GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 3.2 425 sediments deposited or reworked by bottom currents, which are also known sources of this type of layers (Rebesco, 2005) or a metastable fine-grained layer that liquified under cyclic loading (Barnes et al., 1991). The presence of a weak layer is consistent with the deposition of an unit at a lower sea-level as during glacial periods, and the information provided by the wells present in the study area. Indirect evidence of migrating fluids are pockmarks and the presence of polygonal faults. Other factors that had an impact on the seafloor stability are the rapid uplift since Early Pliocene and the erosion which can lead to a local oversteepening of the slope (Morgenstern, 1967). Conclusion. The integration of seabed mapping and acoustic facies represent a particularly useful tool in assessing geohazards and, in this case, determining the possible triggers of submarine landslides. The presence of gas in the sediments, combined with the identification of a weak layer constitute the main factors that controlled the occurrence of slope failures along the study area. Acknowledgements. The authors acknowledge the Italian Civil Protection for funding the MAGIC project and MIUR (Italian Ministry of University and Research) for funding the RITMARE project and HIS Kingdom Suite for providing the educational grant. We are also grateful to colleagues Andrea Cova and Edy Forlin for the processing of multibeam data in the framework of the MAGIC project. Geophysical data have been acquired on board of the R/V Explora. References Barnes P.M.; Lewis K.B.; 1991: Sheet slides and rotational failures on a convergent margin: the Kidnappers Slide, New Zealand. Sedimentology, 38, 205-221. Bunz S.; Mienert J.; Bryn P.; Berg K.; 2005: Fluid flow impact on slope failure from 3D seismic data: a case study in the Storegga Slide. Basin research, 17, 109-122. Fig. 2 – Location of the study area and the U2 unconformity which we infer may represent the glide plane for the mapped slope failures.