Some periods of the geological history of the Earth, the Paleogene, Devonian, Cambrian, for example, are characterized by intense changes on land. So, 570 million - 480 million years ago, a lot of fossils suddenly appeared. 400 million - 320 million years ago, mountain building movements reached their peak. On land, seed plants began to spread, and amphibians appeared. It is believed that these are the most active periods of the geological history of the Earth. The Paleogene p-d is distinguished by the complexity of the crust structure. In many ways, it was close to modern.
Features of natural conditions
In general, during the formation of the structure of the crust, the planet maintained a relatively high temperature. This is evidenced by the predominance of desert conditions, the spread of reptiles, and the evolution of insects (Paleogene, Permian). The Triassic period marked the appearance of primitive mammals, the first dinosaurs. On land, conifers dominated from plants. During the Paleogene periodthe climate was mild. In the equatorial part, the temperature could reach 28 degrees, and in the area near the North Sea - 22-26.
Zonality
There were five belts throughout the Paleogene:
- 2 subtropical.
- Equatorial.
- 2 tropical.
High temperatures contributed to active weathering. Relics of lateritic and kaolinite crusts and products of their redeposition are known on the Brazilian Shield, California, India, Africa, and the islands of the Indo-Malay archipelago. In the equatorial part, moist evergreen forests began to develop. They had some similarities with the arrays that exist today in Equatorial Africa and the Amazon. Wet tropics were typical for the territories of Western Europe, the USA, southern and central regions in Eastern Europe, western parts of China and Asia. Evergreen moisture-loving forests were distributed in the southern zone. Ferriallite and lateritic weathering took place here. The southern tropics covered the central parts of Australia, some areas of the South. America and southern Africa.
Subtropics
They were distributed in the northern United States and the East European Platform, southern Canada, Japan and the Far East. Together with evergreen vegetation, broad-leaved plantations were common in these territories. In the Southern Hemisphere, the subtropics were distributed in the south of Chile and Argentina, in New Zealand and South. Australia. The average surface water temperature in the epicontinental seas of the belt was no more than 18 degrees. Probably,conditions close to moderate prevailed in the territories of the extreme north of the North American continent, in Kamchatka and in Eastern Siberia. During the Eocene, the size of the tropical and equatorial belts will expand significantly, the conditions of the subtropics will shift far to the polar regions.
Characteristic of the Paleogene period
It started 65 million years ago and ended 23.5 million years ago. As an independent division, the Paleogene period was identified by Naumann in 1866. Until that moment, it was included in the tertiary system. In the structure of the crust, along with the ancient platforms, there were also young ones. The latter spread over fairly large areas in geosynclinal folded belts. Their area, in comparison with the beginning of the Mesozoic, has significantly decreased in the Pacific region. Here, by the beginning of the Cenozoic era, vast folded mountainous areas appeared. North America and Eurasia were in the northern hemisphere. These two platform arrays consisted of ancient and young formations. They were separated by the depression of the Atlantic Ocean, but in the region of the Bering Sea that exists today, they were connected. In the southern part of the mainland Gondwana no longer existed. Antarctica and Australia were separate continents. South America and Africa remained connected until the middle of the Eocene.
Flora
The Paleogene period of the Cenozoic era was distinguished by the widespread dominance of angiosperms and conifers (gymnosperms). The latter were distributedexclusively at high latitudes. In the equatorial part, forests dominated, in which ficuses, palms and various representatives of sandalwood grew mainly. In the depths of the continents, woodlands and savannahs predominated. The middle latitudes were the place of distribution of moisture-loving tropical plantations and plants of temperate latitudes. There were tree ferns, sandalwood, breadfruit and banana trees. In the region of high latitudes, the species composition changed dramatically. Araucaria, thuja, cypress, oak, laurel, chestnut, sequoia, and myrtle grew here in the Paleogene period. All of them were typical representatives of the subtropical flora. Vegetation in the Paleogene period was beyond the Arctic Circle. In America, Northern Europe and the Arctic, coniferous-broad-leaved deciduous forests predominated. However, the subtropical plants mentioned above also grew in these territories. Their development and growth were not particularly affected by the polar night.
Sushi fauna
Animals in the Paleogene period were radically different from those that were before. Instead of dinosaurs, small primitive mammals appeared. They inhabited mainly the forest zone and swamps. The number of amphibians and reptiles has significantly decreased. Proboscis animals, pig-like and tapir-like, indicothere (reminiscent of rhinoceroses) began to spread. Most of them were adapted to spend most of their time in the water. In the Paleogene period, the planet also began to be inhabited by the ancestors of horses, rodents of various species. Somewhat later, creodonts (predators) appeared. Topstrees began to occupy toothless birds. The savannas were inhabited by predatory diatryms. They were non-flying birds. Insects were presented in a wide variety of forms. At the beginning of the Paleogene, lemurs began to appear - representatives of the most primitive group of primates - semi-monkeys. Also, large marsupials began to inhabit the land. Both herbivorous and predatory representatives are known among them.
Marine Representatives
In the Paleogene period, bivalves and cephalopods flourished. Unlike previous species, they inhabited not only s alty waters, but also brackish and fresh waters. Some of the gastropods settled in the lowlands. Among other invertebrates, sea irregular urchins, sponges, bryozoans, corals, and arthropods have become especially common. Decapod crustaceans were represented in smaller numbers. These include, in particular, shrimp and crayfish. The role of brachoipods and bryozoans has significantly decreased in comparison with earlier periods. As a result of recent studies, it was found that representatives of nanoplankton, microscopic coccolithophrids, were of particular importance among organisms at that time. The heyday of these golden algae falls on the Eocene. Along with them, siliceous and diatom flagellates had rock-forming significance. The seas were also inhabited by vertebrates. Among them, bony fish were the most widespread. Also in the sea there were representatives of cartilaginous - stingrays and sharks. Becomethe ancestors of whales, sirens, dolphins appear.
East European Platform
During the Paleogene, as well as the Neogene period, formations were located in continental conditions. The exception was their marginal parts. They experienced slight bowing and began to be covered by shallow seas. The development of the East European Platform in the Cenozoic is associated with changes in the Mediterranean belt. First, mainly lowering, and then - large uplifts. In the Paleogene, the southern part of the platform sagged, which adjoined the Mediterranean belt. Carbonate-argillaceous and sandy sediments began to accumulate in shallow seas. By the end of the Paleogene, the basin began to decrease rapidly, and in the next period - the Neogene - a continental regime was formed.
Siberian platform
She was in somewhat different conditions than the Eastern European. During the Cenozoic era, the Siberian Platform was represented as a fairly high-lying area of erosion. The mountain system of the northeast direction began to form. The height of the chains increased towards the uplift, which is called the Baikal arch. By the end of the era, a mountainous relief appeared, some peaks of which reached 3 thousand meters. A system of long and narrow depressions formed in the axial part. They stretched over a distance of more than 1.7 thousand km from the Mongolian border to the middle reaches of the river. Olekma. The largest is considered the depression of the lake. Baikal - maximum depth - 1620 m.
