Pre-Ordovician polyphase tectonics of the Cambrian sequences in the Kielce Unit, Holy Cross Mts. (Central Poland)

Abstract

On a basis of tectonic mesostructures, the pre-late Tremadocian tectonic event (Sandomirian "phase"), believed to account for deformation of the Cambrian system in the Kielce Unit (Holy Cross Mts., Central Poland), has been subdivided into 3 successive tectonic episodes of different kinematics. During the first stage (D1), flat, westerly vergent thrusts originated, giving rise to gravitational sliding. Subsequently, during D2, the entire sequence was imbricated by the northerly vergent thrusts. In the terminal phase (D3), map-scale folds developed, changing inclinations of previously formed structures. Mode of deformation during the D2 stage is typical for thrust and fold belts. Absolute dating of these events remains speculative, but the pre-late Tremadocian age of the D1 and D2 phases is evident. The D3 is considered as a continuation of the D2, but alternative concepts are also acceptable in the light of the presented data.