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Widespread volcanism has been known in the Sicilian Channel for a long time, even if some submarine volcanoes have only recently been discovered. Most of this volcanism formed along the NNE-trending transfer zone known as the Capo Granitola–Sciacca Fault Zone, while others, such as the islands of Pantelleria and Linosa, are associated with the continental rift zone that has developed since the early Pliocene in the central part of the Sicilian Channel through the formation of three deep tectonic troughs (Pantelleria, Linosa and Malta). However, the origin of a group of five volcanoes (here called "Tetide volcanic cluster") that form a NW-SE alignment on the eastern edge of the Adventure Plateau is not yet known. In this work, we hypothesize that this volcanic alignment may represent the remnants of a failed rift attempt that was unable to generate another tectonic trough in the Sicilian Channel. Based on seismic sections and gravimetric data, three phases in the formation of this volcanic alignment can be identified: (i) a major magmatic intrusion in the early Pliocene associated with a NW-SE normal fault that formed during the opening of the Pantelleria graben, leading to the uplift and deformation of the host sedimentary rocks; (ii) a late Pliocene-Quaternary tectono-magmatic quiescent phase; and (iii) a renewed magma intrusion through fissures or cracks that led to the formation of the volcanoes in the late Quaternary. This process was not able to cause significant extension and only limited volcanism, which is why the "Tetide volcanic cluster" is interpreted as the morphological expression of a failed rift. [ABSTRACT FROM AUTHOR]

This paper presents the results of the interpretation of a set of high‐resolution seismic lines integrated with multibeam echosounder data acquired in a coastal area in the Northern Adriatic Sea. The aim of the study was to reconstruct the stratigraphic evolution of a late Quaternary sedimentary succession offshore the town of Bibione, North‐Eastern Italy, by recognising the key unconformities, identifying the main depositional units, dating them and reconstructing the depositional environments in relation to relative sea‐level variations. Specifically, four sedimentary units, separated by erosional unconformities associated with the development of deep channels, were identified and dated based on literature information. By interpreting the seismic data, sedimentary dynamics were reconstructed and palaeoenvironments identified. The lower unit corresponds to a paludal environment, showing abundant gas seeps and accumulations (bright spots); the two intermediate units correspond to fluvial deposits, filling the deep incisions that characterise the bounding surfaces. Finally, the shallowest unit, bounded by a wave‐ravinement surface incised by tidal currents, corresponds to the Holocenic progradation of the coastal wedge. In addition, several vertical gas chimneys were identified, ranging in width from a few metres to 20–30 m. These were present in all units, often reaching the sea floor. Finally, elongated mounds, about 300 m wide, at the sea floor were recognised. The bathymetric and seismic characteristics of these elongated bodies and their relationship to adjacent sedimentary bodies suggest that they are probably methane‐derived carbonate formations known as 'Trezze' or 'Tegnùe'. These names recall the fact that the trawls of the local fishermen were often hindered ('tegnù' in the Venetian language) or even cut off by these formations. [ABSTRACT FROM AUTHOR]

The ancient Greek colony of Selinunte, with its acropolis on a promontory on the south-western coast of Sicily, is flanked by two valleys where two modest rivers flow today: the Modione to the west and the Cottone to the east. Archaeological reconstructions, historical documents from various sources, and recent remote sensing surveys indicate two important bays corresponding to the ancient mouths of these two rivers, now completely covered by a thick layer of sediments. It is believed that the ports of the colony were located in these bays, although the remains of these ports are still sparse and contradictory. Here we present a multibeam bathymetric map of part of the marine area immediately off Selinunte and a series of high-resolution seismic profiles acquired parallel to the coastline. They show the geometries and stratigraphic context of the two buried river valleys offshore, from which information about the palaeoenvironmental setting and evolution of the landscape can be derived and which may be used in adequately guiding future archaeological excavation programs. [ABSTRACT FROM AUTHOR]

Acquiring seismic data with multichannel, multiple‐streamer and even multi‐componentsystems at sea provides excellent images of the Earth. However, the cost and complexity of operations prevent their use in busy areas such as ports or in sensitive environments such as lagoons. In the latter cases, mono‐channel Chirp or Boomer systems are the most viable instruments for marine surveys. The lack of multiple offsets prevents the use of standard tools for amplitude‐versus‐offset and velocity analysis, which are necessary for the lithological characterization of rocks, especially for the shallow sediments in offshore engineering. In this paper, we present a few recent techniques that exploit the traveltime and amplitude of multiple reflections to compensate for the offset limitation, including a new algorithm for the joint tomographic inversion of direct arrivals, primaries and multiples. We have developed a cost‐effective workflow for mono‐channel surveys based on a data‐driven, physically consistent philosophy that attempts to approximately extract lithological parameters, such as P velocity, anelastic absorption, acoustic impedance and even density. We applied the proposed workflow to a real field experiment and obtained a semi‐quantitative estimate for shallow sediments that can be used by offshore engineers. [ABSTRACT FROM AUTHOR]

The lithological characterization of the seafloor is key information for offshore engineering, especially when it comes to pier and platform design. Undetected shallow gas pockets may cause the collapse of heavy platforms for hydrocarbon production. Unconsolidated sediments are not ideal for the basement of wind farms for electric power production. Drilling and coring can be used for local sampling, but continuous profiles or even areal coverage are far more preferable. High-resolution seismic profiles are successfully used when ports are not too busy, but otherwise, single-channel systems must be used. We show in this paper that even these simpler systems can be used to estimate parameters such as the acoustic impedance of shallow sediments directly beneath the seafloor. We exploit the amplitude decay of the multiple reflections between the seafloor and the surface, which does not depend on the source energy. If the offset between source and receiver is not too small, we can estimate the shallow P velocity and, via acoustic impedance, also the rock density. [ABSTRACT FROM AUTHOR]

Lago Roca/Acigami is a "fjord‐type" lake located in the southernmost part of South America, in the proximity of the Beagle Channel. A high‐resolution seismic survey was carried out to analyse the seismic stratigraphy of the lake and to shed some light on the post‐Last Glacial Maximum history of the area. Six seismic units were recognised, and their nature and depositional context were interpreted using seismic stratigraphy and acoustic facies analysis. A buried large ridge was identified within the glacial unit (SU1), interpreted as a frontal moraine that indicates a stabilisation phase. After retreat of the glacier from the basin, the trough was flooded by meltwater and a lake developed (SU2). The seismic facies, from bottom to top, depict a transition from ice‐contact (SU2; SU3) to ice‐distal proglacial conditions (SU4). A thick draping unit (SU5) marks a marine transgressive event and the instauration of a fjord environment in the basin. The marine transgression was a rapid event preceded by a fall in the lake level that caused an erosional unconformity. During the fjord phase the sedimentation remained controlled by meltwater discharge. Sea level fall, and subsequent disconnection from the Beagle Channel was accompanied by a progradation of the glaciofluvial deltaic sediments and the occurrence of several mass‐wasting deposits (SU6). © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]