THE ASSOCIATION OF BENTHIC MACROBIOTA OF THE LATE EDIACARAN OF PODILLIA IN THE DEPOSITS OF THE MOHYLIV-PODILSKYI GROUP IN THE QUARRY NEAR THE DNIESTER HPP

Abstract

The maximum level of Ediacaran-type biota diversity in the Volyn-Podilskyi sedimentation basin existed in the time interval that corresponds to the Lomoziv and Yampil Members of the Mohyliv Formation. Studies of the isotopic age showed that this period ended 557 million years ago. Environmental conditions that prevented the existence of classical Ediacaran biota prevailed during the accumulation of the Lyadova Member. A less numerous biotic association of the transitional type with individual representatives of the Ediacara-type association is observed in the deposits of the Bernashivka Member. Paleoecological conditions in the sedimentation basin were reconstructed on the basis of the study of the section in the quarry near the Dniester HPP. More than a thousand specimens of fossils of soft-bodied organisms and tracefossils were collected there. More than three dozen species were discovered in Podilla for the first time. The study of a significant number of new species continues. It was established that the biotic association of the Mohyliv Formation was dominated by problematic frondomorphic and spherical organisms, which sometimes reached significant sizes.The existence of probable ancestors of several groups of biota of the Phanerozoic type:Cnidaria, Porifera, Lophotrochozoa, Mollusca and Metaphita were found in the Late Ediacaran shallow water ecosystem. Thefossil remains of the earliest probable members of the phylum Chordata of the subphylum Tunicata are collected here. These arethe most likely ancestors of vertebrates according to data from several research groups. It was established that some Ediacaran organisms used life strategies typical for representatives of later biota: combinations of different types of reproduction, activeresponse to external environmental factors, etc. New methods of fossil research were proposed and important results were obtained in the process of their use. It was established that quite sharp changes in the taxonomic composition of biotic associations in the section of sediments are caused by facies conditions and evolutionary processes. This makes it possible to use the fossilized remains of the Ediacaran biota for the needs of biostratigraphy and correlation with the same age deposits in other regions.