The stratigraphic evolution of exhumed submarine lobes in unstable and complex basin margins

Submarine fans are the largest sediment accumulations on Earth and form valuable archives for paleoclimatic and paleogeographic reconstructions. Sand-rich lobes are a major fan component, recording erosion and transport of clastic sediments from terrestrial highs to deep-marine lows. Submarine lobe evolution and architecture are inherently linked to complex interactions between sediment gravity flow processes and the evolving physiography of continental slopes, which induces complex facies transitions and pinch-out styles. In the subsurface, predictions of the pinch-out character at bed- to lobe-scale are limited by the resolution of seismic reflection data and sparse borehole coverage. To bridge the resolution gap, this thesis presents three field-based studies of exceptionally well-exposed examples of intraslope lobes associated with submarine landslide deposits (frontal lobes from the Neuquén Basin, Argentina, and crevasse lobe Aínsa Basin, Spain) and develops new models for submarine lobes developed above inherited tectonic and depositional relief and compares the impact of variable degree of confinement in each system. The main outcomes and novelty of this thesis are 1) the relief along the upper surfaces of submarine landslides can be hierarchical and highly dynamic, which influences the behaviour of gravity flows in more complex ways than simple passive healing of topography; 2) seafloor relief can be rejuvenated progressively due to compaction-driven deformation, or more abruptly due to catastrophic mass failures, which is recorded by the architecture and stacking patterns of lobes; and 3) intraslope lobes can be dominated by transitional flow deposits where immature routing pathways and clay-rich and poorly-consolidated substrates are present, such as in post-rift settings. Therefore, this thesis highlights the inherent complexity of sedimentary processes along unstable slopes, which demonstrably impacted the nature of the investigated lobes.