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Structure of the Triassic Deposits of the Peschanomys–Rakushka Oil and Gas Accumulation Zone
Folding-thrust dislocations formed under the influence of lateral compression forces are quite widely represented in the sedimentary cover of the Scythian-Turanian plate. Horizontal tectonic movements are usually accompanied by lateral displacement of individual blocks of the Earth’s crust separated by strike-slip faults. In contrast to thrust dislocations, information about the presence of strike-slip faults for the Scythian-Turanian plate is extremely limited. This problem is considered on the example of dislocations of Triassic sediments of the Peschanomyssk–Rakushechnaya uplift zone of the South Mangyshlak trough. A detailed lithological and stratigraphic analysis of sections of Triassic sediments exposed by deep wells within this zone was carried out. Characteristic lithological strata were identified and their stratigraphic binding was performed. The shifting nature of regional basement faults was established. Many of them were active in the following periods, characteristic shear deformations were formed in the sedimentary cover as a result of this activity. Morphological features of dislocations that are traps of oil and gas were established. The authors’ reconstructions are based on their comprehensive analysis of geological and geophysical materials, including data from high-precision large-scale aeromagnetic surveys, reflected wave seismic exploration, deep drilling, and remote surveys. In order to restore the history of the development of the territory as a whole and the folded-discontinuous dislocations complicating it, paleotectonic constructions were carried out. The information provided in this paper on this problem allows us to take a fresh look at the geodynamic situation of the formation of platform territories, and may also contribute to solving some oil and geological problems, since oil and gas accumulations are often concentrated in areas of wrench faults.
Astroblemes as indicators of the Holocene activation onset
The article continues the author’s series of publications on global Holocene activation. The research was carried out on the interface between geology and meteoritics within the context of the Earth pulsating expansion model, whereby the Earth began to evolve in a compression mode in the late Pleistocene. At the Pleistocene – Holocene boundary, the Earth was subjected to a massive pummeling of large asteroids and changed its orbit, moving closer to the Sun. From this time on, the compression increased sharply, crustal processes intensified causing an upsurge of continental orogeny, and global transgression intensified. Astroblemes are considered as constituents of the host geological systems. They are indicators of the onset of the Holocene activation. Evidence is presented of most of the known astroblemes being formed at the Pleistocene – Holocene boundary by a single stream of asteroids. Using astroblemes in South Africa and Eurasia as examples, their relationships were studied with Holocene orogenic systems – with their tectonics, volcanism, fluid dynamics, and drainage network. The global Holocene activation is shown to significantly change the natural environment, thereby triggering an unprecedented explosion in the development of human civilization.
On the influence of Holocene tectonics on the formation of the river network of the Alpine-Himalayan and Pacific mobile belts of Eurasia
This article continues the series of publications on the indicators of Holocene activation. Using the examples of the Volga and Amur rivers with their tributaries and the Razdolnaya River, the interaction of the river network with the Holocene orogenic system of the Alpine–Himalayan and Pacific mobile belts of Eurasia was studied. The river network is conformal to their orogenic system. Examples of the control of river valleys by shear systems of active faults are given. The influence of the rivers on the formation of erosional relief was studied. It is shown that loose sediments of the Mesozoic-Cenozoic rifts thrown up in the Holocene are actively destroyed by the river network, with a shear of up to many hundreds of meters. The rises on the riftogen framing and their internal rises, composed of strong pre-Mesozoic rocks, are weakly eroded. Many of them have a contrasting, nonequilibrium relief. The study was conducted within the framework of the pulsatingly expanding Earth model developed by the author.
Geological and geophysical model of the central part of the Yenisei–Khatanga regional trough based on the results of comprehensive interpretationof modern seismic and gravity-magnetic surveys
New data on potential fields are presented, compared with previous ideas about the regional structure and rift genesis of the Yenisei-Khatanga regional depression basement. Our 2D modeling based on geophysical data confirms the results of previous works regarding the identification of two types of the basement, and is consistent with the gravity-geodynamic concept of the formation of the Yenisei-Khatanga regional trough and the tectonic structures that complicate it, such as the Rassokhinsky and Balakhna megaridges. Also, as a result of our study of potential fields, the presence of a large volume of magmatic masses of ultrabasic and basic composition in the axial part of the Yenisei-Khatanga regional trough, Permian-Triassic age, was established, which confirms the rift mode of the region's development.
Thermal history of the permafrost formation in the sedimentary section of the Tyumen superdeep SG-6 well
The thermal evolution of the permafrost in the sedimentary section of the Tyumen superdeep SG-6 well has been numerically reconstructed using the ICE2020 software package, which is part of the GALO flat basin modeling system. The thermal evolution of the sedimentary strata in the last 3.5 My is considered as the final stage of the basin modeling, whose formation began with continental rifting in the Late Permian. Abrupt climate changes in the late Pliocene–Holocene led to a decrease in the rock temperature by 15–20°C in the upper 1–1.5 km of the SG-6 sedimentary section. The maximum thickness of the permafrost in the study area was about 711 m, reached 2.6 Mya. The maximum thickness of the permafrost for the last ice age (23–18 thous and years ago) was 412 m, reached about 14.5 thousand years ago. According to our modeling, the modern base of the permafrost is at the depth of 311 m and is degrading with the rate about 13 m/1000 y. The results of our calculations with a database of climatic data limited to the last 50 and 100 thousand years differ markedly from the modeling results with the complete database for the last 3.5 My.
Physical modeling of the formation conditions of marginal plateaux on the example of structures in the North Atlantic Ocean
Peculiarities of the formation of marginal plateaus in the early period of the opening of the North Atlantic Ocean are considered. The oceanic opening between Greenland and Europe (formation of the North Atlantic Ocean) began approx. 50–55 Mya after a long period of rifting, followed by the formation of the Aegir spreading ridge and the formation of the basin of the Norwegian Deep. Since that moment, the formation of a series of specific structures (marginal plateaus) began. The article considers conditions for their formation, using the physical modeling method. Three groups of structures were distinguished and typified according to the formation mechanism. A series of experiments was performed to each type of structures. Experimental results are compared with our proposed model for the formation and evolution of marginal plateaux.
Formation of the sedimentary cover of the South Kara basin
A scheme of formation of the sedimentary blanket of the South Kara basin is considered, which can further be used for numerical reconstruction of its thermal history. The scheme is based on our analysis of the literature information on the structure and geological history of the Barents-Kara region. This information included an interpreted seismic profile crossing the studied area, drilling data from four wells located along the profile (the University, Rusanov, Leningrad and Kharasavey ones), measurements of the heat flow and deep temperatures in the basin. The proposed scheme considers the formation of the basin as a series of sedimentation stages with various combinations of clay shales, siltstones and sandstones and sedimentation in the Cretaceous and Paleogene with their subsequent erosion in the Miocene. The erosion amplitude is estimated by the observed change in the porosity of sedimentary rocks with depth. The initial heat flow in such a model should correspond to the flow of modern axial zones of continental rifting or be lower for the areas remote from the corresponding segments of the Late Permian-Early Triassic continental rifting system.