Yes

Hydrate Ridge is a peanut shape bathymetric high located about 80 km west of Newport, Oregon on the Pacific continental margin, within the Cascadia subduction zone’s accretionary wedge. The ridge's two topographic highs (S. and N. Hydrate Ridge) are characterized by gas vents and seeps that were observed with previous ODP initiatives. In 2008, we acquired a 3D seismic reflection data set using the P-Cable acquisition system to characterize the subsurface fluid migration pathways that feed the seafloor vent at S. Hydrate Ridge. The new high-resolution data reveal a complex 3D structure of localized faulting within the gas hydrate stability zone (GHSZ). We interpret two groups of fault-related migration pathways. The first group is defined by regularly- and widely-spaced (100-150 m) faults that extend greater than 300ms TWT (~ 250 m) below seafloor and coincide with the regional thrust fault orientations of the Oregon margin. The deep extent of these faults makes them potential conduits for deeply sourced methane and may include thermogenic methane, which was found with shallow drilling during ODP Leg 204. As a fluid pathway these faults may complement the previously identified sand-rich, gas-filled stratigraphic horizon, Horizon A, which is a major gas migration pathway to the summit of S. Hydrate Ridge. The second group of faults is characterized by irregularly but closely spaced (~ 50 m), shallow fractures (extending < 160ms TWT below seafloor, ~ 115 m) found almost exclusively in the GHSZ directly beneath the seafloor vent at the summit of S. Hydrate Ridge. These faults form a closely-spaced network of fractures that provide multiple migration pathways for free gas entering the GHSZ to migrate vertically to the seafloor. We speculate that the faults are the product of hydraulic fracturing due to near-lithostatic gas pressures at the base of the GHSZ. These fractures may fill with hydrate and develop a lower permeability, which will lead to a buildup of gas pressures below the GHSZ. This may lead to a vertical propagation of new fractures to release the overpressure, which results in the high concentration of shallow fractures within the GHSZ seen in the 2008 data. / text

This dissertation investigates contractional fault-related folding, an important mechanism of deformation in the brittle crust, using a range of kinematic and mechanical models and data from natural structures. Fault-related folds are found in a wide range of tectonic settings, including mountain belts and accretionary prisms. There are several different classes of fault-related folds, including fault-bend, fault-propagation, shear-fault-bend, and detachment folds. They are distinguished by the geometric relationships between the fold and fault shape, which are driven by differences in the nature of fault and fold growth. The proper recognition of the folding style present in a natural structure, and the mechanical conditions that lead the development of these different styles, are the focus of this research. By taking advantage of recent increases in the availability of high-quality seismic reflection data and computational power, we seek to further develop the relationship between empirical observations of fault-related fold geometries and the kinematics and mechanics of how they form. In Chapter 1, we develop an independent means of determining the fault-related folding style of a natural structure through observation of the distribution of displacement along the fault. We derive expected displacements for kinematic models of end-member fault-related folding styles, and validate this approach for natural structures imaged in seismic reflection data. We then use this tool to gain insight into the deformational history of more complex structures. In Chapter 2, we explore the mechanical and geometric conditions that lead to the transition between fault-bend and fault-propagation folds. Using the discrete element modeling (DEM) method, we investigate the relative importance of factors such as fault dip, mechanical layer strength and anisotropy, and fault friction on the style of structure that develops. We use these model results to gain insight into the development of transitional fault-related folds in the Niger Delta. In Chapter 3, we compare empirical observations of fault-propagation folds with results from mechanical models to gain insight into the factors that contribute to the wide range of structural geometries observed within this structural class. We find that mechanical layer anisotropy is an important factor in the development of different end-member fault-propagation folding styles. / Earth and Planetary Sciences

Les rides de Barracuda et de Tiburon sont deux reliefs sous-marins situés dans la partie ouest de l'océan Atlantique, là où la lithosphère océanique des plaques Amérique du Nord (NAM) et Amérique du Sud (SAM) est entraînée par subduction sous la plaque Caraïbe, formant l'arc volcanique des Petites Antilles et le prisme d’accrétion de Barbade. Le processus et la période de soulèvement conduisant au relief actuel de ces rides (qui semblent être un marqueur important dans l'histoire géodynamique de la région) sont sujets à débat depuis des décennies.L’interprétation de nouvelles données de sismique réflexion et de bathymétrie multifaisceaux acquises à travers les rides de Barracuda et de Tiburon (campagne Antiplac, 2007 ) a permis de dater les périodes de soulèvements des rides et réaliser des reconstructions paléogéographiques incluant les flux sédimentaires majeurs, depuis le Crétacé jusqu’ à l’Actuel.L’analyse structurale révèle des phases de réactivations tardives d’anciennes zones de fractures dans un contexte transpressif, conduisant aux surrections des rides de Tiburon et de Barracuda.Les processus géologiques possibles impliqués dans la formation des rides de Barracuda et de Tiburon coïncident avec les modèles cinématiques récents décrivant les mouvements relatifs entre les plaques NAM et SAM, le long de la limite de plaque diffuse.Ces résultats permettent de mieux définir la limite de plaque entre NAM et SAM. Elle est nécessairement hétérogène exploitant les zones de faiblesses dans la lithosphère que sont les zones de fracture. Au sein de cette limite de plaque la lithosphère serait donc fragmentée. / The Barracuda Ridge and the Tiburon Rise, two oceanic-basement ridges, lie in the western Atlantic Ocean, where oceanic lithosphere of the North American (NAM) and South American (SAM) plates is subducted beneath the Caribbean plate, creating the Lesser Antilles volcanic arc and the Barbados Ridge accretionary complex. The process and the timing of the uplift leading to the present day morphologies of the Tiburon and Barracuda ridges, that seem to be key markers in the geodynamic history of the region, has remained a matter of debate for decades.From the analysis of new multibeam and seismic reflection profiles acquired in 2007 (Antiplac crusie) DSDP-ODP boreholes available, we provide new information on the timing of the formation of the Barracuda Ridge and Tiburon Rise in their present-day configurations. We propose paleogeographic reconstructions with the main sediments fluxes deposited in the area of the Barracuda and Tiburon ridges from the Late Cretaceous to present. Structural analysis shows reactivation of fracture zones in a transpressive setting leading to the uplifts of the Barracuda and Tiburon Ridges.The location of the Barracuda Ridge and the Tiburon Rise and the timing of the uplift fit well with recent global plate kinematic models describing the movements of NAM relative to SAM along a diffuse plate boundaryThis NAM-SAM plate boundary zone, therefore must most certainly be heterogeneous in nature, exploiting weaknesses in the lithosphere provided by fracture zones where mechanically advantageous, but forming new boundary segments elsewhere, to transfer motion between reactivated segments of the fracture zones.