    2012-04-01

    identified a magmatic episode during the Lower Miocene in Mahé and Sapo Massifs. We present a new structural map of eastern Panama and five geological transects across the isthmus, summarizing the complex history. Our study documents: (1) a southwestward compression phase (in its present-day position) between Late Campanian and Middle Eocene, along the Pacific coast, in agreement with the subduction activity; (2) a Middle Eocene extension phase (Chucunaque-Tuira forearc basin formation); (3) a Middle Miocene compression phase, inverting some of the inherited normal faults and reactivating geological structures; (4) and a Plio-quaternary transpressive tectonic regime, evidenced by several left-lateral strike-slip faults with en echelon folds in the areas of Mahé Massif, Sanson Hills, Pirre Massif and Sapo Massif. These deformations are the result of the collision of Panama Choco block with the South America Plate.

  7. Mesozoic-Cenozoic tectonic evolution and its relation to sandstone-type uranium mineralization in northern Tarim area--Evidence from apatite fission track

    International Nuclear Information System (INIS)

    The apatite fission track dating and inversion result of geological thermal history of four rock specimens from Sawafuqi area and Talike area in northern Tarim Basin show that two areas uplifted at different ages. The apatite fission track ages of Sawafuqi range from 3.5 to 3.9 Ma, while the ages of Talike range from 53 to 59 Ma. The thermal history recorded by rock samples reveals that there are at least three prominent cooling phases since Late Cretaceous epoch. Detailed study was made on the division of uplifting stages during Mesozoic and Cenozoic tectonic evolution with the existing data in northern Tarim area. And new ideas on tectonic evolution and sandstone-type uranium mineralization have been put forward by combining with the sandstone-type uranium mineralization ages in this area.(authors)

  8. Tectonic evolution and its control over ore-formation of interlayer oxidized zone sandstone-type uranium deposit at southern margin of Turpan-Hami basin

    International Nuclear Information System (INIS)

    The tectonic evolution is divided into four stages at the southern margin of Turpan-Hami basin: (1) the development of Xinjiang oldland; (2) the sedimentation of passive-continental margin in the south of Junggar (Turpan-Hami) plate; (3) the accretion nappes of the force-arc margin and the development of foreland-like basin in the island (C2-T); (4) the development of sub-orogenic belt and the slope zone (J-Q). The third stage provided favourable material source and the emplacement space for interlayer oxidized zone-type uranium deposit. The fourth stage of the tectonic evolution was the time for the formation of intramountain basin and controlled the occurrence of the interlayer oxidized zone and sandstone-type uranium deposit

  9. Tectonic and petrologic evolution of the Western Mediterranean: the double polarity subduction model

    Science.gov (United States)

    Melchiorre, Massimiliano; Vergés, Jaume; Fernàndez, Manel; Torné, Montserrat; Casciello, Emilio

    2016-04-01

    The geochemical composition of the mantle beneath the Mediterranean area is extremely heterogeneous. This feature results in volcanic products whose geochemical features in some cases do not correspond to the geodynamic environment in which they are sampled and that is observed at present day. The subduction-related models that have been developed during the last decades to explain the evolution of the Western Mediterranean are mainly based on geologic and seismologic evidences, as well as petrography and age of exhumation of the metamorphic units that compose the inner parts of the different arcs. Except few cases, most of these models are poorly constrained from a petrologic point of view. Usually the volcanic activity that affected the Mediterranean area since Oligocene has been only used as a corollary, and not as a key constrain. This choice is strictly related to the great geochemical variability of the volcanic products erupted in the Western Mediterranean, due to events of long-term recycling affecting the mantle beneath the Mediterranean since the Variscan Orogeny, together with depletion episodes due to partial melting. We consider an evolutionary scenario for the Western Mediterranean based on a double polarity subduction model according to which two opposite slabs separated by a transform fault of the original Jurassic rift operated beneath the Western and Central Mediterranean. Our aim has been to reconstruct the evolution of the Western Mediterranean since the Oligocene considering the volcanic activity that affected this area since ~30 Ma and supporting the double polarity subduction model with the petrology of the erupted rocks.

  10. Permian to late Cenozoic evolution of northern Patagonia: Main tectonic events, magmatic activity, and depositional trends

    Science.gov (United States)

    Uliana, M. A.; Biddle, K. T.

    The late Paleozoic to late Cenozoic evolution of northern Patagonia was influenced significantly by events that occurred while the area was part of the South American sector of Gondwanaland. Late Paleozoic to Middle Triassic subduction along the edge of the supercontinent formed a broad convergent-margin system that is the underpinning of northern Patagonia. Deformation (Gondwanidian orogeny) associated with the subduction is recognized in both the forearc and the convergent backarc areas. Regional extension, accompanied by bimodal volcanism, began in the Late Triassic and led to the formation of a number of north-northwest trending rift basins in Patagonia, which generally followed the Gondwanidian basement grain. Continued extension in the Jurassic and Early Cretaceous led to the opening of the Rocas Verdes marginal basin in southern Chile and, ultimately, to the opening of the South Atlantic Ocean. Once oceanic crust began to form, faulting and volcanism declined in Patagonia. During the late Early Cretaceous to the Late Cretaceous, sags over the rift basins coalesced to form a broad backarc basin behind the volcanic arc to the west. These sags are suggestive of thermally driven subsidence. Subsidence of the evolving Atlantic margin allowed extensive marine transgressions to take place from the east. The stratigraphic record of northern Patagonia reflects these events. The upper Paleozoic to upper Mesozoic sedimentary sequences were deposited in basins directly associated with convergent activity along the margin of Gondwanaland or in rift basins created during its breakup. Even though the Tertiary evolution of Patagonia was dominated by events along the western margin of South America, the patterns of sediment transport, thickness, and general shoreline position were still influenced by the locations of the Mesozoic rifts formed during the breakup of Gondwanaland.

  11. Geology of the Blue Mountains region of Oregon, Idaho, and Washington; petrology and tectonic evolution of pre-Tertiary rocks of the Blue Mountains region

    Science.gov (United States)

    Vallier, T. L., (Edited By); Brooks, H.C.

    1995-01-01

    This Professional Paper contains 14 chapters on the Blue Mountains region of Oregon, Idaho, and Washington. The authors discuss petrology and tectonic evolution of an island arc that formed in the ancestral Pacific Ocean during the Permian to Cretaceous interval. The island arc was accreted to cratonal North America in the Early Cretaceous and thereby became one of the several exotic terranes in western North America.

  12. Gravity modeling constraints on the Gatun-Chagres Basin and tectonic evolution of north-central Panama

    Science.gov (United States)

    Mynhier, Kelci

    The Oligocene-Miocene collision between Panama and South America significantly influenced ocean currents, global climate, and species diversification. Intraplate deformation of the Panama Block also played an important role in the evolution of this tectonic system, but is not well understood. A high-resolution gravity survey, coupled with geologic observations, was conducted in north-central Panama to better constrain the processes responsible for the Isthmus' modern configuration. Approximately 110 gravity stations were collected from Colon to Nombre de Dios, Panama and merged with existing data. Subsequently, four 2.5-D gravity models were produced to constrain the geometry of the Gatun-Chagres Basin using different sedimentary densities (1.8, 2.0, and 2.2 g/cm 3) to produce a realistic range of basin thicknesses. Overall, models with an average basin density of 2.0 g/cm3 are most consistent with offshore seismic profiles and field evidence, suggesting basin thickness is ~3.0--3.5 km. Previous seismic reflection data and geochemical analyses of Miocene arc volcanic rocks delineate a zone of extension in the Panama Canal Region, and gravity analysis from this study supports this hypothesis. Field evidence of multiple NW-facing normal faults suggests that they separate the basin from uplifted arc basement rocks east of the Canal, resulting in a 60 mGal gravity gradient. Beneath the basin, gravity models indicate ~5--10 km of crustal thinning. 3-D reconstruction of the 2.5-D models show a northward thickening basin and two depocenters that correspond to the Rio Indio and Toro facies of the Chagres Formation. This analysis suggests two directional extension of the Gatun-Chagres Basin; an east-west direction corresponding to the initial formation of the basin, and a modern northwest-southeast direction. To the northeast, gravity modeling indicates that there is a ~150 m-thick, Cretaceous-Holocene sedimentary basin present from Portobelo to Nombre de Dios. Sedimentary

  13. Evolution of high-pressure mafic granulites and pelitic gneisses from NE Madagascar: Tectonic implications

    Science.gov (United States)

    Ishwar-Kumar, C.; Sajeev, K.; Windley, B. F.; Kusky, T. M.; Feng, P.; Ratheesh-Kumar, R. T.; Huang, Y.; Zhang, Y.; Jiang, X.; Razakamanana, T.; Yagi, K.; Itaya, T.

    2015-11-01

    The occurrence of high-pressure mafic-ultramafic bodies within major shear zones is one of the indicators of paleo-subduction. In mafic granulites of the Andriamena complex (north-eastern Madagascar) we document unusual textures including garnet-clinopyroxene-quartz coronas that formed after the breakdown of orthopyroxene-plagioclase-ilmenite. Textural evidence and isochemical phase diagram calculations in the Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2 system indicate a pressure-temperature (P-T) evolution from an isothermal (780 °C) pressure up to c. 24 kbar to decompression and cooling. Such a P-T trajectory is typically attained in a subduction zone setting where a gabbroic/ultramafic complex is subducted and later exhumed to the present crustal level during oceanic closure and final continental collision. The present results suggest that the presence of such deeply subducted rocks of the Andriamena complex is related to formation of the Betsimisaraka suture. LA-ICPMS U-Pb zircon dating of pelitic gneisses from the Betsimisaraka suture yields low Th/U ratios and protolith ages ranging from 2535 to 2625 Ma. A granitic gneiss from the Alaotra complex yields a zircon crystallization age of ca. 818 Ma and Th/U ratios vary from 1.08 to 2.09. K-Ar dating of muscovite and biotite from biotite-kyanite-sillimanite gneiss and garnet-biotite gneiss yields age of 486 ± 9 Ma and 459 ± 9 Ma respectively. We have estimated regional crustal thicknesses in NE Madagascar using a flexural inversion technique, which indicates the presence of an anomalously thick crust (c. 43 km) beneath the Antananarivo block. This result is consistent with the present concept that subduction beneath the Antananarivo block resulted in a more competent and thicker crust. The textural data, thermodynamic model, and geophysical evidence together provide a new insight to the subduction history, crustal thickening and evolution of the high-pressure Andriamena complex and its link to the terminal

  14. The Monte Orfano Conglomerate revisited: stratigraphic constraints on Cenozoic tectonic uplift of the Southern Alps (Lombardy, northern Italy)

    Science.gov (United States)

    Sciunnach, Dario; Scardia, Giancarlo; Tremolada, Fabrizio; Premoli Silva, Isabella

    2010-09-01

    The Monte Orfano Conglomerate (MOC), exposed in the foothills of the Southern Alps (northern Italy), is one of the few outcrops of sediments documenting the Cenozoic tectonic evolution of the Alpine retrowedge. Calcareous nannofossil biostratigraphy allowed us to constrain the upper part of the MOC, formerly attributed to the Early-Middle Miocene in the type-locality, to the earliest Miocene (Neogene part of the NN1 nannofossil zone). A likely latest Oligocene age is therefore suggested for the bulk of the underlying conglomerates, whose base is not exposed. Deposition of the MOC can be placed within the post-collisional tectonic uplift of the Alps, documented in the Lake Como area by the Como Conglomerate (CC) at the base of the Gonfolite Lombarda Group, and supports the correlation with Upper Oligocene clastic sediments cropping out further to the East, in the Lake Garda and in the Veneto-Friuli areas (“ molassa”). The remarkable difference in petrographic composition between the western (CC) and eastern (MOC) clastics deposited in the Alpine retro-foreland basin highlights the synchronous tectonic activity of two structural domains involving different crustal levels. Whilst the bulk of the CC, that straddles the Oligocene/Miocene boundary, records largely the tectonic exhumation of the Alpine axial chain crystalline complexes, the coeval MOC consists of detritus derived from the superficial crustal section (Triassic to Paleogene sedimentary rocks) of the Alpine retrowedge and constrains the onset of the post-collisional deformation phase of the Southern Alps as not younger than the Late Oligocene.

  15. Analysis of the influence of tectonics on the evolution valley network based on the SRTM DEM and the relationship of automatically extracted lineaments and the tectonic faults, Jemma River basin, Ethiopia

    Science.gov (United States)

    Kusák, Michal

    2016-04-01

    The Ethiopian Highland is good example of high plateau landscape formed by combination of tectonic uplift and episodic volcanism (Kazmin, 1975; Pik et al., 2003; Gani et al., 2009). Deeply incised gorges indicate active fluvial erosion which leads to instabilities of over-steepened slopes. In this study we focus on Jemma River basin which is a left tributary of Abay - Blue Nile to assess the influence of neotectonics on the evolution of its river and valley network. Tectonic lineaments, shape of valley networks, direction of river courses and intensity of fluvial erosion were compared in six subregions which were delineate beforehand by means of morphometric analysis. The influence of tectonics on the valley network is low in the older deep and wide canyons and in the and on the high plateau covered with Tertiary lava flows while younger upper part of the canyons it is high. Furthermore, the coincidence of the valley network with the tectonic lineaments differs in the subregions. The fluvial erosion along the main tectonic zones (NE-SW) direction made the way for backward erosion possible to reach far distant areas in E for the fluvial erosion. This tectonic zone also separates older areas in the W from the youngest landscape evolution subregions in the E, next to the Rift Valley. We studied the functions that can automatically extract lineaments in programs ArcGIS 10.1 and PCI Geomatica. The values of input parameters and their influence of the final shape and number of lineaments. A map of automated extracted lineaments was created and compared with 1) the tectonic faults by Geology Survey of Ethiopia (1996); and 2) the lineaments based on visual interpretation of by the author. The comparation of lineaments by automated visualization in GIS and visual interpretation of lineaments by the author proves that both sets of lineaments are in the same azimuth (NE-SW) - the same direction as the orientation of the rift. But it the mapping of lineaments by automated

  16. Tectonic-stratigraphic evolution of Cumuruxatiba Basin - Brazil; Evolucao tectono-estratigrafica da Bacia de Cumuruxatiba

    Energy Technology Data Exchange (ETDEWEB)

    Lobato, Gustavo; Fernandes, Flavio L.; Silva, Eric Zagotto; Ferreira Neto, Walter Dias [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE). Lab. de Modelagem Multidisciplinar de Bacias Sedimentares; Ribeiro, Juliana [Agencia Nacional do Petroleo, Gas Natural e Biocombustiveis (ANP), Brasilia, DF (Brazil)

    2008-07-01

    In recent years, the exploratory interest on Cumuruxatiba Basin has been inconstant, with modest discoveries of oil. Aiming to deepen the geological knowledge of the basin and in order to attract the interest of oil companies, the ANP (National Agency of Petroleum, Natural Gas and Biofuels) signed contract with COPPE/UFRJ for carrying out an analysis basin project. The project was developed by the Basin Analysis Multidisciplinary Modeling Laboratory (Lab2M/UFRJ) in the period 2006/2007, and was with the main objective outline the main structural and seismo-stratigraphic features of the basin, and in an integrated and multidisciplinary way, build a model of its sedimentation and tectono-stratigraphic evolution. This paper presents the results of the regional seismic mapping, aided by well and potential methods data. The stratigraphic succession the basin has been divided into genetic units (UN-B, UN-C e UN-D) corresponding to second order depositional sequences, they are: UN-B, corresponding by a rift and sag-rift siliciclastic deposits, plus the Aptian evaporitic deposits; UN-C, characterized by carbonatic deposits, and shelf related sediments; and UN-D, corresponding by a final transgressive (siliciclastic) - regressive (mix) cycle, between Cenomanian and actual days. (author)

  17. 2.6 Ga Gabbro-tonalite-trondhjemite Complex and 2.5 Ga Potassic Granite in Quruqtagh. Geochronology, Geochemistry and Their Implications on the Early Precambrian Tectonic Evolution of the Tarim Block, NW China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chuan-lin; LI Xian-hua; LI Zheng-xiang; YE Hai-min

    2008-01-01

    @@ Field observation, ages and geochemistry of the Neoarchaean intrusive complex in Quruqtagh in northern mar-gin of the Tarim Block, NW China, are reported to decipher the Neoarchaean tectonic evolution of the Tarim Block.

  18. Cenozoic tectonic evolution leading to the Choco-South America collision (Panama-Colombia), from seismic profiles interpretations

    Science.gov (United States)

    Barat, F.; Maurin, T.; Auxietre, J.; Mercier de Lépinay, B.; Salmon, P.; Sosson, M. M.

    2012-12-01

    The Choco Block is located in eastern Panama and western Colombia, at the western boundary of the Caribbean Plate (CP), and is mainly characterized by a Late Cretaceous-Paleogene volcanic arc overlying the Caribbean Large Igneous Province (CLIP). This block was accreted to South American plate (SAP) during Middle to Late Miocene. Geological, chronological and structural data are scarce in the Choco Block. Our study aims at reconstructing the evolution at a local scale, to provide new constraints to the regional scale tectonic processes that have occurred since the Paleogene. In that perspective, we have interpreted offshore seismic reflection profiles. This interpretation was supported by biostratigraphic data from two wells. We focused our studies in the Uraba Gulf area, a triple junction between the Choco Block, the SAP and the Caribbean oceanic plateau. This poorly understood zone offers rare observation of two accretionary wedges, the North Panama Deformed Belt (NPDB), and the Sinu Belt, located at the margins of the Choco Block and the SAP, respectively. They are the results of two opposite convergent zones, and collide along the active Uramita strike-slip Fault Zone (UFZ), a suture zone between the Choco Block and the SAP. This area may provide information on the ages of both accretionary wedges, on the tectonic processes responsible for the disappearance of the CP, and on the late formation of the Choco Block. Our results evidence a northward propagating deformation along the Choco Block, miocene or older in the South of the Uraba Gulf, pliocene in the North of the Uraba Gulf, and active along the northern margin of Panama. This deformation is the result of the progressive accretion of Choco Block along the SAP. At the Uraba triple junction, a thick sedimentary sequence was deposited since late Miocene. North verging progradations suggest that sediments came from the drainage of the western cordillera of Colombia by a Paleo-Sinu river and actual Atrato river

  19. The Carboniferous to Jurassic evolution of the pre-Alpine basement of Crete: Constraints from U-Pb and U-(Th)-Pb dating of orthogneiss, fission-track dating of zircon, structural and petrological data

    Czech Academy of Sciences Publication Activity Database

    Romano, S. S.; Brix, M. R.; Dörr, K.; Fiala, Jiří; Krenn, E.; Zulauf, G.

    2006-01-01

    Roč. 260, - (2006), s. 69-90. ISSN 0375-6440 Institutional research plan: CEZ:AV0Z30130516 Keywords : tectonic-evolution * Carboniferous * Jurassic * uranium-lead-dating * orthogneiss * fission-track-dating * zircon * structural-geology * petrology * metamorphism * high-temperature Subject RIV: DB - Geology ; Mineralogy

  20. The early Paleozoic sedimentary-tectonic evolution of the circum-Mangar areas, Tarim block, NW China: Constraints from integrated detrital records

    Science.gov (United States)

    Dong, Shunli; Li, Zhong; Jiang, Lei

    2016-07-01

    The Mangar depression, located in the eastern part of the Tarim basin, had deposited extremely-thick lower Paleozoic sediments, which yields great scientific value and hydrocarbon resource potential. Due to the lack of enough outcrop and core studies, many issues, e.g., early Paleozoic geographical evolution, basin nature and tectonic affinity, are still poorly understood. In this study, we selected circum-Mangar areas (i.e., the South Quruqtagh, Tabei and Tazhong areas), and carried out comprehensive detrital provenance analysis including detrital modal analysis, heavy mineral and trace element analysis, and detrital zircon U-Pb dating on the Middle-Upper Ordovician and Silurian sandstones. The results show that Upper Ordovician-Lower Silurian detrital provenances of the South Quruqtagh and Tabei areas were primarily derived from the intracontinental uplifts in Tarim. Meanwhile, Upper Silurian detrital provenances of the above two areas were mainly derived from the mix of intracontinental uplifts and continental-margin arcs. Dramatic Late Silurian provenance-change suggests the evident tectonic transition of the northern Tarim margin, which is the opening of the South Tianshan back-arc oceanic basin. Combining the previous studies, an integral redefinition model for the Mangar depression has been made. The evolution process of the Mangar depression could be divided into four stages: graben stage (late Neoproterozoic), transitional stage (Cambrian to Middle Ordovician), downwarp stage (Late Ordovician to Early Silurian) and extinction stage (Late Silurian). Hence, the Mangar depression evolved as an aulacogen. Significantly, the evolutional scenario of the Mangar aulacogen was consistent with that of the North Altyn Tagh and the North Qilian, suggesting that the Mangar aulacogen was involved mainly in the Proto-Tethys tectonic realm south to the Tarim block. However, the Late Silurian tectonic activity in the northern Tarim margin did produce massive detrital

  1. Detrital zircon age populations from the Moine Supergroup, Scotland, and their implications for tectonic evolution

    Science.gov (United States)

    Kindgren, Kelly; Steltenpohl, Mark; Strachan, Rob; Law, Rick; Cawood, Peter; Schwartz, Joshua

    2016-04-01

    absence of detrital grains younger than ~1050 Ma in the lower unit suggests evolution in the nature of rock units exposed in the source and/or a stratigraphic break between the upper and lower units of the succession. Furthermore, the age profile of the lower unit is consistent with, but not limited to, the interpretation that it correlates with the Torridon Group of the foreland, which has been argued to represent a foreland basin to the end Mesoproterozoic Grenville orogenic belt.

  2. Evolution of the Mesozoic Granites in the Xiong'ershan-Waifangshan Region, Western Henan Province, China, and Its Tectonic Implications

    Institute of Scientific and Technical Information of China (English)

    HAN Yigui; ZHANG Shihong; Franco PIRAJNO; ZHANG Yuanhou

    2007-01-01

    Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-Sr I-type granite emplaced in the early stage (~160 Ma), I-type granite in the middle stage (~130 Ma) and anorogenic A-type granite in the late stage (~115 Ma).Geochemical characteristics of the high-Ba-Sr I-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at ~115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between ~160 Ma and ~115 Ma. The genesis of the early- and middle-stage I-type granites could be linked to delamination of subducted lithosphere of the Qinling orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qinling -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios,which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.

  3. 月球的构造格架及其演化差异%Lunar Tectonic Framework and Its Evolution Inhomogeneity

    Institute of Scientific and Technical Information of China (English)

    刘建忠; 郭弟均; 籍进柱; 刘敬稳; 王庆龙

    2015-01-01

    根据以 GRAIL 重力场数据和 LOLA 地形数据计算的月壳厚度,将月球构造格架初步划分为三个构造单元:主要覆盖月球正面风暴洋区域的月海构造单元、主要覆盖月球背面高地的月陆构造单元以及主要位于南半球背面的南极艾肯盆地构造单元。结合最新的研究成果,对各构造单元上的重大地质事件包括岩浆事件、火山事件和撞击事件分别进行了简单的梳理,结果表明月球不同构造单元的演化事件具有明显的差异。%Based on the lunar crust thickness which is inversed from the GRAIL gravity data and LOLA topography data,the lunar tectonic framework can be preliminarily divided into three units:the mare tectonics locates in the region which mainly covers the nearside procellarum,the land tectonics dominately covering the highland in the farside and the south pole aitken basin tectonics.The major geological events including magma processing,volcanism and meteorite impacting have been studied simply,implying that the three kinds of evolution events vary clearly in different tectonic units.

  4. Discovery of deep-level foreland thrust-fold structures in Taihang Mt. and its implication for early tectonic evolution of North China

    Institute of Scientific and Technical Information of China (English)

    LI Jianghai; NIU Xianglong; CHEN Zheng; Timothy M KUSKY; Ali POLAT

    2005-01-01

    Delineation and correlation of Dragon Spring Shear Zone with its deep-level structures at foreland have been studied by field work. This paper reports our new findings of thrust-fold structures within Taihang Neoarchean basement, which include flat thrusts,large-scale recumbent folds, subhorizontal foliation patterns, etc. It reveals that early tectonic evolution of North China clearly involves the horizontal contraction on a large scale, comparable to those of foreland of classical collisional orogenic belts. The vertical variation of structural patterns with foreland fold-thrust belt from shallow to deep levels has been documented for Taihang Mt. by structural correlation,which is associated with tectonic transposition and imbrication of basement complex with supracrustal sequences in the Neoarchean.

  5. The interplay between tectonics, sediment dynamics and gateways evolution in the Danube system from the Pannonian Basin to the western Black Sea.

    Science.gov (United States)

    Matenco, Liviu; Munteanu, Ioan; ter Borgh, Marten; Stanica, Adrian; Tilita, Marius; Lericolais, Gilles; Dinu, Corneliu; Oaie, Gheorghe

    2016-02-01

    Understanding the natural evolution of a river-delta-sea system is important to develop a strong scientific basis for efficient integrated management plans. The distribution of sediment fluxes is linked with the natural connection between sediment source areas situated in uplifting mountain chains and deposition in plains, deltas and, ultimately, in the capturing oceans and seas. The Danube River-western Black Sea is one of the most active European systems in terms of sediment re-distribution that poses significant societal challenges. We aim to derive the tectonic and sedimentological background of human-induced changes in this system and discuss their interplay. This is obtained by analysing the tectonic and associated vertical movements, the evolution of relevant basins and the key events affecting sediment routing and deposition. The analysis of the main source and sink areas is focused in particular on the Miocene evolution of the Carpatho-Balkanides, Dinarides and their sedimentary basins including the western Black Sea. The vertical movements of mountains chains created the main moments of basin connectivity observed in the Danube system. Their timing and effects are observed in sediments deposited in the vicinity of gateways, such as the transition between the Pannonian/Transylvanian and Dacian basins and between the Dacian Basin and western Black Sea. The results demonstrate the importance of understanding threshold conditions driving rapid basins connectivity changes superposed over the longer time scale of tectonic-induced vertical movements associated with background erosion and sedimentation. The spatial and temporal scale of such processes is contrastingly different and challenging. The long-term patterns interact with recent or anthropogenic induced modifications in the natural system and may result in rapid changes at threshold conditions that can be quantified and predicted. Their understanding is critical because of frequent occurrence during

  6. Internal structure and current evolution of very small debris-covered glacier systems located in alpine permafrost environments

    Science.gov (United States)

    Bosson, Jean-Baptiste; Lambiel, Christophe

    2016-04-01

    This contribution explores the internal structure of very small debris-covered glacier systems located in permafrost environments and their current dynamical responses to short-term climatic variations. Three systems were investigated with electrical resistivity tomography and dGPS monitoring over a 3-year period. Five distinct sectors are highlighted in each system: firn and bare-ice glacier, debris-covered glacier, heavily debris-covered glacier of low activity, rock glacier and ice-free debris. Decimetric to metric movements, related to ice ablation, internal deformation and basal sliding affect the glacial zones, which are mainly active in summer. Conversely, surface lowering is close to zero (-0.04 m yr-1) in the rock glaciers. Here, a constant and slow internal deformation was observed (c. 0.2 m yr-1). Thus, these systems are affected by both direct and high magnitude responses and delayed and attenuated responses to climatic variations. This differential evolution appears mainly controlled by (1) the proportion of ice, debris and the presence of water in the ground, and (2) the thickness of the superficial debris layer.

  7. Flower evolution of alpine forbs in the open top chambers (OTCs) from the Qinghai-Tibet Plateau.

    Science.gov (United States)

    Zhang, Chan; Wang, Lin-Lin; Yang, Yong-Ping; Duan, Yuan-Wen

    2015-01-01

    Effects of global changes on biodiversity have been paid more and more attention world widely, and the open top chambers (OTCs) are the most common tools to study the effects of climatic warming on plant diversity. However, it remains unclear how flowers evolve under environmental changes, which could help us to understand the changes of plant diversity in the OTCs. We compared the insect diversity and pollen:ovule (P/O) ratio of eight outcrossing species with different life histories inside and outside the OTCs on the Qinghai-Tibet Plateau, to examine the effects induced by OTCs on the evolution of floral traits. In the OTCs, P/O ratio decreased in annuals, but increased in perennials, indicating an overall trend toward selfing in annuals. We found that the insect diversity differed significantly inside and outside the OTCS, with decreases of dipteran insects and bees. We concluded that changes of P/O ratio in the studied plant species might result from pollination failure, which might be the results of mismatch between flowering time and pollinator activities. We also suggested annuals might be in a more extinction risk than perennials in OTCs, if strong inbreeding depression occurs in these annual outcrossing plants. PMID:25998558

  8. The Ingul block of the Ukrainian Shield (the East European Craton): multiple stress changes during the Palaeoproteozoic tectonic evolution

    Science.gov (United States)

    Gintov, O. B.; Mychak, S. V.

    2012-04-01

    The Palaeoproterozoic Ingul block occupies the central part of the Ukrainian Shield in the Sarmatian crustal segment of the East European Craton. It is situated between two groups of Archaean blocks, the Middle Dniepr and Azov blocks in the east, and the Podolian and Bug blocks, in the southwest. In the Archaean and the earliest Palaeoproterozoic these western and eastern Archaean blocks had different structural evolutions and thus most probably were separated by an ocean. The Ingul block appears to have been formed during the closure of that ocean. Structurally, the Ingul block is a part of an up to 200 km wide zone of NS-trending dextral strike-slip faults. It extends far to the south and to the north and is also marked by the Kherson-Smolensk transregional fault zone. Archaean and Palaeoproterozoic rock complexes occur at the margins of the Ingul block whereas its middle part is completely Palaeoproterozoic. Its formation began during the 2.1-2.05 Ga collisional closing of the assumed ocean and the docking of the Archaean eastern and western continental blocks with each other. It was accompanied by dextral strike-slip faulting and strong compression. As a result, the Golovanevsk and Ingulets-Krivoi Rog suture zones were formed along the edges of the Eastern and Western Sarmatian microplates. Between 2.05 and 1.75 Ga, intense tectonothermal reworking and strike-slip faulting took place in the Ingul block. Several phases of deformation have been recognized. These are: • At 2.05-2.0 Ga - the Kherson phase of extension (azimuth/dip angle of the tension axis σ3 278/10, the compression axis σ1 8/00, dextral strike-slip faulting) accompanied by the intrusion of the Novo-Ukrainka monzogranitoids and some anatectic granitoids, and the formation of the Kherson-Smolensk fault zone, • At 2.0-1.8 Ga - two subsequent phases of compression: (1) the Kirovograd phase (σ1 49/00, σ3 319/00) and the development of a system of dextral strike-slip faults in the central part

  9. Tectonic and deformation history of the Gyeonggi Massif in and around the Hongcheon area, and its implications in the tectonic evolution of the North China Craton

    Science.gov (United States)

    Yengkhom, Kesorjit S.; Lee, Byung Choon; Oh, Chang Whan; Yi, Kee Wook; Kang, Ji Hoon

    2015-04-01

    The Gyeonggi Massif (GM) in South Korea is considered to be a part of the North China Craton. The Precambrian rocks of the GM in and around the Hongcheon area, South Korea, consist of the Yongduri Gneiss Complex (YGC), Euiam Group (EG) and Euiam Gneiss Complex (EGC). The YGC and EG composed mainly of partially migmatised metasedimentary rocks and the EGC is Paleoproterozoic intrusive rock that intruded the EG. At least three major folding (F1, F2 & F3), two-stage ductile shearing and three-stages of metamorphic events (M1, M2 & M3) occurred in the study area. The F1 folds are extremely drawn out, isoclinal, intrafolial folds and have Class 2 to Class 1C geometry. The F1 folds and regional S1 foliation in the YGC and EG are results of the E-W compression during the D1 deformation. Ductile shearing in the southern part of the EG is marked by the Palbongsan Shear Zone that indicates top-to-the SW sheared movement during syn to post-F1 folding. The F2 folds are open to tight, SW plunging and inclined folds, and have Class 1A to 1C geometry. The F2 folding and subsequent NNE thrusting along multiple ductile shear zones parallel to S2 planar fabrics are results of the D2 deformation due to N-S progressive shortening. The D3 deformation was coaxial with the D1 deformation, leading to the development of the F3 kink bands in the mylonite zones. The SHRIMP U-Pb detrital zircon ages from quartzite and banded gneisses in the EG indicate that the sedimentation in the Chunseong basins began after ca. 2094 Ma. The banded gneisses yield M1 metamorphic age of 1917-1925 Ma. However ca.1867-1883 Ma, M2 metamorphism previously reported from the YGC is absent or weakly preserved in the EG representing that the M2 metamorphism was not strong enough to form new zircon in the EG. The igneous zircons form augen gneisses in the EGC yield intrusion age of ca. 1867-1881 Ma and the geochemistries of the EGC gneisses show post-collision tectonic origin. The D1deformation observed in the YGC and

  10. Tectonic and sedimentary evolution of a Cretaceous continental arc-backarc system in the Korean peninsula: New view

    Science.gov (United States)

    Chough, S. K.; Sohn, Y. K.

    2010-08-01

    This paper focuses on the tectonic and sedimentary evolution of the Cretaceous volcanic rocks and nonmarine successions in the southeastern part of the Korean peninsula, which constitute an ancient continental arc system. The arc system (Gyeongsang Arc System), comprising an arc platform (Gyeongsang Volcanic Arc) and a backarc basin (Gyeongsang Backarc Basin), was a southwestward extension of the Japanese Arc formed by oblique northward subduction of the proto-Pacific (Izanagi) plate under the Asian continent. The backarc basin was initiated in the southeastern part of the Korean peninsula in the Early Cretaceous as a narrow NS-trending trough. The basin was bounded by a major fault in the northern part of the basin from which sediments largely emanated. Sediments were deposited in streamflow-dominated alluvial fans adjacent to the fault-bounded basin margin in the north and low-gradient fluvial systems of braided channels that extended southward and southeastward for tens of kilometers. Sediments were also derived from the western highland margin, draining Precambrian to Jurassic basement rocks. The initially narrow trough progressively expanded toward the east, resulting in eastward migration of depocenters that eventually generated a broad fluvio-lacustrine plain fringing the volcanic arc platform. The arc platform played an important role for the derivation of volcanogenic materials and accreted sediments into the backarc basin via extensive fluvial network. Pyroclastic density currents and landslides, which originated from the arc platform, also entered the basin. In addition, extrusion of basaltic volcanic rocks was continual within the basin during basin expansion. The resultant succession of mixed sedimentary and volcanogenic rocks is generally indicative of a temporal increase in volcanic activity in the arc platform and in subsidence rate of the basin. In the Late Cretaceous, andesitic to rhyolitic volcanism became climactic in the arc platform, producing

  11. Performative Tectonics

    DEFF Research Database (Denmark)

    Holst, Malene Kirstine; Mullins, Michael; Kirkegaard, Poul Henning

    This paper studies two digital generative tools in terms of Performative Tectonics. Performative Tectonics is a term developed in the paper, which links the contemporary development of digital tools to the tectonic tradition of architecture. Within the theoretical framework of this definition, the...

  12. Pressure-temperature-deformation-time of the ductile Alpine shearing in Corsica: From orogenic construction to collapse

    Science.gov (United States)

    Rossetti, Federico; Glodny, Johannes; Theye, Thomas; Maggi, Matteo

    2015-03-01

    Definition of the Tertiary tectono-metamorphic history of Alpine Corsica is a key task to decipher the space-time linkage between the Alpine and Apennine subduction systems in the Mediterranean region. Alpine Corsica exposes a nappe stack of oceanic- and continental-derived units, structurally juxtaposed onto the former European continental margin (Hercynian Corsica). Still uncertain is the timing of involvement of the continental-derived units in orogenic construction and shift to regional extension. This paper focuses on reconstruction of the pressure-temperature-deformation-time evolution of selected ductile shear zones activated during transition from the tectonic underplating to the extensional reworking stages. New Rb-Sr mineral age data, integrated with structural and thermobarometric investigations constrain the waning stages of the high-pressure (from blueschist to greenschist facies metamorphic conditions) top-to-the-W thrusting of the HP, oceanic-derived realm (Schistes Lustrés Complex) onto the Hercynian Corsica along the East Tenda Shear Zone in the early Oligocene (from ~ 32 to ~ 27 Ma). This early compressional evolution is overprinted by a major phase of retrogressive, syn-greenschist top-to-the-E extensional shearing in the Schistes Lustrés Complex with the last episode of deformation-related ductile recrystallization recorded during the early Miocene at ~ 20-21 Ma, in a continuum transition from ductile to brittle shearing. The same early Miocene Rb-Sr deformation ages are recovered from the ductile-to-brittle top-to-the-E reactivation domains within the East Tenda Shear Zone, documenting that transition from compression to extension in Alpine Corsica occurred during the late Oligocene-early Miocene time lapse. Implications of these data are discussed in the broader context of the Tertiary geodynamic evolution of the Central Mediterranean region.

  13. Early Paleozoic magmatic history of central Inner Mongolia, China: implications for the tectonic evolution of the Southeast Central Asian Orogenic Belt

    Science.gov (United States)

    Wu, Chen; Liu, Changfeng; Zhu, Yan; Zhou, Zhiguang; Jiang, Tian; Liu, Wencan; Li, Hongying; Wu, Chu; Ye, Baoying

    2016-07-01

    To provide insights into the Early Paleozoic tectonic evolution of the southern portion of the long-lived Central Asian Orogenic Belt, we have conducted major and trace element analyses and zircon U-Pb dating of granitoid samples from central Inner Mongolia. Our study area covers three pre-Mesozoic tectonic units from north to south: the Wenduermiao subduction-accretionary complex, the Bainaimiao magmatic belt, and the northern margin of the North China craton. Our new geochronological and geochemical data show the temporal and genetic relationships between the three tectonic units. Accordingly, we suggest that the Wenduermiao subduction-accretionary complex developed in the Middle Cambrian-Late Silurian (509-421 Ma), comprising of coeval oceanic crust, arc magmatism, and forearc deposits. The Bainaimiao continental arc was developed during the Late Cambrian to Early Silurian (501-437 Ma), which superposed on the basement with the affinity of the North China craton. The back-arc basin opened prior to Early Silurian and lasted to the Late Silurian, which is slightly younger than Bainaimiao island arc. The Wenduermiao Ocean, between the Wenduermiao subduction-accretionary complex and the Bainaimiao continental arc, existed in Early Paleozoic.

  14. Implications for the tectonic transition zone of active orogeny in Hoping drainage basin, by landscape evolution at the multi-temporal timescale

    Science.gov (United States)

    Chang, Q.; Chen, R. F.; Lin, W.; Hsieh, P. S.

    2015-12-01

    In an actively orogeny the landscape are transient state of disequilibrium in response to climatic and tectonic inputs. At the catchment scale, sensitivity of river systems plays an important role in landscape evolution. Hoping drainage basin is located at the tectonic transition zone in the north-eastern Taiwan, where the behavior of Philippine Sea plate switches from overriding above the east-dipping Eurasian Continental plate to northward subducting under the Ryukyu arc. However, extensive deep-seated landslides, debris flow, and numerous large alluvial terraces can be observed, suggesting strong surface processes in this watershed. This effect on regional climate fundamentally changed the landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. In this study we review the morphological evidence from multi-temporal timescale, including in-situ cosmogenic nuclides denudation rate and suspension load data, coupled with the analysis of the longitudinal profiles. The main goal of this study is to compare Holocene erosion rates with thermochronology and radiometric dating of river terraces to investigate the erosion history of Hoping area. The result shows that short-term erosion rate is around twice as large as the long-term denudation rate, which might due to the climate-driven erosion events such as typhoon-induced landslide. We've also mapped detail morphological features by using the high-resolution LiDAR image, which help us to identify not only the landslide but also tectonic features such as lineation, fault scarps, and fracture zones. The tectonic surface features and field investigation results show that the drainage basin is highly fractured, suggesting that even though the vertical tectonic activity rate is small, the horizontal shortening influenced by both southward opening of the back-arc Okinawa trough and the north-western collision in this area is significant. This might cause the reducing in rock strength

  15. Tectonic controls on the geomorphic evolution of alluvial fans in the Piedmont Zone of Ganga Plain, Uttarakhand, India

    Indian Academy of Sciences (India)

    Pradeep K Goswami; Charu C Pant; Shefali Pandey

    2009-06-01

    The Piedmont Zone is the least studied part of the Ganga Plain.The northern limit of the Piedmont Zone is defined by the Himalayan Frontal Thrust (HFT)along which the Himalaya is being thrust over the alluvium of the Ganga Plain.Interpretation of satellite imagery,Digital Terrain Models (DTMs)and field data has helped in the identification and mapping of various morpho-tectonic features in the densely forested and cultivated Piedmont Zone in the Kumaun region of the Uttarakhand state of India.The Piedmont Zone has formed as a result of coalescing alluvial fans,alluvial aprons and talus deposits.The fans have differential morphologies and aggradation processes within a common climatic zone and similar litho-tectonic setting of the catchment area. Morphotectonic analysis reveals that the fan morphologies and aggradation processes in the area are mainly controlled by the ongoing tectonic activities.Such activities along the HFT and transverse faults have controlled the accommodation space by causing differential subsidence of the basin,and aggradation processes by causing channel migration,channel incision and shifting of depocentres.The active tectonic movements have further modified the landscape of the area in the form of tilted alluvial fan,gravel ridges,terraces and uplifted gravels.

  16. Geochronology of the basement rocks, Amazonas Territory, Venezuela and the tectonic evolution of the western Guiana Shield

    International Nuclear Information System (INIS)

    The Amazonas Territory of Venezuela is a large area of Precambrian basement rocks overlain in some locales by the supracrustal sedimentary and volcanic rocks of the Roraima Formation. The basement rocks are medium to high grade gneisses with both igneous and sedimentary protoliths, plutonic rocks ranging in composition from granite to tonalite, and meta-volcanic rocks. Rb-Sr whole rock, and U-Pb isotopic analyses of zircons indicate a period of medium to high grade metamorphism and intrusion from 1860 to 1760 Ma. Post-tectonic plutonic activity continued to 1550 Ma. The volcanic rocks of the Roraima Formation in Venezuela give an age of 1746 Ma comparable to volcanic rocks of the Roraima Formation in other parts of the Guiana Shield. The ages and distribution of the basement rocks suggest the presence of a tectonic zone, approximately coincident with the Venezuelan-Colombian border, representing an active orogenic boundary between distinct tectonic provinces. The rocks to the northeast of this zone are part of the Trans-Amazonian of the Guiana Shield, while to the southwest and in adjacent Brazil and Colombia, new younger continental crust has been developed and cratonized. We suggest a model of collision and subduction followed by a chan0140n tectonic style to extensional-vertical to produce the basement rocks of the western Guiana Shield in the Amazonas Territory. (Auth.)

  17. Mesozoic Cenozoic tectonic evolution of the Zhuanghai area, Bohai-Bay Basin, east China: the application of balanced cross-sections

    Science.gov (United States)

    Wu, Shiguo; Yu, Zhaohua; Zhang, Rongqiang; Han, Wengong; Zou, Dongbo

    2005-06-01

    The technique of balancing cross-sections, an important method for studying the tectonic history of sedimentary basins, has many applications. It enables one to compile charts for petroleum exploration and development, and growth sections of ancient structures can be restored so that the structural growth history can be studied. In order to study tectonic evolution in the Zhuanghai area of the Bohai-Bay basin, we selected two seismic profiles and compiled two structural growth sections. Based on the two balanced cross-sections, the evolution can be divided into four phases: the Triassic-Middle Jurassic phase, Late Jurassic-Cretaceous phase, Palaeogene extension phase, and Late Palaeogene-to-present phase. The whole area was uplifted during the Triassic-Middle Jurassic phase because of intense extrusion stress related to the Indo-China movement. During the Late Jurassic and Early Cretaceous, intense extension occurred in east China, and the whole area rifted, leading to the deposition of a thick sedimentary sequence. In the Late Cretaceous, the area suffered uplift and compression associated with the sinistral strike slip of the Tanlu fault. In the Palaeogene, a rifting basin developed in the area. Finally, it became stable and was placed in its present position by dextral strike-slip motion. In addition, some problems associated with compiling balanced cross-sections are discussed.

  18. The fluid budget of a continental plate boundary fault: Quantification from the Alpine Fault, New Zealand

    Science.gov (United States)

    Menzies, Catriona D.; Teagle, Damon A. H.; Niedermann, Samuel; Cox, Simon C.; Craw, Dave; Zimmer, Martin; Cooper, Matthew J.; Erzinger, Jörg

    2016-07-01

    Fluids play a key role in modifying the chemical and physical properties of fault zones, which may prime them for repeated rupture by the generation of high pore fluid pressures and precipitation of commonly weak, secondary minerals. Fluid flow paths, sources and fluxes, and the permeability evolution of fault zones throughout their seismic cycles remain poorly constrained, despite their importance to understanding fault zone behaviour. Here we use geochemical tracers of fluid-rock exchange to determine budgets for meteoric, metamorphic and mantle fluids on a major compressional tectonic plate boundary. The Alpine Fault marks the transpressional Pacific-Australian plate boundary through South Island, New Zealand and appears to fail in regular (329 ± 68 yrs) large earthquakes (Mw ∼ 8) with the most recent event in 1717 AD. Significant convergent motion has formed the Southern Alps and elevated geothermal gradients in the hangingwall, which drive crustal fluid flow. Along the Alpine Fault the Alpine Schist of the Pacific Plate is thrust over radiogenic metasedimentary rocks on the Australian plate. The absence of highly radiogenic (87Sr/86Sr > 0.7200) strontium isotope ratios of hangingwall hot springs and hydrothermal minerals formed at a range of depths in the Alpine Fault damage zone indicates that the fluid flow is restricted to the hangingwall by a cross-fault fluid flow barrier throughout the seismogenic crust. Helium isotope ratios measured in hot springs near to the Alpine Fault (0.15-0.81 RA) indicate the fault is a crustal-scale feature that acts as a conduit for fluids from the mantle. Rock-exchanged oxygen, but meteoric water-like hydrogen isotope signatures of hydrothermal veins indicate that partially rock-exchanged meteoric fluids dominate down to the top of the brittle to ductile transition zone at ∼6 km. Geochemical tracer transport modelling suggests only ∼0.02 to 0.05% of total rainfall west of the Main Divide penetrates to depth, yet this

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

    Science.gov (United States)

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

    2015-04-01

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

  20. Unraveling the geodynamic evolution and tectonic history of the Guatemala Suture Zone: a world-class natural laboratory

    Science.gov (United States)

    Flores, K. E.; Brocard, G. Y.; Harlow, G. E.

    2013-12-01

    The Guatemala Suture Zone (GSZ) is the fault-bound region in central Guatemala that contains the present North American-Caribbean plate boundary. It is bounded by the Maya Block to the north and by the Chortís Block to the south. This major composite geotectonic unit contains a variety of ophiolites, serpentinite mélanges, and metavolcano-sedimentary sequences along with high-grade schist, gneisses, low-grade metasediments and metagranites thrusted north and south of the active Motagua fault system (MFS). This modern plate boundary has accommodated at least ~1100 km of left-lateral strike-slip motion over the Cenozoic and brings into contact the geological provinces described above. Classically, the GSZ has been interpreted as the result of a single progressive collision of a Chortís Block-related island arc with the passive margin of the Maya Block. This model was based on geochemical signatures of basaltic rocks in oceanic crust sequences both north and south of the MFS. However, results from our research challenge this single collision hypothesis. Oceanic and continental high-pressure-low-temperature (HP-LT) rocks astride the MFS have recorded multiple tectonic events revealed by their multiple metamorphic ages (Sm-Nd, U-Pb and Ar-Ar) and distinct PT paths. These tectonic events differ in age north and south of the MFS. Moreover, the continental and oceanic sequences across the MFS are geochemically and stratigraphically distinct, suggesting different tectonic origins. The southern margin of the Maya Block and the northern section of the GSZ can be clearly interpreted as a Cretaceous-Paleocene flexural passive margin tectonically overridden by ultramafic rocks and a Cretaceous island arc sequence. In contrast, the southern section of the GSZ is composed of a Carboniferous-Jurassic active margin tectonically imbricated with ultramafic rocks and a circum-Pacific Jurassic MORB and IAT metavolcano-sedimentary sequence. Thus, based on these results, we identify at

  1. Tectonic controls on the geomorphic evolution of alluvial fans in the Piedmont Zone of Ganga Plain, Uttarakhand, India

    Science.gov (United States)

    Goswami, Pradeep K.; Pant, Charu C.; Pandey, Shefali

    2009-06-01

    The Piedmont Zone is the least studied part of the Ganga Plain. The northern limit of the Piedmont Zone is defined by the Himalayan Frontal Thrust (HFT) along which the Himalaya is being thrust over the alluvium of the Ganga Plain. Interpretation of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in the identification and mapping of various morphotectonic features in the densely forested and cultivated Piedmont Zone in the Kumaun region of the Uttarakhand state of India. The Piedmont Zone has formed as a result of coalescing alluvial fans, alluvial aprons and talus deposits. The fans have differential morphologies and aggradation processes within a common climatic zone and similar litho-tectonic setting of the catchment area. Morphotectonic analysis reveals that the fan morphologies and aggradation processes in the area are mainly controlled by the ongoing tectonic activities. Such activities along the HFT and transverse faults have controlled the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration, channel incision and shifting of depocentres. The active tectonic movements have further modified the landscape of the area in the form of tilted alluvial fan, gravel ridges, terraces and uplifted gravels.

  2. Triassic to recent tectonic evolution of a crestal collapse graben above a salt-cored anticline in the Glückstadt Graben/North German Basin

    Science.gov (United States)

    Al Hseinat, M.; Hübscher, C.; Lang, J.; Lüdmann, T.; Ott, I.; Polom, U.

    2016-06-01

    In this study we investigate faulting above a salt wall in the Glückstadt Graben/North German Basin. Two supra-salt faults are mapped from coast to coast over a distance of 6-9 km based on offshore and onshore seismic data. These faults form a ca. 2 km wide crestal collapse graben and pierce the seafloor. Salt wall evolution started in the early Late Triassic to Early Jurassic due to regional extension and resulting sub-salt faulting. The salt wall was eroded following exposure to costal and sub-aerial erosion by the regional Mid-Late Jurassic to Early Cretaceous uplift. Late Cretaceous to Early Paleogene compressional tectonics reactivated the vertical salt movement and shortened the salt wall, creating a salt-cored anticline with the crestal collapse graben above. The supra-salt faults were reactivated between the Late Eocene and Middle Miocene when the principal horizontal stress orientation changed from a NE-SW to a NW-SE, the present-day orientation. Stratigraphic data indicate that these faults moved mainly in the Cenozoic. Several observations strongly suggest that the faults continued developing during the Pleistocene until today: (i) the Pleistocene Unconformity is concave upwards and cut by faults; (ii) growth strata within the marine Holocene deposits above the graben imply recent tectonic movements; (iii) onshore high-resolution P-wave vibroseis data of the south-eastern Eckernförde Bay suggest about 10 m of faulted Holocene strata; and (iv) marine seismic data show the faults piercing the seafloor. We suggest that the recent salt tectonics and upward propagation of supra-salt faults resulted from differential ice-sheet loading. That effect on the salt wall stopped once ice grew over the whole structure, at which time the wall subsided because of ice loading. The salt wall and faults were reactivated again once the ice front retreated so that the ice loaded only one side of the structure.

  3. Analysis of the geological structure and tectonic evolution of Xingning-Jinghai sag in deep water area, northern South China Sea

    Science.gov (United States)

    Han, Xiaoying; Ren, Jianye; Lin, Zi; Yang, Linlong

    2015-04-01

    Recent years, oil and gas exploration of the Pearl River Mouth Basin in the northern margin of South China Sea continuously achieved historic breakthroughs. The Xingning-Jinghai sag, which is located in southeast of the Pearl River Mouth Basin, is a deep-water sag with a great exploration potential. Its tectonic evolution is extremely complex. It experienced Mesozoic subduction to Cenozoic intra-continental rifting background, and finally evolved into a deep-water sag of the northern continental margin of South China Sea. The geological characteristics and the tectonic evolution of Xingning-Jinghai sag was closely related to the process of formation and evolution of the passive continental margin of the northern South China Sea. It is confirmed by many geophysical data that compared with adjacent Chaoshan depression, the crustal thickness of Xingning-Jinghai sag was rapidly thinning, and it developed detachment faults with later magmatic intrusion. The development of detachment faults have dynamic significance for the spreading of the South China Sea. Based on the seismic geological interpretation of 2D seismic data in the study area, the characteristics of detachment fault and supra-detachment basin have been proposed in this study. The characteristics of the detachment fault are low angle and high ratio between heave and throw. The geometry of the detachment fault is a typical lisric shape, with the dip of fault decreasing generally from the seismic profile. The detachment basin where sediments are not deposited over a tilting hanging-wall block but onto a tectonically exhumed footwall which is different from the typical half graben basin. Seismic profiles indicate two different structural styles in the east and west part of Xingning-Jinghai sag. In the west of the sag, there developed two large detachment faults, which control their detachment basin systems and the typical H block, and the two detachment faults are dipping landward and seaward, respectively. In

  4. The Pinjaur dun (intermontane longitudinal valley) and associated active mountain fronts, NW Himalaya: Tectonic geomorphology and morphotectonic evolution

    Science.gov (United States)

    Singh, Vimal; Tandon, S. K.

    2008-12-01

    The Himalayan orogenic belt, formed as a result of collision tectonic processes, shows abundant evidence of neotectonic activity, active tectonics, and the occurrence of historical earthquakes. Its frontal deformation zone is characterized, in some segments, by intermontane longitudinal valleys (duns). Such frontal segments of the Himalaya are marked by the occurrence of multiple mountain fronts. In one such segment of the foothills of the NW Himalaya, the Pinjaur dun is developed and marked by three mountain fronts: MF1A and MF1B associated with the southernmost Himalayan Frontal Thrust (HFT), MF2 associated with the Sirsa fault, and MF3 associated with the Barsar thrust along the southern margin of the relatively higher main part of the sub-Himalaya. Geomorphic responses to the tectonic activity of these and related structural features have been analyzed through the use of geomorphic indices, drainage density, stream longitudinal profiles, drainage anomalies, and hypsometric analysis. Also, fault and fold growth and their expression on landform development was studied using a combination of surface profiles and field observations. The values of valley floor width to height ratio ( Vf) for valleys associated with MF1 ranged between 0.07 and 0.74, and for valleys associated with MF2 ranged from 1.02-5.12. Vf for the four major valleys associated with MF1B ranged from 1.1-1.7. The asymmetry factor for 26 drainage basins related to MF1A indicate these have developed under the influence of a transverse structure. These results taken together with those obtained from the Hack profiles and SL index values, hypsometry, drainage density, and drainage anomalies suggest that the faults associated with the mountain fronts and related structures are active. Active tectonics and neotectonic activity have led to the formation of four surfaces in the Pinjaur dun. In addition, an important drainage divide separating the Sirsa and Jhajara drainage networks also developed in the

  5. Miocene Tectonic Evolution from Dextral-Slip Thrusting to Extension in the Nyainqêntanglha Region of the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    WU Zhenhan; Patrick J. BAROSH; ZHAO Xun; WU Zhonghai; HU Daogong; LIU Qisheng

    2007-01-01

    Dextral-slip in the Nyainqêntanglha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The east-west dextral-slip Gangdise fault system merges eastward into the north into the dextral-slip North Damxung shear zone and Jiali faults. These faults were took shape system in 18.3-11.0 Ma as the western block drove under the eastern one. The dextral-slip movement ended at ~11 Ma and the batholith rose, as marked by gravitational shearing at 8.6-8.3 Ma, and a new fault system developed. Northwest-trending dextral-slip faults formed to the northwest of the raisen batholith, whereas the northeast-trending South Damxung thrust faults with some sinistral-slip formed to the southeast. The latter are replaced farther to the east by the west-northwest-trending Miocene deposits preserved was followed by a regional uplift and the initiation of a system of generally north-south grabens in the Late Miocene at ~6.5 Ma. The regional uplift of the southern Tibetan Plateau thus appears to have occurred between 8.3 Ma and 6.5 Ma. The Gulu, Damxungcontrolled by the earlier northeast-trending faults. These grabens dominate the subsequent tectonic movement and are still very active as northwest-trending dextral-slip faults northwest of the mountains. The Miocene is a time of great tectonic change that ushered in the modern tectonic regime.

  6. Holocene Asian monsoon evolution revealed by a pollen record from an alpine lake on the southeastern margin of the Qinghai-Tibetan Plateau, China

    Science.gov (United States)

    Zhang, Enlou; Wang, Yongbo; Sun, Weiwei; Shen, Ji

    2016-02-01

    We present the results of pollen analyses from a 1105 cm long sediment core from Wuxu Lake in southwestern China, which depict the variations of the East Asian winter monsoon (EAWM) and the Indian summer monsoon (ISM) during the last 12.3 ka. During the period of 12.3 to 11.3 cal ka BP, the dominance of Betula forest and open alpine shrub and meadow around Wuxu Lake indicates a climate with relatively cold winters and dry summers, corresponding to the Younger Dryas event. Between 11.3 and 10.4 cal ka BP, further expansion of Betula forest and the retreat of alpine shrubs and meadows reflect a greater seasonality with cold winters and gradually increasing summer precipitation. From 10.4 to 4.9 cal ka BP, the dense forest understory, together with the gradual decrease in Betula forest and increase in Tsuga forest, suggest that the winters became warmer and summer precipitation was at a maximum, corresponding to the Holocene climatic optimum. Between 4.9 and 2.6 cal ka BP, Tsuga forest and alpine shrubs and meadows expanded significantly, reflecting relatively warm winters and decreased summer precipitation. Since 2.6 cal ka BP, reforestation around Wuxu Lake indicates a renewed humid period in the late Holocene; however, the vegetation in the catchment may also have been affected by grazing activity during this period. The results of our study are generally consistent with previous findings; however, the timing and duration of the Holocene climatic optimum from different records are inconsistent, reflecting real contrast in local rainfall response to the ISM. Overall, the EAWM is broadly in-phase with the ISM on the orbital timescale, and both monsoons exhibit a trend of decreasing strength from the early to late Holocene, reflecting the interplay of solar insolation receipt between the winter and summer seasons and El Niño-Southern Oscillation strength in the tropical Pacific.

  7. Tectonic evolution of 200 km of Mid-Atlantic Ridge over 10 million years: Interplay of volcanism and faulting

    Science.gov (United States)

    Cann, Johnson R.; Smith, Deborah K.; Escartin, Javier; Schouten, Hans

    2015-07-01

    We reconstruct the history of the mode of accretion of an area of the Mid-Atlantic Ridge south of the Kane fracture zone using bathymetric morphology. The area includes 200 km of the spreading axis and reaches to 10 Ma on either side. We distinguish three tectonic styles: (1) volcanic construction with eruption and intrusion of magma coupled with minor faulting, (2) extended terrain with abundant large-offset faults, (3) detachment faulting marked by extension on single long-lived faults. Over 40% of the seafloor is made of extended terrain and detachment faults. The area includes products of seven spreading segments. The spreading axis has had detachment faulting or extended terrain on one or both sides for 70% of the last 10 Ma. In some parts of the area, regions of detachment faulting and extended terrain lie close to segment boundaries. Regions of detachment faulting initiated at 10 Ma close to the adjacent fracture zones to the north and south, and then expanded away from them. We discuss the complex evidence from gravity, seismic surveys, and bathymetry for the role of magma supply in generating tectonic style. Overall, we conclude that input of magma at the spreading axis has a general control on the development of detachment faulting, but the relationship is not strong. Other factors may include a positive feedback that stabilizes detachment faulting at the expense of volcanic extension, perhaps through the lubrication of active detachment faults by the formation of low friction materials (talc, serpentine) on detachment fault surfaces.

  8. Geochemical evolution of Cenozoic-Cretaceous magmatism and its relation to tectonic setting, southwestern Idaho, U.S.A

    International Nuclear Information System (INIS)

    Magmatism in the western United States spanned a change in tectonic setting from Mesozoic and early Tertiary plate convergence to middle and late Tertiary crustal extension. This paper presents new major element, trace element, and isotopic (Sr, Nd, Pb) data on a diverse suite of Cretaceous to Neogene igneous rocks from the Owyhee area of southwestern Idaho to evaluate possible relationships between the evolving tectonic regime and temporal changes in igneous activity. The oldest studied rocks are Cretaceous granitic intrusives that probably formed by large-scale mixing of Precambrian crust with subduction-related magmas. Silicic Eocene tuffs are also rich in crustal components, but have isotopic compositions unlike the Cretaceous intrusives. These data require at least two crustal sources that may correspond to domains of significantly different age (Archean vs. Proterozoic). The oldest mafic lavas in the study area are Oligocene andesites and basalts compositionally similar to subduction-related magmas derived from asthenospheric mantle and erupted through thick continental crust. Direct crustal involvement during oligocene time was limited to minor interaction with the mafic magmas. Miocene activity produced bimodal basalt-rhyolite suites and minor volumes of hybrid lavas. Compositions of Miocene basalts demonstrate the decline of subduction-related processes, and increased involvement of subcontinental lithospheric mantle as a magma source. Crustally-derived Miocene rhyolites have isotopic compositions similar to those of the Cretaceous granitic rocks but trace element abundances more typical of within-plate magmas. (orig./WB)

  9. Pre-Alpine evolution of a segment of the North-Gondwanan margin: Geochronological and geochemical evidence from the central Serbo-Macedonian Massif

    OpenAIRE

    Antić, Milorad; Peytcheva, Irena; Von Quadt, Albrecht; Kounov, Alexandre; Trivić, Branislav; Serafimovski, Todor; Tasev, Goran; GERDJIKOV, IANKO; Wetzel, Andreas

    2016-01-01

    The Serbo-Macedonian Massif (SMM) represents a composite crystalline belt within the Eastern European Alpine orogen, outcropping from the Pannonian basin in the north, to the Aegean Sea in the south. The central parts of the massif (i.e. southeastern Serbia, southwestern Bulgaria, eastern Macedonia) consist of the medium- to high-grade Lower Complex, and the low-grade Vlasina Unit. New results of U–Pb LA-ICP-MS analyses, coupled with geochemical analyses of Hf isotopes on magmatic and d...

  10. Rubidium-strontium geochronology and plate-tectonic evolution of the southern part of the Arabian Shield

    Science.gov (United States)

    Fleck, Robert J.; Greenwood, W.R.; Hadley, D.G.; Anderson, R.E.; Schmidt, D.L.

    1980-01-01

    Rubidium-strontium studies of Precambrian volcanic and plutonic rocks of the Arabian Shield document an early development of the Arabian craton between 900 and 680 m.y. (million years) ago. Geologic studies indicate an island-arc environment characterized by andesitic (dioritic) magmas, volcaniclastic sedimentation, rapid deposition, and contemporaneous deformation along north or northwest-trending axes. Magmatic trends show consistent variation in both composition and geographic location as a function of age. The oldest units belong to an assemblage of basaltic strata exposed in western Saudi Arabia that yield an age of 1165:!:110 m.y. The oldest andesitic strata studied yield an age of 912:!:76 m.y. The earliest plutonic units are diorite to trondhjemite batholiths that range from 800 to 9,00 m.y. in age and ,occur along the western and southern parts of Saudi Arabia. Younger plutonic units, 680 to 750 m.y. in age, range from quartz diorite to granodiodte and become more abundant in the central and northeastern parts of the Arabian Shield. Initial 'Sr/ 86 Sr ratios for both dioritic groups range from 0.7023 to 0.7030 and average 0.7027. The absence of sialic detritus in sedimentary units and the evidence for an island-arc environment suggest the early development of the Arabian craton at a convergent plate margin between plates of oceanic lithosphere. Active subduction apparently extended from at least 900 m.y. to about 680 m.y. Subsequent to this subduction-related magmatism and tectonism, called the Hijaz tectonic cycle, the Arabian craton was sutured to the late Precambrian African plate in a collisional event. This period of orogeny, represented in Arabia and eastern Africa by the Mozambiquian or Pan-African event, extended from some time before 650 m.y. to at least 540 m.y. and perhaps 520 m.y. B.P. Although the tectonic processes of subduction and continental collision during the 900+ to 500-m.y. period require similar directions of plate convergence, the

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

    International Nuclear Information System (INIS)

    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)

  12. The impact of salt tectonics on supra-salt (Lago Mare?) deposits and on the structural evolution of the Cyprus-Eratosthenes collision zone

    Science.gov (United States)

    Reiche, Sönke; Hübscher, Christian; Ehrhardt, Axel

    2015-04-01

    Averagely 1.5 km thick Messinian evaporites laterally continue from the Levant Basin, easternmost Mediterranean Sea, into the collision zone between Cyprus and Eratosthenes Seamount where incipient continent-continent-collision is believed to occur. In this study, the impact of Messinian evaporites on the structural evolution of the collision zone is investigated for the first time based on a comprehensive set of seismic reflection profiles. Results show that the collision zone may be subdivided into an eastern and a western domain. In the eastern part, bordered by Eratosthenes Seamount and the Hecataeus Rise, compressionally thickened autochthonous salt is observed. Sub- and supra-salt deposits within this area appear to be in the stage of active accretion. Further west, between Cyprus and Eratosthenes Seamount strongly deformed allochthonous salt has evidently started to advance across sediments of post-Messinian age. In this domain, previously active sediment accretion at the Cyprus margin has now become inactive and shortening is largely accommodated at the leading edge of the allochthonous salt sheet. Such observations bear important implications for the structural interrelation between salt tectonics and the evolution of a young collision zone. On top of highly deformed mobile Messinian evaporites, up to 700 m thick late Messinian supra-salt deposits are mapped within the western part of the Cyprus - Eratosthenes collision zone. Their uppermost 200 m were drilled in the course of ODP Leg 160 (Site 968) and interpreted as Lago Mare sediments, deposited during the final stage of the Messinian Salinity Crisis (Robertson, 1998). These sediments occupy small sub-basins flanked by salt diapirs, indicating a salt-tectonic control on late Messinian sediment deposition. Distribution of these sediments may have further been controlled by sea-level, inferred from rapid eastward thinning and pinchout of Messinian supra-salt deposits towards the Levant Basin

  13. Tectonic and paleoenvironmental evolution of Mesozoic sedimentary basins along the Andean foothills of Argentina (32°-54°S)

    Science.gov (United States)

    Franzese, Juan; Spalletti, Luis; Pérez, Irene Gómez; Macdonald, David

    2003-05-01

    Chronoenvironmental and tectonic charts are presented for Mesozoic basins located along the Andean foothills of the South American plate. On the basis of the main tectonic events, pre-Andean basins, break-up-related basins, extensional back-arc basins, and Andean foreland basins are recognized. The pre-Andean basins were formed by continental extension and strike-slip movement before the development of the Mesozoic-Cenozoic Andean magmatic arc. Upper Permian to Middle Triassic extension along Palaeozoic terrane sutures resulted in rifting, bimodal magmatism (Choiyoi group), and continental deposition (Cuyo basin). From the Late Triassic to the Early Jurassic, continental extension related to the collapse of the Gondwana orogen initiated a series of long, narrow half-grabens that filled with continental volcaniclastic deposits. These depocenters were later integrated into the Neuquén basin. Coeval development of the shallow marine Pampa de Agnia basin (42-44°S) is related to short-lived extension, probably driven by dextral displacement along major strike-slip faults (e.g. the Gastre fault system). Widespread extension related to the Gondwana breakup (180-165 Ma) and the opening of the Weddell Sea reached the western margin of the South American plate. As a result, wide areas of Patagonia were affected by intraplate volcanism (Chon Aike province), and early rifting occurred in the Magallanes basin. The Andean magmatic arc was almost fully developed by Late Jurassic times. A transgressive stage with starvation and anoxia characterized the Neuquén basin. In western Patagonia, back-arc and intra-arc extension produced the opening of several grabens associated with explosive volcanism and lava flows (e.g. Rı´o Mayo, El Quemado). To the south, a deep marginal basin floored by oceanic crust (Rocas Verdes) developed along the back-arc axis. In mid-to late Cretaceous times, Andean compressional tectonics related to South Atlantic spreading caused the inversion of

  14. Integration of natural data within a numerical model of ablative subduction: A possible interpretation for the Alpine dynamics of the Austroalpine crust

    CERN Document Server

    Roda, Manuel; Marotta, Anna Maria

    2012-01-01

    A numerical modelling approach is used to validate the physical and ge- ological reliability of the ablative subduction mechanism during Alpine con- vergence in order to interpret the tectonic and metamorphic evolution of an inner portion of the Alpine belt: the Austroalpine Domain. The model pre- dictions and the natural data for the Austroalpine of the Western Alps agree very well in terms of P-T peak conditions, relative chronology of peak and exhumation events, P-T-t paths, thermal gradients and the tectonic evolu- tion of the continental rocks. These findings suggest that a pre-collisional evolution of this domain, with the burial of the continental rocks (induced by ablative subduction of the overriding Adria plate) and their exhumation (driven by an upwelling flow generated in a hydrated mantle wedge) could be a valid mechanism that reproduces the actual tectono-metamorphic config- uration of this part of the Alps. There is less agreement between the model predictions and the natural data for the Austr...

  15. Dinosaur tectonics

    DEFF Research Database (Denmark)

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

    2007-01-01

    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 for......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...... undertrack. The total length of the tectonic disturbance created by the dinosaur is up to three times that of the original footprint. Early, near-surface cementation gave the substrate the rheological properties necessary for development of the observed structures....

  16. 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....

  17. A numerical model of continental-scale topographic evolution integrating thin sheet tectonics, river transport, and orographic precipitation

    Science.gov (United States)

    Garcia-Castellanos, Daniel; Jimenez-Munt, Ivone

    2014-05-01

    How much does the erosion and sedimentation at the crust's surface influence on the patterns and distribution of tectonic deformation? This question has been mostly addressed from a numerical modelling perspective, at scales ranging from local to orogenic. Here we present a model that aims at constraining this phenomenon at the continental scale. With this purpose, we couple a thin-sheet viscous model of continental deformation with a stream-power surface transport model. The model also incorporates flexural isostatic compensation that permits the formation of large sedimentary foreland basins and a precipitation model that reproduces basic climatic effects such as continentality and orographic rainfall and rain shadow. We quantify the feedbacks between these 4 processes in a synthetic scenario inspired by the India-Asia collision. The model reproduces first-order characteristics of the growth of the Tibetan Plateau as a result of the Indian indentation. A large intramountain basin (comparable to the Tarim Basin) develops when predefining a hard inherited area in the undeformed foreland (Asia). The amount of sediment trapped in it is very sensitive to climatic parameters, particularly to evaporation, because it crucially determines its endorheic/exorheic drainage. We identify some degree of feedback between the deep and the surface processes occurs, leading locally to a <20% increase in deformation rates if orographic precipitation is account for (relative to a reference model with evenly-distributed precipitation). These enhanced thickening of the crust takes place particularly in areas of concentrated precipitation and steep slope, i.e., at the upwind flank of the growing plateau. This effect is particularly enhanced at the corners of the indenter (syntaxes). We hypothesize that this may provide clues for better understanding the mechanisms underlying the intriguing tectonic aneurisms documented in the syntaxes of the Himalayas.

  18. 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.

  19. MIDDLE JURASSIC-LOWER CRETACEOUS BIOSTRATIGRAPHY IN THE CENTRAL PONTIDES (TURKEY): REMARKS ON PALEOGEOGRAPHY AND TECTONIC EVOLUTION

    OpenAIRE

    BORA ROJAY; DEMIR ALTINER

    1998-01-01

    The deposition of Jurassic-Lower Cretaceous carbonates in the Pontides was controlled mainly by the evolution of an Atlantic-type continental margin in the Tethys. The study of several stratigraphic sections from allochthonous slices and blocks of the North Anatolian Ophiolitic Melange provided insight into the Middle Jurassic-Early Cretaceous paleogeographic evolution of the Central Pontide Belt. The Callovian-Aptian successions span the Globuligerina gr. oxfordiana, Clypeina jurassica (equi...

  20. Crustal structure and evolution of the NW Zagros Mountains (Iran): Insights from numerical modeling of the interplay between surface and tectonic processes

    Science.gov (United States)

    Saura, Eduard; Garcia-Castellanos, Daniel; Casciello, Emilio; Vergés, Jaume

    2014-05-01

    Protracted Arabia-Eurasia convergence resulted in the closure of the >2000 km wide Neo-Tethys Ocean from early Late Cretaceous to Recent. This process was controlled by the structure of the NE margin of the Arabian plate, the NE-dipping oceanic subduction beneath Eurasia, the obduction of oceanic lithosphere and the collision of small continental and volcanic arc domains of the SW margin of Eurasia. The evolution of the Zagros Amiran and Mesopotamian foreland basins is studied in this work along a ~700 km long transect in NW Zagros constrained by field, seismic and published data. We use the well-defined geometries and ages of the Amiran and Mesopotamian foreland basins to estimate the elastic thickness of the lithosphere and model the evolution of the deformation to quantitatively link the topographic, tectonic and sedimentary evolution of the system. Modelling results show two major stages of emplacement. The obduction (pre-collision) stage involves the thin thrust sheets of the Kermanshah complex together with the Bisotun basement. The collision stage corresponds to the emplacement of the basement duplex and associated crustal thickening, coeval to the out of sequence emplacement of Gaveh Rud and Imbricated Zone in the hinterland. The geodynamic model is consistent with the history of the foreland basins, with the regional isostasy model, and with a simple scenario for the surface process efficiency. The emplacement of Bisotun basement during obduction tectonically loaded and flexed the Arabian plate triggering deposition in the Amiran foreland basin. The basement units emplaced during the last 10 My, flexed the Arabian plate below the Mesopotamian basin. During this stage, material eroded from the Simply Folded belt and the Imbricated zone was not enough to fill the Mesopotamian basin, which, according to our numerical model results, required a maximum additional sediment supply of 80 m/Myr. This additional supply had to be provided by an axial drainage system

  1. MIDDLE JURASSIC-LOWER CRETACEOUS BIOSTRATIGRAPHY IN THE CENTRAL PONTIDES (TURKEY: REMARKS ON PALEOGEOGRAPHY AND TECTONIC EVOLUTION

    Directory of Open Access Journals (Sweden)

    BORA ROJAY

    1998-07-01

    Full Text Available The deposition of Jurassic-Lower Cretaceous carbonates in the Pontides was controlled mainly by the evolution of an Atlantic-type continental margin in the Tethys. The study of several stratigraphic sections from allochthonous slices and blocks of the North Anatolian Ophiolitic Melange provided insight into the Middle Jurassic-Early Cretaceous paleogeographic evolution of the Central Pontide Belt. The Callovian-Aptian successions span the Globuligerina gr. oxfordiana, Clypeina jurassica (equivalent of the Tubiphytes morronensis zone, Protopeneroplis ultragranulata (with the Haplophragmoides joukowskyi subzone, Montsalevia salevensis, Hedbergella delrioensis - Hedbergella planispira - Leupoldina - Globigerinelloides and Globigerinelloides algerianus biozones. Two major stratigraphic gaps corresponding to the pre-Callovian and Hauterivian-Early Aptian ages are recognised within the successions. Lithostratigraphic and biostratigraphic studies indicate strong similarities in the evolution of the successions in the Amasya region (Central Pontides and Biga-Bursa-Bilecik (BBB Platform (North-western Anatolia. 

  2. PALEOMAGNETISM OF SILURIAN AND DEVONIAN VOLCANICS FROM THE CHINGIZ ISLAND ARC, KAZAKHSTAN, AND ITS BEARING ON TECTONIC EVOLUTION OF THE URAL-MONGOL BELT

    Directory of Open Access Journals (Sweden)

    Natalia M. Levashova

    2015-09-01

    Full Text Available The tectonic and paleogeographic evolution of the Ural-Mongol belt between the cratons of Baltica, Siberia, and Tarim is the key to the formation of the Eurasian supercontinent during Paleozoic time, but the views on this complicated process remain very disparate and sometimes controversial. Three volcanic formations of the Middle Silurian, LowertoMiddle Devonian and Middle Devonian age from the southwestern boundary of the Chingiz Range (NE Kazakhstan yields what are interpreted as primary paleomagnetic directions that help clarify the evolution of the belt. A singlepolarity characteristic component in midSilurian andesites yields a positive intraformational conglomerate test, whereas dualpolarity prefolding components are isolated from the two Devonian collections. These new data were evaluated together with previously published paleomagnetic results from Paleozoic rocks in the Chingiz Range, and allow us to establish with confidence the hemisphere in which the area was located at a given time. We conclude that NE Kazakhstan was steadily moving northward crossing the equator in Silurian time. These new paleomagnetic data from the Chingiz range also agree with and reinforce the hypothesis that the strongly curved volcanic belts of Kazakhstan underwent oroclinal bending between Middle Devonian and Late Carboniferous time. A comparison of the Chingiz paleolatitudes with those of Siberia shows similarities between the northward motion and rotational history of the Chingiz unit and those of Siberia, which imposes important constraints on the evolving paleogeography of the Ural-Mongol belt.

  3. Pluriannual evolution of the hydrochemistry of two Alpine lakes (Lake Paione Inferiore and Lake Paione Superiore, Ossola Valley in relation to atmospheric loads.

    Directory of Open Access Journals (Sweden)

    Gabriele A. TARTARI

    1999-02-01

    Full Text Available Lakes Paione Inferiore and Paione Superiore (LPI, LPS are extremely sensitive to acidification, so they are useful as indicators in studying changes in atmospheric pollutant fluxes on waterbodies. Regular trends observed in the last 3-4 years cannot merely be a consequence of seasonal or interannual variations. Increasing pH and alkalinity are mainly driven by a decrease in acidic inputs from the atmosphere, which have been halved over the last 10 years. This trend of atmospheric deposition chemistry has emerged in several sampling stations in the subalpine and Alpine area, in the watershed of Lake Maggiore. The decrease in deposition acidity is mainly related to a decrease in sulphate, while nitrate and ammonium deposition is still high, resulting in high nitrate concentrations in lake waters.

  4. Indirect estimation of the tectonic evolution of magnetic structures along the Indiavaí-Lucialva Shear Zone, Mato Grosso, Brazil

    Science.gov (United States)

    Louro, V. H.; Ribeiro, V. B.; Mantovani, M. S.; Geolit Team

    2013-05-01

    The Indiavaí-Lucialva Shear Zone (ILSZ) has a notorious cinematic standard, moving from SW to NE, juxtaposing the Santa Helena Granitic Batholith to the metavolcanosedimentary sets and orthogneisses from the Jauru Domain basement. Along the ILSZ, a sequence of magnetic anomalies of high interference, with each other, and varied polarities occurs, what suggests the presence of different lithologies or times of (re)crystallization of the ferromagnetic minerals from these magnetic structures. In its southernmost portion, the sequence of magnetic anomalies splits in two directions, SW and SE, with the first invading the limits of the Santa Helena batholith and, the latest, accompanying the ILSZ. This study aimed for the comprehension of complex tectonic setting of this region. It analyzed the set of anomalies estimating their lateral limits, depths and directions of total magnetization, with the Enhanced Horizontal Derivatives (EHD), its extrapolation for depth estimative (EHD-Depth), and through an iterative reduction to the magnetic pole, respectively. This procedure allowed the composition of initial models for further inversions of magnetic data which, results, indicate contrasts of magnetic susceptibility in sub-surface. Once known the approximated 3-D shape of the magnetic structures along the ILSZ, the total magnetization intensity of each anomaly was recovered, what consequently allowed, by vector subtraction, to estimate their individual remnant magnetization. The remnant magnetization's inclinations and declinations of the anomalies sources and their latitudes and longitudes permitted the calculus of their respective virtual magnetic paleopoles. When confronted with the South American paleopole wander path and the datings linked to this path, available in the literature, it was possible to have an indirect approximation of the age of (re)crystallization of each magnetic structure near the ILSZ. This procedure indicated an increasing of the ages of the

  5. New insights into the North American Cordillera forearc: Cretaceous to Eocene tectonic evolution of the Leech River Schist, Southern Vancouver Island, Canada

    Science.gov (United States)

    Jakob, Johannes; Johnston, Stephen

    2015-04-01

    The Leech River Complex on southern Vancouver Island is a part of the Pacific Rim Terrane of the North American Cordillera and comprises a series of fault-bounded slices of mainly meta-sedimentary and meta-igneous rocks of Triassic to Cretaceous age. The tectono-metamorphic history of this unit provides important constraints on the history of terrane accretion and the paleogeographic and tectonic evolution of the western North American forearc region. Our focus is on the structures and tectonic fabrics that developed within the western most part of the Leech River Schist from ~88 Ma through ~37 Ma. Similar syn- and post-instrusive structures that developed during emplacement of the ~88 Ma Jordan River meta-granodiorite and the ~51 Ma Walker Creek Intrusions respectively, indicate a consistent stress field during >35 m.y. of northward translation of the outboard Cordilleran terranes. A regional high temperature, Staurolite-Andalusite-grade metamorphic event is recorded in the meta-sedimentary rocks. Subcretion of the Crescent terrane beneath the Leech River Schist at ~51 Ma caused folding of the metamorphic rocks, the development of a system of dextral and sinistral brittle shears, and normal faulting. Related extension to the northwest resulted in the opening of Barkley Sound and the more westerly marine Tofino basin. These multi-faceted deformational structures are most likely a direct consequence of the subcretion of the Crescent terrane and the linked development of the Southern Vancouver Island Orocline. The deposition of sandstones and conglomerates of the Sooke Formation began at ca. 37 Ma. This siliciclastic sequence unconformably overlies the Leech River Schist, records rapid subsidence of the forearc following a preceding uplift and exhumation event, and may be a record of a younger subcretion event.

  6. The Ordovician-Silurian tectonic evolution of the northeastern margin of the Tarim block, NW China: Constraints from detrital zircon geochronological records

    Science.gov (United States)

    Dong, Shunli; Li, Zhong; Jiang, Lei

    2016-05-01

    The northeastern margin of the Tarim block is a key tectonic-unit for understanding the evolution processes and geodynamic mechanisms of basin-range coupling between the Paleo-Asian tectonic realm to the north and the Tarim block to the south during the Paleozoic period. Four Upper Ordovician-Silurian sandstone samples were collected from the Tabei and Quruqtagh areas for measuring the detrital zircon U-Pb dating and Hf isotopic compositions, with an aim to decipher the provenances and elucidate the tectonic implications. The results show that all the sandstone samples yield evident detrital zircon U-Pb age groups of ca. 1100-720 Ma and ca. 2100-1700 Ma, demonstrating that the Tarim block was once a part of the Rodinia and Columbia supercontinents during the Neoproterozoic and the Paleoproterozoic, respectively. Remarkably, the Upper Ordovician sandstone sample from the Tabei area yields a higher proportion in age group of ca. 1100-900 Ma than that of ca. 860-720 Ma, whilst the Lower Silurian sample yields the opposite result. The former and the latter age groups aforementioned are consistent with the age patterns of the tectono-thermal events in the Central Tianshan microcontinent and the Tarim block, respectively. Combined with valuable igneous rock information, it is indicative that the Central Tianshan microcontinent drifted away from the proto Tarim block (with attachment of the Central Tianshan microcontinent) most likely at the Early Silurian. The Upper Silurian sandstone in the South Quruqtagh area yield massive detrital zircon U-Pb ages with a peak age of ca. 450 Ma, combining the Late Ordovician magmatic rocks reported from the Central Tianshan and northeastern Tarim margin, which suggests that there was a broad magmatic arc along the northeastern proto Tarim margin during the Late Ordovician. The opening of the South Tianshan Ocean began in the Early Silurian and continued in the Late Silurian, leaving a remanent magmatic arc along northeastern Tarim

  7. Palaeomagnetism and rock magnetism of the Permian redbeds from the Velebit Mt. (Karst Dinarides, Croatia): dating of the early Alpine tectonics in the Western Dinarides by a secondary magnetization

    Science.gov (United States)

    Werner, Tomasz; Lewandowski, Marek; Vlahović, Igor; Velić, Ivo; Sidorczuk, Magdalena

    2015-05-01

    The studied area of the Velebit Mt., a part of the Adria microplate, belonged to a NE margin of Gondwana during the Carboniferous and Permian. While the Carboniferous to the Early Permian was characterised by deposition of clastic rocks, younger sedimentation was dominated by a thick sequence of carbonate rocks. The Lower Permian deposits of the core part of the Velebit Mt. at Košna and Crne Grede localities were investigated using palaeomagnetic and rock magnetic measurements. The main remanence carriers were recognized as haematite with an increasing contribution of SP/SD magnetite in younger subsections. The AMS fabric with low anisotropy ratio (1-3%) is strongly oblate at Košna and weakly prolate at Crne Grede, reflecting differences in the contribution of magnetic phases. A significant remagnetization of the Permian rocks, as proved by results of a conglomerate test, probably caused by a combination of elevated temperatures and fluid migration, may be assigned to burial-related processes that affected the rocks before the final uplift of the Dinarides. Characteristic remanent magnetizations recorded in haematite are apparently similar to the Permian direction for Africa (shallow inclination with NNW declination), as expected for Velebit Mt. coordinates. Paradoxically, this orientation is observed in situ within the almost vertically dipping beds. We explain this relationship assuming a syn-folding Cretaceous remagnetization of the rocks at their subhorizontal position (ca. 30°S), in which a mean vector of the secondary remanence overlaps with the Cretaceous direction, expected for Africa at the Velebit Mt. geographical coordinates. Consequently, our results indirectly point to the Cretaceous time of incipient stages of the Dinaric tectonism, and suggest African geotectonic affinity of the Velebit rocks. No important vertical-axis rotation is implied by our results, in contrast to previously published data. The puzzling complete remagnetization carried by

  8. Evolution of Mesozoic Volcanic Basins and Red Basins in the Gan-Hang Tectonic-Volcanic Metallogenic Belt

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper mainly proposes six major regional geological events in the active continental-margin mantle uplift zone and discusses the oscillation nature of the evolution of Mesozoic volcanic basins and red basins, origin of erosion in the late stage of red basins and mechanism of volcanism.

  9. Textile Tectonics

    DEFF Research Database (Denmark)

    Mossé, Aurélie

    2008-01-01

    The meeting of architecture and textiles is a continuous but too often forgotten story of intimate exchange. However, the 2nd Ventulett Symposium hosted by the College of Architecture, within Georgia Institute of Technology, Atlanta, GA, was one of these precious moments celebrating such a marriage....... Organized by Lars Spuybroeck, principal of Nox, Rotterdam, and current Thomas W. Ventulett III distinguished chair of Architectural Design, the event was embracing the textile tectonics as a core topic, praising textiles as the key component of architecture, relying on Gottfried Semper’s understanding...... 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. On the tectonic evolution of the Tyrrhenian basin: new data from detrital zircons sampled in the Sardinia-Corsica Block and in the Calabria-Peloritain Arc

    Science.gov (United States)

    Pavanetto, Pamela; Funedda, Antonio; Matteini, Massimo; Loi, Alfredo

    2013-04-01

    Geodynamic models and palinspastic reconstructions of pery-Thyrrenian terranes in the Western Mediterranean area are still extremely complex and speculative (Stampfly & Borel 2002, Trombetta et al., 2004; Alvarez & Shimabukuro, 2009; Carminati et al., 2012).A contribute can be done by considering the relationships between Sardinia-Corsica Block (SCB) and Calabria-Peloritain Arc (CPA). They shared a similar Variscan evolution and were the western part of the Briançonnais plate until the opening of the Algero-Provençal Basin during Burdigalian and then were separated in Late Tertiary during the spreading of South-Tyrrhenian Basin. During this period the CPA moved southeastward, with respect to the SCB, driven by a progressive roll-back of the subducted slab. However, is still ambiguous if the CPA was a single terrane during the Middle and Late Tertiary (Amodio Morelli et alii, 1976) or formed by the amalgamation of two or more continental "terranes" that collided during the Tertiary (Bonardi et al., 1980; Scandone, 1982; Alvarez & Shimabukuro, 2009). The data about the paleo-tectonic linkages, the terranes derivations, and the tectonic setting of the SCB and CPA as peri-Tyrrhenian blocks during Tertiary are still poor. Some evidence of their early evolution could be found in coeval Tertiary deposits cropping out both in the SCB and CPA. These deposits represent the early stage of the estensional event developed in the Tyrrhenian region during late Oligocene-Lower Miocene in a broader regional context dominated by the opening of Atlantic Ocean and the resulting convergence of Europe and Apulia microplate (Oggiano et al., 2009). To improve the knowledge on this topic, combined U-Pb and Lu-Hf analyses on zircons from Tertiary detrital sediments from Sardinia, Corsica, and both North and South Calabria have been performed using a Thermo-Fisher Neptune MC-ICP-MS coupled with a Nd:YAG UP213 New Wave laser ablation system, at the Laboratory of Geochronology of the

  11. Edaphics, active tectonics and animal movements in the Kenyan Rift - implications for early human evolution and dispersal

    Science.gov (United States)

    Kübler, Simon; Owenga, Peter; Rucina, Stephen; King, Geoffrey C. P.

    2014-05-01

    The quality of soils (edaphics) and the associated vegetation strongly controls the health of grazing animals. Until now, this has hardly been appreciated by paleo-anthropologists who only take into account the availability of water and vegetation in landscape reconstruction attempts. A lack of understanding the importance of the edaphics of a region greatly limits interpretations of the relation between our ancestors and animals over the last few million years. If a region lacks vital trace elements then wild grazing and browsing animals will avoid it and go to considerable length and take major risks to seek out better pasture. As a consequence animals must move around the landscape at different times of the year. In complex landscapes, such as tectonically active rifts, hominins can use advanced group behaviour to gain strategic advantage for hunting. Our study in the southern Kenya rift in the Lake Magadi region shows that the edaphics and active rift structures play a key role in present day animal movements as well as the for the location of an early hominin site at Mt. Olorgesailie. We carried out field analysis based on studying the relationship between the geology and soil development as well as the tectonic geomorphology to identify 'good' and 'bad' regions both in terms of edaphics and accessibility for grazing animals. We further sampled different soils that developed on the volcanic bedrock and sediment sources of the region and interviewed the local Maasai shepherds to learn about present-day good and bad grazing sites. At the Olorgesailie site the rift valley floor is covered with flood trachytes; basalts only occur at Mt. Olorgesailie and farther east up the rift flank. The hominin site is located in lacustrine sediments at the southern edge of a playa that extends north and northwest of Mt. Olorgesailie. The lakebeds are now tilted and eroded by motion on two north-south striking faults. The lake was trapped by basalt flows from Mt. Olorgesailie

  12. Stable isotopic composition of groundwater of central California as an indicator of mid-pleistocene tectonic evolution

    International Nuclear Information System (INIS)

    In the western and central San Joaquin Valley, California, present-day shallow groundwaters with δ18O=-7.4 and -11.5 per mille, respectively, comprised of modern recharge are separated from an underlying, lower salinity, confined-aquifer system (δ18O=-9 per mille) by the thick, low permeability Corcoran Clay. The substantial thickness of the lacustrine Corcoran Clay, together with small differential head and low structural relief during much of Pleistocene time, have combined to prevent flushing of the confined paleowaters. This unusual hydrologic system of isotopically light water with a mean δ18O of -11 per mille overlying lower salinity, isotopically heavy water supports a tectonic model that calls for uplift of the Central Coast Ranges by about 1100 m in the past 615,000 a. Before uplift, water from the Sierra Nevada with a δ18O value of about -10 per mille mixed in intermittent lakes with water from the pre-emergent Coast Ranges with a δ18O value of about -6 per mille, resulting in blends of recharge water of about -9 per mille in the principal confined aquifer. Chemical and isotopic mass-balance calculations suggest that the western contribution to the confined waters ranged from 20% in the north to 35% in the southern part of the aquifer system. The present 1400 m height of the Coast Ranges results in a higher cloud base and greater interception of precipitation from storms moving inland from the Pacific than had occurred in mid-Pleistocene times. As a consequence, modern precipitation is more depleted in D and 18O over the eastern border of the central Coast Ranges and the Sierra Nevada than was pre-Corcoran precipitation. (author). 22 refs, 5 figs, 3 tabs

  13. New CHIRP Seismic Images of Submarine Terraces Around San Clemente Island Constrain its Tectonic Evolution and Geomorphology

    Science.gov (United States)

    Derosier, B.; Driscoll, N. W.; Graves, L. G.; Holmes, J. J.; Nicholson, C.

    2015-12-01

    New High-resolution CHIRP data acquired on the R/V Point Loma in 2015 imaged flights of submarine Terraces off of San Clemente Island. Outboard terraces at ~90 to 115 m below sea level (using a nominal water column velocity of 1500 m/s) may correlate with the Marine Isotope Stage 2 (MIS2); the last glacial maximum (LGM). Submarine terraces were mapped on both the gentle sloping windward (west) and the steeper sloping leeward (east) sides of San Clemente Island. The submarine terrace's depths are roughly the same on both sides of the island and suggest uniform uplift. These findings are consistent with the onshore mapping of terraces on San Clemente Island. The island exhibits a marked asymmetry both onshore and offshore, with a steeply dipping eastern margin and a gentle dipping western margin. This marked asymmetry cannot be explained by the uniform uplift of San Clemente Island based on the observed onshore and offshore terraces. In our model, the asymmetry of San Clemente Island records an early phase of predominantly extensional deformation during the middle to late Miocene, with San Clemente Island being the footwall block. Such asymmetry is also observed across the 30-mile bank and the Coronado Bank with steeply dipping eastern margins and gently dipping western margins. New regional multichannel seismic data and reprocessed industry data show no sediment divergence along the hangingwall blocks, which suggests that extensional deformation predated sedimentation. Finally, the elevations of the terraces on San Clemente Island are similar to those observed on the mainland from Baja California to Newport Beach, requiring any tectonic model fitting the uplift pattern of mainland terraces to account for the similar elevations not only along the margin but also across the margin out to 70 nautical miles offshore.

  14. 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

  15. Pre-Devonian tectonic evolution of the eastern South China Block:Geochronological evidence from detrital zircons

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Using the U-Pb LA-ICP-MS analysis technique we analyzed geochronological features of detrital zircons from Devonian and Ordovician coarse sandstone in southern Jiangxi Province,northern Cathaysia Block.Abundant ancient crustal information was obtained.The 350 groups of U-Pb age center on five ranges:2600-2300 Ma(peak at 2470 Ma),1100-900 Ma(peak at 980 Ma),900-700 Ma(peak at 800 Ma),650-520 Ma(peak at 600 Ma) and 450-400 Ma(peak at 440 Ma).We also found a detrital zircon of ~3.5 Ga.This is the oldest age in northern Cathaysia Block obtained so far.From the analysis we concluded that:(1) the 2600-2300 Ma period,characterized by a global continent-building,records late Neoarchean magmatism that did not occur in the neighboring area of Cathaysia;(2) the marked peak at 1100-900 Ma corresponds with the assembly time of the Neoproterozoic supercontinent,Rodinia,suggesting that the Cathaysia Block was once a part of Rodinia,and numerous euhedral zircons with similar ages likely resulted from the Grenville event;(3) the peak at 900-700 Ma corresponds to the breakup of Rodinia,as evidenced by wide occurrence of Neoproterozoic granite,basic dyke swarms and continental rift-type deposition;(4) the 650-520 Ma period is the typical time of the Pan-African event,but as yet no associated magmatic rock has been reported in this area;and(5) the peak at 450-400 Ma,representing the early Paleozoic orogeny,was recorded in various igneous rocks.Abundant Silurian-Lower Devonian granitic plutons,orthogneisses and their zircon U-Pb dating ages(450-400 Ma) are important evidence of an early Paleozoic orogenic event.Geological data support the interpretation of an Early Paleozoic tectonic heat event in Cathaysia,which was likely to be caused by intracontinental collision.

  16. 南黄海北部构造演化的地球物理认识%Geophysical cognition of tectonic evolution in the Northern South Yellow Sea

    Institute of Scientific and Technical Information of China (English)

    徐行; 姚永坚; 冯志强; 郝天珧; 陈春峰; 张拭颖; 万荣胜

    2011-01-01

    The northern depression in the South Yellow Sea, as a petroleum resources potential province, is also the key area to study collision effect of Sino-Korean and lower Yangtze plate and the features of geological structure of Paleozoic to Cenozoic sedimentary basins. No main breakthrough of oil and gas has been obtained in the area through 40years exploration. The reasons on exploratory failure are backward research methods and technological means in early years, misunderstanding of basic geological structure and biased exploration strategy. Based on re-interpretation and synthetic analysis of new geophysical and drillings data in recent decade, the tectonic evolution of northern of southern yellow sea, which suffer the Mesozoic land-land collision orogeny, can be divided into 4 stages: passive continental margin basin stage before plate collision (Z-T2); intra-continental faulted basin and deformation stage in the late phase of the Su-Lu collision process (L-K); postcollision intra-continental faulted basin stage (K2t-E) sand regional subsidence stage (N-Q). They correspond to five super-sequences or structural layers respectively, and each tectonic evolution stage has different stratigraphic assemblages, characteristics of tectonic deformation and seismic reflection.%南黄海北部坳陷是研究中朝板块和下扬子板块在海区碰撞效应,以及古、中、新生代沉积盆地的地质构造特征和油气资源前景的重点地区.该海域虽经历了40多年的调查与研究,未获得油气的重大突破,与早年调查研究方法的单一、技术手段的落后和对基础地质构造认识不清、勘探思路的偏颇有关.近十年来,通过对新的地球物理资料及已有钻井的综合分析和再认识,认为南黄海北部在中生代陆—陆碰撞造山作用的机制下,其构造演化经历了4个阶段:前碰撞期被动大陆边缘盆地阶段(Z-T2)、苏鲁碰撞晚期前陆盆地与变形阶段(J2-K)、碰撞期后

  17. High-pressure granulite from Western Kunlun,northwestern China:Its metamorphic evolution,zircon SHRIMP U-Pb ages and tectonic implication

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    High-pressure mafic granulites occurring as lenticular bodies within garnet-amphibolites in Kangxiwar Fault have been first reported in this paper. The P-T conditions of two metamorphic stages were ob-tained using calibrated geothermal barometers and ThermoCalc Program. The peak metamorphic con-dition of these high-pressure granulites is about 760―820℃,1.0―1.2 GPa and the retrograde meta-morphic condition is about 620―720℃,0.7―0.8 GPa. The petrological studies show that they have a near-isobaric cooling P-T path which suggests that the Western Kunlun underwent initial crustal thickening,subsequent exhumation and cooling. The SHRIMP zircon U-Pb dating gives two groups of ages for high-pressure granulites. One is 177±6 Ma which is obtained from the rim of the zircon. We consider this age should be the metamorphic age. And the other is 456±30 Ma which is obtained from the core of the zircon and should be the protolith age. The formation of these high-pressure granulites in western Kunlun is closely correlated with the evolution of the Paleo-Tethys and has important im-plications for the research on Tethys and Paleo-Asian tectonic zone.

  18. The Yermak Plateau in the Arctic Ocean in the light of reflection seismic data—implication for its tectonic and sedimentary evolution

    Science.gov (United States)

    Geissler, W. H.; Jokat, W.; Brekke, H.

    2011-12-01

    The separation of Northeast Greenland and Svalbard is the result of large-scale strike slip movements during Cenozoic times. Geological evidence for these movements can be found onshore both on North Greenland and Svalbard. However, the role of the submarine Yermak Plateau (YP) in this process is unclear. The compilation of available multichannel reflection and wide-angle seismic data give new insights into the sedimentary and crustal structure and evolution of the plateau. The flat surface of the present-day plateau is a quite young feature. Up to 2 km of Cenozoic sediments cover a rough basement, which show similarities to the rough topography and strike of geological structures of Spitsbergen Island. In some basins more than 4 km of sedimentary rocks could be mapped. The most pronounced structure is the Sverdrup Bank, which appears to be part of a larger crustal block. P-wave velocities of about 4.5 km s-1 derived from sonobuoy data indicate that its uppermost part is most probably composed of sedimentary or volcanic rocks. We have made a correlation of previously defined seismic units across the YP to outline the history of sediment deposition in the area. The existing graben structures on the plateau might have provided early shallow pathways for water exchange between the Arctic and the Atlantic Oceans. A chaotic sedimentary apron east of the Sverdrup Bank and bright reflections near the Mosby Seamount interpreted as magmatic sills suggest tectonic and magmatic events during the Miocene.

  19. Chronology and geochemistry of Mesozoic granitoids in the Bengbu area, central China: Constraints on the tectonic evolution of the eastern North China Craton

    Science.gov (United States)

    Yang, De-Bin; Xu, Wen-Liang; Wang, Qing-Hai; Pei, Fu-Ping

    2010-01-01

    We performed zircon U-Pb dating and analyses of major and trace elements, and Sr-Nd-Pb isotopes for granitoids in the Bengbu area, central China, with the aim of constraining the magma sources and tectonic evolution of the eastern North China Craton (NCC). The analyzed zircons show typical fine-scale oscillatory zoning, indicating a magmatic origin. Zircon U-Pb dating reveals granitoids of two ages: Late Jurassic and Early Cretaceous ( 206Pb/ 238U ages of 160 Ma and 130-110 Ma, respectively). The Late Jurassic rocks (Jingshan intrusion) consist of biotite-syenogranite, whereas the Early Cretaceous rocks (Huaiguang, Xilushan, Nushan, and Caoshan intrusions) are granodiorite, syenogranite, and monzogranite. The Late Jurassic biotite-syenogranites and Early Cretaceous granitoids have the following common geochemical characteristics: SiO 2 = 70.35-74.56 wt.%, K 2O/Na 2O = 0.66-1.27 (mainly Nushan and Xilushan granitoids, suggests that the primary magmas were derived from partial melting of the Yangtze Craton (YC) basement. In contrast, the occurrence of Paleoproterozoic and Paleoarchean inherited zircons within the Huaiguang granitoids indicates that their primary magmas mainly originated from partial melting of the NCC basement. The occurrence of YC basement within the lower continental crust of the eastern NCC indicates that the YC was subducted to the northwest beneath the NCC, along the Tan-Lu fault zone, during the early Mesozoic.

  20. Paleomagnetic and structural evidence for localized tectonic rotation associated with fault drag in the northeastern Mojave Desert: Implications for the late Cenozoic tectonic evolution of the Eastern California shear zone

    Science.gov (United States)

    Macconnell, D. F.; Mccabe, C.; Dokka, R. K.; Chu, M.

    1994-01-01

    Paleomagnetic data, coupled with detailed geological analysis of the southeastern Goldstone Lake region, indicate that lower Miocene volcanic and epiclastic rocks of the Pink Canyon area have been folded, faulted and tectonically rotated approximately 28.4 + or - 9.0 deg clockwise about a vertical axis. The Coyote Canyon Fault is locally folded about a vertical axis approximately 25 deg in a clockwise sense in the Pink Canyon area. Timing relationships indicate that rotation is post-early Miocene; regional relationships imply that deformation is late Miocene to Holocene in age. These relationships imply that tectonic rotation is local rather than regional in extent as proposed by some tectonic models. The results of this study are generally consistent with the Dokka and Travis model and the subsequently revised Dokka model of strain partitioning in the northeastern Mojave Desert block.

  1. The eastern Black Sea-Caucasus region during the Cretaceous: New evidence to constrain its tectonic evolution

    Science.gov (United States)

    Sosson, Marc; Stephenson, Randell; Sheremet, Yevgeniya; Rolland, Yann; Adamia, Shota; Melkonian, Rafael; Kangarli, Talat; Yegorova, Tamara; Avagyan, Ara; Galoyan, Ghazar; Danelian, Taniel; Hässig, Marc; Meijers, Maud; Müller, Carla; Sahakyan, Lilit; Sadradze, Nino; Alania, Victor; Enukidze, Onice; Mosar, Jon

    2016-01-01

    We report new observations in the eastern Black Sea-Caucasus region that allow reconstructing the evolution of the Neotethys in the Cretaceous. At that time, the Neotethys oceanic plate was subducting northward below the continental Eurasia plate. Based on the analysis of the obducted ophiolites that crop out throughout Lesser Caucasus and East Anatolides, we show that a spreading center (AESA basin) existed within the Neotethys, between Middle Jurassic and Early Cretaceous. Later, the spreading center was carried into the subduction with the Neotethys plate. We argue that the subduction of the spreading center opened a slab window that allowed asthenospheric material to move upward, in effect thermally and mechanically weakening the otherwise strong Eurasia upper plate. The local weakness zone favored the opening of the Black Sea back-arc basins. Later, in the Late Cretaceous, the AESA basin obducted onto the Taurides-Anatolides-South Armenia Microplate (TASAM), which then collided with Eurasia along a single suture zone (AESA suture).

  2. Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria

    Science.gov (United States)

    Leprêtre, A.; Klingelhoefer, F.; Graindorge, D.; Schnurle, P.; Beslier, M. O.; Yelles, K.; Déverchère, J.; Bracene, R.

    2013-08-01

    The origin of the Algerian margin remains one of the key questions still discussed in the Western Mediterranean sea, due to the imprecise nature and kinematics of the associated basin during the Neogene. For the first time, the deep structure of the Maghrebian margin was explored during the SPIRAL seismic survey. In this work, we present a N-S transect off Tipaza (west of Algiers), a place where the margin broadens due to a topographic high (Khayr-al-Din Bank). New deep penetration seismic profiles allow us to image the sedimentary sequence in the Algerian basin and the crustal structure at the continent-ocean boundary. Modeling of the wide-angle data shows thinning of the basement, from more than 15km in the continental upper margin to only 5-6km of oceanic-type basement in the Algerian basin, and reveals a very narrow or absent transitional zone. Analysis of the deep structure of the margin indicates features inherited from its complex evolution: (1) an oceanic-type crust in the deep basin, (2) similarities with margins formed in a transform-type setting, (3) a progressive deepening of the whole sedimentary cover, and the thickening of the Plio-Quaternary sediments at the margin foot, coeval with (4) a downward flexure of the basement in the basin. These features argue for a multiphased evolution of the margin, including (1) an early stage of rifting and/or spreading, (2) a late transcurrent episode related to the westward migration of the Alboran domain, and (3) a diffuse Plio-Quaternary compressional reactivation of the margin.

  3. Sand fairway mapping as a tool for tectonic restoration in orogenic belts

    Science.gov (United States)

    Butler, Rob

    2016-04-01

    The interplay between regional subsidence mechanisms and local deformation associated with individual fold-thrust structures is commonly investigated in neotectonic subaerial systems using tectonic geomorphology. Taking these approaches back into the early evolution of mountain belts is difficult as much of the key evidence is lost through erosion. The challenge is to develop appropriate tools for investigating these early stages of orogenesis. However, many such systems developed under water. In these settings the connections between regional and local tectonics are manifest in complex bathymetry. Turbidity currents flowing between and across these structures will interact with their substrate and thus their deposits, tied to stratigraphic ages, can chart tectonic evolution. Understanding the depositional processes of the turbidity currents provides substantial further insight on confining seabed geometry and thus can establish significant control on the evolution of bathymetric gradients and continuity through basins. However, reading these records commonly demands working in structurally deformed terrains that hitherto have discouraged sedimentological study. This is now changing. Sand fairway mapping provides a key approach. Fairway maps chart connectivity between basins and hence their relative elevation through time. Larger-scale tectonic reconstructions may be tested by linking fairway maps to sand composition and other provenance data. More detailed turbidite sedimentology provides substantial further insight. In confined turbidite systems, it is the coarser sand component that accumulates in the deeper basin with fines fractionated onto the flanks. Flow bypass, evidenced by abrupt breaks in grading within individual event beds, can be used to predict sand fraction distribution down fairways. Integrating sedimentology into fairway maps can chart syntectonic slope evolution and thus provide high resolution tools equivalent to those in subaerial tectonic

  4. WESTERN EXTENSION OF THE SEVAN-AKERA SUTURE ZONE (ERZINCAN-ERZURUM REGION, TURKEY): COMPARISION OF NEW DATA CONCERNING ORIGIN, STRUCTURE AND TECTONIC EVOLUTION BETWEEN SEVAN-AKERA AND ERZINCAN SUTURE ZONES

    OpenAIRE

    Hässig, Marc; Rolland, Yann; Topuz, G.; Çelik, Ö.; Sosson, Marc

    2012-01-01

    In order to better understand the tectonic evolution of the Sevan-Akera suture zone, particularly its connection westward into the Ankara-Erzincan suture, field observations and sampling were carried out on the Erzincan suture zone (near Erzincan). The goal of this study is to solve the problem of linking both odbucted ophiolitic domains. As in Armenia, the structures in Turkey are complex and have been reworked and reactivated because of post-obduction collision stages. Still, field investig...

  5. Climate vs. tectonic induced variations in Cenozoic sediment supply from western Scandinavia

    DEFF Research Database (Denmark)

    Gołędowski, Bartosz; Nielsen, S.B.; Clausen, O.R.

    on a particular rudimentary understanding of the Davisian cyclic landscape evolution model, which does not consider the occurrence of flexural isostasy or glacial buzzsaw processes. Observations of small scale sedimentary structures of ambiguous origin and activity of salt-related structures is not evidence...... for this hypothesised large-scale uplift [13]. Furthermore, there is little if any evidence for onshore Cenozoic tectonic activity, which is also not constrained by fission track dating [2, 14-20]. Climate variations during Cenozoic times are constrained by oxygen isotope values in benthic foraminifera [21...... by extensive vegetation cover as little bedrock is exposed and soils are well-developed. In case of climate cooling the tree limit lowers, exposing more bedrock for erosion. Furthermore, the erosional regime changes dramatically in the presence of alpine glaciers and cirques and when periglacial processes...

  6. Paleostress inversion of fault-slip data from the Jurassic to Cretaceous Huangshan Basin and implications for the tectonic evolution of southeastern China

    Science.gov (United States)

    Xu, Xianbing; Tang, Shuai; Lin, Shoufa

    2016-08-01

    is recorded by conjugate strike-slip faults and NW-striking thrust faults in the Huangshan Basin; (8) the 28-16 Ma ENE-WSW extensional regime resulted from subsequent post-collisional extension. This extension generated NW-striking normal faults in the Huangshan Basin and elsewhere in the eastern margin of Asia. The results of our paleostress inversion support that the Late Mesozoic to Cenozoic tectonic evolution of southeastern China is characterized by alternating strike-slip and extensional regimes.

  7. Southernmost Andes and South Georgia Island, North Scotia Ridge: Zircon U-Pb and muscovite {40Ar }/{39Ar } age constraints on tectonic evolution of Southwestern Gondwanaland

    Science.gov (United States)

    Mukasa, Samuel B.; Dalziel, Ian W. D.

    1996-11-01

    Zircon U-Pb and muscovite {40Ar }/{39Ar } isotopic ages have been determined on rocks from the southernmost Andes and South Georgia Island, North Scotia Ridge, to provide absolute time constraints on the kinematic evolution of southwestern Gondwanaland, until now known mainly from stratigraphic relations. The U-Pb systematics of four zircon fractions from one sample show that proto-marginal basin magmatism in the northern Scotia arc, creating the peraluminous Darwin granite suite and submarine rhyolite sequences of the Tobifera Formation, had begun by the Middle Jurassic (164.1 ± 1.7 Ma). Seven zircon fractions from two other Darwin granites are discordant with non-linear patterns, suggesting a complex history of inheritances and Pb loss. Reference lines drawn through these points on concordia diagrams give upper intercept ages of ca. 1500 Ma, interpreted as a minimum age for the inherited zircon component. This component is believed to have been derived from sedimentary rocks in the Gondwanaland margin accretionary wedge that forms the basement of the region, or else directly from the cratonic "back stop" of that wedge. Ophiolitic remnants of the Rocas Verdes marginal basin preserved in the Larsen Harbour complex on South Georgia yield the first clear evidence that Gondwanaland fragmentation had resulted in the formation of oceanic crust in the Weddell Sea region by the Late Jurassic (150 ± 1 Ma). The geographic pattern in the observed age range of 8 to 13 million years in these ophiolitic materials, while not definitive, is in keeping with propagation of the marginal basin floor northwestward from South Georgia Island to the Sarmiento Complex in southern Chile. Rocks of the Beagle granite suite, emplaced post-tectonically within the uplifted marginal basin floor, have complex zircon U-Pb systematics with gross discordances dominated by inheritances in some samples and Pb loss in others. Of eleven samples processed, only two had sufficient amounts of zircon for

  8. 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...

  9. From Point Defects to Plate Tectonic Faults

    OpenAIRE

    Regenauer-Lieb, Klaus; Hobbs, Bruce; Yuen, David; Ord, Alison; Zhang, Yanhua; Muhlhaus, Hans Bernd; Morra, Gabriele

    2007-01-01

    Abstract Understanding and explaining emergent constitutive laws in the multi-scale evolution from point defects, dislocations and two-dimensional defects to plate tectonic scales is an arduous challenge in condensed matter physics. The Earth appears to be the only planet known to have developed stable plate tectonics as a means to get rid of its heat. The emergence of plate tectonics out of mantle convection appears to rely intrinsically on the capacity to form extremely weak faul...

  10. The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U-Th-Sm)/He thermochronology

    Science.gov (United States)

    Wildman, Mark; Brown, Roderick; Beucher, Romain; Persano, Cristina; Stuart, Fin; Gallagher, Kerry; Schwanethal, James; Carter, Andrew

    2016-03-01

    Atlantic-type continental margins have long been considered "passive" tectonic settings throughout the entire postrift phase. Recent studies question the long-term stability of these margins and have shown that postrift uplift and reactivation of preexisting structures may be a common feature of a continental margin's evolution. The Namaqualand sector of the western continental margin of South Africa is characterized by a ubiquitously faulted basement but lacks preservation of younger geological strata to constrain postrift tectonic fault activity. Here we present the first systematic study using joint apatite fission track and apatite (U-Th-Sm)/He thermochronology to achieve a better understanding on the chronology and tectonic style of landscape evolution across this region. Apatite fission track ages range from 58.3 ± 2.6 to 132.2 ± 3.6 Ma, with mean track lengths between 10.9 ± 0.19 and 14.35 ± 0.22 µm, and mean (U-Th-Sm)/He sample ages range from 55.8 ± 31.3 to 120.6 ± 31.4 Ma. Joint inverse modeling of these data reveals two distinct episodes of cooling at approximately 150-130 Ma and 110-90 Ma with limited cooling during the Cenozoic. Estimates of denudation based on these thermal histories predict approximately 1-3 km of denudation coinciding with two major tectonic events. The first event, during the Early Cretaceous, was driven by continental rifting and the development and removal of synrift topography. The second event, during the Late Cretaceous, includes localized reactivation of basement structures as well as regional mantle-driven uplift. Relative tectonic stability prevailed during the Cenozoic, and regional denudation over this time is constrained to be less than 1 km.

  11. Radionuclide transfer in Alpine ecosystems

    International Nuclear Information System (INIS)

    Although alpine ecosystems are only of limited extent in Europe and the world, they serve as an important socio-economic basis for food production and tourism for the local population. The specific climate conditions and agricultural practice do have influence on radionuclide transfer in Alpine regions. The paper describes basic processes governing radionuclide behaviour in Alpine ecosystems and gives parameters for vertical migration of radionuclide in soil, for soil-plant transfer as well as transfer of radionuclide to cow milk. (author)

  12. NW Africa post-rift tectonics: fieldwork constraints from an "unfitting" anticline in west Morocco

    Science.gov (United States)

    Fernández-Blanco, David; Gouiza, Mohamed

    2015-04-01

    The evolution of the Moroccan Atlantic rifted margin is marked by a period of abnormal and excessive early post-rift subsidence during the Late Jurassic-Early Cretaceous affecting the proximal coastal basins, the continental shelf and the distal deep basins, which acted coevally to km-scale uplift and erosion of large domains to the east. The tectonics of the uplift event are still unclear, as it took place 30 to 50 Myr after lithospheric breakup between Morocco and Nova Scotia and prior to the Atlas/Alpine contraction, which gave rise to the Atlas and the Rif mountain belts. The Essaouira-Haha basin, located on the coastal plain of the Atlantic rifted margin of Morocco, and bounded by two uplifted Paleozoic basement highs (i.e. the Massif Ancien of Marrakech, to the east, and the Jebilet, to the northeast), is an ideal location to investigate the tectonic processes that might have triggered these vertical movements. Although most of the deformation observed in the basin is classically attributed to Upper Cretaceous halokinesis and Neogene Atlas contraction, recent works have shown the existence of contractional structures. We carry out a structural analysis of the Jbel Amsittene Anticline, located in the middle of the Essaouira-Haha basin to investigate the tectonics of its formation and its relationship with the above-mentioned exhumation. We show structural field data along several cross-sections transecting the anticline, and characterize a salt-cored fault propagation fold verging north, with a Triassic salt acting as a detachment plane. Regional kinematic indicators and structures show overall NNW-SSE to NNE-SSW shortening and active tectonics during the postrift phase, as indicated by syn-tectonic wedges seen for the Late Jurassic to Early Cretaceous period. These facts discard the "salt-drives-tectonics" theory to let "tectonic-drives-salt" one to rise, and point to factors other than small-cell mantle convection acting during the evolution of the Moroccan

  13. Spatial-temporal evolution of topography of the central Andes and implications for deep tectonic processes (Invited)

    Science.gov (United States)

    Garzione, C. N.; Auerbach, D. J.; Bershaw, J. T.; Kar, N.; Smith, J. J.

    2013-12-01

    Resolving the spatial and temporal evolution of changes in the elevation of mountain belts provides constraints on the geodynamic mechanisms that caused surface uplift of these regions. Several recent studies in the Central Andean plateau (between 13°S and 28°S) have used multiple climate proxies to demonstrate punctuated (several myr) changes in the composition of meteoric water and surface temperature inferred to reflect significant (≥1000 m) surface uplift. These studies suggest that different regions experienced surface uplift at different times. In comparison with crustal thickening histories derived from reconstructions of crustal shortening, it is also clear that crustal thickening and surface uplift are temporally decoupled, with significant crustal thickening preceding punctuated surface uplift events by several tens of millions of years. Here we compile results from paleoclimate studies of the Central Andean plateau to infer regional patterns of surface uplift. Limited paleoclimate data and geologic evidence indicate that the Eastern Cordillera experienced an earlier pulse of surface uplift than the Altiplano zone, associated with an eastward sweep of magmatism that marks the current limits of the plateau. Within the Altiplano zone, the southern Altiplano appears to have risen beginning in middle Miocene time and continuing through late Miocene time. During this time, the north-central Altiplano remained low and experienced increasing rates of sedimentation. In late Miocene time, sedimentation rates slowed dramatically at the same time that climate proxy data suggest rapid surface uplift of the north-central Altiplano. The northernmost Altiplano of Peru experienced a pulse of surface uplift in middle Miocene to early Pliocene time, with the exact timing unconstrained as of yet. Crustal shortening reconstructions from the southern through the north-central plateau (between 17°S and 24°S) yield upper estimates that range between 300×20 km, sufficient

  14. Petrology, geochemistry and tectonic settings of the mafic dikes and sills associated with the evolution of the Proterozoic Cuddapah Basin of south India

    Indian Academy of Sciences (India)

    Nilanjan Chatterjee; Somdev Bhattacharji

    2001-12-01

    In this article we summarize the petrological, geochemical and tectonic processes involved in the evolution of the Proterozoic intracratonic Cuddapah basin. We use new and available ages of Cuddapah igneous rocks, together with field, stratigraphic, geophysical and other criteria, to arrive at a plausible model for the timing of these processes during basin evolution. We present petrological and geochronological evidence of dike emplacement along preferred lineament directions around the basin in response to stresses, which may have been responsible for the evolution of the basin itself. Basaltic dike intrusion started on the south Indian shield around 2400 Ma and continued throughout the Cuddapah basin evolution and sedimentation. A deep mantle perturbation, currently manifested by a lopolithic cupola-like intrusion under the southwestern part of the basin, may have occurred at the onset of basin evolution and played an important role in its development. Paleomagnetic, gravity and geochronological evidence indicates that it was a constant thermal source responsible for dike and sill emplacement between 1500 and 1200 Ma both inside and outside the basin. Lineament reactivation in the NW-SE and NE-SW directions, in response to the mantle perturbation, intensified between 1400 and 1200 Ma, leading to the emplacement of several cross cutting dikes. Fe-Mg partition coefficients of olivine and augite and Ca-Na partition coefficient of plagioclase, calculated from the composition of these minerals and bulk composition of their host rocks, indicate that the dikes outside the Cuddapah basin are cumulates. The contemporary dikes may be related by fractional crystallization as indicated by a positive correlation between their plagioclase Ca#(atomic Ca/[Ca+Na]) and augite Mg#(atomic Mg/[Mg+Fe]). A few NW-SE and NE-SW cross cutting dikes of the period between 1400 and 1200 Ma, preserve petrographic evidence of episodic magmatic intrusive activity along preferred directions

  15. Mesozoic tectonic evolution of the Daba Shan Thrust Belt in the southern Qinling orogen, central China: Constraints from surface geology and reflection seismology

    Science.gov (United States)

    Li, Jianhua; Dong, Shuwen; Yin, An; Zhang, Yueqiao; Shi, Wei

    2015-08-01

    The Daba Shan Thrust Belt is located along the southern margin of the Qinling orogen that separates the north China block in the north from the south China block in the south. Despite decades of research, the total magnitude of shortening accommodated by continent-continent convergence across the Qinling orogen after Triassic ocean closure between north and south China remains poorly constrained. The lack of knowledge on the shortening magnitude in turn limits our ability to test a wide array of tectonic models for the development of the Qinling orogen and thus the convergence history between north and south China. In order to address this issue, we construct a balanced cross section and develop a new kinematic model for the evolution of the Daba Shan Thrust Belt. This work was accomplished by integrating (1) surface geologic mapping, (2) detailed kinematic analysis of key structures, (3) existing geochronologic and thermochronological data, and (4) a recently obtained lithospheric-scale seismic reflection profile. Restoration of the cross section indicates that the minimum shortening strain increases northward from ~10% in the foreland to >45% in the thrust belt interior. The estimated amount of upper crustal shortening across the Daba Shan Thrust Belt is >130 km, which is sufficient to allow the inferred mafic lower crust of the subducted south China lithosphere to have experienced eclogite phase transition. Thus, our work supports that the development of the Daba Shan Thrust Belt may have been driven by slab pull of the subducted mafic lower crust at the leading edge of the down-plunging south China continental lithosphere.

  16. Late Paleozoic magmatic record of Middle Gobi area, South Mongolia and its implications for tectonic evolution: Evidences from zircon U-Pb dating and geochemistry

    Science.gov (United States)

    Zhu, Mingshuai; Miao, Laicheng; Baatar, Munkhtsengel; Zhang, Fochin; Anaad, Chimedtseren; Yang, Shunhu; Li, Xingbo

    2016-01-01

    Late Paleozoic subduction-accretion complexes occur widely in Middle Gobi area and provide a good opportunity for unraveling the Paleozoic tectonic evolution of South Mongolia. The magmatic rocks in the Tsavchir hudug district mainly consist of rhyolites and volcaniclastic rocks. The rhyolites show enrichment in LREE and LILE and negative Nb, Ta and Ti anomalies, indicating genesis in the subduction zone. A rhyolite sample from the Tsavchir hudug region yielded a SHRIMP 206Pb/238U zircon age of 315 ± 4 Ma (MSWD = 0.79, n = 15). The andesite overlying the Namdain hundy Early Paleozoic ophiolite shows adakite geochemical features, and the two andesite samples yielded SHRIMP 206Pb/238U zircon ages of 325 ± 3 Ma (MSWD = 1.6, n = 14) and 319 ± 4 Ma (MSWD = 0.56, n = 13), respectively, suggesting that the Carboniferous island arc formed on the basis of Early Paleozoic accretionary complex. The granodiorite sample that intrudes the Early Paleozoic accretion complex with adakite geochemical features yielded a SHRIMP 206Pb/238U zircon age of 333 ± 4 Ma (MSWD = 1.6, n = 16), representing the Late Paleozoic island arc intrusive. The SHRIMP U-Pb analyses for the tuff sandstones that occur associated with Early Paleozic oceanic inliers in Middle Gobi area suggest detrital zircons mainly stem from the Devonian-Carboniferous arc. The age data obtained from the ophiolite (528-509 Ma) and tuff sandstone indicate the accretion in Middle Gobi area lasted from Early Paleozoic to Late Paleozoic for at least ca. 200 Ma, suggesting the ocean of the accretionary complex was the major Paleo-Asain ocean basin. The subduction related magmatic belt in Middle Gobi area includes both Early Paleozoic and Late Paleozoic island arc activities, which is consistent with the accretion duration time obtained from accretionary complex and also attests the argument of major Paleo-Asain ocean basin.

  17. U-Pb geochronology and geochemistry of Bibi-Maryam pluton, eastern Iran: Implication for the late stage of the tectonic evolution of the Sistan Ocean

    Science.gov (United States)

    Delavari, Morteza; Amini, Sadraddin; Schmitt, Axel K.; McKeegan, Kevin D.; Mark Harrison, T.

    2014-07-01

    The Bibi-Maryam pluton crops out in the Sistan suture zone, eastern Iran. This pluton is a 1.5 × 2 km stock composed of leucocratic tonalite, granodiorite and granite. U-Pb zircon geochronology of a leucogranite indicates an emplacement age of 58.6 ± 2.1 Ma (95% confidence). The Bibi-Maryam rock suite is sodic with elevated Na2O/K2O (2.9 to 5.5), Sr/Y (15.6-62.2), La/Yb (13.3-22.2), and low MgO (0.86-1.81) abundances. It lacks significant Eu anomalies. Because of these geochemical characteristics, Bibi-Maryam rocks are similar to high-SiO2 adakites. Trace element modeling indicates that the Bibi-Maryam adakitic rocks could be produced by 5-8% non-modal batch partial melting from a source with composition of 95% N-MORB + 5% sediment in the presence of 35-40% amphibole + 5-10% garnet + 55-60% clinopyroxene + 1% apatite + 1% rutile. This source mineralogy is similar to hornblende eclogite or garnet amphibolites. Collectively, these data provide new constraints for the evolution of the Sistan suture zone and suggest that the Bibi-Maryam pluton formed via slab melting in an oceanic arc and pre-plate collision tectonic setting. This implies that the closure of the Sistan Ocean and Lut-Afghan continental blocks collision happened after the Bibi-Maryam emplacement at 58.6 ± 2.1 Ma.

  18. Besshi-type mineral systems in the Palaeoproterozoic Bryah Rift-Basin, Capricorn Orogen, Western Australia:Implications for tectonic setting and geodynamic evolution

    Institute of Scientific and Technical Information of China (English)

    Franco Pirajno; Yanjing Chen; Nuo Li; Chao Li; Limin Zhou

    2016-01-01

    In this contribution we use VMS mineral systems in the Bryah rift-basin to constrain the tectonic setting of the widespread mafic and ultramafic magmatism that characterises the rift-basin in question. Two distinct, but temporally closely associated, lithostratigraphic sequences, Narracoota and Karalundi For-mations, are discussed. The Karalundi Formation is the main host of VMS mineral systems in the region. The Karalundi Formation consists of turbiditic and immature clastic sediments, which are locally intercalated with basaltic hyaloclastites, dolerites and banded jaspilites. We propose that the basaltic hyaloclastites, dolerites and clastics and jaspilites rocks, form a distinct unit of the Karalundi Formation, named Noonyereena Member. The VMS mineral systems occur near the north-east trending Jenkin Fault and comprise the giant and world-class DeGrussa and the Red Bore deposits. The nature of these deposits and their intimate association with terrigenous clastic rocks and dominantly marine mafic volcanic and subvolcanic rocks, as well as the common development of peperitic margins, are considered indicative of a Besshi-type environment, similar to that of present-day Gulf of California. Our Re-Os age data from a primary pyrite yielded a mean model age of 2012 ? 48 Ma, which coincides (within error) with recent published Re-Os data (Hawke et al., 2015) and confirms the timing of the proposed geodynamic evo-lution. We propose a geodynamic model that attempts to explain the presence of the Narracoota and Karalundi Formations as the result of mantle plume activity, which began with early uplift of continental crust with intraplate volcanism, followed by early stages of rifting with the deposition of the Karalundi Formation (and Noonyereena Member), which led to the formation of Besshi-type VMS deposits. With on-going mantle plume activity and early stages of continental separation, an oceanic plateau was formed and is now represented by mafic-ultramafic rocks of

  19. Tectonic evolution of the Western Kunlun orogenic belt in northern Qinghai-Tibet Plateau: Evidence from zircon SHRIMP and LA-ICP-MS U-Pb geochronology

    Institute of Scientific and Technical Information of China (English)

    ZHANG ChuanLin; LU SongNian; YU HaiFeng; YE HaiMin

    2007-01-01

    The Western Kunlun Range in northern Qinghai-Tibet Plateau is composed of the North Kunlun Terrane,the South Kunlun Terrane and the Karakorum-Tianshuihai Terrane. Here we report zircon SHRIMP and LA-ICP-MS U-Pb ages of some metamorphic and igneous rocks and field observations in order to provide a better understanding of their Precambrian and Palaeozoic-early Mesozoic tectonic evolution.Based on these data we draw the following conclusions: (1) The paragneisses in the North Kunlun Terrane are likely of late Mesoproterozoic age rather than Palaeoproterozoic age as previously thought,representing tectonothermal episodes at 1.0-0.9 Ga and ~0.8 Ga. (2) The North Kunlun Terrane was an orogenic belt accreted to the southern margin of Tarim during late Mesoproterozoic to early Neoproterozoic, the two episodes of metamorphisms correspond to the assemblage and breakup of Rodinia respectively. (3) The Bulunkuole Group in western South Kunlun Terrane, which was considered to be the Palaeoproterozoic basement of the South Kunlun Terrane by previous studies, is now subdivided into the late Neoproterzoic to early Palaeozoic paragneisses (khondalite) and the early Mesozoic metamorphic volcano-sedimentary series; the paragneisses were thrust onto the metamorphic volcano-sedimentary series from south to north, with two main teconothermal episodes (i.e., Caledonian,460-400 Ma, and Hercynian-Indosinian, 340-200 Ma), and have been documented by zircon U-Pb ages.(4) In the eastern part of the South Kunlun Terrane, a gneissic granodiorite pluton, which intruded the khondalite, was crystallized at ca. 505 Ma and metamorphosed at ca. 240 Ma. In combination with geochronology data of the paragneiss, we suggest that the South Kunlun Terrane was a Caledonian accretionary orogenic belt and overprinted by late Paleozoic to early Mesozoic arc magmatism.

  20. Tectonic evolution of the Western Kunlun orogenic belt in northern Qinghai-Tibet Plateau:Evidence from zircon SHRIMP and LA-ICP-MS U-Pb geochronology

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Western Kunlun Range in northern Qinghai-Tibet Plateau is composed of the North Kunlun Terrane,the South Kunlun Terrane and the Karakorum-Tianshuihai Terrane. Here we report zircon SHRIMP and LA-ICP-MS U-Pb ages of some metamorphic and igneous rocks and field observations in order to pro-vide a better understanding of their Precambrian and Palaeozoic-early Mesozoic tectonic evolution. Based on these data we draw the following conclusions: (1) The paragneisses in the North Kunlun Terrane are likely of late Mesoproterozoic age rather than Palaeoproterozoic age as previously thought,representing tectonothermal episodes at 1.0―0.9 Ga and ~0.8 Ga. (2) The North Kunlun Terrane was an orogenic belt accreted to the southern margin of Tarim during late Mesoproterozoic to early Neopro-terozoic,the two episodes of metamorphisms correspond to the assemblage and breakup of Rodinia respectively. (3) The Bulunkuole Group in western South Kunlun Terrane,which was considered to be the Palaeoproterozoic basement of the South Kunlun Terrane by previous studies,is now subdivided into the late Neoproterzoic to early Palaeozoic paragneisses (khondalite) and the early Mesozoic metamorphic volcano-sedimentary series; the paragneisses were thrust onto the metamorphic vol-cano-sedimentary series from south to north,with two main teconothermal episodes (i.e.,Caledonian,460―400 Ma,and Hercynian-Indosinian,340―200 Ma),and have been documented by zircon U-Pb ages. (4) In the eastern part of the South Kunlun Terrane,a gneissic granodiorite pluton,which intruded the khondalite,was crystallized at ca. 505 Ma and metamorphosed at ca. 240 Ma. In combination with geochronology data of the paragneiss,we suggest that the South Kunlun Terrane was a Caledonian accretionary orogenic belt and overprinted by late Paleozoic to early Mesozoic arc magmatism.

  1. Sudbuction-related tectonic mixing between serpentinized mantle and continental crust in the internal Western Alps: exhumed portion of a marble cake?

    Science.gov (United States)

    Spalla, M.; Zucali, M.; Cantù, M.; Roda, M.; Marotta, A.

    2011-12-01

    The pre-Alpine continental crust of the Western Alps is widely affected by subduction-related high-pressure low-temperature (HP-LT) metamorphism and the Sesia-Lanzo Zone (SLZ) represents the widest crustal complex re-equilibrated under HP conditions during Late-Cretaceous (early-Alpine) times. Its Alpine tectonic evolution is compatible with an uplift during active oceanic lithosphere subduction (e.g. Spalla et al., 1996; Meda et al., 2010; Zucali & Spalla, 2011). In the SLZ three main lithologic complexes have been recognized (e.g. Compagnoni et al., 1977): i) Gneiss Minuti complex (GMC); ii) Eclogitic Micaschists complex (EMC); iii) II Dioritic-Kinzigitic Zone (IIDK). IIDK consists of kilometer-size lenses of pelitic and mafic granulites that escaped eclogite facies re-equilibration. EMC and GMC, both pervasively eclogitised, strongly differ in the volume percentage of greenschist facies re-equilibration (Stuenitz, 1989; Spalla et al., 1991). In the southern SLZ the metamorphic complex of Rocca Canavese thrust sheets (RCT; Pognante, 1989 a; Pognante, 1989b) has been recognised, on the ground of its strongly contrasted Alpine metamorphic evolution, characterized by a P-climax recorded under very LT conditions. A new multi-scale structural analysis, performed to acquire new detailed petrologic data and to refine the tectonic trajectory of such a peculiar metamorphic complex, pointed out that RCT is a tectonic mixing of serpentinized mantle and continental rocks deformed together under high pressure conditions. Field analysis reports a superposed grid of metamorphic foliations allowing regional scale correlation of structural and metamorphic stages, after micro-structural identification of mineral assemblages marking successive fabrics in each rock type. Chemical data on variations of mineral compositions in different micro-structural sites, led to the reconstruction of a PTdt (Pressure-Temperature-relative deformation time) path and opened therefore the possibility

  2. Tectonic and magmatic evolution of the northwestern Basin and Range and its transition to unextended volcanic plateaus: Black Rock Range, Nevada

    Science.gov (United States)

    Lerch, D.W.; Miller, E.; McWilliams, M.; Colgan, J.

    2008-01-01

    ??-10??) and concomitant uplift occurring after 16 Ma. This tectonic history is consistent with that of the nearby Pine Forest and Santa Rosa Ranges, where low-temperature thermochronology documents footwall exhumation along the range-bounding normal faults after 12 Ma. The velocity structure of the crust beneath the northern Black Rock Range is constrained by a recent geophysical survey (seismic reflection, refraction, and gravity) and contains gradients that correspond to basin depths predicted by our geologic mapping. Together with recently completed geological and geophysical studies from the surrounding region, our results suggest that the evolution of the northwestern margin of the Basin and Range was characterized by long-lived and voluminous volcanism without significant tectonism, followed by low-magnitude (???20%) extension along high-angle normal faults. ?? 2008 Geological Society of America.

  3. Discussion on regional geo tectonic setting of Ganhang tectonic belt

    International Nuclear Information System (INIS)

    The knowledge of Precambrian structural framework in southern China has been progressed during a long period of study. Based on the comprehensive analysis on Precambrian formations and tectonic evolution the following conclusions are made: (1) The Cathaysia is a desintegrated Early Precambrian old land; (2) Zhexi-Gandongbei region was an active continental margin; (3) The Wuling orogeny is the most important one in the evolution of southern China during which a collision between the Cathaysia and Yangzi blocks occurred forming the united South China Old-land; (4) The Late Proterozoic tectonic evolution in various areas showed obvious difference because of the difference in regional geology. In a word, the Ganhang fault belt was an 'A' subduction zone in the early stage of Late Proterozoic

  4. Molecular phylogenetic analyses identify Alpine differentiation and dysploid chromosome number changes as major forces for the evolution of the European endemic Phyteuma (Campanulaceae).

    Science.gov (United States)

    Schneeweiss, Gerald M; Pachschwöll, Clemens; Tribsch, Andreas; Schönswetter, Peter; Barfuss, Michael H J; Esfeld, Korinna; Weiss-Schneeweiss, Hanna; Thiv, Mike

    2013-12-01

    Phyteuma is a chromosomally and ecologically diverse vascular plant genus and constitutes an excellent system for studying both the role of chromosomal change for species diversification and the evolution of high-mountain biota. This kind of research is, however, hampered by the lack of a sound phylogenetic framework exacerbated by the notoriously low predictive power of traditional taxonomy with respect to phylogenetic relationships in Campanulaceae. Based on a comprehensive taxon sampling and analyses of nuclear and plastid sequence and AFLP fingerprint data, Phyteuma is confirmed as a monophyletic group sister to the monotypic Physoplexis, which is in line with their peculiar flower morphologies. Within Phyteuma two clades, largely corresponding to previously recognized sections, are consistently found. The traditional circumscription of taxonomic series is largely rejected. Whereas distinctness of the currently recognized species is mostly corroborated, some interspecific relationships remain ambiguous due to incongruences between nuclear and plastid data. Major forces for diversification and evolution of Phyteuma are descending dysploidy (i.e., a decrease in chromosome base number) as well as allopatric and ecological differentiation within the Alps, the genus' center of species diversity. PMID:23891952

  5. Identification of new NE-trending deep-seated faults and tectonic pattern updating in northern Tunisia (Mogodos-Bizerte region), insights from field and seismic reflection data

    Science.gov (United States)

    Essid, El Mabrouk; Kadri, Ali; Inoubli, Mohamed Hedi; Zargouni, Fouad

    2016-07-01

    The northern Tunisia is occupied by the Tellian domain constituent the eastern end of the Maghrebides, Alpine fold-thrust belt. Study area includes partially the Tellian domain (Mogodos belt) and its foreland (Bizerte region). Most of this region outcrops consist of Numidian thrust sheet flysch attributed to the lower Oligocene-Burdigalian. In the study area, the major fault systems are still subject of discussion. The Numidian nappe structure, the distribution of basalt and Triassic outcrops within and at the front of this Tellian domain deserve more explanation. In this work we intend to update the structural scheme and the tectonic evolution of the northern Tunisia, taking into account salt tectonics and magmatism. The updated tectonic evolution will be integrated in the geodynamic framework of the Central Mediterranean. For this purpose, we have analyzed morphologic, seismic and structural data. The compilation of the results has allowed the identification of new regional NE-trending faults dipping towards the NW: the Bled el Aouana-Bizerte, the Sejnane-Ras Enjla and the Oued el Harka faults. They correspond to the reactivation of deep-seated normal faults splaying on the Triassic evaporites. This fault system constitutes the main component of the northern Tunisia structural scheme and has influenced its tectonic evolution marked by the main following stages. The Tellian thrust-sheets were immobilized at the uppermost Langhian. During the major Tortonian NW-trending compressive phase, these faults were reactivated with reverse kinematics and controlled the distribution of the post-nappes Neogene continental deposits. At the early Pleistocene, a compressive NNW-trending event has reactivated again these faults with sinistral-reverse movements and deformed the post-nappes Neogene series. Late Quaternary to Actual, the tectonic regime continues to be compressive with a NNW-trending maximum horizontal stress.

  6. Geochronology and Geochemistry of Middle-Late Ordovician Granites and Gabbros in the Erguna Region, NE China:Implications for the Tectonic Evolution of the Erguna Massif

    Institute of Scientific and Technical Information of China (English)

    Shuo Zhao; Wenliang Xu; Wei Wang; Jie Tang; Yihan Zhang

    2014-01-01

    Zircon U-Pb ages, Hf isotope data and whole-rock major and trace element data for the Middle to Late Ordovician gabbros and granites in the Erguna Massif, NE China were presented in this paper. The petrogenesis of these rocks and the Early Paleozoic tectonic evolution of the massif were discussed. Zircons from the granites and gabbros are of magmatic origin based on their cathodolumi-nescence (CL) images. The206Pb/238U ages obtained from 20 spots on zircons from the granites range from 446±9 to 464±10 Ma, yielding a weighted mean age of 455±10 Ma; and 16 spots on zircons from the gabbros range from 465±10 to 466±7 Ma, yielding a weighted mean age of 465±2 Ma. Chemically, the Late Ordovician granites in the Erguna Massif are weakly peraluminous and similar to A-type granites. The granites and gabbros are all enriched in light rare earth elements and large ion lithophile elements (e.g., Rb, K), and depleted in heavy rare earth elements and high field strength elements (e.g., Nb, Ta, and Ti); they all exhibit marked negative Eu anomalies. Their zirconεHf(t) values range mainly from +1.86 to +6.21 (for the granites) and +1.39 to +3.89 (for the gabbros), except for one spot with a value of -0.27 (for a gabbro). TheTDM1 ages for the gabbros andTDM2 ages for the granites vary from 928 to 1 091 Ma and from 1 287 to 1 675 Ma, respectively. It is concluded that the primary magma of the granites could have been derived by partial melting of Mesoproterozoic newly accreted crustal ma-terial, whereas the primary magma of the gabbros originated by partial melting of a depleted mantle wedge that had been metasomatized by fluids derived from a subducted slab. These Middle-Late Or-dovician granites and gabbros constitute a typical bimodal igneous rock association, implying an exten-sional environment that was probably related to the post-collisional development of the Erguna and Xing’an massifs in the early Early Paleozoic.

  7. Campo Belo Metamorphic Complex: tectonic evolution of an Archean sialic crust of the southern São Francisco Craton in Minas Gerais (Brazil

    Directory of Open Access Journals (Sweden)

    ARILDO H. OLIVEIRA

    2001-09-01

    Full Text Available Systematic geological studies performed in the study area allowed the characterization of six lithodemic units: three gneissic, one amphibolitic, one supracrustal and one fissure mafic. The mineral assemblage and the structural record of these lithodemic units indicate that the study area was affected by five tectonothermal events. The structural pattern of the first and oldest event occurred under granulite facies conditions and reveals essentially a sinistral kinematic pattern. The second event, showing dominant extensional characteristics, is related to the generation of an ensialic basin filled by the volcano-sedimentary sequence of the supracrustal lithodemic unit. The third event, which is the most expressive in the study region, is characterized by a vigorous regional migmatization process and by the generation of the Claudio Shear Zone, presenting dextral kinematic movement. The fourth event is represented by a fissure mafic magmatism (probably two different mafic dike swarms and finally, the fifth event is a regional metamorphic re-equilibration that reached the greenschist facies, closing the main processes of the tectonic evolution of the Campo Belo Metamorphic Complex.Estudos geológicos sistemáticos permitiram a caracterização de seis unidades litodêmicas na área estudada: três gnáissicas, uma anfibolítica, uma supracrustal e uma máfica fissural. A assembléia mineral e os registros estruturais dessas unidades litodêmicas mostraram que a área estudada foi afetada por cinco eventos tectonotermais. O padrão estrutural do primeiro e último evento ocorreu em condições de fácies granulito e revelaram uma cinemática essencialmente sinistral. O segundo evento mostrou uma tectônica extensional relacionado à abertura da bacia ensiálica onde se alojou a seqüência vulcanosedimentar da unidade supracrustal. O terceiro evento, que é o mais expressivo na região estudada, é o responsável por um intenso processo de

  8. Tectonic Controls on the Volumes and Petrologic Evolution of Pantellerite-Trachyte-Phonolite Volcanoes in a Continental Rift Setting, Marie Byrd Land, Antarctica

    Science.gov (United States)

    Lemasurier, W. E.

    2010-12-01

    The 18 alkaline volcanoes in Marie Byrd Land (MBL) are characterized by large volumes of felsic rock and a large range in composition, from trachyte to pantellerite, comendite, and phonolite. These characteristics are controlled largely by mantle plume activity, a stationary plate environment, and lithospheric structure of the West Antarctic rift system in coastal MBL. Felsic rocks occur either as summit sections of basalt volcanoes, or comprising all the rock exposed above ice level. Their exposed volumes range from ~30-780 km3 in individual volcanoes. Seven fall between 200-780 km3. Field observations and one seismic traverse show that felsic sections are underlain by thick (1-5 km) sequences of basalt, dominated by basanite. Thus, in spite of their large volumes, felsic rocks appear to make up only ~10% of all the volcanic rock in the province. In four of these volcanoes, pantellerite, trachyte, and phonolite eruptions alternated with each other, and/or took place coevally from the same edifice, indicating that these magmas were available throughout the ~15 m.y. histories of these volcanoes from isolated, but closely adjacent upper crustal reservoirs. Isotope data record crustal contamination in some felsic rocks, but constrain it to <3%, at most. This, plus the results of major and trace element modeling, imply that pantellerites, trachytes and phonolites all evolved from basanite magma by fractional crystallization (FC). Phonolites could have evolved largely by low-pressure FC of basanite in the upper crust. However, modeling and experimental data suggest that 90-95% of pantellerite evolution took place below the crust, where inclusion of kaersutite among fractionated phases, in a low fO2 environment, were key to developing an FeO-rich and SiO2-rich pantellerite lineage from basanite. The complexity of the felsic suite seems related to the presence of mechanical boundaries at the base of the lithosphere (~50 km) and base of the crust (~25 km), that trapped

  9. Late Cretaceous high-Mg# granitoids in southern Tibet: Implications for the early crustal thickening and tectonic evolution of the Tibetan Plateau?

    Science.gov (United States)

    Chen, Jian-Lin; Xu, Ji-Feng; Yu, Hong-Xia; Wang, Bao-Di; Wu, Jian-Bin; Feng, Yue-Xing

    2015-09-01

    This study presents new major and trace element, plus Sr-Nd and zircon U-Pb isotope data for the Zhongcang granitic plutons, which are located to the south of the Yongzhu-Asuo ophiolite belt within the northwestern part of the central Lhasa subterrane, Tibetan Plateau. These data provide new insights into the Late Cretaceous tectonic evolution of southern Tibet. The Zhongcang plutons are dominated by granodiorites and granites that yield zircon U-Pb emplacement ages of 94-88 Ma. They can be further divided into metaluminous and peraluminous subtypes. The metaluminous rocks have adakite-like geochemical signatures, including high SiO2, Al2O3, and Sr concentrations, and low Yb and Y concentrations, and high Sr/Y and (La/Yb)N ratios. These rocks also have negative εNd(t) values (- 3.17 to - 0.17), variable initial 87Sr/86Sr(i) ratios (0.705927-0.707668), and high K2O and Th concentrations, suggesting that they were not derived from the partial melting of subducted oceanic crust in an arc setting. The Zhongcang adakitic rocks have higher MgO and Cr concentrations and Mg# values than do contemporaneous intrusive rocks derived from a region of thickened lower crust within the central Lhasa subterrane. These data suggest that the Zhongcang adakitic rocks were generated by the partial melting of a delaminated thickened lower crust within a Late Cretaceous continental setting. In comparison with the Zhongcang adakitic rocks, the peraluminous rocks have significant negative Eu and Sr anomalies and lower εNd(t) values (- 4.06 to - 6.64). This, combined with their high Mg# values, and Cr concentrations, suggests that the peraluminous units formed from primitive magmas similar to those that formed the Zhongcang adakitic rocks, but modified by contamination with ancient crustal material and by fractional crystallization of plagioclase and apatite during uprising and/or emplacement. The Zhongcang high-Mg# granitoids provide robust evidence for Late Cretaceous crustal thickening

  10. The petrogenesis of sodic granites in the Niujuanzi area and constraints on the Paleozoic tectonic evolution of the Beishan region, NW China

    Science.gov (United States)

    Yu, Jiyuan; Guo, Lin; Li, Jianxing; Li, Yanguang; Smithies, Robert H.; Wingate, Michael T. D.; Meng, Yong; Chen, Shefa

    2016-07-01

    Ordovician to Devonian sodic granites dominate the newly recognized Luotuojuan composite granite in the Lebaquan-Luotuojuan-Niujuanzi region of Beishan, along the southern margin of the Central Asian Orogenic Belt in NW China. The granites include sodic (K2O/Na2O > 0.5) tonalites with low Y ( 68) that formed during at least two events at c. 435 and c. 370-360 Ma. Their compositions are consistent with high-pressure melting of basaltic crust, although relatively non-radiogenic Nd isotope compositions (εNd(t) + 0.9) require some crustal assimilation. The interpretation that these granites reflect melts of a subducted slab (i.e. adakite) is supported by independent local and regional geological evidence for an oceanic subduction-accretion setting, including a long history of calc-alkaline magmatism and the identification of a series of early Paleozoic ophiolite belts. Other sodic granites forming the Luotuojuan composite granite are mainly quartz-diorite and granodiorite formed between c. 391 and c. 360 Ma. These rocks are not adakites, having Sr concentrations and Sr/Y ratios too low and Y and Yb concentrations too high. They are low- to medium-K calc-alkaline rocks more typical of magmas derived through melting in a subduction modified mantle wedge. Compositional changes from sodic to potassic granites, over time frames consistent with subduction processes, suggest at least two separate cycles, or pulses, of hot subduction in the Lebaquan-Luotuojuan-Niujuanzi region. Although early Paleozoic adakites have been inferred to exist elsewhere in the Beishan region, many of the reported adakitic rocks have compositions inconsistent with melting of subducted oceanic lithosphere and so tectonic interpretation of hot subduction might not be valid in these cases. A study of regional granite data also shows not only that adakite magmatism does not extend into the Permian but that if subduction-accretion processes extended into the late Paleozoic, no typical subduction

  11. Tectonic map of Uruguay

    International Nuclear Information System (INIS)

    The tectonic evolution of Uruguay is presented from the synthesis of the geological evolution. It will be show the evolution of different orogenic cycles including the evolution of magmatism, deformation and associated metamorphism, which affected these latitudes emphasizing the paleogeographic context. are recognized in the Uruguayan territory several orogenic cycles , shorter events associated with the movement of fluid reactivation fault zones, inter alia, that with isotope studies mainly those made ​​in the past 15 years have improved the understanding and evaluating durations different tectonic events and associated phenomena. Structural provinces of the platform South America are characterized according to their origin in cratonic areas , orogenic belts and basins sedimentary . Cratons represent stable regions consisting of Precambrian rocks . During cycles orogenic these areas behaved as rigid regions, mobile belts that developed around him and were eroded and exhumed . South America was involved in events amalgamation and breakup of supercontinents during several consecutive orogenic cycles that occurred in the Paleoproterozoic (Atlantis or supercontinent Columbia), Mesoproterozoic (supercontinent Rodinia or paleopangea), Neoproterozoic (western Gondwana) and Carboniferous (Pangaea). Evidence attempt supercontinent Columbia suggests that existed between 1800 and 1500 Ma prior to the period of rapid growth mantle and cortical reorganization. In these latitudes the beam of mafic dikes (1700 Ma) granites with anorogenic (rapakivi) could represent the fragmentation of this supercontinent or episode tafrogénico Stateriano. The geodynamic evolution of the crust during the Late Proterozoic and Paleozoic less involved the formation of two great continents, Laurentia and Gondwana, from fragmentation Rodinia supercontinent that would have formed ca. 1100 Ma and would have dismembered into three fragments between 800 and 600 Ma during the Pan - African orogeny

  12. Late Cenozoic Magmatic and Tectonic Evolution of the Ancestral Cascade Arc in the Bodie Hills, California and Nevada: Insights from Integrated Geologic, Geophysical, Geochemical and Geochronologic Studies

    Science.gov (United States)

    John, D. A.; du Bray, E. A.; Box, S. E.; Blakely, R. J.; Fleck, R. J.; Vikre, P. G.; Cousens, B.; Moring, B. C.

    2012-12-01

    Geologic mapping integrated with new geophysical, geochemical, and geochronologic data characterize the evolution of Bodie Hills volcanic field (BHVF), a long-lived eruptive center in the southern part of the ancestral Cascade arc. The ~700 km2 field was a locus of magmatic activity from ~15 to 8 Ma. It includes >25 basaltic andesite to trachyandesite stratovolcanoes and silicic trachyandesite to rhyolite dome complexes. The southeastern part of the BHVF is overlain by the ~3.9 to 0.1 Ma, post-arc Aurora Volcanic Field. Long-lived BHVF magmatism was localized by crustal-scale tectonic features, including the Precambrian continental margin, the Walker Lane, the Basin and Range Province, and the Mina deflection. BHVF eruptive activity occurred primarily during 3 stages: 1) dominantly trachyandesite stratovolcanoes (~15.0 to 12.9 Ma), 2) coalesced trachydacite and rhyolite lava domes and trachyandesite stratovolcanoes (~11.6 to 9.7 Ma), and 3) dominantly silicic trachyandesite to dacite lava dome complexes (~9.2 to 8.0 Ma). Small rhyolite domes were emplaced at ~6 Ma. Relatively mafic stratovolcanoes surrounded by debris flow aprons lie on the margins of the BHVF, whereas more silicic dome fields occupy its center. Detailed gravity and aeromagnetic data suggest the presence of unexposed cogenetic granitic plutons beneath the center of the BHVF. Isotopic compositions of BHVF rocks are generally more radiogenic with decreasing age (e.g., initial Sr isotope values increase from ~0.7049 to 0.7061), which suggests progressively greater magma contamination by crustal components during evolution of the BHVF. Approximately circular, polygenetic volcanoes and scarcity of dikes suggest a low differential horizontal stress field during BHVF formation. Extensive alluvial gravel deposits that grade laterally into fluvial gravels and finer grained lacustrine sediments and the westerly sourced Eureka Valley Tuff (EVT; ~9.4 Ma) blanket large parts of the BHVF. The earliest sediments

  13. Detrital zircon U-Pb ages and Hf isotopes of Permo-Carboniferous sandstones in central Inner Mongolia, China: Implications for provenance and tectonic evolution of the southeastern Central Asian Orogenic Belt

    Science.gov (United States)

    Chen, Yan; Zhang, Zhicheng; Li, Ke; Yu, Haifei; Wu, Tairan

    2016-03-01

    The tectonic setting of the southeastern Central Asian Orogenic Belt (CAOB) during the Late Paleozoic has been debated for many years. Provenance analysis of Permo-Carboniferous sedimentary rocks can effectively address this issue. In this study, eight sandstone samples were collected for zircon U-Pb and Lu-Hf isotopic analyses combined with petrographic analysis. Framework petrography and zircon morphology suggest that the samples were from recycled orogen of an igneous origin. Carboniferous rocks, with a significant age peak at 432 Ma and εHf (t) values of - 9.0 to 13.6, were mainly derived from Early to Mid-Paleozoic magmatic rocks and deposited in a piedmont zone, namely, the margin of an inland sea. Permian rocks, mostly with age peaks at 445 Ma and/or 280 Ma and εHf (t) values of - 25.2 to 11.4, dominantly originated from a pre-existing Early to Mid-Paleozoic magmatic arc and Late Paleozoic igneous rocks. These rocks formed in restricted basins of the piedmont and intermountain zones. Based on zircon spectral discrimination, sedimentary environmental analysis, and previous studies, this study supports the interpretation that the southeastern CAOB entered stages of extension and rifting during the Late Paleozoic. In the end, this study proposes a tectonic-paleogeographic reconstruction to explain the tectonic evolution of the southeastern CAOB and the exhumation-transportation-deposition processes between the basins and ranges developed in this orogen.

  14. Transient thermal effects in Alpine permafrost

    Directory of Open Access Journals (Sweden)

    J. Noetzli

    2008-04-01

    Full Text Available In high mountain areas, permafrost is important because it influences natural hazards and construction practices, and because it is an indicator of climate change. The modeling of its distribution and evolution over time is complicated by steep and complex topography, highly variable conditions at and below the surface, and varying climatic conditions. This paper presents a systematic investigation of effects of climate variability and topography that are important for subsurface temperatures in Alpine permafrost areas. The effects of both past and projected future ground surface temperature variations on the thermal state of Alpine permafrost are studied based on numerical experimentation with simplified mountain topography. For this purpose, we use a surface energy balance model together with a subsurface heat conduction scheme. The past climate variations that essentially influence the present-day permafrost temperatures at depth are the last glacial period and the major fluctuations in the past millennium. The influence of projected future warming was assessed to cause even larger transient effects in the subsurface thermal field because warming occurs on shorter time scales. Results further demonstrate the accelerating influence of multi-lateral warming in Alpine topography for a temperature signal entering the subsurface. The effects of thermal properties, porosity, and freezing characteristics were examined in sensitivity studies. A considerable influence of latent heat due to water in low-porosity bedrock was only shown for simulations over shorter time periods (i.e., decades to centuries. Finally, as an example of a real and complex topography, the modeled transient three-dimensional temperature distribution in the Matterhorn (Switzerland is given for today and in 200 years.

  15. Les barrages alpins

    Directory of Open Access Journals (Sweden)

    Alain Marnezy

    2009-03-01

    Full Text Available Les barrages-réservoirs de montagne ont été réalisés initialement dans les Alpes pour répondre à la demande d’énergie en période hivernale. Une certaine diversification des usages de l’eau s’est ensuite progressivement développée, en relation avec le développement touristique des collectivités locales. Aujourd’hui, la participation des ouvrages d’Électricité De France à la production de neige de culture représente une nouvelle étape. Dans les régions où les aménagements hydroélectriques sont nombreux, les besoins en eau pour la production de neige peuvent être résolus par prélèvements à partir des adductions EDF. Les gestionnaires de stations échappent ainsi aux inconvénients liés à la construction et à la gestion des « retenues collinaires ». Cette évolution, qui concerne déjà quelques régions alpines comme la haute Maurienne ou le Beaufortin, apparaît comme une forme renouvelée d’intégration territoriale de la ressource en eau.Mountain reservoirs were initially built in the Alps to meet energy needs in the winter. A certain diversification in the uses of water then gradually developed, related to tourism development in the local communities. Today, the use of facilities belonging to EDF (French Electricity Authority to provide water for winter resorts to make artificial snow represents a new phase. By taking water from EDF resources to supply snow-making equipment, resort managers are thus able to avoid the problems related to the construction and management of small headwater dams. This new orientation in the use of mountain water resources already affects a number of alpine regions such as the Upper Maurienne valley and Beaufortain massif and represents a renewed form of the territorial integration of water resources.

  16. Plate tectonics, damage and inheritance.

    Science.gov (United States)

    Bercovici, David; Ricard, Yanick

    2014-04-24

    The initiation of plate tectonics on Earth is a critical event in our planet's history. The time lag between the first proto-subduction (about 4 billion years ago) and global tectonics (approximately 3 billion years ago) suggests that plates and plate boundaries became widespread over a period of 1 billion years. The reason for this time lag is unknown but fundamental to understanding the origin of plate tectonics. Here we suggest that when sufficient lithospheric damage (which promotes shear localization and long-lived weak zones) combines with transient mantle flow and migrating proto-subduction, it leads to the accumulation of weak plate boundaries and eventually to fully formed tectonic plates driven by subduction alone. We simulate this process using a grain evolution and damage mechanism with a composite rheology (which is compatible with field and laboratory observations of polycrystalline rocks), coupled to an idealized model of pressure-driven lithospheric flow in which a low-pressure zone is equivalent to the suction of convective downwellings. In the simplest case, for Earth-like conditions, a few successive rotations of the driving pressure field yield relic damaged weak zones that are inherited by the lithospheric flow to form a nearly perfect plate, with passive spreading and strike-slip margins that persist and localize further, even though flow is driven only by subduction. But for hotter surface conditions, such as those on Venus, accumulation and inheritance of damage is negligible; hence only subduction zones survive and plate tectonics does not spread, which corresponds to observations. After plates have developed, continued changes in driving forces, combined with inherited damage and weak zones, promote increased tectonic complexity, such as oblique subduction, strike-slip boundaries that are subparallel to plate motion, and spalling of minor plates. PMID:24717430

  17. Tectonics of montage

    DEFF Research Database (Denmark)

    Bundgaard, Charlotte

    2013-01-01

    We build in accordance with specific contemporary conditions, defined by production methods, construction and materials as well as ethics, meaning and values. Exactly this relationship between the work as such and the conditions behind its coming into being is a crucial point. The simultaneity of...... creation of meaning forms the core of tectonics. So tectonic thinking is not only about portraying a constructional logic. Tectonics is to create material realities that reveal narrative meaning. Tectonics is to construct with cultural references....

  18. Geochronology, geochemistry, and deformation history of Late Jurassic-Early Cretaceous intrusive rocks in the Erguna Massif, NE China: Constraints on the late Mesozoic tectonic evolution of the Mongol-Okhotsk orogenic belt

    Science.gov (United States)

    Tang, Jie; Xu, Wen-Liang; Wang, Feng; Zhao, Shuo; Li, Yu

    2015-09-01

    This paper presents new zircon and sphene U-Pb ages, biotite and hornblende 40Ar/39Ar ages, Hf isotopic data, and geochemical data for five Mesozoic plutons in the Erguna Massif of NE China. These data are used to constrain the late Mesozoic tectonic evolution of the Mongol-Okhotsk orogenic belt. This new dating, when combined with previously published ages, indicates that the Late Jurassic-Early Cretaceous (J3-K1) intrusive rocks can be subdivided into three stages that represent periods of magmatism during the Late Jurassic (~ 155 Ma), early Early Cretaceous (~ 137 Ma), and late Early Cretaceous (~ 123 Ma). In addition, the rocks have undergone later deformation recorded by peak ages of ~ 137 and ~ 123 Ma. The Late Jurassic and early Early Cretaceous intrusive rocks in the study area are dominantly syenogranites and are either A-type granites or are classified as alkaline series, suggesting that they formed in an extensional environment. The late Early Cretaceous intrusive rocks in this area are generally monzogranitic and were emplaced as dikes in an extensional environment, along with coeval bimodal volcanics. These data, combined with the presence of regional unconformities in the northern part of Hebei Province and western part of Liaoning Province, and the spatial distribution of coeval volcanic rocks in NE China, suggest the Late Jurassic and early Early Cretaceous magmatisms and the early Early Cretaceous deformation in this area occurred in an extensional environment related to the delamination of a thickened part of the crust after closure of the Mongol-Okhotsk Ocean. In comparison, the late Early Cretaceous deformation and magmatism occurred in an extensional environment related to either delamination of the previously thickened crust related to the Mongol-Okhotsk tectonic regime or the subduction of the Paleo-Pacific Plate, or the combined influence of these two tectonic regimes.

  19. Evolutionary ecology of paedomorphosis in the Alpine newt Triturus alpestris

    OpenAIRE

    Denoël, Mathieu

    2003-01-01

    Paedomorphosis, in which individuals retain ancestral characteristics in the adult stage, is widespread in newts and salamanders and is suspected to play an important role in evolution. In some species, paedomorphosis is facultative with some individuals skipping the metamorphic stage. Dimorphic populations of the Alpine newt inhabit a large variety of aquatic habitats such as permanent lakes and temporary ponds. The aim of this study was to determine the benefits of the alternatives in these...

  20. Role of the structural inheritance of the oceanic lithosphere in the magmato-tectonic evolution of Piton de la Fournaise volcano (La Réunion Island)

    OpenAIRE

    Michon, Laurent; Saint-Ange, Francky; Bachelery, Patrick; Villeneuve, Nicolas; Staudacher, Thomas

    2007-01-01

    La Réunion Island is located east of Madagascar, on the eastern rim of the tectonically inactive Mascarene Basin. This island is composed of three shield volcanoes of which only Piton de la Fournaise is currently active. Although the magmatic activity is restricted to Piton de la Fournaise, a scattered seismicity occurs on the whole 200 km wide volcanic edifice and in the underlying oceanic crust. We carried out a multiscale analysis to understand (1) the origin of the seismicity in the geody...

  1. Recent tectonic and morphostructural evolution of Byers Peninsula (Antarctica): insight into the development of the South Shetland Islands and Bransfield Basin

    OpenAIRE

    Alfaro, P.; López-Martínez, J.; Maestro, A.; Galindo-Zaldívar, Jesús; Durán-Valsero, J. J.; Cuchí, J. A.

    2010-01-01

    [EN] Byers Peninsula forms the western extremity of the Livingston Island (Antarctica) in the continental South Shetland Block. This tectonic block is bounded by the South Shetland Trench to the north, the Bransfield back-arc basin to the south, and extends to the South Scotia Ridge on the east. Westwards it is connected to the Antarctic Plate by a broad deformation zone located at the southern end of the Hero Fracture Zone. In Byers Peninsula we analyzed more than 1,200 lineaments, ...

  2. Detrital zircon U-Pb geochronology and stratigraphy of the Cretaceous Sanjiang Basin in NE China: Provenance record of an abrupt tectonic switch in the mode and nature of the NE Asian continental margin evolution

    Science.gov (United States)

    Zhang, Feng-Qi; Chen, Han-Lin; Batt, Geoffrey E.; Dilek, Yildirim; A, Min-Na; Sun, Ming-Dao; Yang, Shu-Feng; Meng, Qi-An; Zhao, Xue-Qin

    2015-12-01

    The age spectra obtained from 505 spots of detrital zircon U-Pb ages of five representative sandstone samples from the Sanjiang Basin in NE China point to a significant change in its provenance during the Coniacian-Santonian. The predominant detrital source for the Sanjiang Basin during the early Cretaceous was the Zhangguangcai Range magmatic belt and Jiamusi Block along its western and southern periphery, whereas it changed in the late Cretaceous to its eastern periphery. The timing of these inferred changes in the detrital source regions and drainage patterns nearly coincide with the age of a regional unconformity in and across the basin. The time interval of non-deposition and unconformity development was coeval with a transitional period between an extensional tectonic regime in the early Cretaceous and a contractional deformation episode in the late Cretaceous. The Sanjiang Basin evolved during this time window from a backarc to a foreland basin. The migration of the coastal orogenic belt and the fold and thrust belt development farther inland during the late Cretaceous marked the onset of regional-scale shortening and surface uplift in the upper plate of a flat (or very shallow-dipping) subduction zone. The stratigraphic record, the detrital source and geochronology of the basinal strata, and the internal structure of the Sanjiang Basin present, therefore, an important record of a tectonic switch in the nature of continental margin evolution of Northeast Asia during the late Mesozoic.

  3. Detrital zircon and apatite fission track data in the Liaoxi basins: Implication to Meso-Cenozoic thermo-tectonic evolution of the northern margin of the North China Craton

    Indian Academy of Sciences (India)

    Yi Yan; Xiaoqiong Hu; Ge Lin; Weiliang Liu; Zhengjiang Song

    2010-08-01

    Detrital zircon and apatite fission track (ZFT and AFT) data of the sandstones collected from the Liaoxi basins served as a significant probe to study the Meso-Cenozoic thermo-tectonic reactivation events in the northern margin of the North China Craton. All sandstones show wide ZFT and AFT age spectrum and most of ZFT and AFT ages are younger than depositional age of respective host rocks, which suggest widespread track resetting of the host rocks in the Liaoxi basins after deposition. This hot geothermal status in the Liaoxi basins deduced from ZFT and AFT data is temporal consistent with the lithospheric evolution of the North China Craton, which implies that the lithosphere under the northern margin of the North China Craton underwent similar thermo-tectonic destruction process as the intracratonic Bohai Sea. The young ZFT peak age, which ranges from ∼50Ma to 20 Ma, to some extend, provides a temporal constraint on the time that lithosphere significantly thinned and following reverse of the Liaoxi basins and uplift of the eastern part of the Yan-Liao Orogenic Belt. Exhumation of 1.5–2 km can be estimated in the eastern part of the Yan-Liao Orogenic Belt since ∼30Ma to 10 Ma.

  4. Comment on: "Geomorpho-tectonic evolution of the Jamaican restraining bend" by Leomaris Domínguez-González, Louis Andreani, Klaus P. Stanek and Richard Gloaguen [Geomorphology, 228 (2015) 320-334

    Science.gov (United States)

    Mitchell, Simon F.; James-Williamson, Sherene; Miller, David J.; Mandal, Arpita

    2016-06-01

    We provide comments on the paper: "Geomorpho-tectonic evolution of the Jamaican restraining bend" by Domínguez-González et al. (2015). The literature review given is lacking in significant elements, particularly recent papers detailing the geology and uplift history of Jamaica. The paper undertakes a GIS analysis of a DEM and produces a drainage network for Jamaica, yet the networks created do not match the actual drainage network of the island. River profiles were extracted using 150 m contours and many of the knickpoints identified are not related to tectonics. The recognition of different erosional (and thus evolutionary) stages does not take into account the differing geology and the different geomorphological processes that were in operation, and the proposed model for the progressive uplift of different parts of Jamaica must therefore be treated with caution. This is particularly the case where their uplift model agrees neither with recent models based on provenance analysis or on the origin of Jamaican bauxite deposits. This paper demonstrates the problems of relying on remote sensing using inadequate datasets, no ground truthing and incomplete consideration of previous research.

  5. Recent advances on the tectonic and magmatic evolution of the Greater Tibetan Plateau: A special issue in honor of Prof. Guitang Pan

    Science.gov (United States)

    Zhu, Di-Cheng; Chung, Sun-Lin; Niu, Yaoling

    2016-02-01

    The Greater Tibetan Plateau, also known in China as the Qinghai-Tibet Plateau or the Qingzang Plateau, is a tectonic amalgamation of numbers of continental collision events from the northwest in the early Paleozoic to the southwest in the Cenozoic (cf. Dewey et al., 1988; Pan et al., 2012; Yin and Harrison, 2000). These collision events resulted in orogenic belts that record the prolonged albeit complex histories of opening and closing of Tethyan ocean basins and associated tectonic and magmatic responses (cf. Chung et al., 2005; Pan et al., 2012; Song et al., 2014; Yin and Harrison, 2000; Zhu et al., 2013, 2015). Although many aspects related to these events have been recently synthesized with elegance by Pan et al. (2012) and Zhu et al. (2013) using data and observations made available since 2000, many scientific questions, such as the duration of oceanic basins, the collisional and accretionary processes of different terranes, the processes responsible for crustal growth, and the mechanisms for economic mineralization, remain underdeveloped and require further investigations with additional data.

  6. La recherche alpine aujourd’hui

    Directory of Open Access Journals (Sweden)

    Jean-Jacques Brun

    2009-06-01

    Full Text Available Alpine research benefits from several international coordination networks, only one of which – ISCAR (the International Scientific Committee on Research in the Alps – works solely in the Alpine arc. The creation of ISCAR is a consequence of the input and involvement of various Alpine partners around the Alpine Convention. Alpine research now aims to promote an integrated vision of Alpine territories focusing on creating and maintaining spatial and temporal networks of sustainable relationships between humans and the other components of the ecosphere. It combines resource usage with conservation of the biological and cultural diversity that makes up the Alpine identity. This article aims to show: (1 how international Alpine research coordination is organised; (2 the role played by the Alpine Convention as a framework of reference for specifically Alpine research; and (3 the role that the ISCAR international commit-tee and the Interreg “Alpine Space” programmes play in uniting research around territorial challenges relating to biodiversity conservation and territorial development.La recherche sur les Alpes bénéficie de plusieurs réseaux de coordination internationaux dont un seul, le comité international recherche alpine (ISCAR, se consacre exclusivement à l’arc alpin. La création de l’ISCAR est une retombée de la mobilisation des divers partenaires alpins autour de la mise en place de la Convention alpine. Aujourd’hui, la recherche alpine vise à promouvoir une vision intégrée des territoires centrée sur la création et le maintien d’un réseau spatial et temporel de relations durables entre les hommes et les autres composantes de l’écosphère. Elle associe étroitement la mise en valeur des ressources et la conservation des diversités biologiques et culturelles qui constituent l’identité alpine. Cet article a pour ambition de montrer : (1 comment s’organise la coordination internationale des recherches sur les

  7. Continental tectonics and continental kinetics

    International Nuclear Information System (INIS)

    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.)

  8. Late cenozoic tectonic and geomorphic evolution of the Patagonian Andes between 42oS and 52oS, southern Chile assessed using fission-track thermochronology

    International Nuclear Information System (INIS)

    Fission-track (FT) analysis has been applied in the Patagonian Andes of southern Chile to assess the late Cenozoic geomorphic and tectonic response of the overriding plate to subduction of the Chile rise active oceanic spreading centre (Thomson et al., 2001). The timing and nature of tectonic uplift and denudation along the southern parts of the major transpression intra-arc Liquine-Ofqui fault (LOF) system have also been investigated (Thomson, 2001, submitted). Results from 130 FT ages (72 zircon and 58 apatite ages) and 39 apatite track length measurements reveal initiation of rapid cooling and denudation at ca. 30 Ma at the western margin of southern continental South America. This was followed by a ca. 200km eastward migration of the locus of maximum denudation to the position of the present day topographic divide between ca. 30 Ma and ca. 12 to 10 Ma. East of the Andean divide less than 3 km of denudation has occurred since the Late Cretaceous. Enhanced denudation is interpreted to be the result of increased tectonic uplift driven by a large increase in convergence rates at ca. 28 to 26 Ma that triggered orographically enhanced precipitation on the west-side of the Patagonian Andes allowing increased erosion by fluvial incision and mass transport processes. The eastward migration of the locus of maximum denudation can be related to either coeval eastward migration of the retro-arc deformation front, the effects of subduction erosion in the overriding plate at the Peru-Chile trench or shallowing of the angle of subduction. Away from the influence of the LOF the process of spreading centre subduction and collision itself coincides with an overall slow-down in denudation rates in the overriding plate most likely caused by a major reduction in the main tectonic force driving tectonic uplift in the upper plate to subduction. In contrast to the Andes south of ca. 46oS, increased cooling and denudation related to transpression induced rock uplift and erosion along

  9. Late Mesozoic to Paleogene stratigraphy of the Salar de Atacama Basin, Antofagasta, Northern Chile: Implications for the tectonic evolution of the Central Andes

    Science.gov (United States)

    Mpodozis, Constantino; Arriagada, César; Basso, Matilde; Roperch, Pierrick; Cobbold, Peter; Reich, Martin

    2005-04-01

    The Salar de Atacama basin, the largest "pre-Andean" basin in Northern Chile, was formed in the early Late Cretaceous as a consequence of the tectonic closure and inversion of the Jurassic-Early Cretaceous Tarapacá back arc basin. Inversion led to uplift of the Cordillera de Domeyko (CD), a thick-skinned basement range bounded by a system of reverse faults and blind thrusts with alternating vergence along strike. The almost 6000-m-thick, upper Cretaceous to lower Paleocene sequences (Purilactis Group) infilling the Salar de Atacama basin reflects rapid local subsidence to the east of the CD. Its oldest outcropping unit (Tonel Formation) comprises more than 1000 m of continental red sandstones and evaporites, which began to accumulate as syntectonic growth strata during the initial stages of CD uplift. Tonel strata are capped by almost 3000 m of sandstones and conglomerates of western provenance, representing the sedimentary response to renewed pulses of tectonic shortening, which were deposited in alluvial fan, fluvial and eolian settings together with minor lacustrine mudstone (Purilactis Formation). These are covered by 500 m of coarse, proximal alluvial fan conglomerates (Barros Arana Formation). The top of the Purilactis Group consists of Maastrichtian-Danian alkaline lava and minor welded tuffs and red beds (Cerro Totola Formation: 70-64 Ma K/Ar) deposited during an interval of tectonic quiescence when the El Molino-Yacoraite Late Cretaceous sea covered large tracts of the nearby Altiplano-Puna domain. Limestones interbedded with the Totola volcanics indicate that this marine incursion advanced westwards to reach the eastern CD slope. CD shortening in the Late Cretaceous was accompanied by volcanism and continental sedimentation in fault bounded basins associated to strike slip along the north Chilean magmatic arc to the west of the CD domain, indicating that oblique plate convergence prevailed during the Late Cretaceous. Oblique convergence seems to have

  10. Petrography and detrital zircon study of late Carboniferous sequences in the southwestern North China Craton: Implications for the regional tectonic evolution and bauxite genesis

    Science.gov (United States)

    Cai, Shuhui; Wang, Qingfei; Liu, Xuefei; Feng, Yuewen; Zhang, Ying

    2015-02-01

    The North China Craton (NCC) has been flanked by the North Qilian and North Qinling arc-accretionary belts to the south and southwest since ∼400 Ma. The part of the NCC to the east of the Alax terrane (E-NCC) experienced a long sedimentary hiatus and tectonic quiescence between the Middle Ordovician and the late Carboniferous. The northern margin of the E-NCC was reactivated and uplifted with contemporaneous volcanism during the late Carboniferous, an event that partly induced the transformation of the E-NCC from an erosional platform to a continental sedimentary basin. However, the factors controlling this transformation are still not fully understood. A series of sedimentary rocks overlying Ordovician carbonates in the southwestern E-NCC contains a lower iron-oxide layer and an upper phyllosilicate layer. Detrital zircons from different parts of the profile, from the base to the top of the two layers, have similar U-Pb ages. These zircons have a minimum age of ca. 300 Ma and a prominent peak at ca. 450 Ma, with subordinate peaks at ca. 1000 and 2500 Ma. The near-identical minimum age for the two layers suggests they were semi-simultaneously deposited in the late Carboniferous after the long hiatus in sedimentation. Detrital zircons with ages of ∼450 Ma have initial Hf isotopic compositions that vary from large negative to elevated positive. These data, together with the trace element compositions of these zircons, indicate that these minerals formed in a continental arc environment. Samples from the upper sedimentary layer contain mica group minerals that are weakly buckled and fractured, and have weathered to form clay minerals, including chlorite and illite. This suggests that the protolith of this sedimentary layer was dominated by mica schist or mica-bearing granitoid that most likely located near the adjoined part between the North Qilian and North Qinling arc-accretionary belts. Detrital zircons with the youngest ages (ca. 300 Ma) were considered to

  11. 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. PMID:22256796

  12. From Flysch to Molasse-Sedimentary and Tectonic Evolution of Late Caledonian-Early Hercynian Foreland Basin in North Qilian Mountains

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Late Caledonian to Early Hercynian North Qilian orogenic belt in northwestern China is an elongate tectonic unit situated between the North China plate in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to Late Silurian shallow marine to tidal flat deposits and the Early and Middle Devonian terrestrial molasse are developed along the corridor Nanshan. The shallowing-upward succession from subabyssal flysch, shallow marine, tidal flat to terrestrial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stage during the Silurian and Devonian time.

  13. The Quaternary N-Apennine tectonics recorded in the Po Basin: stratigraphic and geomorphological evidences along a N-S traverse in Lombardy (Italy)

    Science.gov (United States)

    Bersezio, Riccardo; Zuffetti, Chiara; Cavalli, Emmanuele; Baio, Mariangelo; Cantone, Martino; Inzoli, Silvia; Mele, Mauro; Pavia, Fabrizio; Rigato, Valentina; Rusnighi, Yuri; Rodondi, Cecilia; Sozzi, Samuele

    2016-04-01

    The stratigraphy and geomorphology of the Quaternary Po Basin fill record the tectonic evolution of the foreland shared by Apennine and Alpine mountain ranges. The study of N-S, 3-D cross-sections, orthogonal to the average axial strike of the basin, permits to investigate the interplay between the tectonics of the Apennine fold and thrust belt (the Quaternary southern active range of the basin) and the glacial-related dynamics along the Alpine side (the northern main source of sediments), that drove the evolution of the depositional systems and landscapes of the interposed basin. Here we present a 25-50 Km wide, 3-D cross-section that parallels the Adda river course, connecting the Southern Alps foothills with the northernmost relieves of the Apennines, close to the present-day Po river. The GIS-based work integrates surface geology (1:10.000 mapping) with subsurface correlation of about 1000 borehole data points (20 to >1000 m deep, most ranging between 100-200 m b.g.s.) and geophysical surveys (VES, ERGI, GPR; about 200 data points, maximum investigation depth of about 300 m b.g.s.). Some radiocarbon and OSL age determinations, integrated by micropaleontological and petrographic analyses, brought additional constraints to the available stratigraphic calibration of the tectono-sedimentary evolution. The first release of the 3-D architectural model yields some suggestions: 1) In the Early Pleistocene, the northward propagation of the Apennine blind thrusts shaped the southern and central parts of the basin in a complex pattern of fault-propagation folds and intervening depocentres. The contemporary bulging of the northern Alpine side induced the progressive southward entrenchment and filling of alluvial valleys into the Plio-Pleistocene shallow marine units. A terraced landscape was confined to this northernmost part of the basin. In the depocentre, the coarse-grained depositional systems, fed by the Southern Alps, interfingered with the sands delivered by the

  14. A paradigm shift in stormflow predictions for active tectonic regions with large-magnitude storms: generalisation of catchment observations by hydraulic sensitivity analysis and insight into soil-layer evolution

    Science.gov (United States)

    Tani, Makoto

    2013-11-01

    In active tectonic regions with large-magnitude storms, it is still difficult to predict stormflow responses by distributed runoff models from the catchment properties without a parameter calibration using observational data. This paper represents an attempt to address the problem. A review of observational studies showed that the stormflow generation mechanism was heterogeneous and complex, but stormflow responses there were simply simulated by a single tank with a drainage hole when the stormflow-contribution area was spatially invariable due to the sufficient amount of rainfall supply. These results suggested such a quick inflow/outflow waveform transmission was derived from the creation of a hydraulic continuum under a quasi-steady state. General conditions necessary for the continuum creation were theoretically examined by a sensitivity analysis for a sloping soil layer. A new similarity framework using the Richards equation was developed for specifying the sensitivities of waveform transmission to topographic and soil properties. The sensitivity analysis showed that saturation-excess overland flow was generally produced from a soil layer without any macropore effect, whereas the transmission was derived mainly from the vertical unsaturated flow instead of the downslope flow in a soil layer with a large drainage capacity originated from the macropore effect. Both were possible for the quick transmission, but a discussion on the soil-layer evolution process suggested that an inhibition of the overland flow due to a large drainage capacity played a key role, because a confinement of the water flow within the soil layer might be needed for the evolution against strong erosional forces in the geographical regions. The long history of its evolution may mediate a relationship between simple stormflow responses and complex catchment properties. As a result, an insight into this evolution process and an inductive evaluation of the dependences on catchment properties

  15. The tectonics of Mercury

    International Nuclear Information System (INIS)

    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

  16. Geochemistry and geochronology of Paleozoic intrusions in the Nalati (Narati) area in western Tianshan, Xinjiang, China: Implications for Paleozoic tectonic evolution

    Science.gov (United States)

    Xu, Xue-Yi; Wang, Hong-Liang; Li, Ping; Chen, Jun-Lu; Ma, Zhong-Ping; Zhu, Tao; Wang, Ning; Dong, Yun-Peng

    2013-08-01

    The Nalati (Narati) area in the Chinese western Tianshan is characterized by abundant Paleozoic intrusions, including granites, diorites and gabbros. They are not only indicators of the interaction between crust and mantle, but also useful clues for tracing the tectonic history of the Tianshan Orogen. Most Early Paleozoic granitoids (biotite monzonitic granites and muscovite granites) of this study are from the Yili Block. The biotite monzonitic granites (mixed-source-derived I-type granites) have a zircon U-Pb age of 497.0 ± 5.9 Ma, indicating the time of the subduction of the Terskey Oceanic crust in the Late Cambrian. The 427.2 ± 5.7 Ma Zircon U-Pb age of the S-type muscovite granites let us interpret that these granites may have been formed during the crust thickening process after the collision between the Yili Block and the Nalati Block. In western Tianshan the Late Paleozoic biotite granites, muscovite granites, quartz diorites, biotite monzonitic granites, granodiorites and alkali granites have respectively a LA-ICPMS zircon U-Pb age of 371.8 ± 6 Ma, 357.2 ± 7.5 Ma, 313.9 ± 2.5 Ma and 296.9 ± 2.4 Ma. The biotite granites display I-type geochemical features and are considered to have been derived from a lower continental crust source. The muscovite granites have a pronounced S-type affinity and are considered to have been formed by the partial melting of thickened continental crust after the collision between the Central Tianshan Belt and the South Tianshan Belt. The quartz-diorites are adakite-like and have an I-type affinity, which are considered to have been formed by partial melting of a delaminated lower crust in a post-orogenic extension setting. The granodiorites also show some typical geochemical features of adakite. Their formation is considered to be related to the lower crustal delamination and the ascending of asthenosphere after the collision event. The alkali granites show an A-type granite affinity. They may have been formed in a within

  17. Tectonic-stratigraphic evolution of mini-basins and salt provinces of Espirito Santo Basin-Brazil; Analise da evolucao tectono sedimentar de mini-bacias e provincias de sal da Bacia do Espirito Santo

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira Neto, Walter Dias; Fernandes, Flavio Luis [Petroleum Geoscience Technology Ltda. (PGT), Rio de Janeiro, RJ (Brazil); Mohriak, Webster [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The Espirito Santo Basin integrates the group of basins along the eastern Brazilian continental margin. It is located between 18 deg and 21 deg S, encompassing an area of approximately 220,000 km{sup 2}, onshore and offshore the Espirito Santo State. Its geological limit with the Campos Basin to the south is defined by a Precambrian basement high (Vitoria Arch), and its northern limit with the Mucuri Basin is defined by a geopolitical limit. The study of salt tectonics processes in the Espirito Santo Basin allowed the deformational analysis and interpretation of the chronological evolution of the mini-basins developed between salt diapirs. We observe an intrinsic relationship between halokinesis and creation of subsidence troughs that may be important for trapping hydrocarbon reservoirs, and consequently form oil and gas accumulations in this portion of the basin. This geodynamics evolution of these structures is marked by a strong linkage between salt movement and coeval sedimentation in the interdomal basins, forming structures and stratigraphic traps that may constitute important aspects for the petroleum geology. (author)

  18. Metamorphic evolution of high-pressure-low-temperature rocks from the northern section of the Guatemala Suture Zone: PTt paths and tectonic implications

    Science.gov (United States)

    Flores, K. E.; Hemming, S. R.; Harlow, G. E.; Cai, Y.; Bonnet, G.; Martin, C.; Brueckner, H. K.

    2014-12-01

    The Guatemala Suture Zone (GSZ) is located along the left-lateral strike slip boundary between the North American and Caribbean plates in central Guatemala. This highly tectonized geotectonic unit contains a variety of metamorphic complexes thrusted north and south of the plate boundary. The northern section of the GSZ consists of (a) a serpentinite-matrix mélange that contains high-pressure-low-temperature (HP-LT) rocks, (b) a continental high-grade felsic belt that includes relics of eclogite facies, (c) a low-grade disrupted volcano-sedimentary sequence, and (d) large ultramafic bodies associated with fragments of Cretaceous island arc sequences. Currently, this section of the GSZ is interpreted as the result of subduction-exhumation-collision and obduction in a back-arc basin. However, our new petrochronological study challenges this simple interpretation because multiple metamorphic ages (Sm-Nd, U-Pb and Ar-Ar) and different PT paths are recorded in the HP-LT rocks. Eclogites within the mélange display a polymetamorphic history consisting of a metamorphic peak at 130-125 Ma and ~60 km depth, an early exhumation to the middle section of a subduction channel (~35 km) at 117-116 Ma, a subsequent metamorphic event at amphibolite facies and a final exhumation at ~85 Ma. In contrast, continental eclogites show a younger metamorphic peak of 77-75 Ma at ~80 km depth, and exhumation ages of ~76-66 Ma. Synchronous jadeitite and mica rocks within the mélange yielded crystallization and exhumation ages of ~ 95 Ma and ~77-53 Ma, respectively. These PTt paths reveal a complex history that can be linked to multiple tectonic events during subduction. Ages and PT conditions of eclogites within the mélange suggest an early coupling and storage of eclogitic slices in the subduction channel. Their subsequent record at lower P and higher T may indicate the initiation of continental crust subduction which will have increased the subduction thermal gradient. Continuous

  19. 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...

  20. Seismic monitoring of an Alpine mountain river

    Science.gov (United States)

    Díaz, J.; Ruíz, M.; Crescentini, L.; Amoruso, A.; Gallart, J.

    2014-04-01

    The Canfranc underground laboratory (LSC), excavated under the Central Pyrenees, is mainly devoted to the study of phenomena which needs "cosmic silence." It also hosts a geodynamical facility, named Geodyn, which holds an accelerometer, a broadband seismometer, and two high-resolution laser strainmeters. During the routine processing of the seismic data, we detected an unusual spectral signature in the 2-10 Hz frequency band, which does not correspond to the typical sources of seismic noise and which can also be recognized in the strain records. After checking against meteorological and hydrological data, we can relate those signals to variations in the discharge by the Aragon River, an Alpine-style river in the southern Pyrenees, located about 400 m from the LSC Geodyn facility. Four main episodes have been identified since early 2011, each lasting 1-2 to 6-8 days. Additionally, a limited number of shorter episodes have also been detected. Three types of river-generated seismic events have been identified, related respectively to moderate rainfall, snowmelt, and flooding events associated to severe storms. Each of those types has distinctive characteristics which allow monitoring the hydrological events from the analysis of seismic and deformation data. A few previous studies have already described the seismic noise close to rivers with larger discharge or in small-scale experimental settings, and we are showing here that the so-called "fluvial seismology" can be useful to study the hydrological evolution of Alpine style streams and may have a potential interest for the civil authorities in charge of the management of hydrological basins.

  1. Episodic plate tectonics on Venus

    Science.gov (United States)

    Turcotte, Donald

    1992-01-01

    Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the Moon, Earth, and Mars indicate a mean surface age of 0.5 +/- 0.3 Ga. Another important observation is that 52 percent of the craters are slightly fractured and only 4.5 percent are embayed by lava flows. These observations led researchers to hypothesize that a pervasive resurfacing event occurred about 500 m.y. ago and that relatively little surface volcanism has occurred since. Other researchers have pointed out that a global resurfacing event that ceased about 500 MYBP is consistent with the results given by a recent study. These authors carried out a series of numerical calculations of mantle convection in Venus yielding thermal evolution results. Their model considered crustal recycling and gave rapid planetary cooling. They, in fact, suggested that prior to 500 MYBP plate tectonics was active in Venus and since 500 MYBP the lithosphere has stabilized and only hot-spot volcanism has reached the surface. We propose an alternative hypothesis for the inferred cessation of surface volcanism on Venus. We hypothesize that plate tectonics on Venus is episodic. Periods of rapid plate tectonics result in high rates of subduction that cool the interior resulting in more sluggish mantle convection.

  2. 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 the Vitiaz–

  3. Early Alpine mountain bike events

    OpenAIRE

    Saint-Martin, Jean; Savre, Frédéric; Terret, Thierry

    2013-01-01

    During the 1980s, the diffusion of mountain biking in France underwent its first phase in mountain territories that discovered its socio-economic value. Over and beyond the structural and organisational aspects, the mountain bike also became a favoured medium for technological and social innovation. The aim here is to reflect upon the various underlying stakes of introducing, into Alpine territory, a new physical activity that required a two-wheeled vehicle and had its roots in the spirit and...

  4. Investigation phytochimique de plantes alpines

    OpenAIRE

    Munari, Caroline

    2006-01-01

    As a part of our ongoing investigations of alpine plants from the Valley of Aoste (Italy), the methanol and dichloromethane extracts of 45 plants have been studied from a phytochemical view point. These species grow at altitudes from 2200 to 2700 meters in extreme habitat. Thus, 100 extracts were investigated for their free radical scavenging activity against DPPH and antifungal activities with different tests: against the plant pathogenic fungus Cladosporium cucumerinum by direct bioautograp...

  5. The Voest-Alpine surface miner

    Energy Technology Data Exchange (ETDEWEB)

    1988-08-01

    The Voest-Alpine Surface Miner (VASM) is developed by Voest-Alpine Maschinenbau, Zeltweg, Australia. It is designed to be the excavation machine of an integrated continuous mining system which will cut, load and transfer the material from the face to a continuous haulage system composed of mobile transfer conveyors, shiftable or movable bench conveyors and stationary extendable out-of-the-pit conveyors. Voest-Alpine claims that more efficient and economical solutions in surface mining are provided by this new mining system. This paper also contains a brief description of the Voest-Alpine Pulse Cutting system (VAPCUT) which is a hydraulically activated cutting tool system. 5 figs.

  6. Early Mesozoic paleogeography and tectonic evolution of the western United States: Insights from detrital zircon U-Pb geochronology, Blue Mountains Province, northeastern Oregon

    Science.gov (United States)

    LaMaskin, T.A.; Vervoort, J.D.; Dorsey, R.J.; Wright, J.E.

    2011-01-01

    This study assesses early Mesozoic provenance linkages and paleogeographic-tectonic models for the western United States based on new petrographic and detrital zircon data from Triassic and Jurassic sandstones of the "Izee" and Olds Ferry terranes of the Blue Mountains Province, northeastern Oregon. Triassic sediments were likely derived from the Baker terrane offshore accretionary subduction complex and are dominated by Late Archean (ca. 2.7-2.5 Ga), Late Paleoproterozoic (ca. 2.2-1.6 Ga), and Paleozoic (ca. 380-255 Ma) detrital zircon grains. These detrital ages suggest that portions of the Baker terrane have a genetic affinity with other Cordilleran accretionary subduction complexes of the western United States, including those in the Northern Sierra and Eastern Klamath terranes. The abundance of Precambrian grains in detritus derived from an offshore complex highlights the importance of sediment reworking. Jurassic sediments are dominated by Mesozoic detrital ages (ca. 230-160 Ma), contain significant amounts of Paleozoic (ca. 290, 380-350, 480-415 Ma), Neoproterozoic (ca. 675-575 Ma), and Mesoproterozoic grains (ca. 1.4-1.0 Ga), and have lesser quantities of Late Paleoproterozoic grains (ca. 2.1-1.7 Ga). Detrital zircon ages in Jurassic sediments closely resemble well-documented age distributions in transcontinental sands of Ouachita-Appalachian provenance that were transported across the southwestern United States and modified by input from cratonal, miogeoclinal, and Cordilleran-arc sources during Triassic and Jurassic time. Jurassic sediments likely were derived from the Cordilleran arc and an orogenic highland in Nevada that yielded recycled sand from uplifted Triassic backarc basin deposits. Our data suggest that numerous Jurassic Cordilleran basins formed close to the Cordilleran margin and support a model for moderate post-Jurassic translation (~400 km) of the Blue Mountains Province. ?? 2011 Geological Society of America.

  7. The Palos Verdes Fault offshore Southern California: Late Pleistocene to present tectonic geomorphology, seascape evolution, and slip rate estimate based on AUV and ROV surveys

    Science.gov (United States)

    Brothers, Daniel S.; Conrad, James E.; Maier, Katherine L.; Paull, Charles K.; McGann, Mary; Caress, David W.

    2015-07-01

    The Palos Verdes Fault (PVF) is one of few active faults in Southern California that crosses the shoreline and can be studied using both terrestrial and subaqueous methodologies. To characterize the near-seafloor fault morphology, tectonic influences on continental slope sedimentary processes and late Pleistocene to present slip rate, a grid of high-resolution multibeam bathymetric data, and chirp subbottom profiles were acquired with an autonomous underwater vehicle (AUV) along the main trace of PVF in water depths between 250 and 600 m. Radiocarbon dates were obtained from vibracores collected using a remotely operated vehicle (ROV) and ship-based gravity cores. The PVF is expressed as a well-defined seafloor lineation marked by subtle along-strike bends. Right-stepping transtensional bends exert first-order control on sediment flow dynamics and the spatial distribution of Holocene depocenters; deformed strata within a small pull-apart basin record punctuated growth faulting associated with at least three Holocene surface ruptures. An upper (shallower) landslide scarp, a buried sedimentary mound, and a deeper scarp have been right-laterally offset across the PVF by 55 ± 5, 52 ± 4 , and 39 ± 8 m, respectively. The ages of the upper scarp and buried mound are approximately 31 ka; the age of the deeper scarp is bracketed to 17-24 ka. These three piercing points bracket the late Pleistocene to present slip rate to 1.3-2.8 mm/yr and provide a best estimate of 1.6-1.9 mm/yr. The deformation observed along the PVF is characteristic of strike-slip faulting and accounts for 20-30% of the total right-lateral slip budget accommodated offshore Southern California.

  8. Holocene construction and evolution of the Ganges-Brahmaputra-Meghna delta: the influence of climate, eustasy, and tectonics on stratigraphic architecture and fluvial dynamics

    Science.gov (United States)

    Sincavage, R.; Goodbred, S. L., Jr.; Pickering, J.; Wilson, C.; Patrick, M. G.; Akhter, S. H.; Seeber, L.; Paola, C.; Jean-Louis, G.; Grall, C.

    2015-12-01

    The Ganges-Brahmaputra-Meghna delta (GBMD), an archetypal tidally-influenced deltaic margin, has been the subject of several multi-national, multi-institutional, and interdisciplinary field studies over the past several years, resulting in an unprecedented density of data coverage for stratigraphy, hydrodynamics, and tectonics on a scale previously only found on well-studied delta systems of other types (e.g., Nile, Mississippi, Rhine-Meuse). Using a suite of geochemical, geophysical, and lithologic data extracted from a network of over 400 shallow (sediments suggests the position of the Brahmaputra River was once west of its modern location, following a course along the eastern edge of the Tista Fan and west of the modern confluence with the Ganges. Construction of the modern delta, consisting of a thick (up to 80 m) succession of fluvial and deltaic sediments, was initiated by an intensified summer monsoon, coincident with accommodation generated by rapid sea-level rise following the Younger-Dryas. Sediment delivery has been focused along three pathways associated with antecedent topography inherited from Pleistocene lowstands. Stacked channel sands are the predominant facies within the upper delta, grading to isolated sand lenses in the distal reaches of Sylhet Basin, indicative of a shift from a highly mobile braidbelt to a less mobile distributary system as bedload is extracted to deposition. Episodic avulsions of the Brahmaputra River into Sylhet Basin during the mid-Holocene have been documented using a robust radiocarbon geochronology. The volume of sediment preserved from these events is insufficient to account for the entire sediment budget based on estimates of modern discharge, likely a consequence of both a weakened mid-Holocene monsoon and bypass out of the basin. Rapid (up to 7 mm/yr) subsidence in Sylhet Basin has not acted as an attractor for channel steering during much of the Holocene. Instead, the Brahmaputra has followed the steepest descent

  9. 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....

  10. WAVE TECTONICS OF THE EARTH

    Directory of Open Access Journals (Sweden)

    Tatiana Yu. Tveretinova

    2015-09-01

    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

  11. Structure and evolution of the Sura-Kama strike-slip zone in the Cenozoic (the Volga-Ural anteclise of the East European Platform)

    Science.gov (United States)

    Kolodyazhnyi, S. Yu.

    2015-07-01

    The Sura-Kama zone (SKZ) complicates the central area of the Volga-Ural anteclise and extends sublaterally from the Sura River basin towards the Kama River at a distance of 700-750 km. Based on the analysis of geological-geophysical data and structural studies, a model for the tectonic structure and the evolution of the SKZ is developed. This is a deep tectonic fault that shows the features of long-term polystage development. During the latest Cimmerian-Alpine period of tectonic reactivation, the SKZ represented a zone of strike-slip and consecutive manifestation of early transpressional right-lateral strike-slip dislocations that changed to left-lateral strike-slip displacements under transtension settings as a result of kinematic inversion. Features of the heterogeneous structure of the SKZ are revealed. The segments formed by the system of strike-slip duplexes are alternated along the strike by the principle of rotation-fold and "domino" structures. The particular models of evolution of these segments are proposed by the examples of the widely known Karlin, Tetyushin, and Lower Kama dislocations. It is assumed that kinematic inversion and compression-decompression phenomena on the flanks of the SKZ, as well as the tectonic environments in the area of its dynamic influence were highly important for the development of the processes of migration and redistribution of hydrocarbon components.

  12. Tectonic evolution and chrono-stratigraphy of sediments in Lake Ohrid Basin (Macedonia/Albania) revealed by multichannel seismic and bathymetric data sets

    Science.gov (United States)

    Lindhorst, K.; Krastel, S.; Reicherter, K. R.; Stipp, M.; Wagner, B.; Schwenk, T.

    2012-12-01

    Lake Ohrid located on the Balkan Peninsula is probably the oldest existing lake in Europe and is often referred to as a hotspot of endemic biodiversity. Here we present the analysis of multichannel seismic cross sections and bathymetric data demonstrating the importance of Lake Ohrid as a valuable sedimentary archive within the terrestrial Mediterranean region. According to our data Lake Ohrid formed in two main deformation phases such as a transtensional phase opening up a pull-apart basin in Late Miocene and an extensional phase since the Pliocene leading to the present geometry. The early stage geometry of the basin has a typical rhomboidal shape restricted by two sets of major normal faults. The location of the basin initiation coincides with the greatest depth of the acoustic basement that is now covered by more than 700 m of undisturbed sediments. Numerous faults are present in the northern area offsetting syn-tectonic sediments, thus confirming the hypothesis that Lake Ohrid Basin is still experiencing extension. Seismic stratigraphic interpretation revealed a succession of fluvial deposits overlying the pre-rift basement. The majority of the entire sedimentary infill is interpreted as deep lacustrine sediments. A chrono-stratigraphic scheme developed for undisturbed lacustrine sediments back to an age of 430 kyr indicate that the sediments document glacial and interglacial cycles back to Marine Isotope Stage 12. A refined calculation on the basis of our new data set revealed a limnological age of at least 2 Myr for Lake Ohrid. Mass wasting deposits are widespread in Lake Ohrid at different stratigraphic levels of the basin. Slide deposits, in general are present adjacent to major fault structures suggesting that they are seismically triggered. A mass wasting deposited along the Lini Fault in the NW-part can be linked to the 518 AD earthquake that destroyed the city of Ohrid. The Udenisht Slide Complex (USC) in the southwestern part of the lake is the

  13. Geochemical and tectonic implications on plate-interface evolution achieved from high-pressure ultramafic rocks in mélange settings

    Science.gov (United States)

    Cannaò, E.; Agostini, S.; Scambelluri, M.; Tonarini, S.

    2014-12-01

    Geochemical studies of fluid-mobile elements (FME) joined with B, Sr and Pb isotopic analyses of high-pressure mélanges terranes help constraining tectonic processes and mass transfer during accretion of slab and suprasubduction mantle in plate-interface domains. Here we focus on ultramafic rocks from two plate interface settings: (I) metasediment-dominated mélange (Cima di Gagnone, CdG, Adula Unit), where eclogite-facies de-serpentinized garnet peridotite and chlorite harzburgite lenses are embedded in paraschist; (II) dominated by high-pressure serpentinite (Erro-Tobbio, ET, and Voltri Units, VU, Ligurian Alps). CdG metaperidotite shows low [B], negative δ 11B and high Sr and Pb isotopic ratios. As, Sb loss from metasediment and gain by garnet and chlorite metaperidotite points to exchange between the two systems. Presence of As and Sb in eclogite-facies peridotite minerals and preferential low-T mobility of such elements suggest that exchange was during early subduction burial and prior to eclogitization. Based on high [B], positive δ11B, oxygen and hydrogen isotope, the ET serpentinties were recently interpreted as supra-subduction mantle flushed by slab fluids (Scambelluri & Tonarini, 2012, Geology, 40, 907-910). Their 206Pb/204Pb and 87Sr/86Sr isotope ratios range between 18.300-18.514 and 0.7048-0.7060, respectively. Compared with ET rocks, VU serpentinites have higher As, Sb (up to 1.3 and 0.39 ppm, respectively) and are enriched in radiogenic Sr (up to 0.7105 87Sr/86Sr). This signature reflects interaction with fluids that exchanged with sedimentary rocks, either in outer rise environments or during accretion atop the slab. In the above cases, the serpentinized mantle rocks fingerprint interaction with fluids from different sources, indicating a timing of accretion to plate interface domains. We provide evidence that serpentinized mantle slices of different size and provenance (slab or wedge) accreted to plate interface domains since early subduction

  14. Evolution of magmatism from the uppermost cretaceous to Oligocene, and its relationship to changing tectonic regime, in the Inca de Oro-El Salvador area (Northern Chile)

    International Nuclear Information System (INIS)

    We present geochronological and petrological data for extrusive and intrusive rocks in the Inca de Oro and El Salvador sheets (in prep.), and the Potrerillos (Tomlinson et al., 1999) and Salar de Maricunga sheets (Cornejo et al., 1998), III Region, Chile (26o-27o S). Most of these data were collected as part of the SERNAGEOMIN regional mapping programme. Additionally, we include published data for El Salvador and Potrerillos districts (Cornejo et al., 1997; Marsh et al., 1997; Gustafson et al., 2001). The dataset includes K/Ar, Ar/Ar and U-Pb mineral ages, which have been carefully selected for quality. The area is underlain by Carboniferous-Permian granitic basement rocks, which are covered by Triassic to Early Upper Cretaceous volcanic and sedimentary successions, including both marine and continental sequences (Cornejo et al., 1993). The period studied in this paper includes extrusive and intrusive rocks of Maastrichtian to Oligocene age, which are of particular interest since they record the 'preparation' of the lithosphere prior to, during, and after the mid-Eocene Incaic deformation and associated porphyry copper event. Shortening in the early-upper Cretaceous (95-85Ma; e.g. Mpodozis and Ramos, 1989; Arevalo and Grocott, 2000) deformed large areas of northen Chile, and marked the transition from the dominance of intra-arc extension to that of shortening punctuated by periods of extension. We recognise seven tectono-magmatic periods from the uppermost Cretaceous to Oligocene, comprising a volcanic sedimentary event contemporaneous with an extensional tectonic regime in the Upper Cretaceous, associated with graben formation, followed by an important compressive event at the beginning of the Tertiary. The middle Paleocene was again dominated by voluminous volcanic activity (collapse calderas) in an extensional regime. During the lowest Eocene the magmatic activity in the area shows a gradual transition from pyroxene-bearing to amphibole-bearing lithologies

  15. Melt source and evolution of I-type granitoids in the SE Tibetan Plateau: Late Cretaceous magmatism and mineralization driven by collision-induced transtensional tectonics

    Science.gov (United States)

    Yang, Li-Qiang; Deng, Jun; Dilek, Yildirim; Meng, Jian-Yin; Gao, Xue; Santosh, M.; Wang, Da; Yan, Han

    2016-02-01

    We report new whole-rock geochemical and Sr-Nd-Pb isotope and zircon U-Pb age and Hf isotope data of the Hongshan intrusive suite in the Triassic Yidun Terrane, eastern Tibet. These data allow us to explore the possible causative links between the magmatism and the coeval Cu-Mo mineralization in the region. The Hongshan intrusive rocks have SiO2 of 65.06-73.60 wt.%, K2O of 3.17-6.41 wt.%, and P2O5 of 0.11-0.39 wt.%, enriched in Rb, Th, and U, and depleted in Ba, Sr, P, Ti, Nb, and Eu. These rocks are of high-K calc-alkaline to shoshonite series, showing geochemical signatures of metaluminous to slightly peraluminous I-type granite. Magmatic zircons separated from four samples yielded weighted mean 206Pb/238U ages of 79 ± 0.7 Ma, 78 ± 0.5 Ma, 77 ± 0.8 Ma, and 76 ± 0.8 Ma. Low MgO (0.42-1.47 wt%), low HREE and Y, varying εHf(t) (- 9.5 to - 2.2), and negative εNd(t) (- 7.7 to - 5.8) suggest that magmas of the late Cretaceous Hongshan plutons were most likely generated by partial melting and mixing of ~ 20% juvenile lower crust-derived melts, represented by the ca. 215 Ma basaltic andesite from the southern Yidun Terrane, with ancient basement-derived melts represented by the Baoshan S-type granitic melts from the Zhongza Block. We consider that partial melting processes are capable of removing chalcophile elements (such as Cu) and leaving siderophile metals (such as Mo) as residue in the lower crust of the Yidun Terrane, consequently inducing porphyry Cu-Mo mineralization. This consideration enables us to propose that the Triassic subduction-modified, copper-rich lithosphere was crucial for the giant copper mineralization that occurred in the Yidun Terrane during the late Cretaceous. Lithospheric-scale, transtensional faulting, developed as a result of collision-induced escape tectonics in SE Tibet, triggered asthenospheric upwelling, which in turn caused intra-plate extension and magmatism during the late Cretaceous, forming the Hongshan and coeval I

  16. Uplifted ophiolitic rocks on Isla Gordon, southernmost Chile: implications for the closure history of the Rocas Verdes marginal basin and the tectonic evolution of the Beagle Channel region

    Science.gov (United States)

    Cunningham, W. D.

    1994-04-01

    A succession of mafic rocks that includes gabbro, sheeted dikes and deformed pillow basalts has been mapped in detail on Isla Gordon, southernmost Chile and is identified as an upper ophiolitic complex representing the uplifted floor of the Late Jurassic-Early Cretaceous Rocas Verdes marginal basin. The complex was uplifted, deformed, and regionally metamorphosed prior to the intrusion of an undeformed 90 Ma granodiorite that cuts the complex. The complex appears para-autochthonous, is gently tilted to the northeast and is internally sheared by near-vertical foliation zones. No evidence for obduction was observed although the base of the complex is not exposed. The ophiolitic rocks have been regionally metamorphosed to mid-upper greenschist levels. Isla Gordon is bounded by the northwest and southwest arms of the Beagle Channel, two important structural boundaries in the southernmost Andes that are interpreted to have accommodated north-side-up and left-lateral displacements. Directly north of Isla Gordon is the Cordillera Darwin metamorphic complex that exposes the highest grade metamorphic rocks in the Andes south of Peru. On the north coast of Isla Gordon a volcaniclastic turbidite sequence that is interpreted to have been deposited above the mafic floor is metamorphosed to lower greenschist levels in strong metamorphic contrast to amphibolite-grade othogneisses exposed in Cordillera Darwin only 2 km away across the northwest arm of the Beagle Channel. The profound metamorphic break across the northwest arm of the Beagle Channel and the regional northeast tilt of the ophiolitic complex are consistent with the previously proposed hypothesis that Isla Gordon represents the upper plate to an extensional fault that accommodated tectonic unroofing of Cordillera Darwin. However, limited structural evidence for extension was identified in this study to support the model and further work is needed to determine the relative importance of contractional, extensional and

  17. Experimental Study of Transient Thermal Convection Following a Catastrophic Lithospheric Overturn: Applications to the Tectonic Style, Thermal Evolution and Topography of Venus

    Science.gov (United States)

    Robin, C. M.; Thayalan, V.; Jellinek, A. M.

    2004-05-01

    The coexistence of dynamically supported highlands and coronae is difficult to reconcile with models of Venusian mantle convection. Coronae are well explained by transient discrete mantle upwellings (thermals), which are characteristic of weak cooling due to the stagnant lid style of convection expected in one-plate planets. In contrast, topographic highlands such as Atla, Beta and Themis Regio are better explained by persistent axisymmetric plumes more typical of the Earth's mantle, which is cooled strongly by subduction and plate tectonics (i.e. mobile lid convection). From the observed crater distribution, it is also inferred that the surface of Venus has a mean age of ~700 Ma. One explanation for this young surface age is that it is a result of a recent and catastrophic resurfacing event. We test a hypothesis that the occurrence of highlands and coronae are a consequence of the style of transient mantle convection driven by sudden overturn of the lithosphere. A series of stagnant lid and mobile lid convection control experiments at thermal equilibrium under conditions appropriate for Venus' mantle are first performed. The mobile lid regime is achieved using a conveyor belt at the cold boundary. Next, we investigate the thermal and temporal characteristics of transitions from steady-state stagnant lid to mobile lid, and from mobile lid to stagnant lid regimes. Using a combination of time-lapse video, shadowgraphs and analyses of time-series of temperature and heat flux data, we identify the qualitative changes in convective regime, the quantitative changes in the heat transfer characteristics of the flows, and the characteristic time scales over which transitions occur. Three regimes are observed: (i) steady-state stagnant lid mode characterized by time-dependent hot (rising) and cold (sinking) thermals; (ii) steady-state mobile-lid mode characterized by active stirring and long-lived plumes; and (iii) a transient mixed mode characterized by the coexistence of

  18. Alpine thermal events in the central Serbo-Macedonian Massif (southeastern Serbia)

    Science.gov (United States)

    Antić, Milorad D.; Kounov, Alexandre; Trivić, Branislav; Wetzel, Andreas; Peytcheva, Irena; von Quadt, Albrecht

    2016-07-01

    The Serbo-Macedonian Massif (SMM) represents a crystalline belt situated between the two diverging branches of the Eastern Mediterranean Alpine orogenic system, the northeast-vergent Carpatho-Balkanides and the southwest-vergent Dinarides and the Hellenides. We have applied fission-track analysis on apatites and zircons, coupled with structural field observations in order to reveal the low-temperature evolution of the SMM. Additionally, the age and geochemistry of the Palaeogene igneous rocks (i.e. Surdulica granodiorite and dacitic volcanic rocks) were determined by the LA-ICPMS U-Pb geochronology of zircons and geochemical analysis of main and trace elements in whole-rock samples. Three major cooling stages have been distinguished from the late Early Cretaceous to the Oligocene. The first stage represents rapid cooling through the partial annealing zones of zircon and apatite (300-60 °C) during the late Early to early Late Cretaceous (ca. 110-ca. 90 Ma). It is related to a post-orogenic extension following the regional nappe-stacking event in the Early Cretaceous. Middle to late Eocene (ca. 48-ca. 39 Ma) cooling is related to the formation of the Crnook-Osogovo-Lisets extensional dome and its exhumation along low-angle normal faults. The third event is related to regional cooling following the late Eocene magmatic pulse. During this pulse, the areas surrounding the Surdulica granodiorite (36 ± 1 Ma) and the slightly younger volcanic bodies (ca. 35 Ma) have reached temperatures higher than the apatite closure temperature (120 °C) but lower than ca. 250 °C. The geochemistry of the igneous samples reveals late- to post-orogenic tectonic setting during magma generation.

  19. Alpine thermal events in the central Serbo-Macedonian Massif (southeastern Serbia)

    Science.gov (United States)

    Antić, Milorad D.; Kounov, Alexandre; Trivić, Branislav; Wetzel, Andreas; Peytcheva, Irena; von Quadt, Albrecht

    2015-11-01

    The Serbo-Macedonian Massif (SMM) represents a crystalline belt situated between the two diverging branches of the Eastern Mediterranean Alpine orogenic system, the northeast-vergent Carpatho-Balkanides and the southwest-vergent Dinarides and the Hellenides. We have applied fission-track analysis on apatites and zircons, coupled with structural field observations in order to reveal the low-temperature evolution of the SMM. Additionally, the age and geochemistry of the Palaeogene igneous rocks (i.e. Surdulica granodiorite and dacitic volcanic rocks) were determined by the LA-ICPMS U-Pb geochronology of zircons and geochemical analysis of main and trace elements in whole-rock samples. Three major cooling stages have been distinguished from the late Early Cretaceous to the Oligocene. The first stage represents rapid cooling through the partial annealing zones of zircon and apatite (300-60 °C) during the late Early to early Late Cretaceous (ca. 110-ca. 90 Ma). It is related to a post-orogenic extension following the regional nappe-stacking event in the Early Cretaceous. Middle to late Eocene (ca. 48-ca. 39 Ma) cooling is related to the formation of the Crnook-Osogovo-Lisets extensional dome and its exhumation along low-angle normal faults. The third event is related to regional cooling following the late Eocene magmatic pulse. During this pulse, the areas surrounding the Surdulica granodiorite (36 ± 1 Ma) and the slightly younger volcanic bodies (ca. 35 Ma) have reached temperatures higher than the apatite closure temperature (120 °C) but lower than ca. 250 °C. The geochemistry of the igneous samples reveals late- to post-orogenic tectonic setting during magma generation.

  20. 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

  1. Planetary Geophysics and Tectonics

    Science.gov (United States)

    Zuber, Maria

    2005-01-01

    The broad objective of this work is to improve understanding of the internal structures and thermal and stress histories of the solid planets by combining results from analytical and computational modeling, and geophysical data analysis of gravity, topography and tectonic surface structures. During the past year we performed two quite independent studies in the attempt to explain the Mariner 10 magnetic observations of Mercury. In the first we revisited the possibility of crustal remanence by studying the conditions under which one could break symmetry inherent in Runcorn's model of a uniformly magnetized shell to produce a remanent signal with a dipolar form. In the second we applied a thin shell dynamo model to evaluate the range of intensity/structure for which such a planetary configuration can produce a dipole field consistent with Mariner 10 results. In the next full proposal cycle we will: (1) develop numerical and analytical and models of thin shell dynamos to address the possible nature of Mercury s present-day magnetic field and the demise of Mars magnetic field; (2) study the effect of degree-1 mantle convection on a core dynamo as relevant to the early magnetic field of Mars; (3) develop models of how the deep mantles of terrestrial planets are perturbed by large impacts and address the consequences for mantle evolution; (4) study the structure, compensation, state of stress, and viscous relaxation of lunar basins, and address implications for the Moon s state of stress and thermal history by modeling and gravity/topography analysis; and (5) use a three-dimensional viscous relaxation model for a planet with generalized vertical viscosity distribution to study the degree-two components of the Moon's topography and gravity fields to constrain the primordial stress state and spatial heterogeneity of the crust and mantle.

  2. Dynamic of an intra-continental orogenic prism: thermo-chronologic (apatite fission tracks) and tectonic evolution of the axial zone and the piedmont of the west-central Pyrenees

    International Nuclear Information System (INIS)

    This work illustrates the application of thermo chronology to the study of the following geologic issue: the tectonic evolution of the Pyrenean oncologic prism. Thermo-chronology gives information on the vertical movements at the scale of geological eras. Thermo-chronology is based on the following principle: the decay of a nucleus gives birth to a daughter nucleus. Above a specific temperature named closure temperature, the daughter element can diffuse outside the system while below the closure temperature, diffusion is not possible. Consequently thermo-chronology can be considered to date the moment when a mineral goes below a a specific closure temperature. Minerals have different closure temperatures and so by using a suite of thermo-chronometers on a single sample, its cooling path through the crust can be reconstructed. This work focuses on apatite fission track (AFT)analysis which is a low temperature thermo-chronometer. In apatites the temperature range between 60 and 120 Celsius degrees corresponds to the partial annealing zone. The spontaneous fission of one U238 nucleus entails the formation of one fission track. The determination of the initial quantity of U238 is based on the natural steady ratio U238/U235 which equals 137.88. The initial quantity of U235 is determined through the neutron irradiation of the sample. The knowledge of the initial quantity of U238 and the number of tracks in the sample allows the dating of the sample. In this work we combine AFT thermo- chronology with a detailed structural analysis to describe vertical movements related to the thrusting system evolution, and to determine the influence of the latter on the sedimentation/burial/exhumation cycle of the syn-orogenic deposits of the southern fore-land basin

  3. Sandstone provenance and tectonic evolution of the Xiukang Mélange from Neotethyan subduction to India-Asia collision (Yarlung-Zangbo suture, south Tibet)

    Science.gov (United States)

    An, Wei; Hu, Xiumian; Garzanti, Eduardo

    2016-04-01

    -sandstone blocks were derived from the central Lhasa block and Gangdese magmatic arc. One group was deposited in the trench and/or on the trench slope of the Asian margin during the early Late Cretaceous, and the other group in a syn-collisional basin just after the onset of the India-Asia collision in the Early Eocene. The largely erosional character of the Asian active margin in the Late Cretaceous is indicated by the scarcity of off-scraped trench-fill deposits and the relatively small subduction complex developed during limited episodes of accretion. The Xiukang Mélange was finally structured in the Late Paleocene/Eocene, when sandstone of both Indian and Asian origin were progressively incorporated tectonically in the suture zone of the nascent Himalayan Orogen.

  4. Tectonics of the Levant fault system

    Science.gov (United States)

    Klinger, Yann

    2015-07-01

    In June 2013, for the second time, an international workshop dedicated to the tectonics of the Levant fault system and the Arabic plate was held in Paris. During two days, this meeting gathered researchers from 19 institutions and 12 countries, with 24 presentations. During this meeting, a large variety of topics were addressed, ranging from new insights into the geodynamics of the Red Sea to earthquake history along the Dead Sea fault. A key point of this meeting was actually to gather contributions focused on the same object, here the Levant fault system, but with different perspectives, to foster new collaborations and research projects. In line with this idea, several presentations were actually dealing with issues related to the palaeoclimate of this specific region, engineering issues about earthquake destructions, or the impact of the Dead Sea active tectonics on the evolution of hominins, aside from general tectonics.

  5. Tectonic Plate Movement.

    Science.gov (United States)

    Landalf, Helen

    1998-01-01

    Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)

  6. Plate tectonics: Metamorphic myth

    Science.gov (United States)

    Korenaga, Jun

    2016-01-01

    Clear evidence for subduction-induced metamorphism, and thus the operation of plate tectonics on the ancient Earth has been lacking. Theoretical calculations indicate that we may have been looking for something that cannot exist.

  7. The role of the Variscan eastern Gondwana-Laurussia/Laurasia boundary in the evolution of the central Mediterranean area

    Science.gov (United States)

    Padovano, M.; Elter, F. M.; Pandeli, E.

    2010-12-01

    The geodynamic evolution of the central Mediterranean area is linked to the interaction between Gondwana and Laurussia/Laurasia plates. The interaction between these plates led to the development of Variscan, Alpine and Apennine Orogenic belts. In spite of the different ages of the orogenic systems, it is possible to hypothesize that their geodynamic evolution was linked to the complex interactions between the eastern boundary of Gondwana and the western boundary of Laurussia/Laurasia. This irregular boundary could have played the role of a pre-existing tectonic barrier which started to develop during the Upper Carboniferous. The kinematic along the boundary was related to a transpressive regime which evolved through a shear zones system (“snake” strike-slip and oblique shear zones). The transpressive environment led to the formation of restraining/releasing bends along the boundary between the two plates. The exhumation of middle/deep crustal rocks by telescoping processes, coeval with the transcurrent movement, occurred in the core of this narrow shear zone. The first occurrences of restraining/releasing bends are related to the Early Visean-Bashkirian (Variscan orogeny). The Variscan eastern boundary between the two colliding plates is characterized by a long-narrow band of HT rocks (East Variscan Shear Zone, EVSZ). From South to North they are: Calabria-Peloritani Terrane (Calabria and Sicily), deep basement of northern Apennines, Sardinia, Corsica, Maures-Tanneron Massif and Alpine Massifs. The same boundary was later reworked by the opening of the Alpine Tethys, dated at the Middle-Upper Jurassic. The opening of the Alpine Tethys led to the separation of the Variscan crust which will represent the future Alpine Massifs (External and Internal Massifs). The closure of the Alpine Tethys and the beginning of the Alpine Orogeny (Late Cretaceous to Eocene) re-assembled the system. The roto-translation of the Sardinia-Corsica and Calabrian-Peloritan blocks

  8. Plate tectonics on Venus

    Science.gov (United States)

    Anderson, D. L.

    1981-01-01

    The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial-style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the Ar-40 abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the earth.

  9. Plate tectonics on Venus

    OpenAIRE

    Anderson, Don L.

    1981-01-01

    The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the ^(40)Ar abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the Earth.

  10. Cretaceous crust-mantle interaction and tectonic evolution of Cathaysia Block in South China: Evidence from pulsed mafic rocks and related magmatism

    Science.gov (United States)

    Li, Bin; Jiang, Shao-Yong; Zhang, Qian; Zhao, Hai-Xiang; Zhao, Kui-Dong

    2015-10-01

    Cretaceous tectono-magmatic evolution of the Cathaysia Block in South China is important but their mechanism and geodynamics remain highly disputed. In this study we carried out a detailed geochemical study on the recently found Kuokeng mafic dikes in the western Fujian Province (the Interior Cathaysia Block) to reveal the petrogenesis and geodynamics of the Cretaceous magmatism. Kuokeng mafic dikes were emplaced in three principal episodes: ~ 129 Ma (monzogabbro), ~ 107 Ma (monzodiorite), and ~ 97 Ma (gabbro). Geochemical characteristics indicate that the monzogabbros were derived from the unmodified mantle source, while gabbros were likely derived from metasomatized mantle by subducted slab (fluids and sediments). Sr-Nd isotope compositions indicate that the parental magmas of the monzodiorites were generated by mixing of enriched, mantle-derived, mafic magmas and felsic melts produced by partial melting of crustal materials. Until the Early Cretaceous (~ 123 Ma), the dominant ancient Interior Cathaysia lithospheric mantle exhibited insignificant subduction signature, indicating the melting of asthenospheric mantle and the consequent back-arc extension, producing large-scale partial melting of the crustal materials under the forward subduction regime of the paleo-Pacific plate. The monzodiorites and gabbros appear to be associated with northwestward subduction of Pacific plate under an enhanced lithospheric extensional setting, accompanying with mantle modification, which triggered shallower subduction-related metasomatically enriched lithospheric mantle to melt partially. After ca. 110 Ma, the coastal magmatic belts formed due to a retreat and rollback of the subducting Pacific Plate underneath SE China in the continental margin arc system.

  11. Lithostratigraphy and tectonics of the eastern part of Veporské vrchy Mts. (Western Carpathians

    Directory of Open Access Journals (Sweden)

    Vojtko Rastislav

    2015-12-01

    Full Text Available The study area is located in the eastern part of Veporské vrchy Mts. and is composed of several palaeo-Alpine tectonic units which are sealed by Cenozoic formations and volcanites. The palaeo-Alpine units differ by degree of metamorphism, deformation, age, and lithological composition. The Vepor Unit, which consists of metamorphosed Variscan crystalline basement and the Permian to Triassic Foederata Group, forms the lowermost structure of the palaeo-Alpine nappe stack in this area. The Vepor Unit is overthrust by (from the bottom to the top: (a newly detected epimetamorphosed Carboniferous deposits of the Furmanec Unit which could by correlated with the Ochtiná Nappe of the Gemer Unit s.l. or with the Nižná Boca Formation of the Choč Nappe; (b the unmetamorphosed “Lower” Muráň Nappe, newly described nappe unit within this area but with not well-known tectonic affinity; and (c the unmetamorphosed Muráň Nappe s.s. of the Silica Unit which represents the uppermost portion of the palaeo-Alpine nappe pile. Post-nappe Upper Eocene to Oligocene remnants of sedimentary deposit together with remnants of the originally voluminous Neogene Vepor Stratovolcano are the youngest features of geological structure of the study area.

  12. Changes in the Alpine environment

    Directory of Open Access Journals (Sweden)

    Philippe Schoeneich

    2009-03-01

    Full Text Available L’évolution de l’environnement alpin au XXIe siècle sera conditionnée par le changement climatique. Celui-ci pourrait conduire à des climats inconnus à ce jour dans les Alpes, avec comme conséquence une crise environnementale majeure et durable. Face à ces défis, les financements de recherche restent insuffisants pour la recherche appliquée aux milieux de montagne. Les financements nationaux privilégient souvent la recherche polaire au détriment des hautes altitudes, alors que les financements de type Interreg prennent insuffisamment en compte les besoins de recherche fondamentale, préalable nécessaire à l’élaboration de scénarios. Une évolution se dessine depuis deux ou trois ans vers des projets en réseau à l’échelle alpine. Le présent article fait le point sur les principaux enjeux qui attendent la recherche environnementale alpine et sur la capacité des programmes de recherche à répondre aux besoins. La première partie sur les changements climatiques est fondée sur les rapports récents : rapport de synthèse IPCC 2007 (IPCC 2007, rapport IPCC sur l’Europe (Alcamo et al. 2007, rapport de synthèse du programme ClimChAlp (Prudent-Richard et al., 2008. On y trouvera des bibliographies complètes et circonstanciées. La deuxième partie se base sur une analyse des appels d’offres récents ou en cours, et des projets soumis et financés.The way the Alpine environment will evolve in the 21st century depends upon climate change. This could lead to climates never before seen in the Alps, resulting in a major and lasting environmental crisis. In the face of these challenges, funding is still insufficient for specialised research on mountain environments. State funding often prioritises polar research at the expense of high altitude areas, whereas funding schemes from bodies such as Interreg do not sufficiently address the need for fundamental research, which is nevertheless a necessary first step prior to

  13. An interpretation of the metamorphic history of the Alpine Schist, northern Westland

    International Nuclear Information System (INIS)

    is further constrained independent information about the tectonics of the region and by the timing of the growth of the syn-mylonitic rim zone 5. Based on a depth of formation estimate of 40 km (from geobarometry for the outermost edge) and uplift to the surface by the present day, zone 5 is interpreted to have formed prior to c. 6 Ma. The maximum age for zone 4 is probably less than 40 Ma, as this is when the Alpine Fault inception is thought to occur [Sutherland et al. 1999]. Arguably this age could be younger than 25 Ma, as movement between the Pacific and Australian plates was small from 40-25 Ma [Sutherland 1995, 1999]. Results obtained for these garnets indicate dyschronous prograde garnet growth from the core to rim of the garnets. Further, these results indicate that the peak of Alpine Schist metamorphism for this section of the Southern Alps occurred at c. 595 degrees C and c. 10.5 kbar, synchronous with development of the mylonitic foliation at c. 6 Ma. For other garnet bearing samples of this study, well constrained geothermobarometry and chemical zoning studies show garnet growth has occurred since the development of the alpine foliation, with garnets first forming in samples with high whole-rock MnO (>0.30%) at c. 400 degrees C and c. 6 kbar. A separate episode of garnet growth that is interpreted based on textural evidence to predate the development of the alpine foliation is seen in rare (two) samples from the biotite zone of the Alpine Schist. These garnets record a moderately high P/T metamorphic signature, suggesting that they formed during a different event to that in which the cores of the large polyphase garnets that formed during extension at 98 Ma. Inclusion trails in biotite and plagioclase porphyroblasts suggest that growth of these moderately high P/T garnets occurred coeval with the growth of at least some biotite and plagioclase. Detailed whole-rock analyses identify the Aspiring Lithological Association, occurring with metabasites within

  14. Inevitability of Plate Tectonics on Super-Earths

    CERN Document Server

    Valencia, Diana; Sasselov, Dimitar D

    2007-01-01

    The recent discovery of super-Earths (masses less or equal to 10 earth-masses) has initiated a discussion about conditions for habitable worlds. Among these is the mode of convection, which influences a planet's thermal evolution and surface conditions. On Earth, plate tectonics has been proposed as a necessary condition for life. Here we show, that super-Earths will also have plate tectonics. We demonstrate that as planetary mass increases, the shear stress available to overcome resistance to plate motion increases while the plate thickness decreases, thereby enhancing plate weakness. These effects contribute favorably to the subduction of the lithosphere, an essential component of plate tectonics. Moreover, uncertainties in achieving plate tectonics in the one earth-mass regime disappear as mass increases: super-Earths, even if dry, will exhibit plate tectonic behaviour.

  15. Palaeoproterozoic tectonic evolution of the Alto Tererê Group, southernmost Amazonian Craton, based on field mapping, zircon dating and rock geochemistry

    Science.gov (United States)

    Lacerda Filho, J. V.; Fuck, R. A.; Ruiz, A. S.; Dantas, E. L.; Scandolara, J. E.; Rodrigues, J. B.; Nascimento, N. D. C.

    2016-01-01

    New geochemical and geochronological U-Pb and Sm-Nd data from amphibolites of the Alto Tererê Group, which are of Palaeoproterozoic age, are presented. The amphibolites are exposed in the central-eastern portion of the Rio Apa Block, southern Amazonian Craton, Mato Grosso do Sul, Brazil, and are composed of hornblende, plagioclase, quartz, biotite, cummingtonite and epidote. The amphibolites are subdivided into three lithofacies: (i) thinly banded amphibolites (metabasalts), (ii) coarse- and medium-grained amphibolites with relic subophitic texture (metagabbros), and (iii) amphibolites with relic cumulate texture (metapyroxenites). Chemical data also suggest the subdivision of the amphibolites into three different types. These rocks yield a U-Pb zircon age of 1768 ± 6 Ma and are therefore older than rocks of part of the Rio Apa Complex. Their Sm-Nd model ages range between 2.89 and 1.88 Ga, and their ɛNd (T) values range between -3.40 and + 3.74. Chemical analyses of these rocks indicate SiO2 concentrations between 45.23 and 50.65 wt.%, MgO concentrations between 4.34 and 8.01 wt.%, TiO2 concentrations between 0.91 and 1.74 wt.%, weakly fractionated rare-earth element (REE) patterns with mild depletion in heavy REEs, enrichment in large-ion lithophile elements (LILEs) and high-field-strength element (HFSEs), negative Nb, Ta and Co anomalies, positive Ba and Pb anomalies, low Ce concentrations, high Rb/Y ratios and low Th/La and Hf/Sm ratios. These features reflect metasomatism of the mantle wedge produced by sediments from the subducted plate. Various degrees of melting mark the evolution of the parent basic magmas, although subordinate crustal contamination may also have occurred. The geochemical signature of the amphibolites corresponds to that of tholeiitic basalts generated in an extensional back-arc-basin environment. The deposition in the basin apparently ceased during the first episode of compression and deformation at approximately 1.68 Ga, and the main

  16. 3D decompaction and sequential restoration: a tool to quantify sedimentary and tectonic control on elusive Quaternary structures

    Science.gov (United States)

    D'Ambrogi, Chiara; Emanuele Maesano, Francesco

    2015-04-01

    the Po Basin provided a set of detailed pictures that show the topography and the evolution of the infilling at different point during time. As a matter of fact the resulting 3D surfaces describe the basin configuration and the changes and migration of regional depocentres controlled by thrust activity up to the Pleistocene but also allow to highlight the interference of active tectonic and sedimentation in the central portion of the Po basin, an area considered less affected by the main structures (e.g. the Emilia and Ferrara-Romagna arcs). In the analysis of this structure also the foreland tilting has been subtracted from the topography resulting after unfolding and decompaction, for the 6 time intervals; we obtained a residual signal related to the growing anticline, and the uplift rate of the structure during its Pleistocene evolution. The project GeoMol is co-funded by the Alpine Space Program as part of the European Territorial Cooperation 2007-2013. The project integrates partners from Austria, France, Germany, Italy, Slovenia and Switzerland and runs from September 2012 to June 2015. Further information on www.geomol.eu

  17. Strain weakening enables continental plate tectonics

    OpenAIRE

    Gueydan, Frédéric; Précigout, Jacques; Montesi, Laurent G.J.

    2014-01-01

    International audience Much debate exists concerning the strength distribution of the continental lithosphere, how it controls lithosphere-scale strain localization and hence enables plate tectonics. No rheological model proposed to date is comprehensive enough to describe both the weakness of plate boundary and rigid-like behaviour of plate interiors. Here we show that the duality of strength of the lithosphere corresponds to different stages of microstructural evolution. Geological const...

  18. 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 (observed earthquake mechanisms, which shows that intraplate earthquakes serve to release stress accumulated through long-term plate interactions.

  19. Asynchronous evolution of the isotopic composition and amount of precipitation in north China during the Holocene revealed by a record of compound-specific carbon and hydrogen isotopes of long-chain n-alkanes from an alpine lake

    Science.gov (United States)

    Rao, Zhiguo; Jia, Guodong; Li, Yunxia; Chen, Jianhui; Xu, Qinghai; Chen, Fahu

    2016-07-01

    Both the timing of the maximum East Asian summer monsoon (EASM) intensity in monsoonal China and the environmental significance of the Chinese stalagmite oxygen isotopic record (δ18O) have been debated. Here, we present a ca. 120-year-resolution compound-specific carbon (δ13C) and hydrogen (δD) isotopes of terrestrial long-chain n-alkanes extracted from a well-dated sediment core from an alpine lake in north China. Our δ13C data, together with previously reported pollen data from a parallel core, demonstrate a humid mid-Holocene from ca. 8-5 ka BP. Assuming that the climatic humidity of north China is an indicator of the EASM intensity, then the maximum EASM intensity occurred in the mid-Holocene. Our δD data reveal a similar long-term trend to the δ18O record from nearby Lianhua Cave, indicating that the synchronous δD and δ18O records faithfully record the δD and δ18O of precipitation, respectively. The most negative δD and δ18O values occur in the early-mid Holocene, from ca. 11-5 ka BP. This contrast in the timing of isotopic variations demonstrates a complex relationship between the isotopic composition of precipitation and precipitation amount, or EASM intensity. Further comparisons indicate a possible linkage between the precipitation amount in north China and the west-east thermal gradient in the equatorial Pacific. In addition, the temperature of the moisture source area may play an important role in determining the isotopic composition of precipitation in monsoonal China.

  20. Inevitability of Plate Tectonics on Super-Earths

    OpenAIRE

    Valencia, Diana; O'Connell, Richard J.; Sasselov, Dimitar D.

    2007-01-01

    The recent discovery of super-Earths (masses less or equal to 10 earth-masses) has initiated a discussion about conditions for habitable worlds. Among these is the mode of convection, which influences a planet's thermal evolution and surface conditions. On Earth, plate tectonics has been proposed as a necessary condition for life. Here we show, that super-Earths will also have plate tectonics. We demonstrate that as planetary mass increases, the shear stress available to overcome resistance t...

  1. On volcanism and thermal tectonics on one-plate planets

    Science.gov (United States)

    Solomon, S. C.

    1978-01-01

    For planets with a single global lithospheric shell or 'plate', the thermal evolution of the interior affects the surface geologic history through volumetric expansion and the resultant thermal stress. Interior warming of such planets gives rise to extensional tectonics and a lithospheric stress system conductive to widespread volcanism. Interior cooling leads to compressional tectonics and lithospheric stresses that act to shut off surface volcanism. On the basis of observed surface tectonics, it is concluded that the age of peak planetary volume, the degree of early heating, and the age of youngest major volcanism on the one-plate terrestrial planets likely decrease in the order Mercury, Moon, Mars.

  2. Tectonic Characteristics and Evolution of Meso-Cenozoic of Sun Basin in North Huanghai Sea%北黄海太阳盆地中新生代构造特征与演化研究*

    Institute of Scientific and Technical Information of China (English)

    董军; 曹脊翔; 李斌; 赵莉萍; 李凯

    2013-01-01

      通过对北黄海太阳盆地二维地震资料重新处理解释,系统研究了地层分布及断裂发育,建立了盆地断裂分布格局及构造样式;首次发现太阳盆地中生代发育两个沉积中心:一个位于北部木星拗陷西南部沿盆地西部两条边界断层分布,另一个位于南部天王拗陷中部;结合地层和钻井资料分析了断裂活动期次和特征,揭示中—新生代构造演化经历了3个阶段:晚侏罗世及早白垩世张扭到压扭阶段(燕山运动期);古近纪早期继续压扭抬升、中期张扭、晚期区域挤压抬升阶段(早喜马拉雅运动期);新近纪到第四纪区域沉降阶段(晚喜马拉雅运动期)。为进一步油气勘探工作提供了有价值的参考。%  By re-processing the 2D seismic data,the layer distribution and fault system of Sun Basin are analyzed in this paper and the construction pattern of fault system in the basin is built. Two sedimentation centers are first discovered,Jupiter Depres-sion sedimentation center and Uranus Depression sedimentation center,respectively. According to layer and logging data,the tectonic evolution of Meso-Cenozoic has gone through Yanshan movement and the early and late Himalayan movement. The three evolution phases are as follows:(1)transtension to compression torsion in Yanshan movement period of late Jurassic to early Cretaceous;(2)continuing compression torsion of early Paleogene,transtension of middle Paleogene,press and uplift of late Paleogene in Himalayan movement period,3) regional subsiding in Neogene and Cenozoic. The results provide valuable reference for further work of petroleum exploration.

  3. Experience with the Alpine Breaker Line Support

    Energy Technology Data Exchange (ETDEWEB)

    Habnicht, H.; Halbmayer, C.

    1989-01-01

    The Alpine Breaker Line Support is new, mechanised support equipment for stabilising the caving edge during depillaring operations. A short discussion is presented of some panel geometry variations used, and of performance data achieved. 5 figs.

  4. Tectonic Vocabulary & Materialization

    DEFF Research Database (Denmark)

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

    2015-01-01

    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. On...... 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...

  5. SERVICE QUALITY ANALYSIS - HOTEL ALPIN (POIANA BRASOV)

    OpenAIRE

    MADAR ANCA; NEACȘU NICOLETA ANDREEA

    2013-01-01

    Hotel Alpin was built in 1971 in Poiana Brasov resort and has a 4 star quality ranking at the moment with the apart hotel having a 5 stars ranking. At the moment in the tourism market the service quality and client satisfaction are very important for being successful. This paper is analyzing through market research, clients’ satisfaction towards the service quality provided by Hotel Alpin. The purpose of this research is to validate the reputation of the hotel.

  6. SERVICE QUALITY ANALYSIS - HOTEL ALPIN (POIANA BRASOV

    Directory of Open Access Journals (Sweden)

    MADAR ANCA

    2013-12-01

    Full Text Available Hotel Alpin was built in 1971 in Poiana Brasov resort and has a 4 star quality ranking at the moment with the apart hotel having a 5 stars ranking. At the moment in the tourism market the service quality and client satisfaction are very important for being successful. This paper is analyzing through market research, clients’ satisfaction towards the service quality provided by Hotel Alpin. The purpose of this research is to validate the reputation of the hotel.

  7. Genèse des séquences sédimentaires du Crétacé supérieur des Aurès (Algérie). Rôle de l'eustatisme, de la tectonique, de la subsidence: une mise au pointSedimentary sequences in the Upper Cretaceous of Aures Mountains (Algerie). Eustatsy, tectonics and subsidence: a development.

    Science.gov (United States)

    Herkat, Missoum; Delfaud, Jean

    2000-06-01

    The Upper Cretaceous of Aurès has been studied using a sedimentological approach to characterize the sequential organisation and deposits distribution in the basin. The sequential chain which was observed has been correlated to eustatic cycles defined on a global scale. Palaeogeographic reconstruction shows a basin with its south margin corresponding to a proximal platform domain with essentially carbonate deposits and toward the northeast, marly sedimentation of pelagic nature. The influence of NW-SE to WNW-ESE accidents on sedimentation control has been found preponderant. Therefore a system of tilted blocks toward the south characterizes a large part of the basin. The subsidence evolution through Upper Cretaceous is marked by a recovery of a tectonic distension during some phases (Late Albian and Lower Turonian) and an essentially thermic subsidence during the other periods. Finally some precocious tectonic phases appeared as early as the Santonian-Campanian transition. The evolution of the basin was thus controlled by the drift of the African plate during the expansion of the Atlantic ocean and also the tectonic influence which began to appear in north Alpine domain.

  8. Geochronology (40Ar/39Ar, K-Ar and He-exposure ages of Cenozoic magmatic rocks from Northern Chile (18-22°S: implications for magmatism and tectonic evolution of the central Andes

    Directory of Open Access Journals (Sweden)

    Gerhard Wörner

    2000-12-01

    Full Text Available K-Ar and Ar/Ar ages from magmatic rocks of northern Chile (18-22°S describe duration and extent of the Tertiary and Quaternary magmatic evolution and date major tectonic events in northernmost Chile. This paper summarizes new K-Ar and Ar-Ar mineral and whole rock ages for intrusive rocks from the Precordillera, Tertiary ignimbrites and andesitic stratovolcanoes from the Western Andean Escarpment at 18°S (WARP and the volcanic front. Intrusive rocks of the Precordillera (Quebrada Paguana, Quebrada Blanca, Quebrada Choja, Quebrada Guatacondo, Cerro Chandacolla represent the Cretaceous to Eocene magmatic arc system and gave ages between 45 and 35 Ma. Younger ages on intrusive rocks are invariably caused by deuteric alteration. Ignimbrites of the Putani and Oxaya formations gave Ar-Ar sanidine ages around 24.2 to 24.8 Ma and 22.8 to 19.4 Ma, respectively. Andesitic stratovolcanoes, which directly overlie Oxaya ignimbrites east of the Western Cordillera gave ages of 20.3 Ma (Cordon Quevilque to 9.0 Ma (Cerro Margarita. Samples from the Miocene to Pleistocene arc system on the Chilean Altiplano underlying the volcanoes of the active volcanic front have been dated between 10.5 to ~3 Ma. A widespread ignimbrite can be correlated from the Lauca basin to the Pacific coast and to the east to occurrences of near Pérez. Repeated Ar-Ar sanidine dating of the Lauca-Pérez-ignimbrite resulted in highly concordant ages of 2.71±0.25 Ma, 2.72 Ma±0.01 Ma, and 2.73±0.11 Ma. Rocks from the active chain (Volcanic Cordillera gave ages younger than 0.9 Ma (Volcán Irruputuncu, Volcán Olca, Volcán Aucanquilcha, Volcán Ollagüe, Volcán Poruñita. These new data are used to constrain Miocene stratigraphy and tectonic movements as well as the timing of uplift and sedimentary response at the Western Andean Escarpment within the framework of the tectonic evolution of the Central AndesGeocronología (49Ar/39Ar, K-Ar y edades He de exposición de rocas cenozoicas del

  9. Plate Tectonics on Earth and on Alien Worlds - Novel Insights into Mantle Dynamics

    Science.gov (United States)

    Stamenkovic, V.; Breuer, D.; Seager, S.

    2014-12-01

    We derive the framework of how common assumptions behind parameterized 1D and full convection 2D/3D models, as well as planet mass, interior structure and composition impact the evolution of plate tectonics on Earths and super-Earths. This approach additionally allows us to resolve previous disagreements between groups that studied plate tectonics on super-Earths and to unveil major problems when modeling the thermal evolution of plate tectonics with both 1D and 2D/3D models. How planet properties impact the evolution of plate tectonics is highly sensitive to a planet's initial thermal conditions, the rheology of mantle rock, the scaling of interior heat and yield stress with planet mass, and especially to whether shear or normal stresses drive plate tectonics. Based on the currently most likely model configuration and for planets starting molten, we find that plate tectonics is less likely to occur on super-Earths, for increasing iron and radiogenic heat contents within the mantle, and also with decreasing core to mantle mass fractions. Interestingly, we also find that water within a planet's mantle has a negative impact on plate tectonics and that only surface water can beneficially impact subduction (but not the initiation of plate tectonics). This emphasizes how the distribution and exchange of water between surface and mantle reservoirs are crucial for plate tectonics, and how difficult it is to find positive water-plate tectonics correlations.

  10. The Plate Tectonics Project

    Science.gov (United States)

    Hein, Annamae J.

    2011-01-01

    The Plate Tectonics Project is a multiday, inquiry-based unit that facilitates students as self-motivated learners. Reliable Web sites are offered to assist with lessons, and a summative rubric is used to facilitate the holistic nature of the project. After each topic (parts of the Earth, continental drift, etc.) is covered, the students will…

  11. Cretacic tectonics in Uruguay

    International Nuclear Information System (INIS)

    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.

  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...

  13. 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...

  14. Task 1 quarternary tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Bell, J.W.

    1994-12-31

    Activities on the task of quarternary tectonics for the Yucca Mountain Site investigations are described. Technical topics include: A preliminary reveiw of Bare Mountain Trench; A preliminary detailed lineament map of the Southwestern part of the proposed repository; A discussion on the 1994 Double Spring Flat, Nevada earthquake; and evidence for temporal clustering.

  15. Plains Tectonics on Venus

    Science.gov (United States)

    Banerdt, W. B.; McGill, G. E.; Zuber, M. T.

    1996-01-01

    Tectonic deformation in the plains of Venus is pervasive, with virtually every area of the planet showing evidence for faulting or fracturing. This deformation can be classified into three general categories, defined by the intensity and areal extent of the surface deformation: distributed deformation, concentrated deformation, and local fracture patterns.

  16. Island formation and tectonic processes

    OpenAIRE

    Draper, G

    2011-01-01

    Tectonic processes can form an island in one of two ways. 1. Those processes that cause a rise in water levels and flooding a pre-existing topography, known as tectonic flooding. 2. Those processes that cause uplift of the basin floor to form a topography that emerges above water level, called tectonic emergence.

  17. Active Tectonics in crossroads of an evolving orogen and morphological consequences: Anatolia

    Science.gov (United States)

    Koral, Hayrettin

    2016-04-01

    Anatolia lies in a curved setting of the active Alpine Mountain Range and is located in crossroads of the European and Asian terrains. It is one of the fastest deforming land in the world, manifested by seismicity, characteristic landforms and GPS measurements. Active tectonics in Anatolia provides not only a comparable geological model for the past orogens, but also a laboratory case for morphological consequences of an orogenic processes. Anatolia comprise different tectonic subsettings with its own characteristics. Northern part is influenced by tectonic characteristics of the Black Sea Basin, the Pontides and the Caucasian Range; northwestern part by the Balkanides; eastern-southeastern part by the Bitlis-Zagros suture; and south-southwestern part by the eastern Mediterranean subduction setting. Much of its present tectonic complexity was inherited from the convergence dominant plate tectonic setting of the platelets prior to the Middle-Neogene. Beginning about 11 Ma ago, the deformed and uplifted landmass unable to accommodate further deformation in Anatolia and ongoing tectonic activity gave rise to rearrangement of tectonic forces and westerly translational movements. Formation of major strike-slip faults in Anatolia including the North and East Anatolian Faults and a new platelet called the Anatolian Plate are the consequences of this episode. Such change in the tectonic regime has led to modification of previously-formed landscape, modification and sometimes termination of previously-formed basins. Evidence is present in the Plio-Quaternary stratigraphy, tectonic characteristics and morphology of the well-studied areas. This presentation will discuss active tectonic features of the northwestern, southwestern and eastern Anatolian subsettings and their influence on morphology that is closely related to sites of pre-historical human settlement.

  18. Transient thermal effects in Alpine permafrost

    Directory of Open Access Journals (Sweden)

    J. Noetzli

    2009-04-01

    Full Text Available In high mountain areas, permafrost is important because it influences the occurrence of natural hazards, because it has to be considered in construction practices, and because it is sensitive to climate change. The assessment of its distribution and evolution is challenging because of highly variable conditions at and below the surface, steep topography and varying climatic conditions. This paper presents a systematic investigation of effects of topography and climate variability that are important for subsurface temperatures in Alpine bedrock permafrost. We studied the effects of both, past and projected future ground surface temperature variations on the basis of numerical experimentation with simplified mountain topography in order to demonstrate the principal effects. The modeling approach applied combines a distributed surface energy balance model and a three-dimensional subsurface heat conduction scheme. Results show that the past climate variations that essentially influence present-day permafrost temperatures at depth of the idealized mountains are the last glacial period and the major fluctuations in the past millennium. Transient effects from projected future warming, however, are likely larger than those from past climate conditions because larger temperature changes at the surface occur in shorter time periods. We further demonstrate the accelerating influence of multi-lateral warming in steep and complex topography for a temperature signal entering the subsurface as compared to the situation in flat areas. The effects of varying and uncertain material properties (i.e., thermal properties, porosity, and freezing characteristics on the subsurface temperature field were examined in sensitivity studies. A considerable influence of latent heat due to water in low-porosity bedrock was only shown for simulations over time periods of decades to centuries. At the end, the model was applied to the topographic setting of the Matterhorn

  19. Tectonic evolution of Bransfield Strait, West Antarctica

    Science.gov (United States)

    Barker, Daniel Hugh Njal

    Bransfield Strait is a young (Rocas Verdes basin supports the contention that Bransfield Strait rifting is in a transitional stage between continental/arc rifting and organized sea-floor spreading, and that it is a useful modern analog for the Rocas Verdes basin. Furthermore, it suggests that detachment faulting may be a common feature of backarc basins. Recognition of low-angle detachment faulting and simple-shear extension is essential for estimating basin extension, and the amount of crustal shortening and thickening that may occur during inversion of a basin such as the Rocas Verdes basin.

  20. Alpine radar conversion for LAWR

    Science.gov (United States)

    Savina, M.; Burlando, P.

    2012-04-01

    The Local Area Weather Radar (LAWR) is a ship-born weather radar system operating in X-band developed by the DHI Group to detect precipitation in urban areas. To date more than thirty units are installed in different settings around the world. A LAWR was also deployed in the Alps, at 3883 m a.s.l. on the Kl. Matterhorn (Valais, Switzerland). This was the highest LAWR of the world and it led to the development of an Alpine LAWR system that, besides featuring important technological improvements needed to withstand the severe Alpine conditions, required the development of a new Alpine Radar COnversion Model (ARCOM), which is the main focus of this contribution. The LAWR system is equipped with the original FURUNO fan-beam slotted antenna and the original logarithmic receiver, which limits the radar observations to the video signal (L) withour providing the reflectivity (Z). The beam is 0.95 deg wide and 20 deg high. It can detect precipitation to a max range of 60 km. In order to account for the limited availability of raw signal and information and the specific mountain set-up, the conversion model had to be developed differently from the state-of-the-art radar conversion technique used for this class of radars. In particular, the ARCOM is based on a model used to simulate a spatial dependent factor, hereafter called ACF, which is in turn function of parameters that take in account climatological conditions, also used in other conversion methods, but additionally accounting for local radar beam features and for orographic forcings such as the effective sampling power (sP), which is modelled by means of antenna pattern, geometric ground clutter and their interaction. The result is a conversion factor formulated to account for a range correction that is based on the increase of the sampling volume, partial beam blocking and local climatological conditions. The importance of the latter in this study is double with respect to the standard conversion technique for this

  1. Alpine Groundwater - Pristine Aquifers Under Threat?

    Science.gov (United States)

    Schneider, P.; Lange, A.

    2014-12-01

    Glacier and permafrost retreat are prominent climate change indicators. However, the characteristics of climate and hydrology in mountain areas remain poorly understood relative to lowland areas. Specifically, not much is known about alpine groundwater, its recharge and water quality variations, as these remote reservoirs are rarely monitored. As global temperatures rise, glaciers and permafrost will continue to retreat forming new sediment deposits and changing infiltration conditions in high alpine terrain. Climate change impacts the hydro-chemical composition of alpine waters, accelerates weathering processes, and potentially triggers mobilization of pollutants. Accordingly, we monitored groundwater quantity and quality parameters of an alpine porous aquifer near the Tiefenbach glacier in the Gotthard Massif in Switzerland. The goal of this research was to assess quality and seasonal storage dynamics of groundwater above the timberline (2000 m). To translate hydrological science into an ecosystem service context, we focused on four attributes: Water quantity: observations of groundwater level fluctuations combined with analysis of contributing water sources based on stable isotope analysis to give a quantitative understanding of origin and amount of water, Water quality: groundwater level, groundwater temperature and electrical conductivity were used as proxies for sampling of hydro-chemical parameters with automated water samplers during primary groundwater recharge periods (snowmelt and rainfall events), Location: Alpine terrain above the timberline, especially recharge into/out of an alpine porous aquifer at a pro-glacial floodplain and Date of annual melt (albedo effect) and timing of flow (snow- and icemelt from May to September) and groundwater recharge during the growing season. The study found that the summer groundwater temperatures depend on the date of annual melt and are more sensitive to climate forcing than lowland groundwater temperatures

  2. 40Ar/39Ar and U-Pb Ages and Isotopic Data for Oligocene Ignimbrites, Calderas, and Granitic Plutons, Southern Stillwater Range and Clan Alpine Mountains: Insights into the Volcanic-Plutonic Connection and Crustal Evolution in Western Nevada

    Science.gov (United States)

    John, D. A.; Watts, K. E.; Henry, C.; Colgan, J. P.; Cousens, B.

    2014-12-01

    Calderas in the southern Stillwater Range (SSR) and Clan Alpine Mountains (CAM) were formed during the mid-Tertiary ignimbrite flareup and subsequently tilted (40->90°) by large-magnitude extension. New geologic mapping, geochemistry, and 40Ar/39Ar and SHRIMP U-Pb zircon dating document 2 periods of magmatism resulting in 4 nested calderas and related granitoid plutons in sections up to 10 km thick. The first period included pre-caldera rhyolite lava domes (30(?) Ma), ~5 km of pre- and post-collapse intermediate lavas and rhyolite tuff that filled the Job Canyon caldera (~29.4 to 28.8 Ma), and the >4-5 km thick, geochemically similar IXL pluton (28.9±0.4 Ma) that intruded the Job Canyon caldera. The second period included pre-caldera rhyolite lava domes and dikes (~25.5 Ma) and 3 ignimbrite units in 3 calderas: tuff of the Louderback Mountains (low-silica rhyolite; ≥600 m thick; ~25.2 Ma); tuff of Poco Canyon (high-silica rhyolite; up to 4.3 km thick; 25.27±0.05 Ma); and ≥2000 km3 tuff of Elevenmile Canyon (trachydacite to rhyolite; up to 4.5 km thick; 25.12±0.01 Ma). The composite Freeman Creek pluton (granite, 24.8±0.4 Ma; granodiorite, 25.0±0.2 Ma) and Chalk Mountain rhyolite porphyry (25.2±0.2 Ma) and granite (24.8±0.3 Ma) plutons intruded the Poco Canyon and Elevenmile Canyon calderas. Early (30 Ma) rhyolites have the least radiogenic compositions (Sri~0.7040), whereas other units are relatively homogeneous (Sri~0.7050, ENd~0.0). Oxygen isotope compositions for SSR and CAM calderas are highly variable (d18Oquartz=5.6-8.2‰, d18Osanidine=5.5-7.0‰, d18Ozircon= 4.1-6.3‰), corresponding to a magmatic range of 5.7-7.9‰. U-Pb dating of zircons indicates homogeneous age populations and few/no xenocrysts and antecrysts. These data show that (1) thick plutons (>2-5 km) underlie compositionally and temporally related caldera-filling ignimbrites, (2) caldera-forming cycles are isotopically variable, requiring divergent magmatic sources in relatively

  3. Geochronology and geochemistry of early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China: Implications for the tectonic evolution of the eastern Central Asian Orogenic Belt

    Science.gov (United States)

    Wang, Zhi-wei; Xu, Wen-liang; Pei, Fu-ping; Wang, Feng; Guo, Peng

    2016-09-01

    This paper presents new zircon U-Pb, Hf isotope, and whole-rock major and trace element data for early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China, in order to constrain the early Paleozoic tectonic evolution of the eastern Central Asian Orogenic Belt (CAOB). Zircon U-Pb dating indicates that early Paleozoic magmatic events within the northern Songnen-Zhangguangcai Range Massif (SZM) can be subdivided into four stages: Middle Cambrian (~ 505 Ma), Late Cambrian (~ 490 Ma), Early-Middle Ordovician (~ 470 Ma), and Late Ordovician (460-450 Ma). The Middle Cambrian monzogranites are K-rich, weakly to strongly peraluminous, and characterized by pronounced heavy rare earth element (HREE) depletions, high Sr/Y ratios, low Y concentrations, low primary zircon εHf(t) values (- 6.79 to - 1.09), and ancient two-stage model (TDM2) ages (1901-1534 Ma). These results indicate derivation from partial melting of thickened ancient crustal materials that formed during the amalgamation of the northern SZM and the northern Jiamusi Massif (JM). The Late Cambrian monzonite, quartz monzonite, and monzogranite units are chemically similar to A-type granites, and contain zircons with εHf(t) values of - 2.59 to + 1.78 and TDM2 ages of 1625-1348 Ma. We infer that these rocks formed from primary magmas generated by partial melting of Mesoproterozoic accreted lower crustal materials in a post-collisional extensional environment. The Early-Middle Ordovician quartz monzodiorite, quartz monzonite, monzogranite, and rhyolite units are calc-alkaline, relatively enriched in light REEs (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, Th, and U), depleted in HREEs and high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), and contain zircons with εHf(t) values of - 7.33 to + 4.98, indicative of formation in an active continental margin setting. The Late Ordovician alkali-feldspar granite and rhyolite units have A-type granite affinities that suggest they formed in

  4. Towards a Tectonic Approach

    DEFF Research Database (Denmark)

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

    2015-01-01

    Given the increasing environmental and legislative demands to reduce energy consumption, not only new constructions but also the existing urban fabric is about to change radically in the coming decades. Existing buildings cannot simply be restored but must undergo a transformation to comply with ...... the building envelope as an aesthetic ‘gesture’, this paper discusses the architectural challenges related to energy renovation in a Danish context and tectonic design method as an approach to these challenges in everyday practice....

  5. Tectonics wins AAP Award

    Science.gov (United States)

    AGU's newest journal, Tectonics, won the 1983 award for excellence in journal design and production given by the Association of American Publishers, Inc. (AAP), in the eighth annual professional and scholarly publishing awards competition. Edited by John F. Dewey, the bimonthly journal is a joint publication of AGU and the European Geophysical Society. Paul E. Tapponnier is the European editor and B.C. Burchfiel is the North American editor. The journal is now in its third year of publication.

  6. 温度和海拔对高寒草甸植物种子萌发进化特性的影响%Effects of temperature and altitude on the evolutional characteristics of seed germination in an alpine meadow

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    The effects of temperature, altitude and seed mass on germination were studied. Seed germination characteristics of 524 species (32 families) existing on the eastern edge of Qinghai-Tibet Plateau were investigated. It was found that alternating temperature had a significant effect on germination, and contributed 3.4%of total variation in percentage germination. The mean proportion germination of all species was 78.7%, 83.4% and 91.3%, the mean percentage germination of all species was 36.4%, 40.6% and 47.2% at 5/15◦C, 5/20◦C and 10/25◦C respectively. Both the lowest percentage germination and the lowest proportion germination occurred in 5/15◦C, which indicated that alpine low temperatures had a negative impact on seed germination. It was aslo found that seed germination was strongly related to phylogeny, with the family accounting for 34.9% of total variations in percentage germination. The germination response to temperature among seeds from 10 main families varied significantly. The highest germination occurred in Poaceae (73.6%), and the lowest in Fabaceae(8.2%). The altitude of the origin had a marked effect on the total percentage germination, and contributed 2.3% of total variation in percentage germination. Seeds from a high altitude displayed lower percentage germination. Different from the results of previous studies, we found a significant negative relationship between seed mass and percentage germination. The seeds from a high altitude were heavier than those from a low altitude, which had a beneficial effect on seed germination. The temperature of a high altitude region was lower than that of a low altitude, which had an adverse effect on seed germination. Both would affect seed germination characteristics.%  选择青藏高原东部高寒草甸的32科524种植物种子,探讨了温度、海拔与种子大小对种子萌发特性的影响.研究结果表明变温极显著地影响种子萌发,能够解释萌发率变异的3.4%.在5/15◦C

  7. Modelling photochemistry in alpine valleys

    Directory of Open Access Journals (Sweden)

    G. Brulfert

    2005-01-01

    Full Text Available Road traffic is a serious problem in the Chamonix Valley, France: traffic, noise and above all air pollution worry the inhabitants. The big fire in the Mont-Blanc tunnel made it possible, in the framework of the POVA project (POllution in Alpine Valleys, to undertake measurement campaigns with and without heavy-vehicle traffic through the Chamonix and Maurienne valleys, towards Italy (before and after the tunnel re-opening. Modelling is one of the aspects of POVA and should make it possible to explain the processes leading to episodes of atmospheric pollution, both in summer and in winter. Atmospheric prediction model ARPS 4.5.2 (Advanced Regional Prediction System, developed at the CAPS (Center for Analysis and Prediction of Storms of the University of Oklahoma, enables to resolve the dynamics above a complex terrain. This model is coupled to the TAPOM 1.5.2 atmospheric chemistry (Transport and Air POllution Model code developed at the Air and Soil Pollution Laboratory of the Ecole Polytechnique Fédérale de Lausanne. The numerical codes MM5 and CHIMERE are used to compute large scale boundary forcing. This paper focuses on modelling Chamonix valley using 300-m grid cells to calculate the dynamics and the reactive chemistry which makes possible to accurately represent the dynamics in the Chamonix valley (slope and valley winds and to process chemistry at fine scale. The summer 2003 intensive campaign was used to validate the model and to study chemistry. NOy according to O3 reduction demonstrates a VOC controlled regime, different from the NOx controlled regime expected and observed in the nearby city of Grenoble.

  8. Modelling photochemistry in alpine valleys

    Directory of Open Access Journals (Sweden)

    G. Brulfert

    2005-03-01

    Full Text Available Road traffic is a serious problem in the Chamonix Valley, France: traffic, noise and above all air pollution worry the inhabitants. The big fire in the Mont-Blanc tunnel made it possible, in the framework of the POVA project (POllution in Alpine Valleys, to undertake measurement campaigns with and without heavy-vehicle traffic through the valley, towards Italy (before and after the tunnel re-opening. Modelling in POVA should make it possible to explain the processes leading to episodes of atmospheric pollution, both in summer and in winter.

    Atmospheric prediction model ARPS 4.5.2 (Advanced Regional Prediction System, developed at the CAPS (Center for Analysis and Prediction of Storms of the University of Oklahoma, enables to resolve the dynamics above a complex terrain.

    This model is coupled to the TAPOM 1.5.2 atmospheric chemistry (Transport and Air POllution Model code developed at the Air and Soil Pollution Laboratory of the Ecole Polytechnique Fédérale de Lausanne.

    The numerical codes MM5 and CHIMERE are used to compute large scale boundary forcing.

    Using 300-m grid cells to calculate the dynamics and the reactive chemistry makes possible to accurately represent the dynamics in the valley (slope and valley winds and to process chemistry at fine scale.

    Validation of campaign days allows to study chemistry indicators in the valley. NOy according to O3 reduction demonstrates a VOC controlled regime, different from the NOx controlled regime expected and observed in the nearby city of Grenoble.

  9. Caribbean tectonics and relative plate motions

    Science.gov (United States)

    Burke, K.; Dewey, J. F.; Cooper, C.; Mann, P.; Pindell, J. L.

    1984-01-01

    During the last century, three different ways of interpreting the tectonic evolution of the Gulf of Mexico and the Caribbean have been proposed, taking into account the Bailey Willis School of a permanent pre-Jurassic deep sea basin, the Edward Suess School of a subsided continental terrain, and the Alfred Wegener School of continental separation. The present investigation is concerned with an outline of an interpretation which follows that of Pindell and Dewey (1982). An attempt is made to point out ways in which the advanced hypotheses can be tested. The fit of Africa, North America, and South America is considered along with aspects of relative motion between North and South America since the early Jurasic. Attention is given to a framework for reconstructing Caribbean plate evolution, the evolution of the Caribbean, the plate boundary zones of the northern and southern Caribbean, and the active deformation of the Caribbean plate.

  10. Snow, ice and water in alpine regions

    International Nuclear Information System (INIS)

    This article takes a look at how climate change will have a deep impact on alpine regions. The findings discussed at a conference organised by the Swiss Hydrologic Commission are presented and discussed. Flooding incidents that occurred 'once in a century' are now becoming more frequent and were considered at the conference as being an indicator of climate change. Changing hydrological factors are also discussed and the influence of climate factors in alpine regions on the water quantities in the rivers are looked at. Also, the spontaneous emptying of glacial lakes as has already happened in Switzerland and the consequences to be drawn from such incidences are discussed.

  11. 塔里木盆地色力布亚断裂带变形特征和演化史%Deformation and tectonic evolution of the Selibuya fault zone in Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    姚文倩; 汤良杰; 谢大庆; 杨勇; 蒋华山; 张宇航; 余腾孝; 曹自成

    2013-01-01

    The Selibuya fault zone separates the Maigaiti Slop and the Bach Uplift in the Tarim Basin ,and its structural styles and tectonic evolution Fault zoneis related to some extent with the evolution of Bachu and Keping .Referring to the latest data of drilling ,logging and 2D-seismic interpretation ,we proposed that the previous defined Selibuya Fault zone be divided into two fault zones including Selibuya and Yasongdi .On sectional view ,the former mainly features in basement-involved high-angle thrust extrusion and consists ,together with the early Piqiang fault on Keping uplift ,Piqiang-Selibuya fault zone ,while the later is a superimposed thrust fault resulted from the superimposition of the SW-dipping shallow thrust fault of cap rock slipping type and the NE-dipping deep basement-involved thrust fault .On plane view ,the Selibuya fault zone recognized in this paper can be divided into a north segment and a south segment .The whole Selibuya fault zone are characterized by high-angle deep thrust and positive flower structures .The south segment of this fault zone cuts upward into the Neogene and Quaternary ,leading to the weak folding of the Neogene and Quaternary and the associated local decollement along the Paleogene cap rock .Combined with the evolution of Selibuya and the regional evolution of Ba-chu and Keping ,it is believed that Selibuya fault zone went through mainly four main stages:the Late Caledonian , the Late Hercynian,the Early-Middle Hymalayan,and Late Hymalayan.%色力布亚断裂带为塔里木盆地麦盖提斜坡与巴楚隆起两个构造单元间的边界断裂带,其构造样式和构造演化与巴楚地区及柯坪地区的形成演化具有一定的相关性。结合最新的钻井、测井以及二维地震资料解释,提出了原来的色力布亚断裂带可分为两个断裂带。剖面上主要表现为基底卷入高角度逆冲挤压断裂样式和正花状走滑断裂样式,与柯坪隆起上的皮羌

  12. HP-LT metamorphism in Elba Island: Implications for the geodynamic evolution of the inner Northern Apennines (Italy)

    Science.gov (United States)

    Bianco, Caterina; Brogi, Andrea; Caggianelli, Alfredo; Giorgetti, Giovanna; Liotta, Domenico; Meccheri, Marco

    2015-11-01

    The inner Northern Apennines belt (i.e., northern Tyrrhenian Sea and Tuscany) is an Alpine chain affected by high-P metamorphic conditions during its evolution. Although Elba Island is structurally located close to the Adria-Europe suture zone, for several authors it represents a sector of the orogen affected by low-P metamorphism. The involvement of Elba Island tectonic units in high-P metamorphism was only suspected for the sparse presence of phengitic white mica in the metasedimentary rocks. This paper presents the first clear evidence of high-P and low-T metamorphism found in metabasite rocks embedded in the Cretaceous calcschist of eastern Elba Island. Mineral composition of metabasite includes Gln + Cpx + Ep + Ab + Act + Qtz + Ilm ± Ti-oxide ± Spn and is indicative of a former equilibration in the epidote blueschist subfacies and subsequent retrogression in the greenschist facies. Recorded metamorphic conditions are P = 0.9-1.0 GPa and T = 330-350 °C. Tectonic discrimination using immobile elements in the metabasite does not point to an oceanic setting. As a consequence, the metasedimentary succession containing metabasite is explained as belonging to the Tuscan continental domain and not to the Ligurian-Piedmont Ocean, as previously interpreted. Our results have two significant implications: (i) it is confirmed and strengthened that the tectonic stacking of the Elba Island units did not occur in a low-pressure context; (ii) Elba Island is now completely reconciled in the tectonic and metamorphic evolution of the inner Northern Apennines.

  13. Stress field sensitivity analysis in a sedimentary sequence of the Alpine foreland, northern Switzerland

    Science.gov (United States)

    Hergert, T.; Heidbach, O.; Reiter, K.; Giger, S. B.; Marschall, P.

    2015-05-01

    The stress field at depth is a relevant parameter for the design of subsurface constructions and reservoir management. Yet the distortion of the regional stress field due to local-scale features such as sedimentary and tectonic structures or topography is often poorly constrained. We conduct a stress sensitivity analysis using 3-D numerical geomechanical modelling with an elasto-plastic material law to explore the impact of such site-specific features on the stress field in a sedimentary sequence of the Swiss Alpine foreland. The model's dimensions are 14 x 14 x 3 km3 and it contains 10 units with different mechanical properties, intersected by two regional fault zones. An initial stress state is established involving a semi-empirical relationship between the ratio of horizontal to vertical stress and the overconsolidation ratio of argillaceous sediments. The model results indicate that local topography can affect the stress field significantly to depths greater than the relief contrasts at the surface, especially in conjunction with horizontal tectonic loading. The complexity and frictional properties of faults are also relevant. The greatest variability of the stress field arises across the different sedimentary units. Stress magnitudes and stress anisotropy are much larger in stiffer formations such as massive limestones than in softer argillaceous formations. The stiffer formations essentially carry the load of the far-field forces and are therefore more sensitive to changes of the boundary conditions. This general characteristic of stress distribution in the stiff and soft formations is broadly maintained also with progressive loading towards the plastic limit. The stress field in argillaceous sediments within a stack of formations with strongly contrasting mechanical properties like in the Alpine foreland appears to be relatively insensitive to changes in the tectonic boundary conditions and is largely controlled by the maximum stiffness contrast with respect

  14. Dynamics of Tectonic Plates

    CERN Document Server

    Pechersky, E; Sadowski, G; Yambartsev, A

    2014-01-01

    We suggest a model that describes a mutual dynamic of tectonic plates. The dynamic is a sort of stick-slip one which is modeled by a Markov random process. The process defines a microlevel of the dynamic. A macrolevel is obtained by a scaling limit which leads to a system of integro-differential equations which determines a kind of mean field systems. Conditions when Gutenberg-Richter empirical law are presented on the mean field level. These conditions are rather universal and do not depend on features of resistant forces.

  15. The Tectonic Practice

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due

    The thesis investigates tectonics as a contemporary architectural practice and how changes in the building industry create challenges to this manner of creating architecture. The challenge focused on is the specialization in the building industry between architects and engineering consultants which...... 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...

  16. Quarternary tectonics, Task 1

    Energy Technology Data Exchange (ETDEWEB)

    Bell, J.W.

    1993-09-30

    Activities conducted for the evaluation of the geology and seismotectonics stability of Yucca Mountain as a potential site for the underground disposal of high-level radioactive wastes continued. Tasks concerned with quaternary tectonics include: scheduling of photography of Little Skull Mountain area; the collection and dating of rock varnish samples from the 1932 Cedar Mountain earthquake area for carbon 14 AMS and cation-ratio analysis; collection of samples for thermoluminescence dating from the 1932 Cedar Mountain earthquake area; mapping of the northern area of Crater Flat; and surveying of the May 17, 1993 Eureka the Valley earthquake area.

  17. Volcanological constraints of Archaean tectonics

    Science.gov (United States)

    Thurston, P. C.; Ayres, L. D.

    1986-01-01

    Volcanological and trace element geochemical data can be integrated to place some constraints upon the size, character and evolutionary history of Archean volcanic plumbing, and hence indirectly, Archean tectonics. The earliest volcanism in any greenhouse belt is almost universally tholeitic basalt. Archean mafic magma chambers were usually the site of low pressure fractionation of olivine, plagioclase and later Cpx + or - an oxide phase during evolution of tholeitic liquids. Several models suggest basalt becoming more contaminated by sial with time. Data in the Uchi Subprovince shows early felsic volcanics to have fractionated REE patterns followed by flat REE pattern rhyolites. This is interpreted as initial felsic liquids produced by melting of a garnetiferous mafic source followed by large scale melting of LIL-rich sial. Rare andesites in the Uchi Subprovince are produced by basalt fractionation, direct mantle melts and mixing of basaltic and tonalitic liquids. Composite dikes in the Abitibi Subprovince have a basaltic edge with a chill margin, a rhyolitic interior with no basalt-rhyolite chill margin and partially melted sialic inclusions. Ignimbrites in the Uchi and Abitibi Subprovinces have mafic pumice toward the top. Integration of these data suggest initial mantle-derived basaltic liquids pond in a sialic crust, fractionate and melt sial. The inirial melts low in heavy REE are melts of mafic material, subsequently melting of adjacent sial produces a chamber with a felsic upper part underlain by mafic magma.

  18. 雪峰山早中生代构造演化:构造学和年代学分析木%Tectonic evolution of the Early Mesozoic Xuefengshan belt:Insights from structural analysis and geochronological constraints

    Institute of Scientific and Technical Information of China (English)

    褚杨; 林伟; Michel Faure; 王清晨

    2011-01-01

    In the center of the South China Block,in Hunan Province, the Xuefengshan Belt providesa well-exposed example of intracontinental orogens. Detail field observations indicate that the Xuefengshan Belt can be divided into: ( 1 ) the Western Outer Zone,characterized by km-scale box-fold structure; (2) the Central Xuefengshan Zone, where the dip of the cleavage surface exhibits a fan-like pattern, separated from the Western Outer Zone by the Xuefengshan Main Thrust,the most deformed and metamorphosed region in this belt; (3)and the Eastern Zone,deformed mainly in the brittle-ductile level, characterized by top-to-the-NW structures and also some back-folding structures. The Xuefengshan Belt results of polyphase deformation: D1,characterized by a widespread top-to-the-NW ductile shearing. D2 corresponds to a SE-directed back thrusting and folding event. D3 consists of upright folds with vertical cleavage and lineation. The tectonic evolution of the Early Mesozoic Xuefengshan Belt is possibly originated by the continental subduction in response to the northwest directed subduction of the Pacific plate.%雪峰山主体地处湖南省境内,位于华南板块的中心区域,是一条典型的陆内造山带.通过详细的野外地质观察,我们将其分为3个构造单元:西部外区,主要以大型箱状褶皱为主;中部区,与西部区以主逆冲断层相分隔,劈理发育呈扇状,是雪峰山构造带的核心区域,也是变质级别最深、变形最强的区域;东部区,变形集中在脆韧性区域之上,以极性北西构造为主,并有反向构造发育.研究区经历了3期构造变形:D1为上部指向北西的韧性剪切,广泛发育于整个区域;D2代表了一期反向褶皱一逆冲构造事件;D3则以水平挤压为主,形成了直立的褶皱、劈理和线理.雪峰山的构造演化表明华南板块东南缘古太平洋板块向北西方向的俯冲可能引发了早中生代的陆内俯冲造山过程.

  19. Mixed type sulfide deposits in Northern Tunisia, regenerated in relation to paleogeography and tectonism

    Science.gov (United States)

    Slim-Shimi, Najet; Tlig, Said

    1993-04-01

    Analyses were made of sulfur isotopes and major and minor element (Fe, Pb, Zn, Cu, Hg, Cd, Bi, S, As, Tl, Sb, …) contents of a well characterized suite of minerals from ore deposits wether associated with vulcanism, metamorphism, Cretaceous sedimentary facies or Tertiary detrital-rich and molasse deposits. Paleogeography, tectonism and ore genesis are closely related: periods characterized by intense deformation (Middle and Upper Jurassic, Middle and Upper Cretaceous and Oligocene-Miocene) enable deposition of polymetallic syngenetic/epigenetic sulfide deposits; in contrast, during tectonically less active periods, the ore genesis appear to be clearly restricted. Mineralogy, sulfur isotopes, abundant sulfosalts and minor element abundances (Ag, Hg, Cd, Bi) point to important remobilization and repetitive mineralization stages the latest of which postdated the Alpine orogeny. The origin of Upper Cretaceous mineralizations hosted in local black shales, is thought to be found in metals brought up from deep-seated, eventually endogenic hydrothermal fluids. These deposits may later act as a transition base metal source for Tertiary deposits, during and after the Alpine tectogenesis, along with the new-additions of metals from presumably endogenic sources. Even though admixtures of diagenetic connat fluids somehow hampered geochemical information, it is concluded that ore deposits from Northern Tunisia are mixed-type and closely related to paleogeographic environments and tectonical history of the region. The previous prominent role of Triassic salt diapirism as a metallogenic factor is discussed but not confirmed.

  20. Comment on: Alam Akhtar, Ahmad Shabir, Sultan Bhat, M., Ahmad Bashir, 2015. Tectonic evolution of Kashmir basin in northwest Himalayas. Geomorphology doi: 10.1016/j.geomorph.2015.03.025

    Science.gov (United States)

    Shah, A. A.

    2016-01-01

    Alam et al. (2015) have challenged the classic piggyback tectonic model for the development of Kashmir basin, NW Himalaya. However, all the evidence shown is completely contrary to the geologic, tectonic, structural, seismologic, geodetic, and geomorphic data of previous works. A perfectly planar major (~ 165 km) dextral strike-slip fault has been mapped; however, with such planar geometry, any strike-slip fault cannot produce a pull-apart basin because such basins are characteristic features of step-overs and linkage fault geometries. And the Horsetail structures are impossible for a major planar strike-slip fault geometry that is proposed by the authors. The recent geodetic data of the Kashmir basin strongly refutes the pure strike-slip model. Therefore, the structures, geomorphology, geology, and kinematics associated with typical dextral strike-slip fault geometry completely contradict to what has been proposed by Alam et al. (2015).

  1. Active tectonics of the Andes

    Science.gov (United States)

    Dewey, J. F.; Lamb, S. H.

    1992-04-01

    Nearly 90 mm a -1 of relative plate convergence is absorbed in the Andean plate-boundary zone. The pattern of active tectonics shows remarkable variations in the way in which the plate slip vector is partitioned into displacement and strain and the ways in which compatibility between different segments is solved. Along any traverse across the plate-boundary zone, the sum of relative velocities between points must equal the relative plate motion. We have developed a kinematic synthesis of displacement and strain partitioning in the Andes from 47°S to 5°N relevant for the last 5 Ma based upon: (1) relative plate motion deduced from oceanic circuits giving a roughly constant azimuth between 075 and 080; (2) moment tensor solutions for over 120 crustal earthquakes since 1960; (3) structural studies of deformed Plio-Pleistocene rocks; (4) topographic/geomorphic studies; (5) palaeomagnetic data; and (6) geodetic data. We recognize four neotectonic zones, with subzones and boundary transfer zones, that are partitioned in different ways. These zones are not coincident with the 'classic' zones defined by the presence or absence of a volcanic chain or differences in finite displacements and strains and tectonic form; the long-term segmentation and finite evolution of the Andes may not occur in constantly defined segments in space and time. In Segment 1 (47°-39°S), the slip vector is partitioned into roughly orthogonal Benioff Zone slip with large magnitude/large slip-surface earthquakes and both distributed dextral shear giving clockwise rotations of up to 50° and dextral slip in the curved Liquine-Ofqui Fault System giving 5°-10° of anticlockwise fore-arc rotation. In Segment 2 (39°-20°S), the slip vector is partitioned into Benioff Zone slip roughly parallel with the slip vector, Andean crustal shortening and a very small component of dextral slip, including that on the Atacama Fault System. Between 39° and 34°S, a cross-strike dextral transfer, which deflects

  2. Paleogene palaeogeography and basin evolution of the Western Carpathians, Northern Pannonian domain and adjoining areas

    Science.gov (United States)

    Kováč, Michal; Plašienka, Dušan; Soták, Ján; Vojtko, Rastislav; Oszczypko, Nestor; Less, György; Ćosović, Vlasta; Fügenschuh, Bernhard; Králiková, Silvia

    2016-05-01

    The data about the Paleogene basin evolution, palaeogeography, and geodynamics of the Western Carpathian and Northern Pannonian domains are summarized, re-evaluated, supplemented, and newly interpreted. The presented concept is illustrated by a series of palinspastic and palaeotopographic maps. The Paleogene development of external Carpathian zones reflects gradual subduction of several oceanic realms (Vahic, Iňačovce-Kričevo, Szolnok, Magura, and Silesian-Krosno) and growth of the orogenic accretionary wedge (Pieniny Klippen Belt, Iňačovce-Kričevo Unit, Szolnok Belt, and Outer Carpathian Flysch Belt). Evolution of the Central Western Carpathians is characterized by the Paleocene-Early Eocene opening of several wedge-top basins at the accretionary wedge tip, controlled by changing compressional, strike-slip, and extensional tectonic regimes. During the Lutetian, the diverging translations of the northward moving Eastern Alpine and north-east to eastward shifted Western Carpathian segment generated crustal stretching at the Alpine-Carpathian junction with foundation of relatively deep basins. These basins enabled a marine connection between the Magura oceanic realm and the Northern Pannonian domain, and later also with the Dinaridic foredeep. Afterwards, the Late Eocene compression brought about uplift and exhumation of the basement complexes at the Alpine-Carpathian junction. Simultaneously, the eastern margin of the stretched Central Western Carpathians underwent disintegration, followed by opening of a fore-arc basin - the Central Carpathian Paleogene Basin. In the Northern Hungarian Paleogene retro-arc basin, turbidites covered a carbonate platform in the same time. During the Early Oligocene, the rock uplift of the Alpine-Carpathian junction area continued and the Mesozoic sequences of the Danube Basin basement were removed, along with a large part of the Eocene Hungarian Paleogene Basin fill, while the retro-arc basin depocentres migrated toward the east

  3. A paradigm shift in stormflow predictions for active tectonic regions with large-magnitude storms: generalisation of catchment observations by hydraulic sensitivity analysis and insight into soil-layer evolution

    OpenAIRE

    Makoto Tani

    2013-01-01

    In active tectonic regions with large-magnitude storms, it is still difficult to predict stormflow responses by distributed runoff models from the catchment properties without a parameter calibration using observational data. This paper represents an attempt to address the problem. A review of observational studies showed that the stormflow generation mechanism was heterogeneous and complex, but stormflow responses there were simply simulated by a single tank with a drainage ho...

  4. A paradigm shift in stormflow predictions for active tectonic regions with large-magnitude storms: generalisation of catchment observations by hydraulic sensitivity analysis and insight into soil-layer evolution

    OpenAIRE

    Tani, Makoto

    2013-01-01

    In active tectonic regions with large-magnitude storms, it is still difficult to predict stormflow responses by distributed runoff models from the catchment properties without a parameter calibration using observational data. This paper represents an attempt to address the problem. A review of observational studies showed that the stormflow generation mechanism was heterogeneous and complex, but stormflow responses there were simply simulated by a single tank with a drainage hole when the sto...

  5. INFLUENCE OF MOTOR ABILITIES ON LEARNING OF ALPINE SKI TECHNIQUE

    Directory of Open Access Journals (Sweden)

    Igor Božić

    2012-12-01

    Full Text Available The research determined influence of motor abilities on alpine ski learning. Moreover, the aim was also to estimate the contribution of some morphological characteristics to acquisition of ski knowledge. At the beginning of the study, participants were tested by tests evaluating balance, agility, explosive and static strength, movement frequency and flexibility. After evaluation of motor abilities, basic morphological characteristics were noted and then participants entered a seven days alpine ski course. Acquired alpine ski knowledge was assessed through demonstration of seven elements of alpine ski technique, by five independent judges. Data analysis showed positive influence of agility on all tested elements of alpine ski technique (traversing, β = .38; β = .26; uphill turn, β = .33; β = .23; basic turn, β = .18; parallel turn, β = .32; short turn, β = .34. Subjects’ results in squat endurance test assessing the static leg strength contribute to learning uphill turn (β = .19, basic turn (β = .35 and parallel turn (β = .27. Test used to measure balance (single leg balance test significantly influences learning of basic elements of alpine ski technique (traversing right, β = .23; traversing left, β = .28; uphill turn to the left, β = .24. Body height has a negative effect on alpine ski learning (β = -0.5, indicating that taller ski beginners tend to have more difficulties during alpine ski learning than shorter alpine ski beginners. According to our results, agility, static leg strength and balance are the motor abilities with the greatest influence on beginners’ alpine ski learning

  6. Tectonic forward modelling of positive inversion structures

    Energy Technology Data Exchange (ETDEWEB)

    Brandes, C. [Leibniz Univ. Hannover (Germany). Inst. fuer Geologie; Schmidt, C. [Landesamt fuer Bergbau, Energie und Geologie (LBEG), Hannover (Germany)

    2013-08-01

    Positive tectonic inversion structures are common features that were recognized in many deformed sedimentary basins (Lowell, 1995). They are characterized by a two phase fault evolution, where initial normal faulting was followed by reverse faulting along the same fault, accompanied by the development of hanging wall deformation. Analysing the evolution of such inversion structures is important for understanding the tectonics of sedimentary basins and the formation of hydrocarbon traps. We used a 2D tectonic forward modelling approach to simulate the stepwise structural evolution of inversion structures in cross-section. The modelling was performed with the software FaultFold Forward v. 6, which is based on trishear kinematics (Zehnder and Allmendinger, 2000). Key aspect of the study was to derive the controlling factors for the geometry of inversion structures. The simulation results show, that the trishear approach is able to reproduce the geometry of tectonic inversion structures in a realistic way. This implies that inversion structures are simply fault-related folds that initiated as extensional fault-propagation folds, which were subsequently transformed into compressional fault-propagation folds when the stress field changed. The hanging wall deformation is a consequence of the decrease in slip towards the tip line of the fault. Trishear angle and propagation-to-slip ratio are the key controlling factors for the geometry of the fault-related deformation. We tested trishear angles in the range of 30 - 60 and propagation-to-slip ratios between 1 and 2 in increments of 0.1. Small trishear angles and low propagation-to-slip ratios produced tight folds, whereas large trishear angles and high propagation-to-slip ratios led to more open folds with concentric shapes. This has a direct effect on the size and geometry of potential hydrocarbon traps. The 2D simulations can be extended to a pseudo 3D approach, where a set of parallel cross-sections is used to describe

  7. The potential for retreating alpine glaciers to alter alpine ecosystems in the Colorado Front Range

    Science.gov (United States)

    Hall, E.; Baron, J.

    2013-12-01

    Glaciers are retreating at an unprecedented rate. In mid-latitude alpine ecosystems the presence of glaciers and rock glaciers govern rates and ecology of alpine and sub-alpine ecosystems. Changes in the thermal environment due to the loss of isothermal habitat and inputs from glacier melt chemistry are altering alpine ecosystems in unpredictable ways. In particular, glacier may be a source of nitrogen that is altering alpine ecosystem dynamics. Loch Vale Watershed (LVWS) located within Rocky Mountain National Park. LVWS contains a surface glacier (Andrew's glacier) and a rock glacier (Taylor's glacier) at the headwater of each of the two drainages within the watershed. We collected precipitation from a National Atmospheric Deposition Site and surface water from multiple alpine lakes and streams during a particularly high and low snow year in the Colorado Front Range. We also sampled stream and lake sediments at each site to analyze the associated microbial community. Concentrations of nitrate and ammonium, relative abundance of amoA (the gene responsible for a key step in the microbial nitrification pathway), and the dual isotope signal to nitrate all point to snow melt as a key deliverer of nitrogen to ecosystems along the Colorado Front Range. However, late summer surface water chemistry is isotopically similar to the chemistry of glacial ice. This suggests that retreating glacier may be an additional source of N to alpine ecosystems and have the potential to alter microbial community composition, biogeochemical rate processes, and ecosystem function. These dynamics are most likely not unique to the Colorado Front Range and should be globally distributed as glaciers continue to retreat in high altitude ecosystems around the world.

  8. The Birimian volcanism in the northeastern Ivory-Coast, evidence for two distinct volcano-tectonic phases in the geodynamical evolution during the Palaeo-Proterozoic; Le volcanisme birimien du nord-est de la Cote-d`Ivoire, mise en evidence de deux phases volcano-tectoniques distinctes dans l`evolution geodynamique du Paleoproterozoique

    Energy Technology Data Exchange (ETDEWEB)

    Pouclet, A.; Vidal, M. [Orleans Univ., 45 (France); Delor, C.; Simeon, Y. [Bureau de Recherches Geologiques et Minieres (BRGM), 45 - Orleans (France); Alric, G.

    1996-12-31

    In the northeastern Ivory-Coast, volcanic formations having different geochemical features are located in the Haute-Comoe volcano-sedimentary Birimian terrains (Palaeo-Proterozoic). They consist of tholeiites belonging to greenstone belts and showing an oceanic magmatic signature, andesitic calc-alkaline lavas interbedded in the sediments of the Haute-Comoe Basin and related to an active margin-type magmatic genesis, and rhyodacitic intrusions spatially and geochemically linked to granitoid plutons. The magmatic characterization, in terms of geotectonic contexts leads to the following scheme: formation of the greenstone belts in a juvenile oceanic context with building of oceanic plateau (2.195 Ga), genesis of granitoid batholites with metamorphose the belts and beget a first continental crust (2.15 Ga), opening of a sedimentary basin in a shear-zone corridor with local production of calc-alkaline volcanism due to heat transfer along a major lithospheric fault (2.15 - 2.10 Ga), shortening of the basin with leucogranite intrusions in the same transcurrent context (2.09 Ga). This geodynamical scheme takes account of the distinction between two major volcano-tectonic phases: a tholeiitic phase with the greenstone belt formation and then, a calc-alkaline phase linked to the structural evolution of the sedimentary basin. This model could be applied to other Ivory-Coast Birimian terrains, but it is necessary to distinguish the volcanics and the sediments belonging to the greenstone belts and those of the basins which were emplaced between the batholiths. (authors). 78 refs., 9 figs., 1 tab.

  9. Carbonate clumped isotope thermometry in continental tectonics

    Science.gov (United States)

    Huntington, Katharine W.; Lechler, Alex R.

    2015-04-01

    Reconstructing the thermal history of minerals and fluids in continental environments is a cornerstone of tectonics research. Paleotemperature constraints from carbonate clumped isotope thermometry have provided important tests of geodynamic, structural, topographic and basin evolution models. The thermometer is based on the 13C-18O bond ordering in carbonates (mass-47 anomaly, Δ47) and provides estimates of the carbonate formation temperature independent of the δ18O value of the water from which the carbonate grew; Δ47 is measured simultaneously with conventional measurements of carbonate δ13C and δ18O values, which together constrain the isotopic composition of the parent water. Depending on the geologic setting of carbonate growth, this information can help constrain paleoenvironmental conditions or basin temperatures and fluid sources. This review examines how clumped isotope thermometry can shed new light on problems in continental tectonics, focusing on paleoaltimetry, basin evolution and structural diagenesis applications. Paleoaltimetry is inherently difficult, and the precision in carbonate growth temperature estimates is at the limit of what is useful for quantitative paleoelevation reconstruction. Nevertheless, clumped isotope analyses have enabled workers to address previously intractable problems and in many settings offer the best chance of understanding topographic change from the geologic record. The portion of the shallow crust residing at temperatures up to ca. 200 °C is important as host to economic resources and records of tectonics and climate, and clumped isotope thermometry is one of the few proxies that can access this critical range with sensitivity to temperature alone. Only a handful of studies to date have used clumped isotopes to investigate diagenesis and other sub-surface processes using carbonate crystallization temperatures or the sensitivity of Δ47 values to a sample's thermal history. However, the thermometer is

  10. Plate Tectonics: A Paradigm under Threat.

    Science.gov (United States)

    Pratt, David

    2000-01-01

    Discusses the challenges confronting plate tectonics. Presents evidence that contradicts continental drift, seafloor spreading, and subduction. Reviews problems posed by vertical tectonic movements. (Contains 242 references.) (DDR)

  11. Serpentinite slices within a tectonic zone at the base of the Juvavic nappe system in the Northern Calcareous Alps (Austria): characterization and origin

    Science.gov (United States)

    Boehm, Katharina; Schuster, Ralf; Wagreich, Michael; Koller, Friedrich; Wimmer-Frey, Ingeborg

    2014-05-01

    The investigated serpentinites are present in an ENE-WSW orientated tectonic zone at the base of Juvavic nappes (Northern Calcareous Alps), situated at the eastern margin of the Eastern Alps (Lower Austria). They form small tectonically squeezed slices, which are embedded in Permotriassic schists and Middle to Upper Triassic limestones. These serpentinites play an important, but not yet understood role in reconstructing Neotethys evolution, Alpine Orogeny and the correlation of Dinarides and Alps. The largest serpentinite body near to Unterhöflein is 400 to 100 meters in size and was investigated by mineralogical (XRD) and petrological/geochemical (XRF) methods. The primary mineral composition is olivine + orthopyroxene + clinopyroxene + chrome spinel. Pseudomorphs of pyroxenes are visible macroscopically, but almost all primary minerals are replaced by serpentine minerals. Former olivine is converted to chrysotile minerals, which show typical reticulate textures, orthopyroxene turned into lizardite pseudomorphs and chrome spinel is almost completely altered to magnetite. Major contents of chrysotile-α, chrysotile-γ and lizardite and minor antigorite, as well as secondary minerals like talc, chlorite and hydrogrossular were identified with XRD. Results from whole rock geochemistry indicate harzburgitic precursor rocks for the serpentinites. According to the low antigorite content, the rocks have only a weak metamorphic imprint and therefore an obduction rather than a subduction history is likely. This leads to the assumption that these serpentinites possibly originate from the Neotethys and not from the Penninic oceanic realm. Further, the tectonic position of the serpentinite slices is in close vicinity to sediments of the Meliata unit which also occur between Juvavic and underlying Tirolic nappe system (Mandl & Ondrejickova, 1993). Additionally, remnants from ophiolite nappes are found reworked into the surrounding Upper Cretaceous Gosau Group. In the latter

  12. The experimental investigation of microcracks nucleation in typical tectonics

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The evolution and nucleation of microcracks in typical tectonics are investigated in the experiment of fracture of marble specimen. The change of state during nucleation of microcracks is observed. The controlling effect of tectonics on evolution of microcracks is analyzed by using the damage mechanics theory. These characteristics can be analogized to kilometer meters as the first effect of earthquake precursors. These studies may be helpful to interpret the foreshock or general foreshock in the moderate or short stage before strong earthquakes. The other physical precursors are second or third effect. The local density of microcracks increasing abruptly may be helpful to interpret the phenomenon that part precursor records appear catastrophic jump. The part out of nucleation where some microcracks heal and the density change reversibly may be helpful to interpret the phenomenon that some precursors records appear reverse change. The area difference of microcracks accumulation and evolution in different part of typical tectonics is studied. This difference may be helpful to interpret the characteristics (including the area) of earthquake preparation of different tectonics, and further to interpret the difference of the precursors between plate edge and intraplate. These differences may be introduced by the scholars with different points of view as to discuss about the existence of precursors before earthquakes. However, when the precursor records are studied, one must notice the geology background in different areas.

  13. In search of transient subduction interfaces in the Dent Blanche-Sesia Tectonic System (W. Alps)

    Science.gov (United States)

    Angiboust, Samuel; Glodny, Johannes; Oncken, Onno; Chopin, Christian

    2014-09-01

    In this paper we study the Alpine metamorphic history of a major tectonic zone which formed during Alpine orogeny, the Dent Blanche Thrust (DBT). This contact, located in the Northern Western Alps, juxtaposes some ophiolitic metasediment-rich remnants of the Liguro-Piemontese ocean (Tsaté Complex) with a composite continental, km-sized complex (Dent Blanche Tectonic System, DBTS) of Adriatic affinity thrusted over the ophiolite. In order to better understand the geodynamic meaning of the DBT region and adjacent units, we have reconstructed the pressure-temperature-time-deformation (P-T-t-d) history of these two units using modern thermobarometric tools, Rb/Sr geochronology, and field relationships. We show that the Tsaté Complex is formed by a stack of km-thick calcschists-bearing tectonic slices having experienced variable maximum burial temperatures between 360 °C and 490 °C at depths of ca. 25-40 km. Associated deformation ages span a range between 37 Ma and 41 Ma. The Arolla gneissic mylonites at the base of the DBTS experienced high-pressure (12-14 kbar), top-to-NW deformation at ca. 450 °C between 43 and 48 Ma. A first age of ca. 58 Ma has been obtained for high-pressure ductile deformation in the Valpelline shear zone, atop Arolla gneisses. Some of the primary, peak metamorphic fabrics have been reworked and later backfolded during exhumation and collisional overprint (ca. 20 km depth, 37-40 Ma) leading to the regional greenschist-facies retrogression which is particularly prominent within Tsaté metasediments. We interpret the Dent Blanche Thrust, at the base of the Arolla unit, as a fossilized subduction interface active between 43 and 48 Ma. Our geochronological results on the shear zone lining the top of the Arolla unit, together with previous P-T-t estimates on equivalent blueschist-facies shear zones cutting the Sesia unit, indicate an older tectonic activity between 58 and 65 Ma. We demonstrate here that observed younger ages towards lowermost

  14. Reply to the comment of Mitchell et al. on "Geomorpho-tectonic evolution of the Jamaican restraining bend" by L. Domínguez-González, L. Andreani, K.P. Stanek and R. Gloaguen [Geomorphology, 228 (2015) 320-334

    Science.gov (United States)

    Domínguez-González, Leomaris; Andreani, Louis; Stanek, Klaus P.; Gloaguen, Richard

    2016-06-01

    We reply to the comments of Mitchell et al. on our paper entitled "Geomorpho-tectonic evolution of the Jamaican restraining bend". The comments contain statements about the methods that need to be balanced. We agree that the interpretation of the modeled drainage network in some karstified parts of the Jamaican island is difficult, but this does not affect the validity of our analysis elsewhere. We consider that our geomorphic analyses (which also include topographic profiles and morphometric maps) are still valid. The view expressed by Mitchell et al. that we used serially developed landscapes to 'date' progressive uplift is an oversimplification of our discussion. We highlighted the differences between the geomorpho-tectonic provinces of Jamaica, and we proposed to explain these differences by a model which involves (1) a westward propagation of the restraining bend and (2) a difference in tectonic styles between the different provinces of Jamaica. Our interpretation does not contradict existing models based on seismotectonic data, provenance analysis or on the origin of Jamaican bauxite. There is a disagreement between James-Williamson et al. (2014), which suggested that central Jamaica was already being uplifted by the end of the Late Miocene, and Domínguez-González et al. (2015), which proposed a Pliocene to present onset of the NE-trending compression toward the SW. However, the timing of the deformation in central and western Jamaica is still poorly constrained and, at this time, any interpretation of the uplift history of central Jamaica should be considered as hypothetical.

  15. 中国东北地区的构造格局与演化:从500 Ma到180 Ma%The Tectonic Framework and Evolution of the NE China:from~500 Ma to ~180 Ma

    Institute of Scientific and Technical Information of China (English)

    周建波; 曾维顺; 曹嘉麟; 韩杰; 郭晓丹

    2012-01-01

    component. This uniformity of U - Pb ages across all crustal blocks in NE China establishes a>l 300 km long Late Pan-African khondalite belt with Pan-African syn-collisional granite, which we named here the 'NE China Pan-African Orogen'. This indicates the blocks of NE China were amalgamated prior to ~500 Ma. contrary to current belief. One scenario is that this amalgamated terrane had a tectonicaffinity to the Siberia craton, once forming part of the Late Pan-African ( ~ 500 Ma) Sayang-Baikal orogenic belt extensively developed around the southern margin of the Siberia craton. This belt was the result of collision between currently unidentified terranes with the Southeastern Angara - Anabar Province at about 500 Ma, where the rocks were deformed and metamorphosed to granulite facies. It appears likely that at sometime after ~450 Ma, the combined NE China blocks rifted away from Siberia and moved southward to form what is now NE China. The combined block collided with the North China craton along the Solonker - XarMoron - Changchun suture zone at~230 Ma rather than in the end -Permian as previously thought. Local rifting at the eastern extremity of the developing Central Asian orogenic belt (CAOB) resulted in the splitting away of the Jiamusi/Khanka(/Bureya) blocks. However, this was only transient and sometime between 210 and 180 Ma, and these were re-united with the CAOB by the onset of Pacific plate subduction, which we named here the "Jilin - Heilongjiang high pressure belt" and forming which has dominated the tectonic evolution of the region since that time

  16. Alpine skiing : injury profile, ACL risk factors and prevention

    OpenAIRE

    Westin, Maria

    2015-01-01

    Alpine skiing is a popular winter sport among children and adolescents. The combination of great physical demands and ever-changing external conditions makes competitive alpine skiing to one of our most complex sports. To reach the highest level of skiing skill, the skier needs to take part in a long and carefully planned physical training in order to improve skiing performance. This often starts when the skier enters a Swedish ski high school. Like other sports, alpine skiing may unfortunate...

  17. Continental tectonics in the aftermath of plate tectonics

    Science.gov (United States)

    Molnar, Peter

    1988-01-01

    It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.

  18. Structural Geology and Tectonics in Marine Science:Perspectives in the Research of Deep Sea and Deep Interior

    Institute of Scientific and Technical Information of China (English)

    LI Sanzhong; YU Shan; JIN Chong; SUO Yanhui; M.Santosh; DAI Liming; LIU Xin; MA Yun; WANG Xiaofei; ZHANG Bingkun

    2012-01-01

    The fields of structural geology and tectonics have witnessed great progress over the last decade and are poised for further expansion in the future.One of the significant breakthroughs is the establishment of the ‘Beyond Plate Tectonics Theory’where a combination of conceptual models and numerical modeling on plume tectonics and plate tectonics has enabled new insights into the structural and tectonic architecture and processes in the deep interior and deep sea.This paper Synthesizes developments of structural geology and tectonics from a macroscopic perspective in deep interior and deep sea.Four key techniques are also reviewed:satellite altimetry for surface structures in deep-sea multi-beam sea-floor mapping;tomography for tectonics of the deep interior;diverse modeling approaches and software for unfolding dynamic evolution;and techniques for HT/HP experiments on material rheology and in situ component measurements.

  19. Stability of alpine meadow ecosystem on the Qinghai- Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    ZHOU Huakun; ZHOU Li; ZHAO Xinquan; LIU Wei; LI Yingnian; GU Song; ZHOU Xinmin

    2006-01-01

    The meadow ecosystem on the Qinghai-Tibetan Plateau is considered to be sensitive to climate change. An understanding of the alpine meadow ecosystem is therefore important for predicting the response of ecosystems to climate change. In this study, we use the coefficients of variation (Cv) and stability (E) obtained from the Haibei Alpine Meadow Ecosystem Research Station to characterize the ecosystem stability. The results suggest that the net primary production of the alpine meadow ecosystem was more stable (Cv = 13.18%) than annual precipitation (Cv = 16.55%) and annual mean air temperature (Cv = 28.82%). The net primary production was insensitive to either the precipitation (E = 0.0782) or air temperature (E = 0.1113). In summary, the alpine meadow ecosystem on the Qinghai- Tibetan Plateau is much stable. Comparison of alpine meadow ecosystem stability with other five natural grassland ecosystems in Israel and southern African indicates that the alpine meadow ecosystem on the Qinghai-Tibetan Plateau is the most stable ecosystem. The alpine meadow ecosystem with relatively simple structure has high stability, which indicates that community stability is not only correlated with biodiversity and community complicity but also with environmental stability. An average oscillation cycles of 3―4 years existed in annual precipitation, annual mean air temperature, net primary production and the population size of consumers at the Haibei natural ecosystem. The high stability of the alpine meadow ecosystem may be resulting also from the adaptation of the ecosystem to the alpine environment.

  20. Glacial reorganization of topography in a tectonically active mountain range

    Science.gov (United States)

    Adams, Byron; Ehlers, Todd

    2016-04-01

    Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns, and not tectonic rock uplift rates. Alpine glaciers drastically altered the relief structure of the Olympic Mountains. The details of these relief changes are recorded in channel profiles as overdeepenings, reduced slopes, and associated knickpoints. We find the position of these relief changes within the orogen is dependent on the position of the Pleistocene ELA. While alpine glaciers overdeepened valleys in regions near the Pleistocene ELA (which has a tendency to increase relief), headward erosion of west and north flowing glacier systems captured significant area from opposing systems and caused drainage divide lowering. This divide lowering reduced relief throughout the range. We demonstrate similar topographic effects recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on

  1. Quaternary Tectonics of The Vitosha Mountain (bulgaria)

    Science.gov (United States)

    Angelova, Dora

    The Vitosha Mt. is a Cretaceous paleovolcano of the central type with complex ge- ological evolution. From a contemporary point of view it has a marked orographic homogeneity, which is connected with its specific evolution during the Neogene and the Quaternary. At the background of intensive vault formation, graben systems from the Maritsa and Strouma fault zones originated in a sharp discordance along its pe- riphery. The vault formation process caused the accumulation of tectonic stresses in different parts of the Vitosha Mt. in the course of time and space. The tectonic stresses provoked the formation of concentric normal faults. Their surface display predeter- mined not only the block disintegration of the structure but also its primary relief. The active mountain formation of Vitosha was controlled by the Pernik and Vladaya fault zones, and by the Vitosha, Zheleznitsa, Matnitsa and Chuipetlovo fault beams during the Quaternary. The Pliocene-Pleistocene boundary was accompanied by active ver- tical tectonic deformations. As a result of pulse tectonic movements and subsequent deformations along the above mentioned structures, a global re-arrangement of the Vladaiska and Strouma River basins took place in the region of the Vladaya village and to the south of the Chuipetlovo village. The age of these events is 0.73 Ma. The pa- leoseismic dislocation in the region of the Dragalevtsi quarter was probably formed at the same time. The paleoseismic deformations during the Middle Pleistocene were es- tablished along the radial faults. They had caused rock-falls in the Douhlata cave, pyra- teries and bifurcations of the underground aquatic system and of the Klisuritsa River. The Holocene stage was characterised by intensified vertical movements along all fault structures together with the climatic changes under post-glacial circumstances. The Vitosha paleovolcano was mightily raised due to the vertical compression and new river system originated while the old one was

  2. Multiple Tectonic Regimes and Diverging Geologic Histories of Terrestrial Planets: The Importance of the Early Years

    Science.gov (United States)

    Weller, M. B.; Lenardic, A.

    2013-12-01

    We use 3D mantle convection and planetary tectonics simulations to explore the links between tectonic regimes, the age of a planet, and its surface evolution. We demonstrate that the tectonic regime of a planet is dependant on its thermal and climatic evolution. A young planet with a high degree of internal heating has a strong susceptibility to climate-induced transitions in tectonic styles. The amplitude of a long lived surface temperature perturbation needed to initiate a transition from a mobile- to a stagnant-lid mode of tectonics decreases with increasing degrees of internal heating. As surface temperatures increase, episodic convection occurs over a larger range of lid strengths, suggesting that young and high temperature planetary bodies have a higher potential to exist in a long-lived mode of episodic tectonics. Once the system transitions into a stagnant-lid, the reverse transition is not attainable by a return to the original surface temperature, which indicates that the climate-tectonic system is bi-stable [multiple tectonic states are possible for the same parameter values]. As a planet ages, the system becomes increasingly insensitive to surface temperature induced transitions after ~30 - 50% of the original radiogenics decay. For a planet to transition from mobile- into episodic-, or stagnant-lid modes through the mechanism of increasing surface temperatures, the implication is that the change would have to occur early in its evolution, within the first 1-2 giga years. While the sensitivity to climatic perturbations decreases with the age of the planet, decreasing internal heat production can usher in a transition in tectonic regimes from a stagnant-lid state, into an episodic- and finally mobile-/sluggish-lid regimes. The implications are that terrestrial worlds can alternate between multiple tectonic states over giga-year timescales. The implications for the early Earth and Earth-Venus differences will be discussed.

  3. Jadeitites and Plate Tectonics

    Science.gov (United States)

    Harlow, George E.; Tsujimori, Tatsuki; Sorensen, Sorena S.

    2015-05-01

    Jadeitite is a relatively rare, very tough rock composed predominantly of jadeite and typically found associated with tectonic blocks of high-pressure/low-temperature metabasaltic rocks (e.g., eclogite, blueschist) in exhumed serpentinite-matrix mélanges. Studies over the past ˜20 years have interpreted jadeitite either as the direct hydrous fluid precipitate from subduction channel dewatering into the overlying mantle wedge or as the metasomatic replacement by such fluids of oceanic plagiogranite, graywacke, or metabasite along the channel margin. Thus, jadeitites directly sample and record fluid transport in the subduction factory and provide a window into this geochemical process that is critical to a major process in the Earth system. They record the remarkable transport of large ion lithophile elements, such as Li, Ba, Sr, and Pb, as well as elements generally considered more refractory, such as U, Th, Zr, and Hf. Jadeitite is also the precious form of jade, utilized since antiquity in the form of tools, adornments, and symbols of prestige.

  4. Navigating Towards Digital Tectonic Tools

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due; Kirkegaard, Poul Henning

    2006-01-01

    understand the conflicts in architecture and the building industry but also bring us further into a discussion of how architecture can use digital tools. The investigation is carried out firstly by approaching the subject theoretically through the term tectonics and by setting up a model of the values 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...... like opposites, the term tectonics deals with creating a meaningful relationship between the two. The aim of this paper is to investigate what a digital tectonic tool could be and what relationship with technology it should represent. An understanding of this relationship can help us not only to...

  5. Tectonic Subsidence Analysis of the Pearl River Mouth Basin, Northern South China Sea

    Science.gov (United States)

    Tang, X.; Huang, S. S. X. E. C.; Zhuang, W.; LIU, Z.; Duan, W.; Hu, S.

    2015-12-01

    The Pearl River Mouth Basin (PRMB hereafter) in the northern margin of the South China Sea has attracted great attention not only because of its special tectonic location but also for its abundant hydrocarbon resources. Tectonic evolution controls the petroleum geological condition of hydrocarbon-bearing basins. Efforts have been made to understand the tectonic evolution of this basin. However, many issues about the tectonic features and the evolution process of this basin, such as the age of the breakup unconformities and the anomalously accelerated subsidence during the post-rifting stage, remain controversial. Here we employ tectonic subsidence analysis of sedimentary basins, a technique of removing isostatic loading and compaction effects by back-stripping, to investigate the tectonic controls on the basin formation of the PRMB. We performed the analysis on 4 drill wells and 43 synthetic wells constructed based on recently acquired seismic profiles. The result shows that tectonic subsidence in the eastern sags of the PRMB began to decrease at ~30Ma while in the western sags the onset was ~23.8Ma. This suggests that the break-up time i.e. the end of rifting in the PRMB is earlier in the eastern sags than in the western sags. Abnormally accelerated tectonic subsidence occurred between 17.5-16.4Ma during the post-rifting stage, at an average subsidence rate as high as 301.9m/Ma. This phenomenon discriminates the PRMB from the category of classical Atlantic passive continental marginal basins, of which the tectonic subsidence during the post-rifting stage decays exponentially. The main objective of this paper is to provide insights into the geological and geodynamic evolution of the PRMB. The result bears significance to hydrocarbon exploration in this region.

  6. Tectonics and sedimentation in the Curitiba Basin, south of Brazil

    Science.gov (United States)

    Salamuni, Eduardo; Ebert, Hans Dirk; da Silva Borges, Mauricio; Hasui, Yociteru; Costa, João Batista Sena; Salamuni, Riad

    2003-03-01

    The Curitiba Basin, Paraná, lies parallel to the west side of the Serra do Mar range and is part of a continental rift near the Atlantic coast of southeastern Brazil. It bears unconsolidated and poorly consolidated sediments divided in two formations: the lower Guabirotuba Formation and the overlying Tinguis Formation, both developed over Precambrian basement. Field observations, water well drill cores, and interpretations of satellite images lead to the inference that regional tectonic processes were responsible for the origin of the Basin in the continental rift context and for morphotecatonic evolution through block tilting, dissection, and erosion. The structural framework of the sediments and the basement is characterized by NE-SW-trending normal faults (extensional tectonic D 1 event) reactivated by NE-SW-trending strike-slip and reverse oblique faults (younger transtensional tectonic D 2' to transpressional tectonic D 2″ event). This tectonic event, which started in the Paleogene and controlled the basin geometry, began as a halfgraben and was later reactivated as a pull-apart basin. D 2 is a neotectonic event that controls the current morphostructures. The Basin is connected to the structural rearrangement of the South American platform, which underwent a generalized extensional or trantensional process and, in late Oligocene, changed to a compressional to transpressional regime.

  7. Geochemistry and zircon U-Pb geochronology of granitic rocks in the Buqingshan tectonic mélange belt, northern Tibet Plateau, China and its implications for Prototethyan evolution

    Science.gov (United States)

    Li, Ruibao; Pei, Xianzhi; Li, Zuochen; Pei, Lei; Liu, Chengjun; Chen, Youxin; Chen, Guochao; Liu, Zhanqing; Yang, Jie

    2015-06-01

    The Yikehalaer intrusives are distributed in the Buqingshan tectonic mélange belt at the southern margin of East Kunlun, China. They tectonically intruded the conglomerate of Permian Gequ Formation to the south and the marble of Mesoproterozoic Kuhai Group to the north. These intrusives mainly consist of off-white coarse- and fine-grained granodiorite and granite. U-Pb dating of zircons from the intrusive samples yielded weighted mean 206Pb/238U ages of 436 ± 7 Ma and 437 ± 6 Ma, indicating Early Silurian crystallization age. The intrusives are high-silica, Na-rich, I-type calc-alkalic rocks. They are divisible into two subgroups on the basis of their trace element content: adakitic rocks in the northern part and normal calc-alkalic arc rocks in the southern part. Rocks in the northern part exhibit high Sr (280-493 ppm), low Y (3.8-11.7 ppm), high Sr/Y ratios (23.9-125.0), high light rare earth elements (LREE)/ heavy rare earth elements (HREE) (15.1-35.7), and invisible Eu/Eu∗. They resemble adakites formed by slab melting in subduction zones. However, the rocks in the southern part possess the attributes of normal arc rocks. In addition, the εHf(t) values of the intrusives are consistently positive (0.6-7.6), implying that they were generated by melting of an isotopically depleted mantle source, with insignificant contributions from crustal materials. The source residues likely contained 10-20% garnet and hornblende, and plagioclase was either absent or totally consumed during partial melting. Combining the regional tectonic data, we conclude that the Buqingshan paleo-ocean may have started to subduct in Middle Cambrian until Early Silurian (436 Ma), generating an important adakitic magma event during the late stage of oceanic crust subduction. Moreover, the Proto-Tethyan Ocean closed, and the Bayan Har, East Kunlun, and Qaidam blocks collided during the Middle-Late Silurian.

  8. REE, Sm-Nd and U-Pb zircon study of eclogites from the Alpine External Massifs (Western Alps): Evidence for crustal contamination

    International Nuclear Information System (INIS)

    A geochemical and geochronological study of the Alpine External Crystalline Massifs (AECM) of Aiguilles Rouges, Belledonne and Argentera was undertaken in order to constrain the geodynamic evolution of this segment of the Variscan foldbelt. Another aim of the study is to characterize the behaviour of isotopic markers, in particular the U-Pb zircon system, under high-grade metamorphic conditions. The whole-rock geochemistry of eclogites and amphibolites was investigated using major and trace element (including the REE) analytical techniques; isotopic studies were performed by application of the Sm-Nd whole-rock and U-Pb zircon methods. In terms of regional geological history, the early development of metamorphic and magmatic activity in the AECM is typical of the extensional tectonic regime observed throughout the Variscan foldbelt during the Cambro-Ordovician (i.e. basic magmatism dated at 475-450 Ma). The composition of the metabasic rocks is closely similar to tholeiites emplaced into thinned continental crust which are generally associated with the initial stages of oceanic rifting. The source regions for these metabasics are characterized by initial εNd values between +6 and +8, suggesting depleted mantle sources influenced by a weak crustal component and/or the existence of a metasomatised lithosphere. The multi-stage eclogite-facies metamorphism is dated at 425-395 Ma (i.e. Silurian). An application of the U-Pb method, associated with the artificial abrasion of zircon grains, has led to the recognition of a weak crustal contamination in the metabasic protoliths. This is implied by the Archaean and Lower Proterozoic upper intercepts on Concordia - devoid of geological significance - which reflect the presence of a pre-existing basement to the AECM. (orig./WL)

  9. Interaction of various flow systems in small alpine catchments: conceptual model of the upper Gurk Valley aquifer, Carinthia, Austria

    Science.gov (United States)

    Hilberg, Sylke; Riepler, Franz

    2016-03-01

    Small alpine valleys usually show a heterogeneous hydraulic situation. Recurring landslides create temporal barriers for the surface runoff. As a result of these postglacial processes, temporal lakes form, and thus lacustrine fine-grained sedimentation intercalates with alluvial coarse-grained layers. A sequence of alluvial sediments (confined and thus well protected aquifers) and lacustrine sediments (aquitards) is characteristic for such an environment. The hydrogeological situation of fractured hard-rock aquifers in the framing mountain ranges is characterized by superficially high hydraulic conductivities as the result of tectonic processes, deglaciation and postglacial weathering. Fracture permeability and high hydraulic gradients in small-scaled alpine catchments result in the interaction of various flow systems in various kinds of aquifers. Spatial restrictions and conflicts between the current land use and the requirements of drinking-water protection represent a special challenge for water resource management in usually densely populated small alpine valleys. The presented case study describes hydrogeological investigations within the small alpine valley of the upper Gurktal (Upper Carinthia, Austria) and the adjacent Höllenberg Massif (1,772 m above sea level). Hydrogeological mapping, drilling, and hydrochemical and stable isotope analyses of springs and groundwater were conducted to identify a sustainable drinking-water supply for approximately 1,500 inhabitants. The results contribute to a conceptual hydrogeological model with three interacting flow systems. The local and the intermediate flow systems are assigned to the catchment of the Höllenberg Massif, whereas the regional flow system refers to the bordering Gurktal Alps to the north and provides an appropriate drinking water reservoir.

  10. Interaction of various flow systems in small alpine catchments: conceptual model of the upper Gurk Valley aquifer, Carinthia, Austria

    Science.gov (United States)

    Hilberg, Sylke; Riepler, Franz

    2016-08-01

    Small alpine valleys usually show a heterogeneous hydraulic situation. Recurring landslides create temporal barriers for the surface runoff. As a result of these postglacial processes, temporal lakes form, and thus lacustrine fine-grained sedimentation intercalates with alluvial coarse-grained layers. A sequence of alluvial sediments (confined and thus well protected aquifers) and lacustrine sediments (aquitards) is characteristic for such an environment. The hydrogeological situation of fractured hard-rock aquifers in the framing mountain ranges is characterized by superficially high hydraulic conductivities as the result of tectonic processes, deglaciation and postglacial weathering. Fracture permeability and high hydraulic gradients in small-scaled alpine catchments result in the interaction of various flow systems in various kinds of aquifers. Spatial restrictions and conflicts between the current land use and the requirements of drinking-water protection represent a special challenge for water resource management in usually densely populated small alpine valleys. The presented case study describes hydrogeological investigations within the small alpine valley of the upper Gurktal (Upper Carinthia, Austria) and the adjacent Höllenberg Massif (1,772 m above sea level). Hydrogeological mapping, drilling, and hydrochemical and stable isotope analyses of springs and groundwater were conducted to identify a sustainable drinking-water supply for approximately 1,500 inhabitants. The results contribute to a conceptual hydrogeological model with three interacting flow systems. The local and the intermediate flow systems are assigned to the catchment of the Höllenberg Massif, whereas the regional flow system refers to the bordering Gurktal Alps to the north and provides an appropriate drinking water reservoir.

  11. Intraspecific competition and light effect on reproduction of Ligularia virgaurea, an invasive native alpine grassland clonal herb

    OpenAIRE

    Xie, Tian-peng; Zhang, Ge-fei; Zhao, Zhi-Gang; Du, Guo-Zhen; He, Gui-yong

    2014-01-01

    The relationship between sexual reproduction and clonal growth in clonal plants often shows up at the ramet level. However, only a few studies focus on the relationship at the genet level, which could finally account for evolution. The sexual reproduction and clonal growth of Ligularia virgaurea, a perennial herb widely distributed in the alpine grasslands of the Qinghai-Tibetan Plateau of China, were studied under different competition intensities and light conditions at the genet level thro...

  12. Modelling atmospheric circulations for the study of Alpine valleys pollution; Modelisation des circulations atmospheriques pour l'etude de la pollution des vallees alpines

    Energy Technology Data Exchange (ETDEWEB)

    Brulfert, G.

    2004-11-15

    Local weather phenomena observed in alpine valleys frequently lead to the accumulation of emitted anthropogenic airborne species in the low layers of the atmosphere. The development of a numerical model allows reproducing the chemical evolution of air mass during POVA intensive period of observations. In Chamonix and Maurienne valley, computations of photochemical indicators (NO{sub y}, O{sub 3}/NO{sub z}, H{sub 2}O{sub 2}/HNO{sub 3}) prove the ozone regime to be control by volatile organic compounds. Moreover simulation highlighted that the major part of this secondary pollutant is regionally produced. The development of an indicator who localised ozone production sites can help to define abatement scenarios. The chemical mechanism RACM allows describing the evolution of many species. It is possible to conclude that in winter road traffic and heating are the main sources of volatile organic compounds. (author)

  13. Tectonic earthquakes of anthropogenic origin

    Science.gov (United States)

    Adushkin, V. V.

    2016-03-01

    The enhancement of seismicity induced by industrial activity in Russia in the conditions of present-day anthropization is noted. In particular, the growth in the intensity and number of strong tectonic earthquakes with magnitudes M ≥ 3 (seismic energy 109 J) due to human activity is revealed. These man-made tectonic earthquakes have started to occur in the regions of the East European Platform which were previously aseismic. The development of such seismicity is noted in the areas of intense long-term mineral extraction due to the increasing production depth and extended mining and production. The mechanisms and generation conditions of man-made tectonic earthquakes in the anthropogenically disturbed medium with the changed geodynamical and fluid regime is discussed. The source zones of these shallow-focus tectonic earthquakes of anthropogenic origin are formed in the setting of stress state rearrangement under anthropogenic loading both near these zones and at a significant distance from them. This distance is determined by the tectonic structure of the rock mass and the character of its energy saturation, in particular, by the level of the formation pressure or pore pressure. These earthquakes occur at any time of the day, have a triggered character, and are frequently accompanied by catastrophic phenomena in the underground mines and on the surface due to the closeness to the source zones.

  14. Modelling vegetation dynamics for Alpine meadows

    Science.gov (United States)

    Della Chiesa, Stefano; Bertoldi, Giacomo; Wohlfahrt, Georg; Rist, Armin; Niedrist, Georg; Albertson, John D.; Tappeiner, Ulrike

    2010-05-01

    Regional climate scenarios predict a temperature increase and a summer precipitation decrease for the European Alps. This is expected to lead to longer vegetation periods, but also to drought stress in Alpine meadows ecosystems. It is therefore uncertain if the predicted climatic changes will lead to an increase or decrease of biomass production in these grassland ecosystems. Understanding plant growth requires to consider the complex interactions between soil, atmosphere and climate via its physiological properties, in particular LAI, stomatal resistance, rooting depth, albedo, surface roughness and effects on soil moisture. Vegetation Dynamic Models (VDM) coupled with hydrological models take into account these interactions in order to study and estimate biomass production quantitatively. In this contribution, the VDM previously developed by Montaldo et al. (2005) for semi-arid environments is extended to Alpine meadows in the Stubai Valley (Eastern Austria) which are typically not subjected to water and nutrient stresses, but undergoing low temperature limitations. The aim is to assess the model robustness. Moreover, the effects of mowing practice during the season were taken into consideration. The VDM has then been implemented in the distributed hydrological model GEOtop (Rigon et al., 2006). The VDM performed well in the considered case study. The validation and calibration of the model is presented and then the effects of increased temperature and decreased precipitation are investigated numerically. In order to evaluate in the field the effects of climatic change on Alpine grassland biomass production, the inner Alpine continental Mazia Valley (South Tyrol, Italy) has been chosen in 2009 for Long-Term Ecological Research. These climatic changes will be simulated by manipulations along an altitudinal gradient comprising measuring stations at about 1000 m, 1500 m and 2000 m a.s.l.. Meadow monoliths will be transplanted downslope to simulate temperature

  15. Terrane Tectonics in the Northeast Part of Northeast of China

    Institute of Scientific and Technical Information of China (English)

    Sun Jiapeng; Ye Mao; Dong Yongsheng; Sun Weizhi

    2000-01-01

    As the members of Chinese Group of the international cooperative project of "Mineral Resources, Metallogenesis,and Tectonics of Northeast Asia", the authors had the opportunity to review the recent achievement of regional geology in this area. This paper is confined to a brief discussion of the nature, composition and evolution of terranes in a part of Northeast China. Nine terranes were recognized. A splicing pattern of when and how the amalgamation of 9 terranes into one microcontient is proposed here.

  16. STUDY ON THE TECTONIC STRESS FIELDS OF MESO-CENOZOIC IN LU' AN MINING AREA BY FINITE-ELEMENT SIMULATION

    Institute of Scientific and Technical Information of China (English)

    曹代勇; 张杰林; 关英斌; 钱光谟; 吴国强; 韩远方; 赵志明

    1995-01-01

    The structural deformation of Lu' an mining area is characterized by a remarkable feature of zoning along E-W direction, in the east.limb of Qinshui basin, Shanxi Province, China. The regional tectonic stress fields and basement tectonics are two fundamental factors to control the cover tectonic framework. This paper uses the finite-element method with a elastic-plastic plan problem model to simulate the three periods of stress fields resulting from field geological study. Based on these works, the formation and evolution of tectonic framework of Lu' an mining area have been discussed.

  17. Precambrian crustal evolution and Cretaceous–Palaeogene faulting in West Greenland: Structural analysis of the northern Nagssugtoqidian orogen, West Greenland: an example of complex tectonic patterns in reworked high-grade metamorphic terrains

    Directory of Open Access Journals (Sweden)

    Mazur, Stanislaw

    2006-12-01

    Full Text Available Structural analysis of the deeply eroded northern flank of the Palaeoproterozoic Nagssugtoqidian orogen shows marked regional variations in both the orientation and type of fabrics, as is characteristic of Precambrian high-grade terrains subjected to polyphase deformation. Here we investigate the relationship between strain, metamorphic grade, and the resulting structural patterns. The study area south of Aasiaat in West Greenland consists of amphibolite- togranulite-gradeArchaean orthogneisses and relatively thin supracrustal units. The regional foliation displays a WSW–ENE to SW–NE strike associated with steep to moderate dips towards the WNW or SSE. Lineation trends are WSW–ENE and generally plunge gently towards the WSW. Mesoscopic fold hinges are usually colinear with the regional lineation. A systematic change in the plunge of lineations occurs across the south-western part of the study area. Towards the south, the lineation plunge progressively increases, despite the generally uniform strike of foliation. This southward increase of lineation pitch is typically associated with the transition from L > S or L = S shape fabrics in rocks characterised by a low pitch, to S > L or S fabrics in the zone of moderate to high pitch. The structural patterns point to subdivision of the study area into a southern domain mostly characterised by S or S > L shape fabrics and a moderate to high angle of lineation pitch, and a northern domain showing L > S or L = S fabrics and low angles of lineation pitch. This subdivision corresponds well with the map scale boundary between granulite facies rocks in the south and amphibolite facies rocks farther north. The observed structural pattern may be explained by two alternative tectonic models: (1 northward indentation of the previously cooled granulite block into the rheologically weaker amphibolite domain, and (2 strain partitioning within a mid-crustal transpression zone. In model 2 the northern domain

  18. Evolution process of the Late Silurian–Late Devonian tectonic environment in Qimantagh in the western portion of east Kunlun, China: Evidence from the geochronology and geochemistry of granitoids

    Indian Academy of Sciences (India)

    Nana Hao; Wanming Yuan; Aikui Zhang; Yunlei Feng; Jianhui Cao; Xiaoning Chen; Xueqin Cheng; Xuanxue Mo

    2015-02-01

    The East Kunlun Orogenic Belt has undergone a composite orogenic process consisting of multiple orogenic cycles and involving many types of magmatic rocks spread over the whole district. However, due to bad natural geographical conditions and complex superimposed orogenic processes, most of the Caledonian orogenic traces were modified by the late tectonic uplift and denudation, so these rocks are poorly studied. Multiperiodic magmatic activity during the Late Silurian (approximately 420 Ma)–Late Devonian (approximately 380 Ma) exists in the Qimantagh area. We obtained 5 zircon U–Pb ages from the Late Silurian–Late Devonian granitoids in the Qimantagh area. Those ages are 420.6 ± 2.6 Ma(Nalingguole biotite monzogranite), 421.2 ± 1.9 Ma (Wulanwuzhuer potassium granite), 403.7 ± 2.9 Ma (Yemaquan granodiorite), 391.3 ± 3.2 Ma (Qunli granite porphyry), and 380.52 ± 0.92 Ma (Kayakedengtage granodiorite). These granitoids belong to the sub-alkaline, high-K calc-alkaline, metaluminous or weakly or strongly peraluminous series. The rocks are right oblique types, having overall relative LREE enrichment and HREE depletion, though rocks from different times may exhibit different degrees of Eu anomalies or overall moderate Eu depletion. The rocks are rich in large ion lithophile elements (LILE), such as Rb, Th, and K, and high field strength elements (HFSE), such as Zr and Hf, and are depleted in Ba, Nb, Ta, Sr, P, Eu, and Ti. The rocks have complex composition sources. The Late Silurian granitoids are mainly crust-derived. Most of the Devonian granitoids are crust-mantle mixed-source and only some parts of them are crust-derived, especially the Middle Devonian granitoids. Those mid-acidic and acidic intrusive rocks are formed in a post-collision tectonic setting, lithosphere delamination may have occurred in the Early Devonian (407 Ma), and the study area subsequently experienced an underplating of the mantle-derived magma at least until the Late Devonian (380 Ma).

  19. TECTONICS AND CRUSTAL EVOLUTION OF ALTAI IN CHINA AND KAZAKHSTAN%中国和哈萨克斯坦阿尔泰大地构造及地壳演化

    Institute of Scientific and Technical Information of China (English)

    李天德; В.Н.波里扬斯基

    2001-01-01

    Altai in China and Kazakhstan is located at the southwesternmargin of Siberia plate, where Altai fold system and Zhaisang-North Jungger fold system join together. The tectonic units are divided as follows, the 1st grade units for fold region, the sub-1st grade units for fold system, the 2nd grade units for tectono-formation belt which roughly corresponds with fold belt, central uplift belt or central crystalline belt or simply-called belt. The 3rd grade units roughly correspond with anticlinoria, synclinoria, combination of above two, and faulted blocks. These are simlpy called sub-belts. Four tectono-formation sub-belts are divided in the area. The tectonic framework of the area formed through repeated extensions and compressions. Four key stages are divided, i.e., Archean-Proterozoic formation of paleo-continental crust, Early Paleozoic accretion of passive continental margin, Late Paleozoic extension-compression of continental crust, and Meso-Cenozoic relatively stable development.%中国和哈萨克斯坦阿尔泰位于西伯利亚板块西南边缘,阿尔泰褶皱系与斋桑-北准噶尔褶皱系的接合部位,分为霍尔宗-丘伊-哈纳斯、冲乎尔-青河、别洛乌巴-南阿尔泰、矿区阿尔泰和东卡尔巴-富蕴、二台6个构造建造带,14个构造建造亚带。区内地壳演化可分为太古宙-元古宙古陆壳形成阶段、早古生代被动陆缘陆壳增生阶段、晚古生代陆壳拉张破坏和挤压重建(增生)阶段及中-新生代相对稳定的大陆发展阶段。

  20. Tectonics of the Easter plate

    Science.gov (United States)

    Engeln, J. F.; Stein, S.

    1984-01-01

    A new model for the Easter plate is presented in which rift propagation has resulted in the formation of a rigid plate between the propagating and dying ridges. The distribution of earthquakes, eleven new focal mechanisms, and existing bathymetric and magnetic data are used to describe the tectonics of this area. Both the Easter-Nazca and Easter-Pacific Euler poles are sufficiently close to the Easter plate to cause rapid changes in rates and directions of motion along the boundaries. The east and west boundaries are propagating and dying ridges; the southwest boundary is a slow-spreading ridge and the northern boundary is a complex zone of convergent and transform motion. The Easter plate may reflect the tectonics of rift propagation on a large scale, where rigid plate tectonics requires boundary reorientation. Simple schematic models to illustrate the general features and processes which occur at plates resulting from large-scale rift propagation are used.

  1. PRELIMINARY DISCUSSION ON METALLOGENESIS OF LANCANGJIANG RIVER TRANSITIONAL FIELD TECTONIC ZONE IN WESTERN YUNNAN

    Institute of Scientific and Technical Information of China (English)

    HU Bin; DAI Tagen; HU Ruizhong; GUO Qun

    2004-01-01

    Applying the crustobody geotectonic theory to geological prospecting at the Lancangjiang river metallogenic belt in western Yunnan province, and on the basis of the basic geological background of western Yunnan and the space-time evolution-movement historical-dynamic features of the Lancangjiang river tectonic belt, the author has discussed firstly the metallogenesis of the Lancangjiang river transitional field tectonic zone, which can provide a new theoretical foundation for exploring the space-time laws of mineralization in this region.

  2. On the History of the Continents:A Story of Plate Tectonics and Earth Tides

    OpenAIRE

    Bo Pedersen, Flemming

    2011-01-01

    The present monograph is published to honour Dr. Tech. Flemming Bo Pedersen, Professor Emeritus in Hydrodynamics at the Technical University of Denmark, on his seventy year’s birthday and in gratitude for his continuous support to LICengineering A/S. The monograph collects Professor Emeritus, Dr. Tech. Flemming Bo Pedersen research and findings on plate tectonics during the last fifteen years. A new theory for plate tectonics and the evolution of Earth is introduced in the monograph. The gove...

  3. Evolution: from cosmogenesis to biogenesis

    International Nuclear Information System (INIS)

    The volume contains the material of an interdisciplinary evolution symposium. The purpose was to shed some light on possible connections between steps of evolution of matter on different levels of organisation. The topics involved are as follow: cosmogenesis; galactic and stellar evolution; formation and evolution of the solar system; global atmospheric and tectonic changes of Earth; viral evolution; phylogeny and evolution of terrestrial life; evolution of neural system; hominization. The material also includes some discussions of the underlying phenomena and laws of nature. (author)

  4. Emerging Possibilities and Insuperable Limitations of Exogeophysics: The Example of Plate Tectonics

    Science.gov (United States)

    Stamenković, Vlada; Seager, Sara

    2016-07-01

    To understand the evolution and the habitability of any rocky exoplanet demands detailed knowledge about its geophysical state and history—such as predicting the tectonic mode of a planet. Yet no astronomical observation can directly confirm or rule out the occurrence of plate tectonics on a given exoplanet. Moreover, the field of plate tectonics is still young—questioning whether we should study plate tectonics on exoplanets at this point in time. In this work, we determine the limitations and the emerging possibilities of exogeophysics, the science of connecting geophysics to exoplanets, on the example of plate tectonics. Assuming current uncertainties in model and planet parameters, we develop a qualitatively probabilistic and conservative framework to estimate on what kind of planets and where in the Galaxy plate tectonics might occur. This we achieve by modeling how plate yielding, the most critical condition needed for plate mobility and subduction, is affected by directly observable (planet mass, size) or indirectly, to some degree, assessable planet properties (structure and composition). Our framework not only highlights the importance of a planet’s chemistry for the existence of plate tectonics and the path toward practical exogeophysics but also demonstrates how exoplanet science can actually help to better understand geophysics and the fundamentals of plate tectonics on Earth itself.

  5. An Analysis of Late Mesozoic Tectonic Evolution Process in Northern China:Based on Basin Sedimentary Records in Northern Taihang Mountains%华北晚中生代构造演化过程--根据太行山北部盆地沉积记录

    Institute of Scientific and Technical Information of China (English)

    王永超; 董树文; 施炜; 岑敏; 李江瑜

    2016-01-01

    The northern Taihang Mountains are located at the junction of the Yanshan tectonic belt with the Taihang Mountains belt, and their superimposed basin development process documented the basin trending conversion process from EW to NE during Jurassic to Cretaceous, which is significant for depicting the intracontinental deformation process and its dynamic background during the late Mesozoic in North China. Caogoubu basin and Zhaobai basin located in northern Taihang Mountains were selected as examples in this paper. According to the basic structural framework analysis of basins in combination with isotope chronologic data from magmatic rocks and sedimentology methods which include the detailed analysis of sediment provenance, prototype basin reconstruction and so on, tectonic evolution history of the northern Taihang Mountains during the late Mesozoic can be detected, which includes four stage evolution sequences : (1) nearly N–S contraction and flexural basin development during the late middle Jurassic, (2) nearly N–S low-magnitude extention and crust sources volcanic eruption that occurred in the late Jurassic, (3) NW–SE contraction and foreland basin development from the end of the late Jurassic to the earliest Cretaceous, and (4) NW–SE extension and mantle sources volcanic eruption during the early Cretaceous. The conversion of tectonic regimes is essentially the transformation of its geodynamic systems, and on the context of the East Asia multi-direction convergent tectonic system during the Middle–Late Jurassic, the multi-phases tectonic and basin superposition that occurred in northern Taihang Mountains during the late Mesozoic indicates the conversion process during which the Mogolia–Okhotsk tectonic system graded into the Marginal–Pacific tectonic system.%太行山北部地区处于燕山山脉和太行山山脉的交汇处,其侏罗纪—白垩纪叠加盆地发育过程记录了东西向盆地向北东向盆地转化过程,对刻画华

  6. Metabolic Profiling of Alpine and Ecuadorian Lichens

    Directory of Open Access Journals (Sweden)

    Verena K. Mittermeier

    2015-10-01

    Full Text Available Non-targeted 1H-NMR methods were used to determine metabolite profiles from crude extracts of Alpine and Ecuadorian lichens collected from their natural habitats. In control experiments, the robustness of metabolite detection and quantification was estimated using replicate measurements of Stereocaulon alpinum extracts. The deviations in the overall metabolite fingerprints were low when analyzing S. alpinum collections from different locations or during different annual and seasonal periods. In contrast, metabolite profiles observed from extracts of different Alpine and Ecuadorian lichens clearly revealed genus- and species-specific profiles. The discriminating functions determining cluster formation in principle component analysis (PCA were due to differences in the amounts of genus-specific compounds such as sticticin from the Sticta species, but also in the amounts of ubiquitous metabolites, such as sugar alcohols or trehalose. However, varying concentrations of these metabolites from the same lichen species e.g., due to different environmental conditions appeared of minor relevance for the overall cluster formation in PCA. The metabolic clusters matched phylogenetic analyses using nuclear ribosomal DNA (nrDNA internal transcribed spacer (ITS sequences of lichen mycobionts, as exemplified for the genus Sticta. It can be concluded that NMR-based non-targeted metabolic profiling is a useful tool in the chemo-taxonomy of lichens. The same approach could also facilitate the discovery of novel lichen metabolites on a rapid and systematical basis.

  7. Thermotectonic evolution of the Apuseni mountains (Romania) based on structural and geothermochronological data

    Science.gov (United States)

    Reiser, M. K.; Fügenschuh, B.; Schuster, R.

    2012-04-01

    The Apuseni Mountains in Romania take a central position in the Alpine Carpathian Dinaride system between the Pannonian basin in the West and the Transylvanian basin in the East. Following the final Mid-Cretaceous obduction of the East Vardar ophiolite a NW-vergent nappe stack formed, which involves from bottom to top: Tisza- (Bihor and Codru) and Dacia-derived (Biharia) units, overlain by the South Apuseni or Transylvanian ophiolite belt (see Schmid et al, 2008). This study tries to provide new and additional information on the complex structural and metamorphic evolution of these units, from the onset of obduction during Jurassic times, to the (final?) exhumation processes observed during the Eocene (according to Merten, 2011). Based on observed stretching lineations, kinematic indicators such as porphyroclasts, shearbands etc. were analyzed to establish a relative chronological order of deformation and tectonic transport. Microstructural studies provided additional data on the relative succession of events and the relevant synkinematic temperatures. A thermochronological study, based on the integration of newly aquired Rb-Sr, Sm-Nd, Ar-Ar and fission track ages with existing data allowed the construction of a time-temperature deformation path. Our data indicate three major events, a Late Jurassic-Earliest Cretaceous exhumation event, which cannot be directly constrained by structural data so far. Yet the position of the Transsylvanian ophiolites tectonically overlying the Biharia unit as well as distinct thermochronological data are self-explaining. The second event ("Austrian Phase" in local nomenclature), documented by structural and thermochronological data, is related to the top to the NE thrusting (i.e. in present-day coordinates) of Tisza over Dacia during the Mid-Cretaceous. This penetrative event in the Biharia unit is overprinted at the contact between nappes by a third, top to the NW event during the Turonian, which relates to the NW directed

  8. Pleistocene origin and population history of a neoendemic alpine butterfly.

    Science.gov (United States)

    Schoville, Sean D; Stuckey, Matthew; Roderick, George K

    2011-03-01

    Alpine environments underwent dramatic transformation during glacial-interglacial cycles, with the consequence that geographical, ecological and demographic changes of alpine populations provided the opportunity for formation of neoendemic species. Several biogeographical models have been proposed to account for the unique history of alpine populations, with different expectations of genetic divergence and speciation. The expanding alpine archipelago model proposes that alpine populations expand spatially and demographically during glacial events, dispersing between mountain ranges. Under this model, alpine populations are unlikely to diverge in isolation due to substantial interpopulation gene flow. In contrast, the alpine archipelago refuge model proposes that gene flow during glacial phases is limited and populations expand demographically during interglacial phases, increasing genetic isolation and the likelihood of speciation. We assess these models by reconstructing the evolutionary history of Colias behrii, a morphologically and ecologically distinct alpine butterfly restricted to the California Sierra Nevada. C. behrii exhibits very low genetic diversity at mitochondrial and nuclear loci, limited population structure and evidence of population expansion. C. behrii and Rocky Mountain C. meadii share identical mitochondrial haplotypes, while in contrast, nuclear data indicate common ancestry between C. behrii and Cascades Range Colias pelidne. The conflict in gene genealogies may be a result of recent expansion in North American Colias, but an isolation with migration analysis indicates that genetic patterns in C. behrii might result from differential introgression following hybridization. Based on the timing of population expansion and gene flow between mountain ranges, the expanding alpine archipelago model is supported in C. behrii. PMID:21244539

  9. Depositional history and tectonic regimes within and in the margins of the Fennoscandian shield during the last 1300 million years

    International Nuclear Information System (INIS)

    , Rodinia. At ca. 620 - 600 Ma, this supercontinent started to break-up. By Late Cambrian times, the plate convergence started again, leading to the Caledonian orogeny at the NW margin of the Fennoscandian Shield, the main phase of which occurred in Silurian, at ca. 425 Ma. The tectonics related to the late phase of the central European Variscan orogeny resulted in strike-slip faulting along the NW-SE trending Tornquist Zone in the south-western margin of the Fennoscandian Shield. The faulting was associated with volcanic activity and intrusion of dyke swarms, dated at 300 - 240 Ma. The Permian rifting and volcanism is demonstrated by ca. 400 km long Oslo Rift. During the Mesozoic rifting, the Tornquist Zone was repeatedly reactivated. In the Tertiary, the opening of the North Atlantic, the initiation of sea-floor spreading in the Norwegian-Greenland Sea and onset of the Alpine continent-continent collision dominated the evolution of north-western Europe. Mainly the margins of the Fennoscandian Shield were affected by the uplift of western Scandinavia. The ridge push forces from the Mid-Atlantic Ridge seem to be the major stress-generating mechanism in Fennoscandia today, but the current stress field is likely a combination of plate boundary forces with local sources (e.g. glacial rebound and local geology). Large postglacial faults with a length varying from a few kilometres to tens of kilometres and a scarp height from a few metres to tens of metres occur in northern Finland and elsewhere in northern Fennoscandia. Small post-glacial faults (scarp height 0-20 cm) located in ice polished bedrock outcrops have been found in southern Finland, but so far larger postglacial faults have not been recognised. Investigations on postglacial bedrock movements have revealed that the postglacial faults studied so far are situated in old, reactivated fracture zones. (orig.)

  10. Identifying key conservation threats to Alpine birds through expert knowledge

    OpenAIRE

    Chamberlain, Dan E.; Pedrini, Paolo; Brambilla, Mattia; Rolando, Antonio; Girardello, Marco

    2016-01-01

    Alpine biodiversity is subject to a range of increasing threats, but the scarcity of data for many taxa means that it is difficult to assess the level and likely future impact of a given threat. Expert opinion can be a useful tool to address knowledge gaps in the absence of adequate data. Experts with experience in Alpine ecology were approached to rank threat levels for 69 Alpine bird species over the next 50 years for the whole European Alps in relation to ten categories: land abandonment, ...

  11. Plate tectonics conserves angular momentum

    Directory of Open Access Journals (Sweden)

    C. Bowin

    2009-03-01

    Full Text Available A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4 E+27 kgm2s−1. Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates. Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth. The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant velocity on the crests of convection cells driven by rising heat. These results imply that spreading centers are primarily passive reactive

  12. Increasing alpine transit traffic through Switzerland will considerably enhance high altitude alpine pollutant levels

    Energy Technology Data Exchange (ETDEWEB)

    Prevot, A.S.H.; Dommen, J.; Furger, M.; Graber, W.K. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Within the EU-Project VOTALP (Vertical Ozone Transports in the Alps), we have shown that deep alpine valleys like the Mesolcina Valley very efficiently transport air out of the polluted valley up to altitudes between 2000 and near 4000 m asl (above sea level). Pollutants emitted in these valleys are very efficiently transported up to high altitudes. (author) 2 figs., 1 tab., 2 refs.

  13. The Eastern Alpine Seismic Investigation (EASI) project

    Science.gov (United States)

    Plomerova, Jaroslava; Bianchi, Irene; Hetényi, György; Munzarova, Helena; Bokelmann, Götz; Kissling, Edi; AlpArray-EASI Working Group; AlpArray-EASI Field Team

    2015-04-01

    AlpArray (http://www.seismo.ethz.ch/research/groups/alrt/projects/alparray/) is a large European initiative to study the entire Alpine orogen at high resolution and in 3D with a large variety of methods. The core element of the initiative is an extensive and dense broadband seismological network. In addition, a number of Complementary Experiments will be conducted to focus on targeted problems. The first implemented AlpArray Complementary Experiment is called Eastern Alpine Seismic Investigation (EASI). The Eastern, "straight" part of the Alps is home to a number of open questions, e.g., the origin of the hanging lithospheric slab (Adriatic or European?), the nature of the Moho "hole" between the two plates, the anisotropic nature of the lower crust, and the relationship of the Alpine orogen to the adjacent foreland basin and the lithospheric blocks of the Bohemian Massif. Our research methods include tomography, ambient noise analysis and receiver functions, with anisotropy included in all three types of investigations as well as in shear-wave splitting analyses. The depth range of investigations encompasses the crust and the mantle lithosphere, down to the LAB. In this presentation we detail the design of the experiment. EASI is composed of 55 broadband seismic stations, deployed in a zig-zag pattern on either side of the central longitude line of 13.35°E. The planned north-south distance between stations was 10 km, the distance of each station to either side of the central line was 6 km. We aimed to keep the stations within 1.5 km of the target location, as much as topographic, field and infrastructure condition allowed. The result: with respect to the original deployment plans the closest match is 164m, 10 stations are within 500m, 31 stations are within 1.5km which is also the average match, and the farthest is 4.4km. The overall result remained a very linear and regularly spaced array, spanning 540 km from the Czech-German border to the Adriatic Sea. The

  14. Current tectonic deformation and seismogenic characteristics along the northeast margin of Qinghai-Xizang block*

    Institute of Scientific and Technical Information of China (English)

    王双绪; 江在森; 张希; 陈文胜

    2002-01-01

    Based on the data from repeated precise leveling and across-fault deformation measurements carried out in recent 30 years and the analyzed results from GPS observations made in recent years along the northeastern margin of Qinghai(Xizang block, and combined with the geological structures and seismic activities, some characteristics in regional tectonic deformation and strong earthquake development are studied and approached preliminarily. The results show that: a) The space-time distribution of current tectonic deformation in this area is inhomogeneous with relatively intensive tectonic deformation in the vicinity of main boundary faults and weak deformation in the farther areas. The intensity of vertical differential movement and the deformation status vary with time, and the horizontal movement and deformation are characterized by apparent compression and strike-slip. b) The tectonic stress field generated by the NE-trending continuous compressive movement of Qinghai(Xizang block due to the northward press and collision of India plate is the principal stress for the tectonic deformation and earthquake development in this area. The evolution of space-time distribution of tectonic deformation and seismicity is closely related to the block activity and dynamic evolution of regional tectonic stress field. c) The vertical deformation uplift and high-gradient deformation zones and the obvious fault deformation anomaly appeared along the boundaries of tectonic blocks can be considered as the indicators of hindered block motion and intensified tectonic stress field for strong earthquake development. Usually, the above-mentioned phenomena would be followed by the seismicity of M(6.0, but the earthquake might not occur in the place with the maximum movement. The zones with the fault deformation anomaly characterized by (tendencious accumulation acceleration turning( and the surrounding areas might be the positions for accumulation of strain energy and development and

  15. Sustainable use of alpine and pre-alpine grassland soils in a changing climate (SUSALPS)

    Science.gov (United States)

    Zistl-Schlingmann, Marcus; Beck, Robert; Brandhuber, Robert; Butterbach-Bahl, Klaus; Garcia Franco, Noelia; von Gillhaußen, Phillip; Jentsch, Anke; Kiese, Ralf; Krämer, Alexander; Kögel-Knabner, Ingrid; Köllner, Thomas; Poppenborg, Patrick; Schloter, Michael; Schulz, Stefanie; Wiesmeier, Martin; Wolf, Benjamin; Dannenmann, Michael

    2016-04-01

    The development of ecologically as well as economically sustainable management options for the carbon- and nitrogen rich alpine and pre-alpine grassland soils in a changing climate poses a grand scientific and socio- economical challenge. The transdisciplinary SUSALPS project starting in 2016 aims to essentially improve the knowledge on the functionality of alpine and pre-alpine grassland soils using both natural-scientific/ technical and socio economical approaches. The project is building on existing infrastructure of German grassland-ecosystem-research like the pre-alpine TERENO (Terrestrial ecosystem observation network observatory) observatory sites, the EVENT and SIGNAL sites as well as long term LfL (Bayerische Landesanstalt für Landwirtschaft) sites, plus a new additional high elevation (1400m a.s.l) site in the Bavarian Alps. The site setup along the elevational gradient on the edge of the Alps (1400 m to 300 m) is used for space-for-time climate change experiments which are combined with extensive and intensive management treatments. A key focus of SUSALPS will be the characterization of combined climate change/management effects on carbon and nitrogen biogeochemistry. Hence, we will evaluate the influence of different management options and current and future climate changes on the soil microbiome and associated biogeochemical processes in the plant-soil-system, on nitrogen use efficiency, on biosphere-atmosphere exchange of greenhouse gases as well as on leaching of environmentally relevant compounds. For this purpose, we simulate the predicted climate change in the region by translocation of large lysimeters (1m2, 1.4m depth; TERENO lysimeters, translocated in 2011) for measurements of biosphere-atmosphere hydrosphere exchange of environmentally relevant C and N compounds as well as by newly transferred smaller plant-soil-mesocosms used for destructive biogeochemical process studies. By closely linking this experimental work with biogeochemical and

  16. Seismicity, structure and tectonics in the Arctic region

    Institute of Scientific and Technical Information of China (English)

    Masaki Kanao; Vladimir D. Suvorov; Shigeru Toda; Seiji Tsuboi

    2015-01-01

    The“Arctic”region, where the North Pole occupies the center of the Arctic Ocean, has been affecting the environmental variation of the Earth from geological time to the present. However, the seismic activities in the area are not adequately monitored. Therefore, by conducting long term monitoring of seismic phenomenon as sustainable parameters, our understanding of both the tectonic evolution of the Earth and the dynamic interaction between the cryosphere and geosphere in surface layers of the Earth will increase. In this paper, the association of the seismicity and structure of the Arctic region, particularly focused on Eurasian continent and surrounding oceans, and its relationship with regional evolution during the Earth’s history is studied. The target areas cover representative tectonic provinces in the Eurasian Arctic, such as the wide area of Siberia, Baikal Rift Zone, Far East Russia, Arctic Ocean together with Greenland and Northern Canada. Based on discussion including characteristics of seismicity, het-erogeneous structure of the crust and upper mantle, tectonic history and recent dynamic features of the Earth’s surface in the Arctic are summarized.

  17. Planets and satellites: tectonic twins

    Science.gov (United States)

    Kochemasov, G. G.

    2015-10-01

    There are only three solid planet-satellite pairs in the Solar system: Earth -Moon, Mars -Phobos, Pluto - Charon. For the first two pairs tectonic analogies were shown and explained by moving them in one circumsolar orbit. As it is known from the wave planetology [3, 4, 6], "orbits make structures". For the third pair the same was stated as a prediction based on this fundamental rule. Global tectonic forms of wave origin appear in cosmic bodies because they move in keplerian orbits with periodically changing accelerations. Warping bodies waves have a stationary character and obeying wave harmonics lengths. Starting from the fundamental 2πR-long wave 1 making the ubiquitous tectonic dichotomy (two-face appearance) warping wave lengths descend along harmonics. Very prominent along with the wave 1 are waves 2 responsible for tectonic sectoring superimposed on the wave 1 segments. Practically all bodies have traces of shorter waves making numerous polygons (rings) often confused with impact craters. Earth and the Moon moving in one circumsolar orbit both are distorted by wave 1, wave 2 and wave 4 features aligned along extent tectonic lines [4, 5]. At Earth they are: Pacific Ocean (2πR-structure) and Indian Ocean (πR-structure) from both ends with Malay Archipelago (πR/4-structure) in the middle. At Moon they are: Procellarum Ocean (2πR) and SPA Basin (πR) from ends and Mare Orientale (πR/4) in the middle. A regular disposition is surprising. Both Oceans and Basin occur on opposite hemispheres, lying in the middle both ring structures occur in the boundary between two hemispheres and are of the same relative size. These triads stretch along lines parallel to the equator (Earth) and with the angle about 30 degrees to it (Moon) indicating at a different orientation of the rotation axes in the ancient time [2]. On the whole, one could speak about a "lunar mould" of Earth [5] (Fig. 1-3). Another tectonic twin is the pair Mars -Phobos. Both bodies sharing one

  18. Mars crustal magnetism, plate tectonics, and more

    Science.gov (United States)

    Connerney, J.; Acuna, M.; Ness, N.

    Mars has no global magnetic field of internal origin, but must have had one in the past when the crust acquired intense magnetization, presumably by cooling in the presence of an Earth-like magnetic field (thermoremanent magnetization or TRM). The Mars crust is at least an order of magnitude more intensely magnetized than that of the Earth. The apparent lack of magnetization associated with major impact basins suggests that the crust acquired magnetic remanence early in its history, about 4 billion years ago. A new map of the magnetic field of Mars, compiled at ˜ 400 km mapping altitude by Mars Global Surveyor, is presented here. The spatial resolution and sensitivity of this global map is unprecedented, inviting geologic interpretation heretofor reserved for aeromagnetic and ship surveys on Earth. These data provide new insight into the origin and evolution of the Mars crust. The apparent lack of magnetization associated with volcanic provinces may indicate that the magnetic layer resides within a few km of the surface, requiring magnetization intensity of order few 100 A/m, almost unthinkable. Two parallel great faults are identified in Terra Meridiani by offset magnetic field contours. They appear similar to transform faults that occur in oceanic crust on Earth, and describe the relative motion of two ancient Mars plates on the surface of a sphere. The magnetic imprint in Meridiani is consistent with that observed above a mid-ocean ridge on Earth. It is a relic of an era of plate tectonics on Mars, an era of crustal spreading, rifting, plate motions, and widespread volcanism following the demise of the dynamo. We present this new data in the context of the early development of plate tectonics on Earth, as advanced by the Vine-Matthews hypothesis and the work of W. Jason Morgan and others. Finally, we discuss the next logical steps in Mars exploration: magnetic surveys on global and regional scales.

  19. Accretion tectonics and crustal structure in Alaska

    Science.gov (United States)

    Coney, P.J.; Jones, D.L.

    1985-01-01

    wedging were important processes in northern Cordilleran tectonic evolution. ?? 1985.

  20. The Aegean: A natural laboratory for tectonics

    International Nuclear Information System (INIS)

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

  1. The relationship between soil physical properties and alpine plant diversity on Qinghai-Tibet Plateau

    Directory of Open Access Journals (Sweden)

    Lin Tang

    2015-04-01

    Full Text Available Through a large-scale research, we examined the heterogeneity of soil properties and plant diversity, as well as their relationships across alpine grassland types on Qinghai-Tibet Plateau. The soil pH and EC value increased with the constant deepening of the soil in all the three alpine grassland types which in order of absolute value in every soil layer were alpine desert steppe, alpine steppe and alpine meadow. Among the three grassland types, the alpine meadow possessed the highest SM but the lowest SBD. For plant diversity, alpine meadow was the highest, alpine desert steppe ranked the second and alpine steppe was the last. SM and SBD were the highest influential soil physical properties to species richness, but with opposite effects.

  2. The onset of alpine pastoral systems in the Eastern Alps

    Science.gov (United States)

    Oeggl, Klaus; Festi, Daniela; Putzer, Andreas

    2015-04-01

    Since the discovery of the Neolithic glacier mummy "Ötzi" in the nival belt of the main Alpine ridge, the onset of alpine pasture is matter of a highly controversial debate both in archaeology and in palaeo-ecology of the Eastern Alps. The implication is that his sojourn in the high-altitudes of the Alps is considered to be connected with pastoral nomadism. Regrettably any archaeological evidence for the existence of such Neolithic alpine pastoral systems is missing up to now and the assumption is based on palynological data only. However, also the palynological record is ambiguous, because pasture indicators in the alpine regions react positive on grazing as well as on fertilization induced by a higher runoff of precipitation. Thus alpine pasture indicators reflect both grazing pressure and climatic change. Anyhow, alpine pastoral systems are a common practice in Alpine animal husbandry, but from an economic point of view such a seasonal vertical transhumance is costly. There are three main reasons for its practice: i) climatic, ii) economic (mainly in connection with population pressure or mining activities), and iii) cultural ideology. In this study we tested the above mentioned reasons in an interdisciplinary study on the beginning of pastoral activities in high altitudes in the central part of the Eastern Alps. This is conducted by palynological analyses of peat deposits situated in the vicinity of the timberline (1600 - 2400 m a.s.l.) combined with archaeological surveys. The investigated sites are located in traditional Alpine transhumance regions and aligned on a transect through the central part of the Eastern Alps. The studies reveal that grazing pressure is reflected since the Bronze Age, which is corroborated by archaeological findings in the vicinity of the investigated sites.

  3. Earnings and Performance in Women's Professional Alpine Skiing

    OpenAIRE

    Che, XiaoGang; Humphreys, Brad

    2012-01-01

    We test the predictions of tournament theory using data from competitions in the FIS Alpine Skiing World Cup. Based on data from more than 60 Giant Slalom and Downhill events held over the period 2001-2010, female professional Alpine skiers respond to tournament incentives; times in both events were faster in events with a larger spread in the prize distribution when controlling for course characteristics and the number of contestants in the race. In this setting women engage in vigorous comp...

  4. ALPINE MAGMATIC-METALLOGENIC FORMATIONS OF THE NORTHWESTERN AND CENTRAL DINARIDES

    Directory of Open Access Journals (Sweden)

    Jakob Pamić

    1997-12-01

    Full Text Available In the paper are presented basic geological, petrologieca1, geochemi-cal and mineral deposit data for five main magmatic-metallogenic formations of the northwestern and central Dinarides: (lThe Permo Triassic rifting related andesite-diorite formations; (2 The Jurassic-Lower Cretaceous accretionary (ophiolite formations; (3 The Upper Cretaceous-Paleogene subduction related basalt-rhyohite formations; (4 The Paleogene collisional granite formations, and (5 The Oligo-cene-Neogene postsubduction andesite formations. All these magmatic-metallogenic formations originated in different geotectonic settings during the Alpine evolution of the Dinaridic parts of thc Tethys and the postorogenic evolution of the Paratethys and the Pannonian Basin, respectively.

  5. The buried shape of an alpine valley from gravity surveys, seismic and ambient noise analysis

    Science.gov (United States)

    Barnaba, C.; Marello, L.; Vuan, A.; Palmieri, F.; Romanelli, M.; Priolo, E.; Braitenberg, C.

    2010-02-01

    It has long been observed that damage due to earthquakes depends greatly on local geological conditions. Alpine valleys represent a typical populated environment where large amplifications can take place owing to the presence of surface soils with poor mechanical properties combined to complex topography of the rock basin. In the framework of the EU Interreg IIIB SISMOVALP Project `Seismic hazard and alpine valley response analysis', a stretch of the Tagliamento River Valley (TRV), located in the north-western part of the Friuli Region (Italy) and close to the epicentre of the 1976 Mw = 6.4 earthquake, has been investigated with the aim to define the buried shape of the valley itself. Two non-invasive, low cost, independent geophysical methods were used: (i) detailed gravity survey and (ii) H/V spectral ratio (HVSR) of microtremors. Because of structural geological complexity and active tectonics of the Friuli region, an irregular valley shape was expected in this area. The independent analysis performed by gravity and passive noise, and complemented with refraction seismic velocity profiles, confirms this hypothesis and leads to two models that were consistent, but for some small scale details. The maximum depth estimated is about 400-450 m in the southern part of the valley, while a mean value of 150-180 m is estimated in the northern part. The sediment thickness obtained for this stretch of the TRV is quite large if compared to eastern Alps Plio-Quaternary rates; therefore the valley shape imaged by this study better corresponds to the top of carbonate rocks. Finally, on the basis of the obtained morphology and some direct measurements, we conclude that the TRV features an overall 1-D seismic response (i.e. the resonance is related only to the sediment thickness rather than to the cross-section shape), but in its deepest part some limited 2-D effects could take place.

  6. Tectonic stratification and seismicity of the accretionary prism of the Azerbaijani part of Greater Caucasus

    Science.gov (United States)

    Alizade, Akif; Kangarli, Talat; Aliyev, Fuad

    2013-04-01

    The Greater Caucasus has formed during last stage of the tectogenesis in a geodynamic condition of the lateral compression, peculiar to the zone pseudo-subduction interaction zone between Northern and Southern Caucasian continental microplates. Its present day structure formed as a result of horizontal movements of the different phases and sub-phases of Alpine tectogenesis (from late Cimmerian to Valakhian), and is generally regarded as zone where, along Zangi deformation, the insular arc formations of the Northern edge of South Caucasian microplate thrust under the Meso-Cenozoic substantial complex contained in the facials of marginal sea of Greater Caucasus. The last, in its turn, has been pushed beneath the North-Caucasus continental margin of the Scythian plate along Main Caucasus Thrust fault. Data collected from the territory of Azerbaijan and its' sector of the Caspian area stands for pseudo-subduction interaction of microplates which resulted in the tectonic stratification of the continental slope of Alpine formations, marginal sea and insular arc into different scale plates of south vergent combined into napping complexes. In the orogeny's present structure, tectonically stratified Alpine substantial complex of the marginal sea of Greater Caucasus bordered by Main Caucasus and Zangi thrusts, is represented by allochthonous south vergent accretionary prism in the front of first deformation with its' root buried under the southern border of Scythian plate. Allocated beneath mentioned prism, the autochthonous bedding is presented by Meso-Cenosoic complex of the Northern flank of the South-Caucasian miroplate, which is in its' turn crushed and lensed into southward shifted tectonic microplates gently overlapping the northern flank of Kura flexure along Ganykh-Ayrichay-Alyat thrust. Data of real-time GPS measurement of regional geodynamics indicates that pseudo-subduction of South Caucasian microplate under the North Caucasian microplate still continues during

  7. The Tectonic Potentials of Concrete

    DEFF Research Database (Denma