Лесові покриви на терасах нижньої течії Свічі

Abstract

The Fore-Carpathians part of Svicha River valley partially covers Morshyn and Zalissia Uplands and Stryi-Zhydachiv depression. Within the Svicha and Sukil' river valleys, there are well-developed different-age terraces with thick stratified loess covers. The investigation of the last ones can help to define nomenclature and age of the terraces. The loess covers of the third (Kolodiiv) and the fourth (Mariampil) terraces, which are represented by Pidberezhzhia and Mizhrichchia sections accordingly, are characterised in detail in the article. Pidberezhzhia section represents a sequence of alluvial and covering deposits of the third (Kolodiiv) over-floodplain terrace of Svicha River, which is developed on its right bank. The terrace is stretched out in the form of a narrow (about 2 km) strip from the village Zarichchia to the village Novoselytsia. It is separated from the Svicha riverbed by the system of different-altitude floodplain levels and the first and second over-floodplain terraces. The boundaries between them are morphologically distinct, the exceeding of the surface of the Kolodiiv terrace above the water level in the riverbed of Svicha reaches 10 m or even more. Covering loess-soil series on the terrace has a capacity of more than 6 m and begins with the Horokhiv fossil soil complex. Mizhrichchia section represents the fourth (Mariampil) over-floodplain terrace, which to the north of Mizhrichchia village forms a scarp to the riverbed of the Svicha River, about 20 m in height. The terrace on this part of the valley of the river covers small areas and it is developed between the villages of Zarichchia and Mali Didushychi. Almost along its length, the terrace directly scarps to the riverbed. On the opposite side, where the rear seam is, it borders on the fifth (Galician) over-floodplain terrace, which forms a scarp about 10 m in height. Loess cover on the fourth terrace is up to 14 m thick. There are welldeveloped Dubno fossil soil (MIS 3) and Horokhiv fossil soil complex (MIS 5) and a thick sequence of hydromorphic deposits, which obviously correspond to the Korshiv fossil soil complex (MIS 7) in loesspaleosol series. The studied Pleistocene covers allow us to reliably identify Mariampil and Kolodiiv terraces of the Svicha River, as well as outline the nomenclature of the remaining terraces of the adjacent sections of the Zalissia and Morshyn Uplands and Stryi-Zhydachiv depression. Key words: river terrace, loess-soil covers, Dubno fossil soil, Horokhiv and Korshiv fossil soil complexes, Fore-Carpathians, Zalissia and Morshyn Uplands.