Paleogene period - the time of formation of mammals. Characteristics of the Paleogene period

Some periods of geological history of the Earth, Paleogene, Devonian, Cambrian, for example, are characterized by intensive changes on land. So, 570 million to 480 million years ago, suddenly arose a lot of fossils. 400 million - 320 million years ago, peaks were reached by mountain-building movements. Seeds began to spread on land, amphibians appeared. It is believed that these are the most active periods of the Earth's geological history. Paleogene p-d is distinguished by the complexity of the structure of the cortex. In many ways, it was close to modern.

Features of natural conditions

In general, during the formation of the structure of the crust on the planet, a relatively high temperature was maintained. This is evidenced by the prevalence of desert conditions, the spread of reptiles, the evolution of insects (Paleogene, Permian). Triassic period marked the emergence of primitive mammals, the first dinosaurs. On land, coniferous trees predominated from plants. In the Paleogene period, the climate was mild. In the equatorial part, the temperature could reach 28 degrees, and in the area near the North Sea - 22-26.

Zoning

During the Paleogene there were five belts:

• 2 subtropical.
• Equatorial.
• 2 tropical.

High temperatures promoted active weathering. Relics of laterite and kaolinite cords and products of their redeposition are known on the Brazilian shield, in California, India, Africa and on the islands of the Indo-Malayan archipelago. The equatorial part began to develop moist evergreen forests. They had some similarities with the existing massifs in Equatorial Africa and Amazonia. Wet tropics were typical for the territories of Western Europe, the United States, southern and central areas in Eastern Europe, the western parts of China and Asia. Evergreen moisture-loving forests were distributed in the southern zone. Here, ferriallite and lateritic weathering occurred. The southern tropics covered the central parts of Australia, some areas of South. America and southern Africa.

Subtropics

They were distributed in the north of the United States and the East European Platform, southern Canada, Japan and the Far East. Together with evergreen vegetation, broadleaf plantings were widespread on 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 dominated in the territories of the far north of the North American continent, in Kamchatka and in Eastern Siberia. During the Eocene, the dimensions of the tropical and equatorial belts will expand considerably, the conditions of the subtropics will shift far to the circumpolar regions.

Characteristics of the Paleogene period

It began 65 million, and ended 23.5 million years ago. As an independent unit, the Paleogene period was singled out by Naumann in 1866. Until then, 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 propagated over quite extensive areas in the geosynclinal folded belts. Their area, in comparison with the beginning of the Mesozoic, significantly decreased in the Pacific region. Here, by the beginning of the Cenozoic era, extensive folded mountain areas appeared. In the northern hemisphere were North America and Eurasia. These two platform arrays consisted of ancient and young formations. They were divided by the depression of the Atlantic Ocean, but in the area of the Bering Sea that existed 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 bound up to 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 distributed exclusively in high latitudes. In the equatorial part, forests dominated, in which mainly ficus, palm trees and a variety of sandalwood species grew. In the interior of the continents, woodlands and savannahs predominated. The middle latitudes were a place of distribution of hygrophilous tropical plantations and plants of temperate latitudes. There were treelike ferns, sandalwood, bread and banana trees. In the high latitude region, the species composition changed drastically. Here in the Paleogene period araucaria, thuja, cypress, oak, laurel, chestnut, sequoia, myrtle grew. All of them were typical representatives of the flora of the subtropics. Vegetation in the Paleogene period was beyond the Arctic Circle. In America, Northern Europe and the Arctic, coniferous-deciduous deciduous forests predominated. However, these plants also grew into the subtropical plants mentioned above. Their development and growth was not particularly influenced by the polar night.

Sushi Fauna

Animals in the Paleogene period were fundamentally different from those that were before. Small primitive mammals appeared instead of dinosaurs. They inhabited mainly the forest zone and swamps. The number of amphibians and reptiles has significantly decreased. Spiny animals began to spread, swine and tapir-like, indicotheria (reminiscent of rhinoceroses). Most of them were adapted to spend most of the time in the water. In the Paleogene period the planet was also inhabited by the ancestors of horses, rodents of different species. Somewhat later creodonts appeared (predators). The tops of trees began to be occupied by toothless birds. Savannah inhabited rapacious diatribes. They were not able to fly birds. Insects were represented in a wide variety of species. At the beginning of the Paleogene, lemurs began to appear - representatives of the most primitive group of primates - semi-poor. Also land began to inhabit large marsupials. Among them are both herbivorous and predatory representatives.

Marine representatives

In the Paleogene period came the flowering of bivalves and cephalopods. Unlike previous species, they inhabited not only saline waters, but also brackish water, as well as fresh basins. Some of the gastropods settled in the lowlands. Among other invertebrates, marine irregular hedgehogs, sponges, bryozoans, corals, and arthropods have become particularly common. In a smaller amount, decapod crustaceans were represented. In particular, they include shrimp and crayfish. The role of brachypods and bryozoa decreased significantly in comparison with earlier periods. As a result of recent studies, it was found that representatives of nanoplankton-microscopic coccolithophytes-had a special significance among organisms at that time. The flowering of these golden algae falls on the Eocene. Together with them the rock-forming value was of siliceous and diatomaceous flagellates. The seas were also inhabited by vertebrates. Among them, the most widespread were the bony fishes. Also in the sea were representatives of cartilaginous - rays and sharks. Ancestors of whales, sirens, dolphins began to appear.

Eastern European Platform

During the Paleogene, as well as the Neogene period, the formations were located in continental conditions. The exception were their outlying parts. They experienced slight deflections and began to become covered with shallow seas. The development of the Eastern European platform in the Cenozoic is associated with changes in the Mediterranean belt. At first, mostly subsidence, and then - major uplifts. In the Paleogene the southern part of the platform bent, which adjoined the Mediterranean belt. In shallow-water seas, carbonate-clayey and sandy deposits began to accumulate. By the end of the Paleogene, the pool began to decline rapidly, and in the next period - the Neogene - the continental regime was formed.

Siberian platform

She was somewhat in a different situation than the Eastern European. During the Cenozoic era, the Siberian Platform was represented in the form of a highly elevated erosion area. The mountain system of the northeastern direction began to form. The height of the chains increased in the direction of the uplift, which is called the Baikal vault. Towards the end of the era, a mountain relief appeared, with individual peaks reaching 3,000 meters. A system of long and narrow basins formed in the axial part. They stretched for a distance of more than 1.7 thousand kilometers from the Mongolian border to the middle reaches of the river. Olekma. The largest is the depression of the lake. Baikal - the maximum depth is 1620 m.