1. Post-failure Processes on the Continental Slope of the Central Nile Deep-Sea Fan: Interactions Between Fluid Seepage, Sediment Deformation and Sediment-Wave Construction
- Author
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Silvia Ceramicola, Daniel Praeg, Jean Mascle, Sébastien Migeon, João Marcelo Ketzer, Flore Mary, Emmanuelle Ducassou, and Alexandre Dano
- Subjects
geography ,Gravity (chemistry) ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Deformation (mechanics) ,Continental shelf ,Sediment ,010502 geochemistry & geophysics ,01 natural sciences ,Deep sea ,Seafloor spreading ,chemistry.chemical_compound ,chemistry ,Carbonate ,Geomorphology ,Geology ,Seabed ,0105 earth and related environmental sciences - Abstract
Voluminous mass-transport deposits (MTD) have been identified on seismic profiles across the central Nile Deep-Sea Fan (NDSF). The youngest MTDs are buried under 30–100 m of well-stratified slope deposits that, in water depths of 1,800–2,600 m, are characterized by undulating reflectors correlated with slope-parallel seabed ridges and troughs. Seabed imagery shows that, in the western part of the central NDSF, short, arcuate undulations are associated with fluid venting (carbonate pavements, gas flares), while to the east, long, linear undulations have erosional furrows on their downslope flanks and fluid seeps are less common. Sub-bottom profiles suggest that the western undulations correspond to rotated fault-blocks above the buried MTDs, while those in the east are sediment waves generated by gravity flows. We suggest that fluids coming from dewatering of MTDs and/or from deeper layers generate overpressures along the boundary between MTDs and overlying fine-grained sediment, resulting in a slow downslope movement of the sediment cover and formation of tilted blocks separated by faults. Fluids can migrate to the seafloor, leading to the construction of carbonate pavements. Where the sediment cover stabilizes, sediment deposition by gravity flows may continue building sediment waves. These results suggest that complex processes may follow the emplacement of large MTDs, significantly impacting continental-slope evolution.
- Published
- 2013