Paleogeography and biostratigraphy of the Sea of Azov bottom sediments in the Ancient and New Azov Periods

The article summarizes the data on paleogeography, lithology, and biostratigraphy of the Ancient Azov and New Azov deposits of the Sea of Azov (6.5 kyr BP). It is shown that the Black Sea species had a great influence on the flora and fauna during the early stages of the basin formation and the biota of the Sea of Azov began to acquire specific features only 3 thousand years ago. The article describes changes in the fauna of molluscs, the flora of diatoms and pollen spectra at different time stages. Marker taxa for the Ancient and New Azov sediments from different areas of the Sea of Azov are given. Diatom analysis indicates that such species of diatoms as Paralia sulcata, Grammatophora marina, Thalassiosira eccentrica, and Chaetoceros spp. have stratigraphic significance for the Ancient Azov sediments. The New Azov sediments of the open part of the Sea of Azov are characterized by the presence of other diatoms taxa: Actinocyclus octonarius var. ralfsii, A. octonarius var. tonsure, A. pseudopodolicus, Actinoptychus senarius, Thalassiosira decipience, and Chaetoceros spp. Malacological studies indicate that the species Chamelea gallina, Gastrana fragilis, Polititapes aureus, and Loripes obriculatus may be used to distinguish the Ancient and New Azov layers in the open part of the Sea of Azov. Low taxonomic diversity, the absence of gastropods (with the exception of Hydrobia acuta) and the disappearance of Mytilus galloprovincialis shells from sediments characterize the New Azov strata of the Central Taganrog Bay. The results of the spore-pollen analysis indicate that the boundary of the Ancient and New Azov sediments can be identified only by the appearance of pollen – indicators of anthropogenic activity (cultivated cereals and ruderal plants) – registered in sediments of the past 3 thousand years. The authors conclude that it is preferable to use integrated biostratigraphic data combined with the results of radiocarbon dating for the most precise stratigraphic separation of the Quaternary sediments in the Sea of Azov. 

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