New dinoflagellate cyst species from the Middle Eocene of the Volgograd–Volga region, south-west Russia

Abstract

The Keresta Formation, located in the Volgograd–Volga region (the Volga–Caspian subregion of south-west Russia) has been dated as Middle Eocene, Lutetian, based on dinoflagellate cysts of the Enneadocysta arcuata Zone and nannofossils from the Lutetian subzones CP13c–CP14a. Within this interval, four new species of dinoflagellate cysts are described: Spiniferella grigorovichiae sp. nov., Impagidinium tuberculatum sp. nov., Hystrichostrogylon crassitunicatum sp. nov. and Hystrichosphaeropsis tenerum sp. nov. The new species present a high correlation potential for Middle Eocene stratigraphy over the southern part of the Russian Platform. Also, the assemblage of organic-walled microphytoplankton from the Keresta Formation indicates warm-water marine environments within the marginal part of the Paratethys Basin.

Keywords:

• dinoflagellate cysts
• Middle Eocene
• Lutetian
• south-west Russia
• Volgograd–Volga region; taxonomy

Acknowledgements

The author is grateful to the authorities of the ‘EuroChem-VolgaKaliy’ company for granting permission to work with core materials and publish results; V.V. Savin (chief hydrogeologist of company) and V.A. Musatov (Lower Volga Institute of Geology and Geophysics) are acknowledged for their cooperation. The author expresses deep gratitude to Manuel Vieira and an anonymous reviewer for their constructive and kind review of the manuscript. The author would like to thank Przemysław Gedl for editing the manuscript. Editor-in-chief James B. Riding (Nottingham, UK) is thanked for valuable ideas and publishing support. The research was conducted within the framework of the theme FUMZ-2023-0009, state assignment 123011800010-5, with budget financing by the Institute of Geology and Geochemistry of the Ural Branch, Russian Academy of Sciences.

Disclosure statement

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.