FN Archimer Export Format PT J TI Soft sediment deformation in the shallow submarine slope off Nice (France) as a result of a variably charged Pliocene aquifer and mass wasting processes BT AF KOPF, Achim J. STEGMANN, Sylvia GARZIGLIA, Sebastien HENRY, Pierre DENNIELOU, Bernard HAAS, Simon WEBER, Kai-Christian AS 1:1,2;2:1,2;3:3;4:4;5:3;6:1,2;7:1,2; FF 1:;2:;3:PDG-REM-GM-LAD;4:;5:PDG-REM-GM-LGS;6:;7:; C1 Univ Bremen, Ctr Marine Environm Sci, Marine Geotech, MARUM, Bremen, Germany. Univ Bremen, Fac Geosci, Bremen, Germany. IFREMER, Ctr Brest, IFREMER, Plouzane, France. Univ Aix Marseille III, Coll France, CEREGE, Aix En Provence, France. C2 UNIV BREMEN MARUM, GERMANY UNIV BREMEN, GERMANY IFREMER, FRANCE UNIV AIX MARSEILLE, FRANCE SI BREST SE PDG-REM-GM-LAD PDG-REM-GM-LGS IN WOS Ifremer jusqu'en 2018 copubli-france copubli-europe copubli-univ-france IF 2.373 TC 17 UR https://archimer.ifremer.fr/doc/00343/45397/44894.pdf LA English DT Article CR HALIGURE BO Haliotis DE ;Soft sediment deformation;Submarine landslide;Weak zone;Fluidisation AB Along the Ligurian slope near Nice, southeastern France, a combination of natural and man-made factors govern slope stability, and contributed to a devastating tsunamigenic landslide near Nice airport in 1979. Based on a total of 72 gravity and Kullenberg cores we characterise the architecture and facies of the subbottom sediment. A total of six sedimentary facies types were observed, three of which represent the Pliocene – Holocene background sediment in the wider Nice area while another three are associated with the 1979 landslide and tsunami. The three primary facies types are soft silty clay/clayey silt, somewhat indurated silt/sand interbeds, and Pliocene conglomerates underlying the former. The three other facies are poorly sorted mass wasting deposits up to pebble size, silt representing the finer fraction of the mobilised mass, and a tsunami-related bed into which plant debris and artefacts got amalgamated. Accompanying geotechnical results attest that significant strength variations exist when comparing measurements from the narrow shelf, shelf break and shallow slope as well as the 1979 slide scar. Factors such as groundwater charging in the more permeable horizons further lower the effective stress and, in places, approach lithostatic. Above such permeable silt/sand beds, deformation of soft clay is observed, suggesting that leaching of ions from the clay mineral surfaces and frayed edges also facilitates weakening and creep, micro-slumping and folding. Elevated water supply as well as hydraulic fracturing of the clayey sediment is further attested by pipes of cm-diameter and several decimeters length, which entrained very soupy mud. In the shallowmost deposits in and landward of the slide scar, we also observe remnants from the catastrophic deposition associated with the 2-3 m high tsunami wave triggered in 1979, as attested by amalgamated sea grass and artifacts. Based on our observations and measurements on core-scale and earlier models based on in situ CPTu, we suggest that a significant part of the Quaternary delta and slope apron deposits are prone to being mobilised without a large external trigger, so that all in all a high risk for a landslide event of considerable size off Nice international airport is identified. PY 2016 PD OCT SO Sedimentary Geology SN 0037-0738 PU Elsevier Science Bv VL 344 UT 000387834300021 BP 290 EP 309 DI 10.1016/j.sedgeo.2016.05.014 ID 45397 ER EF