Mass transport deposits form a significant portion of the rock record in both modern and ancient basins. Their geometry, composition, distribution and genesis are poorly understood, making it difficult to predict anything about these deposits in assessing subsurface basin stratigraphy or modern seafloor hazards. A tremendous effort has been made in the last few years to characterize and better understand seafloor failures in numerous margins of the world. These mass failures have triggered the interests of geologists, particularly in the oil and gas industry, as they can form prominent seals and reservoirs. To increase our knowledge base of mass transport complexes (MTCs), the characteristics of 259 siliciclastic deposits worldwide, were analyzed in terms of their volume, area, length, thickness, lithology, and tectonic settings. In some instances, MTCs were geo-referenced and digitized into ArcGIS and their dimensions were calculated. These data reveal several interesting points and suggest a number of statistically significant predictive relationships. Sand-rich mass transport deposits show a propensity to be short and thick. Muddy MTCs show a propensity to be longer and thinner. The highest number and largest volume of clastic mass transport deposits occur along passive margins. These mega-MTCs are typically muddy with lengths up to 800 km and volumes up to 5000 km3. Sandy and gravelly Quaternary-age MTCs show maximum lengths of less than 300 km and with volumes less than 2000 km3. Pre-Quaternary MTCs are systematically under-documented in literature, but known occurrences are found in passive, active and convergent margins. The largest (30,000 to 40,000 sq km) occur along the older Tertiary margin of West Africa. To date, 41 separate mass transport deposits composed dominantly of carbonate material have been identified in literature. The most extensive and voluminous (7000 km3) carbonate mass transport complexes occur in the Citronens Fjord, Offshore Greenland. They are 200m thick, Silurian-age mega-breccias that were deposited in a convergent margin setting. On comparison carbonate MTCs tend to show longer flows with coarser grain sizes, while clastics show coarser grained deposits to be of more limited length. The Mad Dog area, Gulf of Mexico is a region of active salt tectonics and mass transport processes. Consequently, it was selected to form a focus study area to test the relationships developed during this project. MTCs in this region were grouped into four main types based on their size, geomorphology and internal structure. Their geometries indicate they are comparable to MTCs found offshore Oregon and New Jersey and are most likely muddy in nature. / text

Submarine landslides retrogressively fail from intact material at the headwall and then become fluidized by strain weakening; the final deposits of these flows have low porosity, which controls their character in seismic reflection data. Submarine landslides occur on the open slope and also localized areas including margins of turbidite channel-levee systems. I develop and quantify this model with 3-D seismic reflection data, core and log data from Integrated Ocean Drilling Program Expedition 308 (Ursa Basin, Gulf of Mexico), flume experiments, and numerical modeling. At Ursa, multiple submarine slides over the last 60 ky are preserved as mass transport deposits (MTDs). Retrogression proceeded from an initial slope failure that created an excavated headwall, which reduced the horizontal stress behind the headwall and resulted in normal faults. Fault blocks progressively weakened until the gravitational driving stress imposed by the bed slope exceeded soil strength, which allowed the soil to flow for more than 10 km away from the source area. The resulting MTDs have lower porosity (higher bulk density) relative to non-failed sediments, which ultimately produces high amplitude reflections at the base and top of MTDs. In the laboratory, I made weak (low yield strength) and strong flows (high yield strength) from mixtures of clay, silt, and water. Weak flows generate turbidity currents while moving rapidly away from the source area. They create thin and long deposits with sinuous flow features, and leave behind a relatively smooth and featureless source area. In contrast, strong flows move slowly, do not generate a turbidity current, and create blocky, highly fractured source areas and short, thick depositional lobes. In Pleistocene turbidite channels of the Mississippi Fan, deep-seated rotational failures occurred in the flanking levees. The rotational failures displaced material into the channel from below where it became eroded by turbidity flows. This system achieved a delicate steady state where levee deposition and displacement along the fault into the channel was balanced by erosion rate of turbidity flows. This work enhances our understanding of geohazards and margin evolution by illuminating coupled processes of sedimentation, fluid flow, and deformation on passive continental margins. / text

Cette thèse porte sur la déformation et les migrations de fluides associées à la Faille Nord Anatolienne en Mer de Marmara (Turquie).Nous étudions tout d'abord l'évolution de la géométrie et du taux de glissement du système de faille, par deux approches indépendantes: - modélisation thermique de l'histoire d'un bassin, - définition d'un marqueur temporel de type Dépôt de Transport en Masse, daté par interprétation stratigraphique. Nous montrons que: -(1) le système de failles actuel, défini comme une faille principale accommodant la majorité de la déformation inter-plaque, n'a pas significativement évolué depuis 330.000 ± 100.000 ans dans la partie Ouest de la mer; -(2) le système de faille s'est progressivement réorganisé depuis 2.5-1.5 Ma.Dans un deuxième temps, nous étudions les processus d'initiation des Transports en Masse. Nous montrons que: -(1) même si les Transports en Masse sont contrôlés par des processus tectoniques (principalement les séismes et l'extension crustale), leur fréquence et leur taille sont conditionnées par les oscillations glacio-eustatiques; -(2) des Dépôts en Masse ont une périodicité corrélée aux transitions marins/lacustres. Cette cyclicité peut être expliquée par la diffusion d'eau saumâtre, dans les argiles marines entraînant leur gonflement et déstabilisant les sédiments. Dans une troisième partie, nous étudions la diversité des contextes des sites d'émissions de fluides en fonds de mer. Nous montrons que l'occurrence des sites d'émission de fluides est en partie liée au flux ascendant de gaz le long de couches perméables des bassins vers leurs bords, et le long des fractures du socle vers les bords des bassins et les anticlinaux. / This study addresses the issue on the deformation and the fluid migration, associated to the North Anatolian Fault within the Sea of Marmara (Turkey).First, we aim to constrain the evolution of the fault network and the slip rate through time, by two independent approaches: - historical thermal modeling of a basin of the Sea of Marmara; - definition of a Mass Transport Deposit as a fault lateral slip marker, and dated by stratigraphic interpretation. We show that: - (1) the present day fault system, formed by a main fault which accommodated the main part of the inter-plate deformation does not significantly evolved since 330.000 ± 100.000 years - (2) a progressive reorganization of the fault network occurred since the last 2.5-1.5 Ma.Secondly, we discuss the triggers of Mass Transport Processes. We show that: - (1) despite submarine mass movements are related to tectonic activity (mainly earthquakes and crustal stretching), their frequency and their size are also modulated by glacio-eustatic changes; -(2) remarkable Mass Transport Deposits display some cyclicity in stratigraphic sequences which are apparently correlated to transitions between salty marine and lacustrine environments. This cyclicity is perhaps explained by marine clay activity (swelling) under low brackish-fresh water conditions, which can trigger sediment destabilization.Third, we investigate the diversity of active fluid seepages contexts. We propose that the widespread occurrence of fluid expulsion sites can be explained by up-dip gas migration by buoyancy along permeable strata toward their edges, and along fractures within the basement toward both the edges of the basins and topographic highs.