Abstract

A palynological and sedimentological study of an outcrop succession adjacent to the village of Kamyanka within the Kharkiv region of northeast Ukraine was carried out. The successions occur within the Dnieper–Donets Basin, which hosts vast successions (> 20 km) of post mid-Devonian strata and is one of the main hydrocarbon-producing basins in Europe. Middle Jurassic sandstones, siltstones and claystones represent the sedimentary successions at the Kamyanska locality. Few palynological studies have been performed on the Jurassic of Ukraine and even fewer presented in the international literature. Thirty spore taxa and 21 pollen taxa were identified, together with taxa kept in open nomenclature (e.g. bisaccate pollen). Two palynological assemblages were identified within the Kamyanska succession (assemblages A and B) dated as Bathonian. Assemblage A is dominated by the fern spores (Cyathidites and Osmundacidites) and gymnosperm pollen produced by Cupressaceae (Perinopollenites elatoides), ginkgophytes/Cycadales/Bennettitales (monosulcates) and Cheirolepidiaceae (Classopollis). Assemblage B differs in also comprising high abundances of Gleicheniidites and higher percentages of Pinuspollenites and Araucariacites compared to assemblage A. Another difference between the two units is the high relative abundance of seed fern pollen (Alisporites) in the upper part of assemblage B. The thermal alteration index (TAI) of the palynomorphs is estimated to range from 3 to 3.5, indicating a burial depth corresponding to the mature main phase of liquid petroleum and, to some extent, gas generation. Comparisons between the miospore and macrofloral assemblages show that the palynoflora and macroflora are strongly similar at broad taxonomic levels. Importantly, the miospore assemblages described here compare well with European Middle Jurassic assemblages indicating limited provincialism, with similar vegetation extending from eastern Ukraine and across most of Western Europe.

Highlights

  • Material and methodsTwelve samples were collected for palynological analysis from a locality east of the village of Kamyanka from a series of outcrops along the western bank of the Donets River (Fig. 3)

  • A palynological and sedimentological study of an outcrop succession adjacent to the village of Kamyanka within the Kharkiv region of northeast Ukraine was carried out

  • Total values are presented in bold this study is to describe the palynoflora from this palynologically previously unstudied site along the Donets River, using an integrative approach based on the collaboration between eastern and western palynologists, to assess the age and the ecological context of the alternating marine and continental Kamyanska suite and to compare the miospore assemblages with the macroflora

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Summary

Material and methods

Twelve samples were collected for palynological analysis from a locality east of the village of Kamyanka from a series of outcrops along the western bank of the Donets River (Fig. 3). Other differences within the gymnosperms between the two units are the high relative abundance of seed fern pollen (Alisporites) in the top of the succession of sub-suite 2 (assemblage B). The Ukrainian Middle Jurassic flora is similar to coeval assemblages from Sweden (Tralau 1967, 1968; Guy-Ohlson 1971, 1986; Vajda 2001) and Denmark (Dybkjær 1988; Mehlqvist et al 2009) These assemblages are typically composed of abundant fern spores, often dominated by Cyathidites/Deltoidospora spp., abundant conifer pollen, often dominated by Cheirolepidiaceae (Classopollis spp.), Cupressaceae (e.g. Perinopollenites elatoides) and Araucariaceae pollen (e.g. Araucariacites australis and Callialasporites spp.) and bisaccate pollen produced from a mixture of conifers (e.g. Pinuspollenites spp.) and seed ferns (e.g. Alisporites spp.). Similar findings from coeval deposits from the Jurassic of Yorkshire, UK (e.g. Slater et al 2015), and Poland (Ziaja 2006) suggest that these patterns represent consistent ecological, taphonomic and recognition biases that act across different depositional environments

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