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The Maltese Islands (central Mediterranean Sea) are intersected by two normal fault systems associated with continental rifting to the south. Because of a lack of evidence for offshore displacement and insignificant historical seismicity, the systems have been considered to be inactive. Here we integrate aerial and marine geological, geophysical and geochemical data to demonstrate that: (i) the majority of faults offshore the Maltese Islands underwent extensional to transtensional deformation during the last 20 ka, (ii) active degassing of CH4 and CO2 occurs via these faults. The gases migrate through Miocene carbonate bedrock and the overlying Plio-Pleistocene sedimentary layers to generate pockmarks at the muddy seafloor and rise through the water column into the atmosphere. We infer that the offshore faults systems are permeable and that they were active recently and simultaneously. The latter can be explained by a transtensional system involving two right-stepping, right-lateral NW-SE trending faults, either binding a pull-apart basin between the islands of Malta and Gozo or associated with minor connecting antitethic structures. Such a configuration may be responsible for the generation or reactivation of faults onshore and offshore the Maltese Islands, and fits into the modern divergent strain-stress regime inferred from geodetic data., peer-reviewed

18 pages, 13 figures, 1 table, We present here for the first time a morpho-structural study of the submarine sector of the Ustica volcanic edifice, located in the south-western Tyrrhenian Sea, considered as an inactive volcanic system, middle Pleistocene in age. The main aim of this research study is to unravel the submarine dynamics along the slope sectors of the Ustica volcano, in order to provide new insights on one of the most tectonically active regions of the Central Mediterranean during the Quaternary. We analysed and interpreted an integrated seismo-acoustic data set consisting of multibeam swath-bathymetry, sub bottom profiles, single-channel seismic reflection records, all of them acquired during the last two decades. The seismostratigraphic analysis indicates that the Ustica volcano is composed by a sequence of lava flows and pyroclastic products, whose geometry can be interpreted as the consequence of combined upward growing and northward shifting of the volcanic centers. The mapped geomorphological elements distributed along the submerged slopes were classified based on their specific morphogenetic process. The achieved results reveal that volcanic, tectonic, oceanographic and gravity processes interacted in shaping the complex current physiography of the volcanic edifice, which is characterized by extremely uneven submarine flanks. The northern region is characterized by the widespread occurrence of well-preserved cones, probably linked to the last submarine volcanic activity of the area. Along the eastern sector, elongate gullies and linear furrows locally incise the shelf break and develop downward producing slope failures. Furrows and gullies represent the main conduits for flushing sediments through various types of flows and mass wasting, from the shallow sectors to the bathyal plain. Along the southern and eastern region slope failures processes carve almost totally of the shelf edge and mainly propagate through retrograding collapses. Further on, the southern region is mainly shaped by E-W and N-S trending fault escarpments that may have triggered the largest slope failures of the area. The main results of this study contribute to improve the understanding of the geological processes and geodynamic activity between the Northern Sicily Continental Margin and the Tyrrhenian Basin and represent a baseline for assessing the geo-hazard potential on the Ustica Island, We acknowledge the CARG Project (Geological Maps of Italy) funded by the ISPRA-Italian Geological Survey and the Italian National Research Projects MaGIC (Marine Geological Hazard along the Italian Coast) funded by the Italian Civil Protection Department.-- With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

We present the results of an integrated geomorphological and seismo-stratigraphic study based on high resolution marine data acquired in the north-western Sicilian continental margin. We document for the first time five contourite drifts (marked as EM1a, EM2b, EM2, EM3a, and EM3b), located in the continental slope at depths between ca. 400 and 1500 m. EM1a,b have been interpreted as elongated mounded drifts. EM1a,b are ca. 3 km long, 1.3 km wide, and have a maximum thickness of 36 m in their center that thins northwards, while EM1b is smaller with a thickness up to 24 m. They are internally characterized by mounded seismic packages dominated by continuous and parallel reflectors. EM2 is located in the upper slope at a depth of ca. 1470 m, and it is ca. 9.3 km long, more than 3.9 km wide, and has a maximum thickness of ca. 65 m. It consists of an internal aggradational stacking pattern with elongated mounded packages of continuous, moderate to high amplitude seismic reflectors. EM2 is internally composed by a mix of contourite deposits (Holocene) interbedded with turbiditic and/or mass flow deposits. EM1a,b and EM2 are deposited at the top of an erosional truncation aged at 11.5 ka, so they mostly formed during the Holocene. EM3a,b are ca. 16 km long, more than 6.7 km wide, and have a thickness up to 350 m. Both EM2 and EM3a,b have been interpreted as sheeted drift due to their morphology and seismic features. The spatial distribution of the contourite drifts suggests that the drifts are likely generated by the interaction of the LIW, and deep Tyrrhenian water (TDW) on the seafloor, playing an important role in the shaping this continental margin since the late Pleistocene-Holocene. The results may help to understand the deep oceanic processes affecting the north-western Sicilian continental margin.

A high resolution seismic stratigraphic study of the western edge of the Malta Plateau (central Mediterranean Sea) was conducted to reconstruct the depositional mechanisms of the shelf-slope system since the end of the Messinian salinity crisis (MSC; 5.3 Ma). The accurate interpretation of a large grid of variable-resolution seismic reflection profiles (multichannel and Sub Bottom) allows us to identify and map a Plio-Quaternary sedimentary sequence overlying the Messinian evaporites. The stratal pattern of this sequence is the result of a clinoform prograding system that constitutes the internal structure of a sedimentary shelf developed in a ramp about 2° slope with bathymetries that do not exceed 200 m. This type of shelf is a physiographic feature where the shelf edge separates littoral from bathyal realms, differing from the definition of continental shelf that implies the presence of a continent-ocean margin. The evolution of the western edge of Malta Plateau differs from adjacent sectors. Unlike to the nearby Gela Basin, where the Plio-Quaternary sedimentary sequences were affected by the thrusting of the Sicilian-Maghrebian chain until Middle Pleistocene, in the Malta Plateau the post-Messinian sedimentation was mainly controlled by subsidence and sea level fluctuations. In particular, the Malta Plateau represents a back bulge depozone where moderate fluvial sediment supply together with continuous subsidence favoured the progradation of the upper Pliocene-Pleistocene shelf-slope system at bathymetries not exceeding 200 m.

We investigate the tectonically active Northern Sicily Continental margin focusing on the neotectonics affecting the Offshore of Termini (Southern Tyrrhenian Sea) by using high-resolution seismic and multibeam data. The sedimentary succession along the North Sicilian Continental Margin (NSCM) represents the marine prolongation of those outcropping along the Northern Sicily coastal belt. The NSCM has been originated as a consequence of a complex interaction of compressional events, crustal thinning, and strike-slip faulting. E–W, NW–SE, and NE–SW trending, both extensional and compressional faults, with a local strike-slip component, exerted control on the morphology of the present-day shelf and coastal areas during the Pleistocene. During the Quaternary, the tectonic as well as depositional events have strongly shaped the margin forming the actual complex geomorphic setting of the margin. We present the main results of a high resolution survey that allow to identify several features (e.g. Mass Transport Deposits and pockmarks) linked to gravitational mass movement and fluids escape processes strongly controlled by the tectonics affecting the NSCM. All over the study area, we mapped inside the Late Quaternary depositional sequence repeated and variously distributed MTDs, characterised by transparent/chaotic seismic facies, interbedded to hemipelagic deposits, with seismic facies showing subparallel seismic reflectors of the transgressive and high stand systems tracts. We infer that this MTDs have been seismically induced by earthquakes. We estimate the recurrence times of earthquakes, by using an elaborate age-model that considers a constant sedimentation rate for the last 11.5 My, between 680 and 2200 years.

The Maltese Islands, located in the central Mediterranean Sea, are intersected by two normal fault systems associated with continental rifting to the south. Due to a lack of evidence for offshore displacement and insignificant historical seismicity, the systems are thought to be inactive and the rift-related deformation is believed to have ceased. In this study we integrate aerial, marine and onshore geological, geophysical and geochemical data from the Maltese Islands to demonstrate that the majority of faults offshore the archipelago underwent extensional to transtensional deformation during the last 20 ka. We also document an active fluid flow system responsible for degassing of CH4 and CO2. The gases migrate through carbonate bedrock and overlying sedimentary layers via focused pathways, such as faults and pipe structures, and possibly via diffuse pathways, such as fractures. Where the gases seep offshore, they form pockmarks and rise through the water column into the atmosphere. Gas migration and seepage implies that the onshore and offshore faults systems are permeable and that they were active recently and simultaneously. The latter can be explained by a transtensional system involving two right-stepping, right-lateral NW-SE trending faults, either binding a pull-apart basin between the islands of Malta and Gozo or associated with minor connecting antitethic structures. Such a configuration may be responsible for the generation or reactivation of faults onshore and offshore the Maltese Islands, and fits into the modern divergent strain-stress regime inferred from geodetic data.

Graham Bank is a dominant physiographic element of the NW Sicily Channel (central Mediterranean Sea), affected in the last 100 years by numerous well-documented volcanic eruptions. We present the first results of a geomorphological study where the Graham Bank region in the depth interval 7–350 m was mapped for the first time with multi-beam echosounder and high-resolution seismic and multi-channel seismic reflection profiles. We describe in high resolution the detailed geomorphological features of Graham Bank, and how the superficial expression of different process and dynamics occurring in the sub-seafloor evidence volcanic and tectonic controls on seafloor morphology across a relatively small area. The north-eastern part of the study area is dominated by seamounts with heights ranging from 97 to 152 m and auxiliary small cones, reaching heights of 2–10 m, on the whole forming a hummocky surface. In this region, fluid seepages are an important expression of the volcanic processes affecting the study area. The western region comprises a flat seafloor covered by Upper Pleistocene-Holocene outer shelf sedimentary deposits; here aligned mounds and pockmarks are predominantly oriented NW–SE or NNW-SSE, running parallel to the main structural trend of the Sicily Channel. The pockmarks have sub-circular planform shapes and U-shaped cross-section and different depths and mean axis lengths. Numerous Mass Transport Deposits (MTDs) are distributed across the study area. Graham Bank is 45 km from the coast of Sicily and is intersected by submarine cables. Consequently, the mapped volcanic seamounts, pockmarks and MTDs could pose a significant economic risk to the submarine cables.

Active fluid seepage (AFS) at the seafloor is a global phenomenon associated with seafloor morphologies in different geodynamic contexts. Advanced geophysical techniques have allowed geoscientists to characterise pockmarks, mounds and flares associated with AFS. We present a range of new marine geological data acquired in the southern region of the central Mediterranean Sea (northern Sicily continental margin, northwestern Sicily Channel and offshore of the Maltese Islands), which allow us to identify AFSs. AFSs are spatially distributed as clusters, aligned or isolated at different depths, ranging from few decametres offshore of the Maltese Islands; up to 400 m offshore of northern Sicily and in the northwestern Sicily Channel. Mounds have heights ranging from 2 to 15 m and form hummocky surfaces. Seafloor samples were collected at the top of the mounds and were analysed using a SEM with an EDX. Geochemical features reveal that seafloor samples are slightly enriched in O, S and Ba and seem to indicate the existence of an external source of fluids and the occurrence of sediment-fluids interaction processes. Pockmarks with sub-circular planform shapes and U/V-shaped cross-sections are found in sizes ranging from 5 to 530 m. Gas flares occur on both the continental shelf as well as the upper slope.

Carbonate escarpments are submarine limestone and dolomite cliffs that have been documented in numerous sites around the world. Their geomorphic evolution is poorly understood due to difficulties in assessing escarpment outcrops and the limited resolution achieved by geophysical techniques across their steep topographies. The geomorphic evolution of carbonate escarpments in the Mediterranean Sea has been influenced by the Messinian salinity crisis (MSC). During the MSC (5.97–5.33 Ma), the Mediterranean Sea became a saline basin due to a temporary restriction of the Atlantic-Mediterranean seaway, resulting in the deposition of more than one million cubic kilometres of salt. The extent and relative chronology of the evaporative drawdown phases associated to the MSC remain poorly constrained. In this paper we combine geophysical and sedimentological data from the central Mediterranean Sea to reconstruct the geomorphic evolution of the Malta Escarpment and infer the extent and timing of evaporative drawdown in the eastern Mediterranean Sea during the MSC. We propose that, during a MSC base-level fall, fluvial erosion formed a dense network of canyons across the Malta Escarpment whilst coastal erosion developed extensive palaeoshorelines and shore platforms. The drivers of geomorphic evolution of the Malta Escarpment after the MSC include: (i) canyon erosion by submarine gravity flows, with the most recent activity taking place, This research was undertaken with funding from Marie Curie Career Integration Grant PCIG13-GA-2013-618149 (SCARP), ERC Starting Grants n°258482 (CODEMAP) and n°677898 (MARCAN), and collaborative project n°228344 (EUROFLEETS), all within the 7th European Community Framework Programme and the Horizon 2020 Programme. Financial support was also provided by the Fulbright Visiting Scholar Program, Royal Society of New Zealand (through the International Mobility Fund), New Zealand Crown Research Institute SSIF funding to NIWA, the Griffith Geoscience Awards (Department of Communications, Energy and Natural Resources under the National Geoscience Programme 2007–2013 of Ireland), and the David and Lucile Packard Foundation. MAG acknowledges INSU for cruise-related funding and the European Union FP7 project ASTARTE for post-cruise financial support. The article is based upon work from COST Action CA15103 “Uncovering the Mediterranean salt giant” (MEDSALT) supported by COST (European Cooperation in Science and Technology).

A. Micallef et. al., The Messinian salinity crisis (MSC)-the most abrupt, global-scale environmental change since the end of the Cretaceous-is widely associated with partial desiccation of the Mediterranean Sea. A major open question is the way normal marine conditions were abruptly restored at the end of the MSC. Here we use geological and geophysical data to identify an extensive, buried and chaotic sedimentary body deposited in the western Ionian Basin after the massive Messinian salts and before the Plio-Quaternary open-marine sedimentary sequence. We show that this body is consistent with the passage of a megaflood from the western to the eastern Mediterranean Sea via a south-eastern Sicilian gateway. Our findings provide evidence for a large amplitude drawdown in the Ionian Basin during the MSC, support the scenario of a Mediterranean-wide catastrophic flood at the end of the MSC, and suggest that the identified sedimentary body is the largest known megaflood deposit on Earth. © 2018 The Author(s)., This work was supported by Marie Curie Career Integration Grant PCIG13-GA-2013–618149 (SCARP) within the 7th European Community Framework Programme, and the European Research Council under the European Union’s Horizon 2020 Programme (grant agreement n° 677898 (MARCAN)).