Tectonics of the Łysogóry unit in the Holy Cross Mts

Abstract

Results of tectonic investigations in the t.ysog6ry unit in the Holy Cross Mts, Central Poland, are presented. The Łysogóry unit is a monocline with subordinate disharmonic-type fold structures. Those· fold structures occur exclusively in the Middle Cambrian and Silurian shale-and-sandstone-bearing complexes, while they are absent from the Upper Cambrian sandstones. This is due to differential tectonic competencies of the sandstones and shales. The present-day geological structures of the area formed under a preponderant influence of the Holy Cross dislocation; this steep and very deep dislocation makes up a boundary between two blocks of the Earth crust. The Upper Cambrian sedimentation developed under conditions of the substrate lability and activity of transverse dislocations causing a variation in subsidence rate. This resulted in variable·thickness (850 to 1,800 m) of the Upper Cambrian deposits. The old dislocations were rejuvenated during the Variscan orogeny. The present-day trans-verse faults are mostly of normal, hinge, or pivotal type. The Łysogóry unit was formed during the Variscan orogeny, probably during the Sudetic phase.