Three-dimensional density model of the Earth's crust and the upper mantle for the area of Poland

Abstract

A three-dimensional (3D) density model of the Earth's crust and the upper mantle beneath Poland, where Europe's three great geotectonic provinces adjoin, was constructed on the basis of geological, seismic and gravity data. The model includes: (1) a medium with horizontally variable density representing the Permo-Mesozoic-Cenozoic sedimentary cover, (2) two density interfaces of which the upper one corresponds to the top of the consolidated basement, and the lower one to the bottom of the crust determined from DSS (deep seismic soundings) data, and (3) the upper mantle with variable densities. The gravitational influence of the upper mantle (whose density model was constructed using the 3D gravity modelling) compensates for a considerable portion of the Earth's crust gravity effect that is strongly affected by the Moho topography. The results of computation show that in the presented crustal density model, including the DSS data, a considerable change in the crustal thickness is accompanied by horizontal changes of the density in the upper mantle. Thus, it can be inferred that a contact zone between the Precambrian East European Craton (EEC) and Phanerozoic fold belts of the Central and Western Europe extends down to the lower lithosphere. The analysis of the map of the gravity effect of the 3D density model of the Earth's crust and the upper mantle, the map of reduced anomalies (differences between the Bouguer gravity anomalies and computed 3D gravity effect), and the maps of transformed anomalies made it possible to indicate the sources of regional gravity anomalies in various parts of Poland and to make preliminary gravity interpretations in order to identify the complex structure of Paleozoic formations in the East European Craton's foreland.