Results of the Hercynian folding era
The Hercynian fold appeared in the late Paleozoic. As a result of Hercynian tectonic processes, geosynclinal development in the Ural-Mongolian and Atlantic geosynclinal belts was completely completed.
In the Ural-Mongolian belt, the Hercynides include the Ural-Novaya Zemlya (1) folded region (islands New Earth, Vaygach, mountain structures of Pai-Khoi, Ural, Mugodzhar); Tien Shan(2) folded region (Karatau, Ugam, Pskem, Chatkal, Fergana, Zeravshan, Turkestan, Gissar ridges); Dzhungar-Balkhash (3) zone (Zharminsky, Kalbinsky and Narymsky ridges of Kazakhstan); Taimyr-Severozemelskaya (4) folded region (Taimyr peninsula and Severnaya Zemlya archipelago), Mongol-Okhotsk (10) folded region (Mongolian Altai, Gobi Altai, Khingai ridge, Gobi desert, Bureinsky ridge), West Siberian (11) and Scythian-Turanian (12) slabs.
In the Mediterranean belt, geosynclinal development was completed on the territory of the Iberian Peninsula (5), in the northern part Western Europe(6), within the Kun-Lun (7), Qin-Ling (8) ridges; in Africa - in the Inner Atlas (9).
In the Atlantic belt, the Hercynides include the south of Great Britain (13) and the Mexican-Appalachian (14) region (southwestern Appalachians, Gulf Coast, Florida Peninsula).
In the Pacific geosynclinal belt, geosynclinal development was completed in southern Africa - in the Cape Mountains (15) and in eastern Australia within the Great Dividing Range (16).
By the beginning of the Mesozoic there arose Hercynian structure of the earth's crust, in which the following are distinguished structural elements: areas of more ancient consolidation, Hercynides, geosynclinal belts (Fig. 9.4).
Mesozoic folding covers the Triassic, Jurassic and Cretaceous periods. It manifested itself most intensively in the Mediterranean and Pacific geosynclinal belts. In the Mediterranean belt, the Tibetan-Indochina (1) folded region (southern Tibet, Mekong River basin, Malacca Peninsula) is classified as mesozoids. In the Pacific - (2) Sikhote-Alin, (3) Intra-Cordilleran (Brooks Range, Mackenzie Mountains, Rocky Mountains, Great Basin, Colorado Plateau) and (4) Verkhoyansk-Chukotka (Verkhoyansky, Sette-Daban, Anyuisky, Chersky, Momsky ridges , Yudomsky, Poluosny Ridge, Chukotka Peninsula, Wrangel Island, New Siberian Islands, Laptev Sea) folded areas.
Mesozoic folding led to the emergence of depressions in the Atlantic, Indian and Arctic oceans. IN Mesozoic structure of the earth's crust(Fig. 9.5), formed by the beginning of the Paleogene period, ancient platforms and young platforms (areas of earlier consolidation), mesozoids and geosynclinal areas are distinguished.
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78.1.
MESOZOIC FOLDING(Greek mesos average) development of geosynclines with deep depressions of the earth's crust and the accumulation of powerful sediments, which were folded into folds, raised in the form of mountains, broken through by intrusions of granitic magma and volcanic eruptions that lasted from the end of the Triassic to the beginning of the Paleogene period. In different areas, this folding manifested itself with unequal intensity and at different times; therefore, it has several names.
Mesozoic folding began most early in Southeast Europe, South Asia, and Taimyr; it took a particularly long and intense time along the continental margins of the Pacific Ocean and, after a short break, resumed during the Alpine folding. Its granite intrusions are associated with a variety of minerals and numerous deposits of non-ferrous metals and gold, especially in North America and in the North-East of Russia.
Mesozoic Folding
Mesozoic folding is a set of geological processes of folding, mountain building and granitoid magmatism that occurred during the Mesozoic era. It manifested itself most intensively within the Pacific Mobile Belt. There are foldings: ancient Cimmerian, or Indosinian, which appeared in the end. Triassic early Jurassic; Young Cimmerian (Kolyma, Nevada, or Andean); Austrian (at the boundary of the Early and Late Cretaceous) and Laramie. Pacific folding is independently distinguished in areas adjacent to the Pacific Ocean: in the East. Asia, Cordillera and Andes. Ancient Cimmerian folding appeared at the end. Triassic early Jurassic in mountain structures of Crimea, Northern. Dobruja, on Taimyr, in the North. Afghanistan, South-East. Asia, Patagonian Andes and Northeast. Argentina; Young Cimmerian in con. Jurassic early chalk in the Verkhoyansk-Chukotka region, Center. and South-East. Pamir, Karakoram, Center. Iran, the Caucasus, Western Northern Cordillera America, Andes and other areas. Laramie folding one of the youngest eras of Mesozoic folding, manifested itself at the end. chalk beginning Paleogene in the regions of the Northern Rocky Mountains. America, in the Andes South. America, etc.
Areas of Mesozoic folding
Towards the end Paleozoic era, as already mentioned, all geosynclines and mobile areas turned into vast rigid fields. As a result of upward movements of the earth's crust, they were freed from sea waters. A theocratic regime was established.
The Mesozoic era (the era of middle life) began, the era of a new, higher stage of development of the nature of the Earth as a whole.
In the Mesozoic, the foundations of the modern topography of our planet were laid, including within the territory of the CIS, and the main outlines of the continents and oceans were determined.
Mesozoids occupy vast spaces, closing and connecting the territories of more ancient parts of the consolidation of the earth's crust. Various shapes Mesozoic folding is expressed in the east and northeast of Siberia, the Far East, i.e. in the territory total area about 5 million km2. But Mesozoic tectogenesis was also reflected in more ancient structures of the Precambrian, Baikal and Paleozoic stages.
The Mesozoic structures include Eastern Transbaikalia, the south of the Far East with Sikhote-Alin and the Verkhoyansk-Kolyma-Chukchi fold system. Thus, the western Pacific geosynclinal belt belongs to the Mesozoic structures. The modern surface of the East Siberian part and the Far East is characterized by a wide distribution of mountain structures. In addition to the typically mountainous terrain in Eastern Siberia and in the Far East there are numerous highlands, plateaus, plains (the area of the latter is generally not large) and, finally, the vast Pre-Verkhoyansk regional trough. The manifestation of Mesozoic folding is noted in Kopetdag, Mangyshlak, Donbass, Crimea, and the Caucasus.
In the area of the Mesozoic folded systems of Eastern Siberia and the Far East, the main ones were the Neo-Cimmerian and Laramian movements of the Cretaceous period. The geosynclinal basin extended from the Siberian Platform to the east, i.e., into the territory of the Far East. It was a huge sea in which thick layers of sediment accumulated, amounting to many thousands of meters. In the geosynclinal marine basin there were ancient mountainous mid-land masses: the Kolyma-Indigirsky, Omolon and others, the protrusion of the Siberian platform stood out - the Aldan shield, and in the southeast - the Chinese shield. The accumulation of sediments in the geosynclinal basin occurred due to the erosion and destruction of the ancient middle massifs and the Siberian, De Long, and Okhotsk platforms surrounding the geosyncline. Tectogenesis in the ancient platforms and mountain structures of the Paleozoic, which surrounded the Mesozoid territories from the west, northwest and south, proceeded in a complex and unique manner. One of the indicators of this originality was the different times of tectonic processes and the difference in the forms of their manifestation. But in general, the Mesozoic era in the east of our country ended with the replacement of the maritime regime by the continental one.
The Mesozoic folding was most active between the Kolyma massif and the Siberian platform (Verkhoyansk zone). Fold movements here were accompanied by volcanic eruptions and intrusions of granitoids, which led to diverse and very rich mineralization (rare metals, tin, gold, etc.). The middle massifs were subject to deep faults, through the cracks of which effusive materials flowed onto the surface. For mesozoids of the Eastern and North-Eastern Siberia folded zones with anticlinal and synclinal structures are characteristic.
The geological development of the south of the Far East is similar to the development of the northeast. Folded structures were also formed during the Mesozoic stage of tectogenesis, but much earlier the middle massifs of the Precambrian and Paleozoic arose: the Zeya-Bureya plate and the Khanka massif, which was the outskirts of the Manchurian platform. In the Poleozoic, the cores of the axial parts of the Tukuringra-Dzhagdy, Bureinsky, Sikhote-Alin, etc. ridges were also formed. Ancient folding here was accompanied by intense intrusions of granitoids, which caused mineralization.
Mineral resources throughout the Mesozoic folded area of eastern Siberia and the Far East are diverse. Mineralization zones are usually confined to ancient hard massifs (or to their edges): iron ores, non-ferrous metal ores, tungsten, molybdenum, gold, etc. Deposits of stone and brown coals, gas, oil, etc.
78.2.
Laurasia is the northern of the two continents that formed the continent of Pangea. Laurasia included Eurasia and North America. They broke away from the mainland and became modern continents between 135 and 200 million years ago.
In ancient times, Laurasia was a supercontinent and was part of Pangea, which existed in the late Mesozoic era. This continent was formed by those territories that today are the continents of the Northern Hemisphere. In particular, it was Laurentia (the continent that existed during the Paleozoic era in the eastern and central parts of Canada), Siberia, the Baltic, Kazakhstan, as well as the north and east continental shields. The continent received its name from Laurentia and Eurasia.
Origin
Protocontinent Laurasia is a phenomenon of the Mesozoic era. It is currently believed that the continents that formed it, after the collapse of the Motherland (1 billion years ago), formed one supercontinent. To avoid confusion with the name of the Mesozoic continent, it was simply attributed to proto-Laurasia. Referring to current thinking, after connecting with the southern continents, Laurasia formed the late Precambrian supercontinent called Pannotia (Early Cambrian), and was never separated again.
Fracture and formation
During the Cambrian era, for the first half a million years, Laurasia was located in equatorial latitudes. The supercontinent began to break apart into Siberia and Northern China, continuing to drift towards the north; in the past time they were further north than 500 million years ago. By the beginning of the Devonian period, Northern China was located near the Arctic Circle and was the northernmost landmass throughout the Carboniferous Ice Age (300-280 million years ago). To date, there is no evidence of major icing of the northern continents. During that cold period, Baltica and Laurentia connected with the Appalachian Mountains platform, allowing for the formation of huge reserves of coal. It is this coal that today forms the basis of the economy of regions such as Germany, West Virginia and part of the British Isles.
In turn, Siberia, moving south, connected with Kazakhstan, a small continent that today is considered the result of a volcanic eruption in the Silurian era. At the conclusion of these reunions, Laurasia changed its form significantly. At the beginning of the Triassic era, the shield of East China was reunited with Laurasia and Gondwana, resulting in the formation of Pangea. Northern China continued to drift from the near-Arctic latitudes and became the last continent that never connected with Pangea.
Final separation
About 200 million years ago, the procontinent Pangea collapsed. After breaking away, North America and northwestern Africa were separated by the new Atlantic Ocean, while Europe and Greenland (along with North America) were still one. They divided only 60 million years ago in the Paleocene. After this, Laurasia split into Eurasia and Laurentia (present-day North America). Ultimately, India and the Arabian Peninsula were annexed to Eurasia.
78.3.
The collapse of Gondwana began in the Mesozoic, Gondwana was literally torn apart piece by piece. By the end of the Cretaceous and the beginning of the Paleogene periods, the modern post-Gondwanan continents and their parts emerged: South America, Africa (without the Atlas Mountains), Arabia, Australia, and Antarctica.
Gondwana (named after historical area in Central India), a hypothetical continent, which, according to many scientists, existed in the Paleozoic and partially Mesozoic eras in the Southern Hemisphere of the Earth. It included: most of modern South America (to the east of the Andes), Africa (without the Atlas Mountains), o. Madagascar, Arabia, the Hindustan Peninsula (south of the Himalayas), Australia (to the west of the mountain ranges of its eastern part), and, possibly, most of Antarctica. Proponents of the hypothesis of the existence of Gondwana believe that in the Proterozoic and Upper Carboniferous, extensive glaciation developed on the territory of Gondwana. Traces of the Upper Carboniferous glaciation are known in Central and Southern Africa, southern South America, India and Australia. In the Carboniferous and Permian periods, a unique flora of the temperate and cold zones developed on the mainland, which was characterized by an abundance of glossopteris and horsetails. The collapse of Gondwana began in the Mesozoic, and by the end of the Cretaceous and the beginning of the Paleogene periods, modern continents and their parts separated. Many geologists believe that the destruction of Gondwana was a consequence of the horizontal expansion of its modern parts, which is confirmed by paleomagnetism data. Some scientists suggest not the expansion, but the collapse of individual sections of Gondwana, which were on the site of the modern Indian and South Atlantic oceans.
79. 2 .
Features of sedimentation. Continental red-colored strata and weathering crust are typical for the Triassic. Marine sediments were localized in geosynclinal areas. Trap magmatism manifested itself on a large scale on the Siberian, South American and southern African platforms. There are three types - explosive, lava and intrusive (sills). In the Jura, sediments are more diverse. Among the marine ones are siliceous, carbonate, clayey and glauconitic sandstones; continental - weathering crust deposits predominate, and coal-bearing strata are formed in lagoons. Magmatism manifested itself in geosynclinal areas - the Cordillera and Verkhoyansk-Chukchi, and trap magmatism - on the South American and African platforms. A feature of the Cretaceous deposits is the maximum accumulation of chalk (consists of foraminifera and the remains of coccolithophorid algae shells).
Paleogeography of the Mesozoic. The formation of the supercontinent Pangea-2 is associated with the greatest regression of the sea in the history of the Earth. Only small areas adjacent to the geosynclinal belts were covered by shallow seas (areas adjacent to the Cordillera and the Verkhoyansk-Chukotka geosyncline). The Hercynian fold belts represented areas of dissected relief. The Triassic climate is arid continental, only in the coastal regions (Kolyma, Sakhalin, Kamchatka, etc.) it is moderate. At the end of the Triassic, sea transgression began, which became widespread in the Late Jurassic. The sea extended to the western part of the North American Platform, almost the entire East European Platform, and to the northwestern and eastern parts of the Siberian Platform. The maximum sea transgression occurred in the Upper Cretaceous. The climate of these periods is characterized by alternating humid tropical and dry arid.
79.3.
Geocratic periods in the history of the Earth (from geo... and Greek kratos strength, power), periods of significant increase in land area, as opposed to thalassocratic periods, characterized by an increase in sea area. G.P. are confined to the second half of tectonic cycles, when general uplifts of the earth’s crust transform a significant part of the continents previously flooded by a shallow sea into dry land. They are characterized by a large contrast of climates, in particular a sharp increase in the areas of dry (arid) and cold climatic zones. Typical of the glaciers is the accumulation of continental red-colored strata composed of aeolian, alluvial, and lacustrine sediments of arid plains, partly of true deserts, as well as glacial deposits. No less typical are deposits of internal closed and semi-enclosed sea basins with high salinity in sediments of highly salted lagoons (dolomites, gypsum, salts). Geography can include the end of the Silurian and a significant part of the Devonian periods, the end of the Carboniferous, Permian and part of the Triassic periods, the Neogene and Anthropocene periods (including the modern era).
Thalassocratic periods in the history of the Earth, periods of widespread seas on the surface of modern continents. They are contrasted with geocratic periods, which are characterized by a significant increase in land area. In terms of time, the Thalassocratic periods refer to the middle of tectonic cycles (stages), when subsidence of the earth's crust prevailed over most of the earth's surface, due to which almost everywhere a significant area of continents was flooded by the sea. The increase in the area of the hydrosphere contributed to the development of a humid marine climate with small temperature fluctuations. During the Thalassocratic periods, predominantly marine sedimentary strata accumulated, among which carbonate rocks played an important role. Thalassocratic periods include the Middle Cambrian, Upper Silurian, Middle and early Late Devonian, Early Carboniferous and Late Cretaceous.
80.1.
Eustatic fluctuations in sea level (from the Greek éu good, completely and stásis standing still, rest, position), universally traceable slow changes in the level of the World Ocean and associated seas. Eustatic movements (eustasy) were originally identified by E. Suess (1888). Differentiate between movements coastline: 1) as a consequence of the formation of sea depressions when true changes in sea level occur, and 2) as a consequence of tectonic processes leading to apparent movements of sea level. These fluctuations, causing local transgressions and regressions caused by different acting tectonic forces, were called deleveling, and wide transgressions and regressions caused by fluctuations in the level of the water shell itself were called hydrokinematic (F. Yu. Levinson-Lessing, 1893). A.P. Pavlov (1896) called negative movements of the coastline geocratic, and the advance of the sea hydrocratic. Among the hypothetical factors determining eustasy, there is a change in the total volume of ocean water in the geological history of the Earth, which was determined by the evolution of the continents. On initial stages During the development of the earth's crust, the importance of juvenile waters in the E.C. was decisive; later the importance of this factor weakened. Stabilization of water volume began, according to A.P. Vinogradov, in the Proterozoic, and from the Paleozoic the volume water mass the hydrosphere changed within insignificant limits; Not great value processes of sedimentation and volcanic outpouring on the bottom of the seas (sedimentoeustasy) and, as a consequence, an increase in the level of the World Ocean. Beginning with the Paleozoic, the tectonic factor (tectonoeustasy) was of decisive importance, influencing changes in the capacity of the sea. and oceanic depressions with changes in the relief and structure of the ocean floor and adjacent continents. Apparently, Ch. fluctuations in the level of the World Ocean are associated with the development of the system of mid-ocean ridges and with the phenomenon of spreading of the seabed. Against the background of the action of tectonoeustasy in recent geological times, the climatic factor in the form of glacioeustasy played a great influence (see. Oscillatory movements Earth's crust, Modern tectonic movements). During glaciations, when water concentrated on the continents, forming ice sheets, the level of the World Ocean dropped by approximately 110x140 m; after melting, glacial waters again entered the World Ocean, increasing its level by approximately 1/3 of its original level. A decrease in temperature and a change in salinity influenced the density of water, due to which the level of the World Ocean in high latitudes differed by several meters from the level of the World Ocean in equatorial regions. The formation of the lowest terrace 3 × 5 m is associated with these factors. Planetary factors (changes in the speed of rotation of the Earth, displacement of the poles, etc.) also played some role in the mechanism of eustasy. The study of eustasy processes is of great importance for historical geology and understanding the peculiarities of the formation of shelf zones, which are associated with the formation of various minerals.
80.2.
Mesozoic climate
Invoking climatically well-known modern analogues of Mesozoic lithogenetic formations and modern ecological analogues of Mesozoic vegetation and Mesozoic organic world, as well as using paleothermic data, we obtain the necessary data for an approximate quantitative assessment of the climatic conditions of the past.
Early and Middle Triassic
The climate of the Mesozoic and especially the Triassic was almost isothermal, therefore the natural zonation of the continent at that time was determined mainly by the distribution of atmospheric precipitation and not so much by the volume as by the mode of precipitation during the year. For the Early and Middle Triassic within Eurasia, three main natural areas: extra-arid (desert), which included the predominant part of Europe, Arabia, Iran, Middle and Central Asia; moderately arid (dry savanna), the landscapes of which were dominant in the territory Northern Europe, Western and Southern Siberia, Transbaikalia, Mongolia and Eastern China, and semiarid (moderately humid savannah), covering northeast Asia from Khatanga and Chukotka to the Japanese Islands, as well as Southeast Asia.
81.2.
IRIDIUM ANOMALY is an amazing discovery made by American geologist Walter ALVAREZ in 1977 in a gorge near the city of Gubio, 150 kilometers from Rome. At great depths, a thin layer of clay was found with an iridium content 300 times higher than normal. This layer lay at a depth corresponding to the geological boundary between the Mesozoic and Cenozoic - the time when dinosaurs became extinct. Comparing this fact with the fact that usually the iridium content in earth's crust negligible - 0.03 parts by weight per billion, and in meteorites the concentration of this substance is almost 20,000 times greater. Alvarez suggested that the iridium anomaly arose as a result of the fall of a large cosmic body, which caused global catastrophe that killed the dinosaurs. This assumption remains a hypothesis. Meanwhile, iridium anomalies with approximately the same concentration as in the Gubio Gorge have already been found in many places on the planet - in Denmark, Spain, on the coast of the Caspian Sea. But the final version of the fall of an iridium meteorite will be recognized when a specific crater is discovered at the site of its fall .
82.1.
Cenozoic ( Cenozoic era) era in the geological history of the Earth spanning 65.5 million years, from the great extinction of species at the end of the Cretaceous period to the present. Translated from Greek as “new life” (καινός = new + ζωή = life). The Cenozoic period is divided into Paleogene, Neogene and Quaternary periods (Anthropocene). Historically, the Cenozoic was divided into the Tertiary (Paleocene to Pliocene) and Quaternary (Pleistocene and Holocene) periods, although most geologists no longer recognize this division.
Life in the Cenozoic
Cenozoic is an era characterized by great variety land, sea and flying species of animals.
Geologically, the Cenozoic is the era in which the continents acquired their modern shape. Australia and New Guinea separated from Gondwana, moved north and eventually moved closer to Southeast Asia. Antarctica took its current position near the south pole, the Atlantic Ocean expanded, and at the end of the era South America joined North America. The Cenozoic is the era of mammals and angiosperms. Mammals have undergone a long evolution from a small number of small primitive forms and have become distinguished by a wide variety of land, sea and flying species. The Cenozoic can also be called the era of savannas, flowering plants and insects. Birds also evolved significantly during the Cenozoic. Cereals appear among the plants.
82.2.
The stratigraphic division and lithological characteristics of Paleozoic deposits developed in the Belousovsky ore district were developed by us taking into account the definitions of fauna and flora in Carboniferous deposits, as well as spores and pollen in the formations of the Upper and Middle Devonian. The silent rock strata lying between the dated Frasnian and Lower Carboniferous deposits are conventionally assigned to the Famennian. The stratigraphic position of these strata was determined by comparing their lithological composition with faunally dated sections of other areas.
In the Belousovsky ore district of the Irtysh region, the following formations are distinguished: Glubochanskaya B2egv, Shipulinskaya D2gv, Belousovskaya Defri, Garaninskaya Difri, Irtyshskaya Dafmi (?), Pikh-tovskaya (Grebenyushinskaya) Bzgtg, Bukhtarma Cit2 and Maloul -binskaya CinС2. Of these, the first four were established by M.I. Drobyshevsky in 1954. The ore deposits of the deposit, located among hydrothermally altered rocks, are confined to the contact of the Glubochansky formation with the Shipulinsky and Belousovsky formations.
Structurally, the study area covers part of the northeastern wing of the Irtysh anticlinorium, which is complicated by folds and faults of northwestern strike. Characteristic feature of such folds is the tilting of their axial surfaces to the southwest.
All Paleozoic rocks experienced significant changes under the influence of regional contact and, in certain narrow zones, hydrothermal metamorphism. At the base of the stratigraphic section lies a deeply metamorphosed complex of rocks, conventionally attributed to pre-Middle Devonian age. This complex is represented by biotitized, epidotized amphibole-pyroxene gneisses and mica-quartz schists, which are exposed in the erosion section in the core part of the Irtysh anticlinorium in the southeast of the region. The rocks of the listed formations are exposed to the surface in small areas. The rest of the area is covered by loose sediments.
82.4.
One of the most important global metallogenic structures is the Mediterranean belt - the product of the ocean, which received the name Tethys from E. Suess. From a metallogenic standpoint, the Mediterranean belt was specially studied by the outstanding followers of V.I. Smirnov and my late friend G.A. Tvalchrelidze and I would like to dedicate of blessed memory both scientists are very short essay the long and complex history of the Tethys Ocean and the Mediterranean belt.
The concept of “Tethys Ocean” appeared at the end of the last century (1893) in the famous work of E. Suess “The Face of the Earth”. Somewhat earlier, another Austrian geologist M. Neumayr, who compiled the first world paleogeographic map of the Jurassic period, highlighted the “Central Mediterranean Sea” on it. For both scientists the most convincing evidence the existence of such a body of water between the northern and southern rows of continents, there was a striking similarity between the Triassic and Jurassic marine faunas from the Alps, through the Himalayas to Indonesia (Timor), which had been established by that time. G. Stille expanded this concept in time and showed that the Tethys Ocean arose already in the late Precambrian, after the “Algonkian fragmentation” he identified. In this paper I take this view, even though it was based on a fixist premise that has now been completely discredited. It will be further shown that the Tethys Ocean in its long evolution went through a number of stages, including its partial closure and re-opening in another place. The sequence of these stages makes it possible to distinguish the Late Proterozoic-Cambrian Proto-Tethys, the Ordwian-Carboniferous Paleotethys, the Permian-Jurassic Mesotethys and the Jurassic-Paleogene Neo-Tethys, partially overlapping each other in space and time.
Birth of Tethys and Protethys
It is now almost generally accepted that as a result of the Grenville orogeny, about 10 billion years ago, a supercontinent arose, which recently received the name Rodinia. This supercontinent existed until approximately the middle of the Late Riphean, about 850 million years ago, and then began to experience destruction. This destruction began with rifting, which further led to spreading and new formation of the oceans: the Pacific, Iapetus, Paleoasian and Proto-Tethys among them. The birth of this first incarnation of Tethys is proven by the outcrops of ophiolites of Late Riphean age in the Anti-Atlas, the Arabian-Nubian shield on its southern periphery, in the Alps, and the Bohemian Massif on the northern. In the Vendian-Early Cambrian time, the first generation of the Tethys - Prototethys 1 ocean disappeared (partially?) as a result of the Pan-African-Cadoma orogeny, and a significant area was expanded by the Gondwana supercontinent, forming the Epicadomian perigondwanan platform. It formed the oldest foundation of Western Europe, extending north to the English Midlands and the edge of the East European ancient platform.
But very soon the destruction of this newly formed continental crust began and the ocean basin reappeared (or was restored). Remains of its crust are known in the Southern Carpathians, the Balkans (Stara Planina), in northern Transcaucasia (Dzirula massif) and further to the east, in particular in Qilianshan (China). This Vendian-Cambrian basin can be called Proto-Tethys II in contrast to the Late Riphean Proto-Tethys I. It formed possibly along the suture between the Epicadomian Perigondwanan platform and Fennosarmatia (Baltica). It is interesting that the same two generations of ophiolites are known in the south of Siberia (Eastern Sayan) and in Western Mongolia, which belonged to the Paleoasian Ocean in this era. Prototethys II closed (again partially?) in the second half of the Cambrian and finally at the beginning of the Ordovician thanks to the Salairian orogeny. At the same time, a new ocean was formed - Paleotethys.
Paleotethys
It can be assumed with sufficient reason that this was precisely the ocean basin that later gave rise to the main trunk of European variscids (Hercynids). Its eastern continuation can be seen in the North Caucasus and further up to Qinling in Central China. In accordance with the age of ophiolites, two generations of basins are oceanic or suboceanic, i.e. thinned and reworked continental crust can be distinguished. The older of these is documented by ophiolites of Ordovician age exposed in the Western Alps, Western Carpathians and the Front Range of the Greater Caucasus.
The opening of Paleotethys I was connected from Gondwana to the Epicadomian microcontinent Avalonia and its drift to the north. At the same time, that (large) part of the Epicadomian platform, which remained attached to the Early Precambrian skeleton of Gondwanaland, separated from the East European craton-Baltica along the “Törnqvist Sea”, underlain by thinned continental crust.
In the left half of the Devonian, the Rhenohercynian back-arc basin opened on the northern periphery of the Paleotethys in the rear of the Middle German crystalline uplift. The ophiolites of the Lizard Peninsula in Cornwall, the MOR-type basalts of the Rhine Shale Mountains and the Sudetenland ophiolites are relicts of the oceanic crust of this basin.
In the middle of the Devonian, a chain of uplifts arose in the central zone of Paleotethys I; it is known as the Nigerian Cordillera. She divided the main ocean basin into two - the northern one, which includes the Saxothuringian and Rhenohercynian variscid zones and finds its southwestern continuation in the Iberian Meseta, and the southern one, which represents Paleotethys proper and can be called Paleotethys II.
Paleotethys I or Reikum entered the final stage of its evolution in the late Paleozoic, transforming into the Variscan fold-thrust belt of Western and Central Europe, North Caucasus, its buried continuation in the south of the Turan young platform, the Hindu Kush, the southern zone of the Southern Tien Shan, the Northern Pamirs, Kunlun and Qinling.
Paleotethys closed completely only in its western part, west of the meridian of Vienna and Tunisia, forming Pangea. Further to the east it was inherited by Mesotethys.
Mesotethys
The history of Mesotethys proper begins in the Late Permian-Triassic and lasted until the Late Triassic - Early Jurassic, to the Early Cimmerian orogeny - Mesotethys I or the Late Jurassic - Early Cretaceous - Mesotethys II. The main basin of Mesotethys I extended from the border region of Northern Hungary - Southern Slovakia in the Inner Carpathians through the basement of the superimposed Pannonian Basin into the Vardar zone in Yugoslavia and further into the Pontides of northern Anatolia and possibly into central Transcaucasia, where its continuation may be hidden under the molasse of the Kura intermountain trough. Its further continuation can be assumed along the Early Cimmerian suture between the Turanian platform and the Elbrus fold-thrust system on both sides of the South Caspian Basin in Northern Iraq. Further east, Mesotethys I can be traced through the southern zone of the Northern Pamirs, southern slope Kunlun and Qinling, the famous Songpan-Kanze triangle and, with a turn to the south, through Yunnan, Laos, Thailand, Malaya - the classical region of the Indosinids or early Cimmerids (early Yangshanids in China). The northern branch of Mesotethys I, merging with the main basin somewhere in northern Afghanistan, extended through the Kopet Dag, the southern slope of the Greater Caucasus, the Crimean Mountains and all the way to northern Dobruja, where its blind end was located.
Mesotethys I was replaced by Mesotethys II at the end of the Middle Jurassic (late Bathonian-Callovian). At this time, Tethys was transformed from a wide gulf opening eastward into the Pacific Ocean into a continuous oceanic belt dividing Laurasia and Gondwana along its entire length. This division was due to the emergence of the Caribbean, the central Atlantic and the Liguro-Piedmont "ocean". The latter joined in the east with the residual Vardar basin, which was partially closed in the northeast by the Early Cimmerian folding. But further to the east, the continuation of this basin, unlike Mesotethys I, deviated south from the Pontides and extended on the other side of the “Cimmerian Continent” of J. Shenger, then crossing the Lesser Caucasus through Lake Sevan and the Akera Valley and reaching Iranian Karadag. Ophiolite outcrops disappear further to the southeast, but reappear in the Sabzevar area south of eastern Elbrus. To the east of the Herirud transform fault, a continuation of Mesotethys II can be seen in the Farakhrud zone of central Afghanistan and further, after crossing another Afghan-Pamir fault, in the Rushap-Pshart zone of the Central Pamirs and, having experienced a new shift along the Pamir-Karakoram fault, in the Bangong zone -Nujiang of central Tibet. Then this basin, like Mesotethys I, turned to the south (in modern coordinates) and continued in Myanmar to the west of the Sino-Burman massif (Mogok zone).
The entire eastern part of Mesotethys II, starting from Sabzevar-Farakhrud, was finally closed as a result of the Late Cimmerian orogeny. Western, European part The Vardar zone, in particular, also experienced this diastrophism, but here it was not final. The decisive role in this regard belonged to the intra-Senonian, sub-Hercynian tectonic phase.
At the end of the Jurassic, another basin with oceanic or suboceanic crust arose north of the main Mesotethys basin in Europe and extended roughly parallel from the Velis zone of the Alps through the Pieniny "cliff" belt of the Carpathians and further, possibly, the Niš-Troyan zone of eastern Siberia - western Bulgaria. Most important role The Australian orogenic phase in the mid-Cretaceous played a role in the closure of this basin.
This northern basin was not the only one in the Mesozoic Tethys system. The other was the Budva-Pindos basin in the Dinarides-Hellenids and its probable continuation in the Taurus system of southern Anatolia. The third was the back-arc basin of the Greater Caucasus. The final closure of both basins occurred in the late Eocene. But in the meantime, two more back-arc basins formed in the late Cretaceous-early Paleocene:
Black Sea and South Caspian.
Thus, the closure of the European and West Asian segments of Mesotethys II occurred gradually, through a series of compression pulses, starting with the Late Cimmerian and ending with the Pyrenean. And gradually the leading role in the Mediterranean mobile belt passed from the Meso to the Neo-Tethys.
Neo-Tethys
This was the last incarnation of the great ocean. Neo-Tethys was located south of Mesotethys and was formed due to the separation and drift to the north of several fragments of Gondwana - Adria (Apulia), central Iran, Lut block, central Afghanistan, southern Tibet (Lhasa). The opening of the Neoteti sa was preceded by continental rifting, most clearly expressed in its eastern, Himalayan-Tibetan segment, where it began in the Late Permian. Spreading in the Neotethys region continued from the Late Triassic-Early Jurassic to the Late Cretaceous-Early Paleogene. Neo-Tethys itself extended from the Gulf of Antalya, Cyprus and northwestern Syria around the northern protrusion of the Arabian Plate and then in the rear of the Balochistan ranges and the Himalayas, turning south of the Sunda-Banda arc. As for the western end of Neo-Tethys, two versions are possible: 1) it could have found its blind end somewhere between Adria and Africa, in the area of the Ionian Sea and Sicily; 2) it could represent a continuation of the southwestern Dinarides-Ellinides trough - the Budva-Pindos trough. Just as it was in the case of Paleo- and Mesotethys, the main Neotethys basin was accompanied by side and behind-arc basins of different ages and with different degrees of destruction and transformation of the continental crust and the role of spreading. One of them is the Levant Sea of Jurassic age, the other is the Seistan Late Cretaceous-Early Paleogene basin in the extreme east of Iran. The other three, in the extreme west, are the Tyrrhenian Neogene basin in the rear of the Calabrian arc and the Aegean basin of the same age in the rear of the subduction zone of the same name, and finally, the Adaman Sea of the same age, in the extreme east, behind the Sunda subduction zone. The closure of the Neotethys began in the Senonian and accelerated significantly in the mid-late Eocene, when India and a number of microcontinents that had previously broken off from Gondwana, from Adria in the west to Transcaucasia and the Bitlis-Sanandaj-Sirijak microcontinent in the east, collided with the southern edge of Eurasia, and the same process manifested itself between the Indian plate and the southeastern protrusion of Europe, leading to the formation of the Indo-Burman chains. As a result, Neotethys turned out to be dismembered and only some of its remnants were preserved in the Mediterranean and the Black Sea-South Caspian region and in the Gulf of Oman, as well as relict subduction zones - Calabrian, Aegean, Makran, Sunda. Is this really the end of the long history of Tethys or just the beginning new phase its evolution remains an open question.
Conclusion
Considering that the ocean first formed between Laurasia and Gondwana as a single and separate supercontinents at the end of the Precambrian and finally ceased to exist as a whole by the Oligocene, we can consider this huge time interval as corresponding to the Wilson cycle, since at no point in this interval can we assume the absence such a vast water space, even during the period of the existence of Pangea, it was reduced to a very vast gulf comparable in size to the size of the Indian Ocean. However, we can talk about two separate Wilson cycles, separated by the period of the existence of Pangea - the Late Proterozoic-Paleozoic and the Mesozoic-Cenozoic. At the same time, we must admit that the Tethys Ocean during the Proterozoic and Phanerozoic repeatedly and very significantly changed the location and configuration of its the main, axial basin shifted from time to time, mainly in a southern direction, constantly maintaining the role of the water divide between Laurasia and Gondwana or their fragments. These changes did not occur gradually, but spasmodically, and this is what made it possible to distinguish individual stages in the evolution of Tethys and, accordingly, introduce the concepts of Proto-, Paleo-, Meso-, and Neotethys, despite the fact that some intervals of their “life” overlap one another . The closure of these changing oceans was due to orogenesis, long known under the names of the Baikal-Cadoma, Caledonian, Hercynian-Variscan, Cimmerian, and Alpine. Each of these orogenies was accompanied by the accretion of new terranes to Eurasia, which, as a rule, was compensated by the separation of other terranes from Gondwana. Some of these newly accreted terranes later experienced at least partial regeneration of mobility, but others remained attached to Eurasia, increasing its size. These different stages of the evolution of the Tethyan region correspond to the cycles identified a hundred years ago by Marcel Bertrand, and I have proposed to call them Bertrand cycles. In relation to the Wilson cycles, these cycles are of the second order, since they correspond not to complete, but only partial death of the ocean (and at its beginning to a displacement of the axis of its opening). It should be emphasized that the internal structure of the Tethyan region, or the Mediterranean mobile belt, during each stage of evolution remained complex and, in addition to the main basin, included several of its branches of different sizes, micro- and mini-continents, often superstructured by ensialic volcanic arcs. However, this is completely natural for the intercontinental ocean, for the Mediterranean Sea - Mittelmeer - as M. Neumayr defined it, the same century ago. The separation of continental fragments, their reverse rapprochement and, in general, their mutual movements were determined not only by rifting and spreading, not only by subduction, collision and obduction, but also to a large extent by transform faults and shifts. It goes without saying that a complete decoding of the complex history and structural development The Mediterranean belt throughout its entire length allows us to better understand the features of metallogeny. However, for now this can only be done partially, in relation to the western part of Tethys and newest stage its development since the Mesozoic. Therefore, this remains a task for the future and clearly requires international and multidisciplinary (stratigraphy, paleontology, lithology, petrology, tectonics, geophysics, geochemistry) research.
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General information
The eastern part of Russia is characterized by the widespread development of folded mountain regions of Mesozoic and Alpine age, which are part of the Pacific fold belt. Mesozoids are folded mountainous areas that completed their geosynclinal development in the Cretaceous period. However, typical platform development within their boundaries has not yet begun. The earth's crust has not acquired sufficient strength and thickness here. Examples of them are the Verkhoyansk-Kolyma (Verkhoyansk-Chukotka) and Far Eastern (Sikhote-Alin) regions.
The Verkhoyansk-Kolyma region occupies vast areas of the northeastern part of Russia. In the north, this region is washed by the Laptev and East Siberian seas. It also includes the islands of Novosibirsk, De Long, Lyakhovsky, Wrangel and others.
Stratigraphy
Precambrian deposits found within the most ancient massifs of the Verkhoyansk-Kolyma region. They are represented by deeply metamorphosed gneisses, crystalline schists, and amphibolites. In composition and appearance, these rocks are close to the rocks of the Archean complex of the Aldan Shield of the Siberian Platform.
Proterozoic formations are represented by various schists, quartzites, and marbled limestones. The deposits are intruded by granite intrusions. The total thickness of the Precambrian strata is over 5 km.
Breeds Paleozoic group combine sediments of Cambrian - Permian age. Paleozoic formations emerge on the surface only in the cores of anticlinoria. At the same time, Permian deposits are more widely developed. In the Paleozoic group, two strata are distinguished. Lower includes breeds from Cambrian to Lower Carboniferous. It is represented by alternating limestones, marls, dolomites, shales, and sandstones.
There are interlayers of conglomerates (Devonian) and effusive rocks (Cambrian, Devonian). There are intrusions of gabbrodiabases and granites. The total thickness of the Paleozoic terrigenous-carbonate strata is more than 15 km.
The Verkhoyansk complex, which includes Upper Paleozoic strata And lower Mesozoic(Middle and Upper Carboniferous, Permian, Triassic, Lower and Middle Jurassic). The complex is composed of uniformly interbedded dark gray and black sandstones, clayey shales with rare interlayers of limestone. Its thickness exceeds 10 km.
Mesozoic group(Upper Jurassic - Cretaceous) is widespread within the Verkhoyansk-Kolyma region. Upper Jurassic It is represented by terrigenous carbon-bearing deposits with interlayers of conglomerates and volcanic rocks (porphyrites and diabases) with a total thickness of more than 2 km. Lower Cretaceous composed of volcanic-terrigenous strata with layers of coal. The thickness of the thickness is up to 1 km. Along the coast of the Sea of Okhotsk, the thickness of the Lower Cretaceous volcanogenic formations reaches 3 km. The deposits of the Verkhoyansk complex of the Upper Jurassic and Lower Cretaceous are metamorphosed and folded into various folds. Only within the ancient middle massifs of the Verkhoyansk-Kolyma region do they lie almost horizontally.
Upper Cretaceous lies unconformably throughout and is composed of typically continental sediments. These are sands, clays, sometimes with layers of coal (lower reaches of the Kolyma and Indigirka rivers). Acid effusives and their tuffs are widespread. The thickness of the Upper Cretaceous is up to 1 km.
Sediments Cenozoic group are not widespread. Paleogene It is represented by thin sandy-clayey continental sediments and rather significant effusive strata of acidic composition.
Neogene deposits are known in river basins and intermountain depressions. These are continental terrigenous sediments of low thickness.
Lntropogenic the formations consist of glacial, alluvial, colluvial and marine sediments up to 100 m thick.
- (Pacific folding, Yenshan folding), the era of tectogenesis, which appeared during the Mesozoic era mainly along the periphery of the Pacific ca. The main phases are Cimmerian (late Jurassic, early Cretaceous; Crimea and northeast Russia), Laramian (late... ... Big Encyclopedic Dictionary
Mesozoic folding- The era of mountain building, which manifested itself during the Mesozoic era mainly along the periphery of the Pacific Ocean, the main phases being the Cimmerian and Laramie folds... Dictionary of Geography
- (Pacific folding, Yenshan folding), an era of tectogenesis that appeared during the Mesozoic era mainly along the periphery of the Pacific Ocean. The main phases are Cimmerian (end of the Jurassic, beginning of the Cretaceous; Crimea and North-East Russia), ... ... Encyclopedic Dictionary
A set of geological processes of folding, mountain building and granitoid magmatism that occurred during the Mesozoic era. It manifested itself most intensively within the Pacific Mobile Belt. There are foldings: ... ... Geographical encyclopedia
- (Pacific folding, Yeishan folding), era of tectogenesis, which appeared during the Mesozoic era ch. arr. on the periphery of the Pacific approx. Ch. phases Cimmerian (end of the Jurassic - beginning of the Cretaceous; Crimea and N.V. Russia), Laramian (end of the Cretaceous - beginning ... ... Natural science. Encyclopedic Dictionary
Appeared during the Mesozoic era, ch. arr. within the Pacific Mobile Belt. Recently (and by some tectonists even now) the S. m. was considered as part of the Alpine folding. The main phases of S. m. appeared non-simultaneously in... ... Geological encyclopedia
8th grade
Option 1
1. In which of the following eras did plants and animals appear?
1) The age of the Earth is about 5 billion years.
3.What is the name of the top layer of the platform, consisting of limestone, clay, sandstone?
a) basaltic c) sedimentary
b) granite d) limestone
4. Stable areas of the earth’s crust are called:
a) platforms b) shields
b) folded areas d) avalanche
5.The plains are located on:
a) platform b) in folded areas
b) boundaries of lithospheric plates d) on shields
6.Ranges rose into the Mesozoic folding:
a) Altai c) Sikhote-Alin
b) Caucasus d) Urals
7. Deposits are confined to ancient folded areas:
a) coal, oil, gas c) uranium
b) iron ores, gold d) table salt
8.What is the science of minerals called?
b) paleontology d) geology
9. Establish a correspondence between the mountains and their highest peaks:
1. Caucasus a) Pobeda
2. Altai b) Belukha
3. Sayan Mountains c) Elbrus
4. Chersky ridge d) Munku-Sardyk
10. The structure of the earth’s crust is shown on the map:
11.Underwater earthquakes often occur here, which give rise to Pacific Ocean tsunami:
a) Sakhalin c) Kamchatka
b) Madagascar d) Byrranga
12.Name the largest coal basin.
a) Vladimir c) Yakut
b) Kuznetsky d) Kursk
13.Where are diamonds mined in Russia?
a) Tunguska basin c) Yakutia
b) Lena basin d) Buryatia
14.What are the names of the areas within which it occurs? large number deposits of the same type of minerals?
a) deposit c) blockage
b) storage d) pool
15. The most severe region of our country, its relief is represented by medium-altitude mountains of middle age.
16.What is rich in the Tunguska basin in Eastern Siberia?
a) gas b) coal
b) oil d) furs
17.Where in Russia can you find echoes of an ancient glacier?
A) Far East c) Yakutia
b) Valdai Hills d) Karelia
18. The main destroyer and creator of the nature of the Caspian lowland is
a) pressure b) precipitation
b) wind d) air temperature
19. In what geological period of what geological era did we finish studying the topic “Geological structure and relief of Russia”?
a) Cambrian c) Neogene
b) Cretaceous d) Quaternary
20.What platform is the school you are on?
a) Russian c) Amur
Cartographic workshop
8th grade
Test work on the topic “Geological structure and relief”
Option 2
1. In which of the listed eras did reptiles appear to dominate?
a) Cenozoic c) Paleozoic
b) Mesozoic d) Proterozoic
2.Are the following statements true?
1) The age of the Earth is about 8 billion years.
2) The Great Glaciation influenced both the diversity of flora and fauna, as well as the topography of the earth’s surface.
a) only 1 statement is true c) both statements are true
b) only 2 statements are true d) both statements are wrong
3.What is the name of the lower tier, representing the base of the platform?
a) base c) foundation
b) shield d) horst
4. The mountains are located in ……. areas
a) platform b) folded
b) weathered d) foundation
5. In what era did the Caucasus Mountains begin to form?
a) Alpine c) Hercynian
b) Baikal d) Caledonian
6.What mountains were formed during the period of the Caledonian and Hercynian folds between ancient platforms and gradually began to collapse?
a) Altai c) Sikhote-Alin
b) Caucasus d) Ural
7.What minerals are located in folded areas?
a) coal b) oil
b) iron and copper ores d) gas
8.What is the name of the doctrine of the structure of the earth’s crust and its movements?
a) petrography c) geotectonics
b) paleontology d) geology
9. Establish a correspondence between the mountains and their peaks:
1. Caucasus a) Ichinskaya Sopka
2. Altai b) Belukha
3. Sayan Mountains in) Dykhtau
4. Kamchatka d) Munku-Sardyk
10. Map with information about the age of breeds:
a) physical b) tectonic
b) geological d) climatic
11.Where is the only area of modern volcanism in the country located?
a) Sakhalin c) Kamchatka
b) Kuril Islands d) Byrranga
12.What is the name of the richest iron ore basin on the planet?
a) KMA c) KMZH
b) BZhB d) KAM
13.What is the Udokan deposit of Transbaikalia rich in?
A) potassium salts c) oil
b) gold d) copper ore
14.Useful substances are not scattered throughout the earth’s crust, but are concentrated in certain areas of it, which are called...
a) deposit c) deposits
b) storage d) pool
15.What natural area are we talking about: “No region of our country has such a huge extent from north to south. The youngest mountains in Russia are located here.”
a) North-East Siberia c) Ural
b) Far East d) Western Siberia
16.What is the Kuznetsk basin rich in?
a) coal b) gas
b) oil d) diamonds
17.What are the names of mud-stone flows that arise as a result of heavy rains?
a) avalanche c) mudflows
b) moraine d) collapsing cobblestones
18.Which Russian village was completely destroyed in 1995 as a result of a strong earthquake?
a) Neftekamsk c) Neftegaz
b) Neftegorsk d) Severodvinsk
19. In what geological period of what geological era did you study the topic “Russian explorers of the 11th – 17th centuries”?
a) Cambrian c) Neogene
b) Cretaceous d) Quaternary
20.Which platform did you have breakfast on today?
a) Russian c) Amur
b) West Siberian d) North American
Cartographic workshop
Define geographical features, depicted on fragments of the map of Russia.
8th grade
Test work on the topic “Geological structure and relief”
ANSWERS
CARTOGRAPHIC ASSESSMENT PRACTICUM
Option 1 Option 2 “5” - 10 - 9
"4" - 8 -7
"3" - 6 - 5
1. Russian Plain 1. Caspian Lowland
2. Sayan Mountains 2. Timan Ridge
3.g. Khibiny 3. Central Siberian Plateau
4. Aldan Highlands 4. Ural
5.Verkhoyansk ridge 5.g. Byrranga
6, Altai 6. Sikhote - Alin ridge
7.West Siberian Plain 7.West Sakhalin Mountains
8.Caucasus 8.Sayans
9. Sredinny ridge 9.khr. Dzhugjur
10. Chersk ridge 10. Valdai Upland
ANSWERS ASSESSMENTS
Option 1 Option 2 "5" - 20 - 18
1.A 1.B “4” - 17 - 14
2.B 2.B “3” - 13 - 9
3.B 3.AB
4.A 4.B
5.A 5.A
6.B 6.D
7.A 7.B
8.A 8.B
9.1V,2B,3G,4A 9.1V,2B,3G,4A
10.B 10.B
11.AB 11.VB
12.B 12.A
13.B 13.G
14.G 14.A
15.A 15.B
16.B 16.A
17.VG 17.V
18.B 18.B
19.G 19.G
20.A 20.A
