Біостратиграфія середньої юри центральної та східної частини платформної України

Abstract

The new paleontological data are supplemented by a stratigraphic scheme of the Middle Jurassic in the eastern slope of the Ukrainian shield, the Dnieper-Donets Basin and the north-western part of Donbass. Middle Jurassic sediments stratification of a platform Ukraine was conducted through various groups of fauna and flora. Namely, in the article the full spore-pollen complexes and complexes dinocysts are considered. Other groups, such as the remains of fungi, cuticles, tracheids, acritarchs, microforaminifers, remains of insects, etc., are also characterized by deposits microfossils. In this study, sediment samples from boreholes (wells) and outcrops cutting through Mid-Jurassic, Bajocian, Bathonian, Callovian successions of central Ukraine (the eastern slope of the Ukrainian shield) in the western region of Dnieper-Donets Basin and the north-western part of the Donbass, were analysed palynologically. Over 20 genera of dinocysts have been identified and they represent a wide range of forms; planktonic marine, planktonic coastal, benthic coastal, and freshwater specimens. The taxonomic identification of the dinoflagellate cysts and their vertical distribution enables to recognize six dinoflagellate assemblages from Middle Jurassic: Assemblage I (upper Bajocian – presence of the dinocysts Pareodinia sp., Pareodinia evitti, Gonyaulacysta helicoids); Assemblage II (uppermost Bajocian – Zona Acanthaulax crispa); Assemblage IІІ (lower, middle Bathonian. – Zona Ctenidodinium combazii–Ctenidodinium sellwoodii); Assemblage ІV (middle, upper Bathonian and lowermost Callovian – layers with the dinocysts Pareodinia spp., Ctenidodinium spp.); Assemblage V (the uppermost lower- and middle Callovian – Zona Ctenidodinium ornatum–Ctenidodinium continuum); Assemblage VI (upper Callovian – strata with the dinocysts Ctenidodinium ornatum, Batiacasphaera sp., Chlamydophorella sp., Cleistosphaeridium sp., Epiplosphaera sp., Atopodinium sp., Occisucysta sp, Leptodinium sp., Cribroperidinium granulatum, Dapcodinium sp., Nannoceratopsis sp., Acanthaulax senta, Cyclonephelium sp., Dapcodinium sp., Pareodinia sp., Aldorfia sp.). As a result of a palynological analysis we have established seven spore-pollen complexes for middle Jurassic sediments found in wells and outcrops within the central and eastern parts of Ukraine platform.