Geochemical basis of climate change indication in the Holocene sediments of Lake Bannoe (Southern Urals, Russia)

Abstract

The study aims to investigate the geochemical characteristics of lake sediments in order to identify geochemical proxies that reflect climatic changes during lacustrine sedimentation. Finding and substantiating such geochemical indicators is relevant for lake sediments that are sensitive to climatic variations. The paper presents the results of the analysis of the suitability of the chemical variability index CIA for detecting climate changes in the sediments of Lake Bannoe (Southern Urals) during the Holocene. The radiocarbon dating showed that the lake age is ~ 13 ka cal. The data on the elemental composition of the 5-m core of lake sediments were considered; the data were obtained by the X-ray fluorescence (XRF) analysis. Based on the ratio of residual, hydrolysate, and carbonate components, it was established that all measured samples belong to a single geochemical facies of siliceous clastic sediments. The analysis of the CIA relationships with indicators characterizing the provenance (Zr/Ti), grain size (Al/Si), recycling and sorting (ICV), K-metasomatism (A–CN–K diagram) made it possible to determine the suitability of the CIA indicator as a proxy for the intensity of chemical weathering and climatic variations in the lake sediments during the Holocene. The CIA values after correction for K-metasomatism are set in the range of ~ 74–82 with an average of ~ 78, thereby testifying that the climate of the studied epoch was warm and humid with a pronounced warming trend from the Preboreal stage to the Subatlantic stage. The results of the study contribute to further development of ideas about the lacustrine sedimentation in the territory of the Southern Urals.

Keywords

• indicators of chemical variability
• holocene
• lake sediments
• climate