Górny tyton i berias w płaszczowinie reglowej dolnej Tatr Zachodnich w świetle danych lito-, bio- i magnetostratygraficznych

Abstract

The Upper Tithonian and Berriasian in the Lower Sub-Tatric Nappe of the Western Tatra Mts in the light of litho-, bio- and magnetostratigraphic data (southern Poland).S u m m a r y. Detailed magnetostratigraphic investigations of the Tithonian–Berriasian strata, integrated with litho- and biostratigraphic observations were carried out within the Bobrowiec Unit of the Lower Sub Tatric (Križna) Nappe in theWestern Tatra Mts. Amodification of the existing lithostratigraphic scheme is proposed, splitting the Pieniny Limestone Formation (sensu Lefeld et al. 1985) into two formations, accordingly with lithostratigraphic subdivisions of the coeval deposits in some other parts of the Križna Nappe in Slovakia: the Jasenina Formation (includes Pooerednie Member sensu Pszczółkowski 1996, in its uppermost part) and the Osnica Formation (Osnica Member sensu Pszczółkowski 1996). The Jurassic/Cretaceous boundary, as defined by calpionellids, falls within the lowermost part of the Osnica Fm. Magnetozones from CM20r (Lower/Upper Tithonian boundary) up to CM16n (Upper Berriasian) were identified. Jurassic/Cretaceous boundary is situated within the CM19n magnetozone, below the short reversed Brodno subzone. Magnetostratigraphic correlation of four sections revealed existence of some “gaps” which are interpreted as tectonic reductions, which have to be considered while calculating the sedimentation rate which, however, might be roughly estimated. Sedimentation was relatively slow within the Jasenina Formation (5–7 m/My), but accelerated within the Osnica Fm (mean value: 10–15 m/My) and in the investigated lower part of the Kościeliska Marl Fm (20–30 m/My). Presence of hematite correlates with low sedimentation rate.