Calcareous nannoplankton in the Upper Jurassic marine deposits of the Bohemian Massif: new data concerning the Boreal–Tethyan communication corridor

Calcareous nannoplankton assemblages from the Jurassic relict deposits in the northern part of the Bohemian Massif are described here for the first time. They are generally of low diversity and dominated by watznaueriaceans. Some of them are diagenetically affected, probably due to dolomitisation. Calcareous nannoplankton enables the stratigraphical range of the Northern Bohemia Jurassic succession to be extended to the Tithonian by reference to the stratigraphical range of Jurassic platform sequences in Central Poland and the eastern part of the Bohemian Massif. The Oxfordian–Kimmeridgian nannofossil assemblages indicate a generally oligotrophic condition of the restricted sea with episodic fluvial input containing terrestrial nutrients. The character of the upper part of the water column was generally uniform and did not reflect variability at the sea-floor expressed by lithofacies diversity. The palaeoenvironment interpreted for the famous former palaeontological locality “Sternberk Quarry” was characterized by a higher nutrient content and more stable environment. The Tithonian nannofossil assemblages contain warm-water Tethyan taxa which suggest south-north migration of nannoplankton due to warming during the Jurassic–Cretaceous boundary interval

Quantitative calcareous nannoplankton biostratigraphy of the Oligocene/Miocene boundary interval in the northern part of the Buda Basin (Central Paratethys)

Relative abundances of seventeen calcareous nannoplankton species were analysed from around the Oligocene/Miocene boundary interval (NP 25-NN 2 Zones) in the northern part of the Buda Basin (Central Paratethys). A succession of four bioevents can be observed in all sections: FAD of Helicosphaera carteri, FAD of Reticulofenestra cf. pseudoumbilica, and FADs of Discoaster druggii and Helicosphaera scissura, FAD of Helicosphaera ampliaperta. The ligocene/Miocene boundary lies between the FAD of Reticulofenestra cf. pseudoumbilica and FADs of Discoaster druggii and Helicosphaera scissura; events known to approximate it are not recognized

Timing of Langhian bioevents in the Carpathian Foredeep and northern Pannonian Basin in relation to oceanographic, tectonic and climatic processes

The succession of bioevents in planktonic foraminifer and calcareous nannoplankton communities is reviewed and summarized for the Carpathian Foredeep and northern Pannonian Basin in the time interval between ~16 and 13.5 Ma. This succession can be subdivided into three principal intervals: (1) an interval with rare Praeorbulina sicana and P. glomerosa. It was characterized by a limited immigration of index taxa linked to the lack of a warm surface water layer in the Central Paratethys. This interval can be correlated with the first Badenian transgression near the Burdigalian/Langhian boundary. The rare occurrence of biostratigraphical markers does not allow its precise dating and interregional correlation; (2) a brief interval of the first occurrences of Praeorbulina circularis, Orbulina suturalis and Helicosphaera waltrans. This can be related to the formation of a warm surface water layer suitable for the survival of orbulinas and praeorbulinas and a change from estuarine to anti-estuarine circulation. This interval can be correlated with the second Badenian transgression, which, however, was not isochronous over the area as inferred from different successions of these first occurrences; (3) a limited appearance of new index taxa in the Central Paratethys prior to the Wielician Salinity Crisis. This time interval was characterized by increased seasonality and salinity oscillations followed by climate cooling. A “reverse” migration of the stress-tolerant species Helicosphaera walbersdorfensis from the Central Paratethys to the Mediterranean is suggested. Several local bioevents with limited stratigraphic correlation potential have been recognized in this interval

Timing of Langhian bioevents in the Carpathian Foredeep and northern Pannonian Basin in relation to oceanographic, tectonic and climatic processes

The succession of bioevents in planktonic foraminifer and calcareous nannoplankton communities is reviewed and summarized for the Carpathian Foredeep and northern Pannonian Basin in the time interval between ~16 and 13.5 Ma. This succession can be subdivided into three principal intervals: (1) an interval with rare Praeorbulina sicana and P. glomerosa. It was characterized by a limited immigration of index taxa linked to the lack of a warm surface water layer in the Central Paratethys. This interval can be correlated with the first Badenian transgression near the Burdigalian/Langhian boundary. The rare occurrence of biostratigraphical markers does not allow its precise dating and interregional correlation; (2) a brief interval of the first occurrences of Praeorbulina circularis, Orbulina suturalis and Helicosphaera waltrans. This can be related to the formation of a warm surface water layer suitable for the survival of orbulinas and praeorbulinas and a change from estuarine to anti-estuarine circulation. This interval can be correlated with the second Badenian transgression, which, however, was not isochronous over the area as inferred from different successions of these first occurrences; (3) a limited appearance of new index taxa in the Central Paratethys prior to the Wielician Salinity Crisis. This time interval was characterized by increased seasonality and salinity oscillations followed by climate cooling. A “reverse” migration of the stress-tolerant species Helicosphaera walbersdorfensis from the Central Paratethys to the Mediterranean is suggested. Several local bioevents with limited stratigraphic correlation potential have been recognized in this interval

The earliest Badenian Planostegina bloom deposit: reflection of an unusual environment in the westernmost Carpathian Foredeep (Czech Republic)

The Miocene sedimentation history of the Brus denudation relict (the western part of the Carpathian Foredeep, Czech Republic) has been inferred from 20 m of silt/siltstones, sand/sandstones and limestones penetrated by the Brus-1 borehole. Detailed multiproxy lithofacies and biofacies analyses have allowed facies and palaeoenvironment interpretations. The presence of molluscs, brachiopods and fish fauna, as well as large benthic and epiphytic foraminifera indicates a generally shallow, subtropical, marine environment. Despite the scarcity of biostratigraphical markers, the section can be correlated with the lowermost Badenian (~15-16 Ma). In the siltstones in the lower part of the borehole, there are abundant low-salinity foraminifera, which may indicate increased rainfall. Linked to this is the nutrient enrichment of the sea bottom water inferred from the presence of the high-nutrient taxa accompanied by abundant calcareous nannoplankton eutrophic taxa such as Coccolithus pelagicus and eutrophic planktonic foraminifera of the Globigerina bulloides/praebulloides group. The main Planostegina bloom was recorded in a sandstone in the interval 12.5-7 m, and was not influenced by a shift from high-organic content Valvulineria assemblage of small foraminifera to an epiphytic one. The boundary between siliciclastic and carbonate sedimentation (-7.5 m) shows a drop in K and Th concentrations, and in the Th/U ratio, but a rise in the Th/K ratio. This change in radioactive element content may generally indicate a significant decrease in terrestrial sediment input which is further supported by the onset of limestone deposition. Reversal of the deposition regime and a decrease of clastic input into the basin may be related to the changing of the precipitation regime, probably triggered by orbitally-forced cyclicity

The earliest Badenian Planostegina bloom deposit : reflection of an unusual environment in the westernmost Carpathian Foredeep (Czech Republic)

The Miocene sedimentation history of the Brus denudation relict (the western part of the Carpathian Foredeep, Czech Republic) has been inferred from 20 m of silt/siltstones, sand/sandstones and limestones penetrated by the Brus-1 borehole. Detailed multiproxy lithofacies and biofacies analyses have allowed facies and palaeoenvironment interpretations. The presence of molluscs, brachiopods and fish fauna, as well as large benthic and epiphytic foraminifera indicates a generally shallow, subtropical, marine environment. Despite the scarcity of biostratigraphical markers, the section can be correlated with the lowermost Badenian (~15-16 Ma). In the siltstones in the lower part of the borehole, there are abundant low-salinity foraminifera, which may indicate increased rainfall. Linked to this is the nutrient enrichment of the sea bottom water inferred from the presence of the high-nutrient taxa accompanied by abundant calcareous nannoplankton eutrophic taxa such as Coccolithus pelagicus and eutrophic planktonic foraminifera of the Globigerina bulloides/praebulloides group. The main Planostegina bloom was recorded in a sandstone in the interval 12.5-7 m, and was not influenced by a shift from high-organic content Valvulineria assemblage of small foraminifera to an epiphytic one. The boundary between siliciclastic and carbonate sedimentation (-7.5 m) shows a drop in K and Th concentrations, and in the Th/U ratio, but a rise in the Th/K ratio. This change in radioactive element content may generally indicate a significant decrease in terrestrial sediment input which is further supported by the onset of limestone deposition. Reversal of the deposition regime and a decrease of clastic input into the basin may be related to the changing of the precipitation regime, probably triggered by orbitally-forced cyclicity