Two strongly oil-prone source intervals are present in the West Siberian Basin, the Togur Formation (Early Toarcian, Early Jurassic) and the Bazhenov Formation (Volgian-Berriasian, Late Jurassic to Early Cretaceous). Clay sediments of the Togur Formation were deposited in a system of intracontinental sub-basins in the southern half of the West Siberian Basin. The marine deposits of the Bazhenov Formation accumulated throughout the entire basin. Two types of extractable bitumens and oils -marine and non-marine -may be identified from their isotopic carbon composition, sulphur content, bulk composition, and biomarker hydrocarbons (normal alkanes, pristane/phytane, C 27-30 steranes, hopanes and homohopanes). Marine oils, accounting for 80% of oil resources, are sourced from the Bazhenov Formation. The genetic relationship between oils in Upper Jurassic and Cretaceous reservoirs and the organic matter from the Bazhenov Formation is indicated by great similarities in their biomarker hydrocarbon compositions and their maturation levels. Non-marine (lacustrine) oils are sourced from the Togur Formation and account for 11% of oil resources.
The influence of 6.75 m thick dolerite dike on the sheet coal of the Kaierkan deposit (northwestern Siberian Platform) was studied by organogeochemical methods. It is shown that initial bituminous coal was transformed into anthracite in the immediate vicinity of the dike. Chemical kinetic modeling of the dike-induced cracking of coal’s organic matter was performed, and the maximum paleotemperatures were estimated.
The White Sea being connected with the Arctic Ocean via the Barents Sea has an influence on its water temperature/salinity structures and biological processes and thus has an indirect impact on the Eurasian climate system. In this work, we have managed to find a correspondence between the climate fluctuation in the Holocene and changes in the geochemical and microfossil properties in the sediment core of the White Sea. For the first time, the element speciation in the sediment core covering about 10,000 cal yr BP period was investigated. The cooling periods (the early Holocene and the Subboreal stage) were characterized by a trend of increase in Si, Al, and Ti contents and Ti/Al ratios, which reflect lithogenous contribution, and decrease in geochemically labile forms of trace elements. A significant increase in the content of organic-bound trace elements and biogenic components (Сorg, BSi, and chlorin) was observed during periods of Holocene climatic optimums. The evident relationship between the metal speciation and indicators of the sedimentation paleoenvironment is observed at the stage of the active phase of early diagenesis after the slowing down of the biogeochemical processes. Down-core decrease in the Mn oxyhydroxide content exhibited a weakening of diagenesis processes at the ~130–150 cm depth.
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