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Allemand, Pascal. "Mecanique du rifting continental : approche experimentale et application au rifting oligocene ouest europeen." Rennes 1, 1988. http://www.theses.fr/1988REN10088.
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L'etude du champ de deformation en surface des rifts continentaux montre l'acquisition tardive d'asymetrie quasi-systematique. Des experiences en laboratoire a partir d'une lithosphere modelisee montrent que l'asymetrie est due a la presence d'un cisaillement ductile a la base des rifts qui accommode un decalage entre les deformations de la croute fragile et du manteau superieur. Les differentes conclusions sont appliquees au rift oligocene ouest europeen
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Vitale, Brovarone Alberto. "From rifting to orogen : structure of Alpine Corsica and inheritance of rifting-related architectures in HP terranes." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20029/document.
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La Corse Alpine offre une section complète du prisme orogénique alpin où la plupart des équivalents des unités décrites dans les Alpes Occidentales peuvent être trouvés sur une section de 40 km. Les minéraux d'haute pression sont exceptionnellement bien préservés, particulièrement la lawsonite, offrant un accès unique à la compréhension de zones de subduction. La Corse alpine est formée par une pile complexe d’unités métamorphiques d'origine continentale et océanique. Ces unités ont été interprétées soit comme des mélanges tectoniques complexes formés pendant la subduction alpine, soit comme les parties plus continues de lithosphère continentale et-ou océanique. Les rares estimations de condition PT sur des larges régions de la chaîne résultent en plusieurs incertitudes dans l'identification des limites séparant les unités qui ont subi des évolutions tectono-métamorphiques différentes et, par conséquent, dans la définition d'une architecture complète de la chaîne. Les données de terrain, structurelles et métamorphiques obtenues dans cette étude aux différentes échelles suggèrent que la chaîne de la Corse alpine est caractérisée par une forte conservation de structures pré-alpin, de la micro-échelle à l'échelle de la chaîne, malgré la déformation intense associée avec le métamorphisme, qui a localement donné les conditions du facies éclogitique et lawsonite. En détail, seulement neuf domaines tectono-métamorphiques homogènes ont été identifiés. Ces terrains peuvent être attribué aux domaines paléogéographiques différents qui ont subi des évolutions tectono-métamorphiques différentes. Malgré ça, les données géochronologiques fournies pendant cette étude indiquent que la Corse alpine résulte d'une évolution complexe, étant caractérisée par la signature claire tant de la tectonique alpine Eocène, à 35 Ma, que de la tectonique apennine, à 25 Ma. Les résultats fournis dans cette thèse contribuent non seulement à la compréhension des processus de subduction et de formation de montagnes, mais donnent aussi des contraintes importantes pour déchiffrer les systèmes Tethys-Alpes et Alpes-ApennineAlpine Corsica offers a complete section through the Alpine orogenic wedge where most equivalent of the units described in the Western Alps may be found over a 40 km section. High-pressure mineral assemblages are exceptionally well preserved, especially lawsonite, offering a unique access to the understanding of deeply subducted terranes.Alpine Corsica consists of a complex stack of variably metamorphosed units of continental and Tethys-derived material. These units have been interpreted either as complex tectonic mixing formed during the Alpine subduction, or as more continuous portions of continental and/or oceanic lithosphere. The lack of detailed PT estimates over wide regions of the belt results in several uncertainties in identifying the boundaries separating units that experienced different tectono-metamorphic evolutions and, consequently, in the definition of an exhaustive architecture of the belt.Field, structural and metamorphic data collected in this study at different scales suggest that the Alpine Corsica belt is characterized by a high preservation of pre-Alpine sctructures, from the micro-scale up the scale of the belt, despite the intense deformation essociated with metamorphism, which locally reached lawsonite-eclogite metamorphism. In particular, only nine homogeneous tectono-metamorphic domains have been identified. These terranes can be referred to different paleogeographic domains that experienced different tectono-metamorphic evolutions.Despite that, geochronological data provided during this study indicate that Alpine Corsica results fro a complex polyphase evolution, being characterized by clear signature of both Alpine tectonics, at around 35 Ma, and Apennine tectonics, at around 25 Ma.Results provided in this paper contribute not only to the understanding of processes of subduction and mountain building, but also give important constraints for deciphering the Tethys-Alps and Alps-Apennine systems
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Sutherland, Fiona Helen. "Continental rifting across the Southern Gulf of California." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3220419.
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Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed September 7, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 163-173).
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Allemand, Pascal. "Approche expérimentale de la mécanique du rifting continental." Phd thesis, Université Rennes 1, 1988. http://tel.archives-ouvertes.fr/tel-00594518.
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Les rifts continentaux sont des zones étroites et allongées d'extension de la lithosphère. Une étude du champ de déformation en surface montre leur carractère asymétrique quasi-systématique. Cette asymétrie est acquise tardivemen t au cours de la déformation. La lithosphère étant considérée comme un multicouche fragile/d uctile, une modélisation analogique de sa striction est réalisée en appliquant une extension ponctuelle sur des multicouches sable/silicone dimensionnés. Ces expériences montrent que: -l'asymétrie est due à la présence d'un cisaillement ductile à la ba se des rifts qui accommode un décalage entre les déformations de la croûte fra gile et du manteau supérieur -la déformation est contrôlée par la couche la plus résistante de la lithosphère (manteau supérieur) -la déformation du manteau supérieur est conditionnée par des hétérogénéités internes préexistantes (anciennes structures) -la largeur initiale des rifts est fonction de la profondeur de l'interface fragile/ductile dans la croûte ou dans le manteau -la largeur d'une zone active étirée dépend du couplage entre la coûte fragile et la croûte ductile. Ces conclusions sont appliquées au rift oligocène ouest européen et permettent d'expliquer la variation du champ de déformation d'un segment du rift à l'autre. ,
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Bryon, Jonathan Geoffrey. "A comparison of active and ancient rifting processes." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615018.
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Allemand, Pascal. "Approche expérimentale de la mécanique du rifting continental /." Rennes : Centre armoricain d'étude structurale des socles, 1990. http://catalogue.bnf.fr/ark:/12148/cb35412460d.
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Birt, Christopher Simon. "Geophysical investigation of active continental rifting in southern Kenya." Thesis, University of Leicester, 1996. http://hdl.handle.net/2381/34979.
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The history of uplift, volcanism and faulting, and past geophysical studies suggest that extension in the Kenya Rift is actively driven by an upwelling thermal anomaly. The KRISP 94 experiment included a 440 km seismic refraction profile in southern Kenya to investigate the deep structure of the rift, 150 km east of the exposed boundary between the Archean Nyanza craton and the Proterozoic Mozambique orogenic belt. Combined travel-time and gravity interpretations produce an integrated crustal and upper mantle model, showing extensive thrusting of the mobile-belt over the cratonic margin. The rift itself has developed above the buried suture between these units. The asymmetric rift basin (filled with low velocity lavas or sediments) has a maximum depth of 4 km adjacent to the western bounding fault. The high velocity (7.0-7.2 kms-1) lowest crustal layer is modified beneath the rift, possibly by the addition of cumulate layers (products of fractional crystallization). A small amount of crustal thinning (1-2 km) directly beneath the rift axis suggests a pure-shear mechanism at depth. Minimum crustal extension is 4 km, but could be up to 10 km if the whole of the lowest crustal layer is a new magmatic addition. A long-wavelength regional gravity trend is consistent with the presence of a mantle plume beneath the craton to the west. A study of local earthquakes in Tanzania shows that the rift is propagating southwards along the craton margin. Many deep earthquakes (> 20 km) suggest cooler crustal temperatures than in Kenya, and preliminary travel-time tomography shows only minor crustal velocity variations. The results are consistent with rifting in Kenya being driven by an upwelling diapir, originating from a mantle plume beneath the craton. As it has spread, the diapir has been focussed along the suture between the Archean and Proterozoic units, but has not yet produced extensive crustal modification of the youngest part of the rift in Tanzania.
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Jones, Joshua Robert. "Investigating volcano tectonic interactions in the Natron Rift of the East African Rift System." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103780.
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Continental rifting, like other plate tectonic processes, plays a large role in shaping the Earth's crust. Active rift zones evolve from repeated tectonic and magmatic events including volcanic activity. Through investigations of currently and previously active rifts, scientists have discovered considerable interactions between these tectonic and magmatic processes during a rift's evolution; however questions remain about these interactions especially in youthful stages of rifts. We investigate an early phase magma-rich section of the East African Rift System (EARS), named the Eastern Branch to assess volcano-tectonic interactions. The Eastern Branch of the EARS consists of volcanically rich rifts that are actively spreading the Nubian Plate, Somalian plates, and Victoria block at different evolutionary stages making it an ideal study area for volcano-tectonic interactions. Our initial investigation of active volcano-tectonic interactions centered on a rifting event that occurred between 2007-2008 in the Natron Rift, a rift segment in the southern Eastern Branch located in Northern Tanzania. This rifting event contained multiple occurrences of tectonic, magmatic, and volcanic activity in close proximity. We examine the stress transferred from these events to the Natron Fault, which is the major border fault in the area, with analytical modeling using the USGS program Coulomb 3.4. We processed Global Positioning System (GPS) data that recorded slip on the major border fault in the region in early January 2008 and test which events could generate large enough stress changes to trigger the observed slip using a previously defined threshold of 0.1 MPa. These initial models were created using simplified
model parameters, such as an elastic homogeneous half-space, and find that 1) magmatically induced stress perturbations have the potential to trigger fault slip on rift border faults, 2) magmatic events have the potential to trigger strike‐slip motions on a rift border fault, and 3) the proximity of magmatic activity may affect occurrences of slip on adjacent border faults. We then further investigate volcano-tectonic interactions in the Natron Rift by testing using numerical modeling with the CIG finite element code PyLith. We systematically test how adding topography, heterogeneous materials, and various reservoir volumes to a deflating 3 km deep magma reservoir system at the active volcano Ol Doinyo Lengai can affect stress transfer to the adjacent Natron Fault. We compare eight models with variations in topography, material properties, and reservoir volumes to calculate the percent differences between the models; to test their effects on the stress change results. We find that topography plays the largest role with the effect increasing with reservoir size. Finally, we seek to improve the capability of investigating volcano-tectonic interactions in the Natron Rift at faster time- scales by improving Global Navigation Satellite System (GNSS) positioning data (latitude, longitude, and height) collection and distribution capabilities. In the final part of this work, we describe a new Python-based data broker application, GNSS2CHORDS, that can stream real-time centimeter precision displacement data distributed by UNAVCO real-time GNSS data services to an online EarthCube cybertool called CHORDS. GNSS2CHORDS is applied to the TZVOLCANO GNSS network that monitors Ol Doinyo Lengai in the Natron Rift and its interactions with the adjacent rift border fault, the Natron Fault. This new tool provides a mechanism for assessing volcano-tectonic interactions in real-time. In summary, this work provides a new avenue for understanding volcano-tectonic interactions at unprecedented, 1-second time-scales, demonstrates slip can be triggered by small stress changes from magmatic events during early phase rifting, and provides insights into the key role of volcanic topography during volcano-tectonic interactions.Doctor of Philosophy
Investigating interactions between active volcanoes and tectonics (fault zones) is important for understanding how continental rifts grow and evolve over time. Modern researchers use geodetic data, geologic models, and computer simulations of rift processes; like volcanic eruptions and fault movement; to understand how stress in transferred and material deforms due to rift activity. We are especially interested in understanding the stress interactions when volcanic eruptions and earthquakes happen together over a short time period. Our projects apply these tools to examine a segment of the largest active continental rift zone, the Natron Rift in the East African Rift System (EARS), to understand more about the details of these volcano-tectonic interactions when continents break apart (rifting). We first present results that stress transferred to the Natron Fault associated with magmatic activity from the volcano Ol Doinyo Lengai may trigger a major fault to move. Next, we continue our investigations into volcano-tectonic interactions by seeing how volcanic properties could affect stress transferred in the Natron Rift region. We choose to initially test stress variations associated with different 1) topography surfaces, 2) material properties, and 3) reservoir volumes associated with the volcano Ol Doinyo Lengai using a more advanced computer modeling approach. This deeper investigation provides information about the individual roles these parameters play in a younger rift region. We present results that topography has the most influence on the stress transferred to the Natron Fault in our models, and that the other parameters did not play a large role in influencing the stress transferred. Finally we work to increase the ability for researchers to perform geodetic studies in the Natron Rift by providing a new method to share surface displacement data at an unprecedented 1 position a second rate (near real-time). This new method is a data broker application called GNSS2CHORDS that can stream cm precision displacement data to an online cybertool called CHORDS. With our models and data provided through open source methods this work contributes significantly to our understanding of volcano-tectonic interactions.
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Guzman, Vendrell Montserrat. "Understanding the processes that controlled rifting of the Tyrrhenian basin." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/396372.
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This thesis is focused in the processes that took place in the Tyrrhenian Sea, which is a Neogene basin belonging to the Western Mediterranean realm. Its formation is related with the subduction system of the African plate below the European plate. The slab retreat causes a stretching of the overriding plate and triggered the opening of the Tyrrhenian basin.
The sedimentary record described in the Tyrrhenian Basin spans from early-Miocene to the most recent Pleistocene deposits. The distribution of these sediments, their geometry and their relations with the tectonic structures reflects the basin evolution throughout the time.
Oldest sediments consist in pre-Trotonian materials deposited at the Corsica and Sardinian Basins during their formation. Thus this region may have been opened previously to the Tortonian times. In fact, these basins formed as episutural basins during the early Miocene.
The Tortonian unit has only been identified at the continental areas. The rifting onset took place during the Tortonian, as suggested by the sedimentary discontinuity described within this unit. Such discontinuity marks the base of the syn-rift wedges, and it is known at the literature as the "L" discontinuity.
The Messinian deposit have been described at the continental and back-arc areas. Its presence at the Campania and Cornaglia Terraces (back-arc areas), where no Tortonian has been found suggest that they were formed in some moment during the early Messinian. But, in fact, Messinian strata show a clear post-rift character in these areas. Thus both terraces are provably formed during the Tortonian, concurrently to the rifting processes of the North Tyrrhenian.
Thus, in the North Tyrrhenian extension occurred through rifting processes, leading to rotated blocks that can be well appreciated at the bathymetry. North-south trend of these blocks suggest that extension direction was mainly east-west.
While at the same time, at the Cornagla and Campania Terraces, extensional processes become more complex. Continental extension took place in the southern Cornaglia, while at the center, at the north and at the Campania Terrace back-arc magmatic crustal accretion occurred. Instead, in the southern Cornaglia Terrace a limited amount of magmatic crustal accretion occurred.
Finally, according to sedimentary syn-rift geometries, extension continued in all these areas during the Messinian, although extensional processes become attenuated.
The Pliocene deposits are the first unit that can be found everywhere, including the deepest areas of the Vavilov and Magnaghi Basins. It has been divided into two sub-units and the discontinuity between them is known as the "X" discontinuity, and marks the end of this extensional stage. The Magnaghi Basin may have opened during the uppermost Messinian, as suggested by the pre-rift Messinian evaporites observed at the western half
of this basin. Then, in a short time lapse, extensional locus continues its migration towards the east and the Vavilov basin opened at the lower Pliocene. Opening of these two basisn may have occurred during a short period as suggested by the absence of synrift deposits in the area. At the same time, extensional processes at the continental and back-arc regions ceased completely, as suggested by the intra-Pliocene unconformity. It implies that the former magmatic extensional regime changed to an essentially amagmatic extension. Finally, at the boundary between the Pliocene-Pleistocene a new jump in the extensional locus occurred. As in the former case, a new basin opened: the Marsili Basin. Concurrently, in a certain moment during the upper Pliocene, transpression- transtensional tectonics started along the Italian Margin region related with this trench migration towards the south-east, and reactivated the former extensional faults.Esta tesis está centrada en los procesos que tuvieron lugar en el mar Tirreno, el cual es una cuenca Neógena perteneciente al Dominio del Mediterraneo Occidental. Su formación está relacionada con el sistema de subducción de la placa Africana por debajo de la placa Europea. El retroceso del slab da lugar a un estiramiento en la placa superior provocando la apertura de la cuenca del Tirreno. El registro sedimentario descrito en el Tirreno abarca desde el Mioceno inferior hasta el Pleistoceno mas reciente. La distribución de estos sedimentos, su geometría y su relación con las estructuras tectónicas reflejan la evolución de formación de la cuenca a lo largo del tiempo. De acuerdo con la interpretación tectónica y la distribución de los depósitos sedimentarios, las sub-cuencas de Córcega y Cerdeña se formaron durante el Mioceno inferior como cuencas episuturales relacionada con el frente de subducción. Durante el Tortoniense la extensión migró hacia el este y los procesos extensivos empezaron en lo que sería el actual región del Tirreno Norte dando lugar a extensión continental. Mientras que en el sur los processos extensivos tomaron un carácter mas complejo que en el norte. En las zonas de Cornaglia Terrace y Campania Terrace tuvo lugar la formación de corteza oceánica nueva por acreción magmática, excepto en la parte mas meridional de la Cornaglia Terrace, donde tuvo lugar extensión continental con un pequeño aporte magmático. Durante el Messiniense, los procesos extensionales se atenuaron y en el Plioceno inferior cesaron casi por completo. Mientras que al mismo tiempo la extensión migró hacia la actual cuenca de Magnaghi y la cuenca de Vavilov, donde se dio ruptura cortical y exhumación del manto. Finalmente, en el límite Plioceno-Pleistoceno la extensión cesa en esta área y vuelve a migrar hacia la actual cuenca de Marsili.
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Williams, Kimberly Michelle. "Rifting of oceanic lithosphere at transforms and trench slope seamounts /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3071023.
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Mondy, Luke. "On the dynamics of continental rifting: a numerical modelling approach." Thesis, The University of Sydney, 2019. https://hdl.handle.net/2123/21412.
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Passive margins around the world commonly feature evidence of syn-rift small scale contractional deformation, such as reverse faulting and low amplitude folding, as well as evidence of basin depth inversions. Often, these features have no corresponding change in plate motion, and seem in conflict with the kinematic understanding that areas undergoing continental rifting should record only extensional deformation and subsidence. It has been proposed that syn-rift basin inversion may form as a result of gravitational body forces developing because of the upwelling asthenospheric dome beneath the rifted region, known as rift push. The aim of this thesis is to investigate the role these gravitational forces can play on the evolution of passive margins during rifting, and to quantify the role the upwelling asthenosphere plays in this process. To achieve this, we use high-resolution thermomechanical numerical modelling in both two and three dimensions, with non-linear, temperature, stress, and strain-dependent rheologies, to map the evolution of the stress regime throughout the lithosphere as the margins develop. Two dimensional numerical experiments show that the upwelling asthenosphere is capable of driving rift opening, and that transient compressional stress of up to 30 MPa develop within localized regions of the passive margin. When coupled with simplified surface processes allowing the formation of sedimentary basins, the experiments show that rift basins can undergo multiple phases of compression with no change to the applied rift kinematics, as they tend to localise compressive stress. We also explore the role of rift-push in the fundamentally three-dimensional context of continental rifting close to an Euler pole. It has been proposed that diachronous upwelling of the asthenosphere could induce compressional structures along the strike of the rift axis. Our experiments show that as the asthenosphere reaches break-up earlier at one end of the rift, a component of rift-push force is orthogonal to the rift axis (as per the previous experiments), and a second component is parallel to the rift axis, as the relatively unthinned areas of lithosphere are juxtaposed against the upwelled asthenospheric dome along the strike of the rift. In combination, these force components produce transcurrent and compressional stress within the developing passive margins, which matches earthquake focal mechanism data from similar realworld examples. Finally, to facilitate the access of thermo-mechanical modelling to a broader community of structural geologists and tectonicists, we have designed a prebuilt toolbox named the Lithospheric Modelling Recipes which includes a customizable 2D and 3D lithospheric model. In doing so, we aim to a) give structural geologists and tectonicists a user-friendly self-consistent framework to test their conceptual ideas, b) expand the pool of expertise and ideas tapping into geodynamic modelling, and c) enable a large number of geoscientists to critically assess geodynamic models, and d) contribute to the reproducibility of thermo-mechanical modelling.
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Hamling, Ian. "Measuring and modelling deformation during the Dabbahu (Afar) rifting episode." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/1926/.
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In September 2005, a 60-km-long dyke intruded the Dabbahu segment of the Nubia-Arabia plate boundary (Afar, Ethiopia), marking the beginning of an ongoing rifting episode. Continued activity has been monitored using Satellite Radar Interferometry, GPS instruments and seismometers deployed around the rift in response to the initial intrusion. These data show that a sequence of 12 new dyke intrusions have reintruded the central and southern section of the Dabbahu segment. Modelling of InSAR data indicates the dykes were between 0.5 and 3 m wide, up to 10 km long and confined to the upper 10 km of crust. Seismicity data imply that the dykes were probably fed from a source near the centre of the segment. The new dykes are concentrated in areas where the 2005 dyke did not produce significant opening, implying that residual tensile tectonic stresses are higher in this location and are focusing the later intrusions. Geodetic data, which quantify the location and extension occurring in each of the events, allows the identification of regions where tensile stress has been increased. Here I demonstrate for the first time the high probability of a link involving stress transfer and dyke intrusions. Since the September 2005 intrusion, background displacement rates are significantly larger than the average secular divergence between Nubia and Arabia. Some of this deformation can be explained using viscoelastic models, which suggest an elastic crustal thickness of 13 km and upper mantle viscosity of 10 ^18.5 Pas. The presence of multiple magmatic sources around the rift zone, however, cause large residuals between the data and model suggesting that viscoelastic relaxation alone cannot account for the observed deformation. It is likely that, with a continued magma supply, dykes will continue to be intruded until the tectonic stress is fully relieved with more eruptions as the rifting episode is concluded.
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Olierook, Hugo K. H. "Tectono-stratigraphic evolution during rifting of the southwestern Australian margin." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/595.
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Basin development and magmatism on the southwestern Australian margin are profoundly affected by continental breakup. Before and after breakup, sedimentary basins experienced regime switches in: fluvial-dominated to paralic sedimentation; paleo-drainage and provenance from south–north to east–west, and; locally heterogeneous subsidence and exhumation driven by tectonic events to more regionally homogeneous subsidence and exhumation driven predominantly by epeirogenesis. The breakup of eastern Gondwana resulted in coeval magmatism, driven by the Kerguelen mantle plume.
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Kinabo, Baraka Damas. "Incipient continental rifting: insights from the Okavango Rift Zone, northwestern Botswana." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/kinabo_09007dcc.8048de9a.pdf.
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Thesis (Ph. D.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 4, 2008) Includes bibliographical references.
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Sajjad, Noman. "Structural restoration of Mesozoic rifting phases in the northern North Sea." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23650.
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Structural restoration has been carried out on the northern North Sea (60-62ºN), based on the reprocessed, interpreted and depth converted seismic lines NSDP84-1 and 2. Two major rifting events have previously been recognized in the area during the Mesozoic: the Permo-Triassic and Jurassic extension phases. Different structures were formed or, in some cases, the same structures were reactivated during the Permo-Triassic and Jurassic rifting phases. Permo-Triassic rifting affected a 125 km wide area from the Oygarden Fault Zone in the east to the Hutton Fault alignment in the west.. By measuring the length of the profiles before and after faulting, the restorations show that the stretching factors for upper crustal stretching during the Permo-Triassic rifting are 1.11 (11%) for NSDP84-1 and 1.10 (10%) for NSDP84-2 respectively. The Jurassic rifting was confined to a narrower zone mainly in the Viking Graben with the major faults formed on the western side of the graben. Low angle faults are identified in the western flank of Viking Graben in the Tampen Spur area. Low angle supra-basement detachments formed in the late Jurassic are found in Gullfaks area, beneath the Gullfaks Sør block and SE of the Visund fault block. Intra-basement detachments are also found in Tampen Spur area. These detachments are formed by normal faults which flatten in the basement. From the restorations, the stretching factor for the Jurassic rifting is calculated to be 1.12 (12%) for NSDP84-1 and 1.19 (19%) for NSDP84-2. The total extensions for the two rifting phases combined are 1.24 (24%) and for NSDP84-1 and 1.30 (30%) for NSDP84-2. Stretching factors (β) can also be measured by crustal thickness changes, stretching is measured before and after rifting for different area (Horda Platform, Shetland Platform, Viking Graben, and Tampen Spur), and βmean calculate for the Permo-Triassicxrifting phase are calculated 1.25 and 1.16 for NSDP84-1 and 2 respectively. For the Jurassic rifting βmean is calculated as 1.16 for NSDP84-1 and 1.17 for NSDP84-2. These values are similar to previous published results using the same methods in the Northern North Sea and represent the minimum amounts of upper crustal extension on large seismically resolved faults.
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Agustsdottir, Thorbjorg. "The 2014-15 Bárðarbunga-Holuhraun magmatic rifting episode : a seismic study." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/279679.
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On 16 August 2014 an unusual sequence of earthquakes began near the southeastern rim of the ice-covered Bárðarbunga caldera in central Iceland. Over the course of two weeks a dyke propagated 48 km beneath the glacier northeastwards and into the Holuhraun lava field, where it erupted for six months, becoming the largest eruption in Iceland for over 200 years. During this time, a gradual, incremental caldera collapse took place in the central volcano. The rifting episode was captured both geodetically and seismically. In this thesis, I analyse the seismic response to the event, both due to the dyke propagation, and the subsequent caldera collapse. This gives an insight into the underlying processes controlling rifting events, and the nature of the responding crust. The Cambridge seismic network recorded the 2014-15 Bárðarbunga-Holuhraun rifting episode in exceptional detail. I discuss the deployment and operation of this dense seismic network in the remote Icelandic highlands, as well as the campaign deployments on the volcano caldera, on the glacier (above the dyke path) and around the eventual eruption site, as a first response to the crisis. Using this dataset I have accurately located, and analysed, 47,000 earthquakes during the pre-intrusive, intrusive, eruptive and post-eruptive periods. Approximately 4,000 of the recorded earthquakes are associated with the caldera collapse, delineating faults accommodating the subsidence and showing good correlation with geodetic data. The seismicity reveals activation of both inner and outer caldera faults with 60 inward dipping planes on the northern and southern side, indicating a symmetric caldera structure. Detailed analysis of the earthquake source mechanisms shows that 90% can be explained by a double-couple solution, which is in contrast to results from previous studies of Bárðarbunga. I find the dominant failure mechanism during the collapse to be steep normal faulting, with sub-vertical P-axes, striking sub-parallel to the caldera rim. The northern and southern sides of the caldera, however experienced very different seismicity rates, highlighted by the order of magnitude difference in the cumulative seismic moments. The southeastern part of the caldera, whilst experiencing less activity, shows a mixture of failure mechanisms, owing to the interaction of the caldera collapse and the dyke exit. Therefore, this thesis presents evidence of a complex asymmetric caldera collapse, not controlled by a single caldera ring fault. Of the 47,000 earthquakes located, 31,000 delineate the segmented, lateral dyke intrusion as it fractured a pathway through the crust, utilizing pre-existing weaknesses. Despite the extensional rift setting, the dyke emplacement generated exclusively doublecouple earthquakes. At the leading edge of the propagation, earthquake source mechanisms show exclusively strike-slip faulting, in contrast to the conventional model of normal faulting above a propagating dyke. I observe right-lateral strike-slip faulting as the dyke propagates to the NE, and an abrupt change to left-lateral strike-slip faulting as the dyke turns and propagates in a more northerly direction into the northern volcanic zone. This shows that the direction of fault motion is determined by the opening of the dyke, rather than by the regional extension. I am also able to define the thickness of the seismogenic crust under Bárðarbunga as 7 km, based on the depth extent of observed seismicity. The bulk of the seismicity in the volcano is located at 1-4 km below the surface, whereas the dyke exited the caldera at 4-6 km depth, propagating at 6-8 km b.s.l. I hypothesise that the magma storage region is likely located at 4-6 km b.s.l. (6-8 km below the caldera surface), just below the most active caldera seismicity and at similar depth levels to the dyke. Thus, this thesis details the melt distribution and movement at depth from a large basaltic central volcano, and the coupled deformation of the subsiding caldera with the dyke intrusion and eruption.
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Claudel, Marie-Elisabeth. "Reconstitution paléogéographique du domaine briançonnais au Mésozoïque : ouvertures océaniques et raccourcissements croisés." Phd thesis, Grenoble 1, 1999. http://tel.archives-ouvertes.fr/tel-00509949.
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La zone briançonnaise est issue d'un domaine de la marge passive de la Téthys ligure, qui a émergé au Jurassique. Elle est actuellement située au cœur de l'arc alpin entre la zone externe et les autres zones internes. L'évolution particulière de ce domaine pose le problème de sa localisation paléogéographique au sein de la marge passive. En effet, les séries briançonnaises des Alpes occidentales (Sud et du Pelvoux) montrent les traces de déformations anté-alpines antérieures ou postérieures au rifting jurassique de la Téthys ligure. L'analyse des marqueurs structuraux (failles normales, filons, hard-ground, ...) contenus dans la sédimentation associée aux études classiques de sédimentologie, stratigraphie et de micropaléontologie permettent d'établir une chronologie précise des évènements extensifs, de caractériser ces paléostructures et de mettre au jour l'évolution du domaine briançonnais tout au long du Mésozoïque et du Cénozoïque. Des variations d'épaisseurs de l'unité lithologique des « Calcaires rubanés » du Ladinien inférieur impliquent une subsidence différentielle d'origine tectonique (période antérift). Des phénomènes de dissociation trouvés à la limite Ladinien-Carnien pourraient correspondre à des ébranlements sismiques contemporains d'une structure syn-rift précoce de la plate-forme triasique. A partir de l'analyse diagénétique d'échantillons prélevés au niveau de la surface d'émersion, il semble que la lacune débute au Sinémurien supérieur sur l'aire de Peyre-Haute. Le rifting téthysien comprendrait 2 phases : au Carnien et au Sinémurien (surrection). En Briançonnais, 2 aires de subsidence distinctes discernables sur des courbes de subsidence ont donc été mises en évidence pour cette période. L'effondrement « post-rift » de la pate-forme briançonnaise au Bathonien supérieur est suivi par une nouvelle structuration au Callovien-Oxfordien créant de nouvelles failles [Claudel et al., 1997]. Les périodes d'activité tectonique du Crétacé sont surtout marquées par des réactivations de failles : à l'Aptien-Albien et au Turonien supérieur. Les brèches du Campanien-Maastrichtien pourraient s'être déposées en contexte de convergence. L'analyse structurale montre l'existence de chevauchements hors-séquences au sein de l'édifice de nappes briançonnaises : la direction de chevauchement des charriages éocènes seraient obliques (vers le nord ?) par rapport aux charriages vers l'ouest oligocènes. La 1ère mise en place de nappes (Peyre-Haute et Prorel) est superficielle et marquée par des olistostromes (Eychauda, Queyrelets). L'analyse paléomagnétique préliminaire [Thomas et al., soumis] suggère une rotation anti-horaire d'une quarantaine de degrés postérieure à toutes les phases de plissements post-nappes de l'ensemble de la zone briançonnaise étudiée. Le dépliage des unités tectoniques, prenant en compte la rotation et les transports vers le nord, a permis de proposer une reconstitution paléogéographique régionale qui replace le domaine briançonnais au sein du Sud Est de la France dans le prolongement est de la Provence jusqu'au Jurassique supérieur. Replacées dans le contexte géodynamique globale, ces structurations successives croisées au niveau du domaine briançonnais pourraient résulter d'interférences entre les cycles de rifting-ouverture océanique suivants décalés dans l'espace et dans le temps [Claudel & Dumont, soumis] : système Halstatt-Méliata au Ladinien inférieur ; système Atlantique Central-Téthys ligure au Carnien-Lias ; système Atlantique Nord-Golfe de Gascogne-domaine valaisan au Callovien-Oxfordien. La plate-forme triasique enregistrerait tout d'abord l'écho du rifting de l'océan Halstatt au Ladinien, puis subit le 1er stade du rifting téthysien dès le Ladinien supéruer-Carnien. La phase principale survenant au Lias se traduit en domaine briançonnais par une surrection ; ce qui permet d'admettre que ce domaine constituait l'épaulement du rift téthysien [Stampfi, 1993]. Après l'ouverture initiale de l'océan Téthysien ligure, le rifting valaisan oblique par rapport à la ride médio-téthysienne continue de structurer le domaine briançonnais situé dès lors à l'intersection de 2 zones de rupture crustale. Le Wombat plateau au large de l'Australie a subit une évolution de ce type et fournit une image analogue à celle proposée pour le domaine briançonnais au Mésozoïque.
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Johnson, Nicholas Edward. "Magnetotelluric studies of the crust and upper mantle in a zone of active continental breakup, Afar, Ethiopia." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7739.
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The Afar region of Ethiopia is slowly being torn apart by the Red Sea, Gulf of Aden and Main Ethiopian rifts which all meet at this remote, barren corner of Africa. Prior to rifting, volcanism probably started here some 30 million years ago, marked by the arrival of the Afar mantle plume and subsequent eruption of kilometres thick flood basalts. To the north and east the Red Sea and Gulf of Aden rifts have already progressed to become sea-floor spreading centres where new oceanic crust is produced. Active spreading on the Red Sea rift takes a landward step west into Eritrean Afar at approximately 15oN, after which divergence between the Nubian and Arabian tectonic plates is localised into 60 km long, 20 km wide magmatic segments that undergo periodic rifting cycles. This part of Afar is a unique natural laboratory where the process of transition from continental rifting to sea floor spreading can be studied. In September 2005 a dramatic rifting episode began on one such segment of the Red Sea rift in Afar (the Dabbahu magmatic segment), whereby a 60 km long dyke containing an estimated 2.5 km3 magma was intruded in just two weeks, allowing opening of up to 8 m. Since then a further 13 smaller dykes have been intruded, some with fissural eruptions of basaltic lava. Subsidence observed via geodetic observations can only account for a small fraction of the magma supply required to in ate the dykes, suggesting a deep crustal or upper mantle source must exist. The magnetotelluric (MT) method is a passive geophysical technique, used to probe the Earth to reveal subsurface conductivity. The presence of fluids can dramatically increase conductivity by orders of magnitude making the MT method ideally suited to detecting them. MT data collected from 22 sites on profiles near to and crossing the active rift are analysed and interpreted in conjunction with seismic and petrological constraints. They reveal for the first time, the existence of both a mid to lower-crustal magma chamber directly below the rift, and an o -axis zone of partial melt well within the mantle. The volume of melt contained within the crust and upper mantle below the Dabbahu segment is estimated to be at least 350 km3; enough to supply the rift at current spreading rates for almost 30 thousand years, assuming that both melt containing regions supply the rift. Vast amounts of highly conductive material, suggesting the existence of pure melt in places, are also required in the shallow crust close to Dabbahu volcano which lies at the northern end of the segment. Further data collected on the currently inactive Hararo segment which is the next one to the south of Dabbahu, show a smaller zone of partial melt that appears to be pooling at the Moho, inferred seismically to be at about 22 km, but little or no melt is required within the mid-crust. The minimum amount of melt estimated to be contained here is just 21 km3; an order of magnitude less than on the Dabbahu segment, but similar to estimates for melt within the crust found below the rift axis in the continental Main Ethiopian rift. This, along with other morphological evidence, suggests that this rift segment is less mature than the Dabbahu segment to the north, rather than it simply being at a different stage of a rifting cycle. A wide spread layer of highly conductive sediments up to 2 km thick has been imaged at most locations. This was unexpected on the Dabbahu segment where the surface of the Earth is dominated by heavily faulted basalts erupted from fissures, which are seen as a resistive uppermost layer several hundred metres thick. The high conductivity of the sediments is attributed to high heat flow and the presence of brines.
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Halama, Ralf. "Petrologische und geochemische Untersuchungen an Magmatiten der Gardar-Provinz, Südgrönland." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10910388.
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Beniest, Anouk. "From continental rifting to conjugate margins : insights from analogue and numerical modelling." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066289/document.
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Les marges conjuguées de l'Atlantique Sud sont le produit du rifting et de la rupture du continent Pangée. Ce continent présente une hétérogénéité crustale et lithosphérique importante, dont la prise en compte est un objectif de la thèse. Afin de comprendre la rupture continentale à l'échelle lithosphérique de systèmes de rhéologies préexistantes très différentes, nous avons effectué des modélisations, analogique et numérique. Les modèles analogiques s'attachent à montrer l'effet des forces externes sur un tel système hétérogène tandis que les modèles numériques, thermomécaniques, se concentrent sur l'impact des anomalies de fusion du manteau sur le rifting avec une telle configuration.Avec la modélisation analogique, l'effet des forces aux limites sur un système composé de deux segments de rhéologies différentes a été testé à l’échelle de la lithosphère pour comprendre l'influence de l'hétérogénéité rhéologique dans un système en extension. Les résultats montrent que dans un système combiné, toute l'extension se produit dans le segment faible et que le contact entre les deux segments ne joue pratiquement aucun rôle dans l'initiation des failles. Lorsque le segment le plus faible contient une couche résistante dans le manteau supérieur, le rift évolue en deux phases. La première phase montre un système de failles larges où la déformation est distribuée. Une fois que la partie résistante du manteau supérieur est suffisamment affaiblie, l'extension se localise le long d'une zone de faille étroite. Si l'extension continuait, la rupture se produirait à cet emplacement, dans une partie plutôt homogène alors que le système est latéralement hétérogène. Le résultat de ce système extensif serait des marges asymétriques avec une croûte faible/hyper-étirée sur deux marges.Les résultats numériques montrent que, dans le cas de la rupture continentale induite par un panache, le mode de rupture «central», où la rupture se localise au-dessus du point de l'impact du panache, est une forme de rupture continentale parmi d'autres. Ainsi, lorsque l'anomalie de fusion du manteau est localisée de manière décalée par rapport au contact entre les segments rhéologiques, un mode de rupture "décalé" peut se développer. Dans ce cas, le matériel du panache atteint la base de la lithosphère et s’écoule latéralement jusqu’au contact entre les deux segments rhéologiques où le rifting se localise in fine. La partie du matériel qui n’arrive pas au centre de la zone de rupture, se situe au niveau de la croûte inférieure ou bien plus profond, ressemblant aux corps de densité/vitesse élevées imagés le long des marges de l'Atlantique Sud. De plus, le mode «décalé» reproduit l'asymétrie des marges conjuguéesThe South Atlantic conjugate margins are the product of continental rifting and break-up of Pangea, which was made up of different crustal features prior to rifting. This study investigates continental rift initiation and break-up of alternative lithospheric setups, consisting of large segments with different rheological strength, with the use of analogue and numerical modelling. The analogue models investigate the effect of far-field forces on a system that consist of multiple rheological segments, whereas the numerical models include thermal processes and focus on the impact of initial plume emplacement on such a setup.Lithosphere-scale analogue models consisting of two different rheological compartments have been subjected to extensional forces, to understand effect of far-field forces on large rheological heterogeneities in a system within an extensional tectonic regime. The results show that in such a system, the weaker segment accommodates all the extension. At the contact between the two compartments no rift-initiation is observed. In the presence of a strong sub-Moho mantle, the rift evolution consists of two phases. The first phase is a wide or distributed rift event. Once the strong part of the upper mantle has sufficiently weakened, the rift localizes and a narrow rift continues to accommodate the extension. If extension would continue, break-up would happen at the location of the narrow rift, thereby breaking a rather homogenous part within a laterally heterogeneous system. This would result in asymmetric margins with hyperextended, weak crust on both margins.The numerical results show that, in the case of plume-induced continental break-up, the classical ‘central’ mode of break-up, where the break-up centre develops above the plume-impingement point is not the only form of continental break-up. When the mantle anomaly is located off-set from the contact between rheological segments, a ‘shifted’ mode of break-up may develop. In this case, the mantle plume material rises to the base of the lithosphere and migrates laterally to the contact between two rheological segments where rifting initiates. Mantle material that does not reach the spreading centre and remains at lower crustal depths, resemble high density/high velocity bodies at depth found along the South Atlantic margin and providing geometric asymmetry.Further investigation on the exact influence of the initial plume position with respect to the contact between the rheological compartments shows that there is a critical distance for which the system develops either ‘central’ (or ‘plume-induced’) continental break-up or ‘shifted’ (or ‘structural inherited’) continental break-up. For Moho temperatures of 500 – 600 oC, there is a window of ~50 km where the system creates two break-up branches. These results explain complex rift systems with both vertical penetration of plume material into the overlying lithosphere as well as reactivated inherited structures developing break-up systems both aided by the same mantle plume
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Lee, Martin Joseph. "Contrasting sources of palaeozoic mafic dykes during intracratonic rifting in central Australia /." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09SB/09SBl4791.pdf.
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Kirstein, Linda A. "Magmatism in southern Uruguay and the early rifting of the South Atlantic." Thesis, Open University, 1997. http://oro.open.ac.uk/57700/.
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A suite of early Cretaceous vo1canic rocks (Puerto GOmez and Arequita FIm.) are preserved within the N60° E trending Santa Lucia Basin, southern Uruguay which lies at the southern margin of the Parana - Etendeka continental flood basalt province. New Ar- Ar ages of the basalts range from 134 to 130 Ma while ages from the rhyolites range from 130 to 124 Ma. This magamtism was contemporaneous with the main flood basalt event, although rhyolite activity continued after rifting (127 - 126 Ma). The province therefore contains unique information about melting conditions at the periphery of the influence of the Tristan da Cunha plume. The volcanic rocks of southern Uruguay are bimodal in silica, and the majority of basalts of the Puerto G6mez Fm., herein termed the Treinte Y Tres magma type, have major-, trace- element and initial isotope ratios similar to the low -TiIY Gramado -Tafelberg magma types of the Paranl- Etendeka. There are also a number of unique basalt samples termed the Santa Lucfa magma type. which have low LaINb, and are considered to have been generated by mixing between lithosphere - and asthenosphere - derived melts. These magmas represent the first sampling of true plume material in this CFB province. The rhyolites of the Arequita Fm. are relatively evolved with variably sized euhedraI to anbedral quartz phenocrysts, and ignimbritic textures that are the first described from this province. The rhyolites have lower magmatic temperatures (8S0 - 950°C) than those of the Parana - Etendeka, and are divided into two geochemical series, the Lascano Series and the Aigtia Series. The rhyolites of the Lascano and AigUa Series are not related to the Puerto G6mez Fm. basaks, but rather they originated from separate sources in the mid to lower crust. where melting was facilitated by mid-crustal level intrusions of basaJtic material as recognised from a large gravity anomaly. Melt production rates in southern Uruguay were low (0.01 Jan3 yrl) similar to the rates ca1cuIated for the waning stages of magmatism on the Serra Geral escarpment, southern Brazil. These rates are consistent with the notion that by this time the principal melt production was located in the newly forming ocean with Uruguay at the margins of the influence of the plume.
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Woods, Jennifer. "Dyke-induced earthquakes during the 2014-15 Bárðarbunga-Holuhraun rifting event, Iceland." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289448.
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Understanding dykes is vital as they serve both as bodies that build the crust and as conduits that feed eruptions. The 2014-15 Bárðarbunga-Holuhraun rifting event comprised the best-monitored dyke intrusion to date and the largest eruption in Iceland in 230 years. Over a 13 day period magma propagated laterally from the subglacial Bárðarbunga volcano, Iceland, along a 48 km path before erupting in the Holuhraun lava field on 29 August 2014. A huge variety of seismicity was produced, including over 30,000 volcano-tectonic earthquakes (VTs) associated with the dyke propagation at ∼ 6 km depth below sea level, and long-period seismicity - both long-period earthquakes (LPs) and tremor - associated with the eruption processes. The Cambridge University seismic network in central Iceland recorded the dyke seismicity in unprecedented detail, allowing high resolution analyses to be carried out. This dissertation comprises two parts: study of 1) the volcano-tectonic dyke-induced seismicity and 2) the long-period seismicity associated with eruption processes. Volcano-tectonic earthquakes induced by the lateral dyke intrusion were relocated, using cross-correlated, sub-sample relative travel times. The ∼ 100 m spatial resolution achieved reveals the complexity of the dyke propagation pathway and dynamics (jerky, segmented), and allows us to address the precise relationship between the dyke and seismicity. The spatio-temporal characteristics of the induced seismicity can be directly linked in the first instance to propagation of the tip and opening of the dyke, and following this - after dyke opening - indicate a relationship with magma pressure changes (i.e. dyke inflation/deflation), followed by a general 'post-opening' decay. Seismicity occurs only at the base of the dyke, where dyke-imposed stresses - combined with the background tectonic stress (from regional extension over > 200 years since last rifting) - are sufficient to induce failure of pre-existing weaknesses in the crust, while the greatest opening is at shallower depths. Emplacement oblique to the spreading ridge resulted in left-lateral shear motion along the distal dyke section (studied here), and a prevalence of left-lateral shear failure. Fault plane strikes are predominately independent of the orientation of lineations delineated by the hypocenters, indicating that they are controlled by the underlying host rock fabric. Long-period earthquakes and tremor were systematically detected and located during the dyke propagation phase and the first week of the eruption. Clusters of highly similar, repetitive LPs were identified, with a peak frequency of ∼ 1 Hz and clear P and S phases followed by a long-duration coda. The source mechanisms were remarkably consistent between clusters and also fundamentally different to those of the VTs. The clusters were accurately located near each of three ice cauldrons (depressions formed by basal melting) that were observed on the surface of Dyngjujökull glacier above the path of the dyke. Most events were in the vicinity of the northernmost cauldron, at shallower depth than the VTs associated with lateral dyke propagation. At the two northerly cauldrons, periods of shallow seismic tremor following the clusters of LPs were also observed. Given that the LPs occurred at ∼ 4 km depth and in swarms during times of dyke-stalling, it is inferred that they result from excitation of magmatic fluid-filled cavities and indicate magma ascent. The tremor may then represent the climax of the vertical melt movement, arising from either rapid, repeated excitation of the same LP cavities, or sub-glacial eruption processes. This long-period seismicity therefore highlights magma pathways between the depth of the dyke-VT earthquakes and the surface. Notably, no tremor is detected associated with each cauldron, despite melt reaching the base of the overlying ice cap, a concern for hazard forecasting.
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Autin, Julia. "Déchirure continentale et segmentation du Golfe d'Aden Oriental en contexte de rifting oblique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00633368.
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Le Golfe d'Aden sépare la plaque Somalie de la plaque Arabie. Il constitue un objet d'étude intéressant pour la compréhension du développement des marges continentales passives. Le rifting débute vers 35 Ma et l'accrétion se développe à partir de 17,6 Ma dans la zone étudiée. De plus, la direction d'ouverture du Golfe d'Aden est fortement oblique par rapport à sa direction. Sur la marge nord-est, la campagne Encens (N/O l'Atalante, 2006) a permis l'acquisition de nouvelles données de sismique réflexion 360 traces, notamment sur le segment de premier ordre entre les zones de fracture d'Alula-Fartak et de Socotra. À la segmentation de premier ordre (zones de fracture) s'ajoute une segmentation de second ordre qui présente des structures et des morphologies différentes selon les segments, notamment au niveau de la transition océan-continent (TOC). Les segments étudiés suggèrent que la partie ouest de la zone d'étude (segment d'Ashawq-Salalah) est caractérisée par un magmatisme post-rift conséquent tandis que la partie orientale de la zone d'étude (segment de Mirbat) possède une morphologie qui semble être fortement tectonisée. L'évolution tectono-stratigraphique du segment d'Ashawq-Salalah a pu être étudiée en détail (migration avant sommation profondeur et corrélation terre-mer des processus sédimentaires). La marge est tout d'abord structurée par des grabens et des horsts syn-rift. Puis on observe une localisation de la déformation sur la marge distale. Au début de la formation de la TOC, un soulèvement local ou régional induit un glissement de terrain au sommet du horst le plus distal. La déformation crustale est alors localisée dans la TOC, où la rupture continentale va finalement se produire. La nature de la TOC pourrait être du manteau serpentinisé, postérieurement intrudé par du matériel magmatique pendant la période post-rift. La couverture sédimentaire à proximité de la TOC montre qu'elle subit une surrection pendant le post-rift en relation avec la mise en place d'un volcan et des coulées et sills associés. Cette évolution peut être comparée aux modèles d'évolution les plus récents des marges passives. La marge conjuguée (au sud-est du Golfe d'Aden) présente la même segmentation que la marge nord-est (d'Acremont et al., 2005). Une analyse microstructurale de l'île de Socotra (marge sud émergée) permet de comparer les marges et de mieux contraindre le rifting oblique. Comme sur la marge nord, les directions des failles normales sont réparties en trois familles : N110°E perpendiculaire à l'extension, N70°E parallèle à la direction du Golfe, N90°E intermédiaire. L'inversion des données microstructurales montre des directions d'extension en accord avec les trois familles de failles. Des chronologies sont observées depuis une direction d'extension N20°E vers N160°E et réciproquement. Les variations de la direction d'extension suggèrent une alternance des champs de contraintes pendant la phase de rifting du Golfe d'Aden. Des modélisations analogiques dans le Golfe d'Aden ont permis de mieux cerner son développement en rifting oblique. Les horsts et les grabens sont disposés en échelons, avec des formes sigmoïdes. Les trois familles de failles liées à l'obliquité sont observées : N110°E, N90°E et N70°E. L'évolution des directions des failles montre une dominance des failles N90°E et N110°E au début de l'extension puis le développement plus tardif de failles N70°E et ce, avec ou sans la présence initiale d'une hétérogénéité oblique à l'extension. Enfin des failles N110°E sont de nouveau formées. Le modèle conceptuel de Bellahsen et al. (2006) serait donc applicable pour les premiers stades d'évolution : la réactivation de bassins N110°E et la formation de nouvelles failles en échelons s'effectuent sous la direction d'extension des plaques (N20°E) depuis 35 Ma. Puis l'amincissement de la lithosphère se poursuivant le long de la direction du Golfe (N70°E), les contraintes locales dues aux variations latérales d'épaisseur provoquent la formation de failles N70°E et la réactivation de failles N110°E. La chronologie d'extension N20°E puis N160°E observée sur les marges est donc expliquée. Nous proposons une troisième étape : une fois l'amincissement du rift suffisamment important, les contraintes locales ne s'exercent que sur les bords du rift ou sur les horsts majeurs. Partout ailleurs des failles N110°E sont formées et les failles N70°E sont réactivées de manière oblique. La seconde chronologie d'extension N160°E puis N20°E des études microstructurales est aussi expliquée. Les horsts peuvent subir des rotations horaires importantes qui induisent des zones de cisaillement senestres. Elles pourraient initier les nombreuses zones de transfert concordant avec la forte segmentation du le Golfe d'Aden.
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Illsley-Kemp, Finnigan McGowan. "Crustal processes associated with the final stages of continental rifting in northern Afar." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/425897/.
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The transition from continental rifting to seafloor spreading is a key, yet enigmatic, stage of the plate tectonic Wilson Cycle. The Danakil region in the northern Afar depression marks the transition between late-stage continental rifting in the Main Ethiopian rift, and young seafloor spreading in the Red Sea, it is thus an ideal location to investi- gate the final stages of continental breakup. Here, the southern Red Sea rift steps on land and the active processes associated with continental breakup are exposed subaeri- ally. Between February 2011 and February 2013, two seismic networks were installed in northern Ethiopia and Eritrea. In this thesis, continuous seismic data is used to detect and locate 4951 earthquakes and investigate how seismicity accommodates ex- tension and deformation as the region transitions to seafloor spreading. Results show that seismicity is focused at the rift axis and within a graben on the western rift margin. Seismicity at the rift axis accounts for ∼64% of the total seismic moment release and reveals a lower crustal magma complex beneath the Alu-Dalafilla volcanic system. This suggests that the majority of mechanical extension is focused at the rift axis, as is observed in the Main Ethiopian rift. However, seismic moment release rate shows that extension is predominantly accommodated though magmatism and this produces stacked sill magma plumbing systems, analogous to those seen at mid-ocean ridges. In contrast to the Main Ethiopian rift, high levels of seismicity are observed at the western rift margin. Earthquake focal mechanisms and seismic anisotropy show that extension in the marginal graben is oriented E-W, oblique to extension at the rift axis. The seis-micity here predominantly occurs on an antithetic fault, extending to depths of ∼20 km. Large, antithetic faults have been observed in rifted margins worldwide, this research suggests such structures may form and remain active in the final stages of continen- tal rifting. In addition, seismological data is combined with remote structural geology, geodetic observations and three-dimensional thermomechanical numerical modelling to show that an oceanic transform fault is initiating in the Danakil depression. This is the first direct observation of this process and demonstrates that these oceanic structures can initiate in the final stages of continental rifting, prior to seafloor spreading. The findings of this thesis reveal that many processes and structures which are associated with seafloor spreading can form during the final stages of continental breakup. Thus, the continent-ocean boundary must not be treated as a discrete point in space or time.
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Autin, Julia. "Déchirure continentale et segmentation du Golfe d’Aden oriental en contexte de rifting oblique." Paris 6, 2008. http://www.theses.fr/2008PA066274.
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Le Golfe d'Aden oriental constitue un objet d'étude intéressant pour la compréhension du développement des marges passives peu volcaniques. Le rifting débute vers 35 Ma et l'accrétion s’initie à partir de 17,6 Ma. La direction d'ouverture du Golfe d'Aden est oblique par rapport à son axe. Les directions des failles normales sont réparties en trois familles. Cette étude repose sur trois types de données : sismique réflexion, analyse microstructurale et modélisation analogique. La migration avant sommation profondeur d’un profil et la corrélation des unités sismiques en mer avec les séquences sédimentaires à terre permettent de proposer l'évolution tectono-stratigraphique d’un segment de second ordre, avec une transition océan-continent constituée de manteau serpentinisé puis intrudée par du matériel magmatique post-rift. Un nouveau modèle d’ouverture du golfe permet d’expliquer les chronologies relatives entre les différentes extensions à l’origine des trois directions de failles.
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Collanega, Luca. "Polymodal faulting in rifting settings: strain field and role of pre-existing structures." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426232.
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Normal faults have been typically thought to develop sub-perpendicularly to the extension direction, forming systems of sub-parallel faults. However, a variety of processes may result in the simultaneous development of faults with different strikes (i.e. polymodal faulting), most notably 3D strain fields and influence of pre-existing fabrics. Whilst the classic model on faulting suggests that complex fault patterns should result from polyphase deformation with different extension directions, the concept of polymodal faulting can account for the development of different fault sets under the same stress regime, having possibly a strong impact on the reconstruction of the palaeostress.
In the thesis, 3D seismic data were used to assess the occurrence of polymodal faulting in two different extensional tectonic settings: the Barents Sea rift-shear margin (Paper 1), offshore northern Norway, and the Taranaki back-arc rift (Paper 3), offshore New Zealand. Then, analogue models and kinematic analysis were used to investigate the deformation processes. In both settings, polymodal faulting was observed at the 10s of kilometres scale. The occurrence of polymodal faulting at such large scale may affect the previous interpretation of the structural histories of these sedimentary basins, reducing the number of tectonic phases that should be envisaged to explain the observed structures.
The tectonic setting appears to have a strong influence on the deformation processes, with polymodal faulting occurring under the control of a 3D strain field in the Barents Sea and of pre-existing basement fabrics in the Taranaki Basin. In the Barents Sea, the onset of a 3D strain field is related to the interaction between the Atlantic and the Arctic rifts, coupled with a characteristic brittle-ductile-brittle mechanical stratigraphy. The analogue models performed in this thesis (Paper 2) highlighted that in 3D strain fields, local fault interactions exert a strong control on the final fault geometries, with the faults forming perpendicular one to the other rather than in orthorhombic symmetry with respect to the principal strain axes as previously thought. In the Taranaki back-arc rift, despite the absence of extensional reactivation of the intra-basement structures, they appear to have exerted a strong control on the distribution and strike of normal faults. The growth history of normal faults highlighted that preferential nucleation/propagation within pre-existing weakness zones and local perturbation of the regional stress field may be effective mechanisms through which pre-existing structures can influence normal faults, even without their direct extensional reactivation.
In conclusion, complex fault patterns may not necessarily reflect a complex tectonic history, but can result from the dynamics of deformation processes, which appear to be strongly susceptible to the local influences of developing as well as pre-existing structures.Il modello classico della fagliazione (ovvero la teoria di Mohr-Coulomb) prevede che in un regime estensionale le faglie si formino perpendicolarmente alla direzione di estensione, dando luogo a sistemi di faglie sub-parallele fra loro. Tuttavia, una varietà di meccanismi possono portare allo sviluppo simultaneo di faglie con diverse orientazioni, detto fagliazione polimodale. In particolare, campi di strain 3D e l’influenza da parte di strutture pre-esistenti potrebbero portare allo sviluppo simultaneo di diversi sistemi di faglie in modo pervasivo e su ampia scala. A differenza del modello classico della fagliazione, il concetto di fagliazione polimodale può pertanto spiegare lo sviluppo simultaneo di diversi sistemi di faglie nell’ambito di un unico campo di stress. Adottare un modello o l’altro può dunque avere un impatto drastico sulla ricostruzione dell’evoluzione tettonica di un’area. In questa tesi, si sono usati dati sismici 3D per valutare il presentarsi di fagliazione polimodale in due diversi contesti tettonici estensionali: il Mare di Barents (Articolo 1), un margine di rift-shear al largo della Norvegia Settentrionale, ed il Bacino del Taranaki (Articolo 3), un rift di retro-arco al largo della costa occidentale della Nuova Zelanda. Successivamente, i dati sismici sono stati integrati con modelli analogici e dettagliate ricostruzioni della storia cinematica di specifici piani di faglia al fine di meglio comprendere i meccanismi deformativi. In entrambi i contesti, la fagliazione polimodale è stata osservata alla scala delle decine di chilometri, suggerendo la rilevanza di questo processo in termini tettonici. Il verificarsi di fagliazione polimodale ad ampia scala implicherebbe infatti una riduzione del numero di fasi tettoniche necessarie per giustificare le strutture osservate, modificando l’attuale visione dell’evoluzione strutturale di questi bacini sedimentari. Il confronto fra le due aree suggerisce che il contesto tettono-stratigrafico giochi un ruolo fondamentale sui meccanismi alla base della fagliazione polimodale. Nel caso del Mare di Barents, la fagliazione polimodale risulta essere l’espressione di un campo di strain 3D legato all’interazione fra rifting Artico e Atlantico; sebbene anche il disaccoppiamento fra deformazione superficiale e profonda dovuto ai livelli con reologia duttile sembra essere stato un fattore fondamentale. Nel caso del Bacino del Taranaki, invece, la fagliazione polimodale sembra essere avvenuta sotto il controllo di strutture profonde, ereditate da fasi tettoniche compressive precedenti al rifting. La ricostruzione dei processi deformativi nelle due aree ha portato a rivedere i modelli esistenti della deformazione 3D (nel caso del Barents) e dell’eredità strutturale (nel caso del Taranaki). Da una parte, i modelli analogici della deformazione 3D (Articolo 2) hanno evidenziato come le faglie tendano a svilupparsi perpendicolarmente le une alle altre, piuttosto che con simmetria ortorombica rispetto agli assi della distensione, come previsto dal modello classico di Reches (1978). Questa tesi suggerisce pertanto che le interazioni locali tra faglie siano il principale meccanismo di controllo sulle geometrie finali in campi di strain 3D. Dall’altra parte, lo studio del Taranaki ha posto in luce come strutture profonde del basamento cristallino possano esercitare una notevole influenza sulla distribuzione e orientazione delle faglie normali, malgrado l’assenza di una diretta riattivazione estensionale delle stesse. La nucleazione/propagazione preferenziale delle faglie normali da anisotropie pre-esistenti e perturbazioni locali del campo di stress regionale sembrano essere meccanismi alternativi alla riattivazione estensionale, attraverso cui strutture pre-esistenti possono esercitare una forte influenza sulle faglie normali. In conclusione, questa tesi dimostra che sistemi di faglie complessi non necessariamente sono legati ad una complessa storia strutturale, consistente di molteplici fasi tettoniche. La complessità dei processi deformativi, ed in particolare la suscettibilità di questi a strutture pre-esistenti o in fase di formazione, può infatti spiegare lo sviluppo di sistemi di faglie complessi anche nell’ambito di un'unica fase tettonica.
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Mohn, Geoffroy. "L' évolution tectono-sédimentaire des marges de la Téthys Alpine au cours de l'amincissement lithosphérique." Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/MOHN_Geoffroy_2010.pdf.
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La compréhension des mécanismes responsables de l’extension lithosphérique est un enjeu majeur pour la caractérisation des processus de la déchirure continentale. En effet, les mécanismes d’extension lithosphérique permettant l’amincissement de la croûte continentale restent méconnus. Les données acquises dans les marges passives actuelles précisent que la phase majeure d’amincissement se produit dans la zone d’étranglement (necking zone) montrant le passage d’une croûte de 30 à 10 km, à la limite entre marge proximale et distale. Le manque de données dans les marges actuelles ne permet pas de répondre avec précision à ces questions. De ce fait l'étude est focalisée sur les nappes Austroalpines de Bernina-Campo-Grosina dans les Alpes. Ces nappes préservent les reliques de la "necking zone" de la marge fossile Adriatique. Les résultats montrent qu’au sein de la necking zone : 1) l’amincissement est accommodé par un système couplé de détachements crustaux permettant l’exhumation de croûte supérieure et inférieure 2) les niveaux crustaux intermédiaires sont interprétés comme représentant un découpleur entre la croûte supérieure et inférieure 3) la présence d’une zone d’extraction permet l’omission de la croûte moyenne. L’amincissement crustal résulte donc de l’exhumation et de l’extrusion de croûte moyenne dans la "necking zone" tandis que la marge distale est caractérisée par la juxtaposition de croûte supérieure et inférieure. Enfin le manteau sous-continental sera exhumé le long de détachements coupant la croûte continentale préalablement amincie. Ces résultats permettent par analogie une meilleure compréhension de l’architecture des marges passives actuellesA long-standing problem in Earth Sciences is to understand how continents break apart to form new oceanic basins. Many of the questions that currently frame ongoing debates about continental break-up are related to the mechanics of extreme lithospheric extension. Observations from many present-day rifted margins revealed that the transition from continental crust that underwent minor thinning in proximal margins to hyper extended crust in distal margins occurs within a necking zone. The low resolution of offshore data makes it difficult to study the structures and processes associated with crustal thinning in present-day systems. We focused our study on the Austroalpine Bernina-Campo-Grosina units exposed in the Alps, which preserve relics of the former necking zone of the Adriatic rifted margin. Within this necking zone, high-strain shear zones responsible for lithospheric thinning can be defined including: 1) a system of conjugate low-angle shear zones/detachment faults active in the brittle upper crust and lower crust 2) mid-crustal decollements decoupling the deformation in the upper and lower crust 3) an extraction shear zone, whose activity resulted in the total excision of the middle crust. These high-strain zones are interpreted to accommodate crustal thinning from 30 to 10 km during Toarcian time. Thinning resulted in exhumation of mid-crustal rocks in the necking zone, while in the distal margin upper and lower crust are juxtaposed and overprinted by late detachment faults that cut across the thinned crust and exhume mantle rocks to the seafloor. These structures can explain the first-order crustal architecture observed at many present-day rifted margins
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Peron-Pinvidic, Gwenn. "Morphotectonique et architecture sédimentaire de la transition océan-continent de la marge ibérique." Université Louis Pasteur (Strasbourg) (1971-2008), 2006. https://publication-theses.unistra.fr/public/theses_doctorat/2006/PERON-PINVIDIC_Gwenn_2006.pdf.
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La plupart des idées conceptuelles sur l'architecture sédimentaire et l'évolution tectonique des marges passives profondes sont fondées sur des études de rifts continentaux ou de marges proximales. Le problème est que, au contraire des marges distales, ces domaines n'ont subi que de faibles taux d'extension. Le travail de thèse présenté dans ce manuscrit a eu pour but d'analyser plus précisément l'architecture de ces marges distales. Il s'est concentré sur le segment central de la marge ouest Ibérique: la Plaine Abyssale Ibérique Sud (PAIS). J'y ai étudié l'évolution des structures de rifting, spatialement et temporellement, en me basant sur une cartographie détaillée de l'architecture sédimentaire et de socle en 3D sur des profils de sismique réflexion. L'évolution polyphase des processus tectoniques de la phase finale du rifting a pu y être identifiée. Les mécanismes d'extension changent du sud au nord de la PAIS depuis des zones de manteau exhumé par des failles de détachement concaves vers le bas à des demi-grabens classiques formés par le basculement normal de blocs continentaux le long de failles de détachement concaves vers le haut. Sur la base de ces résultats, j'ai pu développer un modèle conceptuel pour l'évolution 3D de la PAIS. Ce modèle suggère une migration générale de l'activité de faille normale vers le futur océan et un changement dans le mode d'extension latéralement à la marge, imagé par un changement de géométrie des structures tectoniques. Ces résultats ont des conséquences importantes pour l'approche théorique de la formation d'une marge passive distale. Par exemple, les concepts de breakup continental et de discordance sédimentaire de breakup, censés caractériser le début de l'accrétion océanique, se révèlent en définitive inadaptés: le rifting est fondamentalement polyphase et poly-processus avec une évolution graduelle vers l'océanisation et non une limite temporelle ou spatiale continent-océan cartographiableMost of the conceptual ideas concerning sedimentary architecture and tectonic evolution of deep rifted margins are based on either continental rifts or proximal margins, both of which underwent only small amounts of crustal thinning. In my PhD thesis I investigated the sediment and basement architecture of the distal magma-poor rifted margin in the Southern Iberia Abyssal Plain (SIAP). The spatial and temporal evolution of the rifting structures have been studied, based on a detailed mapping of the sedimentary and basement architecture in 3D on seismic reflection profiles. The polyphase evolution of the final phase of rifting has been identified and described. The data suggest that the extensional mechanisms change from south to north within the SIAP from zones of mantle exhumed via downward concave detachment faults to classical half-grabens formed by the normal tilting of continental blocks along upward concave detachment faults. On the base of these results, I developed a 3D conceptual model for the SIAP evolution. This model suggests a general migration of normal fault activity during final break-up towards the future ocean and a change in the fault geometry during final rifting. This 3D evolution of rifting in deep margins is described for the first time and has important implications for the interpretation of seismic sections from OCT as well as for the interpretation of the deformation processes at distal margins. The concepts of continental breakup and the breakup unconformity, supposed to characterise the beginning of oceanic accretion, are not applicable to Iberia-type margins. At these margins, rifting is fundamentally polyphase and includes various modes of extension that evolve and superpose in time and space migrating and finally localizing in the area of final seafloor spreading
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Bremer, Florian Heinrich. "Karoo rifting im Morondava Becken, Madagaskar: fazielle Entwicklung, Kinematik und Dynamik eines polyphasen Riftbeckens." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975019910.
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Pérez, Gussinyé Marta. "Continental rifting and break-up at the West Iberia margin : an integrated geophysical study /." [S.l. : s.n.], 2000. http://e-diss.uni-kiel.de/diss_380/.
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McMahon, Neil Andrew. "The role of uplifts in the rifting and sedimentation history of the N. Atlantic." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/11145.
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The synthesis and integration of existing biostratigraphic and sedimentological information from exploration wells in the circum-Atlantic region with recent developments in genetic sequence stratigraphic techniques and computer modelling has allowed the documentation of uplifts and the rifting history of the North Atlantic during the Late Jurassic and Early Cretaceous and has led to a better understanding of the history of N. Atlantic extension. Correlation of the Late Mesozoic stratigraphy between the Lusitanian, Celtic Sea Area, Wessex, Jeanne d'Arc, Faeroe/Shetland Basins and the Rockall Trough areas has resulted in the identification of the main unconformities/uplifts to have affected the N. Atlantic. This has permitted a new understanding for the evolution of the N. Atlantic and the mechanisms of rifting. Up to four major unconformities were identified along the Grand Banks/Iberian Margin during the Oxfordian to Valanginian period. The Late Kimmeridgian and Middle Berriasian unconformities caused the greatest amount of erosion and are associated with uplift events interpreted from vitrinite reflectance data, sedimentation and erosion patterns. These events are thought to be related to the sea floor spreading in the Tagus abyssal plain and the establishment of a new N. Atlantic rift axis in the Early Cretaceous. In the Celtic Sea Area and Wessex Basins a major intra-Cretaceous unconformity has been identified and it is interpreted to be associated with an uplift event which was heralded by a Late Jurassic regression and climaxed in the Berriasian. The uplift, interpreted from subsidence, AFTA and erosion data, was centred on the granites of the Cornubian Platform and peaked after the initiation of rifting in the Late Jurassic and before the emplacement of oceanic crust west of Goban Spur in the Aptian/Albian. The younger regional correlatable "Base Gault unconformity", to which the older event is normally linked, is related to crustal separation in the Bay of Biscay and can be dated as Early/Mid Albian.
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Bennett, Scott Edmund Kelsey Oskin Michael. "Transtensional rifting in the late proto-Gulf of California near Bahía Kino, Sonora, México." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2761.
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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Mar. 10, 2010). "... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Geological Sciences." Discipline: Geology; Department/School: Geological Sciences. Includes color plate.
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Michielini, Erica. "Geometrie deposizionali del Bacino del Browse formatesi durante il rifting del margine Nord-Ovest australiano." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Il Bacino del Browse è parte del margine Nord-occidentale australiano e la sua evoluzione è legata a episodi multipli tettonici, verificatisi dal paleozoico, che hanno strutturato questo margine e i vari sottobacini che lo compongono. L'interpretazione di 16 profili sismici, ubicati nel bacino del Browse, e calibrati tramite dati di pozzo, sono la base principale di questo studio.
L’obiettivo principale di questo lavoro è il riconoscimento delle geometrie deposizionali ed evoluzione tettonica del bacino avvenuta durante il rifting del margine NO australiano fino alla breakup continentale. Le geometrie deposizionali riscontrate comprendono le sequenze syn-rift permo-carbonifere, post-rift permo-triassiche e syn-rift giurassiche. Sono quindi state evidenziate le prime 7 sequenze già riscontrate da Geoscience Australia nel 1997 a cui sono associate 8 principali unconformity. Le quattro differenti fasi (Estensione 1, Subsidenza termica 1, Inversione 1 e Estensione 2), subite dal bacino, hanno plasmato la formazione del Browse andando anche ad influenzare la sedimentazione successiva. In particolare è risultato che, durante la fase estensionale paleozoica, nel bacino si formarono i suoi due maggiori depocentri cioè il Sottobacino del Barcoo e del Caswell. Durante la fase estensionale giurassica, preceduta da un evento di subsidenza termica e da una fase di inversione, la sedimentazione ha in alcuni casi ribattuto su antichi depocentri e in altri casi ne ha creati di nuovi andando quindi ad attuare una riorganizzazione all'interno dell’area di studio. L’evoluzione geologica del Bacino del Browse si è anche dimostrata adatta per la formazione e l’accumulo degli idrocarburi: i Direct Hydrocarbon Indicators (DHIs) riscontrati potrebbero infatti confermare sia la presenza di fluidi, prevalentemente nel Sottobacino del Caswell, sia la loro migrazione verso Est cioè verso l’attuale Piattaforma Yampi.
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LEROY, Marie. "Mécanismes de déformation post-rifting des marges passives. Exemple des marges péri-atlantiques et modélisation." Phd thesis, Université Rennes 1, 2004. http://tel.archives-ouvertes.fr/tel-00008495.
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Les marges passives présentent de nombreux indices de déformations postérieures à l'épisode de subsidence thermique, successif au rifting. Parmi ces déformations, la plus argumentée dans la littérature est la surrection, bien reconnue sur les marges nord-ouest européennes, ouest africaines, sud-ouest brésiliennes et indiennes. Elle est responsable d'une topographie élevée, ainsi que de perturbations importantes des systèmes sédimentaires marins et continentaux (identifiables sur images satellitaires). Des indices d'une tectonique récente en raccourcissement (plissements, failles...) sont également décrits sur ces marges et les données de sismicité, de mouvements de plaques tectoniques (DORIS), et des indications géologiques sont en faveur de contraintes compressives actuelles sur les marges passives péri-atlantiques Les causes suggérées de ces déformations sont diverses. Facteurs climatiques, tectonique régionale, ridge-push, point chaud, etc, sont envisagés dans la littérature. La modélisation nous permet de tester l'influence de certains de ces mécanismes sur la surrection et/ou le style et la localisation de la déformation. Le raccourcissement tectonique et l'influence des point-chauds ont ainsi été testés grâce à la modélisation analogique. Il en découle que les rhéologies des lithosphères océaniques et continentales, et les contrastes de résistance et de densité existant, ont une grande influence sur le style et la localisation des déformations. Un modèle numérique 2D en éléments finis nous permet de connaître l'influence de la thermicité initiale sur la déformation observée après le breakup. Ce modèle démontre notamment qu'une surrection des marges passives peut être induite par leur évolution thermique et que cette surrection est plus importante pour les marges volcaniques que pour les marges non-volcaniques. La rhéologie aura quant à elle une grande influence sur le style et la localisation de la déformation en compression, lorsque la marge est soumise à un raccourcissement horizontal. Il résulte de ces observations et modélisations que la déformation récente des marges passives est liée à des associations différentes de mécanismes selon chaque marge. Cependant certains mécanismes pourraient favoriser ces déformations (ridge-push ou contrainte compressive régionale, points chauds mis en place lors de leur formation ou postérieurement).
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Sautter, Benjamin. "Influence de l’héritage structural sur le rifting : exemple de la marge Ouest de La Sonde." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE015.
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Les bassins sédimentaires se développent souvent le long des zones internes d'anciennes chaînes orogéniques. Nous considérons dans ce projet la Péninsule Malaise (Marge Ouest de la Sonde) comme un haut crustal séparant deux régions de croûte continentale étirée ; les bassins d'Andaman/Malacca du côté occidental et les bassins thaïlandais/malais à l'est. Plusieurs stades de rifting ont été documentés grâce à une intense exploration géophysique régionale. Cependant, la corrélation entre les bassins riftés en mer et le noyau continental terrestre est mal connue. Dans ce mémoire, nous explorons par la cartographie, de missions de terrain et les données sismiques, comment ces structures réactivent des hétérogénéités mésozoïques crustales préexistantes. Le noyau continental semble être relativement peu déformé après l'orogénèse triasique Indosinienne. L’épais méga-horst crustal est bordé par des zones de cisaillement complexes (zones de failles de Ranong, Klong Marui et du Batholithe du Main Range) initiées au Crétacé Supérieur/Paléogène inférieur lors d’une déformation transpressive d’échelle crustale et plus tard réactivées à la fin du Paléogène. L'extension est localisée sur les bords de cette épine dorsale crustale le long d'une bande où la précédente déformation crétacée supérieure est bien exprimée. À l'ouest, le plateau continental est aminci en trois étapes principales qui correspondent à des blocs basculés d’échelle crustale bordés par de larges failles contre-régionales profondément enracinées (Bassin de Mergui). À l'est, des systèmes de rifts prononcés sont également présents, avec de grands blocs basculés (les bassins western Thai, de Songkhla et de Chumphon) qui pourraient représenter de grands boudins de croûte. Dans le domaine central, l'extension est limitée à de demi-grabens étroits isolés de direction N-S développés sur une croûte continentale épaisse, et contrôlés par failles normales pelliculaires, qui se développent souvent au contact entre les granitoïdes et l’encaissant. Les bords extérieurs des régions affectées par le boudinage crustal délimitent le bassin d'Andaman plus grand et profond à l'ouest et les bassins Malais et de Pattani à l'est. À une échelle régionale, les bassins riftés ressemblent à des structures en-échelon N-S le long de grandes bandes de cisaillement de NW-SE. Le rifting est accommodé par de larges failles normales à faible pendage (LANF : Low Angle Normal Faults) réactivant les morpho-structures de la croûte telles que de larges plis et batholithes mésozoïques. Les bassins profonds d'Andaman, Malais et de Pattani semblent situés sur une croûte à rhéologie plus faible qui pourrait être héritée des blocs continentaux dérivés du Gondwana (Birmanie, Sibumasu, et Indochine). L'ensemble des long bassins étroits au coeur de la région (bassins de Khien SA, de Krabi, et du Malacca) apparaissent avoir souffert de relativement peu d'extension. Ce travail montre que le cœur de l’orogène Crétacé supérieure est faiblement réactivé avec seulement quelques traces d’un étirement précoce par rapport aux bords qui sont sujets à un amincissement crustal en larges blocs basculés. A mesure que la déformation augmente, le rifting migre et se localise vers les zones externes et sa géométrie apparait plus « molle » suggérant un mécanisme influencé par la thermique. La coexistence de ces deux géométries au sein d’un même cycle de rifting fait de la marge Ouest de la sonde un cas d’étude édifiantSedimentary basins often develop above internal zones of former orogenic belts. We hereafter consider the Malay Peninsula (Western Sunda) as a crustal high separating two regions of stretched continental crust; the Andaman/Malacca basins in the western side and the Thai/Malay basins in the east. Several stages of rifting have been documented thanks to extensive geophysical exploration. However, little is known on the correlation between offshore rifted basins and the onshore continental core. In this paper, we explore through mapping and seismic data, how these structures reactivate pre-existing Mesozoic basement heterogeneities. The continental core appears to be relatively undeformed after the Triassic Indosinian orogeny. The thick crustal mega-horst is bounded by complex shear zones (Ranong, Klong Marui and Main Range Batholith Fault Zones) inititiated during the Late Cretaceous/Early Paleogene during a thick-skin transpressional deformation and later reactivated in the Late Paleogene. The extension is localized on the sides of this crustal backbone along a strip where earlier Late Cretaceous deformation is well expressed. To the west, the continental shelf is underlain by three major crustal steps which correspond to wide crustal-scale tilted blocks bounded by deep rooted counter regional normal faults (Mergui Basin). To the east, some pronounced rift systems are also present, with large tilted blocks (Western Thai, Songkhla and Chumphon basins) which may reflect large crustal boudins. In the central domain, the extension is limited to isolated narrow N-S half grabens developed on a thick continental crust, controlled by shallow rooted normal faults, which develop often at the contact between granitoids and the host-rocks. The outer limits of the areas affected by the crustal boudinage mark the boundary toward the large and deeper Andaman basin in the west and the Malay and Pattani basins in the east. At a regional scale, the rifted basins resemble N-S en-echelon structures along large NW-SE shear bands. The rifting is accommodated by large low angle normal faults (LANF) running along crustal morphostructures such as broad folds and Mesozoic batholiths. The deep Andaman, Malay and Pattani basins seem to sit on weaker crust inherited from Gondwana-derived continental blocks (Burma, Sibumasu, and Indochina). The set of narrow elongated basins in the core of the Region (Khien Sa, Krabi, and Malacca basins) suffered from a relatively lesser extension. This work shows that the core of the late Cretaceous Orogeny is weakly reactivated during the subsequent rifting with only few evidences of stretching whereas its sides are thinned with large tilted blocks. The rifting migrates and localizes on the external regions and its geometry appears more ductile suggesting the influence of a thermal activity in the process. The coexistence of both geometries in a single rifting cycle makes the western margin of Sundaland an enlightening example
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Shimer, Peter A. "Rifting and Inversion along the Palos Verdes Fault Zone, San Pedro Shelf, Offshore Southern California." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10784146.
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This study examines the relationship of the Palos Verdes Fault Zone (PVFZ), an important fault zone in the Inner Borderland (IB), to the Palos Verdes Anticlinorium, Wilmington Graben, and other structures through detailed mapping of the fault zone constructed from high resolution 2D and 3D seismic reflection data and well logs. The data reveal a Mohnian-Delmontian trough, controlled by rifting and predating Palos Verdes Anticlinorium uplift, along the western PVFZ boundary. Sediment growth in the trough, the bulk of which occurred during the Mohnian, locally persisted into the Repettian. The western PVFZ boundary fault then transitioned to a transpressional regime beginning during the Repettian, inverting trough sediments. Typical of transpressional restraining bends along strike-slip faulting, varying degrees of inversion occur along the fault, with moderate inversion occurring on the central shelf with areas of little to no inversion to the north and south, all bounded by extreme inversion in the Palos Verdes Peninsula to the north and Lasuen Knoll to the south.
The present location and geometry of the PVFZ with its various restraining and releasing bends, is potentially a product of the early rifting episode, which is related to other sub-parallel major IB rifts, such as San Pedro Basin, San Diego Trough, and Los Angeles Basin. At roughly 65 km long, 1-7 km wide, and 1-1.5 km deep, the PVFZ trough is much narrower than the other IB basins, except the San Diego Trough.
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Leroy, Marie. "Mécanismes de déformation post-rifting des marges passives : Exemple des marges péri-atlantiques et modélisation." Rennes 1, 2004. https://tel.archives-ouvertes.fr/tel-00008495.
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De nombreuses marges passives, et notamment celles de l'océan Atlantique, présentent des indices de déformation post-rift, caractérisée par de la surrection et du raccourcissement horizontal, qui se répercute sur la géométrie des systèmes sédimentaires. Différents mécanismes ont été envisagés dans la littérature pour expliquer ces déformations. La modélisation nous permet d'en tester certains. Le ridge-push, la tectonique régionale, l'influence des points-chauds, et de la rhéologie des marges, ont ainsi été testés grâce à des modèles analogiques et numériques. Il résulte des observations naturelles dans l'océan Atlantique et des modélisations, que la déformation récente des marges passives est liée à des associations différentes de mécanismes selon chaque marge. Cependant certains mécanismes pourraient favoriser ces déformations (ridge-push ou compression régionale, points chauds mis en place lors de leur formation ou postérieurement).
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Leroy, Marie. "Mécanismes de déformation post-rifting des marges passives : exemple des marges péri-atlantiques et modélisation /." Rennes : Géosciences-Rennes, 2005. http://catalogue.bnf.fr/ark:/12148/cb39998257g.
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Claudel, Marie-Elisabeth. "Reconstitution paléogéographique du domaine briançonnais au Mésozoïque : ouvertures océaniques et raccourcissements croisés." Grenoble 1, 1999. http://www.theses.fr/1999GRE10041.
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La zone brianconnaise est issue d'un domaine marginal de la tethys ligure, qui a emerge au jurassique. Les series brianconnaises montrent cependant les traces de deformations ante-alpines anterieures ou posterieures au rifting jurassique de la tethys ligure. L'analyse des marqueurs structuraux contenus dans la sedimentation permet d'etablir une chronologie des evenements brianconnais. Des variations d'epaisseurs du ladinien inferieur impliquent une subsidence differentielle d'origine tectonique (ante-rift). Des phenomenes de dissociation a la limite ladinien-carnien pourraient correspondre a des ebranlements sismiques contemporains d'une structuration syn-rift precoce. La lacune d'emersion debuterait au sinemurien superieur. L'effondrement post-rift au bathonien superieur est suivi par une nouvelle structuration au callovien-oxfordien. Les periodes de l'aptien-albien et du turonien superieur montrent surtout des reactivations de failles. Les breches du campanien-maastrichtien pourraient s'etre deposees en contexte de convergence. L'analyse structurale montre l'existence de chevauchements hors-sequences : la direction des charriages eocenes serait oblique par rapport aux charriages vers l'ouest oligocenes. Le paleomagnetisme suggere une rotation anti-horaire d'environ 45 de la zone brianconnaise posterieure a tous plissements post-nappes. Le depliage des nappes a permis de replacer le domaine brianconnais dans le prolongement est de la provence. Les structurations croisees au niveau du domaine brianconnais pourraient resulter d'interferences entre les cycles de rifting-ouverture successifs : halstatt-meliata au ladinien inferieur ; atlantique central-tethys ligure au carnien-lias ; atlantique nord-golfe de gascogne-valaisan au callovien-oxfordien. Par comparaison avec le wombat plateau (australie), le domaine brianconnais serait situe au jurassique superieur a l'intersection de deux zones de rupture crustale : l'ocean tethys ligure et le rift valaisan.
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Möller, Stefan [Verfasser]. "Rifting in the northern Tyrrhenian Sea Basin: a multichannel and wide-angle seismic study / Stefan Möller." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1036637891/34.
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Rajaonarison, Tahiry Andriantsoa. "A Geodynamic Investigation of Continental Rifting and Mantle Rheology: Madagascar and East African Rift case studies." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/102410.
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Continental rifting is an important geodynamic process during which the Earth's outer-most rigid shell undergoes continuous stretching resulting in continental break-up and theformation of new oceanic basins. The East African Rift System, which has two continentalsegments comprising largely of the East African Rift (EAR) to the West and the easternmostsegment Madagascar, is the largest narrow rift on Earth. However, the driving mechanismsof continental rifting remain poorly understood due to a lack of numerical infrastructure tosimulate rifting, the lack of knowledge of the underlying mantle dynamics, and poor knowl-edge of mantle rheology. Here, we use state-of-art computational modeling of the upper660 km of the Earth to: 1) provide a better understanding of mantle flow patterns and themantle rheology beneath Madagascar, 2) to elucidate the main driving forces of observedpresent-day∼E-W opening in the EAR, and 3) to investigate the role of multiple plumesor a superplume in driving surface deformation in the EAR. In chapter 1, we simulate EdgeDriven convection (EDC), constrained by a lithospheric thickness model beneath Madagas-car. The mantle flow associated with the EDC is used to calculate induced olivine aggregates'Lattice Preferred Orientation (LPO), known as seismic anisotropy. The predicted LPO isthen used to calculate synthetic seismic anisotropy, which were compared with observationsacross the island. Through a series of comparisons, we found that asthenospheric flow result-ing from undulations in lithospheric thickness variations is the dominant source of the seismicanisotropy, but fossilized structures from an ancient shear zone may play a role in southern
Madagascar. Our results suggest that the rheological conditions needed for the formationof seismic anisotropy, dislocation creep, dominates the upper asthenosphere beneath Mada-gascar and likely other continental regions. In chapter 2, we use a 3D numerical model ofthe lithosphere-asthenosphere system to simulate instantaneous lithospheric deformation inthe EAR and surroundings. We test the hypothesis that the∼E-W extension of the EAR isdriven by large scale forces arising from topography and internal density gradients, known aslithospheric buoyancy forces. We calculate surface deformation solely driven by lithosphericbuoyancy forces and compare them with surface velocity observations. The lithosphericbuoyancy forces are implemented by imposing observed topography at the model surfaceand lateral density variations in the crust and mantle down to a compensation depth of 100km. Our results indicate that the large-scale∼E-W extension across East Africa is driven bylithospheric buoyancy forces, but not along-rift surface motions in deforming zones. In chap-ter 3, we test the hypothesis that the anomalous northward rift-parallel deformation observedin the deforming zones of the EAR is driven by viscous coupling between the lithosphereand deep upwelling mantle material, known as a superplume, flowing northward. We testtwo end-member plume models including a multiple plumes model simulated using high res-olution shear wave tomography-derived thermal anomaly and a superplume model (Africansuperplume) simulated by imposing a northward mantle-wind on the multiple plumes model.Our results suggest that the horizontal tractions from northward mantle flow associated withthe African Superplume is needed to explain observations of rift-parallel surface motions indeforming zones from GNSS/GPS data and northward oriented seismic anisotropy beneaththe EAR. Overall, this work yields a better understanding of the geodynamics of Africa.Doctor of Philosophy
Continental rifting is an important geodynamic process during which the Earth's outer-most rigid shell undergoes continuous stretching resulting in continental break-up and theformation of new oceanic basins. The East African Rift System, which has two continentalsegments comprising largely of the East African Rift (EAR) to the West and the easternmostsegment Madagascar, is the largest narrow rift on Earth. However, the driving mechanismsof continental rifting remain poorly understood due to a lack of numerical infrastructure tosimulate rifting, the lack of knowledge of the underlying mantle dynamics, and poor knowl-edge of mantle rheology. Here, we use state-of-art computational modeling of the upper660 km of the Earth to: 1) provide a better understanding of mantle flow patterns and themantle rheology beneath Madagascar, 2) to elucidate the main driving forces of observedpresent-day∼E-W opening in the EAR, and 3) to investigate the role of multiple plumesor a superplume in driving surface deformation in the EAR. In chapter 1, we simulate EdgeDriven convection (EDC), constrained by a lithospheric thickness model beneath Madagas-car. The mantle flow associated with the EDC is used to calculate induced olivine aggregates'Lattice Preferred Orientation (LPO), known as seismic anisotropy. The predicted LPO isthen used to calculate synthetic seismic anisotropy, which were compared with observationsacross the island. Through a series of comparisons, we found that asthenospheric flow result-ing from undulations in lithospheric thickness variations is the dominant source of the seismicanisotropy, but fossilized structures from an ancient shear zone may play a role in southern Madagascar. Our results suggest that the rheological conditions needed for the formationof seismic anisotropy, dislocation creep, dominates the upper asthenosphere beneath Mada-gascar and likely other continental regions. In chapter 2, we use a 3D numerical model ofthe lithosphere-asthenosphere system to simulate instantaneous lithospheric deformation inthe EAR and surroundings. We test the hypothesis that the∼E-W extension of the EAR isdriven by large scale forces arising from topography and internal density gradients, known aslithospheric buoyancy forces. We calculate surface deformation solely driven by lithosphericbuoyancy forces and compare them with surface velocity observations. The lithosphericbuoyancy forces are implemented by imposing observed topography at the model surfaceand lateral density variations in the crust and mantle down to a compensation depth of 100km. Our results indicate that the large-scale∼E-W extension across East Africa is driven bylithospheric buoyancy forces, but not along-rift surface motions in deforming zones. In chap-ter 3, we test the hypothesis that the anomalous northward rift-parallel deformation observedin the deforming zones of the EAR is driven by viscous coupling between the lithosphereand deep upwelling mantle material, known as a superplume, flowing northward. We testtwo end-member plume models including a multiple plumes model simulated using high res-olution shear wave tomography-derived thermal anomaly and a superplume model (Africansuperplume) simulated by imposing a northward mantle-wind on the multiple plumes model.Our results suggest that the horizontal tractions from northward mantle flow associated withthe African Superplume is needed to explain observations of rift-parallel surface motions indeforming zones from GNSS/GPS data and northward oriented seismic anisotropy beneaththe EAR. Overall, this work yields a better understanding of the geodynamics of Africa.
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Han, Liang. "Seismic imaging and thermal modeling of active continental rifting processes in the Salton Trough, Southern California." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/78906.
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Continental rifting ultimately creates a deep accommodation space for sediment. When a major river flows into a late-stage rift, thick deltaic sediment can change the thermal regime and alter the mechanisms of extension and continental breakup. The Salton Trough, the northernmost rift segment of the Gulf of California plate boundary, has experienced the same extension as the rest of the Gulf, but is filled to sea level by sediment from the Colorado River. Unlike the southern Gulf, seafloor spreading has not initiated. Instead, seismicity, high heat flow, and minor volcanoes attest to ongoing rifting of thin, transitional crust.
Recently acquired controlled-source seismic refraction and wide-angle reflection data in the Salton Trough provide constraints upon crustal architecture and active rift processes. The crust in the central Salton Trough is only 17-18 km thick, with a strongly layered but relatively one-dimensional structure for ~100 km in the direction of plate motion. The upper crust includes 2-3 km of Colorado River sediment. The basement below the sediment is interpreted to be similar sediment metamorphosed by the high heat flow and geothermal activity. Meta-sedimentary rock extends to at least 7-8 km depth. A 4-5 km thick layer in the middle crust is either additional meta-sedimentary rock or stretched pre-existing continental crust. The lowermost 4-5 km of the crust is rift-related mafic magmatic material underplated from partial melting in the hot upper mantle.
North American lithosphere in the Salton Trough has been almost or completely rifted apart. The gap has been filled by ~100 km of new transitional crust created by magmatism from below and sedimentation from above. These processes create strong lithologic, thermal, and rheologic layering. Brittle extension occurs within new meta-sedimentary rock. The lower crust, in comparison, stretches by ductile flow and magmatism is not localized. This seismic interpretation is also supported by 1D thermal and rheological modeling. In this passive rift driven by far-field extensional stresses, rapid sedimentation keeps the crust thick and ductile, which delays final breakup of the crust and the initiation of seafloor spreading.Ph. D.
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Giannerini, Gérard. "Propagation des phénomènes tectoniques et volcaniques liée aux zones de rifting : exemple de la plaque arabique." Nice, 1988. http://www.theses.fr/1988NICE4188.
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Étude des déformations cénozoïques et du volcanisme associé, à la bordure ouest de la plaque arabique. Mise en évidence du caractère fissural du volcanisme, relations étroites entre volcanisme et déformations intraplaques, propagation du couple déformation-volcanisme. Évolution au cours du Cénozoïque du champ des contraintes. Proposition d'évolution géodynamique de la plaque arabique et d'un mécanisme d'initiation des rifts intracontinentaux et leur évolution en rifts céramiques. Mécanisme caractérisé par une propagation polygonale de transformantes intracontinentales divergentes, provoqué par la pénétration de la ride océanique medio-indienne au sein du continent afro-somalien (golfe d'Aden)
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Giannerini, Gérard. "Propagation des phénomènes tectoniques et volcaniques liée aux zônes de rifting exemple de la plaque arabique /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37613902g.
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Hemelsdaël, Romain. "Évolution spatio-temporelle du couplage entre système fluviatile et rifting : étude du rift de Corinthe (Grèce)." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0141/document.
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Le comportement des rivières au cours du rifting joue un rôle important dans la sédimentation syn-rift et la distribution de la subsidence. Pendant la croissance des failles normales, les rivières répondent aux mouvements verticaux. En réponse au soulèvement tectonique, les rivières peuvent être déviées vers les zones en subsidence ou inversées. Les rivières peuvent aussi inciser les zones en soulèvement. L'évolution à long terme des rivières et leurs enregistrements stratigraphiques restent mal documentés pendant les processus de croissance et de migration des failles normales. Cette thèse analyse les interactions entre les rivières antécédentes et la croissance des réseaux de failles normales. Les implications en termes de distribution des faciès syn-rift sont étudiées à l'échelle du bassin et des blocs de failles. Les dépôts fluviatiles et deltaïques sont préservés dans plusieurs blocs de failles normales soulevés le long de la marge sud du rift de Corinthe (Grèce). Les logs sédimentaires et la cartographie des faciès syn-rift permettent le découpage lithostratigraphique de la zone d'étude. La série syn-rift est principalement conglomératique et difficile à dater. La magnétostratigraphie et quelques marqueurs biostratigraphiques sont utilisés pour dater et corréler les dépôts entre les différents blocs de faille. L'analyse des isotopes cosmogéniques 26Al et 10Be dans les dépôts a permis la détermination d'âge d'enfouissement. L'ensemble des âges obtenus par ces différentes méthodes permet de proposer un modèle de corrélation et de reconstruire l'évolution du rift précoce entre 3,6 et 1,8 Ma environ. (1) Le système fluviatile étudié évolue à travers plusieurs blocs de failles actives. (2) Le système de drainage antécédent hérité de la chaîne hellénique est caractérisé par un flux sédimentaire important depuis le début du rifting. (3) Le système fluviatile (au moins 30 km de long) remplit le paléorelief et le flux sédimentaire dépasse largement l'accommodation créée par les failles. L'enfouissement des failles par le système fluviatile limite la création de topographie et le développement d'un réseau de drainage conséquent. (4) L'axe fluviatile antécédent reste constant et contrôle la distribution des faciès. (5) Les changements de faciès et les architectures alluviales sont observés à l'échelle du bassin et ne sont pas directement contrôlés par les variations d'accommodation dans les blocs de failles. (6) Les zones d'accommodation maximale sont ici disposées parallèlement à l'axe fluviatile antécédent. La persistance des rivières et le flux sédimentaire pendant plusieurs centaines de milliers d'années ont permis la localisation de la déformation, induisant une rétroaction positive sur la croissance des failles. Le système distributaire se termine à l'est où des deltas progradent en milieu lacustre peu profond. Les systèmes de dépôts fluviatiles, deltaïques et turbiditiques actifs à l'initiation du rift de Corinthe enregistrent l'approfondissement diachrone du bassin. Le comportement des rivières antécédentes est aussi étudié à l'échelle d'une zone de relais entre deux failles bordières actuellement actives. Pendant le Pléistocène moyen et supérieur, la zone de relais a capturé la rivière antécédente de Krathis qui a construit une succession de deltas. La connexion entre les deux failles majeures est marquée par (1) des failles obliques dites "de transfert", (2) plusieurs familles de terrasses marines enregistrant le soulèvement diachrone de la rampe de relais, et (3) la migration progressive de l'accommodation vers le bassin. Cette étude permet pour la première fois de reconstruire les processus de connexion de failles sur une période 0,5 Ma. La rivière Krathis persiste au cours du développement de la zone de relais et met en évidence, une fois de plus, l'importance des rivières antécédentes dans la localisation des dépocentres majeurs dans les riftsRivers behaviour during early rifting can significantly impact on syn-rift sedimentation and the distribution of subsidence. During normal fault growth, existing rivers can be diverted toward subsiding zones. They can respond to footwall uplift either by reversing their flow or by incising into uplifting zones. Long-lived river systems and their stratigraphic record in rifts are poorly documented, not only during early fault propagation and linkage processes but also during successive migrating phases of fault activity. We investigate the interactions of major antecedent rivers with a growing normal fault system and the implications for facies distributions, both on a basin scale and at the scale of individual normal fault blocks. Along the southern margin of the western Corinth rift (Greece), the Plio-Pleistocene fluvial and deltaic successions are investigated. Syn-rift deposits are preserved in a series of uplifted normal fault blocks (10–20 km long, 3–7 km wide). Detailed sedimentary logging and high resolution mapping of the syn-rift deposits document variations of alluvial architecture across the basin and enable to define lithostratigraphic units. Magnetostratigraphy and rare biostratigraphic data are used to date and correlate the alluvial succession between fault blocks. Burial ages were tentatively determined using cosmogenic isotopes 10Be and 26Al produced in situ in quartz grains. Based on the correlation model, we reconstruct the evolution of the early western Corinth rift between about 3.6 and 1.8 Ma. (1) The transverse and antecedent Kalavryta river system flowed and deposited across a series of active normal fault blocks. (2) This river system was inherited from the Hellenide mountain belt and supplied high volumes of coarse sediments from the onset of extension. (3) As depocentres enlarged through time, the fluvial deposits progressively filled palaeorelief. A continuous braided plain developed above active buried faults and no significant consequent drainage system developed between the narrow fault blocks. (4) The main fluvial axis of the antecedent drainage persists through time and controlled facies distribution. (5) The length scale of facies transitions is greater than, and therefore not related to fault spacing. Here, along-strike subsidence variations in individual fault blocks represent a secondary contributor to the alluvial architecture. (6) The zones of maximum subsidence on individual faults are aligned across strike, parallel to the persistent fluvial axis. This implies that long-term sediment supply and loading influenced normal fault growth. Sediment supply largely outpaced local hangingwall subsidence and overfilled the early rift basin. The river system terminated eastward where small deltas are built into a shallow lake that occupied the central Corinth rift. During this time, another river system built fan deltas along the southern margin, recording diachronous deepening of the basin. The behaviour of antecedent rivers is also studied at the scale of a relay zone, that developed later in the rift history between two growing fault segments. During the Middle to Late Pleistocene, the relay zone captured the antecedent Krathis River, which deposited prograding Gilbert-type deltas. Transfer faults record progressive linkage and basinward migration of accommodation along the ramp axis, while marine terraces record diachronous uplift in their footwalls. Although early linkage occurred, the main normal faults continued to propagate until final connexion. For the first time a reconstruction of the linkage phase is presented over a period of ca. 0.5 Myr. Throughout this linkage history, the Krathis River continued to flow across the relay zone. Again, this emphasizes the role of antecedent rivers in supplying sediments and controlling the location of the major depocentres along the rift margins
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Ravi, Lokranjith K. "Cycle-up of multiple rifting event models how long does it take to reach a steady state stress /." Lexington, Ky. : [University of Kentucky Libraries], 2005. http://lib.uky.edu/ETD/ukymeen2005t00234/newranjiththesis.pdf.
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Thesis (M.S.) --University of Kentucky, 2005.Title from document title page (viewed on August 17, 2005). Document formatted into pages; contains: x, 107 p. : col. ill. Includes abstract and vita. Includes bibliographical references (p. 104-106).
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Haji, Toshiki. "Miocene intra-arc rifting in SW Japan: Tectonostratigraphy of the Hokutan Group and the paleostress analyses of dike orientations." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/253101.
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京都大学0048
新制・課程博士
博士(理学)
甲第22265号
理博第4579号
新制||理||1657(附属図書館)
京都大学大学院理学研究科地球惑星科学専攻
(主査)教授 山路 敦, 教授 田上 高広, 教授 生形 貴男
学位規則第4条第1項該当
Doctor of Science
Kyoto University
DGAM
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Caméra, Laurent. "Structure profonde de la marge passive égyptienne au large du Nil : contribution des données de sismique multitrace et de gravimétrie." Paris 6, 2006. http://www.theses.fr/2006PA066344.
Full textAbstract:
La marge continentale égyptienne est un segment de la marge passive africaine. En 2002, 1800 km de MCS ont été acquises le long de 7 lignes régionales. Un traitement sismique standard a permis d’imager les structures profondes et a montré la présence d’importants bassins sédimentaires profonds. La PSDM, selon deux techniques, a permis de mieux évaluer l’épaisseur sédimentaire et crustale ainsi que l’architecture de ce segment de marge. L’épaisseur des sédiments (mésozoïques à actuels) varie entre 10 et 15 km, recouvrant une croûte amincie (10 à 12 km). Localement, des réflecteurs profonds peuvent indiquer le Moho. Par ailleurs, à l’intérieur de ces sédiments, la breack-up unconformity est datée de l’Aptien, ce qui fait du rifting nilotique un événement tardif. Des données gravimétriques ont permis de mieux contraindre les structures profondes, comme la transition entre la croûte continentale égyptienne et la croûte continentale amincieThe Egyptian continental margin is a segment of the passive margin of Africa. In 2002, 1800 km of MCS data have been recorded along 7 regional lines. The use of standard processing seismic has allowed to better image of the deep structures and has particularly shown that deeply sedimented basins exist. PSDM, using two processing, has allowed to better evaluate the real sedimentary and crust thickness and to better asses the margin global architecture. The thickness of the sedimentary layers (Mesozoic and subsequent deposits) varies between 10 to 15 km covering a thinned crust (10 to 12 km). Locally, deep reflectors may indicate the Moho. In addition, within the sedimentary unit, the nilotic breack-up unconformity is dated from Aptian, consequently, the nilotic rifing is considered as a late event. A set of gravity data has allowed to better constraint the deep structures as the transition between continental crust and thinned crust
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Keir, Derek. "Strain accommodation by magmatism and faulting as rifting proceeds to breakup : seismicity of the Northern Ethiopian Rift." Thesis, Royal Holloway, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436114.
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