L'ouvrage traite de la déformation 3D des bassins sédimentaires. L'objectif est l'étude de la déformation tectonique, puis son intégration dans la modélisation de bassin pour des calculs de migration d'hydrocarbures. Pour répondre à la complexité des phénomènes, le modèle s'appuie sur des principes cinématiques et l'utilisation d'une méthode discrète, ainsi que sur le développement d'un outil informatique qui autorise une grande diversité dans les mécanismes de déformation pris en compte. La déformation volumique 3D est obtenue à partir de l'étude du comportement de la surface neutre de chaque couche déformée du bassin. L'idée est de déformer la surface neutre de chaque couche, puis de s'appuyer sur ce résultat pour reconstituer la déformation volumique du bassin. L'algorithme intègre trois caractéristiques. La première porte sur l'opérateur mathématique utilisé pour modéliser le plissement par flexion qui est une combinaison de translation des points de la surface neutre et de rotation des segments verticaux rattachés à ces points. Ceci assure la réversibilité de la modélisation. La seconde porte sur l'utilisation d'une approche discrète autorisant une meilleure description de la déformation et permettant de contrôler localement son évolution. La connaissance des variations locales de volume peut devenir un puissant outil d'analyse en géologie structurale et le parfait complément d'une étude de terrain. La troisième concerne la modularité du code développé: le modèle intègre trois mécanismes de déformation, mais l'architecture du code autorise l'insertion future d'autres mécanismes ou une plus forte interaction entre ceux-ci. Le modèle a été validé tout d'abord sur des cas 2D, puis 3D naturels. Ils offrent des résultats satisfaisants d'un point de vue qualitatif. Ils mettent en lumière l'aptitude du modèle à proposer un chemin de déformation géologiquement acceptable, ainsi que sa capacité à contrôler les variations volumiques du bassin au cours de la déformation.

L'objet de la thèse est de mettre au point un prototype de modèle 2D capable de simuler l'évolution géométrique d'une coupe de bassin affectée par le jeu de failles. Une modélisation mécanique de la déformation tectonique, fondée sur le principe des calculs de structure, n'est pas poursuivie car cette approche est trop complexe pour être appliquée au domaine des bassins sédimentaires. Au contraire, le modèle cinématique développé, FOLDIS, repose sur des hypothèses simplificatrices de nature purement géométrique qui déterminent entièrement le mode de déformation envisagé. Jusqu'à présent, les modèles cinématiques de bassin, tels que THRUSTPACK, destinés à modéliser la déformation tectonique complexe des bassins d'avant-chaînes de montagne n'incluent pas la prise en compte des effets géométriques de la compaction mécanique par diminution de porosité. D'autres types de modèles de bassin, comme TEMIS, destinés à modéliser les écoulements, la compaction associée ainsi que l'évolution physico-chimique de la matière organique et des fluides hydrocarbures, ne peuvent être appliqués que dans des zones où la déformation tectonique est simple. C'est à dire dans des bassins sans failles obliques actives, dont le jeu entraînerait nécessairement des déplacements latéraux des écailles tectoniques ainsi qu'une déformation conjointe des sédiments. Le développement du modèle cinématique FOLDIS a un double objectif: * Il s'agit de proposer une méthode de calcul des déformations tectoniques qui présente des améliorations par rapport aux modèles cinématiques existants. Les configurations d'application du modèle FOLDIS sont en effet plus étendues que celle du modèle cinématique THRUSTPACK par exemple. Pour illustrer cette affirmation, on peut avancer le simple fait que les géométries des failles présentes dans un domaine d'étude du modèle FOLDIS ne sont pas limitées à être toutes définies avec un pendage orienté dans le même sens . * TI s'agit ensuite de prendre en compte le phénomène de compaction dans le modèle. Comme les objets du modèle FOLDIS sont de nature discrète, ils se prêtent bien à une modification de leur géométrie et à une redéfinition de leur contour. Après chaque stade de l'évolution du bassin, il est possible de proposer un couplage des déformations tectoniques avec les déformations liées à la compaction par diminution de porosité. Ce couplage repose sur un calcul géométrique incrémentaI. On effectue une prise en compte successive de la déformation tectonique puis de la compaction mécanique pour chaque intervalle de temps correspondant à un incrément cinématique.

Cette étude a pour cadre la partie externe du massif subalpin des Bornes en bordure du lac d'Annecy. La stratigraphie y est étudiée : Lutétien du synclinal du Lindion. La nappe de Veyrier-Bluffy a été définie.

This thesis uses various approaches such as observation of satellite images, field investigations, analogue modeling and GPS measurements to constrain deformation of the basement and sedimentary cover of the Zagros fold-thrust belt in time and space. Focal mechanism solutions of most earthquakes indicate that deformation in the Zagros basement is due to shortening and thickening through numerous thrust faults. However, observations of strike-slip faulting recognized on satellite images imply that N-S trending faults in the Zagros, inherited from Pan-African basement, rotated about vertical axes to accommodate the convergence between Arabia and central Iran. Field studies suggest that southwestward advance of the Zagros front has been recorded by syn-sedimentary structures. These structures indicate that deformation started as early as end Eocene in the northeast of the Simply Folded Zone and propagated progressively to the southwest. The deformation front drove the foreland basin to its present position along the Persian Gulf and Mesopotamia. Scaled analogue models suggest that the seismicity due to orogenic shortening depends largely on the friction between the cover and its basement. Models show that fold-thrust belts with low tapers shortened above low friction ductile decollements involve several long-lived thrust faults generating low to moderate earthquakes over wide areas at the same time. By contrast, earthquakes with larger magnitudes are expected to occur along a few short-lived thrust ramps in fold-thrust belts with larger tapers shortened above high-friction decollments. GPS-derived velocities across and along the Zagros suggest that only about one third (10 ± 3 mm/yr) of the current convergence between Arabia and Eurasia is accommodated within the Zagros by thickening to the east of the Kazerun Fault and thickening and lateral movement to the west. The remaining (21 ± 3 mm/yr) is transferred beyond the Zagros suture to central Iran and the northern Iranian mountains.

Three long sediment cores (BDP-98 – 600 m, BDP-96 – 200 m and BDP-93 – 100 m) drilled in Lake Baikal (Siberia) have been studied with the aims of establishing an absolute chronology and reconstructing paleoclimatic and paleoenvironmental changes in the region. The location of the lake at relatively high latitude and continental interior and a thick continuous sedimentary archive that developed in a rift system tectonic setting provide unique material for this investigation. The cosmogenic isotope 10Be was used for dating and the results indicate time spans of 8 (+0.8\-0.6) Myr for BDP-98, 5.5 (±0.13) Myr for BDP-96 and >0.7 Myr for BDP-93. Two major sedimentary facies (deltaic and hemipelagic) are distinguished by textural geochemical and mineralogical data. Detrital mineral composition suggests negligible change in provenance during the period studied. Formation of authigenic minerals, such as framboidal pyrite, vivianite and siderite, reflects variable environmental conditions in the lake and climate change in the region. Biogenic silica content shows climatic influence, which is modified by the supply of detrital material and postdepositional alterations. 10Be dating, combined with lithological analysis of the sediments, makes it possible to place temporal constrains on climate cooling at the Miocene/Pliocene boundary (5 Myr ago) and at the Early/Late Pliocene boundary (3.6 Myr ago) as well as the beginning of the northern hemisphere glaciation at about 2.5–2.6 Myr ago. The regional east-west tectonic extension of south-east Asia, related to Tibetan Plateau uplift, was confined in the Baikal area to between about 7 and 5 Myr ago, with a rifting rate calculated at 7 mm year-1. Furthermore, the 10Be data suggest that geomagnetic field intensity strengthened around the Miocene/Pliocene boundary.

The North Kara Terrane (NKT), with Severnaya Zemlya as its main outcrop area, constitutes the Palaeozoic and older rocks of the northern part of the Kara Shelf. Potential field data suggest a continuation into the eastern Barents Shelf. Several lines of evidence imply that the NKT was a part of Baltica at least during the latter part of the Neoproterozoic, and probably was influenced by Timanian orogeny. The Timanide type area is characterised by metaturbidites from the pre-Timanian passive margin of the East European Craton (EEC). Regional amphibolite facies metamorphism, as exposed on Kanin Peninsula, was probably followed by near-isothermal decompression. It is inferred that these conditions were reached by depression beneath the accreted outboard terranes. Subsequently, the metaturbidites were thrust into their present position onto the EEC’s pericratonic unmetamorphosed shelf sediments. The thrusting was accompanied by rapid exhumation. About 560 Ma late-orogenic granites intrude the Timanian accreted terranes. On Severnaya Zemlya, Neoproterozoic turbidites, containing ca. 560 Ma zircons, are overlain by shelf deposits, which dominate the Palaeozoic until the end of the Silurian. The succession is interrupted by the regional Kan’on (canyon) River Unconformity and probably by a late Neoproterozoic unconformity. New U-Th-Pb ion-microprobe isotope-ages on volcanics and faunal evidence imply that the Kan'on River Unconformity developed in a short time span around the Cambrian-Ordovician boundary. Other isotope-ages demonstrate that intense igneous activity, which has been inferred to be related to rifting within the NKT, extended into the Arenig and was contemporaneous with the development of Baltica’s northeastern passive margin. Zircon xenocrysts (ca. 540 - 580 Ma) in these igneous rocks indicate a Timanian component in the crust below the Severnaya Zemlya Archipelago. In the latest Silurian, Old Red Sandstone facies sedimentation began with the migration of an inferred Caledonian foreland basin into the area of Severnaya Zemlya. The Caledonian deformation front overrode the area in the latest Devonian or earliest Carboniferous. The inferred late Caledonian deformation terminated, according to biostratigraphy and new isotope-ages from Bol'shevik Island granites, before the end of the Visean (ca. 345 Ma). Thus, the Uralian collision between the NKT and Siberia (ca. 300 Ma) apparently did not affect the Severnaya Zemlya Archipelago.

This thesis uses geodetic satellite data to measure present-day crustal deformation in the Zagros fold-thrust belt (SW Iran). Geodetic-type measurements are also used in down-scaled models that simulate the surface deformations seen in convergent settings like the Zagros fold-thrust belt. Global Positioning System (GPS) measurements of three surveys between 1998 and 2001 indicate 9 ± 3 mm/yr and 5 ± 3 mm/yr shortening across the SE and NW Zagros respectively. GPS results show that in addition to the different rates and directions of shortening on either side of the NS trending Kazerun fault, local along-belt extension occurs to the east. Differential SAR interferograms of ERS1 & 2 images between 1992 and 1999 detect 8 ± 4 mm/yr uplift rate across a newly recognized fault in SW Qeshm Island. This can be attributed to a steep imbricate thrust that may still represent the local Zagros deformation front. The salt diapirs in the Zagros rise from a source layer that acts as a low-frictional decollement that decouples the deformation of the cover sediments from their basement in the eastern Zagros whereas the cover to the west deforms above a high-friction decollement. Physical models were prepared to simulate cover deformation in the Zagros by shortening a sand pack above adjacent high- and low-frictional decollements (represented by a ductile layer). The strain distributions differed above the two types of decollements; it was more heterogeneous above the salt where local extension in the shortening direction was dominant. A separate work also investigated systematically the role of basal friction on cover deformation in convergent settings. Accurate height measurements of the model surface by laser-scanner indicated a deformation front more distal than usual, particularly in the low-basal frictional models. The volume reduction in our shortened sand models correlated directly with their basal friction.

Ce travail comprend trois parties: dans la première nous précisons et développons la stratigraphie déjà connue ; nous établissons une stratigraphie du Mésocrétacé et du Flysch ; dans la deuxième je reprends la question des roches éruptives en lui donnant une signification nouvelle. Enfin, nous y faisons des remarques sur la position de la Nappe de la Simme. La troisième partie traitera de la Tectonique et, enfin , un dernier chapitre tentera d'exposer le problème de la provenance de la Nappe de la Brèche, tel que nous le concevons.

The Nicoya Peninsula of Costa Rica is unusually close to the Middle America Trench (MAT), such that interface locking along the megathrust is observable under land. Here, rapid convergence between the downgoing Cocos and the over-riding Caribbean plates at ~85mm/yr allows for observable high strain rates, frequent large earthquakes and ongoing micro-seismicity. By taking advantage of this ideal location, a network of 20 on-land broadband seismometers was established in cooperation between UC Santa Cruz, Georgia Tech, and OVSICORI, with most stations operating since 2008. To evaluate what seismicity tells us about the ongoing state of coupling along the interface, we must consistently evaluate the location and magnitude of ongoing micro- seismicity. Because of large levels of anthropogenic, biologic, and coastal noise, automatic detection of earthquakes remains problematic in this region. Thus, we resorted to detailed manual investigation of earthquake phases. So far, we have detected nearly 7,000 earthquakes below or near Nicoya between February and August 2009. From these events we evaluate the fine-scale frequency-magnitude distribution (FMD) along the subduction megathrust. The results from this b-value mapping‟ are compared with an earlier study of the seismicity 9 years prior. In addition, we evaluate them relative to the latest geodetically derived locking. Preliminary comparisons of spatial and temporal variations of the b-values will be reported here. Because ongoing manual detection of earthquakes is extremely laborious and some events might be easily neglected, we are implementing a match-filter detection algorithm to search for new events from the continuous seismic data. This new approach has been previously successful in identifying aftershocks of the 2004 Parkfield earthquake. To do so, we use the waveforms of 858 analyst-detected events as templates to search for similarly repeating events during the same periods that have been manually detected. Preliminary results on the effectiveness of this technique are reported. The overall goal of this research is to evaluate the evolution of stress along the megathrust that may indicate the location and magnitude of potentially large future earthquakes. To do so, I make the comparison between the FMD and the interface locking. Only positive correlations are observed in the Nicoya region. The result is different from the one derived from the seismic data set that was recorded 9 years before our data. Therefore, to substantiate the causes for the different relationships between the b-value and the coupling degree, we need additional data with more reliable magnitudes.

Cette thése est un travail sur deux massifs appartenant principalement aux Préalpes médianes. La stratigraphie, la tectonique et les relations de cette nappe avec les éléments tectoniques inférieurs (autochtone et Flysch à lentilles) et supérieures ( Flysch à Helminthoïdes ) sont étudiés.