Ocean tetis in the ancient world map. What does the name "tetis" mean?
The Mediterranean basin, to the system of which our seas belong, has become the cradle of European civilization. The history of the Mediterranean Sea, in the opinion of many scientists, can also become a "key" to the history of our planet, to the history of the origin of continents and oceans. A lot of hypotheses trying to explain the geological evolution of the Earth have been put forward in recent centuries. In principle, they can be divided into two groups. The first unites hypotheses explaining the history of the Earth by vertical movements of the crust - uplift of mountains, sinkholes of ocean troughs, formation of continents in place of sea depths, or, conversely, "oceanization" of the continental crust. The second group, in addition to these vertical movements of the crust, also presupposes horizontal ones, caused by the drift of continents, the expansion of the Earth, etc. - the theory of mobilism.
The ocean Tethys is given a large place precisely in the structures of the mobilists. At the end of the Paleozoic, about 200 million years ago, as suggested by the creator of this hypothesis, the German scientist Alfred Wegener, a single land mass, Pangea, surrounded by the Pacific Ocean, split into two super-continents: the northern one - Laurasia and the southern one - Gondwana. The "gap" between these super-continents, steadily expanding, gave rise to the Tethys Sea, a kind of single gulf that embraced the entire planet of the Panthalassa ocean. Then the split of Laurasia and Gondwana into separate continents began, the movement of continental plates became more complicated. As Europe, North America, India, Africa, Australia, Antarctica "dispersed", the Atlantic, Indian, Arctic oceans were formed - and at the same time the area of the Tethys Sea was shrinking. The majestic Alps, the Caucasus, the Pamirs, the Himalayan mountains, which were once the bottom of the Tethys, rose. And from the Tethys sea itself, only the Mediterranean and the Black Sea associated with it remained.
What then? And here we need to introduce one more concept - Pontida. According to the largest authorities in geology of the late XIX - early XX centuries E. Suess, F. Oswald, the best expert on the Black Sea N.I. Andrusov, President Geographical Society Academician L. S. Berg, the largest Soviet zoogeographer, Professor I. I. Puzanov, it existed on the site of the Black Sea basin until the end of the Pliocene, that is, about one or two million years ago. The mountainous Crimea at that time was the northernmost outskirts of Pontida and was connected by mainland land not only with Asia Minor, but also with the Balkan Peninsula and the Caucasus. In favor of this hypothesis, its supporters cited Interesting Facts associated not only with the geology of the Crimea, the Caucasus, the Balkans, Asia Minor, but also with the specific fauna and flora of the Crimean peninsula.
Pontida is a geological land that existed on the site of the Black Sea and connected the mountainous Crimea with Asia Minor - if it existed, then its death occurred long before the appearance of Homo sapiens, and long before the advent of modern Cenozoic era- tens of millions of years ago. The mountainous Crimea, which for a long time was an island, about 10 million years ago began to be populated by terrestrial animals and plants through land bridges - now appearing and then disappearing again. These bridges connected it not only with mainland Ukraine, but also with the north of the Balkan Peninsula, which determined the originality of the Crimean fauna and flora.
And if we talk about Pontida not geological or zoogeographic, but about the historical one, then first of all we should talk about the vast expanses of the Black Sea shelf. They were dry land in the era of the existence of Homo sapiens. And this land was inhabited by people of the Paleolithic, starting with the Neanderthals (traces of which were found in the mountainous Crimea, along with the remains of a wild horse and mammoth). Primitive people who did not know navigation, undoubtedly, got to the Crimea by land bridges from the regions of the Caucasus, the Balkans or the southwestern outskirts of the East European Plain.
The shallow-water shelf zone occupies almost the entire northwestern part of the Black Sea and significant areas of the southwestern part (its area is almost one fourth of the Black Sea area). It ends at a depth of 90-110 meters with a continental slope, steeply going down to the two-kilometer deep sea. In the era of the last glaciation, it was a plain along which rivers flowed, the channels of which became underwater valleys, continuing the valleys of modern terrestrial rivers. In the north-west of the Black Sea, where the mighty rivers Danube, Dniester, Southern Bug, Dnieper flow into, the shelf width reaches 200 and even 250 kilometers (off the coast of Asia Minor and the Caucasus, it is only a few kilometers, or even hundreds of meters). Once these rivers formed a single system - Paleo Danube, primitive people lived on the banks of the Paleo Danube rivers. Their sites are found on land, but they can also be on the shelf of the Black Sea.
“So what is the promised secret here?” The patient reader will ask. And it is simple and obvious. We live at the bottom of the Tethys Ocean. And this is especially striking when you look at the limestone cliffs of the Crimean cuestas, at the mountains in Novy Svet and Sudak - the former reefs of this ocean.
And when you look at the Karadag peaks and rocks, for some reason you think of a hypothetical Pontida. And also that we are pollen in the great picture of nature. What kind of kings are there ...
Sergey Tkachenko, "
It is perhaps no easier to convey in a nutshell what the Gobi Desert is than to say what color the motley carpet is. A week ago, Vladimir Yarmolyuk with his small detachment traveled across the sandy plain, where the only exception to the general monotony were the rare saxaul trunks with bare branches. And yesterday everything, as if by magic, changed: the detachment found itself in an oasis surrounded by low mountains - in a green valley, overgrown with grass and framed by a lilac bloom of tamarisk.
According to the calendar, September has come. The thermometer is still kept at the forty-degree mark. And although due to the exceptional dryness of the air, the heat here is not so exhausting (it is easy to breathe, in any case), all the same, the first thought of a traveler in Southern Mongolia - wherever he goes and wherever he stops - is, of course, about water.
There was no spring in the valley. Apparently dry. But in one place Yarmolyuk found wet ground and early in the morning began to dig a hole with the driver, hoping to quickly reach the water. When, in fact, little by little she began to gather at the bottom of the improvised well, it turned out that a strong hydrogen sulfide spirit emanated from her. However, this did not bother both of them in the least. They knew that after work, even such moisture would seem blessed, since everyone can really wash, or even (what the devil is not kidding!) Dive from head to toe, keeping intact the supply of drinking water brought with them.
Before Yarmolyuk, only a general reconnaissance was carried out in these areas. He should have found out the details of the structure of their bowels.
But the strange thing is, lately, looking through his sketches of maps, he no-no, and even remembered Priokhotye, which he studied several years ago, as a graduate student of Novosibirsk University. Some unexpected parallels and comparisons crept into his head, although he convinced himself that they were caused by purely random coincidences. Indeed, what similarities could there be between the Gobi Desert and the Magadan coast of the Sea of Okhotsk? Indeed, from the fact that here and there once volcanoes rumbled, absolutely nothing followed: you never know such places on Earth! He's probably just tired, and that's why in the local geological confusion he wants to see something familiar, so to speak, stereotypical ...
Now he was heading for a ridge that included several dark manes. Heavy, crowned with angular ridges, they resembled dormant dinosaurs, suggesting an encounter with something prehistoric.
In essence, for the sake of such meetings (and there were already many of them). Yarmolyuk roamed these homeless places for the third field season in a row. It was no coincidence that this belt attracted the attention of the joint Soviet-Mongolian scientific research geological expedition, which included Yarmolyuk's detachment. Ore deposits are usually associated with such areas.
But in order to understand what exactly such a belt can be rich in, one must first get to the bottom of a lot in its "biography". After all, what kind of "life" he lived, ultimately depended on what he "amassed" in his lifetime. So Yarmolyuk was digging, trying to recreate a more or less integral picture of the ancient Gobi volcanism.
At the foot of the nearest mane, Yarmolyuk got out of the car and, having agreed with the driver about the meeting point, moved up a steep slope, reminiscent of a puff pie cut, in which the multi-colored layers fit well together. Its lower part was composed of basalts. Then they seemed to be cut off. Then there were only liparites - the outpouring varieties of granite.
Heading here, Yarmolyuk expected to meet this contrasting neighborhood (basalt - liparite). He found it more than once, almost all over the waist. But it was precisely such a frequent repetition that puzzled him more and more - he did not understand its reasons. In addition, chemists, petrographers, paleobotanists unanimously testified that all volcanic rocks of southern Mongolia are close in age.
Maybe the contrasting neighborhood of basalt - liparite should have been considered just a play of nature? In that case, it was a strange "game". On the one hand, everything in it did not go according to the rules, since it turned out that from the same volcanoes, in the same epoch, either basalt or granite magma rose up, completely different in composition. On the other hand, there was still a strict order in the “game”. And Yarmolyuk already knew what its completion was. For example, he could, with a high degree of probability, assume that somewhere nearby he should meet another basalt field, which would overlap all these granite-type rocks that lay under his feet. And further. He may come across a fragment of an unusual crack here. crust, the so-called ring fault.
He was almost certain that this was exactly what would happen now. Therefore, when, having reached the very top, he did not find the expected basalt field, he began to look around in confusion, as if he could not find the thing left the day before in the coveted place.
And yet he found the "lost". Beyond the pass, a view of a narrow - no wider than a hundred meters - valley opened up. In a gentle arc, it covered the neighboring hill. Yarmolyuk's eye was already trained enough - characteristic omens did not escape his attention, indicating that the valley was part of that ring fault, which he expected to meet.
And on the other side of it, Yarmolyuk grabbed the second basalts. They really blocked liparites, as it should be according to the “rules of the game”.
In general, everything looked very much like he was dealing with another caldera ...
There is no consensus in science about the origin of calderas. But in the summer of 1883, a powerful explosion shook the island of Krakatoa in the Sunda Strait between Sumatra and Java: a volcano that had been silent for two hundred years came to life. In place of the destroyed part of Krakatoa, a depression with steep sides was formed - a caldera. Disappeared is unknown much more than twenty square kilometers of island land. Almost half a century later, in the middle of the caldera, a new small cone appeared above the water, called Anak-Krakatau ("Child of Krakatau").
Incidentally, the explosions of the Santorini volcano in the Aegean Sea north of Crete were even stronger, as can be judged at least by the fact that there the caldera, spread out on the site of the disappeared islands, occupied an area four times larger than in Krakatoa.
Even in connection with the explosion of Krakatoa, the geological world tried to find out the fate of the missing part of the island, since the share of its materials in the release products was surprisingly small. It was speculated that the central massif of the volcano did not fly up into the air, but plunged into an underground cavity that was empty after the eruption, and that it was from this that a depression was formed.
For many years this version has been questioned. Yarmolyuk, on the example of the Okhotsk calderas, proved its validity. Moreover, he managed to find out that external form the caldera is by no means accidental.
The secret was the ring faults. The catastrophic explosions of volcanoes are so strong that a crack is formed in the thickness of the earth's crust, which runs around the base of the cone, built by the previously erupted lava. And then all of it begins to settle into this giant "glass". This is how the first wall, bordering the caldera, is formed - its outer boundary.
From below, magma penetrates into the crack. If it does not even break out, it will still tightly seal the entire volcano until the forces for a new explosion are accumulated in the uncovered part of the chamber. When this happens, another ring fault will appear - of a smaller diameter.
These conclusions led to important practical considerations. For some minerals, for example, it is more expedient to search inside the caldera, near ring faults (where melts were introduced) and certainly not outside of it.
But this was not the only thing the young researcher was thinking about now. Calderas, in general, were the final stage of ancient volcanism - its extinction. It began with calm outpourings of basalts through linear (non-annular) cracks in the earth's crust. Only then did vents appear, and cones with craters, and explosions, and so on.
Among other things, there were also incomprehensible changes in the composition of magma. Yarmolyuk discovered granite-type rocks both in ring faults and in solidified lava flows. And at the last stage of eruptions, basalt covers invariably appeared again. In other words, it began with them, and ended with them.
Yes, the situation here in southern Mongolia is almost the same as in Priokhotye - sometimes down to the details. And only question marks follow from this. Why did the first basalts appear through short linear fractures? What explains such rhythmic and such abrupt changes in the composition of magmatic melts? Why, finally, are these contrasts especially characteristic of the final stage of volcanism and are often associated with calderas?
The questions are, in general, overtime, since they relate to problems that are by no means local in scope and occupy the minds of many scientists. Are they capable of him, a young candidate of sciences?
A year later, the Gobi desert appeared before Vladimir Yarmolyuk in a completely different, previously unknown guise.
He went south of the ridges where he had worked before. Before him suddenly opened the space of a huge, slightly hilly plain. She was so naked and boundless that it seemed that infinity begins from here.
There were surprises literally from the first runs.
Just beyond the ridge, nature has changed dramatically. Not a blade of grass around, one solid black rubble, which, flying out from under the wheels of the car, beat fractionally in its bottom. Against the sun, the surface of this rocky desert looked silvery gray; she blinded her eyes, as if she were covered with a layer of glass. Only occasionally in the distance did brown hills appear, similar to the burial mounds of some famous ancestors. And wherever you look, a haze rising from the incandescent gravel vibrates the air.
In the mountains left behind, there were unafraid hares, gazelles, even wild donkeys - kulans (animals are rare, few where preserved on Earth). And here everything seems to be extinct - neither a bird will fly by, nor a troublesome jerboa will not slip by. And no matter how much you roll - no well, no spring.
But the main surprise was ahead.
Having rushed from a hundred kilometers, Yarmolyuk noticed several stone pillars sticking out of the ground. He got out of the car and examined the strange hermits. Some were as tall as a man, while others were much taller. All are matte black. Time diligently polished them, giving them rounded shapes.
Now, wherever Yarmolyuk went, he bumped into these strange pillars everywhere. Where did they come from here? But it was enough to beat off a few samples (and this was done with difficulty, the stones were so dense) in order to understand: these were earth surface the so-called hyperbasites are more than outstanding rocks.
The importance of the meeting was so exceptional that, despite the lack of water nearby, Yarmolyuk camped for several days. His particular interest was explained by the following.
For a long time, a number of scientists have suggested that the Mediterranean, Black and Caspian Sea- relics of a once single large basin. The belief in his existence was so strong that he was even given a name - Tethys (after the Greek goddess, wife of the Ocean). Indeed, sedimentary rocks of precisely marine origin were often found in the territory stretching from the Pyrenees to the Himalayas and China. But was Tethys just a chain of shallow seas or a real ocean? This remained controversial.
What spoke in favor of Tethys' oceanic past? In some areas of the deep-sea bed of the Mediterranean, Black and Caspian Seas, as it turned out, to this day there is a transitional type of the earth's crust, a seemingly preserved junction between the shelf extension of the European continent and the bottom of the ancient ocean.
Findings in Cyprus were even more convincing. There, at the base of Mount Trudos, geologists discovered hyperbasites. That at one time became a real sensation: before, such rocks were dredged from the gorges of the mid-ocean ridges, located at great depths, from the gorges where the new crust is constantly being formed. Therefore, the mined blocks were considered samples of the material that composes the base of the ocean floor (and, according to some scientists, even the upper mantle of our planet).
And now hyperbasites again! And where? In the center of the Asian mainland massif - in the Gobi Desert! But this was precisely the territory that, according to the initial assumption, was also part of Tethys.
Yarmolyuk also knew something else: these were not the first hyperbasites found in southern Mongolia. Several years ago, one of the expedition geologists discovered them at about the same latitude, four hundred kilometers to the east. And mentally connecting the point of the first find with the location of his camp, Yarmolyuk received a rather long line of distribution of oceanic rocks in the Gobi. Moreover, he recalled how in the year before last, near one of the ridges, he had already encountered a layer of hyperbasites, the presence of which he considered a phenomenal exception.
Now he looked at both the former finds and the current ones with completely different eyes. Together, they could serve as direct evidence that Tethys really was the ocean!
But in this case, the volcanic belt of southern Mongolia was once a chain of islands and mountain structures similar to the modern Kuril-Kamchatka arc!
A lot lined up in a rather interconnected series of events. An explanation was given for the primary outpouring of basalt through cracks of relatively short length - after all, they cut only the islands. When the eruptions began to concentrate in "hot spots", the cones of volcanoes began to rise. And only then came the time of explosive catastrophes, that is, the time of the formation of calderas and associated associations of contrasting rocks.
He already traced the same sequence of events in the Okhotsk-Chukotka belt of ancient volcanism (with the only difference that they took place there two hundred million years later). And what about hyperbasites? They were also found on the territory of the Far Eastern belt. This means that the biography of the region there began with the emergence of the longest island arc, or perhaps several such arcs.
No, the similarity in the structure of two vast areas so distant from each other Yarmolyuk could no longer consider the result of any coincidences. Most likely, nature here and there in its work simply adhered to strict rules. And something extremely significant follows from them.
No one doubted the magmatic nature of basalt. The situation was quite different with granite.
Granite and related rocks are very common in the earth's crust. They are found in the bowels of the largest mountain systems of the planet and throughout the entire "ring of fire" covering the water area The Pacific, they make up vast territories in Scandinavia, Ukraine, Canada. Deposits of many metals are closely related to these rocks. Unfortunately, geologists have never been able to directly observe the formation of granite occurring at great depths. This was both the main difficulty in understanding its nature and the reason for the controversial nature of the problem.
With the utmost captiousness, Yarmolyuk tried on all the versions and guesses that were available in science on this score to what he saw on expeditions with his own eyes.
Some of them dealt with the melting of already existing various rocks into granite, silica-rich magma. But nowhere in the surveyed areas did he find confirmation of this. Those granite strata, which he studied very well, were invariably homogeneous in composition. Consequently, a charge with a random and varying set of components could in no way serve as a source material for them, which, in essence, were the packs of "ready-made" rocks.
Another well-known hypothesis suggested the presence of two types of magma under the earth's crust. But in this case, Yarmolyuk reflected, granite magma, as lighter, should have surfaced and, being located on top of the basalt, bulge out in the form of some kind of domes, which he had never found either in the Okhotsk-Chukotka or in the South Mongolian belts.
Finally, the hypothesis about a single basaltic magma as the source of all plutonic melts was widespread. But the calculations of prominent scientists have proven that only a tenth of the entire known granite mass could have appeared in this way. Yarmolyuk saw another flaw. With such a process of dividing a single magma into granite and basalt, rocks of an intermediate composition should have appeared, but he did not come across such anywhere.
And yet, in this hypothesis he saw a rational grain - the idea of a single initial basaltic magma. Only he decided to develop it differently.
No, it was not in vain that he once studied the behavior of complex melts under conditions of changing high pressure! It suggested a diagram of its own process model.
Here's the gist of it. In the initial stage of volcanism (outpourings through linear cracks and the first cones), basaltic magma participates in its original form. The pause that follows is only a seeming calm. A very active work is going on inside the column of the rising hot melt. Relatively light silica, water, alkalis move to its upper part from below, while they displace some of the heavier compounds of calcium, magnesium, iron.
As a result, two almost non-mixing zones are formed, similar to how, say, water and oil separate, even if they are first shaken together in one cup.
So, in the upper zone, magma is gradually concentrated, which can already be considered granite. Because it is closer to the Earth's surface, that is, under conditions of less high pressure than the lower zone, it begins to boil, as it were, vigorously emitting water vapor. However, the free escape of gases is impeded by the shell of the rocks surrounding the magma chamber. The pressure underneath it begins to rise, as in an overheated steam boiler. When it exceeds the threshold of the strength of the shell, an explosion occurs and the release of atomized granite melt occurs. Blocks of a volcanic cone fall into the partially emptied chamber. In other words, an annular fault and a caldera are formed.
When the reserves of granite magma are exhausted, the turn will come to the lower zone with its exclusively basaltic melt. Its outpouring will end the final stage of the entire volcanic cycle.
Yarmolyuk compared this model of his with observations of some active volcanoes. And found a striking coincidence in the sequence of the eruption of materials of contrasting composition. The last cycle of Krakatoa's activity, for example, began with the growth of the Rakata basalt cone. Then, during the catastrophe of 1883, about twenty cubic kilometers of atomized granite magma was thrown out. And with the formation of the caldera, after a while, the Anak-Krakatau cone appeared in it - again basalt.
And yet, he considered it necessary to check himself again and again directly on the outcrops of the South Mongolian ridges, where in places, as he remembered, it was the deep structure of extinct volcanoes that had been partially revealed.
The yurt stood in a dry valley between the hills. A herd of goats grazed to one side. And a few more haughty camels were loitering at a distance. At the entrance to the yurt there was a motorcycle, on which tanned daughter children climbed.
Yarmolyuk with two geologists turned here, intending only to inquire about the road and the wells. But the hosts, with the hospitality inherent in the Mongols, began to treat the visitors. Bowls appeared, filled to the brim with cool sour milk. They were brought up with a slight bow. Taking his own, Vladimir spilled a little liquid out of awkwardness and was very embarrassed by this. But the owner nodded his head cheerfully, took his cup, then, as if performing a ritual, stretched out his hand forward and deliberately splashed some of the milk on the ground. Everyone around laughed. Yarmolyuk remembered: this is how they wish a person good luck on the way.
On the indicated road, they quickly reached a low, smoothed ridge. It was so picturesque that everyone got out of their cars just to admire the beautiful view.
Black basalt rocks interspersed with columns of pink granite. And the peaks were decorated with boulders, resembling either the towers of castles, or the figures of people and animals. Their volume was emphasized by the bottomless blue sky.
Yarmoluk felt unaccountable joy. It would be difficult for him to convey his feelings in words. He just looked and looked, as if absorbing this miraculous beauty. If they asked him now, why is he every time, when summer comes, he is in such a hurry on a long journey - to experience at least a few of these minutes or to verify this harmony with his geological "algebra"? - he would have found it difficult to answer. I found it difficult because I never separated one from the other. In his soul, they did not just coexist, but lived as some kind of single, inseparable need. When he was building his model, although it may seem inappropriate, he was also concerned about whether it was graceful enough,
And now he is already climbing steeper than the granite slope, hoping in the depths of the ridge to find those places where vents filled with petrified lava emerge on the day's surface, places where it will be possible to obtain new confirmation of the validity of his model of the magmatic mechanism.
Articles published. A book about Southern Mongolia has been published. For a series of works on ancient volcanism, an employee of the Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the USSR Academy of Sciences Vladimir Yarmolyuk was awarded the Lenin Komsomol Prize in 1978. And the laureate is again plagued by "overtime" thoughts. This time about the origin of some unusual, from his point of view, faults in the earth's crust, which he managed to detect during the next field season ...
Well, let's at least mentally follow the old Mongolian custom - spill some milk on the ground, wishing a good journey to all those who set off to the berets of the mysterious "lands" for science.
On two continents - Laurasia and Gondwana Tethys (ocean) Tethys (ocean)
Tethys(the English-language form of the name of the Greek goddess of the sea Tefis is Greek. Τηθύς , Tethys) is an ancient ocean that existed in the Mesozoic era between the ancient continents of Gondwana and Laurasia. The relics of this ocean are the modern Mediterranean, Black and Caspian Seas.
History of the issue
Contemporary views
Tethys existed for about a billion years (850 to 5 million years ago), dividing the ancient continents of Gondwana and Laurasia, as well as their derivatives. Since during this time continental drift was observed, Tethys constantly changed its configuration. From the wide equatorial ocean of the Old World, it turned into the western bay of the Pacific Ocean, then into the Atlanto-Indian channel, until it broke up into a series of seas. In this regard, it is appropriate to talk about several Tethys oceans:
- Prototethis(Precambrian). According to scientists, Prototethis was formed 850 million years ago as a result of the split of Rodinia, was located in the equatorial zone of the Old World and had a width of 6-10 thousand km.
- Paleotethis 320-260 million years ago (Paleozoic): from the Alps to Qinling. The western part of the Paleotethis was known as Reikum. At the end of the Paleozoic, after the formation of Pangea, Paleotethis was an ocean-bay of the Pacific Ocean.
- Mesotethis 200-66.5 million years ago (Mesozoic): from the Caribbean Sea in the west to Tibet in the east.
- Neotethis(Paratethys) 66-13 million years ago (Cenozoic). After the split of Gondwana, Africa (with Arabia) and Hindustan began to move northward, compressing the Tethys to the size of the Indo-Atlantic Sea. 50 million years ago, Hindustan wedged into Eurasia, taking the modern position. Closed with Eurasia and the Afro-Arabian continent (in the region of Spain and Oman). The convergence of the continents caused the rise of the Alpine-Himalayan mountain complex (Pyrenees, Alps, Carpathians, Caucasus, Zagros, Hindu Kush, Pamir, Himalayas), which separated from Tethys northern part- Paratethys (sea "from Paris to Altai").
- Sarmatian sea(from the Pannonian Sea to the Aral Sea) with the Crimea and the Caucasus islands 13-10 million years ago. The Sarmatian Sea is characterized by isolation from the world's oceans and progressive desalination. About 10 million years ago, the Sarmatian Sea reestablishes communication with the world's oceans in the Bosphorus Strait. This period was called the Meotic Sea, which was the Black and Caspian Sea, connected by the North Caucasian channel. 6 million years ago, the Black and Caspian Seas separated. The disintegration of the seas is partly attributed to the uplift of the Caucasus, partly to a decrease in the level of the Mediterranean Sea. 5-4 million years ago, the level of the Black Sea rose again and it again merged with the Caspian in Akchagyl sea, which evolves into the Absheron Sea and covers the Black Sea, Caspian, Aral and floods the territory of Turkmenistan and the lower Volga region. In fact, the Sarmatian Sea existed 500-300 thousand years ago.
The final "closure" of the Tethys Ocean is associated with the Miocene epoch (5 million years ago). For example, the modern Pamir for some time was an archipelago in the Tethys Ocean.
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Excerpt from Tethys (ocean)
Although the source of the chagrin [grief] of Mr. Michaud was supposed to be different from the one from which the grief of the Russian people flowed, Michaud had such a sad face when he was introduced into the sovereign's office that the sovereign immediately asked him:- M "apportez vous de tristes nouvelles, colonel? [What news have you brought me? Bad news, Colonel?]
- Bien tristes, sire, - answered Michaud, lowering his eyes with a sigh, - l "abandon de Moscou. [Very bad, your majesty, abandonment of Moscow.]
- Aurait on livre mon ancienne capitale sans se battre? [Have they really betrayed my ancient capital without a battle?] - suddenly flaring up, the sovereign said quickly.
Michaud respectfully conveyed what he had been ordered to transfer from Kutuzov - precisely that it was not possible to fight near Moscow and that, since there was only one choice - to lose the army and Moscow or Moscow alone, the field marshal had to choose the latter.
The Emperor listened in silence, without looking at Michaud.
- L "ennemi est il en ville? [Has the enemy entered the city?]" He asked.
- Oui, sire, et elle est en cendres a l "heure qu" il est. Je l "ai laissee toute en flammes, [Yes, your majesty, and he is turned into a conflagration at the present time. I left him in the flame.] - Michaud said resolutely; but, looking at the emperor, Michaud was horrified at what he had done. The Tsar began to breathe heavily and quickly, his lower lip trembled, and his beautiful blue eyes instantly moistened with tears.
But this only lasted one minute. The Emperor suddenly frowned, as if condemning himself for his weakness. And, raising his head, he addressed Michaud in a firm voice.
- Je vois, colonel, par tout ce qui nous arrive, - he said, - que la providence exige de grands sacrifices de nous ... Je suis pret a me soumettre a toutes ses volontes; mais dites moi, Michaud, comment avez vous laisse l "armee, en voyant ainsi, sans coup ferir abandonner mon ancienne capitale? N" avez vous pas apercu du decouragement? Providence requires great sacrifices from us ... I am ready to submit to his will; but tell me, Michaud, how did you leave the army that left my ancient capital without a fight? Have you noticed a discouragement in her?]
Seeing the calmness of his tres gracieux souverain, Michaud also calmed down, but he had not yet had time to prepare an answer to the direct, essential question of the sovereign, which demanded a direct answer.
- Sire, me permettrez vous de vous parler franchement en loyal militaire? [Sovereign, will you allow me to speak frankly, as befits a real warrior?] - he said to gain time.
- Colonel, je l "exige toujours, - said the emperor. - Ne me cachez rien, je veux savoir absolument ce qu" il en est. [Colonel, I always demand this ... Don't hide anything, I certainly want to know the whole truth.]
- Sire! - said Michaud with a thin, barely perceptible smile on his lips, having managed to prepare his answer in the form of a light and respectful jeu de mots [puns]. - Sire! j "ai laisse toute l" armee depuis les chefs jusqu "au dernier soldat, sans exception, dans une crainte epouvantable, effrayante ... [Sovereign, I left the whole army, from the commanders to the last soldier, without exception, in the great, desperate fear ...]
- Comment ca? - sternly frowning, interrupted the emperor. - Mes Russes se laisseront ils abattre par le malheur ... Jamais! .. [How so? Can my Russians be discouraged before failure ... Never! ..]
This was just what Michaud was waiting for to insert his pun.
“Sire,” he said with a respectful playfulness of expression, “ils craignent seulement que Votre Majeste par bonte de c? Ur ne se laisse persuader de faire la paix. Ils brulent de combattre, - said the representative of the Russian people, - et de prouver a Votre Majeste par le sacrifice de leur vie, combien ils lui sont devoues ... ... They are eager to fight again and to prove to your Majesty with the sacrifice of their lives how devoted they are to you ...]
- Ah! - The sovereign said calmly and with a gentle gleam of eyes, striking Michaud on the shoulder. - Vous me tranquillisez, colonel. [BUT! You comfort me, Colonel.]
The Emperor, bowing his head, was silent for some time.
- Eh bien, retournez al "armee, [Well, go back to the army.] - he said, straightening up to his full height and with an affectionate and majestic gesture addressing Michaud, - et dites a nos braves, dites a tous mes bons sujets partout ou vous passerez, que quand je n "aurais plus aucun soldat, je me mettrai moi meme, a la tete de ma chere noblesse, de mes bons paysans et j" userai ainsi jusqu "a la derniere ressource de mon empire. Il m "en offre encore plus que mes ennemis ne pensent," said the sovereign, more and more enthusiastic. "Mais si jamais il fut ecrit dans les decrets de la divine providence," he said, raising his beautiful, meek and brilliant feeling eyes to the sky, - que ma dinastie dut cesser de rogner sur le trone de mes ancetres, alors, apres avoir epuise tous les moyens qui sont en mon pouvoir, je me laisserai croitre la barbe jusqu "ici (the sovereign showed his hand to half of his chest) , et j "irai manger des pommes de terre avec le dernier de mes paysans plutot, que de signer la honte de ma patrie et de ma chere nation, dont je sais apprecier les sacrifices! .. [Tell our brave men, tell all my subjects , wherever you go, that when I have no more soldiers, I myself will become the head of my kind nobles and good men and thus exhaust the last means of my state. They are more than my enemies think ... But if divine providence was destined m, so that our dynasty ceases to reign on the throne of my ancestors, then, having exhausted all the means that are in my hands, I will loose my beard until now and rather go eat one potato with the last of my peasants than dare to sign the shame of my homeland and my dear people whose sacrifices I know how to value! ..] Having said these words in an agitated voice, the emperor suddenly turned, as if wishing to hide from Michaud the tears that had come to his eyes, and walked into the depths of his office. After standing there for a few moments, he returned with large steps to Michaud and with a strong gesture squeezed his hand below the elbow. The beautiful, meek face of the sovereign flushed, and his eyes burned with a gleam of determination and anger.
it short word contains the history of the origin of the seas and mountains, the secrets of disappeared civilizations and the charm of ancient mythology.
TETHIS- an ancient ocean that stretched across the entire globe, starting on the eastern side of the Atlantic Ocean and ending on the western one. TETIS divided the ancient ancestral lands of Laurasia and Gondwana, which gave rise to modern continents. The name TETIS was proposed at the end of the 19th century by the Austrian geologist E. Suess after the name of the ancient Greek goddess of the sea Thetis (Thetis).
According to the assumptions of scientists, the very first continent of the Earth - the Foremother of Pangea split into two supercontinent: the northern one - Laurasia and the southern one - Gondwana about 200 million years ago. Between the divided supercontinents, the TETIS ocean was formed.
Gondwana is a supercontinent of the southern hemisphere, which consisted of the main parts of modern South America, Africa, Arabia, Antarctica, Australia, the Indian subcontinent and about. Madagascar. Laurasia is a supercontinent of the northern hemisphere, which consisted of modern North America and Eastern Europe.
The young Earth was in a powerful movement - separate continents were torn off from the giant foremother, the mountains were buried in the depths of the sea, and, on the contrary, continents grew from the bottom of the ocean. In the depths of TETIS, a giant volcanic belt of the planet passed, volcanoes erupted here, the earth's crust shifted, ruptured and swelled. It is here, in place of the ancient seas, that the highest mountain ranges will subsequently perch, and whole continents will drown in the depths. Slowly but inexorably, Europe, North America, India, Africa, Australia, Antarctica diverged. At the same time, the Atlantic, Indian, Arctic oceans began to form. The area of the TETIS ocean began to decrease, while giant mountain ranges surrounding the planet - the Atlas, the Alps, the Caucasus, the Pamirs, the Himalayas - grew out of its depths. The ocean turned into a sea, in the end, only the Mediterranean, Black, Caspian seas, the Persian Gulf and the seas of the Malay archipelago remained from it.
Maybe one of you wants to know what will happen next?
According to the forecasts of scientists, the shift of the plates of Europe and Africa, leaving only the Mediterranean basin from TETIS, will continue in the future and in 50 million years the remnants of TETIS in the form of the Mediterranean Sea will disappear altogether, and Europe will closely join North Africa.
This mysterious ocean left a memory of itself in the form of mighty mountain ranges stretching across almost the entire planet, emerging from its depths along the volcanic belt of the planet. It reminds of itself with global catastrophes, earthquakes and volcanic explosions, incredible paleontological finds, it is with the TETIS ocean that the greatest marine secrets are associated, myths about sunken civilizations, including the Flood and the mystery of the disappeared Atlantis.
It is no coincidence that the ancient ocean was named after the ancient Greek goddess. For the first time, the name of the goddess TETIS is mentioned in the myths about the creation of the world and the gods. TETIS is the sister, and later the wife of the Ocean, who gave rise to the seas and rivers. In addition, in later myths, TETIS (Thetis) is a good goddess of the sea. TETIS is the first of the immortals to marry a human being, belongs to the category of good gods - patrons who help, protect and save those who are in trouble at sea. Thetis immediately and disinterestedly came to the aid of people and gods; it was not for nothing that seafarers of all times adorned the bow of ships with her image. TETIS, the eldest of fifty Nereids - daughters of the sea elder Nereus, who possessed the gift of divination and reincarnation, is one of the most attractive tragic and human heroines of the myths of antiquity. Beautiful, kind and sympathetic, she was too good and smart to be happy.
All the difficulties of her fate began when two of the greatest gods at once - Poseidon and Zeus himself simultaneously turned their attention to her. Perhaps she would have become the wife of the Thunderer and the ruler of Olympus, if not for the prophecy of the titan Prometheus, who predicted to Zeus that she would give birth to a son who would surpass her father. Then Zeus forcibly married her to a mortal - the Thessalian king Peleus.
The wedding took place in the cave of ketaurus Chiron, all the gods of Olympus walked on it, the only not invited was the goddess of discord Eris, who managed to take revenge by throwing Golden Apple from the garden of the Hesperides with the inscription “Most Beautiful”. It was because of this "apple of discord" that Athena, Aphrodite and Hera quarreled and, ultimately, the Trojan War began.
From Peleus, TETIS gave birth to Achilles, whose prediction promised either great glory and early death, or a long, but unremarkable life. Of course, the life of Achilles was dearer to a loving mother than glory, wishing to save her son from death, she defended him by all possible means.
To make him immortal, she dipped the baby into the waters of the magical Styx, but only one place was left not washed with water - the heel by which she held him (the same Achilles heel). TETIS asked Hephaestus to forge wonderful armor, in which the son was invulnerable. It was impossible to defeat Achilles in this armor. Only the revenge of the god Apollo himself, who directed the arrow, precisely into the vulnerable heel, interrupted life greatest hero Trojan War.
According to legend, Thetis took the soul of Achilles to the island of Levku, where you can sometimes hear the mighty voice of the hero.
Even Leonardo da Vinci found fossilized shells of marine organisms on the peaks of the Alpine mountains 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 modernity - the Alpine-Himalayan belt - was born from ancient sea... At the end of the last century, the outline 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 at the end of the last century, called this space the Tethys sea (in honor of Thetis, or Thetis - the sea goddess).
A new turn in the idea of Tethys came at the beginning of this century, when A. Wegener, the founder modern theory continental drift, made the first reconstruction of the Late Paleozoic supercontinent Pangea. As you know, he pushed Eurasia and Africa to the North and South America, combining their coasts and completely covering the Atlantic Ocean. At the same time, it was found that, covering the Atlantic Ocean, Eurasia and Africa (together with Hindustan) diverge to the sides and between them, as it were, there is a void, a gaping several thousand kilometers wide. Of course, A. Wegener immediately noticed that the gaping corresponds to the Tethys sea, but its dimensions corresponded to the oceanic ones, and one should speak about the Tethys ocean. The conclusion was obvious: as the continents drifted, as Eurasia and Africa moved away from America, a new ocean, the Atlantic Ocean, was opened and at the same time the old ocean, the Tethys, was closed (Fig. 1). Consequently, 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 the study of the structure and history of the Earth - plate tectonics. Let us recall its main provisions.
The upper solid shell of the Earth, or lithosphere, is broken by seismic belts (95% of earthquakes are concentrated in them) into large blocks or plates. They cover continents and oceanic spaces (there are 11 large plates in total today). 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-oceanic ridges - lithospheric plates diverge to the sides at a speed of 2 to 18 cm / year, making room for basalts - volcanic rocks melted from the mantle - to rise upward. When basalts solidify, they increase the diverging edges of the slabs. The process of plate spreading is called spreading. In other active zones - in deep-water trenches - lithospheric plates approach each other, one of them "dives" under the other, going down to depths of 600-650 km. This process of sinking plates and absorbing them into the Earth's mantle is called subduction. Long belts of active volcanoes of specific composition (with a lower silica content than in basalts) arise above the subduction zones. The famous Pacific Ring of Fire is located directly above the subduction zones. Catastrophic earthquakes recorded here are caused by the stresses necessary for the lithosphere to pull the plate down. Where the plates approaching each other carry continents that, because of their lightness (or buoyancy), are not able to sink into the mantle, continents collide and mountain ranges arise. The Himalayas, for example, were formed when the continental block of Hindustan collided with the Eurasian continent. The rate of convergence of these two continental plates is now 4 cm / year.
Since lithospheric plates are, in the first approximation, rigid and do not undergo significant internal deformations during their movement, a mathematical apparatus can be applied to describe their movements along the earth's sphere. It is not complicated and is based on L. Euler's theorem, according to which any movement along a 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 enough 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 the directions (azimuths) and linear velocities displacements of plates at specific points. As a result, for the first time it was possible to introduce a quantitative factor into geology, and it began to move from a speculative and descriptive science to the category of exact sciences.
The above remarks are necessary in order for the reader to understand in the future the essence of the work done jointly by Soviet and French scientists on the Tethys project, which was carried out within the framework of an 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 V.I. P.P. Shirshova of the USSR Academy of Sciences. Corresponding members of the Academy of Sciences of the USSR A.S. Monin and A.P. Lisitsyn, V.G. Kazmin, I.M.Sbolshchikov, L.A. Savostia, O. G. Sorokhtin and the author of this article took part in the research. Employees of other academic institutions: 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. A. Adamia and M.B. Lordkipanidze), the Geological Institute of the Academy of Sciences of the Armenian SSR (Corresponding Member of the Academy of Sciences of the Armenian SSR A.T. and M.I.Satian), the Geological Faculty of Moscow State University (Academician of the USSR Academy of Sciences V .: E. Khain, N.V. Koronovsky, N.A. Bozhko and O. A. | Mazarovich).
On the French side, the project was led by one of the founders of the theory of plate tectonics C. Le Pichon (University of Pierre and Marie Curie in Paris). Experts in the geological structure and tectonics of the Tethys belt took part in the research: J. Dercourt, L.-E. Rikou, J. Le Priviere and J. Jeysan (Pierre and Marie Curie University), J.-C. Cie-Bouet (Center for Oceanographic Research in Brest), M. Westphal and J.P. Lauer (University of Strasbourg), J. Boulene (University of Marseille), B. Bijou-Duval (State Oil Company).
Research included joint expeditions to the Alps and 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 began 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 summarized in a special issue of the international journal "Tectonophysics" in 1986. Abridged version of the report at published in French in 1985 in the Bulletin societe de France, in Russian the History of the Tethys Ocean was published.
The Soviet-French project "Tethys" was not the first attempt to reconstruct the history of this ocean. It differed from the previous ones by the use of new, better data, a much greater length of the studied region - from Gibraltar to the Pamirs (and not from Gibraltar to the Caucasus, as it was before), and most importantly, by attracting and comparing materials from various sources independent from each other. 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 displacements of the main lithospheric plates of the Earth. They are entirely related to plate tectonics. Penetrating into the depths of geological time and consistently moving Eurasia and Africa to North America, we get the relative positions of Eurasia and Africa and identify 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 mobilism and plate 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 regions in the Atlantic Ocean.
In the ocean, we can reliably determine the age of the basalt basement. If we combine the same-aged bottom strips, which are symmetrically on opposite sides of the axis of the mid-oceanic ridges, we will obtain the parameters of plate displacement, that is, the coordinates of the rotation pole and the angle of rotation. The procedure for searching for the parameters for the best alignment of the bottom bands of the same age 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 the 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 as a rigid framework for each moment of geological time, 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 at this location can be divided into two periods. In the first period, 190-80 million years ago, Africa was 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 Caucasus region was 2500 km, and on the traverse of the Pamirs, at least 4500 km. During this period, Africa shifted eastward relative to Laurasia, covering a total of about 2200 km. The second period, which began about 80 million years ago and continues to this 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 draw closer to Eurasia, which ultimately led to the closure of the Tethys Ocean.
The directions and rates of movement of Africa 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 (albeit at a low speed of 0.8-0.3 cm / year) to the southeast, making it possible to open up a young oceanic basin between Africa and Eurasia.
80 million years ago, in the western segment, Africa began to move north, and in modern times it moves to the northwest in relation to Eurasia at a speed of about 1 cm / year. The fold deformations and the growth of mountains in the Alps, Carpathians, and Apennines are in full accordance with this. In the eastern segment (in the Caucasus region), Africa 140 million years ago began to converge with Eurasia, and the rate of convergence fluctuated noticeably. The accelerated approach (2.5-3 cm / year) refers to the intervals 110-80 and 54-35 million years ago. It was in these intervals that intense volcanism was noted in the volcanic arcs of the Eurasian margin. The slowdown of movement (up to 1.2-11.0 cm / year) falls on the intervals of 140-110 and 80-54 million years ago, when stretching occurred in the rear of the volcanic arcs of the Eurasian margin and the deep-water basins of the Black Sea were formed. The minimum approach speed (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 opening of the Red Sea, the Arabian Peninsula broke away from Africa and began to move northward, pushing its ledge into the edge of Eurasia. It is no coincidence that the mountain ranges of the Caucasus have grown 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 the layers of later magnetization and establish what the primary magnetic vector was. It should be pointed towards the paleomagnetic pole. If the continents are not drifting, then all vectors will be oriented in the same way.
Back in the 50s of our century, it was firmly established that within each, separately taken continent, paleomagnetic vectors are indeed oriented parallel and, although they are not elongated along the 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 orientations of vectors, that is, the continents have different paleomagnetic poles. This alone was in itself the basis for 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: in Eurasia - 71 ° N. w „150 ° h. (Chukotka region), in Africa - 60 ° N. w, 108 ° W (region of Central Canada), North America - 70 ° N. w., 132 ° E (the area of the Lena estuary). If we take the parameters of plate rotation relative to each other and, say, move the paleomagnetic poles of Africa and North America along with these continents to Eurasia, then we will find an amazing coincidence of these poles. Accordingly, the paleomagnetic vectors of all three continents will be oriented subparallel and directed to one point - the common paleomagnetic pole. This kind of comparison of kinematic and paleomagnetic data was carried out 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 - fringed the Tethys Ocean. However, inside the ocean, undoubtedly, there were smaller continental or other blocks, as now, for example, inside the Indian Ocean is the microcontinent of Madagascar or a small continental block of the Seychelles. Thus, inside the Tethys were, for example, the Transcaucasian massif (the territory of the Rion and Kura depressions and the mountain bar between them), the Daralagez (South Armenian) block, the Rhodope massif in the Balkans, the Apulian massif (covering most of the Apennine Peninsula and the Adriatic Sea). Paleomagnetic measurements within these blocks are the only quantitative data that make it possible to judge their position in the Tethys Ocean. Thus, the Transcaucasian massif was located near the Eurasian margin. The small Daralagez block is, as it turns out, of southern origin and was previously annexed to Gondwana. The Apulian massif did not greatly displace in latitude relative to Africa and Eurasia, but in the Cenozoic it was turned 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 one and a half hundred years. This group of data is also the most controversial, since a quantitative approach can least of all be applied to it. 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 made it possible to establish a number of essential features of the Tethys paleoocean.
Let's start with the fact that only by the distribution of marine Mesozoic (and Cenozoic) deposits in the Alpine-Himalayan belt, it became obvious that the sea or the Tethys ocean here in the past. Tracing different geological complexes on 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 on their edges. Of key importance are the outcrops of the so-called ophiolite complex (from the Greek ocpir - snake, some of these rocks are called serpentines). Ophiolites are composed of heavy rocks of mantle origin, depleted in silica and rich in magnesium and iron: peridotite, gabbro and basalt. Such rocks form the bedrock of modern oceans. With this in mind, 20 years ago, geologists came to the conclusion that ophiolites are remnants of the crust of ancient oceans.
Ophiolites of the Alpine-Himalayan belt mark the Tethys ocean floor. 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 have been found in the Dealer Alps in Yugoslavia and Albania, in the mountain ranges of Greece, including the famous Mount Olympus. Outcrops of ophiolites, forming an arc facing south, between the Balkan Peninsula and Asia Minor, and then 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 stretch to the Zagros ridge and to the mountains of Oman, where ophiolite plates are thrust over the shallow sediments of the Arabian Peninsula's outskirts. But here, too, the ophiolite zone does not end, it turns to the east and, following parallel to the coast Indian Ocean, goes further to the northeast into the Hindu Kush, Pamir and Himalayas. Ophiolites are of 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 in several tens of kilometers, while the original width of the Tethys Ocean was several thousand kilometers. Consequently, when the continents approached, almost all of the oceanic crust of the Tethys went into the mantle in the zone (or zones) of subduction along the edge of the ocean.
Despite the small width, the ophiolitic, or main, seam of the Tethys separates two provinces that are sharply different in geological structure.
For example, among the Upper Paleozoic deposits that accumulated 300-240 million years ago, to the north of the seam, continental sediments predominate, some of which were deposited in desert conditions; while to the south of the seam there are thick strata of limestone, often reef, marking a vast shelf sea in the equatorial region. Equally striking is the change in Jurassic rocks: clastic, often coal-bearing, deposits north of the seam again oppose limestones south of the seam. The seam separates, as geologists say, different facies (conditions for the formation of precipitation): the Eurasian temperate climate from the Gondwana equatorial climate. Crossing the ophiolite seam, we find ourselves, as it were, from one geological province to another. To the north of it, we meet large granite massifs surrounded by crystalline schists and 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 lie consistently and without any signs of deformation and metamorphism ... It is clear that the two margins of the Tethys Ocean - the Eurasian and Gondwana - were sharply different 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 in the areas lying 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. 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 ridges. The composition of the lavas has been studied in great detail by Georgian petrologists. They found that the lavas are practically indistinguishable from the lavas of modern volcanoes of island arcs and active margins that make up the ring of fire of the Pacific Ocean. Let us recall that the volcanism of the Pacific Ocean framing is associated with the subduction of the oceanic crust beneath 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 the convergence of plates, on which the subduction of the oceanic crust took place. At the same time, to the south of the ophiolite suture, there are no volcanic manifestations of the same age; throughout the Mesozoic era and during most of the Cenozoic era, shallow-water shelf sediments, mainly limestones, 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 border of the convergence of lithospheric plates was, as geologists say, active. The southern, Gondwana margin, devoid of volcanism and occupied by a vast shelf, quietly passed into the deep basins of the Tethys Ocean and was passive. Geological data, and above all materials on volcanism, make it possible, as we can see, to reconstruct the position of the former boundaries of lithospheric plates and to outline ancient subduction zones.
The above does not exhaust all the factual material that must be analyzed to reconstruct 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 points in geological time from 190 to 10 million years ago. On these maps, using kinematic data, the position of the main continental plates - the Eurasian and African (as parts of Gondwana) was reconstructed, the position of microcontinent within the Tethys Ocean was determined, the boundary of the continental and oceanic crust was outlined, the distribution of land and sea was shown, paleolatitudes were calculated (based on paleomagnetic data )4 ... Particular attention is paid to the reconstruction of the boundaries of lithospheric plates - spreading zones and subduction zones. The vectors of displacement of the main plates for each moment of time are also calculated. In fig. 4 shows diagrams compiled from color maps. To make the prehistory of Tethys clear, a diagram of the arrangement of continental plates at the end of the Paleozoic (Late Permian epoch, 250 million years ago) was also added to them.
In the Late Paleozoic (see Fig. 4, a), the Paleo-Tethys Ocean stretched between Eurasia and Gondwana. Already at this time, the main tendency of tectonic history was determined - the existence of an active margin in the north of Paleo-Tethys and a passive -on South... At the beginning of the Permian period, comparatively large continental massifs - Iranian, Afghani, and Pamirian - were split off from the passive margin, which began to move, crossing the Paleo-Tethys, to the north, to the active Eurasian margin. The oceanic bed of the Paleo-Tethys in the front of drifting micro-continents was gradually absorbed in the subduction zone near the Eurasian margin, and in the rear of the micro-continents, between them and the Gondwana passive margin, a new ocean opened up - the Mesozoic Tethys proper, or Neo-Tethys.
In the Early Jurassic (see Fig. 4, b), the Iranian microcountry adjoined the Eurasian margin. When they collided, a folded zone (the so-called Cimmerian folding) arose. In the Late Jurassic, 155 million years ago, the opposition of the Eurasian active and Gondwana passive margins was clearly defined. 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 spread of Mesozoic ophiolites made it possible to outline a spreading axis in the central part of the Tethys Ocean.
In the Early Cretaceous (see Fig. 4, c) the African Plate - the heir to the disintegrated Gondwana by this time - moved towards Eurasia in such a way that in the west of Tethys the continents diverged somewhat and a new oceanic basin arose there, while in the eastern part the continents approached and the ocean floor Tethys 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 Tethys (it is sometimes called Mesogea, and its remnants are the modern deep-sea basins of the Eastern Mediterranean), ceased to open, and in the east of Tethys, judging by the dates of the ophiolites of Cyprus and Oman , the active stage of spreading ended. In general, the width of the eastern part of the Tethys Ocean by the middle of the Cretaceous period decreased to 1,500 km abeam the Caucasus.
The Late Cretaceous, 80 million years ago, includes the rapid reduction in the size of the Tethys Ocean: the width of the strip with the oceanic crust was at that time no more than 1000 km. In 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 covers.
At the Cretaceous – Paleogene boundary (see Fig. 4, e), at least three important events took place. Firstly, ophiolite plates, which cut off the oceanic crust of Tethys, were thrust over the passive margin of Africa by a wide front.
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