№80-10

Paleoecological conditions of the upper eocene sea: spatial distribution of mollusks in the mandrykivska strata of the Rybalskyi quarry

А. Moskalenko¹, V. Prykhodchenko¹, I. Davydov¹

¹Dnipro University of Technology, Dnipro, Ukraine

Coll.res.pap.nat.min.univ. 2025, 80:105–111

Full text (PDF)

https://doi.org/10.33271/crpnmu/80.105

ABSTRACT

Purpose. The study aims to investigate the spatial distribution of fossil mollusks in the Mandrykivskyi strata of the Rybalskyi quarry and to reconstruct the paleoecological conditions of the Upper Eocene sea.

The methods. The research is based on the analysis of the faunal composition of mollusks collected from seven sampling points within the quarry, covering its southern and southeastern parts. New previously undescribed sections were opened as a result of excavation activities during the 2021 excavations. Six mollusk species were selected for analysis: Glycymeris deletus, Venericardia (Megacardita) dnjenrovensa, Natica epiglottina, Chama calcarata, Trochus lucasianus, and Trochus (Tectus) margaritaceus. Quantitative analysis consisted of the counting of the specimens in each sample, and the data were represented using histograms and distribution maps.

Findings. The processing of the results revealed that paleoecological conditions of the Upper Eocene sea control the spatial distribution of mollusks. Three main zones of distribution were discovered: coastal, transitional, and sublittoral, which represent various conditions of the environment. The coastal zone is distinguished by high density of Glycymeris deletus and Venericardia (Megacardita) dnjenrovensа, which speaks of intense movement of waters. Transitional zone is defined by the availability of algae and ideal conditions for herbivorous mollusks such as Trochus lucasianus and Trochus (Tectus) margaritaceus.The sublittoral zone features calm environmental conditions dominated by predatory mollusks, such as Natica epiglottina.

The originality. The scientific novelty of the study lies in the first-time identification of spatial distribution patterns of mollusks in the Mandrykivskyi strata of the Rybalskyi quarry. Additionally, new sections were exposed and described for the first time in 2021.

Practical implementation. The practical significance of the obtained results lies in their potential use for refining the composition of the Mandrykivskyi strata and reconstructing the paleoecological conditions of the Upper Eocene sea. The data can be further utilized for studies of fauna and correlation of deposits with other regions.

Keywords: Mandrykivskyi strata, Upper Eocene, Rybalskyi quarry, mollusks, paleoecology, spatial distribution.

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