Sample records for alpine tectonic evolution

  1. Complex tectonic and tectonostratigraphic evolution of an Alpine foreland basin: The western Duero Basin and the related Tertiary depressions of the NW Iberian Peninsula (United States)

    Martín-González, F.; Heredia, N.


    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

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

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


    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

  3. South Scandinavian joints and Alpine/Atlantic-ridge tectonics

    Directory of Open Access Journals (Sweden)

    A. E. Scheidegger


    Full Text Available Field observations and studies of the joints and dykes in an area shed light on its younger tectonic development; thus, joint orientations measured in Southern Sweden and in Norway have been statistically studied and compared regarding their tectonic significance with studies from Europe and the mid-Atlantic ridge. The present investigation indicates that the surface joint systems in Sweden agree with those in Europe; they are the result of the intracratonic stress field and the mechanical response associated with the Alpine orogeny. The stress systems in Southern Norway, on the other hand, are the result of the ongoing extensional or wrench-fault tectonism in the Atlantic crust associated with the stresses near the mid-Atlantic ridge, which act normally to the contiguous coastlines from Scandinavia to France, Portugal and North Africa.

  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.


    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 (United States)

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


    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)


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


    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 the Jurassic Pacific Plate (United States)

    Nakanishi, M.; Ishihara, T.


    We present the tectonic evolution of the Jurassic Pacific plate based on magnetic anomly lineations and abyssal hills. The Pacific plate is the largest oceanic plate on Earth. It was born as a microplate aroud the Izanagi-Farallon-Phoenix triple junction about 192 Ma, Early Jurassic [Nakanishi et al., 1992]. The size of the Pacific plate at 190 Ma was nearly half that of the present Easter or Juan Fernandez microplates in the East Pacific Rise [Martinez et at, 1991; Larson et al., 1992]. The plate boundary surrounding the Pacific plate from Early Jurassic to Early Cretaceous involved the four triple junctions among Pacific, Izanagi, Farallon, and Phoenix plates. The major tectonic events as the formation of oceanic plateaus and microplates during the period occurred in the vicinity of the triple junctions [e.g., Nakanishi and Winterer, 1998; Nakanishi et al., 1999], implying that the study of the triple junctions is indispensable for understanding the tectonic evolution of the Pacific plate. Previous studies indicate instability of the configuration of the triple junctions from Late Jurassic to Early Cretaceous (155-125 Ma). On the other hand, the age of the birth of the Pacific plate was determined assuming that all triple junctions had kept their configurations for about 30 m.y. [Nakanishi et al., 1992] because of insufficient information of the tectonic history of the Pacific plate before Late Jurassic.Increase in the bathymetric and geomagnetic data over the past two decades enables us to reveal the tectonic evolution of the Pacific-Izanagi-Farallon triple junction before Late Jurassic. Our detailed identication of magnetic anomaly lineations exposes magnetic bights before anomaly M25. We found the curved abyssal hills originated near the triple junction, which trend is parallel to magnetic anomaly lineations. These results imply that the configuration of the Pacific-Izanagi-Farallon triple junction had been RRR before Late Jurassic.

  8. Alpine tectonics of granites in basement of Ysyk-Köl Basin, northern Tien Shan (United States)

    Leonov, M. G.; Przhiyalgovsky, E. S.; Lavrushina, E. V.; Poleshchuk, A. V.; Rybin, A. K.


    The Ysyk-Köl Basin filled with Lower Jurassic-Quaternary sedimentary rocks is the largest intermontane negative structural unit of the northern Tien Shan. The basement of this basin is composed of Precambrian-Paleozoic rocks, largely of Ordovician and Silurian granitoids exposed in mountain ranges of the basin framework and as separate anticlinal domes situated in areas occupied by the Mesozoic-Cenozoic sedimentary cover. The postmagmatic tectonic internalstructure of the Chonkurchak (Chunkurchak), Kyzyl-Choku, Kyzyl-Bulak, and Prishib massifs emplaced in the basement, as well as their relationships to the sedimentary cover, are described in the paper. The study was carried out using the morphostructural method, detailed geological mapping, structural kinematic analysis, and petrographic examination of rocks. The internalstructure of Paleozoic granites in the basement and indications of their 3D tectonic flow are characterized. It is shown that granites underwent 3D deformation after their emplacement in the consolidated crust, and this process had a substantial influence on tectonic processes at the plate and orogenic stages of regional evolution.

  9. 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

  10. Rapid biological speciation driven by tectonic evolution in New Zealand (United States)

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


    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.

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


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


    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...

  12. A window for plate tectonics in terrestrial planet evolution? (United States)

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


    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.

  13. History and Evolution of Precambrian plate tectonics (United States)

    Fischer, Ria; Gerya, Taras


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

  14. Tectonic evolution of northern Wadi Araba, Jordan (United States)

    Atallah, Mohammad


    In the area east of northern Wadi Araba several phases of tectonic fracturing can be distinguished. The oldest is of Precambrian age and is represented by a system of dikes. A second, pre-Cretaceous, tectonic phase is represented by a distinct joint system, which is restricted to the Cambrian sediments and has not cut the Cretaceous sediments. The major tectonic movements which lead to the formation of the Dead Sea rift produced faults and joint systems which cut all rock sequences. The major deformation of the area started in the early Tertiary, when the accumulation of the SE-NW directed compressive stresses produced fold structures which are older than the rift movements. As a result of this stress a conjugate system of fractures was produced; ESE-trending right-lateral (antithetic) faults and SSE-trending left-lateral (synthetic) faults. A major group of tensional faults and fractures, trending 130°, was produced due to this compression. The major displacement along the rift followed the formation of the above mentioned faults. These fault systems dissected the area into different blocks. As the compression continued, the faults and the blocks between them were rotated relative to each other. Two phases of rotational movements were recorded, contemporaneous with the two phases of the rift formation. During its northward movement, the Arabian plate came into collision with the Sinai-Palestine plate in the Dahal area in northern Wadi Araba. Various indications prove that the Wadi Araba fault is still active and the northward displacement of the Arabian plate along this fault continues in recent time.

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

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


    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

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

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


    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

  17. Polyphase tectonic subsidence evolution of the Vienna Basin inferred from quantitative subsidence analysis of the northern and central parts (United States)

    Lee, Eun Young; Wagreich, Michael


    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.

  18. Tertiary tectonic and sedimentological evolution of the South Carpathians foredeep: tectonic vs eustatic control

    Energy Technology Data Exchange (ETDEWEB)

    Rabagia, T. [Prospectiuni S.A., Hydrocarbon Div., Bucharest (Romania); Matenco, L. [Bucharest Univ., Faculty of Geology and Geophysics, Bucharest (Romania)


    A detailed seismic sequence stratigraphy study based on the dense network of seismic profiles is integrated with structural observations from interpreted geological sections to derive a tectonic and sedimentological model for the Miocene-Pliocene evolution of the South Carpathians foredeep (Getic Depression). Following Paleogene and older orogenic phases, the first tectonic event which affected the studied areas was characterised by Early Miocene large scale extension to transtension which is responsible for the opening of the Getic Depression as a dextral pull-apart basin. Further Middle Miocene contraction caused WNW-ESE oriented thrusts and associated piggy-back basins. The last tectonic episode recognised in the studied areas relates to general transpressive deformations during the Late Miocene-Early Pliocene interval, a first NW-SE oriented dextral episode is followed by second N-S sinistral deformations. The detailed sequence stratigraphy study allows for the definition of the dominant tectonic control of the sedimentary sequences in foreland basins. A eustatic control may be associated, but has a clear subordinated character. (Author)

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

    Institute of Scientific and Technical Information of China (English)

    M.S.Njome; C.E.Suh


    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.

  20. Continental Transform Boundaries: Tectonic Evolution and Geohazards

    Directory of Open Access Journals (Sweden)

    Michael Steckler


    Full Text Available Continental transform boundaries cross heavily populated regions, and they are associated with destructive earthquakes,for example, the North Anatolian Fault (NAFacross Turkey, the Enriquillo-Plantain Garden fault in Haiti,the San Andreas Fault in California, and the El Pilar fault in Venezuela. Transform basins are important because they are typically associated with 3-D fault geometries controlling segmentation—thus, the size and timing of damaging earthquakes—and because sediments record both deformation and earthquakes. Even though transform basins have been extensively studied, their evolution remains controversial because we don’t understand the specifics about coupling of vertical and horizontal motions and about the basins’long-term kinematics. Seismic and tsunami hazard assessments require knowing architecture and kinematics of faultsas well as how the faults are segmented.

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

    Institute of Scientific and Technical Information of China (English)

    Wang Hongzhen; Li Sitian


    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.

  2. Tectonic evolution of the Qinling orogen, China: Review and synthesis (United States)

    Dong, Yunpeng; Zhang, Guowei; Neubauer, Franz; Liu, Xiaoming; Genser, Johann; Hauzenberger, Christoph


    This contribution reviews the tectonic structure and evolution of the Qinling orogenic belt, which extends east-west nearly 2500 km across Central China and is a giant orogenic belt formed by the convergence and collision between North China and South China Blocks. The principal tectonic elements including metamorphic basement and its Neoproterozoic to Triassic cover, ophiolitic sutures, nature and ages of granitoid belts, provenance studies and tectonometamorphic studies of metamorphic belts allow tracing the polarity of two stages of plate convergence and collision and the further tectonic history. In this review, we present new distribution maps of the Early Paleozoic ophiolites and associated volcanics in the Shangdan suture zone and the Middle Devonian-Middle Triassic ophiolitic melange in the Mianlue suture zone, as well as the maps of granitoid and metamorphic belts displaying various ages (Silurian-Devonian, Triassic, Late Jurassic-Early Cretaceous). These maps allow better constrain the polarity of subduction and collision. We also discuss the significance of the Early Cretaceous Yanshanian events, which represent a linkage between tectonic events in the Tethyan and East China/Pacific realms. Two ophiolitic sutures, the Shangdan suture zone in the north and the Mianlue suture in the south, have been intensively studied during the past two decades. The Qinling Orogen is divided into the North Qinling and the South Qinling Belts by the Shangdan suture zone, and this suture zone is thought to represent the major suture separating the North China and South China Blocks. However, the timing and processes of convergence between these two blocks have been disputed for many years, and Silurian-Devonian or Late Triassic collision has been proposed as well. Based on the recent results, a detailed convergent evolutionary history between the North China and South China Blocks along the Shangdan suture is here proposed. The Mianlue suture zone is well documented and

  3. Tectonic and stratigraphic evolution in South Alboran Sea (Morocco) (United States)

    D'Acremont, E.; Gorini, C.; El Abbassi, M.; Farran, M.; Leroy, S.; Mercier De Lepinay, B. F.; Migeon, S.; Poort, J.; Ammar, A.; Smit, J.; Ercilla, G.; Alonso, B.; Scientific Team of the Marlboro project


    The Alboran Basin, in western Mediterranean, concentrates on a relatively small surface and densely-populated, a large structural complexity linked to seismic activity with recurrent mass-transport deposits that may trigger tsunamis. It was formed by Oligo-Miocene extension while tectonic inversion occurred since the Late Miocene (Tortonian) due to the African-European collision. This North-South compression produces a conjugated fault system located in the central area from Al Hoceima to Andalusia. Numerous instabilities are linked to the recent and present-day seismic activity and show the link between seismicity and erosion-sedimentation processes. On the Andalusia margin the active structures have been identified and recently mapped in detail by using MBES data (including backscatter), and high-resolution seismic data. Such detailed studies have not yet been carried out on the Moroccan margin. The Marlboro-1 oceanographic cruise (R/V Côtes de la Manche, July 2011) has imaged and constrained active structures and associated sedimentary systems through seismic reflection data (MCS). The Xauen/Tofino banks (growth folds), the Alboran Ridge, and the Al Hoceima basin offshore Morocco have been selected because they constitute key-study areas that record a complete deformation history since the Tortonian. Active features including faults, growth folds, channels, mass transport deposits, contourites and volcanoes has provided first order tectonic and sedimentary markers of the basin's evolution. A high chrono-stratigraphical resolution will constitute the basis for reconstructing the evolution of this tectonically active area marked by strong seismic activity. The Marlboro-1 cruise will allow determining key-study area of the Marlboro-2 cruise scheduled for 2012 (R/V Téthys-II, CNFC Call). These cruises should allow for the acquisition of data necessary to characterize basin morphology, active tectonic and sedimentary structures and also make the link with existing

  4. 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


    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.

  5. Tectonic subsidence history and thermal evolution of the Orange Basin (United States)

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


    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.

  6. Structural and metamorphic evolution of serpentinites and rodingites recycled in the Alpine subduction wedge (United States)

    Zanoni, D.; Rebay, G.; Spalla, M. I.


    Hydration-dehydration of mantle rocks affects the viscosity of the mantle wedge and plays a prominent role in subduction zone tectonics, facilitating marble cake-type instead of large-slice dynamics. An accurate structural and petrologic investigation of serpentinites from orogenic belts, supported by their long-lived structural memory, can help to recognize pressure-sensitive mineral assemblages for deciphering their P-prograde and -retrograde tectonic trajectories. The European Alps preserve large volumes of the hydrated upper part of the oceanic lithosphere that represents the main water carrier into the Alpine subduction zone. Therefore, it is important to understand what happens during subduction when these rocks reach P-T conditions proximal to those that trigger the break-down of serpentine, formed during oceanic metamorphism, to produce olivine and clinopyroxene. Rodingites associated with serpentinites are usually derived from metasomatic ocean floor processes but rodingitization can also happen in subduction environments. Multiscale structural and petrologic analyses of serpentinites and enclosed rodingites have been combined to define the HP mineral assemblages in the Zermatt-Saas ophiolites. They record 3 syn-metamorphic stages of ductile deformation during the Alpine cycle, following the ocean floor history that is testified by structural and metamorphic relics in both rock types. D1 and D2 developed under HP to UHP conditions and D3 under lower P conditions. Syn-D2 assemblages in serpentinites and rodingites indicate conditions of 2.5 ± 0.3 GPa and 600 ± 20°C. This interdisciplinary approach shows that the dominant structural and metamorphic imprint of the Zermatt-Saas eclogitized serpentinites and rodingites developed during the Alpine subduction and that subduction-related serpentinite de-hydration occurred exclusively at Pmax conditions, during D2 deformation. In contrast, in the favourable rodingite bulk composition (Ca-rich), hydrated minerals

  7. 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

  8. Earthquake-related Tectonic Deformation of Soft-sediments and Its Constraints on Basin Tectonic Evolution

    Institute of Scientific and Technical Information of China (English)

    LU Hongbo; ZHANG Yuxu; ZHANG Qiling; XIAO Jiafei


    The authors introduced two kinds of newly found soft-sediment deformation-syn-sedimentary extension structure and syn-sedimentary compression structure, and discuss their origins and constraints on basin tectonic evolution. One representative of the syn-sedimentary extension structure is syn-sedimentary boudinage structure, while the typical example of the syn-sedimentary compression structure is compression sand pillows or compression wrinkles. The former shows NW-SE-trending contemporaneous extension events related to earthquakes in the rift basin near a famous Fe-Nb-REE deposit in northern China during the Early Paleozoic (or Mesoproterozoic as proposed by some researches), while the latter indicates NE-SW-trending contemporaneous compression activities related to earthquakes in the Middle Triassic in the Nanpanjiang remnant basin covering south Guizhou, northwestern Guangxi and eastern Yunnan in southwestern China. The syn-sedimentary boudinage structure was found in an earthquake slump block in the lower part of the Early Paleozoic Sailinhudong Group, 20 km to the southeast of Bayan Obo, Inner Mongolia, north of China. The slump block is composed of two kinds of very thin layers-pale-gray micrite (microcrystalline limestone) of 1-2 cm thick interbedded with gray muddy micrite layers with the similar thickness. Almost every thin muddy micrite layer was cut into imbricate blocks or boudins by abundant tiny contemporaneous faults, while the interbedded micrite remain in continuity. Boudins form as a response to layer-parallel extension (and/or layer-perpendicular flattening) of stiff layers enveloped top and bottom by mechanically soft layers. In this case, the imbricate blocks cut by the tiny contemporaneous faults are the result of abrupt horizontal extension of the crust in the SE-NW direction accompanied with earthquakes. Thus, the rock block is, in fact, a kind of seismites. The syn-sedimentary boudins indicate that there was at least a strong earthquake

  9. Tectonic geomorphological characteristics for evolution of the Manas Lake

    Institute of Scientific and Technical Information of China (English)


    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.

  10. 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)


    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.

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

  12. A planetary perspective on Earth evolution: Lid Tectonics before Plate Tectonics (United States)

    Piper, John D. A.


    Plate Tectonics requires a specific range of thermal, fluid and compositional conditions before it will operate to mobilise planetary lithospheres. The response to interior heat dispersion ranges from mobile lids in constant motion able to generate zones of subduction and spreading (Plate Tectonics), through styles of Lid Tectonics expressed by stagnant lids punctured by volcanism, to lids alternating between static and mobile. The palaeomagnetic record through Earth history provides a test for tectonic style because a mobile Earth of multiple continents is recorded by diverse apparent polar wander paths, whilst Lid Tectonics is recorded by conformity to a single position. The former is difficult to isolate without extreme selection whereas the latter is a demanding requirement and easily recognised. In the event, the Precambrian palaeomagnetic database closely conforms to this latter property over very long periods of time (~ 2.7-2.2 Ga, 1.5-1.3 Ga and 0.75-0.6 Ga); intervening intervals are characterised by focussed loops compatible with episodes of true polar wander stimulated by disturbances to the planetary figure. Because of this singular property, the Precambrian palaeomagnetic record is highly effective in showing that a dominant Lid Tectonics operated throughout most of Earth history. A continental lid comprising at least 60% of the present continental area and volume had achieved quasi-integrity by 2.7 Ga. Reconfiguration of mantle and continental lid at ~ 2.2 Ga correlates with isotopic signatures and the Great Oxygenation Event and is the closest analogy in Earth history to the resurfacing of Venus. Change from Lid Tectonics to Plate Tectonics is transitional and the geological record identifies incipient development of Plate Tectonics on an orogenic scale especially after 1.1 Ga, but only following break-up of the continental lid (Palaeopangaea) in Ediacaran times beginning at ~ 0.6 Ga has it become comprehensive in the style evident during the

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


    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

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


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


    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...

  15. Pollen sensitivity to ultraviolet-B (UV-B) suggests floral structure evolution in alpine plants. (United States)

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


    Various biotic and abiotic factors are known to exert selection pressures on floral traits, but the influence of ultraviolet-B (UV-B) light on the evolution of flower structure remains relatively unexplored. We have examined the effectiveness of flower structure in blocking radiation and the effects of UV-B on pollen viability in 42 species of alpine plants in the Hengduan Mountains, China. Floral forms were categorized as either protecting or exposing pollen grains to UV-B. The floral materials of plants with exposed and protected pollen grains were able to block UV-B at similar levels. Exposure to UV-B radiation in vitro resulted in a significantly greater loss of viability in pollen from plant species with protective floral structures. The pronounced sensitivity of protected pollen to UV-B radiation was associated with the type of flower structure. These findings demonstrate that UV-B plays an important role in the evolution of protective floral forms in alpine plants.

  16. Tectonic and climatic control on geomorphological and sedimentary evolution of the Mercure basin, southern Apennines, Italy (United States)

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


    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

  17. Igneous and tectonic evolution of Venusian and terrestrial coronae (United States)

    Kargel, J. S.; Komatsu, G.


    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.

  18. Geodynamic controls on a salt giant formation. The Messinian salinity crisis and the tectonic evolution of the westernmost Mediterranean (United States)

    Garcia-Castellanos, Daniel


    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

  19. Active tectonics west of New Zealand's Alpine Fault: South Westland Fault Zone activity shows Australian Plate instability (United States)

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


    The 300 km long South Westland Fault Zone (SWFZ) is within the footwall of the Central Alpine Fault (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.

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

    Institute of Scientific and Technical Information of China (English)


    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.

  1. Tectonic Evolution of the Northern Continental Margin of North China Platform in Middle Proterozoic

    Institute of Scientific and Technical Information of China (English)

    Xu Zhongyuan; Liu Zhenghong


    An orogenic belt developed in late middle Proterozoic in the northern margin of North China Plate extends from Inner Mongolia to Western Liaoning Province and Eastern Jilin Province. It is over 2000km long. The orogenic belt was formed by collision between North China Platform and Siberia Platform during the Rodinian Super- Continent period. From sedimentary formation, magmatic activity and crustal tectonic deformation, it is suggested that along the tectonic belt the paleocontinental margin experienced four stages of tectonic evolution in middle Proterozoic, they are: continental margin rift,passive continental margin, active continental margin and collisional orogenic stages.

  2. Tectonic evolution and mantle structure of the Caribbean

    NARCIS (Netherlands)

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


    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


    Institute of Scientific and Technical Information of China (English)

    Lei SHAO; Chuanlian LIU; Karl STATTEGGER


    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.

  4. Tectonic Characteristics and Evolution of Bohai Bay Basin, China

    Institute of Scientific and Technical Information of China (English)

    LIU Pengju; ZHANG Meisheng; SUN Xiaomeng; YANG Baojun


    Synthetical analyzing the deep geophysical data within Bohai bay basin the authors detect the deep crustal structure presenting high geothermal flux, thinned crust and arched Moho discontinuity, and the basin basement belongs to rigid continental crust. The development of the basin was controlled by two - dimensional faults in NNE and NWW directions. The tectonic units of the basin can be subdivided into three structural divisions: the east, middle and west division. The basin is considered as a continental rift. The tectonic background and regional right - lateral stress field during the late Cretaceous and Paleogene were a compound result of the Kula Plate W - directional subducting under Eurasia Continental Plate in 80 ~ 74Ma and the Philippine sea Plate W -directional subducting under the Eurasia Continental Plate since 60Ma, the long-rang effect of the India Continental Plate wedging into the Eurasia Continental Plate and of the Siberia Plate SE - directional relatively moving.

  5. Tectonic Evolution of Bell Regio, Venus: Regional Stress, Lithospheric Flexure, and Edifice Stresses (United States)

    Rogers, P. G.; Zuber, M. T.


    Analyses of the tectonic features associated with large volcanoes provide important insight into the relationship between volcanic and tectonic processes and the stress state of a planet's crust over time, and provide constraints on the local and regional geologic evolution. This investigation focuses on the tectonism and volcanism of Bell Regio, a major highland uplift n Venus. The stress environments and resulting tectonic features associated with the major volcanic edifices in this region are examined using Magellan ynthetic aperture radar (SAR) images and altimeter measurements of topography. The major volcanoes of Bell Regio, Tepev Mons and the "Eastern Volcanic Center" (EVC), exhibit tectonic characteristics that are unique relative to other volcanic edifices on Venus. The most prominent distinctions are the lack of large rift zones within the overall highland uplift and the presence of radial tectonic and concentric fractures associated with the major edifices. This study examines the regional stress field in Bell Regio through analysis of structural features believed to be a consequence of lithospheric flexure due to volcanic loading and tectonic features that likely resulted from edifice stresses associated with magma chamber inflation.

  6. 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


    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.

  7. Tectonic evolution of the East Junggar terrane, CAOB (United States)

    Xu, Xing-Wang


    The East Junggar terrane is one of the important tectonic units of the Central Asian Orogenic Belt (CAOB; Zonenshain et al., 1990). Debate surrounds the tectonics of the East Junggar area, including tectonic setting, age, basement nature, subduction polarity and collisional time between the East Junggar terrane and Junggar block (e.g., Xiao et al., 2008, 2011; Long et al., 2012; Huang et al., 2012). Among the two popular models, one suggests that the Junggar is a continental block (e.g. Zhang et al., 1984, 1993; Watson et al., 1987; Xiao et al., 1992; He et al., 1994; Li et al., 2000; Charvet et al., 2001, 2007; Xu et al., 2003; Zhao et al., 2003; Buslov et al., 2004; Xu and Ma, 2004; Dong et al., 2009; Bazhenov et al., 2012; Choulet et al., 2012; Zhang et al., 2012). The other model proposes that the Junggar has a basement of Paleozoic oceanic crust (e.g., Carroll et al., 1990; Zheng et al., 2007) or oceanic island arc complexes (e.g., Coleman, 1989; Chen and Jahn, 2004; Windley et al., 2007) of the Altaid Paleozoic rocks (e.g., Sengör et al., 1993; Sengör and Natal'in, 1996; Allen and Vincent, 1997; Filippova et al., 2001; Xiao et al., 2004a, 2004b, 2008, 2009, 2010a, 2010b, 2012). The tectonics in the Eastern Junggar area are interpreted to be related to late Paleozoic intra-oceanic accretion induced by northward subduction of the Junggar oceanic lithosphere (e.g. Xiao et al., 2008, 2009; Biske and Seltmann, 2010; Wan et al., 2011; Yang et al., 2011) or by the southward subduction of the Paleo-Asian oceanic lithosphere (Zhang et al., 2004; Wong et al., 2010; Su et al., 2012). Recently, we did detailed field survey and petrological, geochemical and chronological analysis of the metamorphosed volcanic rocks and magmatic rocks, and new discovered gneiss and magnetite quartzite enclaves from the Taheir tectonic window in the East Junggar region which is situated between the Zaisan-Erqis-the Main Mongolian Lineament-suture and the Kelameili suture. The new results

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

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


    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. Understanding the Interior Evolution of Mercury from Its Tectonic History (United States)

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


    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

  10. Evolution of ancient Lake Ohrid: a tectonic perspective (United States)

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


    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.

  11. Evolution of ancient Lake Ohrid: a tectonic perspective

    Directory of Open Access Journals (Sweden)

    N. Hoffmann


    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.

  12. Evolution of ancient Lake Ohrid: a tectonic perspective

    Directory of Open Access Journals (Sweden)

    N. Hoffmann


    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.

  13. Cenozoic tectonic evolution of the Bohai Bay Basin and its coupling relationship with Pacific Plate subduction (United States)

    Liang, Jintong; Wang, Hongliang; Bai, Ying; Ji, Xinyuan; Duo, Xuemei


    The Bohai Bay Basin is a Mesozoic-Cenozoic rift basin in eastern China. Based mainly on a balanced-section analysis, this study compares the spatio-temporal differences of tectonic evolution in relation to strike-slip faults among different depressions within the basin. In combination with the analysis of subsidence characteristics, the study also attempts to clarify the Cenozoic tectonic evolution of the basin and its coupling relationship with the subduction of the Pacific Plate. It was found that: (1) the strike-slip faults were activated generally from south to north and from west to east during the Cenozoic; (2) there is a negative correlation between the intensity of tectonic activity in the Bohai Bay Basin and subduction rate of the Pacific Plate; and (3) the migration direction of the basin depocenters is consistent with the direction of Pacific Plate subduction.

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

    Institute of Scientific and Technical Information of China (English)

    LIU; Shaofeng; LI; Zhong; ZHANG; Jinfang


    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.

  15. 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


    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.

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

    DEFF Research Database (Denmark)

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


    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...

  17. 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


    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

  18. New constraints on the tectonic evolution of the Salton Trough (United States)

    Brothers, D.; Driscoll, N.; Kent, G.


    The Salton Trough is a critical structure where two very different styles of deformation meet; spreading-center dominated deformation to the south in the Gulf of California and dextral strike-slip deformation along the San Andreas fault system(SAF) to the north. Seismic CHIRP data acquired in the Salton Sea provide new constraints on the interaction between the San Andreas, San Jacinto and Imperial fault systems and reveal distinct changes in deformational style from north to south. Based on the stratal geometry observed in CHIRP profiles, we propose three distinct phases of tectonic deformation: (1) Late- Pleistocene transpression north of the Extra Fault Zone (EFZ) replaced by (2) late-Holocene differential subsidence south of the EFZ and (3) recent formation of the Brawley Seismic Zone (BSZ), a through-going crustal shear zone. An angular unconformity is observed to separate the folded and faulted (late?) Pleistocene strata of the Brawley Formation from the overlying Holocene Cahuilla Formation (CF). North of the EFZ reflectors in the CF suggest little to no active deformation. Conversely, south of the EFZ reflectors exhibit marked divergence with their dip systematically increasing with depth. Such a pattern of divergence indicates that the rate of sedimentation has kept pace with the rate of tectonically-induced accommodation. As such, it appears that the EFZ is a tectonic hinge zone delineating the northern limit of active subsidence, high heat flow, and volcanism. Furthermore, given the observed subsidence pattern, we predict the existence of a NE trending basin-bounding normal fault, or series of normal faults, near the southern shoreline of the Salton Sea. In our conceptual model, the early distributed faulting and transrotation between the San Andreas and San Jacinto faults accounts for the compressional folding observed in the Brawley Formation, but later gave way to extension-dominated deformation as significant slip became focused along the Imperial

  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. Three-phase tectonic evolution of the Andaman backarc basin

    Digital Repository Service at National Institute of Oceanography (India)

    KameshRaju, K.A.

    of evolution proposed by Curray 18 and di ffers in the timing of initial separation of Alcock and Sewell seamount complexes, which remains speculative; and in the proposition of propagation of the spreading rift. Based on high - resolution studies carried...

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

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


    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 (United States)

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


    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


    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 (United States)

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


    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


    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. Escape tectonics and foreland basin evolution: The Austrian-German Molasse basin (United States)

    Ortner, Hugo


    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

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

    DEFF Research Database (Denmark)

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


    of relaxation inversion (Nielsen et al. 2005). In conclusion, the Cenozoic structures in the North Sea area do not generally support ideas on Neogene basement tectonism. References: Clausen, O. R. and M. Huuse (1999). "Topography of the Top Chalk surface on- and offshore Denmark." Marine and Petroleum Geology......Abundant seismic sections and well data from the Cenozoic succession in the eastern North Sea area generally reveal normal faulting, salt tectonics and localized tectonic inversion. However, inferences on the Cenozoic dynamic evolution of the region require thorough analysis of interactions between...... 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...

  8. Tectonic Evolution and Petroleum Systems in the Junggar Basin

    Institute of Scientific and Technical Information of China (English)

    WANG Weifeng; CHEN Yequan


    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.

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

    NARCIS (Netherlands)

    Sissingh, W.


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

  10. Geology and Tectonic Evolution of the Kazdaǧ Massif (NW Anatolia) (United States)

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


    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)

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


    Lindhorst, Katja; Krastel, Sebastian; Wagner, Bernd


    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...

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

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


    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.

  13. Overview of geology and tectonic evolution of the Baikal-Tuva area. (United States)

    Gladkochub, Dmitry; Donskaya, Tatiana


    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

  14. Tectonic activity and the evolution of submarine canyons: The Cook Strait Canyon system, New Zealand (United States)

    Micallef, Aaron; Mountjoy, Joshu; Barnes, Philip; Canals, Miquel; Lastras, Galderic


    Submarine canyons are Earth's most dramatic erosional features, comprising steep-walled valleys that originate in the continental shelf and slope. They play a key role in the evolution of continental margins by transferring sediments into deep water settings and are considered important biodiversity hotspots, pathways for nutrients and pollutants, and analogues of hydrocarbon reservoirs. Although comprising only one third of continental margins worldwide, active margins host more than half of global submarine canyons. We still lack of thorough understanding of the coupling between active tectonics and submarine canyon processes, which is necessary to improve the modelling of canyon evolution in active margins and derive tectonic information from canyon morphology. The objectives of this study are to: (i) understand how tectonic activity influences submarine canyon morphology, processes, and evolution in an active margin, and (2) formulate a generalised model of canyon development in response to tectonic forcing based on morphometric parameters. We fulfil these objectives by analysing high resolution geophysical data and imagery from Cook Strait Canyon system, offshore New Zealand. Using these data, we demonstrate that tectonic activity, in the form of major faults and structurally-generated tectonic ridges, leaves a clear topographic signature on submarine canyon location and morphology, in particular their dendritic and sinuous planform shapes, steep and linear longitudinal profiles, and cross-sectional asymmetry and width. We also report breaks/changes in canyon longitudinal slope gradient, relief and slope-area regression models at the intersection with faults. Tectonic activity gives rise to two types of knickpoints in the Cook Strait Canyon. The first type consists of low slope gradient, rounded and diffusive knickpoints forming as a result of short wavelength folds or fault break outs and being restored to an equilibrium profile by upstream erosion and

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

    Tackley, P. J.; Xie, S.


    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. Tectonic activity evolution of the Scotia-Antarctic Plate boundary from mass transport deposit analysis (United States)

    Pérez, Lara F.; Bohoyo, Fernando; Hernández-Molina, F. Javier; Casas, David; Galindo-Zaldívar, Jesús; Ruano, Patricia; Maldonado, Andrés.


    The spatial distribution and temporal occurrence of mass transport deposits (MTDs) in the sedimentary infill of basins and submerged banks near the Scotia-Antarctic plate boundary allowed us to decode the evolution of the tectonic activity of the relevant structures in the region from the Oligocene to present day. The 1020 MTDs identified in the available data set of multichannel seismic reflection profiles in the region are subdivided according to the geographic and chronological distributions of these features. Their spatial distribution reveals a preferential location along the eastern margins of the eastern basins. This reflects local deformation due to the evolution of the Scotia-Antarctic transcurrent plate boundary and the impact of oceanic spreading along the East Scotia Ridge (ESR). The vertical distribution of the MTDs in the sedimentary record evidences intensified regional tectonic deformation from the middle Miocene to Quaternary. Intensified deformation started at about 15 Ma, when the ESR progressively replaces the West Scotia Ridge (WSR) as the main oceanic spreading center in the Scotia Sea. Coevally with the WSR demise at about 6.5 Ma, increased spreading rates of the ESR and numerous MTDs were formed. The high frequency of MTDs during the Pliocene, mainly along the western basins, is also related to greater tectonic activity due to uplift of the Shackleton Fracture Zone by tectonic inversion and extinction of the Antarctic-Phoenix Ridge and involved changes at late Pliocene. The presence of MTDs in the southern Scotia Sea basins is a relevant indicator of the interplay between sedimentary instability and regional tectonics.

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


    Zapata Henao, Sebastian


    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 influence of tectonic evolution on the accumulation and enrichment of coalbed methane (CBM)

    Institute of Scientific and Technical Information of China (English)

    SONG Yan; ZHAO Mengjun; LIU Shaobo; WANG Hongyan; CHEN Zhenhong


    The current accumulation and enrichment of CBM reservoir is a result of the preservation and destruction of former CBM, after the superposing evolution of reversingand-uplifting and the subsequent evolution within the coalbearing basin. The critical moment of the CBM reservoir formation is the time when the burying depth of the overlying net thickness amounts to the least in geological history after the gas generation of coal beds. Except the coal-bearing basins of lower metamorphism, most basins suffered the evolution stage of reversion and uplift. The formation of the CBM reservoir is controlled by the beginning and lasting time, and the intensity of reversing and uplifting. The tectonic evolution after reversing and uplifting also affects the accumulation of CBM in coal-bearing basin. The CBM constantly dissipates in the area of chronically uplifting and denudating. The area developed overlying sedimentation is advantageous to the preservation of CBM, but also can lead to the reduction of CBM saturation.

  19. 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


    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.

  20. Andean subduction orogeny: feedbacks between tectonics, relief evolution and global climate (United States)

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


    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

  1. Sill genesis in the Paleoproterozoic tectonic evolution of the Onega Trough, Baltic shield (United States)

    Poleshchuk, A. V.


    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.

  2. Evidence of Variscan and Alpine tectonics in the structural and thermochronological record of the central Serbo-Macedonian Massif (south-eastern Serbia) (United States)

    Antić, Milorad D.; Kounov, Alexandre; Trivić, Branislav; Spikings, Richard; Wetzel, Andreas


    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 this massif (south-eastern Serbia) consist of the medium- to high-grade Lower Complex and the low-grade Vlasina Unit. Outcrop- and micro-scale ductile structures in this area document three major stages of ductile deformation. The earliest stage D1 is related to isoclinal folding, commonly preserved as up to decimetre-scale quartz-feldspar rootless fold hinges. D2 is associated with general south-eastward tectonic transport and refolding of earlier structures into recumbent metre- to kilometre-scale tight to isoclinal folds. Stages D1 and D2 could not be temporally separated and probably took place in close sequence. The age of these two ductile deformation stages was constrained to the Variscan orogeny based on indirect geological evidence (i.e. ca. 408-ca. 328). During this period, the SMM was involved in a transpressional amalgamation of the western and eastern parts of the Galatian super-terrane and subsequent collision with Laurussia. Outcrop-scale evidence of the final stage D3 is limited to spaced and crenulation cleavage, which are probably related to formation of large-scale open upright folds as reported previously. 40Ar/39Ar thermochronology was applied on hornblende, muscovite, and biotite samples in order to constrain the age of tectonothermal events and activity along major shear zones. These 40Ar/39Ar data reveal three major cooling episodes affecting the central SMM. Cooling below greenschist facies conditions in the western part of the Vlasina Unit took place in a post-orogenic setting (extensional or transtensional) in the early Permian (284 ± 1 Ma). The age of activity along the top-to-the-west shear zone formed within the orthogneiss in the Božica area of the Vlasina Unit was constrained to Middle Triassic (246 ± 1 Ma). This

  3. Integrating Geochemical and Geodynamic Numerical Models of Mantle Evolution and Plate Tectonics (United States)

    Tackley, P. J.; Xie, S.


    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

  4. Timing and modes of granite magmatism in the core of the Alboran Domain, Rif chain, northern Morocco: Implications for the Alpine evolution of the western Mediterranean (United States)

    Rossetti, Federico; Theye, Thomas; Lucci, Federico; Bouybaouene, Mohamed L.; Dini, Andrea; Gerdes, Axel; Phillips, David; Cozzupoli, Domenico


    The Betic-Rif orogen forms the western termination of the Alpine orogenic system in the Mediterranean region. The precise timing, structural evolution, and distribution of high-grade metamorphic units (Alpine versus pre-Alpine) in the inner zones of the orogen (Alboran Domain) remain controversial issues. In this paper we report occurrence of distinct generations of peraluminous granitic bodies intruded within Beni Bousera peridotites and their amphibolite-to-granulite facies envelope, in the core of the Alboran Domain of the Rif chain (northern Morocco). These granitic bodies are central to the reconstruction of the high-grade evolution of the Alboran Domain because they provide first-order structural markers to assess the P-T-t deformation history of the high-grade terranes. Here we document the petrography and structural relationships with the host rocks and constrain the timing of granite emplacement using laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon and/or monazite dating, complemented by 40Ar/39Ar dating. The results indicate that granite emplacement occurred in two major episodes of anatectic magmatism, during the Hercynian (circa 300 Ma) and Alpine (circa 22 Ma) periods, respectively. These data (1) provide conclusive evidence for an important phase of Hercynian magmatism and high-grade metamorphism in the Alboran Domain and (2) permit a revaluation of the significance of the high-grade early Miocene event documented in the Alboran Domain in terms of a late stage, thermal pulse that reworked a polymetamorphic (Hercynian and Alpine) nappe pile. These results provide new constraints for construction of a feasible tectonometamorphic model for the Alpine evolution of the western Mediterranean.

  5. Hinterland tectonics and drainage evolution recorded by foreland basin archives: the Neogene Siwaliks of the Himalaya (United States)

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


    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

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

    Institute of Scientific and Technical Information of China (English)


    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.

  7. 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)

  8. The role of salt tectonics in the evolution of the northeastern Pyrenees (United States)

    Ford, Mary; Christophoul, Frédéric; Menzer, Lionel; Simonis, Jules; Saura, Eduard; Vergés, Jaume


    Evaporites can play a major role in controlling the architecture of external orogenic belts, both during extensional and subsequent compressional phases. However, salt can also 'hide' deformation due to its ability to flow and dissolve. The challenge is to recognise the imprint of its past presence and influence. In the NE Pyrenees multiple deformation phases have been identified based on locally anomalous stratigraphic and structural relationships. This has resulted in complex, sometimes incoherent and often conflictual models of orogenic history. For example, a pre-Cenomanian deformation phase has been interpreted as either extensional or compressional. As part of the ANR-PYRAMID project, we have re-examined key localities around the eastern Mouthoumet massif, in the Corbières foreland and along the Corbières thrust front to reconstruct a coherent deformation history involving salt tectonics. Keuper (Carnian - Rhetian) evaporitic deposits gave rise to diapirs and detachments that were particularly active during Early to Late Cretaceous extension and later during Late Cretaceous to Eocene compression. Growth unconformities and rapid thickness changes in the Aptian Quillan basin indicate that it developed as a salt controlled minibasin. Olistoliths, gypsum breccias and presence of bipyramidal quartz in Albian strata preserved as footwall imbricates along the North Pyrenean thrust front (e.g. around Cucugnan) attest to the proximity of a large diapiric body. Below the Cenomanian unconformity, rotated fault blocks of Liassic to Albian strata lie above a Keuper detachment. These extensional fault blocks have already been recognised at the Serre de Bouchard. They are also preserved north of Cucugnan, in the Montagne de Tauch and in the Fontfroide massif with little or no alpine inversion. In the Corbières foreland area salt-influenced extensional and compressional deformation generated growth folds, with completely overturned limbs (flaps), welds, growth

  9. Main Stages of Geodynamic Evolution of the Caucasian Segment of the Alpine-Mediterranean Belt (United States)

    Gamkrelidze, Irakli; Shengelia, David; Maisadze, Ferando; Tsutsunava, Tamara; Chichinadze, Giorgi


    Within the oceanic area of Tethys, with a typical oceanic crust, in geological past relatively small continental or subcontinental plates (terranes) were situated. The Greater Caucasian, Black Sea - Central Transcaucasian, Baiburt - Sevanian and Iran - Afghanian accretionary terranes, which in geological past represented island arcs or microcontinents, are identified in the Caucasian segment of the Alpine-Mediterranean belt. They are separated by ophiolite sutures (relics of small or large oceanic basins) of different age. During the Late Precambrian, Paleozoic and Early Mesozoic these terranes underwent horizontal displacement in different directions and ultimately they joined the Eurasian continent. New LA-ICP-MS U-Pb zircon dating along with available geologic, petrologic and geochemical investigations, allow to trace with confidence the main stages of regional metamorphism, granite formation and, consequently, pre-Alpine continental crust making within the Caucasus. At the pre-Grenville stage (1200 Ma and more) between the Baltica and Gondvana ancient continents, on the oceanic crust of Prototethys accumulation mainly of terrigenous sediments and of basic volcanites took place. At the Grenville stage (1000-800 Ma) subcontinental or primitive continental crust (gneiss-migmatite complex and synmetamorphic grenitoids of sodium series) were formed in suprasubduction conditions by both sides of Proto-Paleotethys and along the northern peripheries of comparatively small oceanic basins of the Arkhiz and Southern Slope of the Greater Caucasus. At the Baikalian stage (650-550 Ma) plagiogneissic complex has been cut by Precambrian gabbroids and intruded by large bodies of quartz-diorites. The next, Late Baikalian stage (540-500 Ma) is determined by the intrusion of Cambrian basites and Late Baikalian granitoids and by manifestation of intensive suprasubduction regional metamorphism. Late Baikalian tectogenesis is accompanied by contraction of the small oceanic basin of

  10. The Alpine evolution of Thessaly (NW Greece) and Late Tertiary Aegean kinematics

    NARCIS (Netherlands)

    Walcott, C.R.


    The Aegean region is one ofthe most studied regions currently undergoing post-orogenic extension. Numerous kinematic and dynamic models have been proposed to account for its active tectonics. Most recent studies have demonstrated that, since the onset ofextension in the early Miocene, there has been

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

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


    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.

  12. Structure and tectonic evolution of the Fuegian Andes (southernmost South America) in the framework of the Scotia Arc development (United States)

    Torres Carbonell, Pablo J.; Dimieri, Luis V.; Olivero, Eduardo B.; Bohoyo, Fernando; Galindo-Zaldívar, Jesús


    The major structural and tectonic features of the Fuegian Andes provide an outstanding onshore geological framework that aids in the understanding of the tectonic evolution of the Scotia Arc, mainly known from offshore studies. The orogenic history of the Fuegian Andes (Late Cretaceous-Miocene) is thus compared and integrated with the tectonic history of the Scotia Sea. Late Cretaceous-Paleocene structures in the Fuegian Andes suggest a N-directed contraction consistent with an oroclinal bending of the southernmost South America-Antarctic Peninsula continental bridge. This N-directed contraction in the Fuegian Andes continued during the spreading of the West Scotia Ridge, between 40-50 and 10 Ma ago. The onset of major strike-slip faulting in Tierra del Fuego is considered here to be not older than the late Miocene, consistent with the recent history of the North Scotia Ridge; thus forming part of a tectonic regime superposed to the prior contraction in the Fuegian Andes.

  13. Tectonic evolution of the Anadyr Basin, northeastern Eurasia, and its petroleum resource potential (United States)

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


    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

  14. Late Paleozoic-Mesozoic tectonic evolution of SW Japan: A review - Reappraisal of the accretionary orogeny and revalidation of the collisional model (United States)

    Charvet, Jacques


    This paper makes a review of the interpretations of the tectonic evolution of SW Japan during the last three decades. In the late 1970s, the dominant model was the so-called "Pacific-type orogeny", emphasizing the purported absence of nappes and the contrast with the alpine chains, and interpreting the evolution as due to a steady oceanic subduction since the Paleozoic time. In the 80s, the discovery of the actual structure made of a pile of large thrust sheets led authors to propose collisional models, involving the intermittent underthrusting of buoyant blocks like micro-continents. At the same time, the use of high-resolution biostratigraphy allowed several authors to recognize ancient accretionary wedges, with a reconstructed ocean plate stratigraphy of individual accreted units, especially in the Tanba and Shimanto zones. Also, precise radiometric dating permitted the distinction of metamorphosed units, especially in Sanbagawa and Shimanto belts. As a result of these new data, since the 1990s, the plate tectonic interpretation of the history of the Japanese Islands was revised by Japanese scientists and presented again in terms of accretionary processes linked to a steadily oceanic subduction, with an episodic ridge subduction: the so-called "Miyashiro-type orogeny". The review of different data leads to the following conclusions. The structure of SW Japan is made of a pile of sub-horizontal nappes, polydeformed, with a geometry similar to the one encountered in collisional orogens. The geodynamic mechanisms advocated for the tectonic building within the accretionary orogeny concept (Miyashiro-type orogeny) are inappropriate. A permanent oceanic subduction with the intermittent "collision" (actually subduction) of an active ridge or seamount chain is unable to build such structures, as this process induces in fact an acceleration of the tectonic erosion and collapse of the upper plate; the underthrusting of a micro-continent or mature arc is likely needed. The

  15. Seismic Interpretation of the Nam Con Son Basin and its Implication for the Tectonic Evolution

    Directory of Open Access Journals (Sweden)

    Nguyen Quang Tuan


    Full Text Available The Nam Con Son Basin covering an area of circa 110,000 km2 is characterized by complex tectonic settings of the basin which has not fully been understood. Multiple faults allowed favourable migration passageways for hydrocarbons to go in and out of traps. Despite a large amount of newly acquired seismic and well data there is no significant update on the tectonic evolution and history of the basin development. In this study, the vast amount of seismic and well data were integrated and reinterpreted to define the key structural events in the Nam Con Son Basin. The results show that the basin has undergone two extentional phases. The first N - S extensional phase terminated at around 30 M.a. forming E - W trending grabens which are complicated by multiple half grabens filled by Lower Oligocene sediments. These grabens were reactivated during the second NW - SE extension (Middle Miocene, that resulted from the progressive propagation of NE-SW listric fault from the middle part of the grabens to the margins, and the large scale building up of roll-over structure. Further to the SW, the faults of the second extentional phase turn to NNE-SSW and ultimately N - S in the SW edge of the basin. Most of the fault systems were inactive by Upper Miocene except for the N - S fault system which is still active until recent time.

  16. Tectonic Evolution of the Tianhuan Depression and the Western Margin of the Late Triassic Ordos

    Institute of Scientific and Technical Information of China (English)

    LI Xiangbo; LIU Huaqing; WANYAN Rong; WEI Lihua; LIAO Jianbo; FENG Ming; MA Yuhu; BAI Yunlai


    The Ordos Basin is one of the most important oil and gas basins in China. Based on surface outcrop, key exploratory wells and seismic reflection data and by using the technology of "prototype basin recovery", seismic profile "layer flattening" and "restoration of balanced section", and other methods, the sedimentary boundary, structure and the evolution history of the Tianhuan depression on the western margin of the Ordos Basin are reestablished. The following results have been obtained. (1) The west boundary of the Late Triassic Ordos Basin was far beyond the scope of the current basin. The basin is connected with the Late Triassic Hexi Corridor Basin, and its western margin did not have tectonic characteristics of a foreland basin. (2) The Tianhuan depression was first formed in the Late Jurassic. At the late stage it was impacted by the late Yanshanian and Himalayan tectonic movement and the depression axis gradually moved eastwards to the present location with a cumulative migration distance of ~30 kin. (3) Eastward migration of the depression axis caused adjustment and even destruction of the originally formed oil and gas reservoirs, so that oil and gas remigrated and aggregated, resulting in secondary structural reservoirs formed at high positions on the western flank of the depression.

  17. Tectonic and stratigraphic evolution of the Western Alboran Sea Basin in the last 25 Myrs (United States)

    Do Couto, Damien; Gorini, Christian; Jolivet, Laurent; Lebret, Noëmie; Augier, Romain; Gumiaux, Charles; d'Acremont, Elia; Ammar, Abdellah; Jabour, Haddou; Auxietre, Jean-Luc


    The Western Alboran Basin (WAB) formation has always been the subject of debate and considered either as a back-arc or a forearc basin. Stratigraphic analyses of high-resolution 2D seismic profiles mostly located offshore Morocco, enabled us to clarify the tectonic and stratigraphic history of the WAB. The thick pre-rift sequence located beneath the Miocene basin is interpreted as the topmost Malaguide/Ghomaride complex composing the Alboran domain. The structural position of this unit compared with the HP-LT exhumed Alpujarride/Sebtide metamorphic basement, leads us to link the Early Miocene subsidence of the basin with an extensional detachment. Above the Early Miocene, a thick Serravallian sequence marked by siliciclastic deposits is nearly devoid of extensional structures. Its overall landward to basinward onlap geometry indicates that the WAB has behaved as a sag basin during most of its evolution from the Serravallian to the late Tortonian. Tectonic reconstructions in map view and in cross section further suggest that the basin has always represented a strongly subsiding topographic low without internal deformation that migrated westward together with the retreating slab. We propose that the subsidence of the WAB was controlled by the pull of the dipping subducting lithosphere hence explaining the considerable thickness (10 km) of the mostly undeformed sedimentary infill.

  18. Tectonic evolution of the El Salvador Fault Zone. Insights from analogue experiments. (United States)

    Alonso-Henar, Jorge; Schreurs, Guido; Jesús Martínez-Díaz, José; Álvarez-Gómez, José Antonio


    The El Salvador Fault Zone (ESFZ) is an active, c. 150 km long and 20 km wide segmented, dextral strike-slip fault zone within the El Salvador Volcanic Arc striking N90°-100°E. Although several studies have investigated the surface expression of the ESFZ, little is known about its structure at depth and its kinematic evolution. Our analysis of structural field data, remote sensing images and morphometric indices reveals a trenchward migration of the volcanic arc and furthermore suggests that not all structures within the ESFZ can be explained within the current tectonic context, but require a phase of extension or an extensional component of deformation at some stage in the evolution of the ESFZ. Such an extension and trenchward migration of the volcanic arc could be related to subduction roll-back of the Cocos Plate beneath the Chortis Block in Mio-Pliocene times. Such a possible evolution leads to open questions that we address in our research: Is the ESFZ a neo-formed fault zone, i.e. did it form during one phase of strike-slip or transtensional deformation, or do the structures in the ESFZ reflect a two-phase evolution, i.e. an early phase of extension overprinted by a later phase of strike-slip or transtension? Did subduction roll-back occur beneath El Salvador? We carried out analogue model experiments to test whether or not an early phase of extension is required to form the present-day fault pattern in the ESFZ. Analogue modeling is an effective tool in testing various hypotheses, as it allows the experimenter to control specific parameters and to test their influence on the resulting structures. Our experiments suggest that a two-phase tectonic evolution best explains the ESFZ: an early pure extensional phase linked to a segmented volcanic arc is necessary to form the main structures of the ESFZ and can explain the shallow geometry of the fault zone. This extensional phase is followed by a strike-slip dominated regime, which results in inter

  19. Neogene marine isotopic evolution and the erosion of Lesser Himalayan strata: Implications for Cenozoic tectonic history (United States)

    Myrow, Paul M.; Hughes, Nigel C.; Derry, Louis A.; Ryan McKenzie, N.; Jiang, Ganqing; Webb, A. Alexander G.; Banerjee, Dhiraj M.; Paulsen, Timothy S.; Singh, Birendra P.


    An extensive, northward deepening blanket of Neoproterozoic and Cambrian sedimentary rocks once extended from the Himalayan margin far onto the Indian craton. Cambrian deposits of this "upper Lesser Himalayan" succession, which include deposits of the "outer" Lesser Himalaya tectonic unit, are enriched in radiogenic 187Os. They make up part of a proximal marine facies belt that extends onto the craton and along strike from India to Pakistan. By contrast, age-equivalent facies in the Tethyan Himalaya are more distal in nature. Neoproterozoic to Cambrian strata of the upper Lesser Himalayan succession are now missing in much of the Lesser Himalaya, with their erosion exposing older Precambrian Lesser Himalayan strata. We suggest that exhumation and weathering of the upper Lesser Himalaya and related strata caused dramatic changes in the 187Os/188Os and 87Sr/86Sr Neogene record of seawater starting at ∼ 16 Ma. First-order estimates for the volume of upper Himalayan strata, as well as the volume of all LH rock eroded since this time, and geochemical box modeling, support this idea. Exhumation at 16 Ma is a fundamental event in the evolution of the Himalayan orogeny and the geochemical evolution of the oceans, and will be a critical part of the construction of future models of Himalayan thrust belt evolution.

  20. Origin and Evolution of Limestone Caves of Chhattisgarh and Orissa, India: Role of Geomorphic, Tectonic and Hydrological Processes (United States)

    Gautam, P. K.; Allu, N. C.; Ramesh, R.; Yadava, M. G.; Panigrahi, C. P.


    Carbonate rocks undergo karstic process and karst morphology is a key to understand the nature and genesis of caves. The primary energy source for the formation of karst landforms is hydrological cycle. Geomorphic features along with hydrological characteristics provide important information not only on karst formation but also climate and environmental conditions. In this paper, we present the tectonic and geomorphic features that played a role in evolution of caves located in Chhattisgarh and Orissa States of India. The geomorphic and tectonic aspects of Kotumsar, Kailash, and Gupteshwar caves are discussed in relation to the origin and evolution of these caves. Caves are located near the water falls. The area is folded and faulted along the Eastern Ghat Mobile Belt (EGMB) due to tectonic reactivation. Shaly-limestone beds exhibit vertical dipping near Gupteshwar cave, and steeply inclined near Kotumsar and Kailash caves. Indrāvati and Sabari/Kolab tributaries of the Godavari River drain the area. The landscape evolution and the origin of caves in the region is a multistage process, where the lithology, orogeny, fluvial action, and monsoon are the main agents, which is similar to the four state model (Ford and Ewers, 1978). The river basin evolution and regional tectonism also caused the initiation of karstification in the region. The evolution of caves is believed to have taken place in Pre-Pliocene under more humid conditions that coincided with the initiation of monsoon in India. Further, during the Quaternary wet-dry/cold-warm phases altered physical and chemical weathering of limestone rocks. Contrasting relief features of Bastar plateau have also helped the extensive cave formation in the region. The dissolution along weak planes initiated the openings of caves, further enlarged by geomorphic agents. Both monsoon and tectonics have caused fluctuations in water levels along river courses, which acted as active agents in evolution of caves.

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

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


    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


    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 (United States)

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


    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. Tectonic Evolution of the Cretaceous Sava-Klepa Massif, Former Yugoslav Republic of Macedonia, based on field observations and microstructural analysis - Towards a new geodynamic Model (United States)

    Altmeyer, Tobias; Peternell, Mark; Prelević, Dejan; Köpping, Jonas


    the deformation history, i.e. the switch from compressive to extensional, rift forming, regime. REFERENCES Ferrill, D.A. et al. (2004). Calcite twin morphology: a low-temperature deformation geothermometer. Journal of Structural Geology 26: 1521-1529. Peternell, M. et al. (2010). Evaluating quartz crystallographic preferred orientations and the role of deformation partitioning using EBSD and fabric analyser techniques. Journal of Structural Geology 32: 803-817. Robertson, A.H.F. & Karamata, S. (1994). The role of subduction-accretion processes in the tectonic evolution of the Mesozoic Tethys in Serbia. Tectonophysics, 234:73-94. Schmid, S.M. et al. (2008). The Alpine-Carpathian-Dinaridic orogenic system: correlation and evolution of tectonic units. Swiss Journal of Geoscience, 101:139-183.

  5. Hydrological modelling of alpine headwaters using centurial glacier evolution, snow and long-term discharge dynamics (United States)

    Kohn, Irene; Vis, Marc; Freudiger, Daphné; Seibert, Jan; Weiler, Markus; Stahl, Kerstin


    The response of alpine streamflows to long-term climate variations is highly relevant for the supply of water to adjacent lowlands. A key challenge in modelling high-elevation catchments is the complexity and spatial variability of processes, whereas data availability is rather often poor, restricting options for model calibration and validation. Glaciers represent a long-term storage component that changes over long time-scales and thus introduces additional calibration parameters into the modelling challenge. The presented study aimed to model daily streamflow as well as the contributions of ice and snow melt for all 49 of the River Rhine's glaciated headwater catchments over the long time-period from 1901 to 2006. To constrain the models we used multiple data sources and developed an adapted modelling framework based on an extended version of the HBV model that also includes a time-variable glacier change model and a conceptual representation of snow redistribution. In this study constraints were applied in several ways. A water balance approach was applied to correct precipitation input in order to avoid calibration of precipitation; glacier area change from maps and satellite products and information on snow depth and snow covered area were used for the calibration of each catchment model; and finally, specific seasonal and dynamic aspects of discharge were used for calibration. Additional data like glacier mass balances were used to evaluate the model in selected catchments. The modelling experiment showed that the long-term development of the coupled glacier and streamflow change was particularly important to constrain the model through an objective function incorporating three benchmarks of glacier retreat during the 20th Century. Modelling using only streamflow as calibration criteria had resulted in disproportionate under and over estimation of glacier retreat, even though the simulated and observed streamflow agreed well. Also, even short discharge time

  6. Diagenetic Evolution and Reservoir Quality of Sandstones in the North Alpine Foreland Basin: A Microscale Approach. (United States)

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


    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

  7. Alpine endemic spiders shed light on the origin and evolution of subterranean species. (United States)

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


    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

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

    Directory of Open Access Journals (Sweden)

    Casazza Gabriele


    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.

  9. In-situ measurement of the temporal evolution of the thermal conductivity of alpine snow layers (United States)

    Morin, S.; Domine, F.; Arnaud, L.; Picard, G.; Jacobi, H.; Willemet, J.


    We report on a 3-months long time series of in-situ measurements of the thermal conductivity (kT) of snow in 6 different layers in an alpine snowpack in the Mont-Blanc moutain range, France, at an altitude of 2400 m. Automatic measurements were carried out every two days using the heated-needle probe technique. Results show consistent patterns of thermal conductivity increase throughout the measurements campaign. The temporal rate of change of kTvaries up to 0.01 W m-1 K-1 dy-1, with maximum values just after snowfall. Temporal rates of kTincrease are compared with results from laboratory experiments under controlled conditions and with published theoretical assessments. A case where kT decreased over time in a given snow layer was documented both in the field and in the laboratory. Possible reasons for such a behaviour are discussed. A cursory comparison of the field measured kTvalues with the prediction of the snowpack model CROCUS shows that at first order the model performs satisfactorily. However, a quantitative understanding and modeling of the variations of kT over time would require an in-depth assessment of physical processes occurring during snow metamorphism.

  10. The Pattern and Evolution of the Permian Palaeobiogeography and Tectonic Palaeogeography in Jilin and Heilongjiang Orogenic Belt

    Institute of Scientific and Technical Information of China (English)

    Peng Xiangdong; Li Xiaomin; Liu Pengju


    The orogenic belt locates between the North China plate and Siberia plate. The Permian palaeobiogeography and tectonic palaeogeography changed quickly and clearly. The line from Changchun to Yanji is an important palaeobiogeographic provincing line, which may be the collission suture belt of the North China plate and north middle massifs. The orogenic belt has been divided into 2 regions: the North middle massif region and the North Margin of North China plate, the pattern and evolution of Permian palaeobiogeography in the present area were discussed and the Permian biota mixture and its significants were analysed. Then, Based on the above, the Permian tectonic palaeogeography of the orogenic belt is reconstructed.

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

    Institute of Scientific and Technical Information of China (English)


    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. Thermochronology and tectonics of the Leeward Antilles: Evolution of the southern Caribbean Plate boundary zone (United States)

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


    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.

  13. Tectonic evolution of the gulf of Aqaba-Dead Sea transform fault system (United States)

    Barjous, M.; Mikbel, Sh


    Neogene tectonic phases related to stresses which created the Gulf of Aqaba-Dead Sea transform fault system were recorded from evidence in the central part of the Wadi Araba. The chronological sequence of deformation stages is as follows: (1) Epeirogeny (latest late Eocene-Oligocene). (2) Faulting and warping (?Oligocene-Middle Miocene). (3) Folding striking between north-northeast and northeast, E-W trending and N-S shear faulting, and NW-SE normal faulting (Miocene). (4) Uplift and faulting (Pliocene-Pleistocene). (5) Faulting with volcanic activity (Pleistocene). (6) Sinistral movement along the major shear fault in the Wadi Araba. Indications are that this phase is still active (Pleistocene-Recent). The re-strain phases recognised are clues for the investigated area and the entire region to the understanding of the tectonic evolution of the Gulf of Aqaba-Dead Sea transform. Structural features contributing to evidence of strike-slip movement are: drag folds, reverse and normal flower structures, alternation of the downthrown side along the fault trace, gently waved vertical fault planes, horizontal slickensides, transpressive and transtensional pressure ridges and rhombs, linear fault traces without marked vertical throw, and fault plane ridges. A sinistral offset of 40 km along the N-S Al Quweira Fault was deduced from the displacement of distinctive andesitic rocks found on both sides of the fault. For the E-W Salawan Fault, a dextral movement of at least 7 km was determined from the offset of formation boundaries. North-northeast-striking deformed belts containing monoclinal to recumbent en-echelon folds can be seen in the Gulf of Aqaba-Dead Sea transform fault zone. The axial planes of the folds dip southeast and face northwest. These structural elements indicate local SE-NW compressional stress.

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

    Institute of Scientific and Technical Information of China (English)


    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

  15. The late Mesozoic-Cenozoic tectonic evolution of the South China Sea: A petrologic perspective (United States)

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


    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.

  16. Genome evolution in alpine oat-like grasses through homoploid hybridization and polyploidy (United States)

    Winterfeld, Grit; Wölk, Alexandra; Röser, Martin


    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

  17. Genome evolution in alpine oat-like grasses through homoploid hybridization and polyploidy. (United States)

    Winterfeld, Grit; Wölk, Alexandra; Röser, Martin


    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.

  18. Genome evolution in alpine oat-like grasses through homoploid hybridization and polyploidy. (United States)

    Winterfeld, Grit; Wölk, Alexandra; Röser, Martin


    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

  19. Origin, mobility, and temporal evolution of arsenic from a low-contamination catchment in Alpine crystalline rocks. (United States)

    Pili, Eric; Tisserand, Delphine; Bureau, Sarah


    The reduction to 10 μg/l of the limit for arsenic in drinking water led many resource managers to deal with expensive treatments. In the very common case of arsenic levels close to the recommended maximum concentration, knowing the origin and temporal evolution of As has become of great importance. Here we present a case study from an alpine basin. Arsenic speciation, isotopic compositions of pyrite, sulfate and water, and concentrations of major and trace elements demonstrate a geogenic source for arsenic linked to the dissolution of pyrite. We provide new tools to further study As at low concentrations where many processes may be masked. The observed negative correlation between δ(34)SSO4 and [As] is interpreted as a Rayleigh-type sulfur-isotope fractionation during increasing pyrite dissolution. The observed positive correlation between δ(18)OSO4 and As(V)/As(III) could help to retrieve initial redox conditions. A 3-year long monitoring at high-resolution demonstrated that drought conditions enhance pyrite dissolution whose degradation products are scavenged by recharge water. An increase in As in groundwater may result from droughts due to enhanced oxygen entry in the unsaturated zone. The 2003 European heatwave had a major effect.

  20. 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)

  1. Tracing long term tectonic evolution of accretionary orogens by U-Pb zircon geochronology: Proterozoic to Jurassic tectonics of the Santander Massif, northern Colombia (United States)

    Valencia, V. A.; Cardona, A.; Gehrels, G. E.; Ruiz, J.; Ibañez, M.


    Accurate orogenic models are nedded to reconstruct complex tectonic histories of long lived convergent margins. Integrated zircon U-Pb geochronology on igneous, sedimentary and metasedimentry rocks within single crustal domains is a powerful tool, as it can be used to trace the timing of rock forming events, magmatic style and episodity, and identify crustal recycling. U-Pb detrital zircon and magmatic geochronology was carried on multiple litostratigraphic units of the Santander Massif in the northeastern Andes, in order to reconstruct its long term Late Proterozoic to Early Mesozoic tectonic evolution. Major zircon forming events includ well defined Grenvillian, Late Neoproterozoic to Ordovician, Silurian, Early Permian and Jurassic events. Major peaks of activity at ca. 197 Ma, 440-410 Ma and 470-490 Ma and 950-1052 Ma, support the existence of continental scale tectonic cycles. Older Mesoproterozoic (1.3-1.5 Ga) crustal input in metasediments and magmatic rocks link these units to crustal recycling on the margins of the Amazon Craton, whereas the older 950-1052 Ma peak indicates the link of this crustal segment with other Andean Grenvillian remnant. Previous interpretations of the Paleozoic Silgara Formation seem incorrect, as acquired dates from this study includ different metamorphic units, deposited and formed after the Silurian and Permian during final stages of Pangea's assemblage, probably as Laurentia migrated to its final Alleghanian position. Finally the presence of the NW South America Jurassic arc is also present in the region by granitoid ages. The limited input of this arc signature within the contemporaneous and overlapping Early Cretaceous sedimentary rocks suggest that this arc was developed in a back arc setting.

  2. Periodic Vesicle Formation in Tectonic Fault Zones—an Ideal Scenario for Molecular Evolution (United States)

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


    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.

  3. Neogene sedimentary evolution of Baja California in relation to regional tectonics (United States)

    Helenes, J.; Carreño, A. L.


    During the Neogene, the tectonic and sedimentary evolution of the Baja California Peninsula followed four stages: (1) during the early Miocene (22 Ma), the initiation of transform motion between Pacific and North American plates, caused a rapid subsidence in the Continental Borderland Province and in some adjacent areas.This subsidence coincided in time with with a global rise in sea level. At this time, the eastern and southern parts of the peninsula did not show any evidence of subsidence. (2) During the middle Miocene (12 Ma), normal and strike slip faulting migrated eastward, causing subsidence in the northern part of the Gulf of California, where the oldest Tertiary marine sedimentary rocks were deposited. The areas in central Baja California Sur and the central part of the Gulf itself received abundant volcanic deposits related to continental extension. (3) During the late Miocene (8 Ma), the western margin of the Peninsula changed to a slightly compressive regime, while the northern part of the Gulf contained a marine basin with upper bathyal environments. The central area of the Gulf continued receiving abundant volcanic deposits, while the Los Cabos block received marine sedimentation, correlatable with sedimentary units reported from the continental margins in Nayarit, Jalisco and Michoacán. (4) Beginning in the early Pliocene (5 Ma), the present configuration of the Gulf of California developed through right-lateral strike slip and extension in the Gulf itself. Since Pliocene times, the Gulf presents widespread marine sedimentation with deep basins reaching lower bathyal depths.

  4. Geochemistry of Mesoproterozoic Volcanic Rocks in the Western Kunlun Mountains:Evidence for Plate Tectonic Evolution

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chuanlin; DONG Yongguan; ZHAO Yu; WANG Aiguo; GUO Kunyi


    Mesoproterozoic volcanic rocks occurring in the north of the western Kunlun Mountains can be divided into two groups. The first group (north belt) is an reversely-evolved bimodal series. Petrochemistry shows that the alkalinity of the rocks decreases from early to late: alkaline→calc-alkaline→tholeiite, and geochemistry proves that the volcanic rocks were formed in rifting tectonic systems. The sedimentary facies shows characteristics of back-arc basins. The second (south belt) group, which occurs to the south of Yutian-Minfeng-Cele, is composed of calc-alkaline island arc (basaltic) andesite and minor rhyolite. The space distribution, age and geochemistry of the two volcanite groups indicate that they were formed in a back-arc basin (the first group) and an island arc (the second group) respectively and indicate the plate evolution during the Mesoproterozoic. The orogeny took place at ~1.05 Ga, which was coeval with the Grenville orogeny. This study has provided important geological data for exploring the position of the Paleo-Tarim plate in the Rodinia super-continent.

  5. The deformation and tectonic evolution of the Huahui Basin, northeast China, during the Cretaceous-Early Cenozoic (United States)

    Huang, Shiqi; Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Huang, Dezhi; Wei, Shi; Li, Zhenhong; Miao, Laicheng; Zhu, Mingshuai


    The Cretaceous Huahui basin lies along the Dunhua-Mishan fault (Dun-Mi fault), which is one of the northern branches of Tan-Lu fault in northeastern China. The study of the formation and the tectonic movements that took place in the basin can provide very important information for deciphering the tectonic evolution of northeastern China during Cretaceous-Early Cenozoic. The field analysis of fault-slip data collected from different units in the basin, demonstrates changes in the paleo-stress state that reveals a three-stage tectonic movement during the Cretaceous-Early Cenozoic. The earliest tectonic movement was NW-SE extension, which was responsible for the formation of the basin and sedimentary infilling during the Early Cretaceous. Dating of the andesite in the fill indicates it began during about 119.17 ± 0.80 Ma. The extensional structures formed in the Latest Early Cretaceous imply that this tectonic movement lasted until the beginning of the Late Cretaceous. The second stage began during the Late Cretaceous when the tectonic stress state changed and was dominated by NW-SE compression and NE-SW extension, which caused the inversion of the extensional basin. This compression folded the Early Cretaceous deposits and reactivated pre-existing faults and uplifted pre-existing granite in the basin. The strata and the unconformity in the basin shows that this compressive phase probably took place during the Late Cretaceous and ended in the Early Paleogene by a compressional regime with NE-SW compression and NW-SE extension that constitutes the third stage. The tectonic stress fields documented in the Huahui basin provide insight into the influences of plate tectonics on the crustal evolution of northeastern China during the Cretaceous to Early Cenozoic. These results show that the development of Huahui basin was controlled by the northwestward subduction of the paleo-Pacific plate during the Cretaceous, and later by the far-field effects of India-Asia collision in

  6. Tectonic evolution of the Changling fault basin and its relationship to oil and gas accumulation

    Institute of Scientific and Technical Information of China (English)

    Wang Jianqiang; Yang Guang; Xue Linfu; Zhang Jianwei; Bai Ye; Li Wenbo


    The Changling fault depression passed through three stages of evolution:a period of faulting,a period of subsidence,and an inversion period.The fault lifted the whole area and the formation was eroded during the late Yingcheng formation,the late Nenjiang formation,and the late Mingshui formation.The denudation quantity of eight wells located in the study area is estimated by the interval transit time method and by the formation trend extension method using seismic and drilling data.Inversion back stripping technology with de-compaction correction was used to restore the original sedimentary thickness step by step and to recover the burial history at a single well.Two profiles were selected for the recovery and study of the tectonic evolution.The study confirmed that the primary major gas bearing structure formed due to thermal shrinkage lifting during the late Yingcheng formation.Successive development in a pattern during the late Mingshui formation led to the formation of the primary gas pool.Vertical differential uplift during the late Nenjiang formation formed the Fulongquan structure during the late Paleogene.At this same time a secondary gas pool formed.A large scale reverse developed late in the Mingshui formation that provided the impetus for formation of a secondary gas pool.It is thought that the migration and accumulation of oil and gas was controlled by lithologic character,fracture,and structure.The local uplift in the vicinity of the hydrocarbon recession is most conducive to the collection of hydrocarbon gas.

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

    Institute of Scientific and Technical Information of China (English)

    吴冲龙; 汪新庆; 刘刚; 李绍虎; 毛小平; 李星


    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

  8. The role of tectonics and climate in the late Quaternary evolution of a northern Amazonian River (United States)

    Cremon, Édipo Henrique; Rossetti, Dilce de Fátima; Sawakuchi, André de Oliveira; Cohen, Marcelo Cancela Lisboa


    The Amazon basin has most of the largest rivers of the world. However, works focusing the geological evolution of the trunk river or its tributaries have been only partly approached. The Branco River constitutes one of the main northern Amazonian tributaries. A previous work proposed that, before flowing southward into the Negro-Amazon Rivers, the Branco River had a southwest to northeast course into the Caribbean Sea. The present work aimed to establish if the proposed change in the course of this river is supported by morphological and sedimentological data. Other goals were to discuss the factors influencing river development and establish its evolution over time within the chronological framework provided by radiocarbon and optically stimulated luminescence dating. The work considered the entire course of the Branco River downstream of the Precambrian Guiana Shield, where the river presumably did not exist in ancient times. The river valley is incised into fluvial sedimentary units displaying ages between 100 and 250 ky old, which record active and abandoned channels, crevasse splay/levees, and point bars. The sedimentary deposits in the valley include two alluvial plain units as old as 18.7 ky and which intersects a Late Pleistocene residual megafan. These characteristics suggest that a long segment of the Branco River was established only a few thousand years ago. Together with several structural anomalies, these data are consistent with a mega-capture at the middle reach of this river due to tectonic reactivation in the Late Pleistocene. This integrated approach can be applied to other Amazonian tributaries to unravel how and when the Amazonian drainage basin became established.

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


    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

  10. Tectonics and sedimentary evolution of the Sandino forearc basin off Nicaragua, Central America (United States)

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


    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.

  11. Provenance Constraints on the Mesozoic-Cenozoic Tectonic Evolution of the Queen Charlotte Islands Region (United States)

    Mahoney, J.; Haggart, J. W.; Kimbrough, D.; Grove, M.


    The medial Cretaceous magmatic arc system of western North America was flanked by a series of forearc basins extending from Mexico to Alaska. Cretaceous strata in the Queen Charlotte Islands of northwest British Columbia are unique in this series of basins, as these strata have been displaced from the arc system by formation of the extensional Queen Charlotte basin in Cenozoic time. This displacement complicates reconstruction of the forearc basin, and makes it difficult to evaluate the controls on basin evolution. Sedimentologic, paleontologic, and detrital zircon analyses of forearc strata represented by the Valanginian- Campanian Queen Charlotte Group (QCG) constrain basin evolution and provide a framework for an interpretation of the Mesozoic-Cenozoic tectonic evolution of the Queen Charlotte Islands region. Basin subsidence initiated in Valanginian time with a marine transgression over irregular topography consisting of extensional fault blocks of pre-Cretaceous strata. Locally derived conglomerates at the base of the Longarm Formation are overlain by shallow marine shelf deposits that represent a westward-deepening, fining-upward transgressive succession with an eastern depositional edge that migrated eastward during Valanginian to Aptian time. West-directed paleocurrents and a unimodal detrital zircon population of 120-175 Ma grains provide the first linkage between the Cretaceous QCG and unroofed Jura-Cretaceous plutons of the Coast Plutonic Complex to the east. This initial transgressive sequence is superseded by a second pulse of clastic detritus in early Albian time, characterized by an easterly-derived, fossiliferous shallow-shelf sandstone (Haida Formation), fine-grained, outer shelf to upper slope strata (Bearskin Bay Formation), and mass-sediment gravity flows (Skidegate Formation). The unimodal zircon population (ca 140-175 Ma) in the lower Haida Formation is interpreted to reflect renewed uplift of Jura-Cretaceous arc plutons by contractional

  12. 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.)

  13. Determination of the tectonic evolution from fractures, faults, and calcite twins on the southwestern margin of the Indochina Block (United States)

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


    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.

  14. 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)


    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.

  15. Geomorphic evolution of Dehra Dun, NW Himalaya: Tectonics and climatic coupling (United States)

    Sinha, Swati; Sinha, Rajiv


    The Dehra Dun is a good example of a piggyback basin formed from the growth of the Siwalik hills. Two large rivers, the Ganga and the Yamuna, and their tributaries deposit a significant part of their sediment load in the Dun before they enter the Gangetic plains. This work documents the geomorphic complexities and landform evolution of the Dehra Dun through geomorphic mapping and chronostratigraphic investigation of the incised fan sections. Lesser Himalayan hills, inner and outer dissected hills, isolated hills, proximal fan, distal fan, dip slope unit, floodplains, and terraces are the major geomorphic units identified in the area. Isolated hills of fan material (IHF), proximal fan (PF), and distal fan (DF) are identified as fan surfaces from north to south of the valley. The OSL based chronology of the fan sediments suggests that the IHF is the oldest fan consisting of debris flow deposits with a maximum age of ~ 43 ka coinciding with the precipitation minima. The proximal fan consisting of sheet flow deposits represents the second phase of aggradation between 34 and 21 ka caused by shifting of deposition locus downstream triggered by high sediment supply that exceeded the transport capacity. The distal fan was formed by braided river deposits during 20-11 ka coinciding with the deglacial period. The IHF, PF and DF surfaces were abandoned by distinct incision phases during ~ 40-35, ~ 20-17, and ~ 11-4 ka respectively. A minor phase of terrace deposition in Dehra Dun was documented during 3-2 ka. Our results thus show that the evolutionary history of the alluvial fans in Dehra Dun was primarily controlled by climatic forcing with tectonics playing a minimum role in terms of providing accommodation space and sediment production.

  16. The Alegre Lineament and its role over the tectonic evolution of the Campos Basin and adjacent continental margin, Southeastern Brazil (United States)

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


    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.

  17. Rift architecture and evolution: The Sirt Basin, Libya: The influence of basement fabrics and oblique tectonics (United States)

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


    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.

  18. Metamorphic and tectonic evolution of the Greater Himalayan Crystalline Complex in Nyalam region, south Tibet (United States)

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


    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

  19. Quantifying Tectonic Controls on Regional Cenozoic Surface Evolution in the Eastern Lhasa Block (United States)

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


    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.

  20. 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


    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.

  1. Tectonic evolution of Tarim basin in Cambrian-Ordovician and its implication for reservoir development, NW China (United States)

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


    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.

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

    Directory of Open Access Journals (Sweden)

    Kaulina T.V.


    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

  3. Cenozoic Subsidence Features of Beitang Sag and Relationship with Tectonic Evolution

    Institute of Scientific and Technical Information of China (English)

    Zhang Tingting; Wang Hua; Yue Yong; Huang Chuanyan; Zhang Liwei


    Based on the application of the EBM basin modeling software and 2-D seismic profiles, the Paleogene and Neogene shubsidence histories of the Beitang(北塘) sag are simulated with the backstripping technique,and the relationship between subsidence character and tectonic revolution is discussed.Moreover,the result of the basin modeling reveals that the subsidence history of the Beitang sag has the characteristics of several geological periods,and these succeeding periods have shown certain inheritance and difference characteristics.At the early (Es3) and middle (Es2-Es1) rifting periods,the subsidence reaction of the Beitang sag was mainly in the charge of tectonic activity,while at the late (Ng-Nm+Q) rifting period-post rifting period and post rifting subsidence-acceleration period-the subsidence type is mainly that of thermal subsidence or regional depression effect; from the beginning of the subsidence history to the end,the reason for the basin subsidence has changed from tectonic activity to non-tectonic activity.

  4. Tectonic Evolution of an Early Precambrian High-Pressure Granulite Belt in the North China Craton

    Institute of Scientific and Technical Information of China (English)


    A large-scale high-pressure granulite belt (HPGB), more than 700 km long, is recognized within the metamorphic basement of the North China craton. In the regional tectonic framework, the Hengshan-Chengde HPGB is located in the central collision belt between the western block and eastern block, and represents the deep crustal structural level. The typical high-pressure granulite (HPG) outcrops are distributed in the Hengshan and Chengde areas. HPGs commonly occur as mafic xenoliths within ductile shear zones, and underwent multipile deformations. To the south, the Hengshan-Chengde HPGB is juxtaposed with the Wutai greenstone belt by several strike-slip shear zones. Preliminary isotopic age dating indicates that HPGs from North China were mainly generated at the end of the Neoarchaean, assocaited with tectonic assembly of the western and esatern blocks.

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

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


    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

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


    Hurst, Martin David


    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...

  7. Plate-tectonic evolution of the western U.S.A. (United States)

    Hamilton, W.


    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.

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


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


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


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


    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...

  10. Changes in the manner of tectonic movements under the Earth's evolution (United States)

    Kuzmin, M. I.; Yarmolyuk, V. V.


    Variations in the O, Sr, Nd, and Hf isotopic compositions in rocks of various ages, minerals, and mantle temperature in the geological history are considered. Two periods in the Earth's history are studied: the beginning of the formation of the planet until the turn of (3.4) 2.7-2.5 Ga and the tectonic movement period in the last 2 Ga, and also the transitional period within 2.7-2.0 Ga.

  11. Polyphase tectonic evolution of the Aksu Basin, Isparta Angle (Southern Turkey) (United States)

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


    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.

  12. Large Sanjiang basin groups outside of the Songliao Basin Meso-Senozoic Tectonic-sediment evolution and hydrocarbon accumulation (United States)

    Zheng, M.; Wu, X.


    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

  13. 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


    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.

  14. Grenville tectonic events and evolution of the Yenisei Ridge at the western margin of the Siberian Craton (United States)

    Likhanov, I. I.; Nozhkin, A. D.; Reverdatto, V. V.; Kozlov, P. S.


    Geological, petrologic, geochemical, and isotopic geochronological evidence for Grenville events at the western margin of the Siberian Craton are considered. These events were related to assembly of the Rodinia supercontinent. Multiple manifestations of riftogenic and within-plate magmatism at the final stage of orogenic evolution gave rise to breakdown of Rodinia and the formation of the Paleoasian ocean. The results allowed us to develop a new concept on the Precambrian geological evolution of the Yenisei Ridge and the processes that created its tectonic structure. The chronological sequence of events in the history of the Transangarian Yenisei Ridge is based on geological evidence and isotopic dating of Precambrian complexes variable in geodynamic nature. Four tectonic stages dated at 1.4-1.1, 1.1-0.9, 0.90-0.85, and 0.8-0.6 Ga were controlled by collision and extension recognized from large regional linear crustal structural elements. The evolution of the Transangarian Yenisei Ridge, which lasted for ˜650 Ma, corresponds in duration to supercontinental cycles that begin from rifting and breakdown of the predated supercontinent and was completed by orogeny and the formation of a new supercontinent. The regional geodynamic history correlates with the synchronous sequence and similar style of tectonothermal events at the periphery of the large Precambrian Laurentia and Baltica cratons. This is evidenced by paleocontinental reconstructions, which confirm close spatiotemporal links of Siberia with cratons in the northern Atlantic 1400-600 Ma ago and indicate incorporation of the Siberian Craton into the ancient Nuna and Rodinia supercontinents.

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

  16. 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.


    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.

  17. Seismo-stratigraphic evolution of the northern Austral Basin and its possible relation to the Andean tectonics, onshore Argentina. (United States)

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


    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

  18. Laurentian origin for the North Slope of Alaska: Implications for the tectonic evolution of the Arctic (United States)

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


    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. Stratigraphic assessment of the Arcelia Teloloapan area, southern Mexico: implications for southern Mexico's post-Neocomian tectonic evolution (United States)

    Cabral-Cano, E.; Lang, H. R.; Harrison, C. G. A.


    Stratigraphic assessment of the "Tierra Caliente Metamorphic Complex" (TCMC) between Arcelia and Teloloapan in southern Mexico, based on photo interpretation of Landsat Thematic Mapper images and field mapping at the 1:100,000 scale, tests different tectonic evolution scenarios that bear directly on the evolution of the southern North American plate margin. The regional geology, emphasizing the stratigraphy of a portion of the TCMC within the area between Arcelia and Teloloapan is presented. Stratigraphic relationships with units in adjacent areas are also described. The base of the stratigraphic section is a chlorite grade metamorphic sequence that includes the Taxco Schist, the Roca Verde Taxco Viejo Formation, and the Almoloya Phyllite Formation. These metamorphic units, as thick as 2.7 km, are covered disconformably by a sedimentary sequence, 2.9 km thick, composed of the Cretaceous marine Pochote, Morelos, and Mexcala Formations, as well as undifferentiated Tertiary continental red beds and volcanic rocks. The geology may be explained as the evolution of Mesozoic volcanic and sedimentary environments developed upon attenuated continental crust. Our results do not support accretion of the Guerrero terrane during Laramide (Late Cretaceous-Paleogene) time.

  20. Post-Pan-African tectonic evolution of South Malawi in relation to the Karroo and recent East African rift systems (United States)

    Castaing, C.


    Structural studies conducted in the Lengwe and Mwabvi Karroo basins and in the basement in South Malawi, using regional maps and published data extended to cover Southeast Africa, serve to propose a series of geodynamic reconstructions which reveal the persistence of an extensional tectonic regime, the minimum stress σ3 of which has varied through time. The period of Karroo rifting and the tholeiitic and alkaline magmatism which terminated it, were controlled by NW-SE extension, which resulted in the creation of roughly NE-SW troughs articulated by the Tanganyika-Malawi and Zambesi pre-transform systems. These were NW-SE sinistral-slip systems with directions of movement dipping slightly to the Southeast, which enabled the Mwanza fault to play an important role in the evolution of the Karroo basins of the Shire Valley. The Cretaceous was a transition period between the Karroo rifting and the formation of the Recent East African Rift System. Extension was NE-SW, with some evidence for a local compressional episode in the Lengwe basin. Beginning in the Cenozoic, the extension once more became NW-SE and controlled the evolution in transtension of the Recent East African Rift System. This history highlights the major role of transverse faults systems dominated by strike-slip motion in the evolution and perpetuation of the continental rift systems. These faults are of a greater geological persistence than the normal faults bounding the grabens, especially when they are located on major basement anisotropies.

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

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


    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.

  2. The Geomorphological Evolution of a Landscape in a Tectonically Active Region: the Sennwald Landslide (United States)

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


    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

  3. Global tectonics since the breakup of Pangea 180 million years ago: evolution maps and lithospheric budget (United States)

    Weijermars, Ruud

    Pangea, the Earth's youngest single supercontinent, broke up 180 million years ago. Tectonic plates were subsequently formed by dispersal of the continental fragments and accretion of new oceanic lithosphere. The configurations of all the major lithospheric plates at 0, 20, 65, 95, 140, 180 Ma BP are reconstructed on six globes of the Earth, each with a radius of 10 cm. It appears that plate boundaries maintain a remarkably close fit on model globes of constant radii if the reconstructions include the recovery of subducted spreading patterns. This is illustrated with maps in equatorial orthographic, oblique orthographic and transverse Hammer-Aitoff projections. The snug fit of the tectonic plates at every tested time since the breakup of Pangea 180 Ma BP is consistent with the theory of plate tectonics on a non-expanding Earth and contradicts rapidly expanding Earth models. The areas of oceanic lithosphere produced and consumed during the past 180 Ma BP are estimated from surface measurements of the globes reconstructed on the basis of particular assumptions. These measurements suggest a consistent increase in the production rate of oceanic lithosphere during the past 140 Ma. It was decided to revise the assumptions and see if alternative reconstructions of the ancient spreading patterns on the floors of the Tethys and Eo-Pacific oceans could avoid implying an increase of lithospheric production rates with time. This appeared to be possible. The revised maps suggest that ophiolites older than 180 Ma BP may have been obducted in Cenozoic collision zones of the Himalayas, Andes, Rockies, and the western part of the Banda Arc (Timor, New Guinea). Estimates of the ocean floor production and consumption budget appear to be quite similar for both map series, and only the possible ranges are summarized here, time averaged for the past 180 Ma. World-wide production and consumption of oceanic lithosphere appears to have varied between 2.6 and 3.5 km 2 a -1 at most. The mean

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

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


    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. Northwest margin of California continental borderland: marine geology and tectonic evolution. (United States)

    Crouch, J.K.


    The NW margin of the California continental border land consists of 2 NW-trending pre-Neogene lithologic belts blanketed by Miocene and younger strata. These represent facies corresponding to the subduction complex and forearc-basin deposits of a late Mesozoic and Paleogene continental-margin arc-trench system. The outer belt, which forms the acoustic basement is characterized by: 1) moderately high compressional velocities; 2) discordant and discontinuous seismic reflectors; and 3) nonfossiliferous and diverse rock types. Landward, the inner Great Valley sequence belt is characterized by: 1) intermediate compressional velocities; 2) concordant and relatively continuous reflectors, and 3) a thick turbidite sequence. Well-developed wrench-fault structures in overlying Miocene strata record a transition from Paleogene subduction to Neogene transform faulting. The timing of volcanism and uplift, and of the younger wrenching event, closely matches the plate-tectonic model of Atwater and Molnar.-from Author

  6. Interaction of tectonic and depositional processes that control the evolution of the Iberian Gulf of Cadiz margin (United States)

    Maldonado, A.; Nelson, C.H.


    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

  7. A numerical model of continental topographic evolution integrating thin sheet tectonics, river transport, and climate (United States)

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


    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.

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

    Carlotto, Víctor


    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. Evolution of Tidal Influence During the ETS Seismic Cycle Reveals Competition Between Tectonic Loading and Fault Healing (United States)

    Houston, H.


    Following the discovery of the evolution of tremor response to tidal stress over the duration of ETS slip at a spot (Houston 2015; Royer et al 2015;Yabe et al 2015), we investigate whether and how it may evolve between major large ETSs, which occur quasi-periodically in several subduction zones. Preliminary results show that tidal response does evolve over the average interETS period in northern Cascadia - decaying over the first quarter of the cycle to lowest values then climbing back up in the second half of the cycle part of the way toward the strong response seen late during major ETSs. Thus far, we have ignored the possible role of transient stresses during interETS tremor because tremor bursts are mostly small. We explore a strength-threshold model where tidal influence is stronger when stress is close to strength and weaker when they are farther apart. Shortly after a major ETS, both stress and strength are presumed to have fallen over the large region where slow slip occurred. Then, however, stress rebuilds quasi-linearly by plate tectonic loading, whereas strength rebuilds as the logarithm of time (e.g., Vidale et al 1994). Thus, model stress and strength diverge the most midway through the interETS cycle, the period of weakest tidal sensitivity. Tidal stresses become more effective in triggering tremor later in the cycle as the linearly-growing stress approaches the logarithmically-growing strength. This model broadly fits our observed evolution of tidal response. However, the tendency of ETSs to initiate downdip may require an additional process that varies along dip. This approach illuminates the competition between healing on the plate interface and reloading with tectonic stress, and can help constrain and perhaps even monitor physical conditions on the deep subduction interface. The figure shows the evolution of two measures of tidal influence on tremor, consistency and sensitivity (right), and the data on which they are based - probability

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

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


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

  11. 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


    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...

  12. Post-Variscan thermal and tectonic evolution of the KTB site and its surroundings

    NARCIS (Netherlands)

    Wagner, GA; Coyle, DA; Duyster, J; HenjesKunst, F; Peterek, A; Schroder, B; Stockhert, B; Wemmer, K; Zulauf, G; Ahrendt, H; Bischoff, R; Hejl, E; Jacobs, J; Menzel, D; Lal, N; VandenHaute, P; Vercoutere, C; Welzel, B


    The post-Carboniferous crustal evolution of the German Continental Deep Drilling Program (KTB) area, as summarized in this paper, could not be predicted from surface observations: deep drilling was essential for its revelation, The most conspicuous and unexpected feature discovered in the drill hole

  13. Cenozoic Landscape evolution of the South-African Plateau around the Orange Valley: tectonic and climate coupling (United States)

    Dauteuil, Olivier; Bessin, Paul; Guillocheau, François


    The plateaus form the key geomorphic element of the African relief with the occurrence of the South African (or Kalahari) Plateau, extending from South Africa to southern Congo (Fig. 1). The origin and evolution of this large relief with a mean elevation ranging 1 to 2 kilometres were largely debated. This work discussed the landscape growth of the South African plateau on both sides of the Orange valley in term of planation process, incision, deformation and climate change. This work is mainly based on a geomorphic analysis done from DEM and field data. First, we proposed a new typology of planation surfaces based on their genetic process (weathering versus erosion), and not depending the elevation, as previously. Five types of planation surfaces were retained: etchplain, peneplain, pediplain, top-weathering surface and wav-cut platform. Using this approach to determine the evolution of Orange valley, we recognised three planation surfaces of which origin is not controlled by the lithology: a top weathering surface recorded the end of Eocene weathering period, a first etchplain-to-pediplain formed during the Oligocene and finally a pediplain initiated after a deformation event during the Miocene. This event reorganised completely the drainage network and the catchment of the Orange River that became similar to the current one. It corresponds to a regional tilting of the southern part of the plateau with a elevation of 200 m at least. Afterwards, global eustatic variations driven the landscape evolution because the Orange River gained the current stream connected to the sea level. Thus the landscape growth of the South African plateau results in a change in planation processes driven by a first climate change occurring during a slow uplift, then a regional tilting and at least by eustasy. Thus, an accurate and detail geomorphic analysis allows discriminating the tectonic to climatic processes causing the current landscape.

  14. Magmatic and tectonic evolution of the Ladakh Block from field studies (United States)

    Raz, U.; Honegger, K.


    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

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

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


    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. Stress fields recorded on large-scale strike-slip fault systems: Effects on the tectonic evolution of crustal slivers during oblique subduction (United States)

    Veloso, Eugenio E.; Gomila, Rodrigo; Cembrano, José; González, Rodrigo; Jensen, Erik; Arancibia, Gloria


    In continental margins, large-scale, strike-slip fault-systems resulted from oblique subduction commonly exhibit a complex pattern of faulting where major faults define the inland boundary of tectonic slivers that can be detached from the margin. In turn, subsidiary faults bound and define internal tectonic blocks within the sliver which are expected to rotate, translate and/or internally disrupt in order to accommodate the internal deformation. The geometrical and spatial arrangement of faults and tectonic blocks thus determines the evolution of the sliver given a particular stress field regime. The Paposo segment of the Atacama Fault System in northern Chile displays a series of brittle faults whose orientations are hierarchically arranged: low-order faults splay off higher-order faults forming Riedel-type and strike-slip duplexes geometries at several scales. The master (1st- and highest-order) Paposo Fault defines the inland boundary of a tectonic sliver whereas subsidiary faults bound and disrupt internal tectonic blocks. By using newly collected brittle fault-slip data we estimated the orientations and regimes of the stress fields that acted upon the entire sliver, the different fault-orders and the tectonic blocks. Results indicate that an overall transtensional - with NW-compressional and NE-tensional principal axes - strike-slip regime affected the sliver and triggered the development of left-lateral strike-slip structures. An incomplete split of the stress field imposed by the subduction process resulted in the generation of a nested pattern of R-type faults as well as in a combined strike-slip/normal faulting disruption of the tectonic blocks within the sliver.

  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


    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. The Morphology of the Tasmantid Seamounts: Interactions between Tectonic Inheritance and Magmatic Evolution (United States)

    Richards, Fred; Kalnins, Lara; Watts, Anthony; Cohen, Benjamin; Beaman, Robin


    The Tasmantid seamounts extend for over 2000 km off the east coast of Australia and constitute one of three contemporaneous, sub-parallel Cenozoic hotspot tracks that traverse the region (the Tasmantid, Lord Howe, and East Australian volcanic chains), locally separated by as little as 500 km. Where dated, the three chains young from north to south, spanning ca. 34-6 Ma. At multiple locations, the Tasmantid chain intersects the extinct Tasman Sea spreading centre, which was active from 84 Ma to 53 Ma. Detailed morphological analysis reveals a strong correlation between tectonic setting, seamount orientation, and volcanic structure. Seamounts at inside corners of the spreading segment-transform intersections are more rugged and constructed via numerous intersecting fissure-fed volcanic ridges, whereas off-axis seamounts tend to be conical with summit craters and isolated dyke-fed flank cones. In addition, the orientation of the Bouguer gravity anomaly highs, interpreted as magmatic conduits, and the long axes of the seamounts align closely with the principal stress directions expected for a ridge system in which strong mechanical coupling occurs across transform faults. Such a strong connection between the long-lived mantle upwelling, ridge structure, and subsequent dyke emplacement ' despite the ≥ 20 Ma offset between spreading cessation and initial seamount emplacement ' suggests deep faulting of the Tasman Sea oceanic lithosphere in order to channel melts along pre-existing structural trends. Despite the large size of the edifices, up to ~ 4000 m high, slope gradient and backscatter analysis along the chain point to sluggish mass wasting rates with few or no large sector collapse structures. In addition, most seamounts are associated with Bouguer gravity highs. Together, these features suggest that the seamounts have dense, coherent cores with high intrusive to extrusive volume ratios. This indicates low rates of melt generation and intra-lithospheric transport

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

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


    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. Geochronology, geochemistry and tectonic evolution of the Western and Central cordilleras of Colombia (United States)

    Villagómez, Diego; Spikings, Richard; Magna, Tomas; Kammer, Andreas; Winkler, Wilfried; Beltrán, Alejandro


    Autochthonous rocks of the pre-Cretaceous continental margin of NW South America (the Tahami Terrane) are juxtaposed against a series of para-autochthonous rock units that assembled during the Early Cretaceous. Allochthonous, oceanic crust of the Caribbean Large Igneous Province collided with and accreted onto the margin during the Late Cretaceous. We present the first regional-scale dataset of zircon U-Pb LA-ICP-MS ages for intrusive and metamorphic rocks of the autochthonous Tahami Terrane, Early Cretaceous igneous para-autochthonous rocks and accreted oceanic crust. The U-Pb zircon data are complemented by multiphase 40Ar/ 39Ar crystallization and cooling ages. The geochronological data are combined with whole rock major oxide, trace element and REE data acquired from the same units to constrain the tectonic origin of the rock units and terranes exposed in the Western Cordillera, Cauca-Patía Valley and the Central Cordillera of Colombia. The Tahami Terrane includes lower Paleozoic orthogneisses (~ 440 Ma) that may have erupted during the active margin stage of the Rheic Ocean. Basement gneisses were intruded by Permian, continental arc granites during the final assembly of Pangea. Triassic sedimentary rocks were subsequently deposited in rift basins and partially melted during high-T metamorphism associated with rifting of western Pangea during 240-220 Ma. Continental arc magmatism during 180-145 Ma is preserved along the whole length of the Central Cordillera and was followed by an Early Cretaceous out-board step of the arc axis and the inception of the Quebradagrande Arc that fringed the continental margin. Back-stepping of the arc axis may have been caused by the collision of buoyant seamounts, which were coeval with plateau rocks exposed in the Nicoya Peninsular of Costa Rica. Rapid westward drift of South America closed the Quebradagrande basin in the late Aptian and caused medium-high P-T metamorphic rocks of the Arquía Complex to exhume and obduct onto

  1. 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


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

  2. Plio-Quaternary tectonic evolution off Al Hoceima, Moroccan Margin of the Alboran Basin. (United States)

    Lafosse, Manfred; d'Acremont, Elia; Rabaute, Alain; Mercier de Lépinay, Bernard; Gorini, Christian; Ammar, Abdellah; Tahayt, Abdelilah


    We use data from a compilation of industrial and academic 2D surveys and recent data from MARLBORO-1 (2011), MARLBORO-2 (2012), and SARAS (2012) surveys, which provide high resolution bathymetry and 2D seismic reflexion data. We focus on the key area located south of the Alboran Ridge and the Tofiño Bank, and encompassing the Nekor and Boudinar onshore-offshore basins on the Moroccan side of the Alboran Sea. The Nekor basin is a present pull-apart basin in relay between inherited N050° sinistral strike-slip faults. We consider that these faults define the Principal Displacement Zones (PDZ). The northern PDZ marks the position of the crustal Bokkoya fault, which is connected to the Al-Idrisi Fault Zone en relais with the Adra and Carboneras Fault Zones. On the seabed, right-stepping non-coalescent faults characterize the sinistral kinematics of the northern PDZ and give a general N050° azimuth for the crustal discontinuity. The southern PDZ corresponds to the Nekor fault Zone, a Miocene sinistral strike-slip fault acting as the structural limit of the External Rif. On its eastern edge, the Nekor basin is bounded by the N-S onshore-offshore Trougout fault, connecting the northern and the southern PDZ. The western boundary of the Nekor basin is marked by the Rouadi and El-Hammam Quaternary active N-S normal faults. In the offshore Nekor basin, recent N155° conjugated normal faults affect the seabed. Further east, the Boudinar basin is a Plio-Quaternary uplifted Neogene basin. The northeastern segment of the Nekor fault bounds this basin to the south but is inactive in the Quaternary. Normal east-dipping N150° faults are visible offshore in the continuity of the Boudinar fault. From our perspective, the orientation of major tectonic structures (Bokkoya, Nekor and Carboneras faults and the Alboran ridge) under the present compressive regime due to the Europe/Africa convergence is not compatible with a strike-slip motion. The orientation of the most recent Plio

  3. Structural evolution of the Rieserferner Pluton: insight into the localization of deformation and regional tectonics implications (United States)

    Ceccato, Alberto; Pennacchioni, Giorgio


    deformation structures within the RFP is controlled by the development and later reactivation in shear of two main sets of joints during cooling and progressive exhumation of the pluton. These joints were either exploited as faults or localized ductile shear zones. In the RFP, the kinematics of shear reactivation is complex, with the same joint set recording different senses of shear and transport directions. Preliminary kinematic analysis and qualitative paleostress reconstruction show that there has been a clockwise rotation of the main regional shortening direction from WNW-ESE, during the first ductile event, to N-S during later brittle deformation. These two different shortening directions fit with those inferred, respectively, for Austroalpine nappe stacking by Ratschbacher (1989) and for the Alpine convergence during late Oligocene-Miocene within the Tauern window (Pennacchioni & Mancktelow, 2007). References Cesare, B. (1994). Hercynite as the product of staurolite decomposition in the contact aureole of Vedrette di Ries, eastern Alps, Italy. Contributions to Mineralogy and Petrology, 116(3), 239-246. Pennacchioni, G., Di Toro, G., Brack, P., Menegon, L., & Villa, I. M. (2006). Brittle-ductile-brittle deformation during cooling of tonalite (Adamello, Southern Italian Alps). Tectonophysics, 427(1), 171-197. Pennacchioni, G., & Mancktelow, N. S. (2007). Nucleation and initial growth of a shear zone network within compositionally and structurally heterogeneous granitoids under amphibolite facies conditions. Journal of Structural Geology, 29(11), 1757-1780. Ratschbacher, L., Frisch, W., Neubauer, F., Schmid, S. M., & Neugebauer, J. (1989). Extension in compressional orogenic belts: the eastern Alps. Geology, 17(5), 404-407. Romer, R. L., & Siegesmund, S. (2003). Why allanite may swindle about its true age. Contributions to Mineralogy and Petrology, 146(3), 297-307. Steenken, A., Siegesmund, S., & Heinrichs, T. (2000). The emplacement of the Rieserferner Pluton (Eastern

  4. 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)


    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)

  5. Late Neogene stratigraphy and tectonic control on facies evolution in the Laguna Salada Basin, northern Baja California, Mexico (United States)

    Martín-Barajas, A.; Vázquez-Hernández, S.; Carreño, A. L.; Helenes, J.; Suárez-Vidal, F.; Alvarez-Rosales, J.


    The Laguna Salada Basin (LSB) in northeastern Baja California records late-Neogene marine incursions in the Salton Trough and progradation of the Colorado River delta. Early subsidence and subsequent tectonic erosion are related to evolution of the Sierra El Mayor detachment fault during late Miocene time (geothermal exploratory well on the eastern margin of LSB. Interfingering fluvial-sandstone deposits and prograding alluvial fanglomerates with coarse debris-flow and rock-avalanche deposits crudely mark the onset of vertical slip along the Laguna Salada fault and rapid uplift of Sierra Cucapa and Sierra El Mayor. Up to 2 km of Quaternary alluvial-fan and lacustrine deposits accumulated along the eastern margin of LSB, whereas lower subsidence rates produced a thinner sedimentary wedge over a ramp-like crystalline basement along the western margin. In early Pleistocene time (˜2-1 Ma), the Laguna Salada became progressively isolated from the Colorado River delta complex, and the Salton Trough by activity on the Elsinore and Laguna Salada fault zones.

  6. Jurassic extension and Cenozoic inversion tectonics in the Asturian Basin, NW Iberian Peninsula: 3D structural model and kinematic evolution (United States)

    Uzkeda, Hodei; Bulnes, Mayte; Poblet, Josep; García-Ramos, José Carlos; Piñuela, Laura


    We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.

  7. 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


    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.

  8. Variscan tectonics in Dodecanese, Kalymnos island, Greece (United States)

    Chatziioannou, Eleftheria; Grasemann, Bernhard; Schneider, David; Hubmann, Bernhard; Soukis, Konstantinos


    Kalymnos island is located in the Dodecanese, southeastern Aegean Sea, and geologically appears to be part of the external Hellenides. Pre-Alpidic basement rocks on the Dodecanese islands have been suggested to record compelling similarities with the basement rocks in Eastern Crete with respect to their lithologies and pre-Alpidic metamorphic evolution. The lithotectonic units experienced greenschist to amphibolite facies conditions during the Variscan orogeny. Whereas the rocks in Eastern Crete reveal Alpine high-pressure overprint, the Variscan basement units in the Dodecanese record no or low-grade Alpine metamorphism. A field study of basement rocks below Mesozoic limestones and dolomites in the NW part of Kalymnos near Emporios uncovered a complex history of metamorphism, folding and faulting. Three different tectonic units can be discriminated from top to bottom: a) a quartz-mica schist, b) a white-grey, fossiliferous coarse grained marble and c) a fine-grained fossiliferous blue-grey marble. In the marbles macrofossils such as brachiopods, ammonoid cephalopods (Goniatids?) and crinoids suggest a Middle-Upper Devonian deposition age (Givetian- Frasnian). Structural mapping the area resolved a dominant W-E shortening event, resulting in an overall inverted metamorphic gradient. The lowermost blue-grey marble unit is folded into large-scale upright folds, which are truncated by top-to-east overthrusting of the white-grey marble unit. Whereas deformation mechanisms in the blue-grey marble unit are dominated by dissolution-precipitation creep, the white-grey marble suffered intense crystal plastic deformation with localized high-strain mylonitic shear zones. The uppermost quartz-mica schist unit is separated from the lower units by a cataclastic phyllonitic shear zone. 40Ar/39Ar geochronological dating on white micas from the quartz-mica schists yielded cooling ages between 240 and 334 Ma indicative of Variscan cooling. Our data suggest that this part of the

  9. Tectonic and petrologic evolution of the Western Mediterranean: the double polarity subduction model (United States)

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


    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 (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 (United States)

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


    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 (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. Structure of Palaeogene sediments in east Ellesmere Island: Constraints on Eurekan tectonic evolution and implications for the Nares Strait problem (United States)

    Saalmann, K.; Tessensohn, F.; Piepjohn, K.; von Gosen, W.; Mayr, U.


    The "Nares Strait problem" represents a debate about the existence and magnitude of left-lateral movements along the proposed Wegener Fault within this seaway. Study of Palaeogene Eurekan tectonics at its shorelines could shed light on the kinematics of this fault. Palaeogene (Late Paleocene to Early Eocene) sediments are exposed at the northeastern coast of Ellesmere Island in the Judge Daly Promontory. They are preserved as elongate SW-NE striking fault-bounded basins cutting folded Early Paleozoic strata. The structures of the Palaeogene exposures are characterized by broad open synclines cut and displaced by steeply dipping strike-slip faults. Their fold axes strike NE-SW at an acute angle to the border faults indicating left-lateral transpression. Weak deformation in the interior of the outliers contrasts with intense shearing and fracturing adjacent to border faults. The degree of deformation of the Palaeogene strata varies markedly between the northwestern and southeastern border faults with the first being more intense. Structural geometry, orientation of subordinate folds and faults, the kinematics of faults, and fault-slip data suggest a multiple stage structural evolution during the Palaeogene Eurekan deformation: (1) The fault pattern on Judge Daly Promontory is result of left-lateral strike-slip faulting starting in Mid to Late Paleocene times. The Palaeogene Judge Daly basin formed in transtensional segments by pull-apart mechanism. Transpression during progressive strike-slip shearing gave rise to open folding of the Palaeogene deposits. (2) The faults were reactivated during SE-directed thrust tectonics in Mid Eocene times (chron 21). A strike-slip component during thrusting on the reactivated faults depends on the steepness of the fault segments and on their obliquity to the regional stress axes. Strike-slip displacement was partitioned to a number of sub-parallel faults on-shore and off-shore. Hence, large-scale lateral movements in the sum of 80

  14. 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 (United States)

    Kusák, Michal


    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

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


    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

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

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


    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.

  17. Formation and tectonic evolution of the Cretaceous Jurassic Muslim Bagh ophiolitic complex, Pakistan: Implications for the composite tectonic setting of ophiolites (United States)

    Khan, Mehrab; Kerr, Andrew C.; Mahmood, Khalid


    The Muslim Bagh ophiolitic complex Balochistan, Pakistan is comprised of an upper and lower nappe and represents one of a number of ophiolites in this region which mark the boundary between the Indian and Eurasian plates. These ophiolites were obducted onto the Indian continental margin around the Late Cretaceous, prior to the main collision between the Indian and Eurasian plates. The upper nappe contains mantle sequence rocks with numerous isolated gabbro plutons which we show are fed by dolerite dykes. Each pluton has a transitional dunite-rich zone at its base, and new geochemical data suggest a similar mantle source region for both the plutons and dykes. In contrast, the lower nappe consists of pillow basalts, deep-marine sediments and a mélange of ophiolitic rocks. The rocks of the upper nappe have a geochemical signature consistent with formation in an island arc environment whereas the basalts of the lower nappe contain no subduction component and are most likely to have formed at a mid-ocean ridge. The basalts and sediments of the lower nappe have been intruded by oceanic alkaline igneous rocks during the northward drift of the Indian plate. The two nappes of the Muslim Bagh ophiolitic complex are thus distinctively different in terms of their age, lithology and tectonic setting. The recognition of composite ophiolites such as this has an important bearing on the identification and interpretation of ophiolites where the plate tectonic setting is less well resolved.

  18. 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


    @@ 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.

  19. 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)


    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)

  20. Alpine dams

    Directory of Open Access Journals (Sweden)

    Alain Marnezy


    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.

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

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


    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

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

    Dong, Shunli; Li, Zhong; Jiang, Lei


    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

  3. Detrital zircon age populations from the Moine Supergroup, Scotland, and their implications for tectonic evolution (United States)

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


    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.

  4. 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


    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.

  5. Depositional Record of the Bagua Basin, Northern Peru: Implications for Climate and Tectonic Evolution of Tropical South America (United States)

    Moreno, F.; George, S. W. M.; Williams, L. A.; Horton, B. K.; Garzione, C. N.


    The Andes Mountains exert critical controls on the climate, hydrology, and biodiversity of South America. The Bagua Basin, a low elevation (400-600 m) intermontane basin in northern Peru, offers a unique opportunity to study the ecological, climatic, and structural evolution of the western topographic boundary of the Amazonian foreland. Situated between the Marañon fold-thrust belt of the Western Cordillera and basement block uplifts of the Eastern Cordillera, the Bagua region contains a protracted, semi-continuous record of Triassic through Pleistocene sedimentation. Whereas Triassic-Cretaceous marine deposits were potentially related to extension and regional thermal subsidence, a Paleocene-Eocene shift to shallow marine and fluvial systems marks the onset of foreland basin conditions. Oligocene-Miocene sedimentation corresponds to a braided-meandering fluvial system with exceptional development of paleosols. In this study, we use new detrital zircon U-Pb geochronologic and oxygen stable isotopic datasets to establish a chronology of pre-Andean and Andean processes within the Bagua Basin. Detrital zircon geochronology provides constraints on when the Western and Eastern cordilleras shed sediments into the basin. Syndepositional zircons within Eocene, Oligocene and Miocene strata provide key age control for a previously poorly constrained depositional chronology. Preliminary results suggest a dramatic provenance shift in which Paleocene deposits contain almost exclusively cratonic populations (500-1600 Ma) whereas Eocene deposits show a mix of syndepositional zircons from the magmatic arc, recycled Mesozoic zircons, and cratonic zircon populations. Oxygen stable isotopes (δ18O) of carbonate nodules from Neogene paleosols will help elucidate when the Eastern Cordillera became an orographic barrier intercepting moisture from the Amazon basin to the east. Together, these records will help uncover the history of tectonics and climate interaction in tropical South

  6. Petrologic perspectives on tectonic evolution of a nascent basin (Okinawa Trough) behind Ryukyu Arc:A review

    Institute of Scientific and Technical Information of China (English)

    YAN Quanshu; SHI Xuefa


    Okinawa Trough is a back-arc, initial marginal sea basin, located behind the Ryukyu Arc-Trench System. The formation and evolution of the Okinawa Trough is intimately related to the subduction process of the Philippine Sea Plate beneath the Eurasian Plate since the late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, such as the Mariana Trough and southern Lau Basin, all of which are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from the Okinawa Trough, Ryukyu Arc, and Philippine Sea Plate, combined with geophysical data to indicate the relationship between the subduction sources (input) and arc or back-arc magmas (output) in the Philippine Sea Plate-Ryukyu Arc-Okinawa Trough system (PROS). The results obtained showed that several components were variably involved in the petrogenesis of the Oki-nawa Trough lavas:sub-continental lithospheric mantle underlying the Eurasian Plate, Indian mid-oceanic ridge basalt (MORB)-type mantle, and Pacific MORB-type mantle. The addition of shallow aqueous fluids and deep hydrous melts from subducted components with the characteristics of Indian MORB-type mantle into the mantle source of lavas variably modifies the primitive mantle wedge beneath the Ryukyu and sub-continental lithospheric mantle (SCLM) beneath the Okinawa Trough. In the northeastern end of the trough and arc, instead of Indian MORB-type mantle, Pacific MORB-type mantle dominates the magma source. Along the strike of the Ryukyu Arc and Okinawa Trough, the systematic variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. In general, petrologic data, combined with geophysical data, imply that the Okinawa Trough is experiencing the“seafloor spreading”process in the southwest segment,“rift propagation”process in the middle seg-ment, and

  7. Late Cretaceous ARC to MORB compositional switch in the Quebradagrande Complex, Colombian Andes: understanding the long term tectonic evolution of a magmatic arc. (United States)

    Jaramillo, J. S.; Cardona, A.; Zapata, S.; Valencia, V.


    The spatial and compositional characters of arc rocks are sensible markers of the tectonic changes experienced by convergent margins and therefore provide a fundamental view to the continuous tectonic evolution of active margins. The Early to Late Cretaceous tectonic evolution of the Northern Andes have been related to the growth and accretion of different continental and oceanic arc systems that were juxtaposed at the beginning of the Andean Orogeny in the Late Cretaceous. The Quebradagrande Complex is a tectonostratigraphic unit made of mafic to intermediate plutonic rocks, basic to intermediate volcanic flows and associated marine sedimentary rocks that have been related to a single Albian arc or back-arc environment that discontinuously outcrops along the western margin of the Central Cordillera of Colombia. New field, geochronological and geochemical data from the plutonic and volcanic rocks of the Quebradagrande complex shows that the pre-90-80 Ma volcanic arc rocks are intruded by ca. 90 Ma pyroxene gabbroic and hornblende dioritic plutons with medium to pegmatitic grain size characterized by a contrasting MORB-type signature. We related the compositional change to a transient modification of the convergent margin system, where and extensional roll-back related configuration or the subduction of an oceanic ridge allows the flux of the astenospheric mantle. This continental magmatic arc was subsequently deformed due to the collision and accretion of an allocthonous oceanic arc that migrate from the southeast Pacific at the beginning of the Andean orogeny.

  8. 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


    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.%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。

  9. 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


    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.

  10. Tectonic evolution and crustal structure of the central Indonesian region from geology, gravity and other geophysical data (United States)

    Guntoro, Agus

    Bone Bay, the Makassar Strait, the Central Java Sea, the East Java Sea and the Flores Sea provinces. Each province is examined and their stratigraphy, structural and tectonic styles correlated in order to have a complete understanding of their evolution. Variations in gravity values and models demonstrate that the continental crust in the CIR was attenuated by subduction roll-back and then subjected to rifting by extensional forces. The extension in the Makassar Strait, Central Java Sea and East Java Sea took place in the Eocene, forming marginal basins. Bone Bay opened due to collision between the Banggai- Sula microcontinent and Sulawesi in the Middle Miocene and was followed by clockwise rotation of Java, Sumbawa and Flores which cause the opening of the Flores Sea. The present configuration of the CIR is influenced by the collision between the Indo-Australian Plate and the Banda-Sunda arcs.

  11. 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 (United States)

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


    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

  12. Internal structure and current evolution of very small debris-covered glacier systems located in alpine permafrost environments (United States)

    Bosson, Jean-Baptiste; Lambiel, Christophe


    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.

  13. Tectonic vs. gravitational morphostructures in the central Eastern Alps (Italy): Constraints on the recent evolution of the mountain range (United States)

    Agliardi, Federico; Zanchi, Andrea; Crosta, Giovanni B.


    Deep-seated gravitational slope deformations (DSGSDs) influence landscape development in tectonically active mountain ranges. Nevertheless, the relationships among tectonics, DSGSDs, and topography are poorly known. In this paper, the distribution of DSGSDs and their relationships with tectonic structures and active processes, surface processes, and topography were investigated at different scales. Over 100 DSGSDs were mapped in a 5000 km 2 sector of the central Eastern Alps between the Valtellina, Engadine and Venosta valleys. Detailed lineament mapping was carried out by photo-interpretation in a smaller area (about 750 km 2) including the upper Valtellina and Val Venosta. Fault populations were also analysed in the field and their mechanisms unravelled, allowing to identify different structural stages, the youngest being consistent with the regional pattern of the ongoing crustal deformation. Finally, four DSGSD examples have been investigated in detail by geological and 2D geomechanical modelling. DSGSDs affect more than 10% of the study area, and mainly cluster in areas where anisotropic fractured rock mass and high local relief occur. Their onset and development is subjected to a strong passive control by mesoscopic and major tectonic features, including regional nappe boundaries as well as NW-SE, N-S and NE-SW trending recent brittle structures. The kinematic consistency between these structures and the pattern of seismicity suggests that active tectonics may force DSGSDs, although field evidence and numerical models indicate slope debuttressing related to deglaciation as a primary triggering mechanism.

  14. Early Paleozoic magmatic history of central Inner Mongolia, China: implications for the tectonic evolution of the Southeast Central Asian Orogenic Belt (United States)

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


    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.

  15. Implications for the tectonic transition zone of active orogeny in Hoping drainage basin, by landscape evolution at the multi-temporal timescale (United States)

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


    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

  16. 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


    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.

  17. Seismic site characterization for the Deep-Fault-Drilling-Project Alpine Fault (United States)

    Glomb, Vera; Buske, Stefan; Kovacs, Adrienn; Gorman, Andrew


    The Alpine Fault in New Zealand (South Island) is one of the largest active plate-bounding continental fault zones on earth with earthquakes of magnitude 7.9 occuring every 200-400 years. Due to the surface exposure and the shallow depth of mechanical and chemical transitions it is a globally significant natural laboratory. Within the ICDP Deep-Fault-Drilling-Project Alpine Fault (DFDP-AF; a drill hole shall give insight into the geological structure of the fault zone and its evolution to understand the related deformation and earthquake processes. With the help of advanced seismic imaging techniques the shallow structure of the Alpine Fault is imaged to find the most suitable drill site location. A new seismic reflection profile has been acquired in 2011 by the WhataDUSIE project team consisting of partners from the University of Otago (New Zealand), TU Bergakademie Freiberg (Germany) and the University of Alberta (Canada). The reflection profile, located in the Whataroa river valley, has a total length of about 5 km. Up to 643 geophones with spacings between 4-8 m recorded the approximately 100 shot points along the profile line. Single shot gathers as well as preliminary imaging results will be presented. The high-quality data show various indicators of the Alpine Fault such as strong reflections and distorted first-arrival wavefields which are clearly visible already in single shot gathers. With the help of high resolution seismic images we can study the shallow structures of the subsurface thus gaining information about the location and dip of reflectors. Further detailed processing and intensive interpretative work will enable a seismic site characterization providing important information for the selection of the borehole location. Additionally the high resolution seismic images themselves allow a better understanding of the tectonic and geodynamic settings.

  18. Mesozoic Cenozoic tectonic evolution of the Zhuanghai area, Bohai-Bay Basin, east China: the application of balanced cross-sections (United States)

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


    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.

  19. Structure and tectonic evolution of the NE segment of the Polish-Ukrainian Carpathians during the Late Cenozoic: subsurface cross-sections and palinspastic models (United States)

    Kuśmierek, Jan; Baran, Urszula


    The discrepant arrangement of the Carpathian nappes and syntectonic deposits of the Carpathian Foredeep reveals the oroclinal migration of the subduction direction of the platform margin during the Late Cenozoic. Formation of the nappes was induced by their detachment from disintegrated segments of the European Platform; the segments were shortened as a result of their vertical rotation in zones of compressional sutures. It finds expression in local occurrence of the backward vergence of folding against the generally forward vergence toward the Carpathian Foredeep. The precompressional configuration of sedimentation areas of particular nappes was reconstructed with application of the palinspastic method, on the basis of the hitherto undervalued model which emphasizes the influence of the subduction and differentiated morphology of the platform basement on the tectonic evolution of the fold and thrust belt. Superposition of the palaeogeographic representations and the present geometry of the orogen allows understanding of the impact of the magnitudes of tectonic displacements on the differentiation of the geological structure in the NE segment of the Carpathians. The differentiation has inspired different views of Polish and Ukrainian geologists on structural classification and evolution of the frontal thrusts.

  20. 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 (United States)

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


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

  1. Plants in alpine environments (United States)

    Germino, Matthew J.


    Alpine and subalpine plant species are of special interest in ecology and ecophysiology because they represent life at the climate limit and changes in their relative abundances can be a bellwether for climate-change impacts. Perennial life forms dominate alpine plant communities, and their form and function reflect various avoidance, tolerance, or resistance strategies to interactions of cold temperature, radiation, wind, and desiccation stresses that prevail in the short growing seasons common (but not ubiquitous) in alpine areas. Plant microclimate is typically uncoupled from the harsh climate of the alpine, often leading to substantially warmer plant temperatures than air temperatures recorded by weather stations. Low atmospheric pressure is the most pervasive, fundamental, and unifying factor for alpine environments, but the resulting decrease in partial pressure of CO2 does not significantly limit carbon gain by alpine plants. Factors such as tree islands and topographic features create strong heterogeneous mosaics of microclimate and snow cover that are reflected in plant community composition. Factors affecting tree establishment and growth and formation of treeline are key to understanding alpine ecology. Carbohydrate and other carbon storage, rapid development in a short growing season, and physiological function at low temperature are prevailing attributes of alpine plants. A major contemporary research theme asks whether chilling at alpine-treeline affects the ability of trees to assimilate the growth resources and particularly carbon needed for growth or whether the growth itself is limited by the alpine environment. Alpine areas tend to be among the best conserved, globally, yet they are increasingly showing response to a range of anthropogenic impacts, such as atmospheric deposition.

  2. Morphological expression of active tectonics in the Southern Alps (United States)

    Robl, Jörg; Heberer, Bianca; Neubauer, Franz; Hergarten, Stefan


    Evolving drainage pattern and corresponding metrics of the channels (e.g. normalized steepness index) are sensitive indicators for tectonic or climatic events punctuating the evolution of mountain belts and their associated foreland basins. The analysis of drainage systems and their characteristic properties represents a well-established approach to constrain the impact of tectonic and climatic drivers on mountainous landscapes in the recent past. The Southern Alps (SA) are one of the seismically most active zones in the periphery of northern Adria. Recent deformation is caused by the ongoing convergence of the Adriatic and European plate and is recorded by numerous earthquakes in the domain of the SA. Deformation in the SA is characterized by back-thrusting causing crustal thickening and should therefore result in uplift and topography formation. The vertical velocity field determined by GPS-data clearly indicates a belt of significant uplift in the south South alpine indenter between Lake Garda in the west and the Triglav in the east and strong subsidence of the foreland basin surrounding the Mediterranean Sea near Venice, although subsidence is often related to ongoing subduction of the Adriatic microplate underneath Appennines. Despite of these short term time series, timing, rates and drivers of alpine landscape evolution are not well constrained and the linkage between crustal deformation and topographic evolution of this highly active alpine segment remains unclear for the following reasons: (1) The eastern Southern Alps were heavily overprinted by the Pleistocene glaciations and tectonic signals in the alpine landscape are blurred. Only the transition zone to the southern foreland basin remained unaffected and allows an analysis of a glacially undisturbed topography. (2) The major part of this domain is covered by lithology (carbonatic rocks) which is unsuitable for low temperature geochronology and cosmogenic isotope dating so that exhumation and erosion

  3. The fluid budget of a continental plate boundary fault: Quantification from the Alpine Fault, New Zealand (United States)

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


    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

  4. Integration of natural data within a numerical model of ablative subduction: A possible interpretation for the Alpine dynamics of the Austroalpine crust. (United States)

    Roda, M.; Spalla, M. I.; Marotta, A. M.


    A numerical modelling approach is used to validate the physical and geological reliability of the ablative subduction mechanism during Alpine convergence in order to interpret the tectonic and metamorphic evolution of an inner portion of the Alpine belt: the Austroalpine Domain. The model predictions 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 evolution 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 configuration of this part of the Alps. There is less agreement between the model predictions and the natural data for the Austroalpine of the Central-Eastern Alps. Based on the natural data available in the literature, a critical discussion of the other proposed mechanisms is presented, and additional geological factors that should be considered within the numerical model are suggested to improve the fitting to the numerical results; these factors include variations in the continental and/or oceanic thickness, variation of the subduction rate and/or slab dip, the initial thermal state of the passive margin, the occurrence of continental collision and an oblique convergence.

  5. Tectonic Geomorphology. (United States)

    Bull, William B.


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

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

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


    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.

  7. Analysis of the geological structure and tectonic evolution of Xingning-Jinghai sag in deep water area, northern South China Sea (United States)

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


    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

  8. 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


    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.

  9. 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)

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

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


    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 (United States)

    Reiche, Sönke; Hübscher, Christian; Ehrhardt, Axel


    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) (United States)

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


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


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


    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...

  15. Digital Tectonics

    DEFF Research Database (Denmark)

    Christiansen, Karl; Borup, Ruben; Søndergaard, Asbjørn;


    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....

  16. A numerical model of continental-scale topographic evolution integrating thin sheet tectonics, river transport, and orographic precipitation (United States)

    Garcia-Castellanos, Daniel; Jimenez-Munt, Ivone


    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.

  17. 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


    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...


    Directory of Open Access Journals (Sweden)

    Natalia M. Levashova


    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.

  19. Evolution of the late Quaternary San Gregorio Magno tectono-karstic basin (southern Italy) inferred from geomorphological, tephrostratigraphical and palaeoecological analyses: tectonic implications (United States)

    Aiello, G.; Ascione, A.; Barra, D.; Munno, R.; Petrosino, P.; Russo Ermolli, E.; Villani, F.


    The Pantano di San Gregorio Magno is a 4.7 km2 large tectono-karstic basin located in the axial belt of the Southern Apennines, an area affected by intense seismicity. The basin was formed in the Middle Pleistocene and is presently undissected. It is filled by lacustrine sediments (clays, silts and pyroclastic sands) passing laterally into alluvial fan deposits. Geomorphological investigations were integrated with tephrostratigraphical, palynological and palaeoecological analyses of a 61 m thick core (not reaching the bedrock). The multiproxy analysis of the S. Gregorio Magno record shows that, over the last 200k yr, the basin hosted a freshwater lake with an oscillating level. Age constraints provided by the tephrostratigraphic record allowed estimation of the sedimentation rate, which varied strongly through time. Evolution of the basin resulted from the complex combination of tectonic subsidence, karst processes and changing amounts of sedimentary inputs. The latter was influenced by allogenic contributions related both to primary and reworked volcanoclastic inputs and was climate-driven. The overall evidence, which indicates that in the long-term the accumulation rate substantially counterbalanced the accommodation space created by faulting, suggests that the basin evolution was also modulated by changing subsidence rates. Copyright

  20. Joint development and tectonic stress field evolution in the southeastern Mesozoic Ordos Basin, west part of North China (United States)

    Jiang, Lin; Qiu, Zhen; Wang, Qingchen; Guo, Yusen; Wu, Chaofan; Wu, Zhijie; Xue, Zhenhua


    Major joint sets trending E-W (J1), ENE-WSW (J2), NE-SW (J3), N-S (J4), NNW-SSE (J5), NNE-SSW (J6), NW-SE (J7), and WNW-ESE (J8) respectively are recognized in Mesozoic strata within the southeast of Ordos Basin. Among them, the J1, J2 and J3 joint sets are systematic joints, while the other five joint sets (J4, J5, J6, J7, J8) are nonsystematic joints. There are three groups of orthogonal joint systems (i.e. J1 and J4 sets, J2 and J5 sets, and J6 and J8 sets) and two groups of conjugate shear fractures (ENE-WSW and NNE-SSW, ENE-WSW and ESE-WNW) in the study area. Joint spacing analysis indicates that: (1) layer thickness has an effect on the joint spacing, but the correlation of joint spacing and layer thickness is low; (2) joint density of systematic joints is greater than nonsystematic joints, and the joint density of a thin layer is also greater than that of a thick layer; and (3) the joints of Mesozoic strata in the basin are the result of tectonic events affected by multiple stress fields. All these joints in the Mesozoic strata are formed in the two main tectonic events since Late Mesozoic times. One is the westward subduction of the Pacific Plate beneath the Eurasia Plate, which formed the approximately E-W-trending compressive stress field in the China continent. The trends of the J1 joint set (E-W) and the bisector of conjugate shear fractures composed of ENE-WSW and ESE-WNW fractures are all parallel to the trend of maximum compressive stress (E-W). The other stress field is related to the collision of the Indian and Eurasian Plates, which formed the NE-SW-trending compressive stress field in the China continent. The trends of the J3 joint set and bisector of conjugate shear fractures composed of ENE-WSW and NNE-SSW fractures are all parallel to the trend of maximum compressive stress (NE-SW). Finally, we conclude that the J1 and J4 sets are formed in the E-W-trending compressive stress field, and the J2, J3, J5, J6, J7 and J8 sets are formed in the NE

  1. Indirect estimation of the tectonic evolution of magnetic structures along the Indiavaí-Lucialva Shear Zone, Mato Grosso, Brazil (United States)

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


    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

  2. Insights on the Quaternary Tectonic Evolution of the SE Indonesia Arc-Continent Collision from the Study of Uplifted Coral Terraces on Sumba Island. (United States)

    Leclerc, F.; Rigaud, S.; Chiang, H. W.; Djamil, Y. S.; Herdiyanti, T.; Johnny, J.; Ildefonso, S.; Meilano, I.; Bijaksana, S.; Abidin, H. Z.; Tapponnier, P.; Wang, X.


    Sumba Island is uniquely positioned within the Sunda-Banda forearc, at the transition between oceanic subduction and arc-continent collision. There, the convergence between the Sunda and Australian plates is accommodated along at least three major structures: the megathrust, the Savu backthrust located south of Sumba and the Flores backthrust located north of the volcanic arc. The incipient collision in the vicinity of Sumba is responsible for coastal vertical movements. Quaternary reefal deposits form spectacular uplifted flights of terraces, which directly overlie Mid Miocene - Early Pliocene deep carbonate and volcaniclastic rocks at elevations exceeding 500m. Although aerial fossil reefs extensively rim the northern and eastern coasts of Sumba, studies have been limited to Cape Laundi where an uplift rate of 0.2-0.5 m/kyr is estimated for the last 400 kyr, partly on the basis of alpha-spectrometric U/Th dating. At the island scale, the relief morphology and the hydrographic network point to a N-S asymmetry, indicating a general tilt toward the north. A subducting seafloor asperity and south-dipping normal faults have been postulated to generate this asymmetry. However as the pattern and kinematics of the deformation remain partially determined, structures and processes capable of driving such deformation and accommodating the nascent collision may be undisclosed. New topographic data coupled with field observations and coral mass-spectrometric U/Th dating allow investigating the morphology, stratigraphy and age of the fossil reef terraces at the island scale. Tectonic structures disrupting the topography are identified and their activities are relatively dated with respect to fossil reef terraces. The deformation pattern of Sumba is characterized, especially in Cape Laundi where the uplift rate is re-evaluated. Through a multi-disciplinary study, we intend to reconstruct the tectonic evolution of Sumba island and, at a larger scale, of the collision in SE

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

    Jakob, Johannes; Johnston, Stephen


    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.

  4. Evolution of the western segment of Juan Fernández Ridge (Nazca Plate): plume vs. plate tectonic processes (United States)

    Lara, Luis E.; Rodrigo, Cristián; Reyes, Javier; Orozco, Gabriel


    The Juan Fernandez Ridge (Eastern Pacific, Nazca Plate) is thought to be a classic hot spot trail because of the apparent age progression observed in 40Ar-39Ar data. However, geological evidence and some thermochronological data suggest a more complex pattern with a rejuvenation stage in Robinson Crusoe Island, the most eroded of the Juan Fernandez Archipelago. In fact, a postshield stage at 900-700 ka separates the underlying shield-related pile from the post-erosional alkaline succession (Ba/Yb=38.15; La/Yb=15.66; Ba/Y=20.27; Ba/Zr=2.31). Shield volcanoes grew at high effusion rate at ca. 5-4 Ma erupting mostly tholeiitic to transitional magmas (Ba/Yb=18.07-8.32; La/Yb=4.59-9.84; Ba/Y=4.24-8.18; Ba/Zr=0.73-1.09). Taken together, shield volcanoes form a continuous plateau with a base at ca. 3900 mbsl. However, a more complex structural pattern can be inferred from geophysical data, which suggest some intracrustal magma storage and a more extended area of magma ascent. A role for the Challenger Fracture Zone is hypothesized fueling the controversy between pristine plume origin and the effect of plate tectonic processes in the origin of intraplate volcanism. This research is supported by FONDECYT Project 1110966.

  5. Tectonic Evolution of the Careón Ophiolite (Northwest Spain): A Remnant of Oceanic Lithosphere in the Variscan Belt. (United States)

    Díaz García F; Arenas; Martínez Catalán JR; González del Tánago J; Dunning


    Analysis of the Careón Unit in the Ordenes Complex (northwest Iberian Massif) has supplied relevant data concerning the existence of a Paleozoic oceanic lithosphere, probably related to the Rheic realm, and the early subduction-related events that were obscured along much of the Variscan belt by subsequent collision tectonics. The ophiolite consists of serpentinized harzburgite and dunite in the lower section and a crustal section made up of coarse-grained and pegmatitic gabbros. An Early Devonian zircon age (395+/-2 Ma, U-Pb) was obtained in a leucocratic gabbro. The whole section was intruded by numerous diabasic gabbro dikes. Convergence processes took place shortly afterward, giving rise to a mantle-rooted synthetic thrust system, with some coeval igneous activity. Garnet amphibolite, developed in metamorphic soles, was found discontinuously attached to the thrust fault. The soles graded downward to epidote-amphibolite facies metabasite and were partially retrogressed to greenschist facies conditions. Thermobarometric estimations carried out at a metamorphic sole (T approximately 650 degrees C; P approximately 11.5 kbar) suggested that imbrications developed in a subduction setting, and regional geology places this subduction in the context of an early Variscan accretionary wedge. Subduction and imbrication of oceanic lithosphere was followed by underthrusting of the Gondwana continental margin.

  6. 样子哨盆地构造演化特征%Tectonic evolution characteristics of Yangzishao Basin

    Institute of Scientific and Technical Information of China (English)

    惠艳梅; 吕鹏


    样子哨盆地基底为龙岗地块,盖层以晚元古代地层、古生代地层为主。基底构造变形以韧塑性变形和塑性纵弯柔流褶皱及固态流变剪切变形为主,发生片理、片麻理、褶皱及条带状构造。盖层经历多次挤压隆升和拉张断陷运动,屡次遭受海侵—海退,沉积了典型的地台型沉积建造。后经断块运动,改造或继承先期断裂,形成盆地—山岭式构造。%Yangzishao Basin basement is Longgang land mass,cover rock is mainly Late Proterozoic and Paleozoic strata.The basal tectonic deformation is mainly tough plastic deformation and plastic vertical soft curved flow folds and solid rheological shear deformation,occurred schistosity,gneissosity folds and banded structure.The cover rock experienced many compression uplift and extensional rift motion,repeatedly suffered transgressive-regressive,and deposited a typical platform sedimentary formation.After the block movement,transformed or inherited pre-fractures formatted the Basin – mountain structure.

  7. 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)


    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.

  8. Textile Tectonics

    DEFF Research Database (Denmark)

    Mossé, Aurélie


    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

  9. Dinosaur tectonics

    DEFF Research Database (Denmark)

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


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

  10. Everyday Tectonics?

    DEFF Research Database (Denmark)

    Hvejsel, Marie Frier; Beim, Anne


    approach to architecture understood as a spatial unification of aesthetics and technique wherein which structure and materials carry and amplify the spatial experience. But, we as a profession we have difficulties to extract, develop, and apply this sort of tectonic knowledge related to everyday practices....... This circumstance posesing a major challenges to the development and range of our discipline, an issue that and this problem we have tried to addressraised for the first timeinitially in a theme issue of the Nordic Journal of Architectural Research titled; Everyday Tectonics, and an effort that this paper.......e. prefabricated concrete walls, beam, columns, window deliveries etc. as spatial gestures. Because of its etymological origin as a description of the fundamental task of the Greek tekton, to unite aesthetics and technique in the creation of architecture, it is our hypothesis that the notion of tectonics holds...

  11. 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


    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.

  12. 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 (United States)

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


    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

  13. Tree Tectonics (United States)

    Vogt, Peter R.


    Nature often replicates her processes at different scales of space and time in differing media. Here a tree-trunk cross section I am preparing for a dendrochronological display at the Battle Creek Cypress Swamp Nature Sanctuary (Calvert County, Maryland) dried and cracked in a way that replicates practically all the planform features found along the Mid-Oceanic Ridge (see Figure 1). The left-lateral offset of saw marks, contrasting with the right-lateral ``rift'' offset, even illustrates the distinction between transcurrent (strike-slip) and transform faults, the latter only recognized as a geologic feature, by J. Tuzo Wilson, in 1965. However, wood cracking is but one of many examples of natural processes that replicate one or several elements of lithospheric plate tectonics. Many of these examples occur in everyday venues and thus make great teaching aids, ``teachable'' from primary school to university levels. Plate tectonics, the dominant process of Earth geology, also occurs in miniature on the surface of some lava lakes, and as ``ice plate tectonics'' on our frozen seas and lakes. Ice tectonics also happens at larger spatial and temporal scales on the Jovian moons Europa and perhaps Ganymede. Tabletop plate tectonics, in which a molten-paraffin ``asthenosphere'' is surfaced by a skin of congealing wax ``plates,'' first replicated Mid-Oceanic Ridge type seafloor spreading more than three decades ago. A seismologist (J. Brune, personal communication, 2004) discovered wax plate tectonics by casually and serendipitously pulling a stick across a container of molten wax his wife and daughters had used in making candles. Brune and his student D. Oldenburg followed up and mirabile dictu published the results in Science (178, 301-304).

  14. Edaphics, active tectonics and animal movements in the Kenyan Rift - implications for early human evolution and dispersal (United States)

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


    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

  15. The western submerged sector of the Ischia volcanic island (Tyrrhenian Sea, Italy): new insights into its volcano-tectonic evolution (United States)

    Passaro, Salvatore; de Alteriis, Giovanni; Milano, Girolamo; Fedi, Maurizio; Florio, Giovanni


    The Island of Ischia is a volcanic complex located in the northern boundary of the Gulf of Naples (south-eastern Tyrrhenian Sea, Italy). The island represents only the 30% of a larger, E-W trending, volcanic ridge and likely controlled by a regional tectonic lineament. Despite the many geo-volcanological and geophysical investigations conducted on the island since long time, still little is the knowledge of its offshore. Several marine surveys have been carried out over the past 10 years from IAMC - CNR research institute (Naples, Italy) mostly in the frame of INGV and GNV projects, funded by Italy Civil Protection Department. Such surveys have largely improved the knowledge of the entire volcanic complex. Multibeam bathymetry surveys has revealed several, previously unexpected, morphological and morphostructural features. Moreover some structural patterns and volcano alignments offshore show similarities with those occurring at a regional scale in the Campania region and, locally, between the island of Procida and Phlegrean Fields. Here we report the joint interpretation of geophysical data focused on the western underwater sector of the island. Interpretation was chiefly based on processing/inversion of magnetic data in turn constrained by bathymetry and seismic reflection profiles. Magnetic data, acquired by the IAMC during two different cruises in 2000 and 2002 onboard of the Urania R/V oceanographic vessel, put in evidence that the western seafloor of Ischia is characterized by the presence of a strong residual magnetic anomaly field of complex behaviour, somewhere correlated to local bathymetry. These two last methods allowed to define and distinguish between undersea and subsurface magnetic (i.e. magmatic) basement. Interpretation was also constrained by seismological data.

  16. Structural and geochronological constraints on the Pan-African tectonic evolution of the northern Damara Belt, Namibia (United States)

    Lehmann, Jérémie; Saalmann, Kerstin; Naydenov, Kalin V.; Milani, Lorenzo; Belyanin, George A.; Zwingmann, Horst; Charlesworth, Guy; Kinnaird, Judith A.


    The Pan-African Orogen formed by convergence of numerous continental blocks during the Neoproterozoic to early Cambrian. This convergence eventually led to amalgamation of Gondwana, a supercontinent crosscut by a network of highly oblique linear orogenic belts that locally intersect each other, as in NW Namibia, where the NNW trending Kaoko Belt joins the NE trending Damara Belt. The northern Damara Belt has preserved well three regional Pan-African tectonic events due to the dominance of weak Neoproterozoic marine sediments (Damara Supergroup) that have been affected by low-grade metamorphism. A newly discovered early N-S horizontal contraction, dated by 40Ar/39Ar at ~590 Ma, is tentatively linked to convergence between the Congo and Kalahari cratons. This was superseded by collision between the Congo and Rio de la Plata cratons between 580 and 530 Ma that thickened and exhumed the orogenic crust of the Kaoko Belt and produce upper crustal N-S oriented folds of earlier fold trains and associated axial planar schistosities in the northern Damara Belt. A switch from E-W to NW-SE horizontal shortening occurred at ~530 Ma as a result of collision with the Kalahari Craton, triggering extensive syn-orogenic magmatism in the entire Damara Belt. During this last event, southward indentation and underthrusting of the Congo Craton promontory below the Neoproterozoic cover sequences produced a deformation front in the northern Damara Belt. Our results show that highly oblique convergent processes competed over a period of ~120 Ma to build Gondwana in Namibia during the late Neoproterozoic to early Cambrian.

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

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


    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

  18. New CHIRP Seismic Images of Submarine Terraces Around San Clemente Island Constrain its Tectonic Evolution and Geomorphology (United States)

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


    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.

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

    Institute of Scientific and Technical Information of China (English)


    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.

  20. 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


    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

  1. Tectonic evolution of the Irtysh collision belt: New zircon U-Pb ages of deformed and collisional granitoids in the Kalaxiangar area, NW China (United States)

    Tao, Hong; Jun, Gao; Xingwang, Xu; Klemd, Reiner


    The CAOB is thought to have formed by multiple accretion and collision of various microcontinents, island arcs, oceanic plateaus and accretionary wedges due to the closure of the Paleo-Asia Ocean [1, 2, 3]. The Irtysh collision belt is located at the middle-western part of the CAOB and generally thought to be the result of the collision of the Sawuer Island arc and the Altay Terrane, subsequent to the consumption of the Early Paleozoic Junggar Ocean, a branch of Paleo-Asia Ocean. Therefore, the exact timing of the Irtysh collision belt is crucial for a better understanding of the tectonic evolution of this collision belt and will provide constraints on the evolution of the CAOB. Recently, we discovered various collisional granitoids in the Kalaxiangar tectonic belt (KTB), which is located in the eastern part of the Irtysh collision belt. In this contribution, we report new geochemical whole-rock, zircon U-Pb and Hf isotopic data of the arc-related and collisional granitoids. Our new results reveal that 1) the arc-related granodioritic porphyries formed at ca. 374 Ma. Furthermore, recrystallized zircons from the granodioritic mylonite and ultramylonite of the Laoshankou ductile deformation zone have a similar U-Pb age of ca. 360 Ma; 2) the syn-collisional granodioritic porphyries, which distribute along cleavege, were emplaced at ca. 355 Ma; 3) the post-collisional A-type granodioritic porphyry, which cuts the NW-NNW trending schistosity at a low angle, has an age of ca. 323 Ma, ɛHf(t) values from + 7.5 to + 14.4, and young Hf model ages between 387 and 658 Ma; 4) the post-collisional A-type granite dykes, which are exposed along strike-slip faults, have ages between 282.5 and 279.2Ma, ɛHf(t) values from + 4.8 to + 12.6, and Hf model ages between 436 and 729 Ma; 5) the A-type biotite granite dykes that intruded along conjugate tension joints have ages between 273.9 and 271.4 Ma, ɛHf(t) values from + 1.1 to + 12.8, and Hf model ages between 393 and 979 Ma. In

  2. Structural evolution of the Sarandí del Yí Shear Zone, Uruguay: kinematics, deformation conditions and tectonic significance (United States)

    Oriolo, S.; Oyhantçabal, P.; Heidelbach, F.; Wemmer, K.; Siegesmund, S.


    The Sarandí del Yí Shear Zone is a crustal-scale shear zone that separates the Piedra Alta Terrane from the Nico Pérez Terrane and the Dom Feliciano Belt in southern Uruguay. It represents the eastern margin of the Río de la Plata Craton and, consequently, one of the main structural features of the Precambrian basement of Western Gondwana. This shear zone first underwent dextral shearing under upper to middle amphibolite facies conditions, giving rise to the reactivation of pre-existing crustal fabrics in the easternmost Piedra Alta Terrane. Afterwards, pure-shear-dominated sinistral shearing with contemporaneous magmatism took place under lower amphibolite to upper greenschist facies conditions. The mylonites resulting from this event were then locally reactivated by a cataclastic deformation. This evolution points to strain localization under progressively retrograde conditions with time, indicating that the Sarandí del Yí Shear Zone represents an example of a thinning shear zone related to the collisional to post-collisional evolution of the Dom Feliciano Belt that occurred between the Meso- to Neoproterozoic (>600 Ma) and late Ediacaran-lower Cambrian times.

  3. Tectonic evolution of the southern margin of the Amazonian craton in the late Mesoproterozoic based on field relationships and zircon U-Pb geochronology

    Directory of Open Access Journals (Sweden)



    Full Text Available New U-Pb zircon geochronological data integrated with field relationships and an airborne geophysical survey suggest that the Nova Brasilândia and Aguapeí belts are part of the same monocyclic, metaigneous and metasedimentary belt formed in the late Mesoproterozoic (1150 Ma-1110 Ma. This geological history is very similar to the within-plate origin of the Sunsás belt, in eastern Bolivia. Thus, we propose that the Nova Brasilândia, Aguapeí and Sunsás belts represent a unique geotectonic unit (here termed the Western Amazon belt that became amalgamated at the end of the Mesoproterozoic and originated through the reactivation of a paleo-suture (Guaporé suture zone in an intracontinental rift environment. Therefore, its geological history involves a short, complete Wilson cycle of ca. 40 Ma. Globally, this tectonic evolution may be related with the final breakup of the supercontinent Columbia. Mafic rocks and trondhjemites in the northernmost portion of the belt yielded U-Pb zircon ages ca. 1110 Ma, which dates the high-grade metamorphism and the closure of the rift. This indicates that the breakup of supercontinent Columbia was followed in short sequence by the assembly of supercontinent Rodinia at ca. 1.1-1.0 Ga and that the Western Amazon belt was formed during the accretion of the Arequipa-Antofalla basement to the Amazonian craton.

  4. Tectonic uplift and sedimentary evolution of the Jiuxi Basin in the northern margin of the Tibetan Plateau since 13 Ma BP

    Institute of Scientific and Technical Information of China (English)

    宋春晖; 方小敏; 李吉均; 高军平; 赵志军; 范马洁


    Sediments shed from the northern margin of the Tibetan Plateau, the Qilian Mountains, are widely deposited in the foreland basin, the Jiuxi Basin, archiving plenty of information about the mountain surface uplift and erosion history. The Laojunmiao section, 1960 m thick, representing the upper sequence of the Cenozoic basin sediments, is paleomagnetically dated to about 13-0 Ma BP. Detailed sedimentary study of this sequence has revealed five sedimentary fades associations which determine four stages of sedimentary environment evolution. They are: (I) the half-deep lake system before 12.18 Ma BP, (Ⅱ) the shallow lake system between 12.18 and 8.26 Ma BP, (Ⅲ) the fan delta dominated sedimentary system in dry climate between 8.26 and 6.57 Ma BP, and (IV) alluvial fan system since 6.57 Ma BP. The associated mountain erosion and uplift are suggested to have experienced three phases, that is, tectonic stable (13-8.26 Ma BP), gradual uplift (8.26-<4.96 Ma BP), and rapid intermittent uplift (>3.66-0 Ma BP). Th

  5. 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)


    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.

  6. Chronology and geochemistry of Mesozoic granitoids in the Bengbu area, central China: Constraints on the tectonic evolution of the eastern North China Craton (United States)

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


    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.

  7. Sand fairway mapping as a tool for tectonic restoration in orogenic belts (United States)

    Butler, Rob


    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

  8. Formwork tectonics

    DEFF Research Database (Denmark)

    Manelius, Anne-Mette


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

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


    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

  10. Paleostress inversion of fault-slip data from the Jurassic to Cretaceous Huangshan Basin and implications for the tectonic evolution of southeastern China (United States)

    Xu, Xianbing; Tang, Shuai; Lin, Shoufa


    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.

  11. Structural and stratigraphic evolution of the central Mississippi Canyon area: Interaction of salt tectonics and slope processes in the formation of engineering and geologic hazards (United States)

    Brand, John Richard

    Approximately 720 square miles of digital 3-dimensional seismic data covering the eastern Mississippi Canyon area, Gulf of Mexico, continental shelf was used to examine the structural and stratigraphic evolution of the geology in the study area. The analysis focused on salt tectonics and sequence stratigraphy to develop a geologic model for the study area and its potential impact on engineering and geologic hazards. Salt in the study area was found to be established structural end-members derived from shallow-emplaced salt sheets. The transition from regional to local salt tectonics was identified through structural deformation of the stratigraphic section on the seismic data and occurred no later than ˜450,000 years ago. From ˜450,000 years to present, slope depositional processes have become the dominant geologic process in the study area. Six stratigraphic sequences (I-VI) were identified in the study area and found to correlate with sequences previously defined for the Eastern Mississippi Fan. Condensed sections were the key to the correlation. The sequence stratigraphy for the Eastern Mississippi Fan can be extended ˜28 miles west, adding another ˜720 square miles to the interpreted Fan. A previously defined channel within the Eastern Fan was identified in the study area and extended the channel ˜28 miles west. Previous work on the Eastern Fan identified the source of the Fan to be the Mobile River; however, extending the channel west suggests the sediment source to be from the Mississippi River, not the Mobile River. Further evidence for this was found in ponded turbidites whose source has been previously established as the Mississippi River. Ages of the stratigraphic sequences were compared to changes in eustatic sea level. The formation stratigraphic sequences appear decoupled from sea level change with "pseudo-highstands" forming condensed sections during pronounced Pleistocene sea level lowstands. Miocene and Pleistocene depositional analogues

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

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


    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

  13. 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


    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

  14. 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


    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

  15. 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


    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.

  16. 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)


    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.

  17. Insights into the Tectonic Evolution of the North American Cordilleran Hinterland from Detrital Zircon Double Dating of the Eocene Elko Formation (United States)

    Canada, A.; Cassel, E. J.; Smith, M. E.; Stockli, D. F.; Jicha, B. R.; Singer, B. S.


    The North American Cordilleran hinterland, from eastern Nevada to western Utah, is the product of Mesozoic crustal thickening and eventual orogen collapse. In NE Nevada, the Eocene Elko Formation represents ~10 Myr of high-elevation (up to 3.5 km) lacustrine deposition within a Paleogene orogenic plateau interior, prior to Neogene extensional collapse. Detrital zircon U-Pb and (U-Th)/He (ZHe) double dating from the Elko Formation constrains the timing and magnitude of tectonic-scale processes as well as the evolution of hinterland paleohydrology and magmatism. Eocene maximum depositional ages from detrital zircon are largely consistent with new single crystal sanidine 40Ar/39Ar ages for Elko Formation tuff beds. U-Pb-He double dating of Eocene sediments supports several phases of exhumation and surface uplift in the hinterland. ZHe ages, combined with U-Pb geochronology, clast assemblages, and paleocurrent analysis suggest a significant amount of detritus from the Roberts Mountain Allochthon (RMA) and back-arc plutons was transported to the Elko Basin during the middle Eocene. Detrital zircons sourced from the RMA record progressive unroofing and are characterized by Archean-Paleoproterozoic crystallization ages and Mesoproterozoic-Triassic cooling ages. The preponderance of Precambrian ZHe ages during the middle-late Eocene and the absence of reset ZHe ages throughout the basin imply that sediment burial did not exceed depths of >6 km during the Phanerozoic. Double dating of several grains from a sandstone below the base of the lacustrine section also confirms the presence of volcanic detritus derived from the Challis volcanic field of central Idaho 400 kilometers to the northeast. Lag time analysis permits discrimination of syndepositional volcanic grains from grains derived from rapidly exhumed sources. Lag time analysis (excluding volcanic grains) indicates that several source areas west of the Elko Basin have undergone major exhumation during the late Eocene.

  18. Mineral parageneses, regional architecture, and tectonic evolution of Franciscan metagraywackes, Cape Mendocino-Garberville-Covelo 30' x 60' quadrangles, northwest California (United States)

    Ernst, W.G.; McLaughlin, R.J.


    The Franciscan Complex is a classic subduction-zone assemblage. In northwest California, it comprises a stack of west vergent thrust sheets: westernmost Eastern Belt outliers; Central Belt mélange; Coastal Belt Yager terrane; Coastal Belt Coastal terrane; Coastal Belt King Range/False Cape terranes. We collected samples and determined P-T conditions of recrystallization for 88 medium-fine-grained metasandstones to assess their subduction-exhumation histories and assembly of the host allochthons. Feebly recrystallized Yager, Coastal, and King Range strata retain clear detrital features. Scattered neoblastic prehnite occurs in several Coastal terrane metasandstones; traces of possible pumpellyite are present in three Yager metaclastic rocks. Pumpellyite ± lawsonite ± aragonite-bearing Central Belt metasandstones are moderately deformed and reconstituted. Intensely contorted, thoroughly recrystallized Eastern Belt affinity quartzose metagraywackes contain lawsonite + jadeitic pyroxene ± aragonite ± glaucophane. We microprobed neoblastic phases in 23 rocks, documenting mineral parageneses that constrain the tectonic accretion and metamorphic P-T evolution of these sheets. Quasi-stable mineral assemblages typify Eastern Belt metasandstones, but mm-sized domains in the Central and Coastal belt rocks failed to achieve chemical equilibrium. Eastern Belt slabs rose from subduction depths approaching 25–30 km, whereas structurally lower Central Belt mélanges returned from ∼15–18 km. Coastal Belt assemblages suggest burial depths less than 5–8 km. Eastern and Central belt allochthons sequentially decoupled from the downgoing oceanic lithosphere and ascended into the accretionary margin; K-feldspar-rich Coastal Belt rocks were stranded along the continental edge without undergoing appreciable subduction, probably during Paleogene unroofing of the older, deeply subducted units of the Franciscan Complex in east-vergent crustal wedges.

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

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


    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

  20. Comment on "Intermittent plate tectonics?". (United States)

    Korenaga, Jun


    Silver and Behn (Reports, 4 January 2008, p. 85) proposed that intermittent plate tectonics may resolve a long-standing paradox in Earth's thermal evolution. However, their analysis misses one important term, which subsequently brings their main conclusion into question. In addition, the Phanerozoic eustasy record indicates that the claimed effect of intermittency is probably weak.

  1. Stress fields during the evolution of large-scale strike-slip systems and tectonic slivers, Atacama Fault Zone, northern Chile (United States)

    Veloso, E. E.; Gomila, R.


    Tectonic evolution of crustal slivers generated during oblique subduction involves a series of translations and rotations. Slivers are defined by large-scale strike-slip faults, whereas internal blocks are by the faulting pattern related to the fault system. Translations and rotations are then likely to accommodate the internal deformation caused by external forces. The Atacama Fault System (AFS), a crustal-scale strike-slip fault in northern Chile, can be divided into three concave, oceanward segments, that show sinestral (Mesozoic) and normal (Cenozoic) displacements. Clockwise rotations of ca. 50° have been suggested for the AFS, mostly for the northernmost segment. The Paposo segment defines a sliver of 160 km long and 25 km wide. In the northern part, it exhibits intense internal faulting, duplexes, single- and multiple-core faults. To determine the stress field responsible for the development and evolution of the sliver, we measured 162 brittle fault planes on which we determined the sense and direction of maximum shear. Fault planes show a main NW-SE trend and subvertical dip-angles (Fig. 1). Brittle kinematic indicators indicate subhorizontal (sinestral) and subvertical (normal) movements. Fault-slip data was processed with the multiple inverse method. Input parameters were k=5 (grouping), e=9 (enhance) and d=1 (dispersion). Calculations show that σ1 axes are distributed on a NW-SE trending great-circle whereas σ3 axes are clustered near the horizontal in NE and SW orientations. Stress ratios average 0.55±0.20. In the horizontal, σ1 axes cover an arc of about 30° and σ3 axes cover about 60° (Fig. 1), suggesting a strike-slip stress field. On the contrary, the subvertical cluster of σ1 axes suggests a normal stress field. These analyses indicate that the Paposo Sliver developed during a period of NW-SE compression and NE-SW tension. The wide distribution of the tensile axes may denote rotation of the internal blocks to accommodate the deformation or

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

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


    ??-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. 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 (United States)

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


    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.

  4. Alpine orogenic evolution from subduction to collisional thermal overprint: The 40Ar/39Ar age constraints from the Valaisan Ocean, central Alps

    DEFF Research Database (Denmark)

    Wiederkehr, Michael; Sudo, Masafumi; Bousquet, Romain;


    in general. The timing of high-pressure metamorphism, subsequent retrogression and following Barrow-type overprint was studied by 40Ar/39Ar dating of biotite and several white mica generations that are well characterized in terms of mineral chemistry, texture and associated mineral assemblages. Four distinct...... age populations of white mica record peak pressure conditions (42–40 Ma) and several stages of subsequent retrograde metamorphic evolution (36–25 Ma). Biotite isotopic analyses yield consistent apparent ages that cluster around 18–16 Ma for the Barrow-type thermal overprint. The recorded isotopic data...

  5. Deep Fault Drilling Project—Alpine Fault, New Zealand

    Directory of Open Access Journals (Sweden)

    Rupert Sutherland


    Full Text Available The Alpine Fault, South Island, New Zealand, constitutes a globally significant natural laboratory for research into how active plate-bounding continental faults work and, in particular, how rocks exposed at the surface today relate to deep-seated processes of tectonic deformation, seismogenesis, and mineralization. The along-strike homogeneity of the hanging wall, rapid rate of dextral-reverse slip on an inclined fault plane, and relatively shallow depths to mechanical and chemical transitions make the Alpine Fault and the broader South Island plate boundary an important international site for multi-disciplinary research and a realistic target for an ambitious long-term program of scientific drilling investigations.

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

    Lemasurier, W. E.


    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

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

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


    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

  8. The petrogenesis of sodic granites in the Niujuanzi area and constraints on the Paleozoic tectonic evolution of the Beishan region, NW China (United States)

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


    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

  9. 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


    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.

  10. 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 (United States)

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


    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.

  11. 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 (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.


    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

  12. 东非构造演化与油气成藏规律初探%Tectonic Evolution and Hydrocarbon Accumulation Principle in East Africa

    Institute of Scientific and Technical Information of China (English)

    金宠; 陈安清; 楼章华; 金爱民; 朱蓉; 陶丽; 徐胜林


    The opening up of the oil and gas resources of Africa provides opportunities to Chinese overseas oil strategy. Generally, the exploration level of oil and gas is low in East Africa, thus it's necessary to understand the hydrocarbon accumulation rules and its dominant controlling factors in order to effectively choose the hydrocarbon prospect area and explore in future. By analyzing tectonic evolution and conditions of hydrocarbon accumulation of various basins in East Africa, we conclude that the controlling factors of hydrocarbon accumulation in East Africa include salt sequence, drainage distribution, geothermal anomaly and hydrocarbon preserving conditions. The hydrocarbon accumulations in passive continental margin basins are mainly controlled by delta, submarine fan, salt sequence and mudstone seal, whereas, in rift basins are mainly controlled by the distribution of graben and horst, trap type and scale forming by rifting, the intensity and range of structure activity and mag-matism. The passive continental margin basins have hydrocarbon accumulation rules of Karoo Group producing gas, salt sequence distribution areas developing favorable play, land part of basins being poor conditions of oil and gas accumulation, large delta and submarine fan bearing considerable exploration potential. The rift basins have remarkable characteristics that the hydrocarbon migrates along a short distance to reservoirs, and hydrocarbon enriches in the horst margin which is close to trough hydrocarbon kitchen, and shows relatively weak struc-tare activity, magmatism and geothermal anomaly. In conclusion, the exploration potential of East African becomes better away from Afar plume.%随着非洲油气资源对外开放程度的加大,给我国海外石油战略提供了机遇.东非低勘探程度区油气地质资料匮乏,其油气勘探潜力综合评价和预测是目前的一个重点与难点,又是我国海外油气资源战略选区的需要.根据东非的区域构造演

  13. Intermittent plate tectonics? (United States)

    Silver, Paul G; Behn, Mark D


    Although it is commonly assumed that subduction has operated continuously on Earth without interruption, subduction zones are routinely terminated by ocean closure and supercontinent assembly. Under certain circumstances, this could lead to a dramatic loss of subduction, globally. Closure of a Pacific-type basin, for example, would eliminate most subduction, unless this loss were compensated for by comparable subduction initiation elsewhere. Given the evidence for Pacific-type closure in Earth's past, the absence of a direct mechanism for termination/initiation compensation, and recent data supporting a minimum in subduction flux in the Mesoproterozoic, we hypothesize that dramatic reductions or temporary cessations of subduction have occurred in Earth's history. Such deviations in the continuity of plate tectonics have important consequences for Earth's thermal and continental evolution.

  14. Tectonic microplates: laying it down on wax (United States)

    Katz, R. R.; Bodenschatz, E.


    We present a wax analogue model of sea-floor spreading that produces rotating, growing microplates. Wax microplates are kinematically similar to sea-floor tectonic microplates in terms of spreading rate and growth rate. Furthermore, their spiral pseudofault geometry is quantitatively consistent with Schouten's oceanic microplate model. These results suggest that Schouten's edge-driven microplate model captures the kinematics of tectonic microplate evolution on Earth. We propose a theory for the formation of microplates.

  15. The large-wavelength deformations of the lithosphere: materials for a history of the evolution of thought from the earliest times to plate tectonics

    Institute of Scientific and Technical Information of China (English)

    A.M.C.Sengor; DavidOldroyd


    The notable authority on tectonics and the history of geosciences, Professor Celal Sengor from Istanbul, has produced another remarkable book-which, as he tells the reader, grew rapidly from an initial paper into a massive tome. Just as Georges Cuvier liked the idea of ‘bursting the limits of time', so Professor Sengor has again ‘burst the limits of a paper'!

  16. Plate-tectonic evolution of the deep ocean basins adjoining the western continental margin of India - A proposed model for the early opening scenario

    Digital Repository Service at National Institute of Oceanography (India)

    Bhattacharya, G.C.; Yatheesh, V.

    of oceanic crust formed at an abandoned oceanic spreading centre. They (ibid.) however candidly admitted that the debate on the crustal nature of the Laxmi Ridge would still remain owing to the non-uniqueness of geophysical analyses. In our opinion... gradually around chron C21ny (~ 46.3 Ma). Propagation direction during this last stage was systematically towards west along all the spreading ridge segments. The crust generated during each of these propagation stages is delimited by unique tectonic...

  17. Plate tectonics, damage and inheritance. (United States)

    Bercovici, David; Ricard, Yanick


    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.

  18. Plate tectonics, damage and inheritance. (United States)

    Bercovici, David; Ricard, Yanick


    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

  19. Coupling dynamic mechanisms between plate tectonics evolution and mantle convection of south and north Tianshan%天山南北地块构造演化与地幔对流耦合动力机制

    Institute of Scientific and Technical Information of China (English)

    刘玉虎; 刘兴旺; 郑建京; 赵丹丹; 杨鑫; 王亚东


    天山造山带南北分别于塔里木盆地和准噶尔盆地相接,经历古生代时期超级大陆裂解、南北天山洋裂开、洋盆持续扩张、洋壳俯冲消减、陆陆碰撞缝合过程及中新生代陆内再造山构造调整,是现今世界上较为活跃的陆内造山带,成为国内外大陆动力学研究的热点地带.在综合分析地质学、地球物理(地震剖面、重力异常、地震层析)、地球化学、岩石学及天文学等资料基础上,结合天山造山带大地构造演化历史、地表构造变形、盆地基底构造样式,以及对5种地幔对流模式的深入探究,基于全地幔对流和上地幔小尺度对流模式,提出天山地区板块构造演化与地幔对流的耦合动力机制,总体呈现为“启动-同步-超越-消减”模式,中间过程则伴随微观振荡旋回动力模式向前发展,该模式可与经典威尔逊旋回比较,同时现今地球深部板决演化痕迹及地幔对流数值模拟一定程度上支持了该模式.总之,将板块构造演化历史与地幔对流结合起来、纳入统一的动力学模型中,对于今后研究地球各子系统之间的耦合状态、相互作用有十分重要的意义.%Tianshan orogenic belt connects with the Tarim basin and Junggar basin from south to north respectively. Through a joint Paleozoic continental breakup, the South Tianshan Ocean and the North Tianshan ocean cracked, the continued expansion of ocean basins, oceanic crust subduction, continental collision and suture and Cenozoic tectonic adjustments, now it is the world's more active orogenic belt and become a domestic hot zone of continental dynamics. Based on comprehensive analysis of geological, geophysical ( seismic profiles, gravity anomalies, seismic tomography), geochemical, petrological, and astronomy, etc. , combined with the tectonic evolution history of the Tianshan orogenic belt, the surface structural deformation, base tectonic style of the basin, and the deeply

  20. Transient thermal effects in Alpine permafrost

    Directory of Open Access Journals (Sweden)

    J. Noetzli


    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.

  1. Les barrages alpins

    Directory of Open Access Journals (Sweden)

    Alain Marnezy


    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.

  2. Tectonics of montage

    DEFF Research Database (Denmark)

    Bundgaard, Charlotte


    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....

  3. Evolution of the North China Craton and Early Plate Tectonics%华北克拉通的形成以及早期板块构造

    Institute of Scientific and Technical Information of China (English)



    The oldset rock discovered on the Earth is the TTG gneiss but whether there was oldest oceanic crust and how continental crust formed deal with all aspects of continental dynamics. Among them is when the plate tectonics started , "which has been a front scientific question for decades. The popular answer is from Neoproterozoic, others suggest Paleoproterozoic or Neoarchean, or even some believe the plate tectonics started from the occurrence of water. In various marks identifying the plate tectonics, ophiolite and high-pressure metamorphic belt are no doubt the most important issues. The former implies that the old oceanic crust slab was involved in orogenic belt, and the latter probably indicates that supracrustal rock unit was subducted under deep crust or mantle and can be lithological evidence of subduction, denudation and collision. Based on the discussion and comparison between Archean greenstone belt and ophiolite and between UH-HP/UT-UHT granulites and Phanerozoic HP metamorphic belt, authors come to a primitive conclusion that these two can not be used as the convincing evidence to support plate tectonics. The paper also discussed Archean continental formation and rift-subdution-collision tectonic process of Paleoproterozoic mobile belts of the NCC. It is proposed that the Neoarchean tectonic pattern of greenstone belt-high grade region in the NCC probably indicates a dominant heat tectonic regime (mantle plume) with limited transverse movement. The micro-blocks were welded by greenstone belts, followed by metamorphism and granitization, completing craton process of stable continent. The tectonic regime is likely controlled by frequent moderate-scale mantle plumbs, accompanied by small-scale horizontal tectonic movement. The Paleoproterozoic supracrustal rocks in the NCC occur as a linear mobile belt with middle-grade metamorphism, multi-stage deformation, intruded by nearly synchronous or little later granitic intrusion and associated by Cu

  4. Digital Tectonic Tools

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due


    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...


    Institute of Scientific and Technical Information of China (English)



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


    Institute of Scientific and Technical Information of China (English)


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

  7. Tectonic division and regional tectonic evolution of West Tianshan organic belt%西天山造山带构造单元划分与构造演化

    Institute of Scientific and Technical Information of China (English)

    朱志新; 董连慧; 王克卓; 赵同阳; 徐仕琪; 陈邦学; 李平; 靳留圆


    Located in the southern part of Central Asia, the West Tianshan organic belt lies at the juncture between the Kazakhstan-Junggar ancient plate and the Tarim ancient plate and is composed of Paleozoic epicontinental rock series, oceanic crust relicts and Precambrian microlandmass. Its structural evolution process is a miniature of the evolution of the Northern Xinjiang paleo-Asiatic Ocea. It experienced the formation of continental nucleus in Archean-early Proterozoic period, the evolution of Ancient Tianshan oceanic basin in late Proterozoic period, and the generation of a unified Xinjiang part of Gondwana in late Proterozoic period. In late Proterozoic period, Tianshan region, as a part of the paleo-Asiatic Ocean, began cracking; in Cambrian period this region entered the peak stage of expansion; in Ordovician-Carboniferous period, the ancient subduction zone was formed, and the ancient ocean basin was continually contracted; in Late Carboniferous period, the Tianshan ancient ocean basin was closed, with the formation of an unified continental crust; in Middle Cenozoic period, the region entered into the intracontinental evolution stage.%西天山造山带位于北亚造山区的南部,为哈萨克斯坦-准噶尔古板块与塔里木古板块的交会处,由古生代陆缘岩系、洋壳残片和前寒武纪微陆块等拼贴增生而成,其构造演化过程成为新疆北部的古亚洲洋演化的缩影.经历了太古代至早元古代的古陆核形成、中—晚元古代古天山洋盆的演化,至晚元古代形成统一的新疆古陆的一部分.晚元古代天山地区作为古亚洲洋的一部分开始裂解,至寒武纪进入扩张的高峰,奥陶纪—石炭纪古俯冲带形成,古洋盆持续收缩,晚石炭世天山古洋盆关闭,统一大陆地壳形成,中新生代进入陆内演化阶段.

  8. Design of alpine skis (United States)

    Nordt, Alison Audrey

    Models were developed to calculate the mechanical properties and the turning characteristics of alpine skis. The skis considered are constructed of layers of materials which may include wood, foam, metal, plastics, and fiber reinforced composites. The ski may be manufactured with or without camber and sidecut. The first model, and the corresponding SKI-MECH computer code, yields the mass, the bending and torsional stiffness distributions along the length, the flex, the twist, the natural frequencies, and the pressure distribution along the base of the ski. The second model, and the corresponding SKI-TURN code, simulates the motion of a skier of given height, weight, and skill level going down a smooth slope while executing a constant radius turn. The computer code provides the time it requires the skier to complete the turn. Both the SKI-MECH and SKI-TURN codes were verified by comparing the outputs of these codes to laboratory data and to data generated by skiers executing turns on a hill. The results of the model and the data are in good agreement lending confidence to the models and the computer codes. Numerical results are also presented which illustrate the usefulness of the computer codes for assessing the performance of skis and shed light on the role sidecut plays in affecting an efficient turn.

  9. 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 (United States)

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


    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.

  10. 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 (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


    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.

  11. 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


    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.

  12. Recent advances on the tectonic and magmatic evolution of the Greater Tibetan Plateau: A special issue in honor of Prof. Guitang Pan (United States)

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


    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.

  13. Geochemistry of the Neoproterozoic (800-767 Ma) Cerro Bori orthogneisses, Dom Feliciano Belt in Uruguay: tectonic evolution of an ancient continental arc (United States)

    Lenz, C.; Porcher, C. C.; Fernandes, L. A. D.; Masquelin, H.; Koester, E.; Conceição, R. V.


    The Cerro Bori orthogneisses, crystallized between ca. 800 and 767 Ma, are composed of a sequence of mafic gneisses, with dioritic-gabbroic and dioritic composition tectonically interleaved with a sequence of tonalitic and granodioritic gneisses. These rocks intruded the Chafalote paragneisses (metapelites, semipelites, carbonate and mafic rocks) and they were metamorphosed of high P-T conditions at ca. 676-654 Ma. This paper presents the first major and trace geochemical signatures, as well as Sm and Pb isotopic composition for the Cerro Bori orthogneisses, which allow distinguishing three different groups of rocks. Type I rocks are mafic gneisses with tholeiitic affinity, whereas the Type II rocks are tonalitic and granodioritic gneisses with calc-alkaline affinity. The third type is composed of biotite-rich mafic gneisses with potassic and ultrapotassic affinities. All the three types of rocks have negative ℰND values (between -2.12 and -6.67) and old TDM ages (between 1.2 and 2.0 Ga), indicating that the process of crustal assimilation/contamination was an important process, together with fractional crystallization. An continental arc tectonic setting is suggested to this association of rocks between 800 and 767 Ma. This subduction suggests the existence of an ocean between Rio de La Plata and adjacent cratons during the break up of the Rodinia supercontinent.

  14. Oligocene tectonics and sedimentation, California (United States)

    Nilsen, T.H.


    During the Oligocene epoch, California was marked by extensive nonmarine sedimentation, in contrast to its pre-Oligocene and post-Oligocene depositional history. The Oligocene continental deposits are especially widespread in southern California and fill a number of small and generally partly restricted basins. Fluvial facies in many basins prograded over previously deposited lower Tertiary turbidites. Volcanism, from widespread centers, was associated with the nonmarine sedimentation. However, some basins remained marine and a few contain Oligocene turbidites and pelagic sediments deposited at bathyal depths. The Oligocene redbeds of California do not form a post-orogenic molasse sequence comparable to the Old Red Sandstone or Alpine molasse. They are synorogenic and record local uplift of basins and surrounding source areas. Late Cretaceous to contemporary orogenesis in California has been generally characterized by the formation of small restricted basins of variable depth adjacent to small upland areas in response to strike-slip faulting. Deposition of Oligocene redbeds was associated with climatic change from warm and humid to cold and semiarid, and a global lowering of sea level. Oligocene tectonism occurred during the transition from subduction of the Farallon Plate to initiation of the modern San Andreas transform system. However, the major influence that caused uplift, formation of fault-bounded basins, and extensive redbed deposition, especially in southern California, was the approach of the Pacific-Farallon spreading ridge to the western margin of California. ?? 1984.

  15. 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.)

  16. Unraveling tectonics and climate forcing in the late-Neogene exhumation history of South Alaska (United States)

    Valla, Pierre; Champagnac, Jean-Daniel; Shuster, David; Herman, Frédéric; Giuditta Fellin, Maria


    The southern Alaska range presents an ideal setting to study the complex interactions between tectonics, climate and surface processes in landscape evolution. It exhibits active tectonics with the ongoing subduction/collision between Pacific and North America, and major active seismogenic reverse and strike-slip faults. The alpine landscape, rugged topography and the important ice-coverage at present reveal a strong glacial imprint associated with high erosion and sediment transport rates. Therefore, the relative importance of climatically-driven glacial erosion and tectonics for the observed late-exhumation history appears to be quite complex to decipher. Here, we first perform a formal inversion of an extensive bedrock thermochronological dataset from the literature to quantify the large-scale 20-Myr exhumation history over the entire southern Alaska. We show that almost half of the variability within the thermochronological record can be explained by modern annual precipitations spatial distribution, the residuals clearly evidencing localized exhumation along major tectonic structures of the frontal fold and thrust belt. Our results confirm high exhumation rates in the St Elias "syntaxis" and frontal zones for the last 0-2 Myr, where major ice fields and high precipitation rates likely sustained high exhumation rates; however the impact of late Cenozoic glaciations is difficult to constrain because of the low resolution on the exhumation history older than ~2 Myr. On the contrary, our inversion outcomes highlight that north of the Bagley Icefield the long-term exhumation has remained quite slow and continuous over the last ~20 Myr, with no late-stage signal of exhumation change since the onset of glaciations despite a clear glacial imprint on the landscape. We thus focus on the Granite Range (Wrangell-St Elias National Park, Alaska), an area presenting a strong glacial imprint but minor tectonic activity with only localized brittle deformation. We sampled four

  17. 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

  18. Depositional architecture and evolution of inner shelf to shelf edge delta systems since the Late Oliocene and their respone to the tectonic and sea level change, Pear River Mouth Basin, northern South China Sea (United States)

    Lin, Changsong; Zhang, Zhongtao; liu, Jingyan; Jiang, Jing


    The Pear River Mouth Basin is located in the northern continent margin of the South China Sea. Since the Late Oligocene, the long-term active fluvial systems (Paleo-Zhujiang) from the western basin margin bebouched into the northern continental margin of the South China Sea and formed widespread deltaic deposits in various depositional geomorphologies and tectonic settings. Based of integral analysys of abundant seismic, well logging and drilling core data, Depositional architecture and evolution of these delta systems and their respone to the tectonic and sea level change are documented in the study. There are two basic types of the delta systems which have been recognized: inner shelf delta deposited in shallow water enviroments and the outer shelf or shelf-edge delta systems occurred in deep water settings. The paleowater depths of these delta systems are around 30 to 80m (inner shelf delta) and 400-1000m (shelf-edge delta) estimated from the thickness (decompaction) of the delta front sequences. The study shows that the inner shelf delta systems are characterized by relatively thin delta forests (20-40m), numereous stacked distributary channel fills, relative coarse river mouth bar deposits and thin distal delta front or distal bar and prodelta deposits. In contrast, the outer shelf or shelf edge delta systems are characteristic of thick (300-800m) and steep (4-60) of deltaic clinoforms, which commonly display in 3D seismic profiles as "S" shape reflection. Large scale soft-sediment deformation structures, slump or debris flow deposits consisting mainly of soft-sediment deformed beds, blocks of sandstones and siltstones or mudstones widely developed in the delta front deposits. The shelf edge delta systems are typically associated with sandy turbidite fan deposits along the prodelta slopes, which may shift basinwards as the progradation of the delta systems. The delta systems underwent several regional cycles of evolution from inner shelf deltas to shelf edge

  19. Plate tectonics and planetary habitability: current status and future challenges. (United States)

    Korenaga, Jun


    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

  20. Plate tectonics and planetary habitability: current status and future challenges. (United States)

    Korenaga, Jun


    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.

  1. Late Mesozoic to Paleogene stratigraphy of the Salar de Atacama Basin, Antofagasta, Northern Chile: Implications for the tectonic evolution of the Central Andes (United States)

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


    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

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

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


    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

  3. Geodynamical evolution of the Southern Carpathians: inferences from computational models of lithospheric gravitational instability (United States)

    Lorinczi, Piroska; Houseman, Gregory


    The Carpathians are a geologically young mountain chain which, together with the Alps and the Dinarides, surround the extensional Pannonian and Transylvanian basins of Central Europe. The tectonic evolution of the Alpine-Carpathian-Pannonian system was controlled by convergence between the Adriatic and European plates, by the extensional collapse of thickened Alpine crust and by the retreat of the Eastern Carpathians driven by either a brief episode of subduction or by gravitational instability of the continental lithospheric mantle. The Southeast corner of the Carpathians has been widely studied due to its strong seismic activity. The distribution and rate of moment release of this seismic activity provides convincing evidence of a mantle drip produced by gravitational instability of the lithospheric mantle developing beneath the Vrancea region now. The question of why gravitational instability is strongly evident beneath Vrancea and not elsewhere beneath the Southern Carpathians is unresolved. Geological and geophysical interpretations of the Southern Carpathians emphasise the transcurrent deformation that has dominated recent tectonic evolution of this mountain belt. We use computational models of gravitational instability in order to address the question of why the instability appears to have developed strongly only at the eastern end of this mountain chain. We use a parallelised 3D Lagrangean-frame finite deformation algorithm, which solves the equations of momentum and mass conservation in an incompressible viscous fluid, assuming a non-linear power-law that relates deviatoric stress and strain-rate. We consider a gravitationally unstable system, with a dense mantle lithosphere overlying a less dense asthenosphere, subject to boundary conditions which simulate the combination of shear and convergence that are thought to have governed the evolution of the South Carpathians. This program (OREGANO) allows 3D viscous flow fields to be computed for spatially

  4. La recherche alpine aujourd’hui

    Directory of Open Access Journals (Sweden)

    Jean-Jacques Brun


    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

  5. 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)


    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.

  6. 华北克拉通中部沁水盆地热演化史与山西高原中新生代岩石圈构造演化%Thermal Evolution History of Qinshui Basin in the Middle of North China Cratonand Mesozoic-Cenozoic Lithosphere Tectonic Evolution in Shanxi Plateau

    Institute of Scientific and Technical Information of China (English)

    孟元库; 汪新文; 李波; 蔡志东


    Based on the geological data of Qincan No.1 well,combined with the sedimentary structural evolution and its contrast with neighboring areas,the paper systematically studied the regional tectonic movement and tectonic evolution of Qinshui basinsince the late Paleozoic by apa-tite fission track analysis as well asstudies on aspects including zircon fission track,minerals fluid inclusions,organic matter vitrinite reflectance,regional magmatic activity and basin structural e-volution.On this basis,the Mesozoic-Cenozoic lithosphere tectonic evolution and plateau uplift thermal process in Shanxi plateau was discussed,and the geological evaluation of Qinshuibasin-was improved,which laida solid the oretical foundation for further studies of ancient geothermal history in Qinshui basin of North China Craton and its adjacent areas.%以沁参1井地质资料为基础,结合沉积构造演化及邻区对比等,以磷灰石裂变径迹分析为主要手段,配合锆石裂变径迹、矿物流体包裹体、有机质镜质体反射率、区域岩浆活动及盆地演化分析,较系统地研究了沁水盆地晚古生代以来的区域构造运动与构造演化。并以此为基础探讨了山西高原中—新生代岩石圈构造热演化与高原的隆升过程,提高了对沁水盆地的地质评价,为下一步研究华北克拉通东部沁水盆地及邻区的古地热演化历史奠定了基础。

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


    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

  8. 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

  9. 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 (United States)

    Tani, Makoto


    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

  10. Alpine Skiing in the Classroom (United States)

    Mendez-Gimenez, Antonio; Fernandez-Rio, Javier


    Many students settle indoors in the winter. However, this does not mean that winter should be a period of time with no physical activity. Several snow activities could be practiced during those months, such as ice-skating, ice-hockey, snowshoeing, cross-country skiing, alpine skiing, or snowboarding. In order to counteract the tendency for…

  11. Geomorphology, tectonics, and exploration (United States)

    Sabins, F. F., Jr.


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

  12. Seismic Imaging at Whataroa Valley (New Zealand) for the Deep-Fault-Drilling-Project Alpine Fault (United States)

    Lay, V.; Buske, S.; Kovacs, A.; Gorman, A. R.


    The Alpine Fault in New Zealand (South Island) is one of the largest active plate-bounding continental fault zones on Earth with earthquakes of magnitude 7.9 occuring every 200-400 years. Due to the surface exposure and the shallow depth of mechanical and chemical transitions it is a globally significant natural laboratory. Within the ICDP Deep-Fault-Drilling-Project Alpine Fault (DFDP-AF; a drill hole shall give insight into the geological structure of the fault zone and its evolution to understand the related deformation and earthquake processes. With the help of advanced seismic imaging techniques the shallow structure of the Alpine Fault is imaged to find the most suitable drill site location. A new seismic reflection profile has been acquired in 2011 by the WhataDUSIE project team consisting of partners from the University of Otago (New Zealand), TU Bergakademie Freiberg (Germany) and the University of Alberta (Canada). The reflection profile, located in the Whataroa river valley, has a total length of about 5 km. Up to 643 geophones with spacings between 4-8 m recorded the approximately 100 shots along the profile line. Single shot gathers as well as imaging results will be presented. The obtained data quality was in general very good. Nevertheless, extensive preprocessing of the data had to be performed to obtain shot gathers usable for imaging. Due to the field conditions the profile was divided into 5 parts with different features concerning geophone spacing and eigenfrequency of the geophones. To combine the single stations to one shot gather, we used overlapping geophones to derive the relative time corrections by crosscorrelating these particular traces. Additionally three Reftek 130 stations were recording continuously. By correlating the absolute Reftek time and the adjacent geophone trace we extracted the absolute shot time and applied the resulting time-shift to the corresponding traces. Finally the merged single shot

  13. 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)


    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)

  14. Crustal thickness controlled by plate tectonics

    DEFF Research Database (Denmark)

    Artemieva, Irina M.; Meissner, Rolf


    /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...

  15. Episodic plate tectonics on Venus (United States)

    Turcotte, Donald


    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.

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

    NARCIS (Netherlands)

    Schellart, W.P.; Spakman, W.


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

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


    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

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

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


    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.

  19. 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 (United States)

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


    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.


    Directory of Open Access Journals (Sweden)

    Tatiana Yu. Tveretinova


    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

  1. Investigation phytochimique de plantes alpines


    Munari, Caroline


    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...

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

    Kolodyazhnyi, S. Yu.


    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.

  3. The Voest-Alpine surface miner

    Energy Technology Data Exchange (ETDEWEB)


    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.

  4. 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 (United States)

    Cunningham, W. D.


    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

  5. Experimental Study of Transient Thermal Convection Following a Catastrophic Lithospheric Overturn: Applications to the Tectonic Style, Thermal Evolution and Topography of Venus (United States)

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


    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

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

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


    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

  7. Plate tectonics, habitability and life (United States)

    Spohn, Tilman; Breuer, Doris


    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

  8. 东海盆地形成的区域地质背景与构造演化特征%Regional Background and Tectonic Evolution of East China Sea Basin

    Institute of Scientific and Technical Information of China (English)

    赵志刚; 王鹏; 祁鹏; 郭瑞


    东海盆地处于西太平洋俯冲带前缘,是发育在华南克拉通基底之上的,以晚白垩世-新生代沉积为主的新生代盆地。东海盆地性质是在活动大陆边缘减薄陆壳之上的,由于洋-陆俯冲消减所引起的张裂、拉伸作用而形成的弧后裂谷型盆地,是西太平洋众多“沟-弧-盆”体系的一部分。东海盆地陆架外缘隆起控制着东海盆地的演化过程,该地质单元形成于晚白垩世,是陆缘隆起和增生楔的复合体,中新世后由于菲律宾海板块的活动而解体为现今的钓鱼岛隆褶带和琉球隆起。结合对陆架外缘隆起的研究后认为,东海盆地晚白垩世以来的演化历程具有3大构造阶段,即:第一阶段,古新世-中始新世西部坳陷形成发展期;第二阶段,中始新世-渐新世东部坳陷形成发展期,其中,中晚始新世太平洋板块的转向是东、西部坳陷构造迁移的分界点;第三阶段,中新世-全新世,东海盆地进入到菲律宾板块影响时期,原先的构造格局开始分解。%The East China Sea Basin that located in the front of the west Pacific subduction zone,is formed upon the Huanan Craton basement.The main sediment filling are from Late Cretaceous to Cenozoic.The East China Sea Basin developed on the thinned continental margin crust,is a back-arc rift basin caused by rifting and stretching that induced by ocean subduction, which is the part of the “trench-arc-basin”system in the west Pacific.The tectonic evolution was controlled by the uplift in the outer continental shelf that formed in the Late Cretaceous.The uplift is the complex of the continental margin uplift and accre-tionary wedge that disintegrated into Diaoyu Island fold belt and Ryukyu uplift after Miocene.Considering the study of the out-er continental shelf uplift,tectonic evolution history of the East China Sea basin after Late Cretaceous can be divided into three stages

  9. Tectonic Vocabulary & Materialization

    DEFF Research Database (Denmark)

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


    By referring to the fundamental question of how we unite aesthetics and technology – tectonic theory is necessarily a focal point in the development of the architectural discipline. However, a critical reconsideration of the role of tectonic theory seems necessary when facing the present everyday...... architectural practice. In this matter the paper focuses on the need to juxtapose theoretical studies, to bring the present vocabulary of the tectonic further, as well as to spur further practical experiments enabling theory to materialize in the everyday of the current practice....

  10. Alpine thermal events in the central Serbo-Macedonian Massif (southeastern Serbia) (United States)

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


    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.

  11. 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

  12. Sandstone provenance and tectonic evolution of the Xiukang Mélange from Neotethyan subduction to India-Asia collision (Yarlung-Zangbo suture, south Tibet) (United States)

    An, Wei; Hu, Xiumian; Garzanti, Eduardo


    -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.

  13. Rheology and deep tectonics

    Directory of Open Access Journals (Sweden)

    G. Ranalli


    Full Text Available The distribution of the rheological properties of the lithosphere in space, and their variations in time, have a profound effect on the resulting tectonic deformation. A classical way of estimating these properties makes use of rheological profiles (strength envelopes. Although rheological profiles are based on assumptions and approximations which limit their resolving power, they are an efficient first-order tool for the study of lithosphere rheology, and their application clarifies the dynamics of tectonic processes. Two examples of the interaction of rheology and tectonics are discussed, namely, the post-orogenic relaxation of Moho topography (which is an additional factor to be considered in tectonic inversion, and the strength control on the level of necking in extension (which may lead to apparent local isostasy at passive continental margins and in sedimentary basins.

  14. Plate tectonics: Metamorphic myth (United States)

    Korenaga, Jun


    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.

  15. Tectonic Plate Movement. (United States)

    Landalf, Helen


    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)

  16. Plate tectonics on Venus


    Anderson, Don L.


    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.

  17. Plate tectonics on Venus (United States)

    Anderson, D. L.


    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.

  18. Modelling "reality" in tectonics: Simulation of the mechanical evolution of the Jura Mountains-Molasse Basin system, and routes to forward-inverse modelling of fold thrust belts. (United States)

    Hindle, David; Kley, Jonas


    The ultimate validation of any numerical model of any geological process comes when it can accurately forward model a case study from the geological record. However, as the example of the Jura-Molasse fold thrust belt demonstrates, geological information on even the most basic aspects of the present day state of such systems is highly incomplete and usually known only with large uncertainties. Fold thrust-belts are studied and understood by geologists in an iterative process of constructing their subsurface geometries and structures (folds, faults, bedding etc) based on limited subsurface information from boreholes, tunnels or seismic data where available, and surface information on outcrops of different layers and their dips. This data is usually processed through geometric models which involve conservation of line length of different beds over the length of an entire cross section. Constructing such sections is the art of cross section balancing. A balanced cross section can be easily restored to its pre-deformation state, assuming (usually) originally horizontal bedding to remove the effects of folding and faulting. Such a pre-deformation state can then form an initial condition for a forward mechanical model of the section. A mechanical model introduces new parameters into the system such as rock elasticity, cohesion, and frictional properties. However, a forward mechanical model can also potentially show the continuous evolution of a fold thrust belt, including dynamic quantities like stress. Moreover, a forward mechanical model, if correct in most aspects, should match in its final state, the present day geological cross section it is simulating. However, when attempting to achieve a match between geometric and mechanical models, it becomes clear that many more aspects of the geodynamic history of a fold thrust belt have to be taken into account. Erosion of the uppermost layers of an evolving thrust belt is the most obvious one of these. This can potentially

  19. Lithostratigraphy and tectonics of the eastern part of Veporské vrchy Mts. (Western Carpathians

    Directory of Open Access Journals (Sweden)

    Vojtko Rastislav


    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.

  20. Ediacaran Palaeozoic tectonic evolution of the Ossa Morena and Central Iberian zones (SW Iberia) as revealed by Sm Nd isotope systematics (United States)

    López-Guijarro, Rafael; Armendáriz, Maider; Quesada, Cecilio; Fernández-Suárez, Javier; Murphy, J. Brendan; Pin, Christian; Bellido, Felix


    Sm-Nd isotopic analyses of Palaeozoic sedimentary and igneous rocks in the southwest Iberian Massif (western end of the European Variscan Belt) are presented in order to unravel its complex poly-orogenic evolution during the closure of the Rheic Ocean and the amalgamation of Pangea. The Gondwanan margin in southwest Iberia SW Iberia is subdivided into the Ossa Morena and Central Iberian zones, separated by the Badajoz-Córdoba Shear Zone which represents a cryptic suture zone between these terranes. The relationships between these terranes, and between units preserved within the suture zone (e.g. the Sierra Albarrana Group) during the Palaeozoic and Neoproterozoic are controversial. Sm-Nd isotopic studies of representative sedimentary sequences covering the entire pre-Variscan record of the Ossa Morena and Central Iberian zones show very similar characteristics from the uppermost Ediacaran onwards. These data indicate that their accretion to one another must have been completed by the Late Neoproterozoic-Ediacarin that time (an event assigned to Cadomian orogeny) and that they never separated substantially from each other since that time. The Sm-Nd isotopic composition of the Sierra Albarrana Group metasedimentary rocks is similar to that of the pre-Cadomian sequences of the Ossa Morena Zone (Serie Negra), suggesting derivation from a common source. The common provenance of the Palaeozoic sequences in the two zones is identical to that of the pre-Cadomian Serie Negra of the Ossa Morena Zone, which in accordance with the data presented herein and published U-Pb zircon data indicates a West African affinity.

  1. Inevitability of Plate Tectonics on Super-Earths

    CERN Document Server

    Valencia, Diana; Sasselov, Dimitar D


    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.

  2. Palaeoproterozoic tectonic evolution of the Alto Tererê Group, southernmost Amazonian Craton, based on field mapping, zircon dating and rock geochemistry (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.


    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

  3. Alpine cloud climatology: regional effects (United States)

    Kaestner, Martina; Kriebel, Karl T.


    The present understanding of moist atmospheric processes and the role of clouds in the hydrologic cycle shows severe gaps of knowledge. Water vapor plays an essential part in atmospheric dynamics. For example, the release of large amounts of latent heat, due to the condensation in convective clouds, plays an important role in the general circulation. Knowledge of the distribution of clouds and its transport is essential to understand atmospheric dynamics. Clouds can have a positive as well as a negative contribution to the greenhouse effect. A cloud cover climatology in a 15 km grid resolution has been retrieved by means of the APOLLO algorithm using the 5 calibrated AVHRR channels. The monthly means of total cloud cover are about 15 percent too high compared to conventional data, the standard deviation is +/- 12 percent. The high resolution cloud cover maps show topometeorological features like 'Fohn' on single days but not in monthly means, because these events are too rare. But increased cloud cover in the luff regions are detected in monthly means as well as some cloud sparse regions like Lake Garda, Ticino or the Swiss Rhone valley. The different annual cycles of cloud cover show the different climatic regions, which are temperate, Alpine, and Mediterranean climate. This is indicated, for example, by the remarkably smaller cloud cover in the Alpine region in winter as compared to the northern and southern forelands.

  4. Strain weakening enables continental plate tectonics


    Gueydan, Frédéric; Précigout, Jacques; Montesi, Laurent G.J.


    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...

  5. Changes in the Alpine environment

    Directory of Open Access Journals (Sweden)

    Philippe Schoeneich


    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

  6. 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

  7. 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 (United States)

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


    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.

  8. On volcanism and thermal tectonics on one-plate planets (United States)

    Solomon, S. C.


    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.

  9. Inevitability of Plate Tectonics on Super-Earths


    Valencia, Diana; O'Connell, Richard J.; Sasselov, Dimitar D.


    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...

  10. 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


      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.

  11. 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 (United States)

    Rao, Zhiguo; Jia, Guodong; Li, Yunxia; Chen, Jianhui; Xu, Qinghai; Chen, Fahu


    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.

  12. 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. (United States)

    Herkat, Missoum; Delfaud, Jean


    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.

  13. Plate Tectonics on Earth and on Alien Worlds - Novel Insights into Mantle Dynamics (United States)

    Stamenkovic, V.; Breuer, D.; Seager, S.


    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.

  14. Task 1 quarternary tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Bell, J.W.


    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. The Plate Tectonics Project (United States)

    Hein, Annamae J.


    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…

  16. Tectonic vision in architecture

    DEFF Research Database (Denmark)

    Beim, Anne


    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...

  17. Experience with the Alpine Breaker Line Support

    Energy Technology Data Exchange (ETDEWEB)

    Habnicht, H.; Halbmayer, C.


    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.

  18. Emplacement ages, geochemical and Sr-Nd-Hf isotopic characterization of Mesozoic to early Cenozoic granitoids of the Sikhote-Alin Orogenic Belt, Russian Far East: Crustal growth and regional tectonic evolution (United States)

    Jahn, Bor-ming; Valui, Galina; Kruk, Nikolai; Gonevchuk, V.; Usuki, Masako; Wu, Jeremy T. J.


    The Sikhote-Alin Range of the Russian Far East is an important accretionary orogen of the Western Pacific Orogenic Belt. In order to study the formation and tectonic evolution of the orogen, we performed zircon U-Pb dating, as well as geochemical and Sr-Nd-Hf isotopic analyses on 24 granitoid samples from various massifs in the Primorye and Khabarovsk regions. The zircon dating revealed that the granitoids were emplaced from 131 to 56 Ma (Cretaceous to Paleogene). In the Primorye Region, granitoids in the coastal Sikhote-Alin intruded the Cretaceous Taukha Accretionary Terrane from ca. 90 to 56 Ma, whereas those along the Central Sikhote-Alin Fault zone intruded the Jurassic Samarka Accretionary Terrane during ca. 110-75 Ma. The "oldest" monzogranite (131 Ma) was emplaced in the Lermontovka area of the NW Primorye Region. Granitoid massifs along the Central Sikhote-Alin Fault zone in the Khabarovsk Region formed from 109 to 58 Ma. Thus, the most important tectonothermal events in the Sikhote-Alin orogen took place in the Cretaceous. Geochemical analysis indicates that most samples are I-type granitoids. They have initial 87Sr/86Sr ratios ranging from 0.7040 to 0.7083, and initial Nd isotopic ratios, expressed as εNd(t) values, from +3.0 to -5.0 (mostly 0 to -5). The data suggest that the granitoid magmas were generated by partial melting of sources with mixed lithologies, including the subducted accretionary complex ± hidden Paleozoic-Proterozoic basement rocks. Based on whole-rock Nd isotopic data, we estimated variable proportions (36-77%) of juvenile component (=mantle-derived basaltic rocks) in the generation of the granitic magmas. Furthermore, zircon Hf isotopic data (εHf(t) = 0 to +15) indicate that the zircon grains crystallized from melts of mixed sources and that crustal assimilation occurred during magmatic differentiation. The quasi-continuous magmatism in the Sikhote-Alin orogen suggests that the Paleo-Pacific plate subduction was very active in the

  19. Active Tectonics in crossroads of an evolving orogen and morphological consequences: Anatolia (United States)

    Koral, Hayrettin


    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.


    Directory of Open Access Journals (Sweden)



    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.

  1. Tectonic evolution of Bransfield Strait, West Antarctica (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.

  2. Differential tectonic evolution and hydrocarbon distribution in clastic strata of petroliferous basins in central-western China%中国中西部盆地差异构造演化与碎屑岩层系油气聚集分布

    Institute of Scientific and Technical Information of China (English)

    方成名; 黄泽光; 段铁军; 胡宗全; 杨帆


    The relationship between tectonic evolution and hydrocarbon distribution is complex in major petroliferous basins such as Sichuan, Ordos, Junggar and Tarim in central-western China. Analysis of the tectonic evolution and late differential tectonic modification of these basins shows that the four basins had the simdar process and different geologic timing of tectonic evolution and basin formation, I. E. they all have a similar basin-forming process featuring in transformation from extensional to compressional or transpressional basin. The late tectonic modification of the clastic strata is characterized by lateral aligning and vertical superimposition of three basic structural styles including foreland thrust, differential uplifts and titled structure. Tectonic activity,basin formation and late modification jointly control hydrocarbon accumulation types, sizesand distribution. Simple basin-forming process but diversified tectonic transformation determines that the four basins have similar play types but differential distribution patterns. The basic modification style of the four basins determines their hydrocarbon accumulation types, while the superposition features control the timing and sizes of hydrocarbon accumulation. Based on the understanding of the similarities and differences of tectonic controlling factors on hydrocarbon accumulation among these basins,we put forward a play classification scheme. According to this scheme,we identi- fied 4 play types including palaeo-uplift, slope, foreland folded-thrust and large fault.%对中西部地区盆地构造演化和晚期差异构造改造的分析表明,四大盆地构造-成盆具有“同序异时”的演化特征,即均具有从伸展性盆地向压性或压扭性盆地转化的成盆序列;碎屑岩层系的晚期构造改造由山前冲断、差异隆升和掀斜等3种基本型式在横向上并列和纵向上叠加而成.构造-成盆作用与晚期构造改造共同控制了碎屑岩层系的油气

  3. The compilation of the lunar digital geological map and a discussion on the tectonic evolution of the moon%月球数字地质图的编制与研究

    Institute of Scientific and Technical Information of China (English)

    王梁; 丁孝忠; 韩坤英; 庞健峰; 许可娟; 郑洪伟; 吴昊


    The compilation of the Lunar Digital Geological Map was based on the scientific exploration data obtained by Chang’E-1 and Chang’E-2 and other lunar geological data as well as research results. According to the material compositions, structure elements and the information of geochronology of the Moon, the authors compiled the Lunar Geological Map at a scale of 1∶2500000 and established spatial database by using the ArcGIS platform. The authors developed a mapping programs, processes and legends for the Lunar Digital Geological Map, and established a spatial database based on Geodatabase model by compiling and investigating geological map of the typical region, which can effectively update and manage the Digital Geological Map and thus lay the foundation for the geological comprehensive study of the Moon, the geological mapping of the whole Moon, and also the geological mapping of other celestial bodies in the future. This paper also deals with the tectonic evolution of the moon on the basis of summarizing the compilation of the Lunar Digital Geological Map and comprehensive research on a large number of lunar geological data.%提中国月球数字地质图的编制是利用嫦娥一号、嫦娥二号月球科学探测数据和其他已有月球地质资料与研究成果,通过对月球岩石成分、地质构造和形成时代等要素的研究,应用ArcGIS平台编制1∶250万月球地质图,并建立数字地质图空间数据库。本文通过对月球典型地区地质图的编制与研究,制定了月球数字地质图的编图方案、流程与图示图例,建立了Geodatabase空间数据库,为有效地对数字地质图进行更新与管理,开展月球地质综合研究、编制全月球地质图及未来开展其他天体的地质编图工作奠定了基础。通过地质图编制与大量月球资料的综合集成研究,对月球形成与构造演化进行了初步的探讨。

  4. 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 (United States)

    Wang, Zhi-wei; Xu, Wen-liang; Pei, Fu-ping; Wang, Feng; Guo, Peng


    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

  5. Advances on Active Tectonics Research

    Institute of Scientific and Technical Information of China (English)

    Chen Yong; Chen Qifu; Li Juan


    The tectonic movement at human scale has not been fully understood yet, especially for active tectonics, although it is the basis to study natural hazards and environmental variations. Many national and international scientific plans related closely to active tectonics research have been made in the past ten years. This paper briefly summarized the background of the undertaking of active tectonics research, its advances and existing problems, and the key points in its future studies are also pointed out. The emerging of new technologies like the Earth Observing Sys tem, Digital Seismology and so on provides unusual opportunities for tectonic research. It is emphasized, however, that careful analyses and building up of new theoretical frame are sill the key problems for studies of active tectonics, especially for active tectonics in China' s conti nent.

  6. Transient thermal effects in Alpine permafrost

    Directory of Open Access Journals (Sweden)

    J. Noetzli


    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

  7. Alpine radar conversion for LAWR (United States)

    Savina, M.; Burlando, P.


    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

  8. Tectonic Theory and Practice

    DEFF Research Database (Denmark)

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


    defined by Semper as a constructive precondition, a theory for developing a novel tectonic relation between home and system opens up. As a research result the paper suggests a practical spatial exploitation of the actual prefab construction, defining interiority not solely as a visual occupation......’ is an example of this sensuous interior transformation of a house into a home, a level of detailing which is, however, seldom represented in the prefabricated house. Consequently, this paper investigates whether interiority can be developed as a tectonic theory and design principle for uniting home and system...... in the development of novel prefab solutions. This is pursued trough a deductive study comparing Gottfried Semper’s theories on the origins of construction with Werner Blaser’s technical and practical studies of the joint. In combining Blaser’s constructive understanding of the joint with the interior softness...

  9. Frost resistance in alpine woody plants. (United States)

    Neuner, Gilbert


    This report provides a brief review of key findings related to frost resistance in alpine woody plant species, summarizes data on their frost resistance, highlights the importance of freeze avoidance mechanisms, and indicates areas of future research. Freezing temperatures are possible throughout the whole growing period in the alpine life zone. Frost severity, comprised of both intensity and duration, becomes greater with increasing elevation and, there is also a greater probability, that small statured woody plants, may be insulated by snow cover. Several frost survival mechanisms have evolved in woody alpine plants in response to these environmental conditions. Examples of tolerance to extracellular freezing and freeze dehydration, life cycles that allow species to escape frost, and freeze avoidance mechanisms can all be found. Despite their specific adaption to the alpine environment, frost damage can occur in spring, while all alpine woody plants have a low risk of frost damage in winter. Experimental evidence indicates that premature deacclimation in Pinus cembra in the spring, and a limited ability of many species of alpine woody shrubs to rapidly reacclimate when they lose snow cover, resulting in reduced levels of frost resistance in the spring, may be particularly critical under the projected changes in climate. In this review, frost resistance and specific frost survival mechanisms of different organs (leaves, stems, vegetative and reproductive over-wintering buds, flowers, and fruits) and tissues are compared. The seasonal dynamics of frost resistance of leaves of trees, as opposed to woody shrubs, is also discussed. The ability of some tissues and organs to avoid freezing by supercooling, as visualized by high resolution infrared thermography, are also provided. Collectively, the report provides a review of the complex and diverse ways that woody plants survive in the frost dominated environment of the alpine life zone.

  10. Caribbean tectonics and relative plate motions (United States)

    Burke, K.; Dewey, J. F.; Cooper, C.; Mann, P.; Pindell, J. L.


    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.

  11. Tectonic Evolution and Control Effect on Sandstone-Type Uranium Mineralization in Changqi Placantieline%大庆长垣构造演化特征及对砂岩型铀矿成矿的控制作用

    Institute of Scientific and Technical Information of China (English)



    大庆长垣的形成主要受三个构造期次的影响,即早白垩世嫩江组末期、晚白垩世明水组末期和早第三纪末期.三个构造运动期分别呈现了隆起雏型、形成大庆长垣的整体背斜及背斜整体隆升加高并遭受剥蚀形成剥蚀天窗.该构造运动造就了该区多个有利铀成矿条件,一是使背斜顶部遭受剥蚀形成的构造天窗,有利于含铀含氧水渗入地下岩层;二是改变了地层产状,使地下水从滞流状态变为循环状态;三是改善了地层和岩石的物理性质,增加了岩层的渗透性;四是产生了新断裂或激活了早期断层,是深部还原性烃类流体上升的通道.因此,大庆长垣东西两翼应是寻找铀矿的有利部位,其中东翼更为有利.%The formation of Daqing Placantieline was controlled by three tectonic episodes, i. e. the end of Nen-jiang Formation in Early Cretaceous and the end of Mingshui Formation in late Cretaceous as well as the end of early Tertiary Period. These three tectonic episodes present diversified geological feature including uplift prototype , overall anticline and denudation window formed by anticline uplift and erosion. The tectonic movements resulted in several favorable conditions for uranium mineralization: 1 ) the top of anticline denuded by tectonic movements and formation of denudation window. Denudation window is helpful for uranium-oxygen water flowing into underground rock formations; 2) tectonic movements altered the attitude of stratum so that groundwater converted from stagnant state to circulatory state; 3) tectonic movements improved the physical properties and increased permeability of the rock; 4) tectonic movements produced new faults or activated the early faults, which are the pathways of deep reducing hydrocarbon fluids lifting up. Therefore, the east and west limbs of Daqing Placantieline should be the favorable parts for exploring the uranium,the eastern part of Daqing Placantieline is

  12. 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


    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

  13. Effects of temperature and altitude on the evolutional characteristics of seed germination in an alpine meadow%温度和海拔对高寒草甸植物种子萌发进化特性的影响

    Institute of Scientific and Technical Information of China (English)


    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.

  14. Quarternary tectonics, Task 1

    Energy Technology Data Exchange (ETDEWEB)

    Bell, J.W.


    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.

  15. Dynamics of Tectonic Plates

    CERN Document Server

    Pechersky, E; Sadowski, G; Yambartsev, A


    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.

  16. 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...

  17. The tectonic origin of the Bay of Bengal and Bangladesh

    Digital Repository Service at National Institute of Oceanography (India)

    Talwani, M.; Desa, M.; Ismaiel, M.; Krishna, K.S.

    We are able to decipher the tectonic evolution of the Bay of Bengal, a puzzle which has not been satisfactorily solved in the past, and we are also able to shed new light on origin of the buried 85°E Ridge. We do so by incorporating a number...

  18. 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.

  19. Developing the plate tectonics from oceanic subduction to continental collision

    Institute of Scientific and Technical Information of China (English)

    ZHENG YongFei; YE Kai; ZHANG LiFei


    The studies of continental deep subduction and ultrahigh-pressure metamorphism have not only promoted the development of solid earth science in China,but also provided an excellent opportunity to advance the plate tectonics theory.In view of the nature of subducted crust,two types of subduction and collision have been respectively recognized in nature.On one hand,the crustal subduction occurs due to underflow of either oceanic crust (Pacific type) or continental crust (Alpine type).On the other hand,the continental collision proceeds by arc-continent collision (Himalaya-Tibet type) or continent-continent collision (Dabie-Sulu type).The key issues in the future study of continental dynamics are the chemical changes and differential exhumation in continental deep subduction zones,and the temporal-spatial transition from oceanic subduction to continental subduction.

  20. 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


    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.

  1. Why is understanding when Plate Tectonics began important for understanding Earth? (United States)

    Korenaga, J.


    Almost all kinds of geological activities on Earth depend critically on the operation of plate tectonics, but did plate tectonics initiate right after the solidification of a putative magma ocean, or did it start much later, e.g., sometime during the Archean? This problem of the initiation of plate tectonics in the Earth history presents us a unique combination of observational and theoretical challenges. Finding geological evidence for the onset of plate tectonics is difficult because plate tectonics is a dynamic process that continuously destroys a remnant of the past. We therefore need to rely on more secondary traces, the interpretation of which often involves theoretical considerations. At the same time, it is still hard to predict, on a firm theoretical ground, when plate tectonics should have prevailed, because there is no consensus on why plate tectonics currently takes place on Earth. Knowing when plate tectonics began is one thing, and understanding why it did so is another. The initiation of plate tectonics is one of the last frontiers in earth science, which encourages a concerted effort from both geologists and geophysicists to identify key geological evidence and distinguish between competing theories of early Earth evolution. Such an endeavor is essential to arrive at a self-contained theory for the evolution of terrestrial planets.

  2. Active tectonics of the Andes (United States)

    Dewey, J. F.; Lamb, S. H.


    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

  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


    Makoto Tani


    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


    Tani, Makoto


    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. Island formation and tectonic processes

    NARCIS (Netherlands)

    Draper, G.


    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 tecto

  6. Paleogene palaeogeography and basin evolution of the Western Carpathians, Northern Pannonian domain and adjoining areas (United States)

    Kováč, Michal; Plašienka, Dušan; Soták, Ján; Vojtko, Rastislav; Oszczypko, Nestor; Less, György; Ćosović, Vlasta; Fügenschuh, Bernhard; Králiková, Silvia


    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

  7. Alpine-hydrological observations at the "Zugspitzplatt" (United States)

    Schulz, Karsten; Bernhardt, Matthias; Wetzel, Karl F.; Haerer, Stefan


    Alpine Regions are considered to be important sources of freshwater for large regions world wide. The storage of water as snow and/or ice, as well as subsequent melting processes during spring and summer are important factors for water resources management and flood control. However, alpine regions and relevant hydrological processes are generally not very well investigated and therefore poorly understood. This is mainly due to the difficulties of setting up and maintaining monitoring stations in often remote places, under harsh environmental conditions. The "Environmental Research Station Schneefernerhaus" (UFS) located at 2700 m altitude within the "Zugspitzplatt"/Wettersteingebirge, close to Garmisch-Partenkirchen, Germany, is managed by the Bavarian Government and is run by 10 universities and research institutions as consortium partners. Within this "Centre for altitude, climate and environment research in Bavaria", the Universities of Augsburg and Munich have recently intensified their research on alpine hydrological processes in order to improve the aforementioned limitations. The Zugspitzplatt catchment serves as a typical representation of the northern "Kalkalpen". Its unique geological structure serve as an ideal natural lysimeter, allowing water and solute mass balances to be derived and closed from meteorological and hydrological measurements. Long term meteorological data and a large variety of newly implemented (snow-)hydrological, micrometeorological and remote sensing instrumentation will allow detailed and long term studies on the dynamics of alpine hydrological processes. In our contribution we will present the research catchment and its instrumentation as well as first results from last years measurements.

  8. 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)


    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

  9. Transcultural Tectonic Connections

    DEFF Research Database (Denmark)

    Carter, Adrian


    have been informed by his understanding of boat-building, reference to nature, extensive travels and broad transcultural influences. The paper will also consider to what extent Utzon’s work can be seen to have been a precursor and direct influence upon subsequent developments within architecture......’s architecture ranges from the modest to the monumental; from the Kingo courtyard houses, the finest Scandinavian example of humane housing, to the sculptural abstraction and technical innovation of the Sydney Opera House; an iconic work of modern architecture that has come to symbolise not only a city, but also...... with such original unrealised projects as the subterranean Silkeborg Art Museum, Utzon’s work embodies a visionary approach to architecture that is site specific and poetic, tectonic and humane; informed by a profound appreciation of nature and diversity of human cultures, as sources of inspiration and analogy...

  10. Plate Tectonics: A Paradigm under Threat. (United States)

    Pratt, David


    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. 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.


    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.

  12. Optimal Planet Properties For Plate Tectonics Through Time And Space (United States)

    Stamenkovic, Vlada; Seager, Sara


    Both the time and the location of planet formation shape a rocky planet’s mass, interior composition and structure, and hence also its tectonic mode. The tectonic mode of a planet can vary between two end-member solutions, plate tectonics and stagnant lid convection, and does significantly impact outgassing and biogeochemical cycles on any rocky planet. Therefore, estimating how the tectonic mode of a planet is affected by a planet’s age, mass, structure, and composition is a major step towards understanding habitability of exoplanets and geophysical false positives to biosignature gases. We connect geophysics to astronomy in order to understand how we could identify and where we could find planet candidates with optimal conditions for plate tectonics. To achieve this goal, we use thermal evolution models, account for the current wide range of uncertainties, and simulate various alien planets. Based on our best model estimates, we predict that the ideal targets for plate tectonics are oxygen-dominated (C/Ometallic cores super-Mercury, rocky body densities of ~7000kgm-3), and with small mantle concentrations of iron 0%), water 0%), and radiogenic isotopes 10 times less than Earth). Super-Earths, undifferentiated planets, and especially hypothetical carbon planets, speculated to consist of SiC and C, are not optimal for the occurrence of plate tectonics. These results put Earth close to an ideal compositional and structural configuration for plate tectonics. Moreover, the results indicate that plate tectonics might have never existed on planets formed soon after the Big Bang—but instead is favored on planets formed from an evolved interstellar medium enriched in iron but depleted in silicon, oxygen, and especially in Th, K, and U relative to iron. This possibly sets a belated Galactic start for complex Earth-like surface life if plate tectonics significantly impacts the build up and regulation of gases relevant for life. This allows for the first time to

  13. The experimental investigation of microcracks nucleation in typical tectonics

    Institute of Scientific and Technical Information of China (English)


    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.

  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 (United States)

    Domínguez-González, Leomaris; Andreani, Louis; Stanek, Klaus P.; Gloaguen, Richard


    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. The potential for retreating alpine glaciers to alter alpine ecosystems in the Colorado Front Range (United States)

    Hall, E.; Baron, J.


    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.

  16. 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


    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.

  17. Continental tectonics in the aftermath of plate tectonics (United States)

    Molnar, Peter


    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. Occurrence of ignimbrite volcanics in the northern Espirito Santo Basin, Brazil: an advance in the model of tectonic-sedimentary evolution of the basin; Ocorrencia de rochas vulcanicas ignimbriticas na porcao norte da Bacia do Espirito Santo: evolucao do modelo tectono-sedimentar

    Energy Technology Data Exchange (ETDEWEB)

    Novais, Luis Carlos Chaves [PETROBRAS, ES (Brazil). Unidade de Negocio de Exploracao e Producao do Espirito Santo. Gerencia de Reservatorios], e-mail:; Zelenka, Tibor [University of Miskolc (Hungary). Dept. of Geology], e-mail:; Szatmari, Peter [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas Leopoldo A. Miguez de Mello. Gerencia de Geologia Estrutural e Geotectonica], e-mail:; Motoki, Akihisa [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Dept. de Mineralogia e Petrologia Ignea], e-mail:; Aires, Jose Ribeiro [PETROBRAS, Rio de Janeiro, RJ (Brazil). Abastecimento-Petroquimica e Fertilizantes. Gerencia Setorial de Seguranca, Meio Ambiente e Saude], e-mail:; Tagliari, Claudio VInicius [PETROBRAS, ES (Brazil). Unidade de Negocio de Exploracao e Producao do Espirito Santo. Gerencia de Avaliacao de Blocos e Interpretacao Geologica e Geofisica], e-mail:


    The intention of this work is to provide information on ignimbrite volcanoclastics, outcropping in the northern onshore part of the Espirito Santo Basin, and to examine their role in the tectonic-sedimentary evolution of the basin. We identified ignimbrites, pyroclastics of rhyolitic to dacitic composition, along the NNW-SSE to NW-SE trending transcurrent fault system named here Sao Mateus Alignment or Sao Mateus Arch. We followed the mostly horizontally layered ignimbrites, at least 50 m thick, for about 10 km along and close to the margins of the Sao Mateus River. These ignimbrite bodies had been mapped before as fluvio-lacustrine sandstones of the Tertiary Rio Doce/Barreiras Formation, without recognizing their partially volcanoclastic character. Microscopic examination suggests idiomorphic and fragmented {proportional_to}-quartz phenocrysts, contained in a hydrothermally altered matrix of clay minerals and zeolites. The fragmented form of the phenocrysts points to explosive volcanic activity; grain size tends to increase westward, probably indicating the principal place of volcanic centers. The outcropping sequence of ignimbritic rocks provides a major advance in the understanding of the basin's Cenozoic tectonic-structural history contributing to a revision of its stratigraphy. (author)

  19. 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


    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

  20. Glacial reorganization of topography in a tectonically active mountain range (United States)

    Adams, Byron; Ehlers, Todd


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

    DEFF Research Database (Denmark)

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


    Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses to ...... by plate tectonic forces, induced perhaps by a change in the Iceland plume (a hot pulse) and/or by changes in intra-plate stresses related to global tectonics....

  2. Multiple Tectonic Regimes and Diverging Geologic Histories of Terrestrial Planets: The Importance of the Early Years (United States)

    Weller, M. B.; Lenardic, A.


    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. Navigating Towards Digital Tectonic Tools

    DEFF Research Database (Denmark)

    Schmidt, Anne Marie Due; Kirkegaard, Poul Henning


    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 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...

  4. Tectonics: Changing of the plates (United States)

    Brandon, Alan


    The composition of Earth's crust depends on the style of plate tectonics and of the melting regimes in the mantle. Analyses of the oldest identified rocks suggest that these styles and the resulting crust have changed over Earth's history.

  5. The Ecology of Urban Tectonics

    DEFF Research Database (Denmark)

    Beim, Anne; Hvejsel, Marie Frier


    it as part of an everyday practice and regional building culture. “Can material interest and tectonic aspiration inform the urban scale and how can the urban context call for tectonic qualities in ordinary buildings?” We ask, and “Can we speak of an ‘ecology of urban tectonics’ where the scale of the urban...... that link the urban fabric to the human scale. Consequently, the paper studies how meta-level concepts as everyday building culture, the regional and the notion of ecology link together and the commonalities they share that often happen to be mutually interdependent: culture /tradition, locality, and scale...... designs that link culture/tradition, locality and scale around the human experience of the work. One could argue that his buildings define an ecological tectonic approach that addresses the urban scale in a direct unimpressed and highly original manner, outlining a direction for an ‘urban tectonic...

  6. Tectonic Subsidence Analysis of the Pearl River Mouth Basin, Northern South China Sea (United States)

    Tang, X.; Huang, S. S. X. E. C.; Zhuang, W.; LIU, Z.; Duan, W.; Hu, S.


    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.


    Gualtieri, J.L.; Thurber, H.K.


    The Alpine Lakes Wilderness study area, located in the central part of the Cascade Mountains of Washington was examined for its mineral-resource potential. On the basis of that study the area was found to contain deposits of copper, other base metals, and gold and silver. Probable or substantiated mineral-resource potential exists for these commodities in the southwest-central, northwest, and southeast-central parts of the area. The geologic terrane precludes the occurrence of fossil fuel resources.

  8. 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


    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.

  9. Soil Fauna Affects Dissolved Carbon and Nitrogen in Foliar Litter in Alpine Forest and Alpine Meadow.

    Directory of Open Access Journals (Sweden)

    Shu Liao

    Full Text Available Dissolved organic carbon (DOC and total dissolved nitrogen (TDN are generally considered important active biogeochemical pools of total carbon and nitrogen. Many studies have documented the contributions of soil fauna to litter decomposition, but the effects of the soil fauna on labile substances (i.e., DOC and TDN in litter during early decomposition are not completely clear. Therefore, a field litterbag experiment was carried out from 13th November 2013 to 23rd October 2014 in an alpine forest and an alpine meadow located on the eastern Tibetan Plateau. Litterbags with different mesh sizes were used to provide access to or prohibit the access of the soil fauna, and the concentrations of DOC and TDN in the foliar litter were measured during the winter (the onset of freezing, deep freezing and thawing stage and the growing season (early and late. After one year of field incubation, the concentration of DOC in the litter significantly decreased, whereas the TDN concentration in the litter increased. Similar dynamic patterns were detected under the effects of the soil fauna on both DOC and TDN in the litter between the alpine forest and the alpine meadow. The soil fauna showed greater positive effects on decreasing DOC concentration in the litter in the winter than in the growing season. In contrast, the dynamics of TND in the litter were related to seasonal changes in environmental factors, rather than the soil fauna. In addition, the soil fauna promoted a decrease in litter DOC/TDN ratio in both the alpine forest and the alpine meadow throughout the first year of decomposition, except for in the late growing season. These results suggest that the soil fauna can promote decreases in DOC and TDN concentrations in litter, contributing to early litter decomposition in these cold biomes.

  10. Usbnd Pb zircon geochronology constraints on the ages of the Tananao Schist Belt and timing of orogenic events in Taiwan: Implications for a new tectonic evolution of the South China Block during the Mesozoic (United States)

    Chen, Wen-Shan; Huang, Yi-Chang; Liu, Chang-Hao; Feng, Han-Ting; Chung, Sun-Lin; Lee, Yuan-Hsi


    The Tananao Schist Belt is a low-pressure metamorphic complex comprised of three lithological units of marble, schist formation, and granite, in ascending order of proportion. Previous studies have found that the schist formation was formed during the Mesozoic. However, there is a lack of geochronological data to corroborate the schist protolith and metamorphic ages. In this study, we have used Usbnd Pb zircon geochronology to provide a time frame for the creation of the schist formation and metamorphism, as well as a new tectonic model. Twenty-three schist and eleven meta-magmatic samples were used for Usbnd Pb dating by LA-ICP-MS. Results from the youngest peak age of detrital zircon indicate that the schist formed in a new depositional age of 120-110 Ma and, therefore, is different from the previously estimated age of the Paleozoic-Mesozoic. Additionally, the block-in-matrix schist indicates an age that ranges from 270 to 80 Ma and was inferred from the chaotic deposits to be a metamorphic mélange. The Tananao Schist Belt appears to represent an arc-trench system that formed during the Cretaceous in the South China Block margin. Moreover, the youngest Usbnd Pb age of 80 Ma from the leucogranite dike and schist, constrains the upper age limit for a metamorphism that is younger than the previously accepted age of 100-90 Ma. The contact layer between Permian-Triassic marble and the overlying early Cretaceous schists remains a chloritoid bed that is, therefore, considered to be a paleosol at the unconformity, which formed over an extended duration of 60 ± 30 Ma. The stratigraphic contact indicates a long period of erosion during the Jurassic and suggests that a tectonic event occurred. However, we propose that two important metamorphic events took place prior to, and following, the schist formation during the Jurassic and late Cretaceous orogenic events.

  11. Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau. (United States)

    Liu, Shuli; Zhang, Fawei; Du, Yangong; Guo, Xiaowei; Lin, Li; Li, Yikang; Li, Qian; Cao, Guangmin


    The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. PMID:27494253

  12. Interaction of various flow systems in small alpine catchments: conceptual model of the upper Gurk Valley aquifer, Carinthia, Austria (United States)

    Hilberg, Sylke; Riepler, Franz


    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.

  13. Tectonic implications of Mars crustal magnetism. (United States)

    Connerney, J E P; Acuña, M H; Ness, N F; Kletetschka, G; Mitchell, D L; Lin, R P; Reme, H


    Mars currently 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). A new map of the magnetic field of Mars, compiled by using measurements acquired at an approximately 400-km mapping altitude by the Mars Global Surveyor spacecraft, is presented here. The increased spatial resolution and sensitivity of this map provide new insight into the origin and evolution of the Mars crust. Variations in the crustal magnetic field appear in association with major faults, some previously identified in imagery and topography (Cerberus Rupes and Valles Marineris). 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 support the notion that the Mars crust formed during an early era of plate tectonics.


    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


    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.

  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


    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. Tectonic microplates in a wax model of sea-floor spreading (United States)

    Katz, Richard F.; Ragnarsson, Rolf; Bodenschatz, Eberhard


    Rotating, growing microplates are observed in a wax analogue model of sea-floor spreading. Wax microplates are kinematically similar to sea-floor tectonic microplates in terms of spreading rate and growth rate. Furthermore, their spiral pseudofault geometry is quantitatively consistent with Schouten's oceanic microplate model. These results suggest that Schouten's edge-driven microplate model captures the kinematics of tectonic microplate evolution on Earth. Based on the wax observations, a theory for the nucleation of overlapping spreading centres, the precursors of tectonic microplates, is developed.


    Institute of Scientific and Technical Information of China (English)

    HU Bin; DAI Tagen; HU Ruizhong; GUO Qun


    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.

  18. On the History of the Continents:A Story of Plate Tectonics and Earth Tides


    Bo Pedersen, Flemming


    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...

  19. Tectonics of the Easter plate (United States)

    Engeln, J. F.; Stein, S.


    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.


    Institute of Scientific and Technical Information of China (English)

    李天德; В.Н.波里扬斯基


    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。

  1. 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


    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

  2. 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


    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).

  3. Explaining plant-soil diversity in Alpine ecosystems: more than just time since ecosystem succession started (United States)

    Lane, Stuart; Baetz, Nico; Borgeaud, Laure; Verrecchia, Eric; Vittoz, Pascal


    Ecosystem succession in Alpine environments has been a focus of research for many decades. Following from the classic ideas of Jenny (1941, 1961), following perturbation, an ecosystem (flora, fauna and soil) should evolve as a function of time at a rate conditioned by external variables (relief, climate, geology). More recently, biogeomorphologists have focused upon the notion of co-evolution of geomorphic processes with ecosystems over very short through to very long (evolutionary) time-scales. Alpine environments have been a particular focus of models of co-evolution, as a means of understanding the rate of plant colonization of previously glaciated terrain. However, work in this field has tended to adopt an over simplified view of the relationship between perturbation and succession, including: how the landform and ecosystem itself conditions the impact of a perturbation to create a complex spatial impact; and how perturbations are not simply ecosystem destroyers but can be a significant source of ecosystem resources. What this means is that at the within landform scale, there may well be a complex and dynamic topographic and sedimentological template that co-evolves with the development of soil, flora and fauna. In this paper, we present and test conceptual models for such co-evolution for an Alpine alluvial fan and an Alpine piedmont braided river. We combine detailed floristic inventory with soil inventory, survey of edaphic variables above and below ground (e.g. vertical and lateral sedimentological structure, using electrical resistance tomography) and the analysis of historical aerial imagery. The floristic inventory shows the existence of a suite of distinct plant communities within each landform. Time since last perturbation is not a useful explanatory variable of the spatial distribution of these communities because: (1) perturbation impacts are spatially variable, as conditioned by the extent distribution of topographic, edaphic and ecological

  4. 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.


    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)

  5. Emerging Possibilities and Insuperable Limitations of Exogeophysics: The Example of Plate Tectonics (United States)

    Stamenković, Vlada; Seager, Sara


    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.

  6. Tectonics: The meaning of form

    DEFF Research Database (Denmark)

    Christiansen, Karl; Brandt, Per Aage

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

  7. 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)

  8. 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


    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

  9. Modelling vegetation dynamics for Alpine meadows (United States)

    Della Chiesa, Stefano; Bertoldi, Giacomo; Wohlfahrt, Georg; Rist, Armin; Niedrist, Georg; Albertson, John D.; Tappeiner, Ulrike


    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

  10. Thermotectonic evolution of the Apuseni mountains (Romania) based on structural and geothermochronological data (United States)

    Reiser, M. K.; Fügenschuh, B.; Schuster, R.


    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

  11. 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.)

  12. Plate tectonics conserves angular momentum

    Directory of Open Access Journals (Sweden)

    C. Bowin


    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

  13. Metabolic Profiling of Alpine and Ecuadorian Lichens

    Directory of Open Access Journals (Sweden)

    Verena K. Mittermeier


    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.

  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


    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. Pleistocene origin and population history of a neoendemic alpine butterfly. (United States)

    Schoville, Sean D; Stuckey, Matthew; Roderick, George K


    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

  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


    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. 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)


    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.

  18. Zircon U-Pb and Lu-Hf isotopic and whole-rock geochemical constraints on the Lanhe and Heichashan Groups: Implications for the Paleoproterozoic tectonic basin evolution of the Lüliang Complex (United States)

    Liu, Chaohui; Zhao, Guochun; Liu, Fulai; Shi, Jianrong; Ji, Lei; Liu, Pinghua; Yang, Hong; Liu, Lishuang; Wang, Wei; Tian, Zhonghua


    Group was deposited in a foreland basin. Conversion of the tectonic basin from the middle Paleoproterozoic back-arc basin to the late Paleoproterozoic foreland basin is well consistent with the model that the single collision to form the basement of the North China Craton happened at ~ 1.85 Ga.

  19. Planets and satellites: tectonic twins (United States)

    Kochemasov, G. G.


    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

  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. Mars crustal magnetism, plate tectonics, and more (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 Ea