Giant-scale cross-bedded Miocene biocalcarenites in the northern margin of the Carpathian foredeep
Abstract
Nasypy przekątnie wielkoskalowo warstwowane w mioceńskich biokalkarenitach południowego obrzeżenia Gór Swiętokrzyskich
Biocalcarenite bodies with giant-scale cross-bedding occur along the southern margin of the Góry Świętokrzyskie mountains which during the Miocene bordered the sedimentary basin of the Carpathian Foredeep from the north. The biocalcarenite bodies occur in a zone about 25 km long and up to 3 km wide; their thickness attains 35 m. The biocalcarenitc bodies are tripartite in vertical section - they consist of bottomset, foreset and topset divisions. The individual tabular sets of cross-strata in the foreset deposits arc up to 17 m thick. The foreset cross-strata dip steeply (average value of the maximum dip of the foreset strata is 2º) southward, that is towards the Carpathian Foredeep. The topsct deposits consist of horizontally stratified biocalcarcnites up to 5 m thick. The bottomset deposits are either cross-stratified in various directions or massive; locally they form lenticular slumped bodies with erosional bases. The biocalcarenite bodies were deposited in a nearshore zone at the northern margin of the Carpathian Forcdeep during the tectonic uplift of the of the Góry Świętokrzyskie. A longshore current flowing from NEE to SWW earned bioclastic debris eroded from the nearshore area. The current crossed obliquely the edge of an initial escarpment that was probably an E - W-oriented synsediinentary fault scarp. The bioclastic debris fell down at the upper edge of the scarp and was laid down parallel to the south-dipping scarp at the angle of repose. The low specific weight of the biocalcarcnites grains could facilitate the formation of the giant-scale cross-stratified bodies.
Biocalcarenite bodies with giant-scale cross-bedding occur along the southern margin of the Góry Świętokrzyskie mountains which during the Miocene bordered the sedimentary basin of the Carpathian Foredeep from the north. The biocalcarenite bodies occur in a zone about 25 km long and up to 3 km wide; their thickness attains 35 m. The biocalcarenitc bodies are tripartite in vertical section - they consist of bottomset, foreset and topset divisions. The individual tabular sets of cross-strata in the foreset deposits arc up to 17 m thick. The foreset cross-strata dip steeply (average value of the maximum dip of the foreset strata is 2º) southward, that is towards the Carpathian Foredeep. The topsct deposits consist of horizontally stratified biocalcarcnites up to 5 m thick. The bottomset deposits are either cross-stratified in various directions or massive; locally they form lenticular slumped bodies with erosional bases. The biocalcarenite bodies were deposited in a nearshore zone at the northern margin of the Carpathian Forcdeep during the tectonic uplift of the of the Góry Świętokrzyskie. A longshore current flowing from NEE to SWW earned bioclastic debris eroded from the nearshore area. The current crossed obliquely the edge of an initial escarpment that was probably an E - W-oriented synsediinentary fault scarp. The bioclastic debris fell down at the upper edge of the scarp and was laid down parallel to the south-dipping scarp at the angle of repose. The low specific weight of the biocalcarcnites grains could facilitate the formation of the giant-scale cross-stratified bodies.