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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.

Revision of Hamites wernickei Wollemann, 1902 (Cephalopoda, Ancyloceratina) from the classic Lüneburg section (Upper Cretaceous, northern Germany)

Niebuhr B., Jagt J. W. M.

Acta Geologica Polonica

2016

Vol. 66, no. 4

627--644

A re-examination of heteromorph ammonites of late Campanian age from the Zeltberg section at Lüneburg has demonstrated that the type series of Hamites wernickei in fact comprises two different species that are here assigned to the nostoceratid Nostoceras Hyatt, 1894 and the polyptychoceratid Oxybeloceras Hyatt, 1900. Nostoceras (Didymoceras) wernickei (Wollemann, 1902) comb. nov., to which three of the four specimens that were described and illustrated by Wollemann (1902) belong, has irregularities of ribbing and tuberculation and changes its direction of growth at the transition from the helicoidal whorls to the hook, which is a typical feature of members of the subfamily Nostoceratinae. Torsion of body chambers is not developed in hairpin-shaped ammonite species, which means that the species name wernickei is no longer available for such polyptychoceratine diplomoceratids. Consequently, the fourth specimen figured and assigned to Hamites wernickei by Wollemann (1902) is here transferred to Oxybeloceras and considered conspecific to material from the Hannover area (Lehrte West Syncline) as O. aff. crassum (Whitfield, 1877). In addition to the "Heteroceras-Schicht des Mucronaten-Senons" of Lüneburg (bipunctatum /roemeri Zone, upper upper Campanian), the geographic range of N. (D.) wernickei probably includes Upper Austria, Tunisia and the Donbass region, while O. aff. crassum is known from the Hannover area (northern Germany), southern France, northern Spain and Upper Austria.