The name of the ocean Tethys comes from the name of the Greek goddess of the sea Tethys - (Greek Tethys).

Ancient Ocean Tethys, existed during the Mesozoic era and separated the two ancient continents of the Earth, which were called Gondwana and Laurasia.

Modern scientific research by geologists, oceanologists and other scientists indisputably confirms the existence of an ancient oceanic basin on Earth, which separated in the meso Zoic era (200-70 million years ago) The European and Siberian continental masses from the African and Hindustan and connected the Atlantic Ocean with the Pacific.

At the end of the 19th century, this ocean was named Tethiso m at the suggestion of an outstanding Austrian geologist E. Suess.

Now there are only remnants (relics) of the once vast Tethys Ocean: the Mediterranean, Black Sea, Azov and Caspian Seas, and for the most part The former territory of Tethys contains the highest mountain ranges: the Pyrenees, the Alps, the Carpathians, the Caucasus, the Hindu Kush, the Himalayas, composed of rocks formed at the bottom of the former basin.

In 1965, Tajik geologists discovered in the valleys of the Zeravshan Range at an altitude of 1500 m above sea level a petrified starfish - an inhabitant of the underwater world. This find once again confirms the opinion of scientists that once the current The ridges of the Western Pamirs were an archipelago of islands among the expanses of Tethys.

Not only at the bottom of the Black Sea, you can find many fossils - inhabitants the once vast Tethys Ocean. The fossilized remains of the inhabitants of the sea can be found in dumps, near the city of Belogorsk in the Crimea.

Ammonites (lat. Ammonoidea) - an extinct subclass of cephalopods, existed in the pre-Cretaceous period. Fossilized remains of ammonites can be found in the Black Sea and on coastal rocks.

Ammonites got their name from the name of the ancient Egyptian god Amun, who was depicted with spiral horns.

The cephalopods became the dominant group of molluscs during the Ordovician period and were represented by primitive nautiloids. In our time, 2 modern subclasses are known: Coleoidea, which includes octopus, squid, cuttlefish; and Nautiloidea, represented by nautilus and Allonautilus.

2 extinct groups are also known: Ammonoidea (ammonites) and Belemnoidea (belemnites).

According to the same features - the structure and composition of the crust and the entire lithosphere, as well as the tectonic regime - these first-order units are subdivided into second-order units - mobile belts and stable areas. In the oceans, the former are represented by mid-ocean ridges, the latter by abyssal plains.

Thanks to deep-sea drilling and mapping of linear magnetic anomalies, the age of modern ocean basins can be considered established.

Theory of lithospheric plate tectonics

The theory of lithospheric plate tectonics provides an explanation for the origin of the oceans. Only spreading can explain the coincidence of the following data:

1. systematic increase in the age of basalts of the 2nd layer and overlying sediments from the axes of the mid-oceans towards the continents;
2. increase in the thickness and stratigraphic range of the sedimentary layer from zero values ​​on the spreading axis in the same direction;
3. an increase in ocean depth with increasing age of the crust and a transition from shallower, albeit pelagic, to deeper sediments up the section of the sedimentary cover;
4. the presence at the base of the sedimentary layer of metaliferous sediments deposited by hydrotherms on spreading axes;
5. an increase in the thickness and density of the lithosphere from the median ridge to the continent;
6. decrease in the intensity of magnetic anomalies in the same direction;
7. a decrease in the magnitude of the heat flux in the same direction.

Chronological classification

The age of many ancient oceans has been determined. By age, the oceans can be divided into:

Precambrian

• Panthalassa -0 - this super-ocean may have arisen around a crater at the site of a giant meteorite fall. This super-ocean opposed the Pangea-0 supercontinent on the opposite side of the planet. The age of the superocean is 2.5-2.2 billion years. According to the international stratigraphic scale, this interval corresponds to the Paleoproterozoic era - the Siderian Eurasia (Russia, Kazakhstan) or the Early Proterozoic period.

• Panthalassa-1 (Mirovia) - this super-ocean may have opposed the super-continent Pangea-1 on the opposite side of the planet. In modern geological literature, Panthalassa-1 is called Mirovia, while Pangea-1 is called Rodinia. The age of the superocean is 1600-850 million years. According to the international stratigraphic scale, this interval corresponds to the entire Mesoproterozoic era or the Neoproterozoic era according to the Tonian system. According to the scale of Northern Eurasia (Russia, Kazakhstan), it corresponds to the Early Riphean and Middle Riphean periods, inclusive.

• Mozambican - this ocean separated Western and Eastern Gondwana. Formed after the collapse of Mirovia and Rodinia. The age of the ocean is 850-600 million years. According to the international stratigraphic scale, this interval corresponds to the Neoproterozoic era - the Cryogenian period. If on the scale of Northern Eurasia (Russia, Kazakhstan), then the late Riphean.

• Protopacific - this ocean is the prototype of the modern Pacific Ocean and the direct heir to the superocean of Mirovia. It was formed as a result of the merger of Western and Eastern Gondwana into a single continent. The age of the ocean is 600-570 million years. According to the international stratigraphic scale, this interval corresponds to the Neoproterozoic era - the Cryogenic and Ediacaran periods. If on the scale of Northern Eurasia (Russia, Kazakhstan), then the Vendian period. Already in the Paleozoic era, it became the Paleopacific ocean.

• Prototethys - this ocean is the prototype of Tethys in the Cenozoic era. It was formed after the collapse of Mirovia and Rodinia of Eurasia (Russia, Kazakhstan) to the late Riphean and Vendian period. Already in the Paleozoic era, it became the Paleotethys ocean.

• Proto-Iapetus - this ocean is the prototype of Iapetus in the Paleozoic era. Formed after the collapse of Mirovia and Rodinia. The age of the ocean is 850-570 million years. According to the international stratigraphic scale, this interval corresponds to the Neoproterozoic era - the Cryogenic and Ediacaran periods. If on the scale of Northern Eurasia (Russia, Kazakhstan), then the late Riphean and Vendian period. Already in the Paleozoic era, it became the Iapetus ocean.

• Paleoasian - this super-ocean separated the East European platform from the Siberian platform, and the latter from the Tarim and Sino-Korean platforms. Formed after the collapse of Mirovia and Rodinia. The age of the ocean is 850-320 million years. According to the international stratigraphic scale, this interval corresponds to the period from the Neoproterozoic era to the Paleozoic era, respectively, from the Cryogenian period to the early Carboniferous. If on the scale of Northern Eurasia (Russia, Kazakhstan), then the period from the Late Riphean to the Early Carboniferous. Already in the Late Carboniferous, it became the Mongolian-Okhotsk Ocean. In the Late Carboniferous, it broke up into the Turkestan, Novaya Zemlya, Mongol-Okhotsk, and Solonker-Girinsky oceans.

• Boreal - this ocean is a prototype of the modern Arctic or Arctic Ocean, sometimes this ocean is considered the northern part of the Paleopacific Ocean. The age of the ocean is 850-240 million years.

Paleozoic

• Paleopacific - this ocean is the prototype of the modern Pacific Ocean and the direct successor of the Protopasific superocean. The age of the ocean is 570-240 million years. On the international stratigraphic scale, as well as on the scale of Northern Eurasia (Russia, Kazakhstan), this interval corresponds to the Paleozoic era. Already in the Mesozoic era, it became the Panthalassa-2 ocean.

• Iapetus - this ocean is the prototype of the modern Atlantic Ocean and the direct successor of the Protoyapetus superocean. The age of the ocean is 570-420 million years. On the international stratigraphic scale, as well as on the scale of Northern Eurasia (Russia, Kazakhstan), this interval corresponds to the interval from the Cambrian to the Silurian period of the Paleozoic era.

• Paleotethys - this ocean is the prototype of Tethys in the Cenozoic era and the direct successor of the Prototethys ocean. The age of the ocean is 570-205 million years. According to the international stratigraphic scale, as well as on the scale of Northern Eurasia (Russia, Kazakhstan), this interval corresponds to the Paleozoic era and the Mesozoic era - from the Cambrian to the Late Triassic.

• Reikum - this ocean is the western part of Paleo-Tethys, but sometimes it is distinguished as an independent ocean. The age of the ocean is 480-425 million years. According to the international stratigraphic scale and the scale of Northern Eurasia, this interval corresponds to the period from the early Ordovician to the early Silurian.

• Ural - this ocean is the southern part of the Paleo-Asian Ocean, but sometimes it is distinguished as an independent ocean. The age of the ocean is 540-320 million years. According to the international stratigraphic scale and the scale of Northern Eurasia

• Mongolian-Okhotsk - this ocean is part of the Paleoasian Ocean, but separated into an independent ocean in the Middle Carboniferous. The age of the ocean is 325-155 million years. According to the international stratigraphic scale and the scale of Northern Eurasia, this interval corresponds to the period from the Middle Carboniferous to the Middle Triassic.

• Turkestan - this ocean is part of the Paleo-Asian Ocean, but sometimes it is distinguished as an independent ocean or combined with the Ural Ocean. The age of the ocean is 540-320 million years. According to the international stratigraphic scale and the scale of Northern Eurasia, this interval corresponds to the period from the Middle Cambrian to the Middle Carboniferous.

Mesozoic

• Panthalassa -2 - this super-ocean is the prototype of the modern Pacific Ocean and the direct successor of the Paleopacific super-ocean. This is the last world ocean on Earth. After the collapse of Pangea-2, the ocean broke up, and the Pacific Ocean formed in the Cenozoic era. The age of the ocean is 240-160 million years. According to the international stratigraphic scale and the scale of Northern Eurasia (Russia, Kazakhstan), this interval corresponds to the period from the Middle Triassic to the Late Jurassic.

• Tethys - this ocean was located east of Pangea-2. Sometimes in different geological sources, Tethys in the Mesozoic era is called Neotethys. In the Paleozoic era, this ocean was part of the Paleo-Tethys, and in the Mesozoic era it separated into an independent ocean. The age of the ocean is 280-60 million years. According to the international stratigraphic scale and the scale of Northern Eurasia (Russia, Kazakhstan), this interval corresponds to the period from the early Permian to the Paleocene.

see also

Write a review on the article "Ancient Oceans"

Literature

• N. V. Koronovsky, V. E. Khain, N. A. Yasamanov. Historical geology: a textbook for students. higher textbook institutions - 2nd ed., revised. and additional - M.: Publishing Center "Academy", 2006.

An excerpt characterizing the ancient oceans

- What? To whom?... You're kidding! shouted the Count, suddenly blushing apoplectically on his neck and the back of his head, as old people blush.
“I promised to pay tomorrow,” Nikolai said.
“Well!” said the old count, spreading his arms and sank helplessly on the sofa.
- What to do! Who hasn't this happened to? - said the son in a cheeky, bold tone, while in his soul he considered himself a scoundrel, a scoundrel who could not atone for his crime all his life. He would like to kiss his father's hands, on his knees to ask for his forgiveness, and he casually and even rudely said that this happens to everyone.
Count Ilya Andreich lowered his eyes on hearing these words of his son and hurried, looking for something.
“Yes, yes,” he said, “it’s hard, I’m afraid, it’s hard to get ... with anyone! yes, with whom it has not happened ... - And the count glanced at his son's face and went out of the room ... Nikolai was preparing to fight back, but did not expect this at all.
- Daddy! pa ... hemp! he shouted after him, sobbing; forgive me! And, seizing his father's hand, he pressed his lips to it and wept.

While the father was explaining himself to his son, an equally important explanation was taking place between the mother and her daughter. Natasha, excited, ran to her mother.
- Mom! ... Mom! ... he made me ...
- What did you do?
- Made an offer. Mum! Mum! she screamed. The Countess could not believe her ears. Denisov made an offer. To whom? This tiny girl Natasha, who until recently played with dolls and now still took lessons.
- Natasha, full of nonsense! she said, still hoping it was a joke.
- Well, nonsense! “I’m talking to you,” Natasha said angrily. - I came to ask what to do, and you tell me: "nonsense" ...
The countess shrugged.
- If it is true that Monsieur Denisov proposed to you, then tell him that he is a fool, that's all.
“No, he’s not a fool,” Natasha said offendedly and seriously.
- Well, what do you want? You are all in love these days. Well, in love, so marry him! said the Countess, laughing angrily. - With God!
“No, mother, I am not in love with him, I must not be in love with him.
“Well, just tell him that.
- Mom, are you angry? Don't be angry, my dear, what am I to blame for?
“No, what is it, my friend? If you want, I'll go and tell him, - said the countess, smiling.
- No, I myself, just teach. Everything is easy for you,” she added, answering her smile. “And if you saw how he told me this!” After all, I know that he did not want to say this, but he accidentally said it.
- Well, you still have to refuse.
- No, you don't have to. I feel so sorry for him! He is so cute.
Well, take the offer. And then it’s time to get married, ”the mother said angrily and mockingly.
“No, Mom, I feel so sorry for him. I don't know how I will say.
“Yes, you don’t have anything to say, I’ll say it myself,” said the countess, indignant at the fact that they dared to look at this little Natasha as a big one.
“No, no way, I’m on my own, and you listen at the door,” and Natasha ran through the living room into the hall, where Denisov was sitting on the same chair, at the clavichord, covering his face with his hands. He jumped up at the sound of her light footsteps.
- Natalie, - he said, approaching her with quick steps, - decide my fate. She is in your hands!
"Vasily Dmitritch, I'm so sorry for you!... No, but you're so nice... but don't... it's... but I'll always love you like that."
Denisov bent over her hand, and she heard strange sounds, incomprehensible to her. She kissed him on his black, matted, curly head. At that moment, the hasty noise of the countess's dress was heard. She approached them.
“Vasily Dmitritch, I thank you for the honor,” said the countess in an embarrassed voice, but which seemed strict to Denisov, “but my daughter is so young, and I thought that you, as a friend of my son, would first turn to me. In that case, you would not put me in the need for a refusal.
“Mr. Athena,” Denisov said with downcast eyes and a guilty look, he wanted to say something else and stumbled.
Natasha could not calmly see him so miserable. She began to sob loudly.
“Mr. Athena, I am guilty before you,” Denisov continued in a broken voice, “but know that I idolize your daughter and your entire family so much that I will give two lives ...” He looked at the countess and, noticing her stern face ... “Well, goodbye, Mrs. Athena,” he said, kissed her hand and, without looking at Natasha, left the room with quick, decisive steps.

The next day, Rostov saw off Denisov, who did not want to stay in Moscow for another day. Denisov was seen off at the gypsies by all his Moscow friends, and he did not remember how he was put into the sledge and how the first three stations were taken.
After Denisov's departure, Rostov, waiting for the money that the old count could not suddenly collect, spent another two weeks in Moscow, without leaving home, and mainly in the young ladies' room.
Sonya was more tender and devoted to him than before. She seemed to want to show him that his loss was a feat for which she now loves him all the more; but Nicholas now considered himself unworthy of her.
He filled the girls' albums with poems and notes, and without saying goodbye to any of his acquaintances, finally sending all 43 thousand and receiving Dolokhov's receipt, he left at the end of November to catch up with the regiment, which was already in Poland.

After his explanation with his wife, Pierre went to Petersburg. There were no horses at the station in Torzhok, or the caretaker did not want them. Pierre had to wait. Without undressing, he lay down on a leather sofa in front of a round table, put his big feet in warm boots on this table and thought.
- Will you order the suitcases to be brought in? Make a bed, would you like some tea? the valet asked.
Pierre did not answer, because he did not hear or see anything. He had been thinking at the last station and still kept thinking about the same thing - about such an important thing that he did not pay any attention to what was going on around him. He was not only not interested in the fact that he would arrive later or earlier in Petersburg, or whether he would or would not have a place to rest at this station, but all the same, in comparison with the thoughts that occupied him now, whether he would stay for a few hours or a lifetime at that station.
The caretaker, caretaker, valet, a woman with Torzhkov sewing came into the room, offering their services. Pierre, without changing his position of his raised legs, looked at them through his glasses, and did not understand what they might need and how they could all live without resolving the issues that occupied him. And he was always occupied with the same questions from the very day he returned from Sokolniki after the duel and spent the first, painful, sleepless night; only now, in the solitude of the journey, they took possession of it with particular force. Whatever he began to think about, he returned to the same questions that he could not solve, and could not stop asking himself. It was as if the main screw on which his whole life rested was curled up in his head. The screw did not go further in, did not go out, but spun, without grabbing anything, all on the same groove, and it was impossible to stop turning it.
The superintendent entered and humbly began to ask his excellency to wait only two hours, after which he would give courier for his excellency (what will be, will be). The caretaker obviously lied and only wanted to get extra money from the traveler. “Was it bad or good?” Pierre asked himself. “It’s good for me, it’s bad for another passing by, but it’s inevitable for him, because he has nothing to eat: he said that an officer beat him up for this. And the officer nailed him because he had to go sooner. And I shot Dolokhov because I considered myself insulted, and Louis XVI was executed because he was considered a criminal, and a year later those who executed him were killed, also for something. What's wrong? What well? What should you love, what should you hate? Why live, and what am I? What is life, what is death? What power governs everything?” he asked himself. And there was no answer to any of these questions, except for one, not a logical answer, not at all to these questions. This answer was: “If you die, everything will end. You will die and you will know everything, or you will stop asking.” But it was also scary to die.
The Torzhkovskaya tradeswoman offered her goods in a shrill voice, and especially goat shoes. “I have hundreds of rubles, which I have nowhere to put, and she stands in a torn fur coat and looks timidly at me,” thought Pierre. And why do we need this money? Precisely for one hair, this money can add to her happiness, peace of mind? Can anything in the world make her and me less subject to evil and death? Death, which will end everything and which must come today or tomorrow - all the same in a moment, in comparison with eternity. And he again pressed the screw, which was not grasping anything, and the screw was still spinning in the same place.
His servant handed him a book of the novel, cut in half, in letters m me Suza. [Madame Susa.] He began to read about the suffering and virtuous struggle of some Amelie de Mansfeld. [to Amalia Mansfeld.] And why did she fight her seducer, he thought, when she loved him? God could not put into her soul aspirations contrary to His will. My ex-wife didn't fight and maybe she was right. Nothing has been found, Pierre told himself again, nothing has been invented. We can only know that we know nothing. And this is the highest degree of human wisdom.”
Everything in him and around him seemed to him confused, meaningless and disgusting. But in this very disgust for everything around him, Pierre found a kind of annoying pleasure.
“I dare to ask Your Excellency to make room for a little one, here for them,” said the caretaker, entering the room and leading another, who was stopped for lack of horses, passing by. The passer-by was a squat, broad-boned, yellow, wrinkled old man with overhanging gray eyebrows over shining, indefinite grayish eyes.

Even Leonardo da Vinci found fossilized shells of marine organisms on the tops of the Alps and came to the conclusion that there used to be a sea on the site of the highest ridges of the Alps. Later, marine fossils were found not only in the Alps, but also in the Carpathians, the Caucasus, the Pamirs, and the Himalayas. Indeed, the main mountain system of our time - the Alpine-Himalayan belt - was born from the ancient sea. At the end of the last century, the contour of the area covered by this sea became clear: it stretched between the Eurasian continent in the north and Africa and Hindustan in the south. E. Suess, one of the greatest geologists of the end of the last century, called this space the Tethys Sea (in honor of Thetis, or Tethys, the sea goddess).

A new turn in the idea of ​​Tethys came at the beginning of this century, when A. Wegener, the founder of the modern theory of continental drift, made the first reconstruction of the Late Paleozoic supercontinent Pangea. As you know, he pushed Eurasia and Africa to North and South America, combining their coasts and completely closing the Atlantic Ocean. At the same time, it was discovered that, closing the Atlantic Ocean, Eurasia and Africa (together with Hindustan) diverge to the sides and between them, as it were, a void appears, a gaping several thousand kilometers wide. Of course, A. Wegener immediately noticed that the gap corresponds to the Tethys Sea, but its dimensions corresponded to those of the ocean, and one should have spoken of the Tethys Ocean. The conclusion was obvious: as the continents drifted, as Eurasia and Africa moved away from America, a new ocean opened up - the Atlantic and at the same time the old ocean - Tethys closed (Fig. 1). Therefore, the Tethys Sea is a vanished ocean.

This schematic picture, which emerged 70 years ago, has been confirmed and detailed in the last 20 years on the basis of a new geological concept that is now widely used in studying the structure and history of the Earth - lithospheric plate tectonics. Let us recall its main provisions.

The upper solid shell of the Earth, or the lithosphere, is divided by seismic belts (95% of earthquakes are concentrated in them) into large blocks or plates. They cover the continents and oceanic spaces (today there are 11 large plates in total). The lithosphere has a thickness of 50-100 km (under the ocean) to 200-300 km (under the continents) and rests on a heated and softened layer - the asthenosphere, along which plates can move in a horizontal direction. In some active zones - in the mid-ocean ridges - lithospheric plates diverge to the sides at a speed of 2 to 18 cm / year, making room for the uplift of basalts - volcanic rocks melted from the mantle. Basalts, solidifying, build up the divergent edges of the plates. The process of spreading the plates is called spreading. In other active zones - in deep-sea trenches - lithospheric plates approach each other, one of them "dives" under the other, going down to depths of 600-650 km. This process of submerging plates and absorbing them into the Earth's mantle is called subduction. Above the subduction zones, extended belts of active volcanoes of a specific composition (with a lower content of silica than in basalts) arise. The famous ring of fire of the Pacific Ocean is located strictly above the subduction zones. Catastrophic earthquakes recorded here are caused by the stresses necessary to pull the lithospheric plate down. Where plates approaching each other carry continents that are not capable of sinking into the mantle due to their lightness (or buoyancy), a collision of continents occurs and mountain ranges arise. The Himalayas, for example, were formed during the collision of the continental block of Hindustan with the Eurasian continent. The rate of convergence of these two continental plates is now 4 cm/year.

Since the lithospheric plates are rigid in the first approximation and do not undergo significant internal deformations during their movement, a mathematical apparatus can be applied to describe their movements on the earth's sphere. It is not complicated and is based on L. Euler's theorem, according to which any movement along the sphere can be described as rotation around an axis passing through the center of the sphere and intersecting its surface at two points or poles. Therefore, in order to determine the movement of one lithospheric plate relative to another, it is sufficient to know the coordinates of the poles of their rotation relative to each other and the angular velocity. These parameters are calculated from the values ​​of directions (azimuths) and linear velocities of plate movements at specific points. As a result, for the first time, a quantitative factor was introduced into geology, and it began to move from a speculative and descriptive science into the category of exact sciences.

The above remarks are necessary in order for the reader to further understand the essence of the work done jointly by Soviet and French scientists on the Tethys project, which was carried out under the agreement on Soviet-French cooperation in the study of the oceans. The main goal of the project was to restore the history of the disappeared Tethys Ocean. On the Soviet side, the Institute of Oceanology named after A.I. P. P. Shirshov Academy of Sciences of the USSR. Corresponding members of the USSR Academy of Sciences A. S. Monin and A. P. Lisitsyn, V. G. Kazmin, I. M. Sborshchikov, L. A. Savostii, O. G. Sorokhtin and the author of this article took part in the research. Employees of other academic institutions were involved: D. M. Pechersky (O. Yu. Schmidt Institute of Physics of the Earth), A. L. Knipper and M. L. Bazhenov (Geological Institute). Great assistance in the work was provided by employees of the Geological Institute of the Academy of Sciences of the GSSR (Academician of the Academy of Sciences of the GSSR G. A. Tvalchrelidze, Sh. and M. I. Satian), Faculty of Geology, Moscow State University (Academician of the Academy of Sciences of the USSR V.: E. Khain, N. V. Koronovsky, N. A. Bozhko and O. A. | Mazarovich).

From the French side, the project was headed by one of the founders of the theory of plate tectonics, K. Le Pichon (University named after Pierre and Marie Curie in Paris). Experts in the geological structure and tectonics of the Tethys belt took part in the research: J. Derkur, L.-E. Ricou, J. Le Priviere and J. Jeyssan (University named after Pierre and Marie Curie), J.-C. Si-boué (Center for Oceanographic Research in Brest), M. Westphal and J.P. Lauer (University of Strasbourg), J. Boulin (University of Marseille), B. Bijou-Duval (State Oil Company).

The research included joint expeditions to the Alps and the Pyrenees, and then to the Crimea and the Caucasus, laboratory processing and synthesis of materials at the University. Pierre and Marie Curie and at the Institute of Oceanology of the USSR Academy of Sciences. The work was started in 1982 and completed in 1985. Preliminary results were reported at the XXVII session of the International Geological Congress, held in Moscow in 1984. The results of the joint work were summed up in a special issue of the international journal "Tectonophysics" in 1986. An abbreviated version of the report on published in French in 1985 in the Bulletin societe de France, in Russian was published The History of the Tethys Ocean.

The Soviet-French project "Tethys" was not the first attempt to restore the history of this ocean. It differed from the previous ones in the use of new, better quality data, in the significantly greater extent of the region under study - from Gibraltar to the Pamirs (and not from Gibraltar to the Caucasus, as it was before), and most importantly, in the involvement and comparison of materials from various independent sources. Three main groups of data were analyzed and taken into account during the reconstruction of the Tethys Ocean: kinematic, paleomagnetic and geological.

Kinematic data relate to the mutual movements of the main lithospheric plates of the Earth. They are entirely related to plate tectonics. Penetrating into the depths of geological time and successively moving Eurasia and Africa closer to North America, we obtain the relative positions of Eurasia and Africa and reveal the contour of the Tethys Ocean for each specific moment in time. Here a situation arises that seems paradoxical to a geologist who does not recognize plate mobilism and tectonics: in order to represent events, for example, in the Caucasus or in the Alps, it is necessary to know what happened thousands of kilometers from these areas in the Atlantic Ocean.

In the ocean, we can reliably determine the age of the basalt base. If we combine the same-age bottom bands that are symmetrically on different sides of the axis of the mid-ocean ridges, then we will obtain the parameters of plate movement, that is, the coordinates of the pole of rotation and the angle of rotation. The procedure for searching for parameters for the best combination of coeval bottom bands is now well developed and is carried out on a computer (a series of programs is available at the Institute of Oceanology). The accuracy of determining the parameters is very high (usually fractions of a degree of a great circle arc, that is, the error is less than 100 km), and the accuracy of reconstructions of the former position of Africa relative to Eurasia is just as high. This reconstruction serves for each moment of geological time as a rigid frame, which should be taken as a basis for reconstructing the history of the Tethys Ocean.

The history of plate movement in the North Atlantic and the opening of the ocean in this place can be divided into two periods. In the first period, 190-80 million years ago, Africa separated from the united North America and Eurasia, the so-called Laurasia. Prior to this split, the Tethys Ocean had a wedge-shaped outline, expanding with a bell to the east. Its width in the region of the Caucasus was 2500 km, and on the traverse of the Pamirs it was at least 4500 km. During this period, Africa shifted to the east relative to Laurasia, covering a total of about 2200 km. The second period, which began about 80 million years ago and continues to the present day, was associated with the division of Laurasia into Eurasia and North America. As a result, the northern edge of Africa along its entire length began to converge with Eurasia, which ultimately led to the closure of the Tethys Ocean.

The directions and speeds of Africa's movement relative to Eurasia did not remain unchanged throughout the Mesozoic and Cenozoic eras (Fig. 2). In the first period, in the western segment (west of the Black Sea), Africa moved (though at a low rate of 0.8–0.3 cm/year) to the southeast, allowing the young oceanic basin between Africa and Eurasia to open up.

80 million years ago, in the western segment, Africa began to move northward, and in recent times it has been moving northwest with respect to Eurasia at a rate of about 1 cm/year. In full accordance with this are folded deformations and the growth of mountains in the Alps, Carpathians, Apennines. In the eastern segment (in the region of the Caucasus), Africa began to approach Eurasia 140 million years ago, and the rate of approach fluctuated noticeably. Accelerated approach (2.5-3 cm/year) refers to the intervals 110-80 and 54-35 million years ago. It was during these intervals that intense volcanism was noted in the volcanic arcs of the Eurasian margin. The movement slowed down (up to 1.2-11.0 cm/year) in the intervals of 140-110 and 80-54 million years ago, when stretching took place in the rear of the volcanic arcs of the Eurasian margin and deep-water basins of the Black Sea were formed. The minimum approach rate (1 cm/year) refers to 35-10 million years ago. Over the past 10 million years in the Caucasus region, the rate of convergence of plates has increased to 2.5 cm / year due to the fact that the Red Sea began to open, the Arabian Peninsula broke away from Africa and began to move north, pressing its protrusion into the edge of Eurasia. It is no coincidence that the mountain ranges of the Caucasus grew on the top of the Arabian ledge. The paleomagnetic data used in the reconstruction of the Tethys Ocean are based on measurements of the remanent magnetization of rocks. The fact is that many rocks, both igneous and sedimentary, at the time of their formation were magnetized in accordance with the orientation of the magnetic field that existed at that time. There are methods that allow you to remove layers of later magnetization and establish what the primary magnetic vector was. It should be directed to the paleomagnetic pole. If the continents do not drift, then all vectors will be oriented in the same way.

Back in the 50s of our century, it was firmly established that within each individual continent, paleomagnetic vectors are indeed oriented in parallel and, although they are not elongated along modern meridians, are still directed to one point - the paleomagnetic pole. But it turned out that different continents, even nearby ones, are characterized by completely different orientation of the vectors, that is, the continents have different paleomagnetic poles. This alone has given rise to the assumption of large-scale continental drift.

In the Tethys belt, the paleomagnetic poles of Eurasia, Africa, and North America also do not coincide. For example, for the Jurassic period, the paleomagnetic poles have the following coordinates: near Eurasia - 71 ° N. w „ 150 ° in. d. (region of Chukotka), near Africa - 60 ° N. latitude, 108° W (region of Central Canada), near North America - 70 ° N. latitude, 132° E (the area of ​​the mouth of the Lena). If we take the parameters of plate rotation relative to each other and, say, move the paleomagnetic poles of Africa and North America together with these continents towards Eurasia, then a striking coincidence of these poles will be revealed. Accordingly, the paleomagnetic vectors of all three continents will be oriented subparallel and directed to one point - a common paleomagnetic pole. This kind of comparison of kinematic and paleomagnetic data was made for all time intervals from 190 million years ago to the present. There was always a good match; by the way, it is a reliable evidence of the reliability and accuracy of paleogeographic reconstructions.

The main continental plates - Eurasia and Africa - bordered the Tethys Ocean. However, inside the ocean, there were undoubtedly smaller continental or other blocks, as now, for example, inside the Indian Ocean there is a microcontinent of Madagascar or a small continental block of the Seychelles. Thus, inside the Tethys there were, for example, the Transcaucasian massif (the territory of the Rion and Kura depressions and the mountain bridge between them), the Daralagez (South Armenian) block, the Rhodope massif in the Balkans, the Apulia massif (covering most of the Apennine Peninsula and the Adriatic Sea). Paleomagnetic measurements within these blocks are the only quantitative data that allow us to judge their position in the Tethys Ocean. Thus, the Transcaucasian massif was located near the Eurasian margin. The small Daralagez block appears to be of southern origin and was previously annexed to Gondwana. The Apulian massif did not shift much in latitude relative to Africa and Eurasia, but in the Cenozoic it was rotated counterclockwise by almost 30°.

The geological group of data is the most abundant, since geologists have been studying the mountain belt from the Alps to the Caucasus for a good hundred and fifty years. This group of data is also the most controversial, since it can be least of all applied to a quantitative approach. At the same time, geological data in many cases are decisive: it is geological objects - rocks and tectonic structures - that were formed as a result of the movement and interaction of lithospheric plates. In the Tethys belt, geological materials have made it possible to establish a number of essential features of the Tethys paleoocean.

Let's start with the fact that it was only by the distribution of marine Mesozoic (and Cenozoic) deposits in the Alpine-Himalayan belt that the existence of the Tethys sea or ocean in the past became obvious. Tracing different geological complexes over the area, it is possible to determine the position of the seam of the Tethys ocean, that is, the zone along which the continents that framed Tethys converged at their edges. Of key importance are the outcrops of rocks of the so-called ophiolite complex (from the Greek ocpir ​​- a snake, some of these rocks are called serpentines). Ophiolites consist of heavy rocks of mantle origin, depleted in silica and rich in magnesium and iron: peridotites, gabbro and basalts. Such rocks form the bedrock of modern oceans. Given this, 20 years ago, geologists came to the conclusion that ophiolites are the remains of the crust of ancient oceans.

Ophiolites of the Alpine-Himalayan belt mark the bed of the Tethys Ocean. Their outcrops form a winding strip along the strike of the entire belt. They are known in the south of Spain, on the island of Corsica, stretching in a narrow strip along the central zone of the Alps, continuing into the Carpathians. Large tectonic scales of ophiolites were found in the Dealer Alps in Yugoslavia and Albania, in the mountain ranges of Greece, including the famous Mount Olympus. The outcrops of ophiolites form an arc facing south between the Balkan Peninsula and Asia Minor, and then are traced in Southern Turkey. Ophiolites are beautifully exposed in our country in the Lesser Caucasus, on the northern shore of Lake Sevan. From here they extend to the Zagros Range and into the mountains of Oman, where ophiolite plates are pushed over the shallow sediments of the margin of the Arabian Peninsula. But even here the ophiolite zone does not end, it turns to the east and, following parallel to the coast of the Indian Ocean, goes further northeast to the Hindu Kush, the Pamirs and the Himalayas. Ophiolites have different ages - from Jurassic to Cretaceous, but everywhere they are relics of the earth's crust of the Mesozoic Tethys ocean. The width of the ophiolite zones is measured by several tens of kilometers, while the original width of the Tethys Ocean was several thousand kilometers. Consequently, during the approach of the continents, almost the entire oceanic crust of Tethys went into the mantle in the zone (or zones) of subduction along the edge of the ocean.

Despite the small width, the ophiolite, or main, suture of the Tethys separates two provinces that are sharply different in geological structure.

For example, among the Upper Paleozoic deposits accumulated 300-240 million years ago, north of the suture, continental sediments predominate, some of which was deposited in desert conditions; while to the south of the suture, thick strata of limestones, often reefs, are widespread, marking a vast shelf sea in the equator region. The change of Jurassic rocks is just as striking: detrital, often coal-bearing, deposits north of the seam again oppose limestone south of the seam. The seam separates, as geologists say, different facies (conditions for the formation of sediments): the Eurasian temperate climate from the Gondwanan equatorial climate. Crossing the ophiolite seam, we get, as it were, from one geological province to another. To the north of it we find large granite massifs surrounded by crystalline schists and a series of folds that arose at the end of the Carboniferous period (about 300 million years ago), to the south - layers of sedimentary rocks of the same age occur in accordance with and without any signs of deformation and metamorphism . It is clear that the two margins of the Tethys Ocean - the Eurasian and the Gondwana - differed sharply from each other both in their position on the earth's sphere and in their geological history.

Finally, we note one of the most significant differences between the areas north and south of the ophiolite suture. To the north of it are belts of volcanic rocks of the Mesozoic and Early Cenozoic age, formed over 150 million years: from 190 to 35-40 million years ago. The volcanic complexes in the Lesser Caucasus are especially well traced: they stretch in a continuous strip along the entire ridge, going west to Turkey and further to the Balkans, and east to the Zagros and Elburs ranges. The composition of the lavas has been studied in great detail by Georgian petrologists. They found that the lavas are almost indistinguishable from the lavas of modern island arc volcanoes and active margins that make up the ring of fire of the Pacific Ocean. Recall that the volcanism of the rim of the Pacific Ocean is associated with the subduction of the oceanic crust under the continent and is confined to the boundaries of the convergence of lithospheric plates. This means that in the Tethys belt, volcanism similar in composition marks the former boundary of convergence of plates, on which subduction of the oceanic crust took place. At the same time, south of the ophiolite suture, there are no coeval volcanic manifestations; throughout the Mesozoic era and during most of the Cenozoic era, shallow-water shelf sediments, mainly limestone, were deposited here. Consequently, the geological data provide solid evidence that the margins of the Tethys Ocean were fundamentally different in tectonic nature. The northern, Eurasian margin, with volcanic belts constantly forming at the boundary of the convergence of lithospheric plates, was, as geologists say, active. The southern, Gondwana margin, devoid of volcanism and occupied by a vast shelf, calmly passed into the deep basins of the Tethys Ocean and was passive. Geological data, and primarily materials on volcanism, make it possible, as we see, to restore the position of the former boundaries of the lithospheric plates and outline ancient subduction zones.

The foregoing does not exhaust all the factual material that must be analyzed for the reconstruction of the disappeared Tethys Ocean, but I hope this is enough for the reader, especially far from geology, to understand the basis of the constructions made by Soviet and French scientists. As a result, color paleogeographic maps were compiled for nine moments of geological time from 190 to 10 million years ago. On these maps, the position of the main continental plates - the Eurasian and African (as parts of Gondwana) was restored using kinematic data, the position of the microcontinents inside the Tethys Ocean was determined, the boundary of the continental and oceanic crust was outlined, the distribution of land and sea was shown, and paleolatitudes were calculated (from paleomagnetic data)4 . Particular attention is paid to the reconstruction of the boundaries of lithospheric plates - spreading zones and subduction zones. The displacement vectors of the main plates are also calculated for each moment of time. On fig. 4 shows diagrams compiled from color maps. To make clear the prehistory of Tethys, they also added a diagram of the location of continental plates at the end of the Paleozoic (Late Permian era, 250 million years ago).

In the Late Paleozoic (see Fig. 4, a), the Paleo-Tethys ocean extended between Eurasia and Gondwana. Already at that time, the main trend of tectonic history was determined - the existence of an active margin in the north of the Paleo-Tethys and a passive one in the south. From the passive margin at the beginning of the Permian period, relatively large continental masses were split off - Iranian, Afghan, Pamir, which began to move, crossing the Paleo-Tethys, to the north, to the active Eurasian margin. The Paleo-Tethys oceanic bed in the front of drifting microcontinents was gradually absorbed in the subduction zone near the Eurasian margin, and in the rear of the microcontinents, between them and the Gondwana passive margin, a new ocean opened - the Mesozoic Tethys proper, or Neo-Tethys.

In the Early Jurassic (see Fig. 4b), the Iranian microcotinent joined the Eurasian margin. When they collided, a folded zone arose (the so-called Cimmerian folding). In the Late Jurassic, 155 million years ago, the opposition of the Eurasian active and Gondwana passive margins was clearly marked. At that time, the width of the Tethys Ocean was 2500-3000 km, that is, it was the same as the width of the modern Atlantic Ocean. The distribution of Mesozoic ophiolites made it possible to mark the spreading axis in the central part of the Tethys Ocean.

In the Early Cretaceous (see Fig. 4, c), the African plate - the successor to the Gondwana that had disintegrated by that time - moved towards Eurasia in such a way that in the west of the Tethys the continents parted somewhat and a new ocean basin arose there, while in the eastern part of the continents they converged and the bed of the Tethys ocean was absorbed under the Lesser Caucasian volcanic arc.

At the end of the Early Cretaceous (see Fig. 4, d), the oceanic basin in the west of the Tethys (sometimes called the Mesogea, and its remains are the modern deep-water basins of the Eastern Mediterranean) ceased to open, and in the east of the Tethys, judging by the dating of the ophiolites of Cyprus and Oman , the active stage of spreading was completed. In general, the width of the eastern part of the Tethys Ocean decreased to 1500 km by the middle of the Cretaceous at the traverse of the Caucasus.

By the Late Cretaceous, 80 million years ago, there was a rapid reduction in the size of the Tethys Ocean: the width of the strip with oceanic crust at that time was no more than 1000 km. In some places, as in the Lesser Caucasus, collisions of microcontinents with an active margin began, and the rocks underwent deformation, accompanied by significant displacements of tectonic sheets.

At the turn of the Cretaceous and Paleogene (see Fig. 4, e), at least three important events took place. First, ophiolite plates, torn off the oceanic crust of Tethys, were pushed over the passive margin of Africa by a wide front.

There are places on Earth that have remained unchanged for millions of years. When you get to such places, you willy-nilly imbued with reverence for time and feel like just a grain of sand.

This review contains the oldest geological antiquities of our planet, many of which are still a mystery to scientists today.

1. The oldest surface

1.8 million years

In Israel, one of the local desert areas looks the same as almost two million years ago. Scientists believe that this plain remained dry and extremely flat for such a long time due to the fact that the climate did not change here and there was no geological activity. According to those who have been here, you can look at the endless barren plain almost forever ... if you can stand the wild heat well.

2. The oldest ice

15 million years

At first glance, the McMurdo Dry Valleys in Antarctica appear to be ice-free. Their eerie "Martian" landscapes are made up of bare rocks and a thick layer of dust. There are also remnants of ice about 15 million years old. Moreover, a mystery is connected with this most ancient ice on the planet. For millions of years the valleys have remained stable and unchanged, but in recent years they have begun to thaw. For reasons unknown, the Garwood Valley experienced unusually hot weather for Antarctica. One of the glaciers began to melt intensively for at least 7000 years. Since then, it has already lost a huge amount of ice and there is no sign that this will stop.

3. Desert

55 million years

The Namib Desert in Africa is officially the oldest "pile of sand" in the world. Among its dunes, you can find mysterious “fairy circles” and desert velvichia plants, some of which are 2,500 years old. This desert has not seen surface water for 55 million years. However, its origins go back to the Western Gondwana continental break that occurred 145 million years ago.

4. Oceanic crust

340 million years

The Indian and Atlantic Oceans were far from the first. Scientists believe they have found traces of the primordial Tethys Ocean in the Mediterranean Sea. It is very rare that the seafloor crust can be dated to more than 200 million years, as it is in constant motion and new strata rise to the surface. A site in the Mediterranean has escaped normal geological recycling and has been scanned for a record age of 340 million years ago. If this is indeed part of Tethys, then this is the first evidence that the ancient ocean existed earlier than previously thought.

5. Reefs created by animals

548 million years

The oldest reef is not just one or two sprigs of corals. This is a massive petrified “network” that stretches for 7 km. And it is in Africa. This miracle of nature was created in Namibia by claudins - the first creatures with skeletons. Extinct rod-shaped animals made their own cement from calcium carbonate, like modern corals, and used it to stick together. Although very little is known about them today, scientists believe that claudins combined to protect themselves from predators.

6. Mount Roraima

2 billion years

Three countries border this mountain: Guyana, Brazil and Venezuela. Its huge flat top is a popular tourist attraction, and when it rains heavily, the water from the mountain cascades down to the plateau below. The sight of Roraima inspired Sir Arthur Conan Doyle so much that he wrote his famous classic The Lost World. At the same time, few tourists know that Mount Roraima is one of the most ancient formations in the world.

7. Water

2.64 billion years

At a depth of 3 kilometers in a Canadian mine lies what used to be the prehistoric ocean floor. After scientists took samples from a "pocket" of water found in a mine, they were shocked when the liquid turned out to be the oldest H2O on the planet. This water is older than even the first multicellular life.

8. Impact crater

3 billion years

A huge meteorite could have “knocked out” a significant piece of Greenland a long time ago. If this is proven, then the Greenland crater will “move off the throne” the current champion - the 2 billion year old Vredefort crater in South Africa. Initially, the diameter of the crater was up to 500 kilometers. To this day, it still shows evidence of impact, such as eroded rocks at the rims of the crater and molten mineral formations. There is also ample evidence that sea water gushed into the freshly formed crater and a gigantic amount of steam altered the chemistry of the environment. If such a behemoth hits the Earth today, the human race will face the threat of extinction.

9 Tectonic Plates

3.8 billion years

The outer layer of the Earth is made up of several "plates" that are stacked together like puzzle pieces. Their movements form the appearance of the world, and these “plates” are known as tectonic plates. On the southwestern coast of Greenland, traces of ancient tectonic activity have been found. 3.8 billion years ago, colliding plates “squeezed out” a “cushion” of lava.

10. Earth

4.5 billion years

Scientists believe that a part of the Earth, which the planet was at birth, may have fallen into their hands. In Baffin Island in the Canadian Arctic, volcanic rocks have been found that formed before the earth's crust formed. This discovery may finally reveal what happened to the globe before it became solid. These rocks contained a previously unseen combination of chemical elements - lead, neodymium and extremely rare helium-3.

460 million years ago- At the end of the Ordovician period (Ordovician), one of the ancient oceans - Iapetus - began to close and another ocean appeared - Rhea. These oceans were located on both sides of a narrow strip of land that was near the South Pole and today forms the east coast of North America. Small fragments were breaking off from the supercontinent Gondwana. The rest of Gondwana moved south, so that what is now North Africa was right at the South Pole. The area of ​​many continents increased; high volcanic activity added new land areas to the east coast of Australia, to Antarctica and South America.

In Ordovician, ancient oceans separated 4 barren continents - Laurentia, Baltica, Siberia and Gondwana. The end of Ordovician was one of the coldest periods in the history of the Earth. Ice covered much of southern Gondwana. In the Ordovician period, as well as in the Cambrian, bacteria dominated. Blue-green algae continued to develop. Calcareous green and red algae, which lived in warm seas at depths of up to 50 m, reach lush development. The existence of terrestrial vegetation in the Ordovician period is evidenced by the remains of spores and rare finds of imprints of stems, probably belonging to vascular plants. Of the animals of the Ordovician period, only the inhabitants of the seas, oceans, as well as some representatives of fresh and brackish waters are well known. There were representatives of almost all types and most classes of marine invertebrates. At the same time, jawless fish-like fish appeared - the first vertebrates.

DURING THE ORDOVICAN PERIOD, LIFE WAS INCREASED BUT THEN CLIMATE CHANGE DESTROYED THE HABITATS OF MANY SPECIES OF LIVING THINGS.

During the Ordovician period, the rate of global tectonic changes increased. During the 50 million years that the Ordovician lasted, from 495 to 443 million years ago, Siberia and the Baltic moved northward, the Iapetus Ocean began to close, and the Rhea Ocean gradually opened in the south. The Southern Hemisphere was still dominated by the Gondwana supercontinent, with North Africa located at the South Pole.

Almost all of our knowledge of the Ordovician climate changes and the position of the continents is based on the fossil remains of creatures that lived in the seas and oceans. In the Ordovician period, primitive plants, along with some small arthropods, had already begun to populate the land, but the bulk of life was still concentrated in the ocean.

In the Ordovician period, the first fish appeared, but most of the inhabitants of the sea remained small - few of them grew to a length of more than 4 -5 cm. The most common owners of shells were brachiopods similar to oysters, reaching a size of 2 - 3 cm. and over 12,000 fossil brachiopod species have been described. The shape of their shells changed depending on environmental conditions, so the fossil remains of brachiopods help to reconstruct the climate of ancient times.

The Ordovician period represented a turning point in the evolution of marine life. Many organisms have increased in size and learned to move faster. Of particular importance were jawless creatures called conodonts, extinct today, but widespread in the seas of the Ordovician period. They were close relatives of the first vertebrates. The appearance of the first fish-like jawless vertebrates was followed by the rapid evolution of the first shark-like vertebrates with jaws and teeth. This happened over 450 million years ago. It was during this period that animals first began to land on land.

In the Ordovician period, animals made their first attempts to reach land, but not directly from the sea, but through an intermediate stage - fresh water. These centimeter-wide parallel lines have been found in Ordovician sedimentary rocks of freshwater lakes in Northern England. Their age is 450 million years. Probably, they were left by an ancient arthropod - a creature with a segmented body, numerous jointed legs and exoske in the summer. It looked like modern centipedes. However, no fossil remains of this creature have been found so far.

The Ordovician seas were inhabited by numerous animals that differed sharply from the inhabitants of the ancient Cambrian seas. The formation of hard covers in many animals meant that they acquired the ability to rise above bottom sediments and feed in food-rich waters above the seabed. During the Ordovician and Silurian periods, more animals appeared that extract food from sea water. Among the most attractive are the sea lilies, which look like hard-shelled starfish on thin stalks, swaying in water currents. With long flexible rays covered with a sticky substance, sea lilies caught food particles from the water. Some species of such rays had up to 200. Sea lilies, like their stemless relatives - starfish, have successfully survived to this day.

SECTION 5

PALAEOZOIC

SILURIAN

(approximately from 443 million to 410 million years ago)

Silurian: the collapse of the continents

420 million years ago- If you look at our land from the poles, it becomes clear that in the Silurian period (Silur), almost all the continents lay in the Southern Hemisphere. The giant continent of Gondwana, which included present-day South America, Africa, Australia and India, was located at the South Pole. Avalonia - a continental fragment that represented most of the east coast of America - approached Laurentia, which later formed modern North America, and along the way closed the Iapetus Ocean. South of Avalonia, the Rhea Ocean appeared. Greenland and Alaska, today located near the North Pole, were near the equator during the Silurian period.

The boundary between the Ordovician and Silurian periods of the ancient history of the Earth was determined by geological strata near Dobslinn in Scotland. In the Silurian, this area was located on the very edge of the Baltic - a large island that also included Scandinavia and part of Northern Europe. The transition from earlier - Ordovician to later - Silurian layers corresponds to the boundary between the layers of sandstone and shale formed on the seabed.

During the Silurian period, Laurentia collides with the Baltic with the closure of the northern branch of the Iapetus Ocean and the formation of the "New Red Sandstone" continent. Coral reefs are expanding and plants are beginning to colonize barren continents. The lower limit of the Silurian is defined by a major extinction, which resulted in the disappearance of about 60% of the species of marine organisms that existed in the Ordovician, the so-called Ordovician-Silurian extinction.