Characterising weak layers that accommodate submarine landslides on the Northwest African continental slope .

Urlaub, Morelia , Krastel, Sebastian, Geersen, Jacob and Schwenk, Tilmann (2017) Characterising weak layers that accommodate submarine landslides on the Northwest African continental slope . [Poster] In: AGU Fall Meeting 2017. , 11.12 - 15.12.2017, New Orleans, USA .

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Abstract

Numerous studies invoke weak layers to explain the occurrence of large submarine landslides (>100 km³), in particular those on very gentle slopes (<3°). Failure conditions are thought to be met only within this layer, which is embedded between stable sediments. Although key to understanding failure mechanisms, little is known about the nature and composition of such weak layers, mainly because they are (1) often destroyed with the landslide and (2) difficult to reach with ship-based gravity and piston coring. The Northwest African continental slope hosts numerous large submarine landslides that are translational, such that failure takes place along bedding-parallel surfaces at different stratigraphic depths. This suggests that failure occurs along weak layers, which are deposited repeatedly over time. Using high resolution seismic reflection data we trace several failure surfaces of the Cap Blanc Slide complex offshore Northwest Africa to ODP-Site 658. Core-seismic integration shows that the failure surfaces coincide with diatom oozes that are topped by clay. Along Northwest Africa diatom-rich sediments are typically deposited at the end of glacial periods. In the seismic data these oozes show up as distinct high amplitude reflectors due to their characteristic low densities. Similar high-amplitude reflectors embedded into low-reflective seismic units are commonly observed in shallow sediments (<100 m below seafloor) along the entire Northwest African continental slope. The failure surfaces of at least three large landslides coincide with such reflectors. As the most recent Pleistocene glacial periods likely influenced sediment deposition along the entire Northwest African margin in a similar manner we hypothesize that diatom oozes play a critical role for the generation of submarine landslides off Northwest Africa as well as globally within subtropical regions. An initiative to drill the Northwest African continental slope with IODP is ongoing, within which this hypothesis shall be tested.

Document Type: Conference or Workshop Item (Poster)
Research affiliation: Kiel University
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Date Deposited: 07 Dec 2017 14:38
Last Modified: 19 Dec 2017 10:55
URI: http://oceanrep.geomar.de/id/eprint/40453

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