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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.

Cysty Dinoflagellata z górnego kampanu i najniższego mastrychtu (górna kreda) profilu środkowej Wisły : stratygrafia i paleoekologia

Nechwedowicz Mariusz

Przegląd Geologiczny

2022

Vol. 70, nr 10

751--760

Among the rich dinoflagellate cyst assemblages recovered from the upper Campanian-lowermost Maastrichtian succession of the Middle Vistula River section (central Poland), four taxa (Callaiosphaeridium bicoronatum, Odontochitina dilatata, Oligosphaeridium araneum and Samlandia paucitabulata) have been described as new. An analysis of the distribution of particular dinoflagellate cyst taxa enabled the development of a highly resolved biostratigraphic framework, calibrated against other biozonal schemes (based, among others, on inoceramid bivalves, ammonites and belemnites), formerly established for the succession. A comparison of the Middle Vistula River record with the dinoflagellate cyst ranges documented in other European successions enabled correlations with selected sections in Belgium, the Netherlands, southern Germany and northern Italy, and with the Campanian/Maastrichtian boundary stratotype section in Tercis les Bains, southwest France. A palaeoecological analysis of the dino- flagellate cyst assemblages and of other components of phytoplankton communities revealed a well-defined trend in sea-level fluctuations (likely of eustatic origin), and palaeoclimatic changes probably related to the latest Cretaceous cooling episode, as observed elsewhere.