Loess doll from Pleistocene loess-like sediments in the Vishera diamond-bearing area (Perm region)

Abstract

The purpose of the study is to investigate the cranes from loess-like deposits as indicator formations for the glacial epochs of the late Pleistocene – Holocene using current lithology methods. The motivating reason for the study was that loess-like deposits directly “seal” the industrial placer of the Silurian diamond-bearing reservoir in the Vishera diamondiferous region.Loess doll (loess pupae, dutiki) are concretions weakly cemented by iron hydroxides, consisting of quartz grains with an admixture of fine-silty feldspars. In terms of granulometry and mineral composition, the cranes correspond to the loess-like deposits that host them and are the frame of the root system of tundra-type grass vegetation. In the center of the concretion, in place of the disappeared grass root, a hollow tubule is preserved, sometimes filled with silty sand from the surrounding rocks.The granulometric composition of loess-like deposits was studied using an Analysette 22 MicroTec plus laser diffraction analyzer. Mineral composition of the heavy fraction of loess-like and underlying sediments – using quantitative mineralogical analysis. Quantitative gross mineral composition and the ratio of clay minerals in the pelitic fraction – using a D2 Phaser X-ray powder diffractometer (Bruker, Germany).The data obtained can be used for geological surveying and exploration of diamond-bearing placers in the Urals and in regions with a similar geological structure. It must be borne in mind that in the study area the described loess-like deposits do not have a direct connection with industrial placer diamond content.