The contact between the Pieniny Klippen Belt and Magura Unit (the Male Pieniny Mts.)

Abstract

The fold-and-thrust tectonic stage in the Pieniny Klippen Belt commenced at the Cretaceous-Tertiary boundary (late sub-Hercynian phase) and resulted in the formation of a series of tectonic units. In the Jaworki region these are: the Branisko and Niedzica Nappes, Czertezik and Czorsztyn Units (the last-mentioned unit is considered to be autochthonous). According to previous views, the tectonic stage associated with the Laramian phase (Palaeocene) which followed later, resulted in folding of the peri-klippen parts of the Magura Basin, their “retro-arc thrusting” over the Pieniny Klippen Belt and formation of the Grajcarek Unit. However, during the present studies, no evidence of a rearrangement of tectonic pattern which could be related to retro-arc thrusting, has been recorded. Instead, a possibility of progressive thrusting of the klippen units over the Magura forefield and the Czorsztyn Unit which already lost its autochthonous position, is considered. Consequently: (1) the thrust-nappe folding should be prolonged in time from Maastrichtian until Middle Palaeocene times, (2) the position of the Grajcarek Unit within the Pieniny Klippen Belt should be recognized as tectonic windows of the Magura Unit (but not as tectonic caps of the Magura Unit, back-thrusted and chocked in tectonic grabens) and, (3) the Grajcarek Unit in the peri-klippen part should be included into the Magura Unit, distinguishing, at most, a near-contact deformation zone. The result is that the boundary of the Pieniny Klippen Belt has been shifted southwards, i.e. from the contact between the Grajcarek and Magura Units to the contact between the klippen units and the Grajcarek Unit. In the Jaworki region, the Homole and Biała Woda Blocks must be considered a tectonic cap of the klippen units resting upon the Magura Unit. The Repowa Fault has been described as a new structural element related to the Carpathian arc-like bending.