The lithospheric structure of the Western Carpathian–Pannonian Basin region based on the CELEBRATION 2000 seismic experiment and gravity modelling

Abstract

The lithospheric structure of the Western Carpathian–Pannonian Basin region was studied using 3-D modelling of the Bouguer gravity anomaly constrained by seismic models and other geophysical data. The thermal structure and density distribution in the shallow upper mantle were also estimated using a combination of petrological, geophysical, and mineral physics information (LitMod). This approach is necessary if the more complicated structure of the Pannonian Basin is to be better constrained. As a result, we have constructed the first 3-D gravity model of the region that combines various geophysical datasets and is consistent with petrological data. The model provides improved estimates of both the density distribution within the lithosphere and the depth to major density discontinuities. We present new maps of the thickness of major sedimentary basins and of the depth to the Moho and the lithosphere–asthenosphere boundary. In our best-fitting model, the Pannonian Basin is characterised by extremely thin crust and lithospheric mantle, both of which have low density. A low-density uppermost asthenospheric mantle layer is also included at depths of 60–100 km. The Western Carpathians have only a thin crustal root and moderate densities. In contrast, the European Platform and Eastern Alps are characterised by lithosphere that is considerably thicker and denser. This inference is also supported by stripped gravity anomalies from which sediment, Moho and asthenospheric gravity contributions have been removed. These residual anomalies are characteristically low in the Western Carpathian–Pannonian Basin region, which suggests that both the ALCAPA and Tisza–Dacia microplates are ‘exotic terranes’ that are markedly different to the European Platform.