Geochemistry of Alkylbenzenes, Alkyltoluenes, and 2-Methyl-2-(4,8,12-Trimethyltridecyl) Chromans in the Lower Permian Salt Sequence of the Upper Pechora Salt Basin

The composition and distribution of alkylbenzenes, alkyltoluenes, and 2-methyl-2-(4,8,12-trimethyltridecyl)chromans (MTTC) in the aromatic hydrocarbon fraction isolated from the Lower Permian silty-clayey and salt rocks of the Upper Pechora potassium–magnesium salt basin (Yakshinskoe deposit) are pr...

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Bibliographic Details
Published in:Geochemistry international 2021-10, Vol.59 (10), p.947-958
Main Authors: Shanina, S. N., Burdelnaya, N. S., Bushnev, D. A., Valyaeva, O. V., Ignatovich, O. O.
Format: Article
Language:English
Subjects:
Algae
Alkylbenzenes
Archaea
Aromatic compounds
Aromatic hydrocarbons
Deposition
Distribution
Earth and Environmental Science
Earth Sciences
Evaporites
Fresh water
Freshwater
Geochemistry
Halite
Halites
Halophilic archaea
Inland water environment
Low concentrations
Magnesium
Organic matter
Permian
Phytoplankton
Potassium
Rock
Rock-salt
Rocks
Salt
Salts
Sylvite
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Summary:The composition and distribution of alkylbenzenes, alkyltoluenes, and 2-methyl-2-(4,8,12-trimethyltridecyl)chromans (MTTC) in the aromatic hydrocarbon fraction isolated from the Lower Permian silty-clayey and salt rocks of the Upper Pechora potassium–magnesium salt basin (Yakshinskoe deposit) are presented. The studies have shown the wide distribution of alkylbenzenes and alkyltoluenes under hypersaline environment (stages of the halite and sylvite precipitation) at low organic matter maturity. The revealed differences in n -alkylbenzenes and n -alkyltoluene distributions are associated with the predominance of various biological precursors (halophilic archaea, prasinophytes, planktonic algae, etc.) during the salt deposition of the Upper Pechora Basin. Our data confirmed the predominance of hexadecylbenzene (C 22 ) among n -alkylbenzenzenes under hypersaline environments. The presence of phytanylbenzene and phytanyltoluene was established in the rocks of the Upper Pechora salt basin. It was found that the maximum content of phytanylbenzene is correlated with elevated contents of phytane and hexadecylbenzene, which suggests their common source and allows us to consider these compounds as indicators of paleohypersalinity. The abundance of 5,7,8-trimethyl-MTTC at low concentrations of mono- and dimethyl-MTTC indicates significant input of fresh water into the evaporite basin during the deposition of the underlying rock salt horizon.
ISSN:0016-7029
1556-1968
DOI:10.1134/S0016702921090056