Vol 71, No 2 (2016)
- Year: 2016
- Articles: 10
- URL: https://journals.rcsi.science/0145-8752/issue/view/10647
Article
The influence of geodynamic factors on the lithification of sedimentary deposits in the stratisphere
Abstract
The peculiarities of the processes of postsedimentary lithification and their dynamics in various geostructural areas (cratons, young platforms, and orogens) are considered. The direct and indirect impacts of geodynamic factors on these processes are substantiated.
The recent structure of Mahe Island (the Seychelles archipelago)
Abstract
Complex studies were carried out, including structural and geomorphological analyses of space images and statistical processing of their deciphering results, which revealed the blocky pattern of the recent dislocations of Mahe Island, thus defining their relationships with a jointing pattern in granite outcrops. The results were compared with the geological data and instrumental observations of modern movements.
The mineralogical, isotope (K–Ar), structural, and textural features of the Jurassic siliciclastic complex in various tectonic environments (Greater Caucasus, Chechnya, and Georgia)
Abstract
The variations in the structural, textural, mineralogical, and geochemical (isotope) features of Lower to Middle Jurassic siliciclastic sediments along the Chanty-Argun River in Mountainous Chechnya and Georgia are discussed. This profile transects areas with various types of deformed sediments, from the northern comparatively weakly deformed and altered zone, to the southern zone of intense deformation and cleavage. Southward along the profile, these alterations are accompanied by the evolution of clay mineral assemblages, as well as polytypic modifications of micas and their crystallinity index. Increasing intensity of rock alteration and cleavage leads to a change of the K–Ar system, which results in a substantially rejuvenated isotope age of the sediments with a simultaneous increase of their stratigraphic age.
The structure of the Tuapse shear zone according to the field tectonophysical data
Abstract
The results of field structural studies of the Tuapse shear zone in the Northwest Caucasus are presented. This zone is characterized by shear displacements of various scales with a dominant horizontal shear, viz., a geodynamic type of the stress state, which leads to the formation of faults with mostly lateral displacement of wings, i.e., along the strike of the fault surface. The quantitative characteristics of the local stress conditions in the shear zone (the positions of principal axes and the Lode–Nadai coefficient) are determined on the basis of cataclastic analysis and geological indicators of the paleostresses. The differences between these characteristics are considered for the large tectonic zones. Significant spatial (areal) variations in orientations of the axes of major normal stresses in the shear zone and their local weak gentle variations are evidence of a consistent general stress direction during the formation of faults during the Late Eocene–Miocene deformation epoch.
The facies structure of the Vasyugan Formation deposits within the junction of the Surgut Dome and the Northern Nizhnevartovsk Megaterrace
Abstract
This paper considers the lithological peculiarities of the structure and formation conditions of the Upper Jurassic productive reservoirs in the junction zone of the Surgut Dome and the Northern Nizhnevartovsk Megaterrace in the Western Siberia Oil and Gas Basin. Based on the study of core samples and logging data we suggested a fundamentally new formation model for the U11 reservoir deposits in the Vasyugan Formation, which makes it possible to specify the major directions of further exploration.
Sedimentation control over the oil and gas contents in the cretaceous deposits of the Russkoe–Chaselka Mega-Arch (West Siberian oil and gas basin)
Abstract
Most of the hydrocarbon resources of the Russkoe–Chaselka Mega-Arch are related to the Pokur Formation reservoirs. They are generally composed of alluvial sandstones and shales. Due to their genesis the Pokur reservoirs have a complex structure and a localized spread within ancient alluvial plains. The performed integrated interpretation of the well and 3D seismic data made it possible to estimate new perspective fields and to geometrize the oil and gas deposits.
The lithological–geochemical characteristics for the Permian oil-and-gas bearing complex of the Lena-Anabar trough (based on the example of Ust’-Olenekskaya well no. 2370)
Abstract
Lithofacies of different geneses are identified in a section of Permian deposits based on the study of the core material; the best reservoirs in the Permian complex of the Lena-Anabar trough are related to the sand bodies of the delta system. The Permian oil-source strata, where organic matter was accumulated under marine conditions, are recognized, the initial characteristics of organic matter are estimated, and the initial high oil-generation potential is substantiated. The results of the lithological–geochemical studies of the samples from one of the northernmost wells in the Laptev Sea coast have been published for the first time.
The petrology of the Upper Albian tuffites from the Bakhchysarai district, southwestern Crimea
Abstract
We present the first data on the composition of plagioclase and quartz-hosted melt inclusions, plagioclase primary magmatic zoning and mineral compositions for the Upper Albian tuffites from the Bakhchysarai district. The estimated composition of the magmatic melts corresponds to the high potassium rhyolites. The measured water content in the melt inclusions reaches 4 wt %. The phenocrysts crystallized at the temperature within the range 820–860°C and under the pressure not less than 0.1 GPa. The Upper Albian tuffites from the Bakhchysarai district were formed in the active continental margin environment.
Fracturing in the high-carbon formation of the northern flank of the South-Tatar arch
Abstract
The problem of studying the Domanik deposits and their reservoir potential is among the most important ones. The discovery of hydrocarbon deposits in similar rocks at various depths, the considerable variability of reservoir properties, and ambiguity in establishing the values of the effective thickness set the task for researchers to estimate them more reliably. The high-carbon kerogenic-carbonate-siliceous stratum that is characterized by the development of differently-oriented systems of fractures is of outstanding interest.