Integrated geophysical, sedimentological and geotechnical investigation of submarine landslides in the Gulf of Lions (Western Mediterranean)

Abstract

The Gulf of Lions presents recurring mass-transport deposits (MTDs) within the Plio-Quaternary sediments, suggesting a long history of mass movements. The two large, surficial MTDs are located on the eastern and western levee of the Rhone canyon over an area exceeding 6000 km2 and volumes exceeding 100 km3. Both MTDs were emplaced 21 ka ago (peak of the Last Glacial Maximum), suggesting a common trigger. Here, we present a multidisciplinary high-resolution geophysical, sedimentological and in-situ geotechnical study of the source and deposit areas of both MTDs to characterize distinct expressions of sediment deformation as well as their spatial and chronological distributions. We show the internal structure of mass movements and resulting MTDs with unprecedented details that were previously represented in the conventional seismic data as transparent and chaotic facies. The combination of multidisciplinary approaches shows new insights into the nature of basal surfaces of the slope failures. In particular, we show that the basal surfaces of the failures consist of clay-rich material contrasting with the overlying turbiditic deposits, suggesting that a strong lithological heterogeneity exists within the strata. We suggest that this change in lithology between clay-rich sediments and turbiditic sequences most likely controls the localization of weak layers and landslide basal surfaces.

Factors leading to slope failure on a sediment-starved margin: The southwestern continental margin of the East Sea, Korea

“…Changes in spatial and temporal heterogeneity in sedimentation on the slopes, due to climatic changes in the hinterland, tectonic activity, or sea-level fluctuations, can significantly precondition sediments for failure (e.g., Laberg et al, 2005;Badhani et al, 2020). For example, coarser-grained sediments, interpreted as grain flow deposits (Facies MgmS; Fig.…”

Seismic amplitude response to internal heterogeneity of mass-transport deposits

“…One indication that the seismic amplitude response is not straightforwardly related to preserved internal structure is that modern high-resolution geophysical datasets, particularly 3-D seismic volumes, have revealed previously unresolvable organisation and internal structure within MTDs as small as the metre to decametre scale (Bull et al, 2009;Gafeira et al, 2010;Alves and Lourenço, 2010;Bellwald and Planke, 2018;Badhani et al, 2020;Barrett et al, 2021). Another indication is that sediment core samples retrieved from seismically "transparent" bodies can sometimes show little evidence of internal deformation at core scale (tens of centimetres and lower) (Expedition 316 Scientists, 2009;Strasser et al, 2011;Sammartini et al, 2021;Fig.…”

Seismic Diffraction Imaging to Characterize Mass‐Transport Complexes: Examples From the Gulf of Cadiz, South West Iberian Margin

“…In academic settings, maximum offsets are typically limited relative to the target depth, meaning reflectors are often poorly illuminated, intrinsically limiting the lateral resolution. Improvements in imaging of academic data have typically come from novel acquisition geometries and seismic sources, such as ultra‐high‐resolution deep‐tow seismic (Badhani et al., 2020) and short‐offset 3D “P‐cable”‐type geometries (Berndt et al., 2012; Karstens et al., 2019). Such approaches can provide dramatic increases in seismic resolution within MTCs at the cost of significantly increased acquisition effort.…”