Large Quaternary plastered drifts characterise the slope and base of slope of the area between the Guadiaro and Baños turbidite systems (Alboran Sea). A terraced contourite drift has developed between 190 and 600 meters water depth (mwd). Seawards, another plastered drift extends from a scarpat 600 mwd to beyond the base of slope. The sedimentary and physical properties of the contourite drifts allowed establishing a geotechnical model that reveals high factors of safety. The sediments evolve from granular, low plasticity and very poorly sorted on the contourite terrace to medium-to high-plasticity, low-permeability and poorly sorted silty clayey-sediments on the distal contourites at the base of slope. These characteristics are consistent with the geotechnical model defined by the in-situ properties and SBT (Soil Behaviour Types) classification. The coarse-grained sediments, are defined by cohesion (c′) and internal friction angle (ϕ′)values of0-9 kPa and 46-30º, respectively. The undrained shear strength gradient (∇Su) is 2 kPa/m for distal contourites. These properties allow assessing high factors of safety (FoS), for all the scenarios considered, including seismic loading. Several characteristics and processes may explain the high stability compared to others with similar sedimentary features. These include 1) the geometry of the drifts, defined by an upper contouritic terrace and low-mounded cross-sections; and 2) recurrent low intensity earthquakes and cyclic loading induced by internal waves, both favouring the dynamic compaction

This research was supported by the Spanish Fauces project (CTM2015-65461-C2-1-R). This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). We are also grateful for the data we received from the Viatar project (http://datos.ieo.es/)

X Simposio sobre el Margen Ibérico Atlántico - X Simpósio sobre a Margen Ibérica Atlántica, 7-9 de julio de 2022, Bilbao

Peer reviewed