Determining the drivers and mechanisms of Quaternary submarine megaslides on the North Sea Fan using high-resolution seismic datasets

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"This project uses seismic datasets covering the Northeast Atlantic Margin to analyse how glacial sedimentation changes with ice sheet margin fluctuations. In particular, it focuses on the North Sea Fan, a large depocentre at the head of the former Norwegian Channel Ice Stream, and the Quaternary Period submarine slides that have been identified within the layered structure of the fan. The deepest and oldest of these, the Stad Slide, has been poorly studied until now as a result of its depth and a lack of high enough resolution seismic data. Making use of new high-resolution datasets, this study analyses the morphology and sedimentology of the Stad Slide to reveal more about the triggers, preconditions, and mechanisms of the event, including the glacial conditions under which it was possible. This will be compared to other slides within the fan and further afield to reveal broader patterns surrounding megaslides and their relation to fluctuating ice sheet margins. Trough mouth fans (TMFs) form at the head of glacial troughs, where fast-flowing outlet glaciers (ice streams) efficiently erode sediment. This sediment is expelled at the ice stream margin on the continental slope, forming a progradational wedge of sediment. The North Sea Fan (NSF), at the head of the Norwegian Channel, which during the Quaternary intermittently hosted the Norwegian Channel Ice Stream, is a TMF which forms a major depocentre on the continental slope of the southeast Nordic Sea. The 32,000km3 layered sedimentary record the NSF contains hosts a wealth of information on glacial and oceanic conditions since its early Pleistocene inception. Within the structure of the NSF, several large-scale submarine slides have been identified. Rapid glacial sedimentation combined with formation of interglacial "weak" sedimentary layers are often cited as the mechanisms behind such large slides on glacial margins. However, there are still gaps in current understanding of the triggers and progression of such slides. The Storegga Slide (8.1kya) forms the most recent and is visible on the modern-day seafloor to the northeast of the NSF. Three more have been identified within buried NSF layers: the Tampen (0.15Mya), More (0.4Mya), and Stad Slides (0.5Mya). The Stad Slide forms the deepest and possibly largest slide in the NSF. Until recently detailed study of this deep (700-1000m below the seafloor) slide has been impossible. However, new high-resolution seismic data means that detailed analysis is now feasible. This research therefore aims to perform a detailed analysis of the NSF megaslides, with a particular focus on the Stad Slide. This involves morphological and sedimentological analysis to reveal more about slide drivers and progression, and how this can be linked to ice sheet behaviour, such as the mode and pace of sediment delivery to TMFs. Comparison with other slides will reveal more about the universal and local drivers and progression of submarine slope failures. The project uses extensive seismic datasets from the Northeast Atlantic Margin. Seismic data image buried seafloor surfaces, with the differences in acoustic signature between different sediment types allowing reconstructions of past sedimentation. Seismic geomorphology can reveal larger-scale patterns, for example by identifying buried landforms indicative of glacial activity. This technique has been used to analyse the NSF and submarine slides in detail, and the increasing resolution at depth of such datasets now renders the Stad Slide open to similar analysis. Research Questions1) What can be inferred from the structure and morphology of the Stad Slide about its drivers and mechanisms?2) What differences and similarities are there between the Stad Slide and other submarine megaslides on the NSF, and what does this reveal about their relative drivers and nature?3) What can these slides reveal about Quaternary fluctuations in the Eurasian Ice Sheet?"