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S U M M A R YA map of the observed gravity field of Europe has been constructed by averaging anomalies on a 1" X 1" grid in a combined reduction of Bouguer anomalies on land and free-air anomalies offshore. On the basis of the observed gravity field and recent seismic data on crustal structure, a 3-D density model for the lithosphere of Europe has been calculated. The model is represented by two complementary parts, each obtained by its own specific method. For the south of Eastern Europe, the 3-D density model of the Earth's crust comprising the sedimentary cover and three layers within the crystalline crust (upper, intermediate and lower crust) was obtained by the following procedure: (1) the velocity model was transformed into a density distribution using the velocity-density relation; (2) the gravity field of this density distribution was calculated by solving the 3-D direct gravity problem; (3) the residual gravity field was obtained by subtracting the total gravity effect of the model and the regional component from the oberved gravity field: (4) the isostatic equilibrium of the model was evaluated; (5) in accordance with the residual anomalies and isostasy estimates, some changes (mainly in density distribution within the sedimentary cover) were entered into the initial density model and the final version of the density model was obtained for the consolidated crust as well as for areas with density inhomogeneities within the upper mantle.The correlation between Moho traveltimes and crustal gravity influence obtained from the results of 3-D modelling for the south of Eastern Europe, supplemented by 2-D modelling data available over Western Europe, makes it possible to estimate (without solving the direct gravity problem) the crustal gravity field for the whole European continent. Residual anomalies due to subcrustal density inhomogeneities have been interpreted in the light of seismic tomography and heat-flow distribution.For both parts of the model geological and geodynamical interpretations of the results have been made. In particular, differences in the deep structure of the two major geoblocks of the continent-the West and East European Platforms-have been confirmed. Regions of relatively light upper mantle have been outlined beneath the east and north-west of the East European Platform, while a heavier upper mantle has been distinguished below the Alps, the Caucasus, and the Calabrian Arc, as well as under the South Caspian Depression.

Residual gravity anomalies characterizing the density heterogeneities in the upper mantle of the Alpine belt of Western Europe are determined. Residual anomalies were calculated on a 1" x 1" grid by subtracting the gravity effect of the density model for the Earth's crust from the observed gravity field. Our 3-D density model consists of two regional layers of varying thicknesses with a lateral variation in average density: the sedimentary cover and the crystalline crust. Offshore, the model is supplemented by a sea-water layer. This 3-D density model is based on a generalized velocity model represented by structure maps of the main seismic horizons (the 'seismic' basement and the Moho boundary) and a map of the average P-wave velocity in the consolidated crust. The density distribution within the model layers was obtained using the correlation functions between P-wave velocity and density. For sediments, sediment consolidation with depth was taken into account. The gravity effect of the model, approximated by parallelepipeds 1" x 1" in planar size, was calculated by a program designed for solving 3-D gravity problems. The program takes into account the spherical configuration of the Earth. This method also permits the estimation of the isostatic state of the crust. A mantle origin of residual gravity anomalies is confirmed by their close correlation with upper-mantle velocity heterogeneities, established by both seismic-tomography and thermal-regime data. The residual gravity field is inverted into the distribution of anomalous density within the uppermost mantle layer (between the Moho and a bottom level at 200 km depth). The most important anomalies are the high-density domains caused by the thick lithosphere of the Adriatic plate and by the lithosphere 'roots' beneath the Alps and the Calabrian Arc. Negative density anomalies over the Pannonian Basin and the Western Mediterranean basins reach -0.04 to -0.05 x lo3 kg m-3 due to thermal expansion of the asthenosphere.

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