Deformation style along a fossil transform plate boundary; geophysical investigation of the Central European Variscides

The boundary between the Saxo-Thuringian and Rheno-Hercynian zones represent a Gondwana-Laurussia transform plate boundary in the Bohemian Massif. To the west of the Bohemian Massif, Permo-Mesozoic sedimentary rocks cover the transform plate boundary, which limits our understanding of its spatial and temporal development. We reinterpret Dekorp-2S and 4N and create a composite profile in between, perpendicular to the transform plate boundary. Based on the seismic reflection facies, we define Southeastern, Central and Northwestern Saxo-Thuringian domains (SE, Central and NW domains). Magnetic field intensity and Bouguer gravity anomaly maps and their derivatives further strengthen our interpretation of the Saxo-Thuringian domains and their regional-scale deformation style.

The SE-domain show sub-horizontal and high-amplitude reflections in the southwest and medium-amplitude reflection in the northeast and it is correlated to the medium-grade metamorphosed areas of the Fichtelgebirge and northeastern Münchberg nappe. The Central-domain is characterized by low reflectivity in the upper and the middle crust and it is not developed in the southwest along the Dekorp-2S. The Central-domain is correlated to the early Carboniferous turbidites and the SE Schwarzburg anticline. The NW-domain show high-amplitude and dipping reflections occupying broader areas in the southwest. We interpret the lateral changes along the NW-domain resulting from the regional stress field rotation in the latest Variscan times and thrust reactivation of the former strike-slip shear zones developed along the transform plate boundary. Our results highlight noncylindrical nature of the Variscan lithostructures west of the Bohemian Massif and the regional scale spatiotemporal development of a fossil transform plate boundary.