Stratigraphic position of the Bajocian crinoidal limestones and their palaeogeographic significance in evolution of the Pieniny Klippen Basin

Abstract

The chronostratigraphical position of the crinoidal limestones in the Pieniny Klippen Belt (Carpathians, Poland) is well documented by ammonite faunas. It corresponds to the stratigraphical interval from the uppermost Propinquans and lowermost Humphriesianum zones of the Lower Bajocian to the Garantiana Zone of the Upper Bajocian. The hiatus recognized at the base of the crinoidal limestone complexes covers the time interval of the Laeviuscula Chron and a bulk of the Propinquans Chron of the Early Bajocian. The sedimentological features found in the basal beds of the crinoidal limestones include: presence of numerous phosphatic concretions, occurrence of pyrite framboids, as well as numerous rests of fauna (mostly ammonites and belemnites), all of them showing a slow sedimentation rate. The rapid change of sedimentation from dark shales of oxygen-depleted environment (Skrzypny Shale Fm. – Aalenian to earliest Bajocian) to overlying light crinoidal grainstones (Smolegowa Limeston Fm., Flaki Limestone Fm.) corresponded to an important geodynamic event that took place during Early Bajocian – the origin of the mid-oceanic Czorsztyn Ridge.