Jurassic system stratigraphy at the Kamianka village. Part 4. The Kamianska formation

Abstract

Introduction. This study focuses on the Jurassic Kamianska Formation of northwestern Donbas, eastern Ukraine and is part of a series of publications concerning Jurassic stratigraphy in the vicinity of the village of Kamianka. The study is especially important because as we here document several classical outcrops containing rich macrofloral assemblages, localities that are in the risk of being damaged, inaccessible, or permanently destroyed due to ongoing military activities in the region.

Material and methods. The study is based on lithological observations and fossils collected from Middle Jurassic deposits of the northwestern Donbas. The focus of the study are the palynological asseblages including the palynoflora and the macroflora, combined with sedimentological data from outcrops. Palynological samples were processed using standard laboratory techniques, including acid maceration, sieving, and microscopic analysis.

Results and discussion. The investigated Bathonian deposits yield diverse palynological assemblages dominated by fern spores and gymnosperm pollen. The most common spores belong to the fern families Gleicheniaceae, Osmundaceae, and Cyatheaceae, whereas gymnosperm pollen is represented mainly by Classopollis, Callialasporites, Perinopollenites, and Araucariacites. The composition of the assemblages indicates that the plants producing these pollen and spores grew in a humid warm-temperate environment. Increased abundance in the upper part of the section of Classopollis, produced by the drought-adapted Cheirolepids, suggests gradual climatic drying during the late Bathonian.

Lithology. The Bathonian deposits are composed predominantly of alternating sandstones, siltstones, carbonaceous claystones . The lower part is sandy, whereas the upper part is mainly clayey with coal lenses, fossil wood, and volcanogenic material. Sedimentary structures indicate deposition within fluvial, deltaic, lagoonal, and marginal- marine environments.

Stratigraphy. Integrated paleobotanical and palynological data confirm the Bathonian age of the Kamianska Formation. The investigated palynological assemblages correlate well with coeval assemblages from Scandinavia and other European regions, particularly with the Callialasporites–Perinopollenites palynozone.

Conclusion. The Kamianska Formation represents an important middle–upper Bathonian unit, located in the northwestern Donbas, Ukraina. The dating of the succession is based on integrated lithological, macrofloral, and palynological analyses documenting a gradual paleoenvironmental changes from humid to relatively drier conditions during time of the sediment accumulation. The late Bathonian macroflora is dominated by ferns and Bennettites accompanied by horsetails, ginkgophytes, and conifers, reflecting vegetation typical of the Middle Jurassic European floral province. The palynological assemblages demonstrate strong similarities with coeval European floras and provide an important basis for regional Jurassic stratigraphic correlations and paleoenvironmental reconstructions.