Heterogeneous tectonic inversion of the Mid-Polish Trough related to crustal architecture, sedimentary patterns and structural inheritance

Abstract

Using a 3-D structural model, we performed a basin-scale analysis of the tectonically inverted Mid-Polish Swell, which developed above the NW–SE-oriented Teisseyre-Tornquist Zone. The later separates the Paleozoic West European Platform from the Precambrian East European Craton. The model permits a comparison between the present depths and sedimentary thicknesses of five layers within the Permian–Mesozoic and Cenozoic successions. The inversion of the NW–SE-trending Mid-Polish Trough during the Late Cretaceous–Paleogene resulted in uplift of a central horst, the Mid-Polish Swell, bounded by two lateral troughs. These structural features are induced by squeezing of a weak crust along the Teisseyre-Tornquist Zone. The swell is characterized by an inherited segmentation which is due to NE–SW transversal faults having crustal roots. From NW to SE, we distinguish the Pomeranian, Kujavian, and Małopolska segments, that are separated by two transversal faults. During the inversion, the Zechstein salt occurring in the Pomeranian and Kujavian segments in the NW acted as decoupling level between the basement and the post-salt cover, leading to disharmonic deformation. Conversely, because no salt occurs in the SE, both basement and cover were jointly deformed. The vertical tectonic uplift at the surface is estimated to amount to 3 km in the Małopolska segment. The structural inheritance of the basement is expressed by the heterogeneous geometry of the swell and tectonic instability during Mesozoic sedimentation. The reasons for the inheritance are seen in the mosaic-type Paleozoic basement SW of the Teisseyre-Tornquist Zone, contrasting the Precambrian East European Craton which acted as a stable buttress in the NE. The horst and trough geometry of Cenozoic sediments blanketing the Mid-Polish swell reveals the ongoing intracontinental compressional stress in Poland.