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DISTRIBUTION NATURE OF MACRO- AND MICROELEMENTS IN ORGANIC RESIDUES FROM MESOZOIC REMAINS OF WEST AND CENTRAL SIBERIA

O. N. Zlobina 1,2, E. A. Predtechenskaya 2

Features of biomineralization, fossilization and distribution of chemical elements were revealed in remains of various groups of organisms, and relationship with conditions of accumulation and post-sedimentation transformations of deposits of the Middle–Upper Jurassic and Lower Cretaceous of Siberia was determined. Plates of coccolithophorids, skeletons of radiolaria and acantharia, fragments of hetetoidea frameworks, relics of red algaes, diatoms and/or cyanobacteria were studied among the remains of organisms. The composition of coccoliths from various types of rocks includes essential (calcite, ankerite, siderite) and complementary (silica and hydroxyapatite) components. It is assumed that coccolithophorids could use Fe, Mg and Mn in the form of organomineral compounds in the construction of shells, the remnants of which, after accumulation, formed deposits of the appropriate composition. The absence of pyritized coccolithophorid relics was noted in the studied sections, while the siliceous remains of radiolaria buried with them are often fossilized with FeS2. It is considered that secondary mineralization was preceded by partial or complete bacterial dissolution of siliceous skeletal fragments and some terrigenous grains.S ubsequent pyritization developed due to the vital activity of sulfate reducing bacteria. As a result, there was a transformation of the intracellular content of radiolaria and membrane complexes separating it from the elements of the mineral skeleton. The possibility of preserving acantharia relics in a fossil state was proved.

Keywords: biomineralization, fossilization, elemental composition, Mesozoic deposits, Siberia.

DOI 10.20403/2078-0575-2024-3-31-48

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