Description: The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side.

Description: The Doldrums transform system offsets the Equatorial Mid Atlantic Ridge by ~630 km at 7–8° N. This transform system consists of four intra-transform spreading centers (ITRs) bounded by five transform faults. The northernmost ITR is linked to the MAR axis by a ~ 180 km-long transform. Here, during two R/V A. N. Strakhov expeditions (S06 and S09), mantle peridotites were dredged along the transverse and median ridge of the transform, across the western flank of the ITR valley. Residual harzburgites were mainly sampled along the northern Doldrums transform valley, whereas plagioclase-bearing peridotites showing evidence for melt-rock interaction characterize the ITR domain. Petrological and geochemical observations reinforced by geochemical modelling are used to define the behaviour of trace elements during melt extraction and melt-rock reaction in our rocks. Results suggest that residual peridotites derive from mantle rocks that have undergone a degree of partial melting up to 12%, with melting likely starting at the transition of garnet-spinel stability fields, whereas peridotites which suffered melt-rock reactions have been divided into two types: (i) pl-impregnated peridotites, formed by migration of melts at high porosity and high melt-rock ratio; and (ii) refertilized peridotites, generated at reduced porosity, when small fractions of the same percolating melt crystallized clinopyroxene and minor plagioclase. We suggest that the refertilizing agent was a melt highly depleted in incompatible trace elements, in turn produced by an ultra-depleted mantle source. This mantle experienced previous degrees of melt extraction at the ridge axis, before being transposed laterally along the transform where it melted a second time during the opening of the intra-transform spreading segment.

Description: Highlights • New geophysical data and samples redefine submarine volcanism in Sicilian Channel. • Three dominant bands of volcanism are distinguished. • Ancient, eroded structures aligned at 120° are tied to faulted banks in the north. • Younger band of similarly aligned volcanism in the south is linked to grabens. • Youngest structures comprise small, dispersed volcanoes with distinct orientation. Abstract The origin and role of volcanism in continental rifts remains poorly understood in comparison to other volcano-tectonic settings. The Sicilian Channel (central Mediterranean Sea) is largely floored by continental crust and represents an area affected by pronounced crustal extension and strike-slip tectonism. It hosts a variety of volcanic landforms closely associated with faults, which can be used to better understand the nature and distribution of rift-related volcanism. A paucity of appropriate seafloor data in the Sicilian Channel has led to uncertainties regarding the location, volume, sources and timing of submarine volcanism. To improve on this situation, we use newly acquired geophysical data (multibeam echosounder and magnetic data, sub-bottom profiles) and dredged seafloor samples to: (i) re-assess the evidence for submarine volcanism in the Sicilian Channel and define its spatial pattern, (ii) infer the relative age and style of magmatism, and (iii) relate this to the dominant tectonic structures in the region. Quaternary rift-related volcanism has been focused at Pantelleria and Linosa, at the northwest boundaries of their respective NW-SE trending grabens. Subsidiary and older volcanic sites potentially occur at the Linosa III and Pantelleria SE seamounts, collectively representing the only sites of recent volcanism that can be directly related to the main rift process. These long-lived polygenetic volcanic landforms have been shaped by magmatism that is directly correlated with extensional faulting and buried igneous bodies. Older volcanic landforms, sharing a similar scale and alignment, occur to the north at Nameless Bank and Adventure Bank. These deeply eroded volcanoes have likely been inactive since the Pliocene and are probably related to earlier stages of crustal thinning and underlying feeder structures in the northern region of the Sicilian Channel. Along a similar alignment, Pinne Bank, SE Pinne Bank and Cimotoe in the northern Sicilian Channel lack a surface volcanic signature but are associated with intrusive bodies or deeply buried volcanic rock masses. Terrible Bank, in the same region, also shows evidence of ancient, polygenetic magmatism, but was subject to significant erosion and lacks a prominent alignment. The much younger volcanism at Graham Volcanic Field and along the northern Capo-Granitola-Sciacca Fault Zone differs markedly from that observed in the other study areas. Here, the low-volume and scattered volcanic activity is driven by shallow-water mafic magma eruptions, which gave rise to small individual cones. These sites are associated with large fault structures away from the main rift axis and may have a distinct magmatic origin. Dispersed active fluid venting occurs across both ancient and young volcanic sites in the region and is directly associated with shallow magmatic bodies within tectonically-controlled basins. Our study provides the foundation for an updated tectonic and magmatic framework for the Sicilian Channel, and for future detailed chronological and geochemical assessment of the sources and evolution of magmatic processes in the region.

Description: New multichannel seismic reflection profiles were acquired to unravel the structure of a portion of the eastern margin of the Tyrrhenian basin. This extensional feature is part of an Oligocene to Present back-arc basin in the hangingwall of the west directed Apennines subduction system. The basin provides excellent conditions to investigate the early stage processes leading to the development of rifted passive margins and to the emplacement of oceanic crust in an oblique setting. The interpreted post-stack-migrated seismic profiles highlight the geometry and kinematics of the Pontine escarpment that connects the Latium-Campania continental margin to the Vavilov basin. The latter is the main feature of the area, related to the early Pliocene extension of the Tyrrhenian Sea. Several morphological variations are pointed out along strike, mirroring different structural settings of the margin itself: a steeper margin to the north corresponds to high-angle possibly transtensional faults, whereas a smooth slope in the southern portion corresponds to several more distributed listric faults. This work contributes to the understanding of the interplay between extensional and transtensional tectonics along the margins of an oblique back-arc basin.

Description: Published

Description: 78–107

Description: 3A. Geofisica marina

Description: 2TR. Ricostruzione e modellazione della struttura crostale

Description: JCR Journal

Description: The Equatorial portion of the Mid Atlantic Ridge is displaced by a series of large offset oceanic transforms, also called “megatransforms”. These transform domains are characterized by a wide zone of deformation that may include different conjugated fault systems and intra-transform spreading centers (ITRs). Among these megatransforms, the Doldrums system (7-8ºN) is arguably the less studied, although it may be considered the most magmatically active. New geophysical data and rock samples were recently collected during the 45th expedition of the R/V Akademik Nikolaj Strakhov. Preliminary cruise results allow to reconstruct the large-scale structure and the tectonic evolution of this poorly-known feature of the Equatorial Atlantic. Swath bathymetry data, coupled with extensive dredging, were collected along the entire megatransform domain, covering an area of approximately 29,000 km2. The new data clearly indicate that the Doldrums is an extremely complex transform system that includes 4 active ITRs bounded by 5 fracture zones. Although the axial depth decreases toward the central part of the system, recent volcanism is significantly more abundant in the central ITRs when compared to that of the peripheral ITRs. Our preliminary interpretation is that a region of intense mantle melting is located in the central part of the Doldrums system as consequence of either a general transtensive regime or the occurrence of a more fertile mantle domain. Large regions of basement exposure characterize the transform valleys and the ridge-transform intersections. We speculate that different mechanisms may be responsible for the exposure of basement rocks. These include the uplift of slivers of oceanic lithosphere by tectonic tilting (median and transverse ridges formation), the denudation of deformed gabbro and peridotite by detachment faulting at inner corner highs, and the exposure of deep-seated rocks at the footwall of high-angle normal faults at the intersection of mid-ocean ridges with transform valleys.

Description: Published

Description: 25-41

Description: 3A. Geofisica marina e osservazioni multiparametriche a fondo mare

Description: JCR Journal

Description: The geological and geophysical data acquired during cruise 45 of R/V Akademik Nikolaj Strakhov regarding the structure of the Doldrums megatransform system in the Central Atlantic are presented. Taking into account the data of the previous expeditions, the structure of this region is examined in detail. The bathymetric data confirm the complex morphology, consisting of five dextral transform faults, separated by four active intra-transform rift segments and indicates the variability of tectonic conditions in this region. The dredged rocks are represented by the entire spectrum from the mantle to the upper crustal varieties and, together with the detailed topographic data, make it possible to identify the origin of the key structures in the Doldrums megatransform system.

Description: Published

Description: 131–134

Description: 3A. Geofisica marina e osservazioni multiparametriche a fondo mare

Description: 2TR. Ricostruzione e modellazione della struttura crostale

Description: JCR Journal

Description: Herein we provide information on the integrated geological, geophysical, sedimentological, paleoceanographic, hydrophysical and biological investigations in the Central Atlantic during the cruise 45 of the R/V “Akademik Nikolaj Strakhov” in October-November 2019. The preliminary scientific results are discussed.

Description: Published

Description: 424–426

Description: 3A. Geofisica marina e osservazioni multiparametriche a fondo mare

Description: JCR Journal

Description: New high-resolution geophysical data collected along the eastern margin of the Tyrrhenian back-arc basin, in the Pontine Islands area, reveal a ∼NW-SE elongated morphological high, the Ventotene Volcanic Ridge (VR), located on the northern edge of the Ventotene Basin. High-resolution multibeam bathymetry, combined with magnetic data, multi- and single-channel seismic profiles, and ROV dives, suggest that VR results from aggregation of a series of volcanic edifices. The summit of these volcanoes is flat and occurs at about 170 m water depth. Given their depths, we propose that flat morphologies were probably caused by surf erosion during Quaternary glacial sea level lowstands. Seismic stratigraphy together with magnetic data suggest that the volcanic activity in this area is older than 190–130 ka age and may be coeval with that of Ventotene Island (Middle Pleistocene). The submarine volcanoes, located 25 km north of Ventotene, are part of a ∼E-W regional volcanic alignment and extend the Pontine volcanism landward toward the Gaeta bay. Integration of structural data from multichannel seismic profiles in this sector of the eastern Tyrrhenian margin indicates that several normal and/or transtensional faults, striking WNW-ESE, NNW-SSE, and NE-SW, offset the basement and form alternating structural highs and depressions filled by thick, mostly undeformed, sedimentary units. Arc-related magmatism is widespread in the study area, where the VR is placed at the hangingwall of the west-directed Apennines subduction zone, which is undergoing tensional and transtensional tectonics. Bathymetric and topographic evidence shows that VR lies in between a major NE-SW trending escarpment east of Ponza and a NE-SW trending graben southwest of the Roccamonfina volcano, a NE-SW transfer zone that accommodate the extension along this segmented portion of the margin. This suggests that the interaction between NE-SW and NW-SE trending fault systems acts as a structural control on location of eruptive centers, given that main volcanic edifices develop along the NW-SE direction, compatible with the extensional setting of the Tyrrhenian basin.

Description: Published

Description: 86

Description: 3A. Geofisica marina

Description: JCR Journal

Description: Climate change investigation, protection of marine ecosystems and mitigation of natural risks are the main research objectives of the Levante Canyon Mooring (LCM), a deep submarine multidisciplinary observatory, installed in September 2019 in the Eastern Ligurian Sea (Lat 44°05.443'N, Long 009°29.900'E at 608 m depth), inside the Pelagos Sanctuary. The observatory consists of a stand-alone station, with an instrumented mooring line ending with a submerged buoy. It operates in delayed-mode and is equipped with sensors that measure physical and biogeochemical parameters continuously and it is expected to provide data in the long-term. Temperature and salinity monitoring is carried out at three depth levels (about 80, 335 and 580 m depth), while turbidity is recorded at 580 m depth. LCM is also equipped with a sediment trap and two acoustic current profilers, able to measure direction and speed of currents in nearly the entire water column.Data will be used to measure flux of sediments, nutrients and organic matter and to better understand the hydrodynamic and physical conditions of the Levante Canyon, which hosts valuable and vulnerable ecosystems, such as the deep-living cold-water corals, identified by IIM and ENEA in 2014, near the LCM mooring site. The LCM site is also located in an area where surface currents are monitored in near-real time by the CNR's High Frequency Radar network, allowing data integration from multiplatform observations.The project, co-financed by the Liguria Region, is coordinated by the DLTM in strict collaboration, in terms of human resources, infrastructures and instruments with the associated public research bodies (CNR, ENEA, INGV) and with the IIM. The project also includes the next deployment of a cabled station in the Gulf of La Spezia (10 m depth, less than 100 m far from the coast) that will monitor the gravimetric field, temperature and marine current. The main objective of the coastal station is to provide a test site for new instruments and sensors.

Description: Published

Description: Online

Description: 3A. Geofisica marina e osservazioni multiparametriche a fondo mare

Description: The overall objective of this proposal is to build an advanced and original prototype specifically devoted to seafloor and water-column monitoring as starting Italian contribution to the further development of the EMSO Ligurian Sea node. In detail the aim of the observatory is to ensure realtime continuous acquisition of geophysical, oceanographic and biological data by a cable system from a marine depth of about 500 m to the shore station.

Description: Published

Description: Genova, Italy

Description: 3A. Ambiente Marino

Description: restricted