Tectonic structures are large areas of the solid outer shell of the planet. They are limited to deep faults. The movements and structure of the crust are studied within the discipline of tectonics.
General information
Tectonic structures are explored using geographic mapping, geophysical methods (seismic exploration, in particular), and drilling. The study of these areas is carried out in accordance with the accepted classification. Geology explores medium and small forms, about 10 km in cross section, tectonics - large formations, over 100 km. The former are called dislocations of various types (discontinuous, injective, etc.). The second category includes synclinoria and anticlinoria in folded areas, aulacogenes, syneclises, and anteclises within plates, shields, and pericrater subsidences. This category also includes underwater passive and active continental margins, platforms, geosynclinal belts, oceans, orogens, mid-ocean ridges, rifts, etc. These are the largest tectonicstructures cover the solid shell and the lithosphere and are called deep.
Classification
Super-global oldest tectonic structures reach tens of millions of square meters. km in area and thousands of kilometers in length. They develop throughout the geological stage of the planet's history. Global tectonic structures are formations that occupy up to 10 million square meters. km. Their length reaches several thousand kilometers. The duration of their existence coincides with the previous sites. There are also subglobal tectonic structures of the earth's crust. They cover an area of several million square meters. km and stretch for thousands of kilometers. The period of their development is more than 1 billion years.
Main tectonic structures
On the basis of the unity of movement, comparative solidity, lithospheric plates are distinguished. To date, 7 largest and 11-13 smaller sites are known. The former include the Eurasian, North and South American, African, Indo-Australian, Pacific, and Antarctic tectonic structures. Smaller formations include the Philippine, Arabian, Caribbean plates, Cocos, Nasca, etc.
Rift formations
These tectonic structures separate the lithospheric plates. Among them, rifts are primarily distinguished. They are divided into continental and mid-ocean. The latter form a global system, the length of which is more than 64 thousand km. Examples of such sites are the East African(the largest on the planet), Baikal. Another type of fault formations are transform sections that cut perpendicular to rifts. Along their lines, there is a horizontal shift of sections of the lithospheric plates adjacent to them.
Platforms
They are inactive hard blocks of the bark. These areas have gone through a fairly long stage of development. The platforms are three-tiered. Their structure contains a crystalline basement, which is formed by bas alt and granite-gneiss layers. A sedimentary cover is also distinguished in the platforms. The crystalline basement is formed by layers of metamorphic rocks, crumpled into folds. All this complexly dislocated stratum is broken through by intrusions (mostly having an average and acidic composition). Depending on the age of foundation formation, the platforms are divided into young and ancient tectonic structures. The latter act as the core of the continents, occupying their central part. Younger formations are located on their periphery. The sedimentary cover contains predominantly undislocated layers of lagoonal, shelf and, in rare cases, continental sediments.
Shields and plates
These types of tectonic structures are distinguished by the specifics of the geological structure. A shield is a section of a platform on which the crystalline foundation is on the surface, that is, there is no sedimentary layer in them. In the relief, shields are represented, as a rule, by plateaus andhills. Plates are platforms or their sections, characterized by a thick sedimentary layer. Their formation is determined by tectonic subsidence and marine transgression. In the relief, plate areas usually correspond to uplands and lowlands.
Anteclise
They represent the largest positive plate formations. The surface of the foundations is convex. The sedimentary cover is not very powerful. The formation of anteclises is due to the tectonic uplift of the territory. In this regard, many of the horizons present in neighboring negative areas may not be found in them.
Arrays and ledges
They are regional anteclise structures. Arrays are represented by their higher parts. In them, the foundation is either near the surface or is overlain by Quaternary sedimentary formations. Protrusions are called parts of arrays. They are represented by elongated or isometric basement uplifts reaching 100 km in diameter. Buried protrusions are also distinguished. Above them, the sedimentary cover is presented in the form of a strongly reduced section.
Syneclise
They are the largest negative superregional plate formation structures. The surface of their foundation is concave. They are distinguished by a flat bottom, as well as very gentle dip angles of the seams on the slopes. Syneclises are formed during the tectonic subsidence of the territory. In this regard, their sedimentary cover is characterized by high thickness.
Monoclines
These tectonic structures are distinguished by one-sided inclination of the layers. Their angle of incidence rarely exceeds 1 degree. Depending on the rank of negative and positive structures, between the boundaries of which the monocline is located, its category can also be different. Of the regional formations of the sedimentary cover, grabens, horsts, and saddles are of interest. The latter occupy an intermediate position in terms of surface height. Saddles are located above the negative structures surrounding them, but below the positive ones.
Pleated areas
They are characterized by a sharp increase in the thickness of the crust. Mountain-folded areas are formed during the convergence of lithospheric areas. Most of them, especially young ones, are characterized by high seismicity. The age of formations serves as a fundamental principle for the classification of mountain-folded areas. It is installed on the youngest crumpled layers. Mountain ranges are thus divided into:
- Baikal.
- Hercynian.
- Caledonian.
- Alpine.
- Cimmerian.
This classification is considered rather arbitrary, since most scientists recognize the continuity of folding.
Pleated-blocky arrays
These formations are formed as a result of the revival of horizontal and vertical tectonic movements within the boundaries of previously formed and often already destroyed systems. In this regard, the fold-blockthe structure is more characteristic of the regions of the Paleozoic and earlier stages. The relief of the massifs, in general, is similar to the configuration of the bends of the rock layers. However, this is by no means always detected in fold-block areas. For example, in young mountains, the structures of anticlinoria correspond to ridges, and synclinoria correspond to intermountain troughs. Within the folded areas, as well as on their periphery, marginal and advanced depressions and valleys are distinguished, respectively. On the surface of these formations there are coarse clastic products that have arisen from the destruction of mountain formations - molasses. The formation of foothill troughs is the result of subduction of lithospheric areas.
Central Russia
Each large natural complex is presented as a single geostructural area of a large area. It may be a platform or a fold system of a particular geological age. Each formation has a corresponding expression in the relief. All of them differ in climatic conditions, features of soil and vegetation cover. First of all, the tectonic structure of the Urals is of interest. In its present state, it is a meganticlinorium, which consists of several anticlinoria elongated meridionally and separated by synclinoria. The latter correspond to longitudinal valleys, the former to ridges. The key Ur altau anticlinorium runs through the entire formation. According to the composition of the Riphean deposits, it can be concluded that during the period of their accumulation, intensive subsidence took place. At the same time, it was repeatedly replaced by short-term uplifts. Towards the end of the RipheanBaikal folding appeared. Uplifts began and intensified in the Cambrian. During this period, almost the entire territory turned into dry land. This is indicated by a very limited distribution of deposits, which are represented by green shales of the Lower Cambrian formation, marbles and quartzites. The tectonic structure of the Urals in the lower tier, thus, completed its formation with the Baikal folding. As a result of it, areas were formed that differed from those that arose at a later time. They are continued by the formations of the basement of the Timan-Pechora margin within the East European platform.
Siberian tectonic structure: Aldan Highlands
Formations in this area are composed of prehistoric gneisses and Proterozoic shales. They belong to the Precambrian Siberian platform. However, it is necessary to say about some features that the tectonic structure has. The Aldan Highlands developed during the Meso-Cenozoic history between the southern Northern Baikal areas and the platform. In many areas, the crystalline basement rocks are near the surface. They are represented by fine-grained granites, ancient quartzites, marbles and gneisses. There is an area on the northern slope, the basement of which lies at a depth of about 1.5 km. Its rocks are intruded by granite intrusions at different stages of geological development.
European part
Here the Khibiny Mountains are of interest. The tectonic structure is represented by denudation dissected elevated plains. They occupy territoryKola Peninsula and Karelia. The tectonic structure that formed the Khibiny Mountains arose in the form of intrusions and dislocations. It was they who predetermined the terrain. The alkaline massif of the territory is represented by one of the multiphase complex intrusions. It is located on the border of the Gnei Archean complex and the Proterozoic formations of the Varzuga-Imandra suite, as well as in the zone of a key transverse fault that runs along the line of the river. Cola - r. Niva.
