Features of the coarse clasts (psephites) distribution in the Upper Quaternary sediments of the northern Barents Sea

Abstract

The paper presents the characteristics of the coarse clasts (psephites, larger than 1 cm) sampled in the northern part of the Franz Victoria Trough (Barents Sea) during the “Transarktika-2019” expedition. The studied sedimentary section was formed during the transition from the last deglaciation environments to the marine Holocene settings. The amount of psephites in deglacial sediments is much higher than the one in Holocene sediments. The petrographic composition of the psephites, their roundness (according to Waddell and Khabakov classifications) and shape (according to Zingg classification) were studied in detail. It is shown that the majority of psephites is represented by non-rounded or poorly rounded varieties. Isometric and disc-type shapes are predominating among coarse clasts. Isometric psephites prevail in “deglacial sediments”, while disc-shaped, bladed, and rodlike, as a rule, are current in marine Holocene sediments. The petrographic composition of psephites is mostly represented with carbonate (limestone and dolomite) and sandstones. The amount of carbonates increases from the Holocene to the deglacial part of the sediment section. Other rocks found in smaller quantities are represented by quartzites, cherts, shales, basalts, crystalline schists, gneisses, granites, pyrite. During the last deglaciation at the Late Pleistocene the iceberg rafting was the main mechanism of psephites delivery to the sampling points. The major sources of the icebergs were Franz Josef Land and the Belyi — Victoria Islands region. Rocks of Franz Josef Land are represented mainly by Cretaceous gabbro-basalt complex and Triassic sandstones and siltstones. Upper Paleozoic terrigenous and carbonate rocks, as well as Proterozoic metamorphites, occur in the west of the studied area (the area of the Belyi — Victoria Islands). The results of studying the petrographic composition of psephites allow us to conclude that during the last deglaciation icebergs from both sources were heading north towards the Nansen Basin through the Franz Victoria Trough. Both streams of icebergs failed to reach the opposite sides of the Franz Victoria Trough, mixing with each other approximately in the axial part of the trough and leaving it in northern directions.