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Travan, Gaia. "Interactions between salt tectonics and crustal tectonics in the Mediterranean and in the Barents sea." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR050.
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À l'échelle des temps géologiques, le comportement du sel peut être approché d'un fluide newtonien (comportement visqueux) par rapport au comportement fragile des roches environnantes. La tectonique crustale, extensive et compressive, joue souvent un rôle fondamental dans l'évolution des structures salines et devient la principale cause de déformation dans de nombreuses zones d'étude. Le but de cette thèse est d'analyser le calendrier et les mécanismes de la tectonique salifère dans trois zones d'étude caractérisées par différents âges du sel et l'influence croissante de la tectonique crustale sur la tectonique salifère : la marge sarde occidentale et algérienne septentrionale (Méditerranée occidentale) et le bassin de Sørvestsnaget (mer de Barents sud-ouest). Cela a été fait par l'interprétation de données de réflexion sismique 2D et 3D de TGS (Norvège), OGS (Italie) et UMR Geo-Ocean (France), ainsi que par l'intégration avec d'autres données géophysiques et la comparaison avec des modèles analogiques. Dans la Méditerranée occidentale, le sel déposé pendant la crise de salinité (5,6 Ma) est relativement jeune, la couverture est mince et les marques des premiers stades de déformation sont visibles. Sur la marge sarde occidentale les structures salines sont principalement dues à la pente de la base du sel, résultant de la subsidence différentielle après le remplissage de la Méditerranée à la fin de la crise. En se déplaçant vers le centre du bassin sardo-provençal, où la charge sédimentaire du Rhône Deep Sea Fan forme une lourde couverture au-dessus du sel, l'étalement par gravité domine. Bien que dans cette zone il n'y ait aucune influence de la tectonique crustale sur la déformation du sel à l'échelle régionale, nous avons reconnu sur la marge SW-sarde la présence d'une structure en fleur active pendant le Pliocène. Nous proposons qu'elle fasse partie de la North Balearic Fracture Zone, i.e. la faille de glissement dextre de l'ouverture du bassin sardo-provençal, jamais reconnue dans la région.Le secteur sud de la Méditerranée occidentale est réactivé en compression depuis 8 Ma en raison de la convergence Afrique-Europe, et cette compression s'exprime par des chevauchements sur la marge algérienne. Ici, la tectonique salifère est principalement la conséquence de la tectonique crustale, et en particulier de l'augmentation de l'énergie potentielle résultant de l'élévation localisée. Les modèles analogiques produits montrent que le soulèvement du plateau est à l'origine des variations latérales d'épaisseur de la couche saline et de la formation des minibassins polygonaux dans la zone au large d'Alger. Une composante de glissement par gravité liée à l'affaissement du bassin est présente. La troisième zone d'étude est le bassin de Sørvestsnaget dans la mer de Barents. Ici le sel permien a formé des structures qui sont le résultat de centaines de millions d'années de déformation, principalement par le diapirisme de sel réactif et actif conséquence de la tectonique extensive mésozoïque due à l'ouverture de l'océan Atlantique. Ceci a conduit à la formation de structures de sel allochtones massives et localement à leur déflation. Après la fin de l'extension de la croûte, l'influence principale sur la déformation du sel est attribuable au prisme sédimentaire glaciaire quaternaire et aux mouvements de la croûte contrôlés par glacio-isostasie, ce qui entraîne une redistribution interne dans les structures de sel allochtones comme mis en évidence par la modélisation analogique. Grâce à la diversité géologique entre les trois zones d'étude, nous offrons non seulement une vue d'ensemble des différents niveaux d'interaction entre le sel et la tectonique de la croûte, mais aussi de l'effet de la pente basale du sel et de la charge sédimentaire différentielle sur l'évolution des structures de sel, ainsi que des différents niveaux de maturité des structures de sel, des plus jeunes (par ex. salt rollers) aux plus matures (par ex. salt sheets)Considering geological times, the behaviour of the salt can be approximated to a Newtonian fluid (i.e. viscous behaviour) compared to the brittle behaviour of the surrounding rocks, and their interaction can be modelled through scaled analogue models of a viscous material and a brittle one, e.g. silicone and sand. Crustal tectonics, both extensional and contractional, have often a fundamental role in the evolution of the salt structures, and becomes the main cause of deformation in many study areas. The aim of this thesis is to analyze the timing and mechanisms of salt tectonics in three study area characterized by different salt ages and increasing influence of crustal tectonics on the salt tectonics processes: the Western Sardinian and Northern Algerian margin (Western Mediterranean) and the Sørvestsnaget Basin (Southwestern Barents Sea). This has been done through the interpretation of 2D and 3D seismic reflection data from TGS (Norway), OGS (Italy) and UMR Geo-Ocean (France), as well as through the integration with other geophysical data, wells data and the comparison with analogue models. In the W-Mediterranean the salt deposited during the Salinity Crisis (5.6 Ma) so salt tectonics is relatively young, the overburden is thin and the marks of the first stages of deformation are usually imaged. On the W-Sardinian margin the salt structures are mainly consequence of the basinward slope of the salt base, resulting from the differential subsidence after the refilling of the Mediterranean at the end of the crisis. Moving towards the center of the Sardo-Provencal basin, where the sedimentary load of the Rhone Deep Sea Fan forms a thick salt overburden, gravity spreading dominates. While in this area there is no influence of crustal tectonics on salt deformation at a regional scale, we recognized on the SW-Sardinian margin the presence of a flower structure active during Pliocene. We propose it to be part of the North Balearic Fracture Zone, i.e. the dextral strike-slip fault of the Sardo-Provençal basin opening, never recognized in the area.The southern sector of the Western Mediterranean is reactivated in compression since 8 Ma due to the Africa-Europe convergence, and this compression is expressed through thrusts on the Algerian margin. Here salt tectonics is mainly the consequence of crustal tectonics, and in particular of the increased potential energy consequence of the localized uplift. The analogue models produced show that the uplift of the plateau is at the origin of the lateral thickness variations in the salt layer and of the polygonal minibasins formation in the area offshore Algiers. A component of gravity gliding related to the basin subsidence is present.The third study area is the Sørvestsnaget Basin in the SW Barents Sea. Here the Permian salt formed structures that are the result of hundreds of millions years of deformation, mainly through reactive and active salt diapirism consequence of the Mesozoic extensional tectonics due to the Atlantic Ocean opening. This lead to the formation of massive allochthonous salt structures and locally to their deflation. After the end of the crustal extension, the main influence on the salt deformation is attributable to the Quaternary glacial sedimentary wedge and the consequent glacio-isostatically controlled crustal movements, leading to internal redistribution in the allochthonous salt structures. Part of the hypothesis on the salt tectonics mechanisms in the Sørvestsnaget basin were confirmed through analogue modelling.Thanks to the diversity between the three study areas in terms of geological setting, we offer not only a broad picture of different levels of interaction between salt and crustal tectonics, but also of the effect of salt basal slope and differential sedimentary load on the salt structures evolution, as well as different levels of maturity of salt structures, from the younger ones (e.g. salt rollers) to the more mature ones (e.g. salt sheets)
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Cragg, Ian Alan. "Numerical modelling of crustal scale fault propagation." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321166.
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Rayson, Martin W. "Computer aided design of geodetic networks for monitoring crustal tectonics." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278767.
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Gordon, Andres Cesar. "Arquitetura crustal da bacia de Almada no contexto das bacias da margem lesste da América do Sul." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2446.
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A Bacia de Almada, localizada no estado da Bahia, compartilha características similares com as outras bacias da margem leste do Brasil, quando é analisada segundo aspectos como os processos sedimentares e o regime de esforço dominante durante a sua formação. Observa-se uma diferença marcante em relação as outras bacias quando é analisada sob a ótica da composição da crosta transicional, uma vez que não se registra atividade vulcânica durante a fase rifte. A aquisição de um extenso levantamento sísmico 3D, com cabos de 6 km de comprimento e 9.2 segundos de tempo de registro (tempo sísmico duplo), resultaram em imagens sísmicas de boa qualidade das estruturas profundas do rifte. Adicionalmente, estudos de modelagem gravimétrica foram integrados com a análise sísmica para corroborar o modelo geológico. A Bacia de Almada é parte dos sistemas de rifte continentais, desenvolvidos durante o Berriasiano até o Aptiano, que antecederam a quebra do continente do Gondwana, evoluindo posteriormente para uma margem passiva divergente. O processo do rifteamento desenvolveu cinco sub-bacias de orientação NNE-SSO, desde posições terrestres até marinhas profundas, produzindo um arcabouço estrutural complexo. Os perfis da sísmica profunda mostram o afinamento progressivo da crosta continental até espessuras da ordem de 5 km, abaixo da sub-bacia mais oriental, com fatores de estiramento crustal próximo a 7 antes do desenvolvimento de crosta oceânica propriamente dita. As imagens sísmicas de boa qualidade permitem também o reconhecimento de sistemas de falhas lístricas que se iniciam na crosta superior, evoluem atravessando a crosta e conectando as sub-bacias para finalizar em um descolamento horizontal na crosta inferior estratificada. Adicionalmente, a bacia apresenta um perfil assimétrico, compatível com mecanismos de cisalhamento simples. As margens vulcânicas (VM) e não vulcânicas (NVM), são os extremos da análise composicional das margens divergentes continentais. Na Bacia de Almada não se reconhecem os elementos arquiteturais típicos das VM, tais como são as grandes províncias ígneas, caracterizadas por cunhas de refletores que mergulham em direção ao mar e por intenso vulcanismo pré- e sin-rifte nas bacias. Embora a margem divergente do Atlântico Sul seja interpretada tradicionalmente como vulcânica, o segmento do rifte ao sul do Estado da Bahia apresenta características não-vulcânicas, devido à ausência destes elementos arquiteturais e aos resultados obtidos nas perfurações geológicas que eventualmente alcançam a seqüência rifte e embasamento. Regionalmente a margem divergente sul-americana é majoritariamente vulcânica, embora a abundância e a influência do magmatísmo contemporâneo ao rifte seja muito variável. Ao longo da margem continental, desde a Bacia Austral no sul da Argentina, até a Bacia de Pernambuco no nordeste do Brasil, podem ser reconhecidos segmentos de caráter vulcânico forte, médio e não vulcânico. Nos exemplos clássicos de margens não vulcânicas, como a margem da Ibéria, a crosta transicional é altamente afinada podendo apresentar evidências de exumação de manto. Na Bacia de Almada, a crosta transicional apresenta importante estiramento embora não haja evidências concretas de exumação de manto. Os mecanismos responsáveis pela geração e intrusão dos grandes volumes de magma registrados nas margens divergentes são ainda sujeitos a intenso debate. Ao longo da margem divergente sul-americana há evidências da presença dos mecanismos genéticos de estiramento litosférico e impacto de plumas. Alternativamente estes dois mecanismos parecem ter tido um papel importante na evolução tectônica da margem sudeste e sul, diferenciando-as da margem continental onde foi implantada a Bacia de Almada.The Almada Basin, located in the Bahia State, shares similar characteristics with other eastern Brazilian basins when analyzed in terms of major sedimentation process and dominant stress regime. However, a remarkably different composition of the transitional crust is observed when this basin is compared with the other eastern Brazilian basins. A large 3D survey, acquired with cable length of 6 km and 9.2 seconds resulted in good seismic images of the rift deep structure. A detailed gravity survey and 2D forward modeling were integrated with the seismic analysis to corroborate the geological model. The Almada Basin is part of the continental rift system that developed during the Berriasian to Aptian times, heralding the Gondwana break up. Subsequently the basin evolved into a passive divergent margin. The rifting process results in five NNE-SSW striking half-graben sub-basins, from onshore to deep water, producing a complex structural framework. Deep seismic profiles reveal the progressive thinning of the continental crust down to 5 km below the easternmost half-graben with a crustal β factor of 7 before the ocean crust developed. The good-quality seismic images also allowed the recognition of major listric faults systems that cut the upper crust, linking the half-grabens and detaching along the layered lower crust. The basin shows an asymmetrical crustal profile compatible with a simple shear rifting mechanism. Volcanic Margins (VM) and Non Volcanic Margins (NVM) are the end members of the crustal compositional analysis of divergent continental margins. The key architectural elements of the VM, such as large igneous provinces, seaward dipping reflectors and the basinal synrift magmatism, are not recognized in the Almada Basin. Even though the South Atlantic divergent margin is traditionally interpreted as a VM, particularly in the rift segment south of Bahia State, the lack of these key elements, as well as drilling results, indicate a non volcanic character for the Almada segment. Regionally, the South American divergent margin is mostly volcanic, but the amount and the influence of the magmatism during the rift phase is variable from the southernmost Austral Basin in south Argentina up to the Pernambuco Basin in northeast Brazil. Along the whole continental margin different segments of strong, medium and non volcanic character can be recognized. In the classical NVM, the transitional crust is highly stretched and, in some cases, it shows evidence of exhumed sub continental mantle (e.g., Iberian margin). In the Almada Basin, the transitional crust indicates a considerable thinning, but there is no clear evidence of mantle exhumation. The mechanisms responsible for the generation and emplacement of the large amounts of magma recorded in the divergent margins are still subject to discussions. Along the South American segments, both the lithospheric thinning and mantle plume models have been proposed. Alternatively, a combination of these two mechanisms may have played an important role in the margin evolution.
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Gilbert, John Bennett. "Crustal Deformation During Arc-Flare Up Magmatism: Field And Microstructural Analysis Of A Mid-Crustal, Melt Enhanced Shear Zone." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/699.
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This study combines structural field data with microstructural observations in an analysis of a mid-crustal shear zone related to the emplacement of the Misty pluton during a high-flux magmatic event in Northern Fiordland, New Zealand. These high-flux magmatic events transport massive amounts of heat and material as they develop along accretionary continental margins, and represent a primary source of continental crust. Fiordland, New Zealand possesses, perhaps, the most extensive middle and lower crustal exposure of these systems on earth. Therefore, this study area provides a significant opportunity to understand processes of continental crust formation in the mid-crust and how these events relate to the broader construction of continents.
Herein, I document the four-stage geologic history of the Cozette Burn field area. Pre-existing structures along the Gondwana accretionary margin hosted a regional flare-up magmatic event that produced the Misty pluton and several other large plutons of the West Fiordland Orthogneiss (WFO). This study primarily focuses on the mid-crustal emplacement of the Misty pluton during oblique convergence along the accretionary margin, forming the upper-amphibolite facies Misty Shear Zone (MSZ). The exposures of the MSZ within the Cozette Burn preserve rare structural relationships between host rock and the intrusive Misty pluton. Together, these structures developed during end-stage contractional tectonics that constructed a long-lived (~270+ Ma) composite batholith.
Heterogeneous ductile shearing defines the MSZ, with microstructural evidence indicating an interplay of high-temperature crystal plastic deformation along with partial melting of host rock and melt channeling. This resulted in focused, melt-assisted shearing under regional transpressive deformation. These accommodative processes provided an efficient mechanism for moving heat, fluids and magma sourced from the lower crust/mantle boundary into the mid-crust during 15-25 km of crustal thickening related to arc flare-up magmatism.
This flare up magmatism and MSZ formation occurred during the final stages of crustal thickening along Gondwana continental margin. High-strain, mylonitic- ultramylonitic shear zones developed in a later phase of deformation, cutting MSZ fabrics near contacts between the Misty pluton and host rock. These more localized shear zones can be attributed to either accommodation of localized melt-pressure buildup or the shift to extensional tectonics. Brittle faulting cut these structures with oblique-thrust in the Tertiary. These mid-crustal structures carry economic relevance: thickened-crust events along accretionary continental margins produce deep-crustal sourced, metal-bearing magmas that are transferred into mid-crust prior to their hydrothermal emplacement as ore deposits in the upper crust. The lasting influence of these processes warrants consideration when assessing continental crust architecture at all scales.
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Chan, Yau-cheong Ian, and 陳有昌. "Characterizing crustal melt episodes in the Himalayan orogen." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206505.
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Extensive studies have been undertaking in exploring the tectonic evolution of the Himalayan Orogen. Various tectonic models were developed to explain and constraint spatially and temporally critical events including the collision of Indian Plate with the Eurasia Plate, crustal thickening in association with the indentation, crustal spreading of the Tibetan Plateau. Recent study by King et al., 2011 identified two distinct leucogranite suites which were formed by contrasting tectonic actions at Sakya. They are Equigranular Anastomosing Leucogranite (AEG) formed under prograde fluidpresent condition while the Discrete Porphyritic Pluton Leucogranite (DPP) formed with retro-grade fluid-absent environment. Based on the characteristics of AEG and DPP, this study started with the acquisition of geochemistry data of rock samples collected for researches at various locations of the Himalaya Orogen. The two leucogranite suites were characterized through the study of their geochemistry comprised major elements, trace elements and rare earth elements models. Results of the studies concluded the existence of AEGs and DPPs distributed over the eastern area of the Himalaya Orogen beyond longitude 85 degree East. DPPs are also found at the far West location of the orogen. AEGs are typically formed from around 38Ma to 23Ma, while DPPs are of young age from 23Ma to 15Ma. Based on the observation of missing, or paucity in data for AEG and DPPs available to the west of longitude 85 degree East, it is hypothesized that recent collision of the Arabia plate to the Iran Domain inhibited the northward indentation movement of the Indian plate that not only caused the anticlockwise rotation of the Indian plate but also decreased the rate of tectonic movement of the Indian plate in the West relative to Eurasia plate. The slow rate of tectonic movement may result in insufficient thickening/energy developed within the crustal layer to cause any melting.
Further studies to examine and development of the hypothesis is recommended.published_or_final_version
Applied Geosciences
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Lawson, N. Kate. "Crustal accretion near ridge-transform intersections : Kane fracture zone, mid-Atlantic ridge." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/1157/.
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Leftwich, Timothy E. "Geopotential investigations of the crustal structure and evolution of Mars." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1147893346.
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Dilles, Zoe Y. G. "Geochronologic and Petrologic Context for Deep Crustal Metamorphic Core Complex Development, East Humboldt Range, Nevada." Scholarship @ Claremont, 2016. http://scholarship.claremont.edu/scripps_theses/811.
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The Ruby-Humboldt Range in Northeastern Nevada exposes the deepest crust in the western portion of the Sevier Hinterland. The product of unique brittle and ductile accommodations, this block of lower crustal rock is a window into the processes of continental thickening and extension. The structure of the northern tip of the Ruby-Humboldt Range core complex is dominated by a large recumbent fold nappe with a southward closeure cored by Paleoproterozoic-Archean gneissic complexes with complex interdigitated field relationships that record polyphase continental metamorphism. Amphibolite-grade metapelitic rocks within the core and Winchell Lake nappe record a wide range of zircon age dates of metamorphic events the oldest of which at ~2.5 Ga is recorded in adjacent orthogneiss as a crystallization age. At least two younger metamorphic events are recorded within this orthogneiss, most significantly at 1.7-1.8 Ga, an event previously unpublished for this region that links it to Wyoming province activity in addition to inherited component of detrital cores up to 3.7 Ga in age that is among the oldest ages reported in Nevada. The youngest overprint of cretaceous metamorphic overgrowth ranges fro 60-90 Ma in age based on zircon rims in the aforementioned units as well as three garnet amphibolites that intrude the core of the nappe and are interpreted to be metabasic bodies.
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Wightman, R. T. "Constraints on crustal development and tectonics in the Archaean rocks of south India." Thesis, Open University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374494.
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Gudmundsson, M. T. "The crustal structure of the subglacial Grimsvotn Volcano, Vatnajokull, Iceland, from multiparameter geophysical surveys." Thesis, University College London (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342375.
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Tsoumakos, Petros E. "Interpretation of a seismic survey of crustal structure in western Scotland and the Hebrides." Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236701.
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Opare-Addo, Emmanuel. "Aspects of Early Proterozoic granitoids and migmatites in southern Ghana : implications for crustal evolution." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240966.
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Moore, James D. P. "Viscoelastic modelling of crustal deformation." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6e73f2e2-a8f7-4790-8f13-f562d50302a9.
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Deformation in continents is not restricted to narrow bands but is spread over great distances within their interiors. A number of lines of evidence, including the distribution of earthquakes, reveal that the strength of different continental regions varies markedly. While it is relatively easy to qualitatively map out these variations, little progress has been made in quantifying the range of strength in the continents and identifying the physical mechanisms that control these variations. I investigate crustal deformation associated with the earthquake cycle, inflation of magma chambers beneath volcanoes, and changes in surface loads. Results of these models has important implications for our understanding of large-scale continental deformation and mountain building, in addition to both seismic and volcanic hazard assessment. Novel analytic solutions for simple shear with depth-dependent linear and non-linear viscoelastic rheologies are derived, in addition to analytical solutions for imposed harmonic tractions and displacements on an elastic layer over a Maxwell viscoelastic half space.
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Swenson, Jennifer Lyn. "Broadband regional waveform modeling to investigate crustal structure and tectonics of the central Andes." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/282873.
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We use broadband regional waveform modeling of earthquakes in the central Andes to determine seismic properties of the Altiplano crust. Properties of the shear-coupled P-wavetrain (SPL ) from intermediate-depth events provide particularly important information about the structure of the crust. We utilize broadband seismic data recorded at the BANJO and SEDA stations, and synthetic seismograms computed with a reflectivity technique to study the sensitivity of SPL to crustal and upper mantle parameters at regional distances. We find that the long-period SPL-wavetrain is most sensitive to crustal and mantle Poisson's ratios, average crustal velocity, and crustal thickness. A comprehensive grid search method developed to investigate these four parameters suggests that although trade-offs exist between model parameters, models of the Altiplano which provide the best fit between the data and synthetic seismograms are characterized by low Poisson's ratios, low average crustal velocity and thick crust. We apply our grid search technique and sensitivity analysis results to model the full waveforms from 6 intermediate-depth and 2 shallow-focus earthquakes recorded at regional distances by BANJO and SEDA stations. Results suggest that the Altiplano crust is much thicker (55-65 km) and slower (5.75-6.25 km/s) than global average values. Low crustal and mantle Poisson's ratios together with the lack of evidence for a high-velocity lower crust suggests a bulk felsic crustal composition, resulting in an overall weak crust. Our results favor a model of crustal thickening involving large-scale tectonic shortening of a predominantly felsic crust. To better understand the mechanics of earthquake rupture along the South American subduction zone, we have analyzed broadband teleseismic P-waves and utilize single- and multi-station inversion techniques to constrain source characteristics for the 12 November 1996 Peru subduction zone earthquake. Aftershock locations, intensity reports, directivity, and spatial locations of seismic moment pulses indicate that the 1996 Peru event ruptured primarily southeast. This earthquake re-ruptured a portion of the 1942 Peru event. We find no indication that the 1996 Peru earthquake ruptured to the northwest, suggesting a sizable gap along the Peru trench corresponding to the position of the northwest flank of the subducting Nazca Ridge.
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Burkett, Corey A. "LATE QUATERNARY CRUSTAL DEFORMATION AT THE APEX OF THE MOUNT MCKINLEY RESTRAINING BEND OF THE DENALI FAULT, ALASKA." UKnowledge, 2014. http://uknowledge.uky.edu/ees_etds/25.
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The tallest mountain in North America, Mount McKinley is situated inside a sharp bend in the right‐lateral Denali fault. This anomalous topography is clearly associated with the complex geometry of the Denali fault, but how this topography evolves in conjunction with the adjacent strike‐slip fault is unknown. To constrain how this fault bend is deforming, the Quaternary fault‐related deformation on the opposite side of the Denali fault from Mount McKinley were documented through combined geologic mapping, active fault characterization, and analysis of background seismicity. My mapping illustrates an east‐west change in faulting style where normal faults occur east of the fault bend and thrust faults predominate to the west. These faults offset glacial outwash terraces and moraines which, with tentative correlations with the regional glacial history, provide fault slip rates that suggest that the Denali fault bend is migrating southwestward. The complex and elevated regional seismicity corroborates the style of faulting associated with the fault bend and provide additional subsurface control on the location of active faults. Seismologic and neotectonic constraints suggest that the maximum compressive stress axis rotates from vertical east of the bend to horizontal and Denali fault‐normal west of the bend.
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McFarland, Phillip K., Richard A. Bennett, Patricia Alvarado, and Peter G. DeCelles. "Rapid Geodetic Shortening Across the Eastern Cordillera of NW Argentina Observed by the Puna-Andes GPS Array." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626449.
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We present crustal velocities for 29 continuously recording GPS stations from the southern central Andes across the Puna, Eastern Cordillera, and Santa Barbara system for the period between the 27 February 2010 Maule and 1 April 2014 Iquique earthquakes in a South American frame. The velocity field exhibits a systematic decrease in magnitude from similar to 35mm/yr near the trench to <1mm/yr within the craton. We forward model loading on the Nazca-South America (NZ-SA) subduction interface using back slip on elastic dislocations to approximate a fully locked interface from 10 to 50km depth. We generate an ensemble of models by iterating over the percentage of NZ-SA convergence accommodated at the subduction interface. Velocity residuals calculated for each model demonstrate that locking on the NZ-SA interface is insufficient to reproduce the observed velocities. We model deformation associated with a back-arc decollement using an edge dislocation, estimating model parameters from the velocity residuals for each forward model of the subduction interface ensemble using a Bayesian approach. We realize our best fit to the thrust-perpendicular velocity field with 705% of NZ-SA convergence accommodated at the subduction interface and a slip rate of 9.10.9mm/yr on the fold-thrust belt decollement. We also estimate a locking depth of 149km, which places the downdip extent of the locked zone 13520km from the thrust front. The thrust-parallel component of velocity is fit by a constant shear strain rate of -19x10(-9)yr-(1), equivalent to clockwise rigid block rotation of the back arc at a rate of 1.1 degrees/Myr.
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Leftwich, Timothy E. "Geophysical investigations of the crustal structure and evolution of Mars." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1147893346.
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Guntoro, Agus. "Tectonic evolution and crustal structure of the Central Indonesian Region : from geology, gravity and other geophysical data." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307471.
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Jaafar, Rani Gomez Francisco Gustavo. "GPS measurements of present day crustal deformation within the Lebanese Restraining Bend along the Dead Sea Transform." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/6288.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 12, 2010 ). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Francisco Gomez, Thesis Supervisor. Includes bibliographical references.
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Wharton, Mark R. "Crustal accretion during the earliest stages of intra-oceanic arc volcanism : examples from Fiji and Tonga, SW Pacific." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/1616/.
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Takahashi, Atsushi. "Hierarchical Cluster Analysis of Dense GNSS Data and Interpretation of Cluster Characteristics." Kyoto University, 2019. http://hdl.handle.net/2433/244510.
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Alvarado, Patricia Monica. "Crustal Seismicity in the Back-Arc Region of the Southern Central Andes from Historic to Modern Times." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195537.
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The western margin of South America between 30ºS and 36ºS is seismically active. While the largest magnitude earthquakes are the interplate subduction zone events, the historically most devastating earthquakes have been the moderate-to-large magnitude earthquakes with depths < 35 km in the Andean back-arc. This region is characterized by accreted terranes later reactivated during Mesozoic extensional processes. Crustal seismicity in the back-arc is related to the thin-skinned Precordillera (PC) fold-thrust belt and the thick-skinned Sierras Pampeanas (SP) basement-cored uplifts overlying the flat slab segment. South of 33ºS, the active volcanic arc above the normally dipping subducted plate is also seismically active at crustal depths. In this study we combined historical and regional broadband seismic data to characterize moderate-to-large earthquakes and the crustal structure in this region. We have digitized and modeled teleseismic records of the 1944 and 1952 San Juan, Argentina PC earthquakes. Both events have shallow source depths, short duration of the source time functions with a thrusting focal solution for the 1944 (Mw 7.0) earthquake and a major strike-slip component in the 1952 (Mw 6.8) earthquake solution. By modeling regional broadband waveforms collected during the CHile-ARgentina Geophysical Experiment (CHARGE) during 2000 and 2002 we constrained the seismic moment tensor and improved focal depths for 27 crustal (3.5 < Mw < 5.1) earthquakes. We found predominantly thrust-fault focal mechanisms and focal depths of 10-26 km for earthquakes over the flat slab region; the eastern SP and active arc have earthquakes with strike-slip focal mechanisms and shallower depths. We used these same earthquakes to determine the crustal structure using raypaths that sample different geologic terranes. Our results indicate high Vp, low Vs for the northern Cordillera, PC and western SP thicker crust; low Vp, low Vs and a thinner crust beneath the arc (south of 33°S) consistent with a mafic composition and partial melt. The eastern SP basement shows low Vp, low Vs and thinner crust consistent with a more quartz-rich composition. These differences have an important control on the present day Andean earthquake deformation and the high seismic hazard posed in this region.
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Nnange, Joseph Metuk. "The crustal structure of the Cameroon Volcanic Line and the Foumban Shear Zone based on gravity and aeromagnetic data." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305782.
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Papapavlou, Konstantinos. "Petrochronology and mineral chemistry of mid-crustal shear zones : new tools for tectonics and mineral exploration." Thesis, University of Portsmouth, 2017. https://researchportal.port.ac.uk/portal/en/theses/petrochronology-and-mineral-chemistry-of-midcrustal-shear-zones(e59893a5-5079-43b8-8dfd-b83e207b5097).html.
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Dating ductile shear zones is daunting because we have to demonstrate either that the chronometer of choice grew during shear zone operation or that crystal-plastic deformation induced age resetting. By adopting a petrochronological approach in this project combining petrographic, geochemical, U-Pb isotopic, and quantitative microstructural data U-Pb isotopic dates are linked with certain shear zone processes. The study area is the South Range of the world-class Sudbury Impact Structure. Specifically, mylonitic shear zones at the Creighton Mine (South Range, Sudbury) operated during three distinct tectonothermal events at ca. 1.75 Ga, 1.65 Ga, and 1.45 Ga. The age dating of texturally and geochemically characterised titanite grains from a shear zone exposed at the 5400 level of the Creighton Mine, indicates operation of the shear during the Mazatzalian – Labradorian orogeny (1.7 – 1.6 Ga). Meso-scale sulphide structures of mechanical remobilization, within the main body of the examined shear zone, show that this event facilitated the local-scale transfer of sulphides to satellite positions. Three age populations of ca. 1.75 Ga, 1.65 Ga, and 1.45 Ga are also prevalent in shear zones from deeper levels of the Creighton Mine. These age populations yield new insights into the orogenic history of the South Range and the Southern Province, and provide further constraints on the comparison of accretionary provinces of the North American Mid-continent and the Southwest United States. Taking into consideration the fluid-mediated and crystal-plasticity textural features in the examined titanite populations it is suggested that these dates record events of syndeformational fluid percolation. Within the 1.75 Ga textural population of titanite grains survived inclusions of inherited titanite grains with shock-metamorphic features. Microstructural and micro to nano-scale crosscutting relationships suggest that the shock wave during the 1.85 Ga impact event induced in these grains the growth of 75°/<010> and 108°/<010> shock microtwins. The nucleation of twins induced a work hardening effect that allowed their survival during the later polyorogenic reworking of the basin (1.75 to 1.45 Ga). U-Pb age dating of these grains yield accurately the age of impact (i.e. 1851 ± 12 Ma). In comparison, titanite grains located within Archaean target rocks ofthe Vredefort structure show identical crystallographic features and partial age resetting. The differential response is attributed to the different distance of the samples from the base of the impact melt sheet that was the dominant heat source. The ore-controlling character of the examined shear zones in the Sudbury mining camp can provide critical information about the exploration potential of these structures in metallogenetic settings. Preliminary mineral-chemical analysis, from major to trace element level, of fabric-forming silicates show distinct trends in the abundance of pathfinder elements (e.g. transition metals). Further, work that will collate the different datasets using multivariable statistical methods will be pursued in order to untangle the vectoring potential of different elements.
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Moore, Nicole E. DeBari Susan M. "Origin and geochemical evolution of mafic magmas from Mount Baker in the northern Cascade arc, Washington : probes into mantle and crustal processes /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=345&CISOBOX=1&REC=14.
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Randall, Darren Edward. "A palaeomagnetic study of crustal rotations and their relationship to the tectonics of the Atacama and Domeyko fault systems, northern Chile." Thesis, University of Plymouth, 1996. http://hdl.handle.net/10026.1/1728.
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A total of 178 sites have been collected for palaeomagnetic analysis from within two strike-slip fault systems in northern Chile (25.4°S - 26.4°S); the Atacama Fault System in the Coastal Cordillera, and the Domeyko Fault System in the Andean pre-Cordillera. In the Coastal Cordillera, analysis of Middle Jurassic lavas (La Negra Formation) and Middle Jurassic to Early Cretaceous dyke swarms reveal a consistent clockwise rotation of approximately 42°. The remanence from the La Negra Formation passes both fold and reversal tests and is interpreted as a pre-folding remanence. Four of the five dyke swarms have mixed polarity, suggesting that they too carry a primary or very early remanence. The clockwise rotation of the area is interpreted as occurring due to a domino-type mechanism where the blocks are bounded by sinistral faults operating in a crustal scale strike-slip duplex structure. The rotation is the result of sinistral transpression during the middle Cretaceous as a result of the Peruvian Orogeny leading to abandonment of the Jurassic-Early Cretaceous magmatic arc in the Coastal Cordillera and its subsequent eastward migration. The Domeyko Fault System (DFS) comprises the Domeyko Fault Zone (DFZ), and a series of subsidiary faults to the east which define two distinct but slightly overlapping domains: a fold-and-thrust belt in the north and a domain o f sinistral strike-slip faults in the south. Samples were collected from the volcanic rocks of the Sierra Fraga Formation (Middle Jurassic) west of the DFZ, and from the lavas of the Quebrada Vicunita Formation (Late Jurassic) and Cerro Valiente Formation (Palaeocene) from both domains of the DFS. Also sampled in the southern domain, and in a small area between the two domains were sandstones o f the Quebrada Monardes Formation (Early Cretaceous). All of the volcanic units have been remagnetised and no tectonic interpretation is made from them. The sandstones in the southern domain record a clockwise rotation of approximately 24°. This is interpreted as being due to compression across the DFS causing the sinistral strike-slip faults, and the blocks between them to rotate clockwise towards the major tectonic structure, the DFS. The sandstones in the central area between the two domains record an anticlockwise rotation of approximately 28°. This is explained by small-scale rotation of thrust sheets or slip on minor dextral strike-slip faults. The deformation and rotation in the pre-Cordillera occurred in response to the Incaic Orogeny during the Miocene-Oligocene.
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Van, Avendonk Hermanus Josephus Antonius. "An investigation of the crustal structure of the Clipperton transform fault area using 3D seismic tomography /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9823314.
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Parks, Jane Elizabeth. "Crustal evolution of Grenville terranes in the central and southern Appalachians : the Pb isotope perspective for Grenville tectonics /." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06162009-063235/.
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Cook, Kristen Lee. "The development of orogenic plateaus : Plateaus: case studies examining relationships between tectonics, crustal strength, surface deformation, and plateau morphology." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45769.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.Includes bibliographical references.
This thesis addresses processes associated with the uplift, deformation, and erosion of orogenic plateaus. The timing and mechanisms of uplift of the Tibetan Plateau and the Altiplano are the subject of ongoing debate. Central issues include the strength of the lower crust and the role of lower crustal flow, the relative importance of continuous deformation versus block deformation, and the possibility of lithospheric delamination. The goal of this thesis is to further explore several of these issues using a combination of numerical modeling, field observations, and thermochronology. I investigate controls on the large-scale evolution of the Tibetan Plateau and the Altiplano using a new quasithree-dimensional viscous flow model that allows for both the development of a weak lower crust and lateral and temporal viscosity variations. Modeling motivated by the Tibetan Plateau shows that lateral variations in crustal strength can have a significant effect on surface velocities throughout the plateau, as well as on the location, shape, and slope of plateau margins and the overall plateau morphology. Model results suggest that crustal strength heterogeneities may be responsible for a number of seemingly unrelated aspects of Tibetan Plateau morphology and deformation. Modeling motivated by the Altiplano explores the relationship between subduction angle, the strength of the lower crust, crustal thickening, and surface shortening in the Central Andes. Model results illustrate that lower crustal flow above regions of steep-slab subduction can redistribute material along strike and can explain discrepancies between surface shortening and crustal thickness in the northern and southern Altiplano. I address the distribution of Middle Cenozoic deformation on the eastern margin of the Tibetan Plateau by using field observations and thermochronology to document an episode of extension and constrain its timing to the Oligocene. Finally, I examine the response of a major river system to flow over an abrupt plateau margin by using topographic data, cosmogenic nuclide dating, and numerical modeling to describe the incision history of the Colorado River into the southwestern Colorado Plateau.
by Kristen Lee Cook.
Ph.D.
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Willis, Michael J. "Crustal motion in the Antarctic interior from a decade of global positioning system measurements." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1198348880.
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Wijns, Christopher P. "Exploring conceptual geodynamic models : numerical method and application to tectonics and fluid flow." University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0068.
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Geodynamic modelling, via computer simulations, offers an easily controllable method for investigating the behaviour of an Earth system and providing feedback to conceptual models of geological evolution. However, most available computer codes have been developed for engineering or hydrological applications, where strains are small and post-failure deformation is not studied. Such codes cannot simultaneously model large deformation and porous fluid flow. To remedy this situation in the face of tectonic modelling, a numerical approach was developed to incorporate porous fluid flow into an existing high-deformation code called Ellipsis. The resulting software, with these twin capabilities, simulates the evolution of highly deformed tectonic regimes where fluid flow is important, such as in mineral provinces. A realistic description of deformation depends on the accurate characterisation of material properties and the laws governing material behaviour. Aside from the development of appropriate physics, it can be a difficult task to find a set of model parameters, including material properties and initial geometries, that can reproduce some conceptual target. In this context, an interactive system for the rapid exploration of model parameter space, and for the evaluation of all model results, replaces the traditional but time-consuming approach of finding a result via trial and error. The visualisation of all solutions in such a search of parameter space, through simple graphical tools, adds a new degree of understanding to the effects of variations in the parameters, the importance of each parameter in controlling a solution, and the degree of coverage of the parameter space. Two final applications of the software code and interactive parameter search illustrate the power of numerical modelling within the feedback loop to field observations. In the first example, vertical rheological contrasts between the upper and lower crust, most easily related to thermal profiles and mineralogy, exert a greater control over the mode of crustal extension than any other parameters. A weak lower crust promotes large fault spacing with high displacements, often overriding initial close fault spacing, to lead eventually to metamorphic core complex formation. In the second case, specifically tied to the history of compressional orogenies in northern Nevada, exploration of model parameters shows that the natural reactivation of early normal faults in the Proterozoic basement, regardless of basement topography or rheological contrasts, would explain the subsequent elevation and gravitationally-induced thrusting of sedimentary layers over the Carlin gold trend, providing pathways and ponding sites for mineral-bearing fluids.
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Hull, Angela Lynn. "Geochronology and thermochronology of Precambrian basement drill core samples in Nebraska and southeastern South Dakota." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1385078311.
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Tozer, Brook. "Crustal structure, gravity anomalies and subsidence history of the Parnaíba cratonic basin, Northeast Brazil." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:90ce8bb0-e55d-4b3c-87e1-aab60084ef42.
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Cratonic basins cover more than 10% of Earth's continental surface area, yet their origin remains enigmatic. In this thesis a suite of new and legacy geophysical and geological data are integrated to constrain the origin of the Parnaíba basin, a cratonic basin in Northeast Brazil. These data include a 1400 km long, deep (20 s two-way travel time) seismic reflection profile, five +/- 110 km offset wide-angle split-spread receiver gathers, gravity anomaly, and well data. In the centre of the basin, the depth to pre-Paleozoic basement is ~ 3.3 km, a zone of midcrustal reflectivity (MCR) can be traced laterally for ~ 250 km at depths between 17-25 km and Moho depth is ~ 42 +/- 2 km. Gravity and P-wave modelling suggests that the MCR represents the upper surface of a high density (2985 kg m3) and Vp (6.7 - 7.0 km s-1) lower crustal body, likely of magmatic origin. Backstripping of well data shows a concave up decreasing tectonic subsidence, similar in form to that commonly observed in rift-type basins. It is shown, however, that the seismic and gravity data are inconsistent with an extensional origin. It is shown that an intrusive body in the lower crust that has loaded and flexed the surface of the crust, combined with sediment loading, provides a satisfactory fit to the observed gravity anomaly, sediment thickness and basin shape. A buried load model is also consistent with seismic data, which suggest that the Moho is as deep or deeper beneath the basin centre than its flanks and accounts for at least part of the tectonic subsidence through a viscoelastic stress relaxation that occurs in the lithosphere following load emplacement. Comparative analysis of the Michigan and Congo basins shows gravity data from these basins is also consistent with a lower crustal mass excess, while subsidence analysis shows viscoelastic stress relaxation may also contribute to their early subsidence histories. However, unlike Parnaíba, both of these basins appear to have been subjected to secondary tectonic processes that obscure the primary 'cratonic basin' subsidence signals. Parnaíba basin, therefore, offers an excellent record for the investigation of cratonic basin formation.
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Salazar, Reinoso Pablo [Verfasser]. "The upper crustal microseismicity image from the North Chilean subduction zone : implications for tectonics and fluid migration / Pablo Salazar Reinoso." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1025511484/34.
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Skipton, Diane. "Paleoproterozoic Metamorphism, Deformation and Exhumation of Mid-Crustal Rocks of the Trans-Hudson Orogen on Hall Peninsula, Baffin Island." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35291.
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In the Paleoproterozoic Trans-Hudson Orogen, a well exposed section of mid-crust on Hall Peninsula, southeastern Baffin Island, offers an opportunity to improve our understanding of mid-crustal tectonothermal processes in hot, collisional orogens. Additionally, more robust age constraints on the tectonic history of Hall Peninsula are important for plate tectonic reconstructions of the North Atlantic region. Recent mapping shows that the section comprises Archean crystalline basement overlain by Paleoproterozoic supracrustal rocks, which host felsic plutons on the western peninsula. There is a westward increase in peak metamorphic grade, from amphibolite- to granulite-facies, and three regional deformation events are recognized (D1, 2, 3). Equilibrium phase diagram modeling constrained by garnet compositions in pelite indicates peak conditions of ~720–740°C on the eastern peninsula and ~850°C further west, with pressures of ~6.25–7.35 kbar. Modeling and petrographical evidence suggest subsequent cooling, decompression, growth of retrograde biotite and, on the eastern peninsula, retrograde muscovite. In situ U-Pb monazite dating (~450 analyses) and U-Pb zircon depth profiling (~90 analyses) resolve the timing of regional metamorphism and crustal shortening between ca. 1860–1820 Ma, coincident with the accretion of crustal blocks and arc terranes during the amalgamation of the orogenic upper (Churchill) plate. Regionally-occurring ca. 1800–1750 Ma monazite domains and zircon rims are interpreted to result from fluid-assisted dissolution-reprecipitation. They likely record the terminal collision with the lower-plate Superior craton and post-orogenic thermal activity, possibly related to the emplacement of pegmatitic syenogranite dykes. The new data strengthen formerly tentative correlations with southern Baffin Island, West Greenland and northern Labrador. 40Ar/39Ar thermochronology on muscovite, biotite and phlogopite suggests that Hall Peninsula underwent slow cooling at rates of ~1–2.5ºC/Myr after peak metamorphism, remaining hotter than ~400°C until ca. 1670–1660 Ma. Analogous thermochronological ages from elsewhere in the Trans-Hudson Orogen imply orogen-wide slow cooling. Despite significant crustal thickening and elevated paleotemperatures, the Hall Peninsula crustal section does not record evidence of orogenic collapse, implying that it may not be a hallmark of all hot, thickened orogens.
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Parent, Andrew Michael. "Pre-Mt. Simon Seismic Sequences Below West-Central Indiana: Local Interpretation and Regional Significance." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright149606295325976.
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Wiemer, Daniel. "Tectonic evolution of the Early Archaean Doolena Gap Greenstone Belt, East Pilbara Terrane, Western Australia." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/102985/1/Daniel_Wiemer_Thesis.pdf.
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This thesis examined how the oldest core of the Australian continent formed more than 3.5 billion years ago. Unraveling the complex tectonic and petrologic history of ancient rocks of the East Pilbara in Western Australia provided important new insights into how and why continents developed on our hot, young planet. A multifaceted methodology of field-based structural geology, uranium-lead (U-Pb) dating of zircon, whole-rock geochemistry, and petrology improved our understanding of early Archaean mass and heat transfer, including the history of the associated planetary surface environment, which hosted some of the earliest life on Earth.
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Benavente, Escobar Carlos Lenin. "Neogene tectonic and exhumation of the Andes Centrales, Southern Peru." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU021/document.
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L’histoire et les mécanismes de soulèvement des Andes centrales ont fait l'objet de débats animés depuis les années 1970. Notre étude se concentre sur l’analyse de la déformation Cénozoïque et de l'exhumation des Andes Centrales dans la région du Sud Pérou : à Cuzco, et dans la région de Nazca entre les cordillères Occidentale et Côtière. En effet, plusieurs auteurs soulignent le rôle du raccourcissement tectonique dans l'épaississement de la croûte, dans l’avant-arc Chilien ou à l’Est dans la région Subandine. Dans les modèles de déformation tectonique active issus du GPS, aucun raccourcissement ni transpression n’est pris en compte sur la bordure Occidentale des Andes au Cénozoïque ou dans les modèles de déformation crustale issus du GPS. La nouvelle cartographie des systèmes de failles actives dans la région sud du Pérou donnent un aperçu de la déformation active à l’échelle crustale pour la marge Pacifique des Andes Centrales. La géomorphologie et les paysages de l'avant-arc andin ont classiquement été présentés comme fossiles depuis le Miocène, sans évidence de structures actives accommodant la déformation cénozoïque. Cependant, les surfaces géomorphologiques bien préservées développées dans l'avant-arc du sud du Pérou fournissent d'excellents marqueurs et des évidences de déformation très nettes depuis le Cénozoïque jusqu’au Quaternaire récent. Ces marqueurs montrent tous un soulèvement des Andes le long de la marge ouest depuis les derniers Millions d’années. Bien que l’initiation et l’évolution de l'exhumation et du soulèvement cénozoïque aient été étudié dans les canyons de Colca et de Cotahuasi, il demeure peu contraint dans le segment nord de l'avant – arc, i.e., dans la région de Nazca. Dans cette étude, nous avons choisi d’apporter de nouvelles données (U-Th)/He et traces de fission sur apatite (AHe) et (AFT) respectivement dans cette région. L’échantillonnage a porté sur la Cordillère Occidentale entre Cañete et Nazca le long de deux nouvelles coupes transversales à la topographie. Le profil Age/Distance à la côte indique une mise en place de relief dans la région Andine au début du Miocène et une évolution découplée des deux systèmes de cordillères Cotière et Occidentale en terme d’exhumation dans le temps. A l’échelle Quaternaire, nous avons cartographié les failles actives pour déterminer leur géométrie, cinématique et les âges maximaux de l’activation de ces failles. Ceci afin de discuter du rôle de cette activité tectonique, précédemment supposée Miocène, dans le soulèvement et l’exhumation de l’avant-arc Andin. Nous avons utilisé la production et l’accumulation du 10Be cosmogénique dans les roches pour déterminer les âges d'exposition d’un escarpement tectonique marquant les derniers épisodes co-sismiques de la faille de Purgatorio. Nos nouveaux résultats, contrastent avec des conclusions précédentes qui concluaient à de l’extension et des vitesses lentes le long de l’avant arc Andin (<0.1mm/an). Les âges très récents indiquent une morphologie « historique » (free face) et deux tremblements de terre Mw6-7 sur ce système de failles transpressives qui se connectent au système principal d’Incapuquio. Les données suggèrent non seulement une déformation active significative de l’avant-arc, mais soulignent aussi l’existence d’un aléa sismique qui n’est toujours pas pris en compte pour les failles crustales dans les Andes. Tandis que l’hypothèse acceptée est que la déformation active est localisée dans le bassin d’avant pays subandin, ou à l’est de la cordillère orientale, nos données suggèrent qu’une partie de la déformation active se localise aussi sur la marge Occidentale ainsi que le long de la faille d'Incapuquio. De plus, les failles observées en néotectonique accommoderaient le partitionnement de la déformation le long de la subduction oblique et ceci n’a jamais été discuté précédemment. Ce mouvement, rigide, en bloc serait du à la présence du craton accrété sur le flanc Ouest et à sa rigiditéABSTRACTTiming and mechanisms of uplift in the Central Andes have been a matter of debate since at least the 1970’s. Our study focuses on Cenozoic deformation and exhumation of the Central Andean forearc in Peru, in Cuzco region, and between the Western Cordillera and the Coastal Cordillera in Nazca region. Our new mapping of active faults provides new insights into the Cenozoic to present-day crustal deformation of the Central Andean Western margin. Until now, apart from some local studies, the geomorphology of the Andean forearc has classically been presented as a remnant Miocene landscape with no significant active structures accommodating the Cenozoic deformation. Thanks to new high-resolution optical imagery, the well-preserved geomorphic surfaces developed within the forearc of southern Peru provide excellent regional markers to map patterns of deformation. Pertaining to the Cenozoic history, while the timing of uplift-related exhumation and Cenozoic exhumation has been studied in Colca and Cotahuasi canyons, it remain poorly constrained in the northern segment of the Central Andean forearc. I report new apatite (U–Th)/He (AHe) and fission track (AFT) ages from the western Cordillera between Cañete and Nazca along two new cross sections. The ages in Nazca region reflect relatively recent (since ~10Ma) relief creation along the western margin of the Altiplano, similar to what is described south in Colca region.The Quaternary tectonic history is revealed by the newly mapped fault segments affecting the Miocene deposits within forearc. Through field and remote mapping, I determined fault geometries and maximum ages for the activity of the faults systems based on stratigraphic relationships in order to assess the role of this tectonic activity in the Western Cordillera uplift and exhumation.To understand the Holocene tectonic history, we use in situ produced 10Be to determine the exposure ages of the free face and tectonic scarp of the Purgatorio Fault in order to map the temporal evolution of its seismotectonic activity. Our new results display evidence of transpression and the formation of meter-high coseismic scarps as well as very recent exposure ages indicating a youthful fault morphology and Mw6-7 earthquakes occurring along the Purgatorio fault segments. These new data are in contrast with some previous conclusions for this region which suggest extension and/or slow rates of deformation for this region and time period. Further, these new data not only suggest significant active deformation within the forearc, but also highlight a potential seismic hazard for the region that not take into account crustal forearc faults.While the general assumption is that active deformation is localized in the Subandean fold and thrust belt, or east of the Western Cordillera in the Altiplano, our data support a model where active deformation is occurring in the western margin as well, along the Incapuquio Fault and other neotectonic faults that accommodates the partitioning of the subduction oblique convergence.These crustal active faults and more precisely the “not migrating to the trench” Incapuquio fault zone reveal the rigid motion of the forearc. Our new model is nevertheless compatible with the recently published GPS data that measure a southeastward movement at 4–5 mm/yr relative to a stable South America reference frame. This rigid motion is in part due to the presence of the rigid Greenvillian accreted craton, that behave as a sliver, and rather tilt than deform through time
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Cesin, Gina Lee. "The Application of Electrical Resistivity and Microgravity to Locate Tunnels along the U.S.-Mexico Border at Calexico." TopSCHOLAR®, 2008. http://digitalcommons.wku.edu/theses/44.
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Johnson, Julie A. "A Geochemical Study of Crustal Plutonic Rocks from the Southern Mariana Trench Forearc: Relationship to Volcanic Rocks Erupted during Subduction Initiation." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1249.
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Two suites of intermediate-felsic plutonic rocks were recovered by dredges RD63 and RD64 (R/V KK81-06-26) from the northern wall of the Mariana trench near Guam, which is located in the southern part of the Izu-Bonin-Mariana (IBM) island arc system. The locations of the dredges are significant as the area contains volcanic rocks (forearc basalts and boninites) that have been pivotal in explaining processes that occur when one lithospheric plate initially begins to subduct beneath another. The plutonic rocks have been classified based on petrologic and geochemical analyses, which provides insight to their origin and evolution in context of the surrounding Mariana trench.
Based on whole rock geochemistry, these rocks (SiO2: 49-78 wt%) have island arc trace element signatures (Ba, Sr, Rb enrichment, Nb-Ta negative anomalies, U/Th enrichment), consistent with the adjacent IBM volcanics. Depletion of rare earth elements (REEs) relative to primitive mantle and excess Zr and Hf compared to the middle REEs indicate that the source of the plutonic rocks is similar to boninites and transitional boninites. Early IBM volcanic rocks define isotopic fields (Sr, Pb, Nd and Hf-isotopes) that represent different aspects of the subduction process (e.g., sediment influence, mantle provenance). The southern Mariana plutonic rocks overlap these fields, but show a clear distinction between RD63 and RD64. Modeling of the REEs, Zr and Hf shows that the plutonic suites formed via melting of boninite crust or by crystallization from a boninite-like magma rather than other sources that are found in the IBM system.
The data presented support the hypothesis that the plutonic rocks from RD63 and RD64 are products of subduction initiation and are likely pieces of middle crust in the forearc exposed at the surface by faulting and serpentine mudvolcanoes. Their existence shows that intermediate-felsic crust may form very early in the history of an intra-oceanic island arc system. Plutonic rocks with similar formation histories may exist in obducted suprasubduction zone ophiolites and would be evidence that felsic-intermediate forearc plutonics are eventually accreted to the continents.
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Yang, Jiaming. "Melting in the Mantle Wedge: Quantifying the Effects of Crustal Morphology and Viscous Decoupling on Melt Production with Application to the Cascadia Subduction Zone." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3880.
Full textAbstract:
Arc magmatism is sustained by the complex interactions between the subducting slab, the overriding plate, and the mantle wedge. Partial melting of mantle peridotite is achieved by fluid-induced flux melting and decompression melting due to upward flow. The distribution of melting is sensitive to temperature, the pattern of flow, and the pressure in the mantle wedge. The arc front is the surface manifestation of partial melting in the mantle wedge and is characterized by a narrow chain of active volcanoes that migrate in time. The conventional interpretation is that changes in slab dip angle lead to changes in the arc front position relative to the trench. We explore an alternative hypothesis: evolution of the overlying plate, specifically thickening of the arc root, causes arc front migration. We investigate the effects of varying crustal morphology and viscous decoupling of the shallow slab-mantle interface on melt production using 2D numerical models involving a stationary overriding plate, a subducting plate with prescribed motion, and a dynamic mantle wedge. Melt production is quantified using a hydrous melting parameterization. We conclude: 1) Localized lithospheric thickening shifts the locus of melt production trenchward while thinning shifts melting landward. 2) Inclined LAB topography modulates the asthenospheric flow field, producing a narrow, well-defined arc front. 3) Thickening of the overriding plate exerts increased torque on the slab, favoring shallowing of the dip angle. 4) Viscous decoupling produces a cold, stagnant forearc mantle but promotes arc front melting due to reduction in the radius of corner flow, leading to higher temperatures at the coupling/decoupling transition.
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Marsh, Nicola A. "The influences of crustal extension, salt tectonics and gravity-driven deformation on the structural evolution of the Halten Terrace, offshore mid-Norway : new sights from 3D seismic data and fault analysis." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/1933/.
Full textAbstract:
Normal fault zones play a fundamental role in the development of sedimentary basins and in the migration and trapping of hydrocarbons. The idealised geometry of an isolated post-sedimentary normal fault (Barnett, 1987, Walsh & Watterson, 1989) existing conceptual models that describe the process of fault growth and linkage in brittle systems (Childs et al, 1995; Cartwright et al, 1996; Childs et al, 1995, 1996b; Huggins et al, 1995), where fault planes composed of many overstepping segments are linked by areas of complex deformation called relay ramps, are generally accepted. Relay zones can trap significant volumes of hydrocarbon or act as leakage points, thus understanding the style of fault linkage, which strongly influences the location of hydrocarbon tops and reservoir compartmentalisation, is vital for any petroleum system.
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Bassett, Daniel Graham. "The relationship between structure and seismogenic behaviour in subduction zones." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:dd284a79-d94a-4732-8dec-cb38c78fca73.
Full textAbstract:
The largest earthquakes on Earth take place on the megathrusts of subduction zones, but the slip behavior of megathrusts is variable. This thesis considers why by conducting local, regional and global studies of the interrelationships between the structure and seismogenic behavior of subduction zones. New marine geophysical data collected from the collision zone between the Louisville Ridge seamount chain with the Tonga-Kermadec trench constrain overthrusting and subducting plate structure. Mo'unga seamount is identified beneath the outer-forearc, which calibrates the association of residual bathymetric anomalies and subducting relief, implies an E-W geometry for the subducted ridge and suggests the 200 km wide Louisville seismic gap is modulated by the sediment filled flexural moat. Spectral averaging is then applied along the Tonga-Kermadec margin and along strike variations in overthrusting plate structure are verified by wide-angle seismic transects. The remnant Tonga-Ridge occupies the inner fore-arc and residual free-air gravity anomalies constrain its latitudinal extent (north of 30.5°S), width (110±20 km) and strike (~005° south of 25°S). Plate tectonic reconstructions suggest the Lau Ridge is unmodified by subduction related erosion, <200 km of the Tonga Ridge has been eroded, and neither ridge ever occupied the southern Kermadec arc. Crustal thickness variations are thus inherited, reflecting the Cenozoic tectonic evolution of the Tonga-Kermadec-Hikurangi margin. Spectral averaging is finally applied to all subduction zones on Earth. Part one develops a global catalogue of subducting relief, which is compared with seismological and geodetic inferences of fault-slip behavior. Most seamounts are aseismic, relatively undeformed and observations are not consistent with mechanical models proposing full-decapitation. Aseismic ridges are also associated with megathrust complexity, but are of a larger wavelength and contrasting mode of isostatic compensation. Part two shows almost all intra-margin along-strike transitions in seismogenic behavior are related to pre-existing crustal structure. A paired forearc anomaly is interpreted consisting of a trench-parallel ridge landward of the deep-sea-terrace basin. The ridge crest correlates with the down-dip limit of coseismic slip and strong interplate coupling, the up- dip limit of tremor epicentres, and is interpreted as defining the boundary between the velocity-weakening and seismogenic portion of the subduction interface and the down-dip frictional transition zone. Paired anomalies may be attributed to unrecovered interseismic elastic strain, the preferential subduction erosion of the outer-forearc and/or underplating beneath the inner forearc.
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Missenard, Yves. "Le relief des Atlas Marocains : contribution des processus asthénosphériques et du raccourcissement crustal, aspects chronologiques." Phd thesis, Université de Cergy Pontoise, 2006. http://tel.archives-ouvertes.fr/tel-00125775.
Full textAbstract:
L'objectif de cette thèse est l'étude des mouvements verticaux et la caractérisation des processus à l'origine de ces mouvements au sein d'une chaîne de montagnes intracontinentale. Les mécanismes contrôlant l'évolution de la topographie sont nombreux et encore mal connus. La chaîne du Haut Atlas marocain est située à plus de 600 km de la limite de plaque Afrique-Europe et supporte pourtant le deuxième sommet d'Afrique (Jbel Toubkal, 4165 m). L'absence de racine crustale développée sous la chaîne, conséquence d'un taux de raccourcissement assez faible (~20 km), implique donc l'existence d'un autre processus permettant de maintenir une telle topographie. La réalisation de profils géophysiques nous permet de montrer qu'un amincissement lithosphérique provoque un soulèvement d'environ 1000 m dans l'Anti-Atlas, le Haut Atlas Central, et le Moyen Atlas. Certains bassins d'avant-pays sont aussi affectés, comme les bassins du Souss, de Ouarzazate ou de Missour. La zone amincie est une bande d'orientation Nord-Est / Sud-Ouest recoupant les principaux domaines structuraux marocains et probablement lalimite de plaque Afrique-Europe.
Le raccourcissement crustal est le deuxième mécanisme à l'origine du relief de cette chaîne. Une analyse structurale sur la base des données de terrain dans le Haut Atlas de Marrakech nous a permis de montrer l'existence d'une stratigraphie mécanique contrastée. Plusieurs niveaux de décollements potentiels y sont identifiés en particulier dans le Viséen, le Cambrien, le Trias et le Sénonien. L'héritage complexe de cette région, située à la limite entre les rifts Triasico-Liasiques Atlantique et Téthysien, contrôle leur activation sur les bordures de la chaîne. Celle-ci entraîne la formation de structures variées : zones triangulaires, plis secondaires (« rabbit ears »), imbrications. Un groupe basal rigide est distingué. Il inclut le Précambrien, et localement le Paléozoique et le Trias. Une coupe complète de la
chaîne est présentée.
La chronologie de la déformation et l'âge de l'amincissement de la lithosphère sous la chaîne sont finalement discutés. Une analyse détaillée de la géologie de l'avant-pays sud du Haut Atlas de Marrakech est combinée aux résultats obtenus par comptage de traces de fissions pour proposer un scénario d'évolution. Une première phase de raccourcissement est identifiée à l'Eocène Supérieur – Oligocène. Au Miocène Inférieur – Moyen, la lithosphère est amincie et une phase de dénudation affecte l'ensemble de la chaîne et son avant-pays. Enfin, une dernière phase de raccourcissement a lieu au Plio-Quaternaire.
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Maurin, Thomas. "Impact de la ride 90°E et du flux crustal Est-Tibétain sur l'évolution récente de la subduction oblique Indo-Birmane : approche géologique, sismique et géodésique." Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2009. http://tel.archives-ouvertes.fr/tel-00425058.
Full textAbstract:
La frontière tectonique entre les plaques indienne et birmane est principalement décrochante avec une faible composante de raccourcissement. La plaque subduite, le bassin du Bengale, est parcourue par des hétérogénéités crustales majeures acquises lors de son processus de formation et de migration vers le Nord (rides de point chaud, failles transformantes...). La plaque supérieure, la microplaque birmane, délimitée à l'Est par la faille décrochante dextre de Sagaing, est dans la zone d'influence du flux crustal Est-Tibétain. Le long d'une large coupe Terre-Mer depuis le bassin du Bengale jusqu'au Nord de la Birmanie, je me suis intéressé à la géométrie structurale et à la cinématique de la subduction hyper-oblique Indo-Birmane en insistant sur les effets d'éléments perturbateurs (flux et hétérogénéités crustaux). Par une approche pluridisciplinaire combinant des observations géologiques structurales de terrain, des données géophysiques marines et des mesures géodésiques, je présente un modèle d'évolution néogène de la subduction oblique en réponse à ces perturbations. Une étude de la sismicité et quelques mesures paléomagnétiques ont complété ce travail.
La ride de 90°E, formée au sein de la croûte océanique du Bengale vers 100Ma, est entrée en collision avec la marge Birmane au Miocène supérieur. Elle a probablement bloqué la subduction dans sa partie méridionale de telle sorte que seule une déformation décrochante dextre le long de son flanc Est est exprimé structuralement. Au Nord de la ride, le prisme externe Indo-Birman est libre de se développer rapidement vers l'Ouest depuis 2Ma à la faveur d'une forte épaisseur de sédiments déposés sur la plaque plongeante (delta du Ganges-Brahmapoutre).
Ce prisme Indo-Birman, construit en convergence hyper-oblique, a enregistré un partitionnement de la déformation : les zones internes sont cisaillées sur une direction Nord-Sud et les zones externes sont raccourcies sur une direction Est-Ouest.
La faille de Sagaing est défléchie de plus de 100km vers l'Ouest dans sa partie Nord. Je propose un modèle dans lequel le flux crustal résultant de l'effondrement du Tibet, est responsable de cette inflexion. Ce modèle questionne le rôle de ce flux dans la construction du prisme partitionné. Appuyé sur l'ensemble des données géodésiques disponibles autour de la syntaxe Est Himalayenne, il établit un lien entre les déformations finis néogènes de la région.
Les données de sismique réflexion ont apporté des contraintes fortes sur la partie marine de la section. Ainsi, la présence de la ride de 90°E et la nature océanique de la croûte du Bengale ont pu être fixées. En revanche, le flux crustal Est-Tibétain reste mal compris. Les données géodésiques permettent d'en approcher la cinématique mais il est nécessaire, pour en connaître la nature, d'y combiner des données géologiques de terrain, qui sont les seuls à permettre l'observation direct de la déformation crustale profonde aujourd'hui exhumée. Ces observations géologiques peuvent aussi apporter des éléments de réponses sur la stabilité du flux au cours du temps. Un travail de modélisation doit encore être mené pour confronter ces idées nouvelles aux propriétés physiques de la lithosphère continentale en cours de déformation.
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Karakas, Ozge. "Modulation of crustal magmatic systems by external tectonic forcing." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45964.
Full textAbstract:
We develop a two dimensional model that simulates the response of the crust to prolonged mantle-derived intrusions in arc environments. The domain includes the entire crustal section and upper mantle and focuses on the evolving thermal structure due to intrusions and external tectonic forcing. We monitor the thermal response, melt fraction and volume for different environments after a definite time by considering geologically relevant melt flux and extensional tectonic rates. The amount of crustal melt versus fractionated primary mantle melts present in the crustal column helps determine crustal structure and growth through time. We observe that with a geophysically estimated flux and tectonic rate, the mantle-derived magma bodies can melt the surrounding volume of crust. We express the amount of crustal melting in terms of an efficiency; therefore we define the melting efficiency as the ratio of the melted volume of crustal material to the volume of melt expected from a strict enthalpy balance as explained by Dufek and Bergantz (2005). Melting efficiencies are less than 1.0 in real systems because heat diffuses to sections of the crust that never melt. The maximum calculated efficiency is 0.05 in our model while most of our simulations show zero efficiency. Additionally, maximum total melt amount is observed in relatively greater extensional environments (0.02 m/yr) and high intrusion rates (10⁻² m³/m²/yr) and in long time periods (2 x 10⁶ years). However, maximum crustal melting in the same environment is reached in 1.2 x 10⁶ years. The relative amounts of mantle-derived and crustal melts in the total volume of magma suggest that the majority of magma composition in crustal column is derived from the mantle material.
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Chevalier, Francis. "Vitesse et cyclicité de fonctionnement des failles normales de rift : implication sur le remplissage stratigraphique des bassins et sur les modalités d'extension d'une marge passive fossile : aplication au demi-graben liasique de Bourg-d'Oisans (Alpes occidentales, France)." Phd thesis, Université de Bourgogne, 2002. http://tel.archives-ouvertes.fr/tel-00877244.
Full textAbstract:
Les objectifs de ce travail sont les suivants. 1- Reconstitution de la géométrie syn-rift du demi-graben de Bourg-d 'Oisans 2- Quantification des vitesses de fon ctionnement des failles normales syn-rift 3- Relation entre vitesse de fonctionnement et processus de croissance des failles normales dans la croûte continentale 4- Reconstitution de la géométrie profonde des failles normales 5- Caractérisation des facteurs de contrôle de l'étirement crustal en contexte de rift 6- Variabilité spatiale et temporelle de l'étirement sur une paléomarge. Secteur d'étude Pour répondre aux différentes problématiques évoquées ci-dessus, le choix du secteur d'étude s'est porté sur le bassin de Bourg-d'Oisans, situé dans la zone dauphinoise du domaine externe des Alpes occidentales françaises . Les raisons qui ont motivé cette décision sont les suivantes. (1) Le bassin correspond à un demi-graben d'âge Jurassique inférieur, situé sur la marge nord-téthysienne (e.g. Lemoine et al. , 1986). (2) La série sédimentaire liasique préservée au sein du demi-graben présente une forte épaisseur au regard des séries réduites situées sur les hauts-fonds voisins (têtes de blocs) (e.g. Mouterde, 1964; Barfety, 1985 ; Bas, 1985). (3) Les sédiments sont de nature essentiellement carbonatée et argilo-carbonatée et contiennent des faunes servant de marqueurs biostratigraphiques (ammonites) qui permettent de dater les séries sédimentaires (Barfety, 1985 ; Bas, 1985). (4) La faille d'Ornon n'a été que modérément inversé durant l'orogenèse alpine (e.g.. Gillchrist et al., 1987). (5) Les structures tectoniques précoces sont bien conservées et affleurent sur l'ensemble du secteur (e.g. Barfety, 1985). (6) Le secteur est connu et a déjà fait l'objet d'études cartographiques et/ou structurales sans analyse stratigraphique détaillée (e.g. Reboul, 1962; Bornuat, 1962 ; Barfety, 1985 ; Pinto-Bull, 1987 ; Grand, 1987).
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Jolley, Stephen J. "Mid crustal thrust tectonic processes : examples from the Dalradian of N.W. Donegal." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5884/.
Full textAbstract:
A D2 ductile thrust imbricate stack has been identified within the mid greenschist facies (Appin Group) metasediments of the Breaghy Head area of Co. Donegal. Major stratigraphy parallel tectonic slides detach arrays of subsidiary ductile thrust imbricates, which display patterns of intensifying strain and minor structures generally regarded as being diagnostic of the much broader thrust sense shear zones (tectonic slides) which typify deformation within metamorphic "parts of mountain belts. This commonality of structural associations implies that the. Breaghy Head imbricates and their broader larger scale counterparts must share similar generative and propagative processes. The imbricates have 'shaped' geometries with long bedding parallel flats and shorter 20-30º ramps preserved as hanging wall anticlines, footwall synclines or complex remnant zones of climbing vein arrays. At a number of localities, ramps have escaped direct incorporation into mature thrust profiles and have been preserved within thrust hanging walls, ' frozen' at early on _intermediate stages of development. This has enabled identification of three distinct ramp styles; "Vein array ramps" characterised by vein array complexes, and "fold ramps" & "fabric slip ramps", both hosted by primary F2 folds. These fold hosted ramps can be seen to nucleate or 'result from coallescent propagation of ductile thrust dislocation cells (F5R & PR respectively).The concept of thrust dislocation cells is supported by the presence of D2 extensional flow within the imbricate stack, expressed by shear bands and boudinage. These structures are kinematically and temporally intimate, forming combinant structures at a number of localities. These structures characteristically intensify towards the thrust planes but are never seen to deform them, such that extensional flow is detached at the thrust plane to which it is seen to intensify. The extensional and contractional flow clearly relates spatially and temporally to the generation and movement of individual imbricates and must, therefore, coexist kinematically as this takes place. This can be explained by Theologically focusing (localising) deformation to produce stratigraphy parallel dislocation cells. The development and subsequent propagation of these features produces the observed structural patterns and displacement connectivity via ramp generation to produce mature 'shaped' ductile thrust profiles. Local polyphase fold and fabric histories are seen to be generated during continuum D2 ductile thrusting. These structures are temporally and spatially restricted, chiefly as hanging wall strains produced by local thrust stacking processes (eg. Imbricate back-steepening and culmination extension). Local polyphase sequences are also generated by development of rare backthrusts, buttressing and footwall collapse of ramps and hard band block rotations. These structures are clearly D2 ductile thrust secondary structures, related to local kinematic processes and do not therefore reflect regional polyphase deformation.
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Diop, Catherine Bineta. "Structures et circulations de fluides dans un avant-pays synschisteux : le système de chevauchements des Mauritanides du Sénégal." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL044N.
Full textAbstract:
Les Mauritanides du Sénégal (Afrique de l'ouest) sont constituées par des nappes épizonales mises en place au varisque. Ces nappes sont constituées de séries du précambrien supérieur au silurien, répétées dans des duplex caractéristiques des systèmes de chevauchements en rampes et paliers. Les chevauchements sont associés à une schistosité majeure S2 orientée N030°E, 15°NW portant une linéation d'étirement régionalement orientée N130°E. Des critères cinématiques suivant cette linéation indiquent que la mise en place des nappes s'est faite du NW vers le SE. La propagation des nappes vers le SE est accommodée par des structures plicatives variées: antiformes de propagation associées à des kinks, plis déjetés au SE et plis isoclinaux dans les contacts chevauchants, toutes développées dans un même continuum de déformation monocyclique. On observe une deformation cisaillante marquée uniquement au niveau des contacts ; mais dans les nappes, la déformation est à dominante co-axiale, comme le montrent les opr du quartz, qui indiquent une activation des systèmes basal et prismatique . Ces témoins de la déformation plastique sont accompagnés d'une dissolution-cristallisation importante assistée par les fluides et se traduisant par des veines et fentes de tension remplies de quartz, des stylolites et des microfractures indiquant un raccourcissement perpendiculaire à S2. L’étude de la fabrique de forme de marqueurs au sein des nappes a montré une forme généralement aplatie dans la schistosite S2, et compatible avec l'action de la dissolution-cristallisation. Les conditions métamorphiques pendant la formation des nappes déterminée par la pétrologie et l'étude des inclusions fluides ont été estimées entre 500°C et de 300°C du NW au SE pour des pressions maximales de 4 kbars. Les fluides mis en place dans les nappes, principalement aux zones de contact, ont une composition influencée par la nature du substratum. Les Mauritanides sont un avant-pays caractérisé par une tectonique pelliculaire