Late Eocene to Quaternary deformation and stress field evolution of the Orava region (Western Carpathians)

Abstract

The northern part of theWestern Carpathians suffered polyphase deformation at the boundary between their Central and Outer parts. Palaeostress analysis in the Orava region revealed the existence of five different stress fields in the period from the Late Eocene to the Quaternary. The evolution of the stress fields was determined by detailed structural analysis of the fault slip and fold orientation data. The orientation of the stress fields shows an apparent clockwise rotation from the Late Eocene to the Quaternary. During the Late Eocene to Oligocene, E–W compression and perpendicular tension affected this area. This was the time when the Central Carpathian Palaeogene Basin formed.After this compression, the palaeostress field rotated approximately 40–50°, and NW– SE compression and NE–SWtension took place in the EarlyMiocene. TheMiddleMiocene to Pliocene was characterised by progressive rotation of the palaeostress field from NW–SE to the NE–SW direction of the maximum principal compressional stress axis (σ₁). This clockwise rotation of the Oligocene to Quaternary palaeostress fields here is explained by the effect of the counterclockwise rotation of theALCAPAmicroplate, and by the regional stress field changes in this region. The Quaternary stress field was reconstructed on the basis of structural measurements in the Pliocene sedimentary formations of the Orava–Nowy Targ Basin. The results of the palaeostress analysis show that the Quaternary stress field is characterised by E–W-oriented S_h (minimum horizontal compression) and N–S-oriented S_H (maximum horizontal compression).