Origin of submarine swell (Czorsztyn Ridge of the Pieniny Klippen Belt, Polish/Ukrainian Carpathians) and it's geotectonic consequences by biostratigraphy/volcano-sedimentary record

The most important geotectonic element within Polish/Slovakian/Ukrainian Western Carpathians basins has been the Czorsztyn Ridge (Swell), which originated during Early Bajocian time. Then, palaeogeographicaly during Middle Jurassic–Late Cretaceous span it has been the main object which separated two large Carpathians basins – the Magura Basin on NW side and the Pieniny Basin on SE side – and therefore the detail dating of its origin is crucial for recognition of its geodynamic significance. This first uplift is correlated with stratigraphical hiatus between sedimentation of dark/black shales of oxygen-poor environments (latest Pliensbachian–earliest Bajocian) and white/light grey crinoidal limestones of well oxygenated regimes (late Early Bajocian), which documented drastic change of sedimentation/palaeoenvironments which took place in meantime as effect of uplift. This stratigraphical gap was perfectly dated biostratigraphicaly by ammonites collected from the basal part of crinoidal limestones in several outcrops of the Polish part of the Pieniny Klippen Belt (PKB). The evidences of condensation event at the beginning of crinoidal limestones sedimentation are marked by: phosphatic concretions concentration, pyrite concretions, large clasts of green micritic limestones, fossils (ammonites, belemnites, brachiopods). On the other hand, high variable thickness of these limestones (from ca. 10 m up to 100 m) suggests origin of synsedimentary tectonic blocks and troughs during syn-rift episode. This Bajocian tectonic activity within Pieniny Klippen Basin corresponds very well with others Middle Jurassic Western Tethyan geodynamic reorganizations. Estimation of duration of aforementioned hiatus – based on a cyclostratigraphic analysis of the carbonate content from the Subalpine Basin in France, which indicates that the Early Bajocian only lasted c. 4.082 Ma – time necessary for origin/uplift of the Czorsztyn Ridge is about 2 Ma.

            Tectonic rejuvenation of Middle Jurassic structures took place during the earliest Cretaceous (Berriasian) times and have been connected with active volcanogenic events which occur now within several tectonostratigraphic units of the Ukrainian Carpathians, including PKB. In the Veliky Kamenets active quarry (PKB) a continuous section occurs with a Lower Jurassic (since Hettangian?) to the lowermost Cretaceous (Berriasian) sedimentary succession. The biostratigraphy of the Toarcian-Berriasian part of this section is very precisely based on ammonites, dinoflagellates and calpionellids. Basaltic rocks occur in the uppermost part and overlie creamy-white Calpionella-bearing limestones. They are directly covered by biodetritic limestones and synsedimentary breccias. The latter are the so-called Walentowa Breccia Member of the Łysa Limestone Formation, according to the Polish and Slovakian parts of the PKB, which are dated by calpionellids as middle and/or upper Berriasian and upper Berriasian, respectively. Importantly, in this breccia some clasts of basaltic rocks occur (sometimes developed as pillow lavas and/or peperites) which implies they are middle and/or upper Berriasian in age as well. New investigations are concentrating on radiometric dating of these basaltic rocks, which geochemically have previously been determined to be caused by intra-plate volcanism. Integrated litho-, bio-, chemo- and magnetostratigraphic studies carried out in this section can be here supplemented by absolute age determination of a submarine volcanic event. Additionally, this is a unique chance to calibrate the absolute age of the J/K boundary.