The patterns and history of Mesozoic-Cenozoic plume magmatism in the Arctic are considered in relation with suprasubductional volcanism and geodynamic events. The Mesozoic-Cenozoic magmatic history of the area includes seven stages, distinguished by correlation of ages and compositions of volcanics associated with mid-ocean rifting, plumes, and subduction; three of seven stages correspond to global events at 230-200 Ma, 130-120 Ma, and 40-30 Ma. The reported study supports the inferred inverse correlation between plate velocities and amount of subduction-related volcanism. The gained knowledge is used for paleotectonic reconstructions.
The Late Paleozoic and Mesozoic history of petroleum and coal basins in the Arctic and adjacent areas is investigated and compared with the history of plume magmatism in the same areas. The sedimentation rates in all discussed cases are proven to be the fastest (more than 100 m per 1 Myr) during rifting events. Other peaks of rapid deposition may be associated with collisional mountain growth and/or climate change.
Chromato-mass-spectrometric studies made it possible to identify a wide spectrum of hydrocarbon biomarkers in crude oils from Cenomanian pools of northern West Siberia (Russkoe, Pangodinskoe, Van-Eganskoe, Severo-Komsomol’skoe). The distribution pattern of the main hydrocarbon components ( n -alkanes, acyclic isoprenanes, steranes, terpanes) shows that most of the oils underwent intense microbial oxidation. We have established high concentrations of 25-norhopanes typical of high-degree degradation; demethylated hopanes are also revealed in “alkane” crude oils. Among low-molecular chemofossils, biand tricyclic monoand sesquiterpanes have been recognized, whose precursors are usually biomolecules synthesized by plants. Unsaturated precursors of monoand sesquiterpanes might have been the starting material for thermocatalytical synthesis of framework adamantanoid structures, whose high concentrations have been found in alkane-free crude oils.
We present results of geochemical studies of organic matter of the Jurassic–Cretaceous deposits in the west of the Yenisei–Khatanga regional trough. The studies were carried out on a representative set of well cores by a complex of modern organic-geochemistry methods (determination of organic-carbon content in rocks, pyrolysis, estimation of the carbon isotope composition in the kerogen of rocks, extraction, liquid and gas–liquid chromatography, and chromato-mass spectrometry). Based on the distribution of biomarkers in the studied bitumens and pyrolysis of rocks, two groups of the samples were recognized: with terrigenous (type III) and marine (type II) organic matter. The terrigenous bitumens are characterized by a low hydrogen index (HI) and a predominance of hydrocarbons C29 among steranes and C19 and C20 among tricyclanes. The marine bitumens, revealed in stratigraphic analogs of the Bazhenovo Formation and in the Malyshevka, Nizhnyaya Kheta, and Shuratovka Formations, show an even distribution of sterane homologues and a predominance of medium-molecular tricyclanes. The Pr/Ph and C35/C34 ratios and the presence of diahopanes testify to the burial of organic matter in suboxidizing sea coast environments. In the Yanov Stan (J3–K1), Gol’chikha (J2–K1), and, to a lesser extent, Malyshevka (J2), Nizhnyaya Kheta, and Shuratovka (K1) Formations, we have recognized widespread stratigraphic levels with marine organic matter of rocks. Its contents and degree of maturity permit these rocks to be considered oil-generating.
Much work at A.A. Trofimuk Institute of Petroleum Geology and Geophysics (Novosibirsk) has been done to synthesize geological and geophysical data from the Siberian Arctic and Arctic shelf. Namely, seismic-geological modeling and petroleum potential assessment have been performed for the Neoproterozoic–Phanerozoic section of the Anabar–Lena province in the northern Sakha Republic (Yakutia). The results include seismic-geological division, a set of structural maps, and structural, paleotectonic, and facies analysis. The study shows that Riphean, Vendian, Cambrian, and Permian sequences are of interest in terms of petroleum potential; oil and gas may accumulate in traps of different types.
Formation of the passive continental margin of the Laptev Sea (Laptev Plate), which was part of the Siberian Platform till the Late Cretaceous, was related to the Late Mesozoic–Cenozoic rifting of the Arctic geodepression. The regime of the passive continental margin still continues. The maximum thickness of the deposits of this age seems to exceed 6 km in the northeastern part of the shelf. The hydrocarbon resources of the Late Precambrian–Cenozoic deposits forming the Laptev Plate cover are evaluated. Based on the concept of the similar evolution of the Laptev Plate and Vilyui syneclise, the geochemical characteristics of dispersed organic matter of the coeval deposits of the Vilyui syneclise are used.
The rate of decomposition of vegetable residues in embryonic soils characterized by the stage of post-technogenius soil formation is considered. Syngenesicity and vicissitude of the process of mineralization and losses of organic matter in the soils under study are demonstrated.
The soil cover of man-made landscapes of the Kuznetsk basin is described. It is established that the basis of the soil cover of man-made landscapes is composed of four types of embryonic soils. The specificity of formation of the embryonic soils is determined by the peculiarities of development of biological processes. It is demonstrated that the rate of development of biogeocenoses is controlled by the environmental conditions which are formed during the technogenesis stage. Therein, considered as the ecologically most important element of technogenesis must be the rock formation, i.e. the man-caused lithogenesis.
The work is dedicated to the problems of rational ecologically safe use of chernozems - the main automorphous type of irrigated soils in the forest-steppe and steppe zones of West Siberia. For the main provinces of the region, theoretically and experimentally substantiated are the most important elements of soil humidification, and on this basis soil protection regimes of irrigation are developed.
