Strukturalne, litologiczne oraz tektoniczne uwarunkowania rozwoju i ewolucji świętokrzyskich skałek piaskowcowych
Abstract
Structural, lithological and tectonic constraints on the development and evolution of sandstone tors in the Świętokrzyskie (Holy Cross) Mountains.
A b s t r a c t. Majority of ca. 90 sites of sandstone crag groups and individual crags, occurring in the Świętokrzyskie (Holy Cross) Mts. region, represent the following crag-forming lithostratigraphic units: Cambrian Wiśniówka Formation, Devonian Barcza Fm and Zagórze Fm, Triassic Zagnańsk Fm and Krynki Beds, as well as Jurassic Skłoby Fm and Ostrowiec Fm. Specific features of these rocks are the occurrence of sandstone series, up to 20 m thick, above more plastic, clayey or heterolithic series, high-energy depositional environments, and siliceous composition. The crag-forming sandstones differ in the amount of siliceous cement: from strongly cemented Paleozoic quartzitic sandstones to porous Mesozoic sandstones with poor cement, which determines diverse mechanical properties. Strongly cemented Paleozoic rocks display high rock strength and abrasion resistance, while porous and theoretically friable Mesozoic sandstones are characterised by high grain packing due to compaction. Regarding the principal role of gravitational disintegration of rock massifs under the periglacial conditions in the Pleistocene, other factors constraining the crag formation and shaping are the tectonic situation of rocks (orientation of strata and joints), adequate joint spacing, and bed thickness. The interrelations between lithological and structural features of crag-forming sandstones and tectonics, conditioning erosion and weathering rates are specific for particular types of these sandstones.
A b s t r a c t. Majority of ca. 90 sites of sandstone crag groups and individual crags, occurring in the Świętokrzyskie (Holy Cross) Mts. region, represent the following crag-forming lithostratigraphic units: Cambrian Wiśniówka Formation, Devonian Barcza Fm and Zagórze Fm, Triassic Zagnańsk Fm and Krynki Beds, as well as Jurassic Skłoby Fm and Ostrowiec Fm. Specific features of these rocks are the occurrence of sandstone series, up to 20 m thick, above more plastic, clayey or heterolithic series, high-energy depositional environments, and siliceous composition. The crag-forming sandstones differ in the amount of siliceous cement: from strongly cemented Paleozoic quartzitic sandstones to porous Mesozoic sandstones with poor cement, which determines diverse mechanical properties. Strongly cemented Paleozoic rocks display high rock strength and abrasion resistance, while porous and theoretically friable Mesozoic sandstones are characterised by high grain packing due to compaction. Regarding the principal role of gravitational disintegration of rock massifs under the periglacial conditions in the Pleistocene, other factors constraining the crag formation and shaping are the tectonic situation of rocks (orientation of strata and joints), adequate joint spacing, and bed thickness. The interrelations between lithological and structural features of crag-forming sandstones and tectonics, conditioning erosion and weathering rates are specific for particular types of these sandstones.