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Extensive overwash occurred along Florida's Atlantic and northern Gulf facing barrier islands during the passages of Hurricanes Frances, Ivan, and Jeanne in 2004. These high-energy storm events provided a unique opportunity to study the spatial depositional patterns and internal sedimentary architecture of fresh washover deposits resulting from inundation to collision regime overwash events. Sedimentological characteristics and 3-D internal architecture of the washover deposits were studied through coring, trenching, sediment analysis, ground penetrating radar (GPR) surveys, and pre- and post-storm aerial photography and LiDAR topographic survey data. The cross-shore extent of washover deposition is controlled by sediment supply, accommodation space, and the extent of cross-shore penetration of overwash flow. Antecedent morphology of the beach or barrier island is the primary factor governing sediment supply and accommodation space. Antecedent morphology coupled with spatio-temporal factors including storm position, intensity, and duration govern the extent of landward excursion of overwash flow. Washover deposition ranges from thin deposits, limited in cross-shore extent to the beach berm, to extensive sheet-like sediment bodies extending across an entire barrier island profile. Four sedimentary facies are recognized, which can be related to antecedent morphology. Berm facies, dominates the beach and seaward side of the foredune, and is characterized by a basal erosional surface and seaward dipping planar stratification. Back-berm facies extends landward from the dune crest down the backside of the foredune, exhibits little evidence of erosion along the basal contact, and is dominated by landward inclined stratification. Platform facies, largely confined to the interior platform, exhibits little evidence of erosion along the pre-storm surface, and horizontal to gently landward dipping parallel stratification, which merges landward with, and commonly overlies steeply landward dipping foreset stratification. Antecedent hummocky dunes may be preserved within platform facies. The landward most facies, backbay facies is dominated by subaqueous deposition within the back bay, and is characterized by steeply landward dipping tabular foreset and sigmoidal stratification. In the longshore direction, backbay facies exhibit trough and mound GPR reflective patterns, representing washover sediment ridges and troughs oriented parallel to the primary flow direction, and illustrate the highly 3-dimesional nature of the washover deposits.

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L’architecture crustale et l’évolution de la partie profonde des marges passives peu-magmatiques sont encore mal comprises. En prenant comme chantier principal les marges Australie-Antarctique, cette thèse montre que l’enregistrement de la déformation dans les sédiments met en évidence une évolution polyphasée des marges distales. Cette évolution polyphasée implique le développement de multiples systèmes de détachement présentant une organisation hors-séquence et menant à une architecture finale symétrique des domaines exhumés. Cette organisation des systèmes de failles est liée à des cycles de délocalisation / relocalisation de la déformation influencés par l’apport magmatique, par un niveau de découplage et par la remontée asthénosphérique. L’interaction faille / magma apparait particulièrement importante dans l’évolution des marges distales. Cette étude a permis de mieux caractériser la rupture lithosphérique, qui peut se définir comme un événement tectono-magmatique progressif. / The crustal architecture and evolution of the deepest part of magma-poor rifted margins is currently not well understood. Taking the Australia-Antarctica margins as main study area, this thesis shows that the record of the deformation in sediments highlights a clear polyphase evolution of distal margins. This polyphase evolution implies the development of multiple detachment systems presenting an out-of-sequence organization and leading to a final symmetric architecture of the exhumed domains. This organization of fault systems is linked to cycles of delocalisation / re-localisation of the deformation influenced by the magmatic supply, by a decoupling level and by the asthenospheric uplift. Fault / magma interaction appears particularly important during the evolution of distal margins. This study allowed a better characterization of the lithospheric breakup, which can be defined as a progressive tectono-magmatic event.