Abstract
Abstract The southern Tyrrhenian continental margin is the product of Pliocene–Recent back-arc extension. An area of approximately 30 km 2 of gentle (about 1.5°) lower slope of the last glacial outer shelf sedimentary wedge in water depths of between 200 and 300 m failed between 14 and 11 ka BP. We approached the landslide by multibeam and sub-bottom profiler surveying, high-resolution multichannel seismics, and coring for stratigraphic and geotechnical purposes. With regard to a slope-stability analysis, we carried out an assessment of the stratigraphic and structural setting of the area of the Licosa landslide. This analysis revealed that the landslide detached along a marker bed that was composed of the tephra layer Y-5 ( c. 39 ka). Several previously unknown geological characteristics of the area are likely to have affected the slope stability. These are the basal erosion of the slope in the Licosa Channel, a high sedimentation rate in the sedimentary wedge, earthquake shaking, the volcanic ash nature of the detachment surface, subsurface gas/fluid migration, and lateral porewater flow from the depocentre of wedge to the base of the slope along the high-permeability ash layers. A newly discovered prominent structural discontinuity is identified as the fault whose activity may have triggered the landslide.
Highlights
Modern submarine landsides often occur, paradoxically, in areas of the seafloor where morphological and geological characteristics suggest gravitational stability
The detachment surface of the Licosa landslides coincides with a marker bed composed of the tephra layer Y-5 (c. 39 ka) correlated to the Campanian Ignimbrite deposit generated by Phlegrean Fields super-eruption and caldera collapse
The Licosa landslide mass-transport deposit (MTD) traced into the Licosa Channel, where it attains a maximum thickness of 25 m and a lateral extent of 600 m, there is another, older MTD with a maximum thickness of about 17 m and a lateral extent of 220 m
Summary
Modern submarine landsides often occur, paradoxically, in areas of the seafloor where morphological and geological characteristics suggest gravitational stability. The Licosa submarine landslide, originally identified and described by Trincardi & Field (1992), is located between 200 and 300 m water depth just seawards of the shelf break (Fig. 1) It affected an area of the seafloor of about 30 km, on the seawards termination. The slip plane is a smooth and continuous surface dipping seawards by about 1.5°–3°, probably exposed after the failure as a result of complete mobilization of sediments above it It is covered by about 65 cm of post-slide sedimentary drape (Iorio et al 2014). The landslide has been dated about 14 ka cal BP by Trincardi et al (2003), who suggested a failure by a sudden increase in porewater pressure induced by rapid global sea-level rise (Meltwater Pulse 1A) on a slope preconditioned to failure by high sedimentation rates during the growth of the lowstand sedimentary wedge. Several open questions were left after the initial assessment of the landslide: Is rapid sea-level rise the only preconditioning factor involved in decreasing the sediment shear strength? Does the age refinement introduced by Iorio et al (2014) impose the identification of alternative factors? What is the role of widespread and often thick ash layers in the slope stability? Is there a fluid-flow component relevant to the slope stability? And, where is the source of ground shaking capable of triggering a landslide?
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
