Mg-Rich Authigenic Carbonates in Coastal Facies of the Vtoroe Zasechnoe Lake (Southwest Siberia): First Assessment and Possible Mechanisms of Formation

Abstract

The formation of Mg-rich carbonates in continental lakes throughout the world is highly relevant to irreversible CO2 sequestration and the reconstruction of paleo-sedimentary environments. Here, preliminary results on Mg-rich carbonate formation at the coastal zone of Lake Vtoroe Zasechnoe, representing the Setovskiye group of water bodies located in the forest-steppe zone of Southwest Western Siberia, are reported. The Setovskiye lakes are Cl−–Na+–(SO42−) type, alkaline, and medium or highly saline. The results of microscopic and mineralogical studies of microbialites from shallow coastal waters of Lake Vtoroe Zasechnoe demonstrated that Mg in the studied lake was precipitated in the form of hydrous Mg carbonates, which occur as radially divergent crystals that form clusters in a dumbbell or star shape. It is possible that hydrous Mg carbonate forms due to the mineralization of exopolymeric substances (EPS) around bacterial cells within the algal mats. Therefore, the Vtoroe Zasechnoe Lake represents a rare case of Mg-carbonates formation under contemporary lacustrine conditions. Further research on this, as well as other lakes of Setovskiye group, is needed for a better understanding of the possible role of biomineralization and abiotic mechanisms, such as winter freezing and solute concentration, in the formation of authigenic Mg carbonate in modern aquatic environments.

Semiarid Lakes of Southwestern Siberia as Sentinels of On-Going Climate Change: Hydrochemistry, the Carbon Cycle, and Modern Carbonate Mineral Formation

“…In total, 43 samples of water and 36 samples of sediments collected during fieldwork periods of 2018-2019 were analyzed in this study (Figure 1, Tables A1 and A2). Sampling field campaigns were mainly conducted in summer and autumn periods corresponding to summer baseflow of the region, which is the main period of authigenic carbonate mineral formation [27,28]. One of the lakes (Zolotoye) was studied in early spring.…”

“…The hydrochemical features and sedimentation processes in water bodies of the Trans-Urals and the Ishim plain are much better studied compared to the Barabinsk lowland and the Kulunda plain, though they occupy a significant part of the semiarid part of Western Siberia. Only a few studies were devoted to assessing the composition of waters and bottom sediments of these geomorphological regions with a focus on water bodies, where the formation of authigenic Mg and Mg-Ca carbonates occurs [26][27][28].…”

Micromorphological and mineralogical features of saline playa surface sediments from two large Trans-Uralian lakes

“…Undrained lakes and forest-steppe bogs occupy local depressions. The covering deposits are represented by Late Quaternary carbonaceous loess-like loams, which are underlain by Neogene and Oligocene continental sediments (Novoselov et al, 2019). The climate of the territory is continental, typical for the forest-steppe subzone of the Southern Urals, with low precipitation, hot summer and cold winter seasons.…”