Berriasian

This article is concerned with nannofossil study of Tithonian-Berriasian sediments of Eastern Crimea. The NJT 16, NJT 17a, NJT 17b, NKT, and NK 1 nannofossil zones were determined. The occurrence of Nannoconus kamptneri minor, one of the potential marker-types of the Tithonian-Berriasian boundary (the base of the NKT Zone) of the Tethyan sequence in the Feodosiyan section is assigned here to the Pseudosubplanites grandis ammonite Subzone and the magnetic Chron M18n. The base of the NKT Zone is closer to the Grandis Subzone base than to the base of the Jacobi Subzone. Contradictions in the interpretation of magnetic chrons obtained by the present authors (Arkadiev et al. 2018) and by Bakhmutov et al. (2018) might be caused by mistakes admitted in the latter work on the compiled section.

For more than a century, a number of ammonite taxa of supposed Tethyan origin or affinity have been reported from the Berriasian condensed deposits of Russia (referred to as 'Ryazanian'). These occurrences have been used to constrain long-distance correlation and palaeobiogeo-graphic interpretation of the Russian Platform during the earliest Cretaceous. We revise these taxa herein. To accommodate the systematic issues, we introduce a new ammonite genus: Mittaites n. gen. (type species: Mazenoticeras ceccai). We also provide re-assessment for the genera Tauri-coceras (= Subriasanites), Riasanella, Riasanites, Prorjasanites, and Karasyazites. Considering the strong affinities between these genera (except for Karasyazites), resctricted palaeobiogeographic distribution and a problematic phyletic origin, we erect a new family Riasanitidae n. fam. Our re-examination suggests that the occurrence of western Tethyan migrants in the type 'Ryazanian' should be ruled out. Pending new investigation, correlation of the ammonites of the type 'Ryazanian' beds with the Berriasian part of the Standard Mediterranean Ammonite Scale (SMAS) should be treated with caution.

Тhe ammonites Fauriella boissieri (Pictet), F. rarefurcata (Pictet), F. simplicicostata (Mazenot), Тimovella alpillensis (Мazenot), Jabronella cf. paquieri (Simionescu) characterized the boissieri zone of цррег berriasian оf the Crimean mountains аге described.

This article is concerned with nannofossil study of Tithonian–Berriasian sediments of Eastern Crimea. The NJT 16, NJT 17a, NJT 17b, NKT, and NK 1 nannofossil zones were determined. The occurrence of Nannoconus kamptneri minor, one of the potential marker-types of the Tithonian–Berriasian boundary (the base of the NKT Zone) of the Tethyan sequence in the Feodosiyan section is assigned here to the Pseudosubplanites grandis ammonite Subzone and the magnetic Chron M18n. The base of the NKT Zone is closer to the Grandis Subzone base than to the base of the Jacobi Subzone. Contradictions in the interpretation of magnetic chrons obtained by the present authors (Arkadiev et al. 2018) and by Bakhmutov et al. (2018) might be caused by mistakes admitted in the latter work on the compiled section.

16 species of tintinnids determinates in the Upper tithonian — Berriasian section of the Eastern Crimea. Continuous succession tintinnids zones and almost all subzones established in this section. Zones Chitinoidella and Crassicollaria established in Tithonian, and zone Calpionella in Berriasian, correlated with ammonite zones. A monograph description of tintinnids is given. Refs 69. Figs 3. Tables 2.

The results of bio- and magnetostratigraphic study of the key section "Kabaniy Log" (Belbek river, SW Crimea) where were established the analogues of magnetic chrons M17, M17 (and M15r?) are presented in this article. Upper part of M16r chron is reduced, probably, as a result of detachment. The conplex of foraminifers, found in the upper part of Bechku formation is characteristic of Boissieri, but, in terms of paleomagnetic correlation with Berriasian of Central Cromea, upper part of the Bechku formation corresponds to the upper Occitanica (Tauricum subzone).