Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Complex multifault earthquake ruptures involving secondary faults emphasize the necessity to characterize their seismogenic potential better and study their relationship with major faults to improve the seismic hazard assessment of a region. High-resolution geophysical data were interpreted to make a detailed characterization of the Averroes Fault and the North Averroes Faults, which are poorly known secondary right-lateral strike-slip faults located in the central part of the Alboran Sea (western Mediterranean). These faults appear to have evolved since the Pliocene as part of a distributed dextral strike-slip shear zone in response to local strain engendered by the diverging movement of the Carboneras Fault to the north, and the Yusuf and Alboran Ridge faults to the south. In addition, the architecture of these faults suggests that the Averroes Fault may eventually link with the Yusuf fault, thus leading to a higher seismogenic potential. Therefore, these secondary faults represent a hitherto unrecognized seismogenic hazard since they could produce earthquakes up to moment magnitude (Mw) 7.6. Our results highlight the importance of the role played by secondary faults in a specific kinematic framework. Their reciprocal linkage and their mechanical relationship with the main faults could lead to future complex fault ruptures. This information could improve fault source and earthquake models used in seismic and tsunami hazard assessment in this and similar regions.

This study reports the composition and distribution of demersal megafauna from various north-western Mediterranean submarine areas such as canyons, seamounts and landslides between 60–800 m depth, based on remotely operated vehicle (ROV) observations. From a total of 30 h of video, 4534 faunistic observations were made and analysed in relationship to environmental factors (i.e. topography, substrate type and depth). In addition, anthropogenic impact was quantified by grouping observations in four categories: fishing nets, longlines, trawl marks and other litter. The different targeted environments showed similarities in faunal composition according to substrate, depth and topography. Our results also indicated the presence of anthropogenic impact in all the sampled areas in which litter and trawl marks were the most observed artefacts.

This study focuses on the extraction of climate signals and processes using a combined approach which includes the analysis of a high number of lipid molecules in marine sediments, and the chemometric analysis of the acquired data. Neutral and acidic fractions of marine sediments from site IODP-U1318 (south-west of the UK, Porcupine Seabight) were quantified by GC-MS. The alkenone unsaturation index, U(k')37, was estimated from the composition of C37 alkenones and it was then used for the estimation of sea surface temperatures (SST) for reference. Principal component analysis (PCA), explained 77.45% of the total data variance, and differentiated neutral fraction GC-MS total ion current (TIC) profiles according to SST values of the different sediment sections. GC-MS TIC chromatograms were correlated to sea surface temperatures (SST) by partial least squares regression (PLSR). The compounds more robustly in line with SST values at each sediment section explained 93% of the SST variance and they were identified using the variable importance in projection (VIP) scores method. The proposed approach enables an objective identification of organic compounds sensitive to SST variability throughout complete chromatographic profiles. As a result of this multivariate unbiased approach, lipid composition of sediments was differentiated between compounds of marine (long chain n-alkanes, long chain n-alkan-1-ols) and terrestrial (short chain n-alkan1-ols, alkenols, cholesterol, squalene) origin, whose concentrations were directly and inversely correlated to SST, respectively.

We used high-resolution swath-bathymetry data to characterise the morphology of the abandoned subaqueous Sol de Riu delta lobe in the Ebro Delta, Western Mediterranean Sea.This study aims to assess the influence of an abandoned delta lobe on present-day coastal dynamics in a micro-tidal environment.Detailed mapping of the relict Sol de Riu lobe also showed a set of bedforms interpreted as footprints of human activities: seasonal V-shaped depressions on the middle shoreface due to boat anchoring and old trawling marks between 16 and 18 m water depth.Estimations of the mobility of bottom sediment showed that the shallowest shoreface (i.e. less than 7 m depth) is the most dynamic part of the relict lobe, while the middle shoreface experienced significant morphological changes since the lobe was abandoned.The deepest shoreface (i.e.water depth in excess of 15 m), which corresponds to the front of the lobe, is defined by a very small potential for morphological change.Simulations showed that while the relict lobe does not significantly affect the typical short period waves (T p ≈4 s) in the study area, it does interfere with the most energetic wave conditions (T p ≥ 7 s) acting as a shoal leading to the concentration of wave energy along the shoreline northwest of the lobe.The consequence of such modification of the high-energy wave propagation pattern by the relict lobe is an alteration of the waveinduced littoral sediment dynamics with respect to a situation without the lobe.

The Messinian Salinity Crisis (MSC) resulted from a significant multi-phase drop and subsequent reflooding of the Mediterranean Sea from 5.96 to 5.33 Ma. Well-developed drainage networks, characterized by step-like profiles and abrasion platforms, are associated to this event. The Ebro Continental Margin (Western Mediterranean) presents an additional complexity since the capture of the drainage of the adjacent subaerial Ebro Basin took place sometime prior to the Messinian stage. Using 3D seismic reflection data, this work provides new insights into the origin of the step-like profile of the Messinian erosional surface (MES) and timing of the capture of the subaerial Ebro Basin. The results obtained indicate a sedimentary-active continental slope and delta progradation during Middle-Late Miocene, in a normal regressive context associated to a pre-Messinian proto-Ebro River. The mature development attained by the Messinian Ebro River network during the MSC corroborates that the capture of the Ebro Basin occurred prior to the MSC. The configuration of the clinoforms below the MES suggests that deltaic sediments of the Messinian Paleo-Ebro River deposited during the Tortonian and initial Messinian sea-level drawdown. The MES formed at the top of the Tortonian Highstand, where a fluvial network was deeply carved, and in the topset region of the Messinian Falling Stage Systems Tract, where minor erosion occurred. Fluvial deposits are outstandingly preserved on the main valleys of the MES. Therefore, the step-like profile of the MES was not created during Zanclean inundation, but during the latest stages of the main Messinian sea-level fall and lowstand.

Climate variations control sediment supply to the continental slope as well as glacial advances and retreats, which (a) cause significant stress changes in the sedimentary column and redistribution of interstitial fluids, (b) induce a particular margin stratigraphic pattern and permeability architecture and (c) are at the origin of isostatic adjustments that may reactivate faults. We test this hypothesis using a combination of geophysical and geotechnical data from the Storfjorden Trough Mouth Fan, off southern Svalbard. The results of compressibility and permeability testing are used together with margin stratigraphic models obtained from seismic reflection data, as input for numerical finite elements models to understand focusing of interstitial fluids in glaciated continental margins and influence on timing and location of submarine slope failure. Available results indicate values of overpressure of 0.23-0.5 (slope-shelf) that persist to present-day. This overpressure started to develop in response to onset of Pleistocene glaciations and reduced by half the factor of safety of the continental slope.

•Litter was found in all samples taken from 900 to 3000m depth in the Mediterranean.•Plastics, glass, metal and clinker were the most abundant litter types.•Litter in the canyon is mostly coastal, litter on the slope is mostly from ships.•Litter is transported down-slope and accumulates at depth.•Megafauna biomass and litter weight were similar in many study sites.

The distribution, type and quantity of marine litter accumulated on the bathyal and abyssal Mediterranean seafloor has been studied in the framework of the Spanish national projects PROMETEO and DOS MARES and the ESF-EuroDEEP project BIOFUN. Litter was collected with an otter trawl and Agassiz trawl while sampling for megafauna on the Blanes canyon and adjacent slope (Catalan margin, north-western Mediterranean) between 900 and 2700 m depth, and on the western, central and eastern Mediterranean basins at 1200, 2000 and 3000 m depth. All litter was sorted into 8 categories (hard plastic, soft plastic, glass, metal, clinker, fabric, longlines and fishing nets) and weighed. The distribution of litter was analysed in relation to depth, geographic area and natural (bathymetry, currents and rivers) and anthropogenic (population density and shipping routes) processes. The most abundant litter types were plastic, glass, metal and clinker. Lost or discarded fishing gear was also commonly found. On the Catalan margin, although the data indicated an accumulation of litter with increasing depth, mean weight was not significantly different between depths or between the open slope and the canyon. We propose that litter accumulated in the canyon, with high proportions of plastics, has predominantly a coastal origin, while litter collected on the open slope, dominated by heavy litter, is mostly ship-originated, especially at sites under major shipping routes. Along the trans-Mediterranean transect, although a higher amount of litter seemed to be found on the Western Mediterranean, differences of mean weight were not significant between the 3 geographic areas and the 3 depths. Here, the shallower sites, also closer to the coast, had a higher proportion of plastics than the deeper sites, which had a higher proportion of heavy litter and were often affected by shipping routes. The weight of litter was also compared to biomass of megafauna from the same samples. On the Blanes slope, the biomass of megafauna was significantly higher than the weight of litter between 900 and 2000 m depth and no significant differences were found at 2250 and 2700 m depth. Along the trans-Mediterranean transect, no significant differences were found between biomass and litter weight at all sites except in two sites: the Central Mediterranean at 1200 m depth, where biomass was higher than litter weight, and the Eastern Mediterranean at 1200 m depth, where litter weight was higher than biomass. The results are discussed in the framework of knowledge on marine litter accumulation, its potential impact on the habitat and fauna and the legislation addressing these issues.

The sill of the Strait of Gibraltar is the morphological and oceanographic gateway between the Atlantic Ocean and the Mediterranean Sea for the post-Messinian period. It was surveyed by multibeam echosounder. TOPAS profiler, and 380 grab samples to study the distribution of cold-water corals. The sill represents an elevated seabed topography characterized in its central part by two main "mounts" separated by E-W oriented depressions. The irregular morphology suggests a rocky aspect, which is confirmed by the TOPAS profiler data showing a thin veneer of sediment or bare rocks. Low sedimentation is enforced by an extremely variable and strong current regime. Overall N-S elevated morphological structures dominate the sill area as an expression of the tectonic stress field and represent Early Pliocene flysch outcrops. Pliocene and/or Quaternary sediments consist mainly of calcareous conglomerates and cold-water coral accumulations, as well as sands and in the deeper part, muddy sediments. Cold-water coral distribution is related to elevated seafloor morphology of various sizes and low-sedimentation environments.

Submarine slope failures are a well-known geohazard. They are able to destroy seafloor installations along their path and by generating tsunamis they may threaten coastal infrastructures. While the mechanisms involved in submarine landslide generation remain poorly known, there are observations that slope stability can be reduced in the presence of free gas. Here, we present new high-resolution 3D seismic data from the Eivissa Channel between the Iberian Penninsula and the Balearic Promontory in the Western Mediterranean Sea. The data reveal slope stability reduction in this area at least since mid-Quaternary times, and an intimate relationship between fluid migration and slope stability. We show that two landslides, i.e. pre-Ana Slide and Ana Slide, occurred at almost the same location above an erosional channel in the Messinian unconformity. There is seismic evidence that fluids including gas are migrating upwards through this erosional surface and that they charge sedimentary layers at the base of the Ana Slide possibly reducing its strength and predisposing it to failure. Our data show in unprecedented detail the ways in which the presence of gas influences slope stability. The findings illustrate the importance of including high-resolution 3D seismic data in slope stability and tsunami risk assessments to identify shallow gas distribution as one of the main controls on slope stability in gas prone areas.