Depositional environment of the Middle- and Upper-Holocene sediments in the North-West of the Bol’shezemel’skaya tundra (in the Kuya river valley)

• Published in: Litosfera (Ekaterinburg. Online) Vol. 24; no. 6; pp. 986 - 1013
• Main Authors: Golubeva, Yu. V., Marchenko-Vagapova, T. I., Isakov, V. A.
• Format: Journal Article
• Language: English
• Published: 15.01.2025
• ISSN: 1681-9004; 2500-302X
• DOI: 10.24930/2500-302X-2024-24-6-986-1013

Research subject. The Holocene alluvium, lake-bog and oxbow-lake sediments in the lower reaches of the Kuya river valley, the right tributary of the Pechora river (Nenets Autonomous Okrug, northwest of the Bol`shezemel`skaya tundra). Aim. Investigation of the morphological types of fluvial formations, their lithostratigraphic subdivision, and reconstruction of the environmental conditions of sedimentation. Materials and methods. The sediments texture and structure features of the floodplain-channel complex were studied by granulometric and mineralogical analyses. The morphostructural features of the relief were identified by high-resolution satellite imagery and an ArcticDEM digital relief model. The spore-pollen and diatom analyses and radiocarbon dating results are presented. Results. The lithotypes of Holocene sediments that make up the valley in the lower reaches of the Kuya River are distinguished, and the chronology of paleogeographic events in the study area is presented. A geological and geomorphological scheme of the floodplain-channel complex of the Kuya River valley is constructed. The geological profile of alluvium and underlying sediments is constructed. Reconstructions of vegetation and climate dynamics in the mid- and late-Holocene based on the palynostratigraphic subdivision of alluvium sediments is carried out. The lower boundary of the late Sub-Atlantic period, correlated with the Little Ice Age, is clarified. Conclusions. The formation of the floodplain-channel complex occurred in four stages, with its constituent deposits being attributed to the channel, lacustrine, bog, and floodplain facies. According to morphometric features in the geomorphological structure of the river valley, an erosion-accumulative relief of the above-floodplain terraces of high and low floodplains is identified. The following stages of vegetation changes are traced: from tundra communities in the coldest conditions of the early Subboreal, which were replaced by forests of the middle taiga type to the Subboreal thermal maximum, dated 3360 ± 70 years ago (3602 cal. BP) to modern forest-tundra and south-tundra communities. The formation fluvial plain sediments occurred in shallow, slightly mineralized, and waterlogged reservoirs.