New data on Caledonian, Alpine-style folding in the Holy Cross Mts., Poland

Abstract

There has been a century-long debate on the nature of the major orogeny in the Holy Cross Mts. Some research workers consider that they were folded during the Variscan orogeny, and that Caledonian movements were responsible only for the formation of mesostructures. Others provide evidence for great folding movements and detachments, suggesting that strong Caledonian compression formed or “squeezed out” Ordovician-Silurian synclines; they consider Variscan deformation to be of platform-type. Laramide and Late Alpine platform-type faults also deformed the Holy Cross Mts. Ordovician haematites  show 3 generations of folds in the Brzeziny Syncline, showing it to be over 250 m in amplitude. This structure is thus not a mesostructure but a large-scale structure formed as a result of  orogenic compression. The Devonian-Carboniferous cover shows a platform tectonic style. Differences in style between the folded Cambro-Silurian basement  and the unconformably overlying Devonian-Carboniferous sedimentary cover are great and cannot be explained in terms of different rock competence. These tectonic relationships are supported by borehole and geophysical evidence. The Caledonian faulting style is identical in the southern part of the Holy Cross Mts. and the northern Łysogóry area. Laramide and Late Alpine stresses are likely related to Atlantic ocean-floor spreading; stresses acting on the  crystalline margin of the East European Craton rejuvenated tectonic lineaments in the Holy Cross Mts. and deformed the Devonian-Cenozoic cover throughout the Polish Lowlands.