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Abstract: The plate boundary between the Scotia and Antarctic plates runs along the broadly E–W trending South Scotia Ridge. It is a mainly transcurrent margin that juxtaposes thinned continental and transitional crust elements with restricted oceanic basins and deep troughs. Seismic profiles and regional-scale seismological constraints are used to define the peculiarities of the crustal structures in and around the southern Scotia Sea, and focal solutions from recent earthquakes help to understand the present-day geodynamic setting. The northern edge of the western South Scotia Ridge is marked by a sub-vertical, left-lateral master fault. Locally, a narrow wedge of accreted sediments is present at the base of the slope. This segment represents the boundary between the Scotia plate and the independent South Shetland continental block. Along the northern margin of the South Orkney microcontinent, the largest fragment of the South Scotia Ridge, an accretionary prism is present at the base of the slope, which was possibly created by the eastward drift of the South Orkney microcontinent and the consequent subduction of the transitional crust present to the north. East of the South Orkney microcontinent, the physiography and structure of the plate boundary are less constrained. Here the tectonic regime exhibits mainly strike–slip behavior with some grade of extensional component, and the plate boundary is segmented by a series of NNW–SSE trending release zones which favored the fragmentation and dispersion of the crustal blocks. Seismic data have also identified, along the north-western edge of the South Scotia Ridge, an elevated region – the Ona Platform – which can be considered, along with the Terror Rise, as the conjugate margin of the Tierra del Fuego, before the Drake Passage opening. We propose here an evolutionary sketch for the plate boundary (from the Late Oligocene to the present) encompassing the segment from the Elephant Island platform to the Herdman Bank. [Copyright &y& Elsevier]

Widespread Late Miocene to Quaternary volcanic activity is know to have occurred in the Sicily Channel continuing up to historical time. New magnetic anomaly data acquired in the Pantelleria Graben, one of the three main tectonic depressions forming the WNW-trending Sicily Channel rift system, integrated with available profiles, are used to identify and map volcanic bodies in this sector of the northern African margin. Some of these manifestations, both outcropping at the sea-floor or buried beneath a variable thickness of Plio-Quaternary sedimentary cover, have been imaged by seismic reflection profiles. Three main positive magnetic anomalies have been found: to the S-E of the Pantelleria Island, the largest emerged caldera of the Sicily Channel, along the eastern margin of the Nameless Bank, and at the north-western termination of the Linosa Graben. Only the anomaly located off the south-eastern coast of the Pantelleria Island, associated with a large outcropping body gradually buried beneath a substantially undisturbed Upper Pliocene-Quaternary sediments, aligns with the trend of the tectonic depression. 2-D geophysical models produced along seismic transects perpendicularly crossing the Pantelleria Graben have allowed to derive its deep crustal structure, and detect the presence of buried magmatic bodies which generate the anomalies. Marginal faults seem to have played a major role in focussing magma emplacement in this sector of the Sicily Channel. The other anomalies represent off-axis volcanic episodes and generally do not show evident magmatic manifestations at the sea-floor. These magnetic maxima seem to follow a NNE-SSW-trending belt extending from Linosa Island to the Nameless Bank, where pre-existing crustal anisotropies may have conditioned magma emplacement both at deep and shallow crustal levels. In general, data analysis has shown that there is a structural control on magma emplacement, with the major magmatic features located in specific locations like boundary faults and transfer zones, in a manner similar to that found along several segments of the East African Rift system. [ABSTRACT FROM AUTHOR]

Abstract: We present new high-resolution swath bathymetric data and multichannel seismic profiles acquired in the Pantelleria graben, one of the three main tectonic depressions forming the Sicily Channel Rift Zone. This region experienced a Late Miocene–Early Pliocene continental extension with the development of NW-trending, fault-bounded troughs, later accompanied by widespread volcanic manifestations. Data support the interpretation that the Pantelleria graben evolution was dominated by two tectonic phases: A lithospheric-scale continental rifting (Early Pliocene), in which the whole graben was formed, and a successive phase (Late Pliocene–Pleistocene) characterized by a magma-assisted extensional mechanism. Ascending magmas within the graben floor seem to migrate from the S–E sector of the depression toward the N–W sector, which is almost entirely floored by igneous material, and where the volcanic edifice of the Pantelleria Island is emerged. The volcanic activity is presently concentrated north of the Pantelleria Island. The tectonic evolution of the Pantelleria graben, characterized by the chronological sequence of events: rifting-doming-volcanism, can be referred to as a ‘passive’ rifting model. Crustal stretching, and subsequent fault development and rifting within the Pelagian block, may have been controlled by slab-pull forces of the northward-subducting African slab. [Copyright &y& Elsevier]

Abstract: The Straits of Messina and its surroundings are considered as one of the most tectonically active area of the Mediterranean, but in spite of their hazard potential, modern geophysical data aimed at investigating their hidden structures are lacking. In order to bridge this gap, we carried out a marine multichannel seismic survey primarily aimed at: i) studying the regional fault pattern in the area of the Messina 1908 earthquake; and ii) checking the existence of a potentially seismogenic fault, the Taormina Fault, which many authors locate offshore, along the coast between Taormina and Messina. Our seismic profiles show a great structural complexity within the Messina Straits, with the best imaged faults occurring on the Calabrian side. In particular, a more than 30 km long NW-trending fault located at the SW tip of Calabria is cutting the sea floor. Moreover, our data did not image any extensional fault plane attributable to the Taormina Fault; rather, the whole slope has been tilted east-ward. The geodynamic implication is that extension in south-eastern Sicily, on the Ionian side of the Hyblean Plateau, and extension in southern Calabria and Messina Straits belong to two different tectonic systems and cannot be mechanically linked. [Copyright &y& Elsevier]