A multi-disciplinary investigation of the AFEN Slide: the relationship between contourites and submarine landslides

Abstract

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Diagenetic priming of submarine landslides in ooze-rich substrates

“…Seismic reflection data were tied to ODP 762 (see Appendix S3 for details), allowing us to corelate seismic character and sediment properties. Velocity and density data from ODP 762 provide a proxy record of sediment overpressure (Tingay et al, 2009), whereas water content and void ratio are used as proxies for sediment shear strength and compressibility (Gatter et al, 2020;Tanaka and Locat, 1999).…”

“…Hs is characterized by an upward decrease in Vp from 1.7 km/s and 1.52 km/s, and an increase in water content from 30.0% to 48.5% (Figure 1B). The extremely low velocity response at the level of Hs indicates possible underpressure at this horizon, whereas the high-water content response indicates Hs has higher compressibility and lower shear strength (Gatter et al, 2020). Nonetheless, direct measurements are needed to achieve a more accurate analysis of the sediment stability that using proxy measures from well data, which will improve future hazard assessments (see also Appendix S5).…”

“…These tectonicallydriven variations fundamentally controlled the benthic and planktonic foraminiferal assemblages (Kennett, 1985), and hence the abrupt contrast in lithology and physical properties at H2 that subsequently primed slides failure depth and location. The interplay of multiple physical processes on slide preconditioning can be felt thousands, or even millions, of years after their activity ceased (Gatter et al, 2020), thus cautioning against the simplistic linkage of sliding to an external trigger. We suggest that such a temporally-buffered connection likely exists for many other settings, where diverse tectonic, sedimentological and/or oceanographic process interactions form stratigraphically-constrained fluid sources, pathways, and permeability barriers (Gatter et al, 2021;Gatter et al, 2020).…”

Supplemental Material: Diagenetic priming of submarine landslides in ooze-rich substrates

“…bulk density to infer porosity; porosity to infer pore pressure; and water content to infer compressibility) and have been proved as an effective method in both siliciclastic and carbonate dominant settings (i.e. Herbert and Mayer, 1991;Tanaka and Locat, 1999;Martin et al, 2015;Gatter et al, 2020). We therefore consider that our approach is appropriate but also suggest that the findings of our study (based on proxy data) will provide a much-needed stimulus to acquire insitu measurements, and sediment cores that can be subject to detailed geotechnical analysis to make primary measurements of overpressure, shear strength and permeability of unfailed and failed sediments fill in key data gaps (as also emphasised in Gatter et al, 2020).…”

Channel and inter-channel morphology resulting from the long-term interplay of alongslope and downslope processes, NE Rockall Trough, NE Atlantic

“…Amy, 2019), in assessing the strength and stability of a slope and the associated geohazard (e.g. Gatter et al, 2020;Brackenridge et al, 2020;Georgiopoulou et al, 2019), and in palaeogeographic reconstructions where deposits like these are used to infer opening of oceanic gateways and new water mass connections leading to large-scale climatic changes (e.g. Jakobsson et al, 2007;Koenitz et al, 2008).…”