Palynological diagrams of Holocene sediments and ice wedges at the mouth of the Seyakha River (Zelenaya), Yamal Peninsula

Abstract

This article examines the sections of the high floodplain of the Seyakha River (Zelenaya) and sections of Holocene peat layers with ice wedges on the third terrace. Palynospectra from sediments and ice wedges of the high floodplain are characterized by a rhythmic fluctuations typical to floodplain facies. The presence of spruce pollen is related to resedimentation, since spruce pollen is detected in the samples with the composition of verifiably resedimented palynomorphs around 10% or higher. The change in composition of the pollen of Siberian pine, scots pine, and birch tree is associated with a change in wind drift, since fluctuations in the composition of the pollen of these taxonomic units do not correlate with fluctuations in resedimented palynomorphs. Therefore, the three periods of increased wind drift and possible increase in pollen productivity can be determined based on mid-period contrast changes in the structure of palynospectra. At the same time, the local peak of cereals is replaced three times by the maximum pollen of dwarf birch and alder. The absence of larch trunks can be substantiated by fires, the traces of which are observed in the section, as well as that larch at the northern limit of its habitat has crumbly wood tissue, which is being rapidly destroyed. Tree limb, needles, and cones usually remain, while the wood tissue is absent. It is assumed that ice wedges formed here 8.5-6 thousand years ago during a single cycle of the change in wind direction and speed , when prevalence of birch tree pollen with some alder pollen at a relatively low pollen concentration was replaced by the dominance of gramineae pollen, and then, dwarf birch pollen in the spring pollen rain. Palynospectra of these ice wedges indicates an increase in the sum of positive temperatures from 8.3 to 6 thousand years.