Journal of Siberian Federal University. Biology / On the Composition of a “Pink Horizon” in Varved Clays of the Onega Ice Lake

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Issue
Journal of Siberian Federal University. Biology. 2025 18 (3)
Authors
Golyeva, Alexandra A.; Subetto, Dmitry A.; Mergelov, Nikita S.; Orlov, Alexander V.; Dzini, Stefania; Khokhlov, Nikita V.
Contact information
Golyeva, Alexandra A.: Institute of Geography RAS Moscow, Russian Federation; ORCID: 0000-0002-1162-3321; Subetto, Dmitry A.: Herzen State Pedagogical University of Russia Saint Petersburg, Russian Federation; ; ORCID: 0000-0002-3585-8598; Mergelov, Nikita S.: Institute of Geography RAS Moscow, Russian Federation; ORCID: 0000-0001-5796-5960; Orlov, Alexander V. : Herzen State Pedagogical University of Russia Saint Petersburg, Russian Federation; ORCID: 0000-0001-9726-0471; Dzini, Stefania: Miklouho-Maclay Institute of Ethnology and Anthropology RAS Moscow, Russian Federation; ORCID: 0000-0002-7288-9422; Khokhlov, Nikita V. : Miklouho-Maclay Institute of Ethnology and Anthropology RAS Moscow, Russian Federation
Keywords
iron; scanning electron microscope; Raman spectra; microanalyzer; microbial mats; varved clays; “pink horizon”; Onega Ice Lake
Abstract

The present study reports results of the microscopic and geochemical examination of the structure and composition of the “pink horizon” in varved clays of the Onega Ice Lake. This is a stratigraphically consistent marking horizon extending across the entire area of the Onega Ice Lake waters, which is dated to approximately 13,300–13,200 calibrated years ago. The origin and the structure of this horizon remain a matter of debate. The research was conducted on Lake Polevskoye, at the Zaonezhsky Peninsula, which is located in the Republic of Karelia. From the sediment core N 125, 18 samples were collected at 0.5 cm intervals for analysis (depth 9.64–9.84 m – “pink horizon” in varved clays of the Onega Ice Lake). A JEOL 6610LV scanning electron microscope (SEM) and an INCAx- act (MAn) microanalyzer were used. Raman spectra were acquired directly from the Fe- containing particles and films on a Renishaw inVia Reflex microspectrometer equipped with 532 nm and 785 nm lasers using a 50x objective with 0.5 numerical aperture. Data collection time ranged from 10 to 180 sec per measurement. For black C-rich particles, we used a 532 nm laser set to 5–10 mW power and 10 sec of acquisition time. A large amount of iron was found in the form of small crystals and amorphous films on the surface of various particles. The presence of biogenic structures within the samples exclusively in the form of microbial mats and biofilms suggests relatively rapid sedimentation and accumulation processes. Microbial mats and biofilms may develop in deep water even at a depth of 100 m and deeper. In deep- water environments, the composition of the microbial community may change, with photoautotrophs being replaced by chemoautotrophs. A conclusion has been made about the high rate of accumulation of varved clays. The current study shows that the “pink horizon” has internal heterogeneity (fine layering), which averages the obtained geochemical spectra and makes it impossible to distinguish concentrations of individual elements

Pages
272–284
EDN
QPCWSQ
Paper at repository of SibFU
https://elib.sfu-kras.ru/handle/2311/157485

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