Cretaceous period of the Mesozoic era, fossils. Cretaceous period What animals became extinct at the end of the Cretaceous period

The Cretaceous period is considered the longest period of the Mesozoic, as it lasted about 79 million years.

Geography

The separated parts of the supercontinent Pangea drifted away from each other. The Tethys Ocean continued to separate the northern continent of Laurasia from southern Gondwana. The North and South Atlantic were still inaccessible. By the middle of the period, ocean levels were much higher; Most of the land we know was still under water. By the end of the period, the continents acquired outlines close to modern ones. Africa and South America took on their distinctive forms; but India had not yet encountered Asia, and Australia remained part of Antarctica.

Climate

During the Cretaceous period, climate conditions on Earth became warmer. It was colder at the poles. Fossils of tropical plants and ferns support this assumption.

Animals lived everywhere, even in colder areas. For example, fossil hadrosaurs dating back to the Late Cretaceous were discovered in Alaska.

When the asteroid struck, the world likely experienced what is known as a “nuclear winter,” when dust particles blocked many of the sun's rays from reaching the land surface.

Vegetable world

One of the hallmarks of the Cretaceous period was the development of flowering plants. The oldest angiosperm fossil is Archaefructus liaoningensis- was found in China. This plant is believed to be most similar to modern black pepper and is believed to be at least 122 million years old.

It was previously thought that pollinating insects such as bees and wasps evolved around the same time as angiosperms, a process called coevolution. However, new research indicates that insect pollination was likely common even before the first flowers. While the oldest fossil bee is about 80 million years old, evidence has been found that bees or wasps built their nests in Arizona's "Petrified Forest" (Petrified Forest National Park).

These nests, found by Stefan Chasiotis and his team at the University of Colorado, are at least 207 million years old. It is now thought that competition for insect attention likely contributed to the relatively rapid success and diversification of flowering plants. As diverse floral forms attracted insects for pollination, insects adapted different ways of collecting nectar and moving pollen, thereby creating the complex coevolutionary systems we are familiar with today.

There is limited evidence that dinosaurs ate angiosperms. According to a study published at the 2015 annual meeting of the Society of Paleontology. Two dinosaur coprolites (fossilized poop) were discovered in Utah that contained angiosperm particles. This finding, as well as others (including the presence of angiosperm fruits in the guts of Early Cretaceous ankylosaurs), suggests that some animals fed on flowering plants.

Animal world

During the Cretaceous period, more began to fly, joining pterosaurs in the air. The origin of flight is debated by many experts. The tree-down theory suggests that small reptiles may have evolved from jumping behavior. The ground-up hypothesis suggests that small theropods may have jumped high to catch prey and were able to develop the ability to fly. Feathers probably evolved from early skin coverings, the main function of which was most likely thermoregulation.

In any case, it is clear that birds were quite successful and became widely diversified during the Cretaceous. Confuciusornis (125-120 million years ago) is a bird with a modern beak and huge claws on the tips of its fingers. Iberomesornis was the size of a sparrow, could run, and probably fed on insects.

By the end of the Jurassic, some large sauropods, such as Apatosaurus and Diplodocus, became extinct. But other giant sauropods, including titanosaurs, flourished, especially during the late Cretaceous period.

Large herds of herbivorous ornithischian dinosaurs also flourished during the Cretaceous, including iguanodonts, ankylosaurs, and horned dinosaurs. Theropods, including Tyrannosaurus rex, continued to remain at the top until the end of the Cretaceous period.

Mass Cretaceous-Paleogene (C-T) extinction

About 66 million years ago, almost all large and many tropical ones became extinct. Geologists call this the Cretaceous-Paleogene extinction event because it marks the boundary between the Cretaceous and Paleogene periods.

In 1979, a geologist studying rock layers between the Cretaceous and Paleogene discovered a thin layer of gray clay separating the two eras. Other scientists have found this gray layer around the world, and tests have shown that it contains high concentrations of iridium, which is rare on Earth but common in most meteorites.

Also present in this layer are signs of "shocked quartz" and tiny glass particles called tektites, which form when rock is rapidly heated and cooled, as happens when an extraterrestrial object hits Earth with great force.

The Chicxulub crater on the Yucatan Peninsula dates back to this time. The crater is more than 180 kilometers in diameter, and chemical analysis shows that the area's sedimentary rocks were melted and mixed together by the impact of an asteroid about 10 kilometers in diameter.

When the asteroid hit Earth, it caused shock waves, massive tsunamis and sent a large cloud of hot rocks and dust into the atmosphere. As the hot debris fell to Earth, it ignited numerous forest fires, raising ambient temperatures.

A rain of dust and rocks raised the planet's global temperature within hours of the impact and wiped out animals that were too large to seek shelter. Small fauna that took refuge underground or in water, in caves or large tree trunks, were probably able to survive this catastrophe.

The tiny fragments likely remained in the atmosphere, blocking some of the sun's rays for months or years. When the amount of sunlight decreased, plants could not participate and died, as did the animals that fed on them.

Smaller, land-based animals such as mammals, lizards, turtles and birds may have been able to survive as scavengers by feeding on the carcasses of dead dinosaurs, fungi, roots and rotting plant matter.

There is also evidence that a series of huge volcanic eruptions occurred along the tectonic boundary between India and Asia, starting just before the Cretaceous-Paleogene extinction event. It is likely that these regional disasters affected many living organisms on the planet.

Eras. The Cretaceous period lasted for 79 million years, starting at 145 million years ago and ending at 66 million years ago. In order not to get confused in the eras and periods of the Earth's history, use the geochronological scale, which is located.

“Chalk” received its name due to the rich chalk deposits that are found in the geological strata of this period. It’s worth knowing that the very chalk you use to write in school are fossilized invertebrate marine organisms that lived tens of millions of years ago.

Chalk is divided into two sections - and. The beginning and end of the period differ radically. If the Lower and part of the Upper Cretaceous is the active development of life, the emergence of new species, the kingdom and diversity of dinosaurs, then the end of the Upper Cretaceous is a real tragedy for the animal kingdom of that period. A catastrophe on a planetary scale occurred in the Upper Cretaceous, as a result of which all dinosaurs, as well as many species of plants and animals, perished.

During the Cretaceous period, the continental breakup continued. There is no mention left of the former supercontinent Pangea. The continents moved further and further away from each other. Many scientists believe that due to the divergence of continents, the expansion of the Atlantic Ocean, changes in air currents in the atmosphere and ocean currents, the Earth began to cool during the first period of the Cretaceous period. However, at the end of the Cretaceous period, temperatures began to rise. Judging by some hypotheses, the reason for the rise in temperature was the increase in the area of ​​the world's oceans.

Animals of the Cretaceous period

The Cretaceous period is an active development of life of almost all species. The first flowering plants appeared in the Cretaceous period. This led to an increase in the diversity of insects that began to pollinate flowers. The seas were inhabited by such large predators as ichthyosaurs, plesiosaurs, and mososaurs.

Marine animals sometimes reached colossal sizes, for example, ichthyosaurs grew up to 24 meters in length, plesiosaurs - up to 20 meters, mososaurs - up to 14 meters. It is worth noting that they were still not as huge as, for example, the modern Blue Whale, reaching a length of 33 meters, however, the Blue Whale is a peaceful creature that feeds on plankton, but predators that reached 20 meters were represented in the seas a real threat to their victims.

Giant animals, dinosaurs, existed on land. A large species diversity is observed already in the period, and in the Cretaceous their diversity became even greater. Some dinosaurs were over 10 meters tall and over 20 meters long. These sizes are a record for terrestrial animals.

In addition to large lizards, this period is also noticeable by a wide variety of flying animals. If in our time only birds mastered the air environment, then in the Cretaceous period there were flying lizards (pterosaurs), lizard-tailed birds and ordinary birds (fan-tailed birds). The largest flying creature in those days was a representative of the pterosaur order Quetzalcoatlus, whose wingspan reached from 12 to 15 meters.

During the same period, the first snakes appeared. Reptiles without legs or limbs, snakes, are considered the youngest group of reptiles. Also, this species of animal, along with some others, was able to survive the upcoming catastrophe and survive to this day.

The Cretaceous also saw a diversity of mammals. If in the Jurassic period there were only small species of warm-blooded mammals, then in the Cretaceous period ungulates, insectivores, predators, as well as the very first primates appeared, which, as everyone knows, became the ancestors of modern people.

Cretaceous-Paleogene extinction

The Cretaceous period and the entire Mesozoic era ended with the mass extinction of animals. The causes of the Cretaceous-Paleogene catastrophe have not yet been reliably elucidated. The most likely cause was the fall of a large asteroid or even several asteroids. In addition, there are also versions such as: increased volcanic activity, changes in weather conditions, excess oxygen in the atmosphere, mass epidemic, excessive development of flowering plants and many others. One way or another, as a result of the mass extinction, all the dinosaurs that developed over many tens of millions of years disappeared. In layers after the Cretaceous-Paleogene extinction, archaeologists no longer find the remains of any dinosaurs, which suggests that none of the dinosaurs could survive. In addition, many aquatic reptiles, flying pterosaurs, ammonites, and brachiopods became extinct. In total, 16% of marine animal families and 18% of land vertebrate families died. Many small reptiles, birds, and warm-blooded animals survived. After the global extinction of animals, mammals began to reign on Earth.

Dinosaurs of the Cretaceous period

Velociraptor

Gainosaurus

Ichthyosaurs

Carnotaurus

Quetzalcoatlus

Majungasaurus

Mosasaurus

Parasaurolophus

Plesiosaurs

Pteranodon

Styracosaurus

Tarbosaurus

Tyrannosaurus

Torosaurus

Triceratops

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During the transition to the Middle Cretaceous period, the most important changes occurred in the plant world - the first flowering plants appeared. At the same time, the evolution of huge herbivorous dinosaurs continued.

The first flowering plant, Archaefmctus ("ancient fruit"), is known from rocks of the Lower Cretaceous. Its fossils were found in the Chinese province of Liaodun (in honor of which it received its name - Archaefruclus liaoningensis) 400 km north of Beijing, in an area that 140 million years ago was covered with swampy forest. The fruits of Arcbaefructus bore little resemblance to the fruits of modern plants, they looked more like a pair of leaves wrapped around seeds, however, the presence of a shell surrounding the seeds is the main characteristic of a flowering (angiosperm) plant. Determining the age of the rocks containing these fossils causes some difficulties. While some paleontologists believe that they are no more than 120 million years old, others estimate their age at 140 million years. In any case, Archaefruclus is the oldest known flowering plant.

Among the finds of plant fossils from the Late Cretaceous period, especially in regions located at high latitudes with a temperate climate, flowering plants account for 50 to 80%.

A fossilized magnolia leaf found in Upper Cretaceous rocks in Saxony, Germany. Reconstruction of the plant shows that it was very similar to Magnolia (Magnolia grandiflora), a favorite of gardeners.

The increase in the number of flowering species was accompanied by a decrease in the diversity of cycads and ferns, while the proportion of coniferous plant species in the local flora was relatively constant. However, in terms of biomass produced, the main components of terrestrial plant ecosystems at this time remained conifers, ferns and cycads.

Co-evolution?

In the 1970-80s. theories appeared in which the flourishing of angiosperms was associated with an increase in the number of herbivorous dinosaurs. It was stated that "flowering plants were spread by dinosaurs." The idea was that damaged flowering plants nowadays recover faster and more efficiently than gymnosperms (conifers and ferns). In the Cretaceous period, the role of modern cattle, whose grazing sometimes almost completely destroys plant cover, was played by large herbivorous dinosaurs that consumed huge amounts of plant food. Under such conditions, the increased resistance of flowering plants to damage gave them great advantages over gymnosperms.

However, recent studies in England have shown that the basic assumptions of these theories are unfounded. First, the distribution of angiosperms did not coincide in time with the peak numbers of herbivorous dinosaurs feeding on low-growing plants, and second, the geographical distribution of these tank-like and bulldozer-like animals did not coincide with the zones of origin and species diversity of flowering plants. Moreover, these theories assumed the dominant position of angiosperms in the plant world of the beginning of the Late Cretaceous period, which is also not true.

The Triceratops depicted in the picture fed on young shoots of plants and most likely led a gregarious lifestyle. Its terrifying horns and bone collar covering its neck provided reliable protection from any predator. These animals reached 7 m in length.

A large diversity of species of a group of plants does not automatically mean its important role in the flora of a given region. For example, the orchid family is now unusually diverse. But in any region where orchids grow, they are found as individual plants and constitute a negligibly small part of the biomass of the local ecosystem. Therefore, it is unlikely that during the Cretaceous period any species of herbivorous dinosaurs, let alone their entire community, fed only on a variety of but rarely found angiosperms.

Social insects

The oldest fossilized remains of termites and ants date back to the late Cretaceous period. The appearance of these insects should have significantly influenced the development of both flora and fauna. This is an important and interesting point in evolution, since it is believed that the body structure of some fossil animals, including small dinosaurs, allowed them to tear apart termite mounds in search of food. But, firstly, some of these animals existed before the appearance of social insects. And, secondly, the fossilized remains of the first social insects do not indicate their life in large communities immediately after their emergence. They became a significant source of food for large animals only after they began to create huge colonies. Nowadays, large animals such as anteaters, aardvarks and aardwolves feed on them.

The emergence of flowering plants undoubtedly accelerated the evolution and complicated the organization of communities of such social insects as bees, although finding out the details of the evolution of these small and fragile creatures is a rather difficult task.

Beginning of separation

By the beginning of the Cretaceous period, fossil remains of tetrapods (which include all vertebrates except fish) begin to show increasing differences between the fauna of the Northern and Southern Hemispheres, although limited exchange of land animals between them continued. The major change in the fauna of the Northern Hemisphere of this era was a decrease in the number and number of species of giant herbivorous sauropods that fed on the leaves and shoots of tall plants.

Along with these herbivorous giants, in the Early Cretaceous period the number of stegosaurs also decreased significantly, which, judging by their structure, were also herbivores and fed on shoots and leaves growing at low and medium altitudes. The slow decline in their numbers was accompanied by the spread of another type of large herbivorous dinosaurs - four-legged ankylosaurs covered with a strong shell, reaching 6 m in length and weighing, it is estimated, up to 3 tons.

Although they, like stegosaurs, occupied the ecological niche of "herbivores that feed on short plants", their wide, massive skulls were radically different from the long, low, small-toothed skulls of stegosaurs. The heads of ankylosaurs were almost completely covered (even the eyelids) by a shell. But, despite the complex structure of the skull, the teeth of the ankylosaur differed little from the teeth of the stegosaurus. The peculiarities of their abrasion made it possible to establish how ankylosaurs crushed food, and to conclude that, most likely, they ate roots, tubers and the core of plants. Differences in feeding habits explain why these two species of herbivorous dinosaurs, occupying almost the same ecological niche, could coexist for a long time. It is also possible that they ate different types of plants.

The gentle giants of the iguanodon settle down for the night. They reached 9 m in length and up to 5 m in height. Next to them was a group of small reptiles called Hypsilophodon. Speed ​​and dexterity helped the “little ones” (their size did not exceed 70 cm) survive.

North and South

Giant sauropods continued to dominate the south during this time, and the dominant herbivorous ornithopods in the Northern Hemisphere, such as hadrosaurs ("duck-billed dinosaurs"), were quite rare here.

A feature of the Cretaceous period was the very rapid spread of herbivorous dinosaurs from the suborder of orthithopods in the Northern Hemisphere: hadrosaurs, iguanodons (Iguanodon) and tenontosaurs (Tenontosaurus). They reached much larger sizes at this time than their Jurassic predecessors (eg Camptosaurus), and probably therefore foraged at higher levels.

Tyrannosaurus rex catching prey. The largest of all terrestrial predators that ever existed, it reached 13 m in length and rose 5 m above the ground. It probably used its disproportionately short forelimbs to rise from a lying position. Remains of a Tyrannosaurus rex discovered in the USA. Similar creatures also lived in Canada and China.

In these ornithopods, there is a clear evolutionary tendency towards a more complex mechanism for chewing food. Their teeth interlocked with their bite, allowing for efficient grinding of hard plant foods. The peculiarities of the connection of the cranial bones of iguanodons allowed the upper jaw to move slightly forward under the pressure of the teeth of the lower jaw. Unlike mammals (such as the camel), reptiles could not chew because they did not have jaw muscles that move the lower jaw laterally. However, the described structural features of ornithopods allowed them to grind food quite well with a longitudinal displacement of the jaws, which probably became one of the main reasons for their wide distribution throughout the Cretaceous period.

Other advanced herbivorous dinosaurs (not belonging to the suborder Ornithopod) appeared in the Late Cretaceous, and in many respects their jaws were even more developed than those of Iguanodons. These were the so-called. horned dinosaurs, or ceratopsians. The first ceratopsians were apparently the bipedal psittacosaurs from the Early Cretaceous of Mongolia and the massive, pig-like protoceratopsians from slightly later rocks. These were massive animals with short limbs and a protective collar around the neck formed by overgrown skull bones (such a collar was absent in psittacosaurs).

Closely related to them were the pachycephalosaurs (“thick-skull lizards”) with massive and durable skulls. During the mating season, males used their heads as weapons in fights with rivals. Their descendants, for example, the huge Triceratops, are typical dinosaurs of the last days of the prosperity of these huge reptiles.

During the Late Cretaceous period, there was an established and extremely diverse community of herbivorous dinosaurs of all shapes and sizes, which served as prey for the numerous predators of the era. Among the latter there were those who could hunt the largest herbivores.

Animals such as Trodden weighed no more than a modern dog, while the mass of the largest of the carnivorous dinosaurs, the giant tyrannosaurus (Tyrannosaurus rex), according to most scientists, reached 7 tons (according to other estimates, 4 tons). The diversity of dinosaurs' feeding habits and the way they obtained food in this era is amazing. In the late Cretaceous period, at the last stage of dinosaur development, their most progressive forms arose. 

The Cretaceous period is the last era that ends the Mesozoic era. It replaced the Jurassic, according to geologists, somewhere around 145 million years ago and lasted approximately eighty million years, after which another Tertiary period began, the “era of new life.” This rather long stage of the Earth’s development received its name due to the fact that it left us a legacy of powerful deposits of chalk, marl and sand. Although during these eighty million years there were no catastrophes of a planetary scale on Earth and, consequently, the extinction of a large number of species of plants and animals, the movement of tectonic plates, changes in the level of the world ocean and climate change made their own amendments to the process of evolution of living beings .

The Cretaceous period is usually divided into subsections: Lower and Upper Cretaceous. To understand how life developed in the seas, on land and in the air of that time, it is necessary to briefly characterize the tectonic mountain-building processes that took place, starting from the Jurassic stage. During the Lower Cretaceous, Gondwana and Laurasia continued to move away from each other. Exactly the same process occurred with Africa and South America. Thus, it increasingly took on the outlines familiar to us now. But in the east, Gondwana connected with Laurasia. Australia was where it is today, but only a third of its current territory rose above the water.

The Upper Cretaceous is characterized by the fact that the level of the world's oceans began to rise, and vast areas of Eastern Europe, Western Siberia, all of Arabia and almost all of modern Canada found themselves under water. However, by the end of the Cretaceous period, the Earth began to resemble the modern globe in its outline.

During the Cretaceous period, the climate also underwent changes. It was, of course, much warmer than the modern one. The spaces of today's Europe were covered by real tropical jungles. However, in high latitudes the seasons were already changing, and snow was falling in winter. This gave impetus to the fact that, along with spores and gymnosperms, angiosperms appeared. Trees such as beech, birch, ash and walnut, having appeared in the Cretaceous era, have survived to this day without changes. The earth acquired its first flowering plants - first magnolias, then roses. Flowering plants had the advantage that their pollen was carried not only by the wind, but also by insects. Fruit plants, hiding the seed in the fruit, spread with the help of animals that ate the fruit. Thus, fruit and flowering plants filled the entire planet.

Changes in the flora during the Cretaceous period also led to the emergence of new species of fauna. The first butterflies began to flutter in the air and bees began to fly, feeding on the nectar of flowers. The sea is dominated by foraminifera, whose dead and crumbled shells gave the name to this entire geological time. Along with them, other ammonite mollusks appear. The fish kingdom is dominated by sharks and Animals of the Mesozoic era - primarily dinosaurs and the first mammals - safely “migrated” from the Jurassic to the Cretaceous. But throughout the Cretaceous, several dead-end branches of bird-like dinosaurs died out, for example, Archeopteryx. But birds appear - the ancestors of modern geese, plovers, ducks and loons.

(the Jurassic period in particular), judging by the famous film, is also known as the era of dinosaurs. In general, the dominance of ancient lizards continues in the Cretaceous. But during the last period, the stegosaurus disappeared from the face of the earth, and its niche was occupied by the tyrannosaurus. The rich flora contributed to the emergence of new species of Triceratops, Iguanodons, Ankylosaurs and others. We can say that during the Cretaceous era, the species diversity of dinosaurs reached its peak. And at this time, hiding from the giants in their burrows, the future rulers of the Earth - mammals - lived. These rat-like animals rarely reached one meter in length; most species were small oviparous, armored or marsupial animals, weighing up to 500 g. But they were the future.

The duration of which is approximately determined to be ~80 million years (began ~145 million years ago and ended ~65 million years ago).

Flora and fauna

The fauna of the Cretaceous period had an appearance characteristic of the Mesozoic era, but at the same time was sharply different from the fauna of the Jurassic period. Among the invertebrates, new forms of belemnites and ammonites appeared in large numbers, and among the latter there were many representatives with an anomalous shell: stick-shaped, turret-shaped, etc. Some groups of elasmobranchs (rudists, inocerams, trigonians) and gastropods (nerineids) developed luxuriantly. Irregular sea urchins acquired significant development, and large foraminifera (orbitolins, orbitoids) appeared. Among vertebrates, the development of reptiles reached its culmination point, many of which acquired gigantic sizes. There was a flourishing of bony fish, which took a dominant position. Of the birds, only toothy ones existed. Mammals still played a modest role and did not reach great size. Among them, primitive placental forms appeared. Among fossil vertebrates, reptiles still occupy the leading place. Many large dinosaurs appeared on land. Of the aquatic lizards, plesiosaurs and snake-like mosasaurs were widespread, and to a lesser extent, ichthyosaurs, flying lizards, etc. Snakes appeared in the group of terrestrial reptiles. Cretaceous birds are represented by forms that still had teeth in their mouths, but had already lost features reminiscent of reptiles. The heyday of bony fish has arrived.

In the Early Cretaceous era, the flora resembled the Jurassic: conifers, ginkgo trees, cycads, and ferns continued to exist. At the same time, the first angiosperms (flowering plants) appeared, which quickly evolved and spread on the Cretaceous land. By the beginning of the Late Cretaceous era, angiosperms began to occupy a dominant position, and gymnosperms were relegated to the background. In the Cretaceous period, angiosperms - flowering plants - appeared. This resulted in an increase in the diversity of insects that became flower pollinators. The vegetation, preserving the Mesozoic appearance from the beginning of the period, from the Cenomanian century is characterized by the predominance of angiosperms flowering plants, the first signs of which were found in deposits of Hauterivian or even Valanginian age. All classes of plants of the Cretaceous period continue to exist to this day, but the ratio of angiosperm families has changed significantly.

At the end of the Cretaceous period, major changes occurred in the fauna: aquatic reptiles, dinosaurs, flying dinosaurs, toothed birds, ammonites, almost all belemnites and a number of genera and families of invertebrates became extinct. At this time, the most famous and very large extinction of many groups of plants and animals occurred. Many gymnosperms, all dinosaurs, pterosaurs, and aquatic reptiles became extinct. Ammonites, many brachiopods, and almost all belemnites disappeared. In the surviving groups, 30-50% of species became extinct. Whether this was caused by a planetary catastrophe, and if so, what were its causes and scale, remains unclear.

Tectonics and magmatism

During the Cretaceous period, the Mesozoic tectonic stage of development ends, which manifested itself especially rapidly along the outskirts of the Pacific segment of the earth's crust. The result of this was, first of all, the complete formation of Mesozoic mountain-folded structures (mesozoid) on the site of the Verkhoyansk-Chukotka and Sikhote-Alin geosynclinal regions in the Western Pacific geosynclinal belt, almost entirely in the Cordilleran geosynclinal region of the East Pacific belt and within the Tibetan geosynclinal region in eastern Mediterranean geosynclinal belt.
Extra-geosynclinal depressions complete their active tectonic development and platform granitoid magmatism ceases.
At the border of the Pacific geosynclinal belts and adjacent platforms, a structural zone appears in the form of linear large splits, along which the intrusion and outpouring of acidic magma occurs. This volcanic belt is called the Chukotka-Kathasian belt.
The orogenic stage of mesozoid development was accompanied by the formation of large marginal troughs (Pre-Verkhoyansk trough) at the border with the platforms.
Mountain building processes were accompanied by the intensive introduction of granitoid intrusions.

Intense tectonic activity in the Cretaceous period is not limited only to folding and magmatism. New major faults are being formed. They lead to the subsidence of vast areas of Gondwana. As a result, the Gondwanan continent breaks up into separate large blocks - South American, African, Indian, Australian and Antarctic, and between them the depressions of the Indian and South Atlantic oceans are completely formed. Similar processes occur on Angarid, which splits into two parts: Eurasian and North American; a depression in the northern part of the Atlantic Ocean is formed between them. Obviously, the formation of the Arctic Ocean depression is associated with the same time.
On the African and Hindustan