A 3-D density model of Greece was developed by gravity modelling constrained by 2-D seismic profiles. Densities were defined from seismic velocities using the Nafe & Drake and Birch empirical functions for the sediments, crust and upper mantle. Sediments in the North Aegean are 6 km thick, and are deposited in transtensional basins developing by dextral strike slip motion of the North Anatolian Fault. The Cyclades, central Aegean Sea, are free of sediments. South of Crete, in the Libyan Sea, sediments are approximately 11 km thick. At the western Hellenides sediments of up to 8 km thickness have been accumulated in basins formed by crustal bending and southwestwards thrusting of the Hellenic napes. At a deeper crustal level variations of crustal type and thickness cause density variations explaining large part of the observed gravity field. The North Aegean domain is characterized by a 24-km-thick continental crust, including sediments, whereas the western Cyclades, in central Aegean area, have a slightly thickened crust of 26 km. Crustal thicknesses vary between 16 km in the deep Ionian and Cretan Seas to 40 km in the western Hellenides. In western Crete crust is 30–32 km thick, thinning eastwards to only 26 km. The deep Ionian basin, the Mediterranean Ridge, as well as most of the Libyan Sea are underlain by oceanic crust. In western Turkey the crust thickens from 30 km along the coast to 34 km to the interior. A third deeper level of density variations occurs in the upper mantle. Subduction of the oceanic lithosphere below the Aegean continental domain destabilizes the thermal field, uplifting the isotherms by convection and conduction below the Aegean Sea. Consequently, volume expansion of the upper mantle and lithological changes reduce its density and depress the gravity intensity. This low density–velocity upper mantle extends from the Sporades islands in the North Aegean to the Cretan Sea, occupying the space between the cold subducted Ionian oceanic lithosphere and the Aegean continental Moho. Upper mantle densities vary from 3.24 g cm^–3 in the Aegean area to 3.29 g cm^–3 below western Greece and the Ionian and Libyan Seas.

The backarc Black Sea (BS) basin was formed in the Late Cretaceous-Palaeocene at the hinterland of the Pontide magmatic arc due to subduction of the Neotethys ocean below the southern Eurasian continental margin. At present the BS consists of two large depressions—the West- and East-Black Sea basins (WBS and EBS) filled with thick (up to 12 km) Cretaceous and younger sediments and underlain by a crust of oceanic/suboceanic type. The sediments mask poorly investigated crystalline crust that is thought to comprise an accretional collage of microplates and terranes of different affinities. To investigate the lithospheric structure of the BS we performed a 3-D gravity analysis and local seismic tomography study. 3-D gravity backstripping analysis allowed us to separate the gravity signal from different parts of the crustal model and then, by subtracting the crustal effect from the observed field, to obtain gravity anomalies of presumed mantle origin only. The broad positive long wavelength component of this might be indicative of good isostatic equilibrium of the deep structure of the Black Sea, that is, that the negative gravity effect of sediments is almost totally compensated by the strong positive gravity impact of Moho shallowing. Velocity structure of the BS lithosphere has been studied by P-wave local seismic tomography. It uses the traveltimes of the earthquakes occurring inside the study region and recorded by permanent seismic stations around the BS. Initial data were corrected for the effect of the crust. The resulting model shows the BS lithosphere as being rather heterogeneous with two domains of increased velocity in its western and eastern parts. The gravity analysis and seismic tomography approaches were integrated by calculating the upper-mantle gravity effect of the tomography model and comparing this to the mantle gravity signature inferred from the gravity analysis itself. The integrated results suggest the presence of rheologically strong and cold continental lithosphere below the BS, similar to Precambrian lithosphere of the East European Platform.

Summary. The Antarctic Peninsula (AP) is a composite magmatic arc terrane formed at the Pacific margin of Gondwana. Through the late Mesozoic and Cenozoic subd

The GEORIFT 2013 (GR'13) WARR (wide-angle reflection and refraction) experiment was carried out in 2013 in the territory of Belarus and Ukraine with broad international co-operation. The aim of the work is to study basin architecture and deep structure of the Pripyat–Dnieper–Donets Basin (PDDB), which is the deepest and best studied Palaeozoic rift basin in Europe. The PDDB is located in the southern part of the East European Craton (EEC) and crosses Sarmatia—one of the three segments of the EEC. The PDDB was formed by Late Devonian rifting associated with domal basement uplift and magmatism. The GR’13 extends in NW–SE direction along the PDDB strike and crosses the Pripyat Trough (PT) and Dnieper Graben (DG) separated by the Bragin Uplift (BU) of the basement. The field acquisition along the GR'13 (of 670 km total length) involved 14 shots and recorders deployed every ∼2.2 km for several shot points. The good quality of the data, with first arrivals visible up to 670 km for several shot points, allowed for construction of a velocity model extending to 80 km depth using ray-tracing modelling. The thickness of the sediments (Vp < 6.0 km s⁻¹) varies from 1–4 km in the PT, to ∼5 km in the NW part of the DG, to 10–13 km in the SE part of the profile. Below the DG, at ∼330–530 km distance, we observed an upwarping of the lower crust (with Vp of ∼7.1 km s⁻¹) to ∼25 km depth that represents a rift pillow or mantle underplate. The Moho shallows southeastwards from ∼47 km in the PT to 40–38 km in the DG with mantle velocities of 8.35 and ∼8.25 km s⁻¹ in the PT and DG, respectively. A near-horizontal mantle discontinuity was found beneath BU (a transition zone from the PT to the DG) at the depth of 50–47 km. It dips to the depth of ∼60 km at distances of 360–405 km, similar to the intersecting EUROBRIDGE’97 profile. The crust and upper mantle structure on the GR'13 may reflect varying intensity of rifting in the PDDB from a passive stage in the PT to active rifting in the DG. The absence of Moho uplift and relatively thick crystalline crust under the PT is explained by its tectonic position as a closing unit of the PDDB, with a gradual attenuation of rifting from the southeast to the northwest. The most active stage of rifting is evidenced in the DG by a shallower Moho and by a presence of a rift pillow caused by mafic and ultramafic intrusions during the active phase. The junction of the PT and the DG (the BU) locates just at its intersection with the NS regional tectonic zone Odessa-Gomel. Most likely, the ‘blocking’ effect of this zone did not allow for further propagation of active rifting to the NW.

Summary. Large-scale 3D gravity modelling using data averaged on a 1° grid has been performed for the whole European continent and part of the Northern Atlanti