The foraminifera-based biostratigraphy of the Middle and Upper Jurassic of the Polish Lowlands was re-evaluated. Biostratigraphic charts providing ranges of the most important foraminiferal taxa characteristic of individual Jurassic stages are presented in relation to the currently used ammonite-based standard stratigraphic divisions. The study contains the new research on the foraminifera fauna and includes earlier results available in published and archival reports. In the Oxfordian and Lower Kimmeridgian deposits, various foraminiferal assemblages were distinguished with reference to the lithofacies in the individual parts of the Polish Basin and varying influences of the palaeogeographical provinces. Additionally, the foraminiferal zones in the Oxfordian and Lower Kimmeridgian deposits of southeastern Poland are distinguished based on detail study of foraminifers.
The Kamyanyi (Kaminnyi) Potik Unit (Nappe) is the most internal and structurally-highest unit of the Fore-Marmarosh units, and in many places is directly covered by the Marmarosh Nappes of the Marmarosh Crystalline Massif. Chyvchyn Mount is built of this unit and forms a separate tectonic cap (Chyvchyn Mt. Klippe). It consists of the Upper Jurassic/lowermost Cretaceous Chyvchyn Formation, composed mainly of basic volcanic rocks, and the Tithonian-Early Cretaceous Kamyanyi Potik Formation, represented by calcareous and/or turbiditic deposits containing volcanic material. Geological mapping showed that this complex forms a tectonic klippe, which consists of four small tectonic thrust slices. Structurally, the lowermost one is represented by thin-bedded micritic limestones with cherts, and is interbedded with coarse/fine-grained calcareous pyroclastic turbidites (flysch). The second thrust slice is composed of calcareous-pyroclastic breccia with blocks of limestone, basalt, and chert (radiolarite?), which occur within a pyroclastic matrix and of coral limestones with basalt fragments and pyroclastic intercalations. The third thrust slice is constructed of breccia with a pyroclastic and volcanic matrix and clasts of effusive rocks and limestone. The fourth thrust slice – the highest – is represented by massive basaltic pillow lavas. Sedimentologically, the volcano-sedimentary complex represents a whole spectrum of marine mass-movement deposits, from debris flows through proximal turbidites to distal ones, which were formed during latest Jurassic/earliest Cretaceous time in the Outer Dacide-Severinide part of the Carpathian basins.
The Lower Jurassic and the lower part of the Middle Jurassic deposits corresponding to the Sołtysia Marlstone Formation of the Lower Subtatric (Krížna) nappe in the Kopy Sołtysie mountain range of the High Tatra Mts and the Płaczliwa Skała (= Ždziarska Vidla) mountain of the Belianske Tatra Mts in the eastern part of the Tatra Mts in Poland and Slovakia are described. The work concentrates both on their lithological and facies development as well as their ammonite faunal content and their chronostratigraphy. These are basinal deposits which show the dominant facies of the fleckenkalk-fleckenmergel type and reveal the succession of several palaeontological microfacies types from the spiculite microfacies (Sinemurian–Lower Pliensbachian, but locally also in the Bajocian), up to the radiolarian microfacies (Upper Pliensbachian and Toarcian, Bajocian–Bathonian), and locally the Bositra (filament) microfacies (Bajocian–Bathonian). In addition, there appear intercalations of detrital deposits – both bioclastic limestones and breccias – formed by downslope transport from elevated areas (junction of the Sinemurian and Pliensbachian, Upper Toarcian, and Bajocian). The uppermost Toarcian – lowermost Bajocian interval is represented by marly-shaly deposits with a marked admixture of siliciclastic material. The deposits are correlated with the coeval deposits of the Lower Subtatric nappe of the western part of the Tatra Mts (the Bobrowiec unit), as well as with the autochthonous-parachthonous Hightatric units, but also with those of the Czorsztyn and Niedzica successions of the Pieniny Klippen Belt, in Poland. The character of the deposits in the sequences, and their biostratigraphical analysis, show that sedimentation during the Early Jurassic, and up to the Late Bajocian, was controlled by rifting phases which were active at the junction of the Sinemurian and Pliensbachian (Zliechov Phase), during the Late Pliensbachian and Toarcian (Devín Phase), and during the Bajocian (Krasín Phase). The onset of pelagic sedimentation overlying the rift strata took place during the latest Bajocian. Selected ammonite taxa are illustrated and discussed.
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