Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: calcareous nannofossil

Sortuj według:

Ogranicz wyniki do:

Integrated biostratigraphy and palaeoenvironments of the Upper Cretaceous in the Petrich section (Central Srednogorie Zone, Bulgaria)

Pavlishina Polina, Dochev Docho, Wagreich Michael, Koukal Veronika

Acta Geologica Polonica

2023

Vol. 73, no. 1

33--62

The Upper Cretaceous succession (Coniacian to lowermost Maastrichtian, with focus on the Campanian) at Petrich, Central Srednogorie Zone in Bulgaria, is described and calibrated stratigraphically based on nannofossils, dinoflagellate cysts and inoceramids. The following standard nannofossil zones and subzones are identified: UC10-UC11ab (middle to upper Coniacian), UC11c-UC12-UC13 (uppermost Coniacian to Santonian), UC14a (lowermost Campanian), UC14bTP-UC15cTP (lower Campanian to ‘middle’ Campanian), UC15dTP-UC15eTP (upper Campanian), UC16aTP (of Thibault et al. 2016; upper part of the upper Campanian), and UC16b (Campanian-Maastrichtian boundary). The base of the Campanian is defined by the FO of Broinsonia parca parca (Stradner) Bukry, 1969 and Calculites obscurus (Deflandre) Prins and Sissingh in Sissingh, 1977 (a morphotype with a wide central longitudinal suture). The Areoligera coronata dinoflagellate cyst Zone (upper lower Campanian to upper upper Campanian) is identified, corresponding to the UC14bTP-UC16aTP nannofossil subzones. The inoceramid assemblage indicates the ‘Inoceramus’ azerbaydjanensis-‘Inoceramus’ vorhelmensis Zone, correlated within the interval of nannofossil subzones UC15dTP-UC15eTP. The composition of the dinoflagellate cyst assemblages and palynofacies pattern suggest normal marine, oxic conditions and low nutrient availability within a distal shelf to open marine depositional environment during the Campanian.

The nannofossil biostratigraphy of the youngest deposits of the Magura Nappe (East of the Szczawa river, Polish Flysch Carpathians)

Oszczypko-Clowes M.

Annales Societatis Geologorum Poloniae

2001

Vol. 71, No 3

139-188

The Magura Nappe is the largest and southernmost tectonic unit of the Western Outer Carpathians and differ in lithofacies development from the Middle and Marginal groups of units. The age studies of the youngest deposits of the Magura Nappe play an important role in understanding the tectogenesis of the Outer Carpathians. The aim of this work was to find the litho- and biostratigraphic correlation with the more external units. For this purpose the youngest deposits from selected sections of the Magura Nappe located east of the Skawa River, were chosen. For the lower limit of the youngest sediments, Middle/Upper Eocene variegated shales with Reticulophragmium amplectens Grzybowski were taken. The analysis of nannoplankton assemblages enable to establish the age of these deposits which varies from Middle Eocene (NP15) up to Upper Oligocene (NP25) and Lower Miocene (NN2). The Eocene/Oligocene boundary lies within the NP21 nanno-zone and was found in the Krynica Zone within the Globigerina Marls (Leluchów section), in the Rača Zone within Poprad Sandstone Mbr of the Magura Fm. and in the Siary Zone within supra-Magura (Budzów) Beds (Budzów section), Wątkowa Sandstone (Ropica and Małastów sections) and within Zembrzyce (sub-Magura) Beds (Folusz section). In the Rača and Krynica zones the youngest - Upper Oligocene deposits from the studied sections belong to the Malcov Fm., whereas in the Siary Zone they belong to the supra-Magura (Budzów) Beds. The age of the Malcov Fm. was determined as NP24 in Leluchów and as NP25 in the Nowy Sącz I borehole, whereas the Budzów Beds belong to zone NP24. The youngest deposits so far described from the Magura Nappe belong to the Zawada Fm. whose age was determined as NN2. In the Polish part of the Bystrica Zone deposits younger than NP18, have so far not been found. The analysis of autochtonous nannoplankton assemblages from the Magura Basin enable to follow the palaeoecological changes in the Magura Basin, both in regional and global sense, from Late Eocene through Oligocene. The global changes are the drop of the water temperature accompanied by the progressing eutrophication of the Magura Basin. Further events were also recorded in zone NP23. The assemblage of this zone was characterised by the presence of species which are believed to be indicative of brackish water and restricted to the Paratethys region.