Lithospheric density model along the CEL09 profile and its geological implications

Abstract

We present a new 2D lithospheric density model along the seismic profile CEL09 crossing the Bohemian Massif, the Western Carpathians, and the Pannonian Basin. The resulting model consists of five principal layers: sediments, upper crust, lower crust, lower lithosphere, and asthenosphere. The thicknesses of the Neogene sedimentary basins vary from 0 to ~5.5 km while the Paleogene flysch sediments dip to a depth of ~6.5 km. The most complex upper part of the upper crust in the Bohemian Massif is represented mainly by low-density granitoid plutons (~2.60–2.68 g cm−3), metamorphic rocks (~2.69–2.74 g cm−3) and high-density basic and ultrabasic bodies (~2.78–2.79 g cm−3). In the Western Carpathians, this layer is formed by the crystalline Malé Karpaty Mts. (2.66–2.67 g cm−3), Trans-Danubian range (2.73–2.74 g cm−3), and the pre-Cainozoic basement of the sedimentary basins (2.67–2.74 g cm−3). The densities of the lower part of the upper crust range from 2.78 g cm−3 (in the Western Carpathian–Pannonian region) to 2.77–2.80 g cm−3 (in the Bohemian Massif). In the lower crust, four different sectors were modelled. In the Saxothuringian, they are divided into two layers, the upper layer (2.84–2.85 g cm−3) and the lower layer (3.12 g cm−3). The Moldanubian has the thickest lower crust (~20 km) with a density of 2.98 g cm−3; the lower crust in the Moravo–Silesian has a density of 2.97 g cm−3. The Western Carpathian– Pannonian region is represented by slightly lower densities of 2.94–2.96 g cm−3. The gravity modelling indicates that the Western Carpathians were overthrusted by ~30 km onto the Bohemian Massif resulting in a neo-transformation of the crust/mantle and related lithosphere after subduction.