www.geologicacarpathica.sk Barremian-Aptian erosion of the Kysuca-Pieniny trough

Abstract: The Pieniny Klippen Belt is a tectonic melange representing the boundary between the Outer and Central Western Carpathians. Within this melange, Jurassic and Cretaceous sedimentary rocks from deep-water (Kysuca Basin) to shallow-water environments (Czorsztyn Unit) occur. The Nižná Unit of the Pieniny Klippen Belt was distinguished as a particular development of the Kysuca Unit. As a result of a sea-level fall in the Barremian, the Barremian-Aptian Nižná Limestone Formation (organodetritic Urgonian-like facies) rests unconformably on older formations. At the base of this transgressional contact the newly discovered Tvrdošín Breccia Member occurs. This breccia consists of clasts of radiolarites, red limestones, white Calpionella limestones, and black chert nodules extracted from these limestones. The presence of breccia shows that the pre-Barremian strata in the Nižná Unit were eroded to relatively deep levels. This event was coeval with, and probably related to, the hiatus in other units situated on the Czorsztyn Swell. The Nižná Limestone Formation is overlain by the uppermost Aptian to Cenomanian pelagic marlstones, limestones and radiolarites at least 10 m thick. These are followed by flysch with exotic pebble material. Its age is younger than Cenomanian, which contradicts previous opinions. An earlier (Albian) onset of exotic flysches would be indicative of more southern units, close to the exotic Andrusov Ridge. This implies that the Nižná Unit was situated at the northern margin of the sedimentary area of the Kysuca Unit, closer to the Czorsztyn Swell, where the exotic flysch sedimentation came later