Middle-late Eocene dinoflagellate cysts from NE Ukraine (Borehole No. 230, Dnepr-Donets Depression): Stratigraphic and palaeoenvironmental approach

Abstract

Analysis of the stratigraphic and quantitative distribution of dinoflagellate cysts and other palynomorphs from a shallow marine Eocene section drilled from borehole No. 230 (NE Ukraine) resulted in an updated age-assessment of regional formations and a reconstruction of the major transgressive-regressive trends in the North Ukrainian palaeosedimentological province. Based on dinocyst age-diagnostic events, the Buchak Formation is attributed to the mid-upper Lutetian; the Kiev Formation is assigned to the Bartonian-?lowermost Priabonian; finally, the Obukhov Formation is dated Priabonian. The Buchak Formation accumulation reflects the first major transgressive episode in the North Ukrainian Province; the accumulation of the lower Kiev Formation corresponds to the maximum of regional marine transgression, while the palynological assemblages from the upper Kiev Formation indicate a protracted regression. The beginning of the Obukhov Formation accumulation corresponds to the last marine transgressive cycle.