Development and inversion of Devonian and Carboniferous basins in the eastern part of the Variscan foreland (Poland)

Abstract

The Polish part of the Central European Variscan foreland includes several regional units that differ in crustal structure and are characterized by distinct Devonian to Carboniferous subsidence and depositional histories. These units responded differently to palaeostress changes along the southern margin of the Old Red Continent. During the Devonian to Namurian A, areas located to the south-west of the Teisseyre-Tornquist Zone (TTZ), including the Upper Silesian Coal Basin, Małopolska and Łysogóry-Radom blocks, were influenced by stress fields similar to those in the westward adjacent Rheno-Hercynian Zone, whilst the Lublin Basin, located to the north-east of the TTZ, shows a similar development to the Pripyat-Dniepr-Donets rift system. After the Namurian A, the entire southern Polish foreland started to respond in a more consistent way to the build-up of synorogenic compressional stresses, implying a more uniform development of the stress field. During the Namurian B to early Westphalian D, the Polish foreland was dominated by north-directed compressional stresses emanating from the Southeastern Variscan Belt. During the late Westphalian and early Stephanian, the entire foreland underwent compressional deformation and concomitant basin inversion under the influence of stresses propagating from the Moravian-Silesian Fold-and-Thrust Belt. In the Polish foreland, the development of Devonian-Carboniferous basins, as well as the architecture of Variscan structures, clearly reflect the reactivation of pre-existing crustal discontinuities, including specifically the TTZ, but also other major geophysically defined crustal boundaries. In general, thick-skinned tectonics controlled by the inherited structural grain of the basement prevailed, whereas structural decoupling, resulting in the development of minor thrusts and reverse faulting, was of local significance only. The distinct structural-depositional development of the Pomerania region reflects its distal location with respect to the evolving orogen. Orogenic compression influenced this area only indirectly, with the TTZ acting as a guide for the transmission of transtensional and transpressional stresses.