TUSTAN – NEW SECTION OF TERRACE DEPOSITS IN THE DNIESTER VALLEY

Abstract

The current scope of knowledge of individual fragments of the Dniester valley was analyzed, and it was found thatits pre-Carpathian part remains the least studied. The diagrams illustrating the idea of the structure and history of the formation of this river valleyfragment are mainly based on the diagram by I. Hofshtein developed in the 1960–1970s and coincide with it in terms of boththe number of terraces discovered here and the determination of their age. In recent years, significant progress has been made in the study of the pre-Carpathian fragment of the river valley, in particular in the study of the ancient terraces of the Dniester River, which until now have been "hidden" in the leveling surfaces of Loyeva and Krasna. Low-Upper Pleistocene terraces, which are spread mainly within the borders of the Upper Dniester, Stryi-Zhydachiv, Halytsia-Bukachiv basins and within the 5–10-kilometer sections of the Dniester valley and the valleys of its separate Carpathian tributaries located at the foot of the Carpathian escarpment, remain less studied. Until recently, the youngest of the Pleistocene terraces of the Dniester River was considered to be the Kolodiyiv terrace, the loose accumulations of which are based on alluvium of the Horohiv (Prylutskyi) period. Below it, the first supraflood terrace of Late Pleistocene-Holocene age is developed. On the basis of the analysis of the morphological parameters of the terrace developed within the Halytsia-Bukachiv basin, the analysis of the cross-section of its loose accumulations, a terrace was identified that corresponds to the second supraflood terrace of the Vytachiv-Buzka period, developed in Middle Transnistria. As a result of the identification of the terrace, which we consider as the second supraflood, as well as the terraces discovered within the distribution of the Loyeva and Krasnaya leveling surfaces, the total number of terraces developed in the pre-Carpathian part of the valleys and the Dniester reached twelve: the late Pleistocene-Holocene first floodplain terrace; late Pleistocene second (Tustan) and third (Kolodiiv) floodplain terraces; Middle Pleistocene fourth (Jezupil) and fifth (Maryyampil) floodplain terraces; early Pleistocene sixth (Halytsky), seventh (Biskovytsky), eighth (Susidovytsky), ninth (Dubrivsky), and tenth (Torganovytsky) supraflood terraces; Pliocene (?) eleventh (Starosilska) and twelfth (Krasnianska) supraflood terraces. Key words: terrace; morphology; Dniester valley; loess; alluvium; stratigraphic horizons.