Our Earth-Paleogene (the Rise of Mammals)

The end of Cretaceous marks the end of Mesozoic and the beginning of Cenozoic in geology. Paleogene maps show what the earth looked like 45 million years ago. With the interruption of contact between Norway and Greenland, the Atlantic Ocean is still expanding, while the United States has moved westward. Africa slowly moved to the southeast and squeezed with southern Europe, forming the Pyrenees and Alps. India is still moving north across the equator. Australia has been completely separated from Antarctica. Paleogene is a period of large-scale orogeny and global land and sea remodeling. Africa and India continued to move northward, and the Paleo-Tethys Ocean gradually closed. Due to the collision between Gondwana block and the south side of Eurasia, the sedimentary strata were squeezed, so a series of orogenic movements began along the Alps to the Himalayas. In the far west, the Iberian Peninsula (Spain and Portugal) collided with France, which led to the formation of the Pyrenees.

Crustal movements occurred frequently during this period. At the same time, modern animals that record mammals to songbirds have become the masters of the world. Paleogene lasted from 66 million years ago to 23 million years ago. Traditionally, these 43 million years are divided into three periods, namely, Paleocene (66 million to 56 million years ago), Eocene (56 million to 43 million years ago) and Oligocene (34 million to 23 million years ago).

1 The ocean is shrinking in America. During the Cretaceous, a shallow sea covered the central and western parts of North America. In the Paleogene, only a small piece of remains called the Shell Sea remained. Due to the continuous plate movement that formed the Rocky Mountain, the continent stretched and fractured, and the covered seawater retreated, forming a lake basin. One of them is the Uinta basin, where several layers of sediments have accumulated, forming the Green River Formation with exquisite fish fossil civilization.

Volcanoes in the Atlantic Ocean spewed a column of hot lava from the bottom of the North Atlantic between Great Britain and Greenland, jacking up, stretching and tearing the ocean crust in this area. In this process, a large number of magma spewed to the surface, forming a new landform. Traces of these explosions can be seen in the giant Tito in Northern Ireland and the finger hole in Staffa Island in Scotland.

The volcanic hot spots in the Pacific Ocean move up with a hot spot in the Pacific plate (the outcrop of the material upwelling to the surface in the deep mantle), and a chain of volcanic islands is formed here, which is called Hawaii-Imperial Seamount Chain. 70 million years ago, the first volcano erupted from the bottom of the sea. Plate movements have now moved volcanoes to the Pacific Ocean. About 43 million years ago, the movement direction of Taiping plate changed, and this change was preserved in the "broken line path" of submarine volcanic chain.

4 Climate change in Australia The rocks in South Australia and Queensland show that the weather in Australia changed in Paleogene. About 55 million years ago, the climate here was humid and there were a lot of swamp forests. They later became lignite and oil shale. The sediments here were much thinner 40 million years ago, indicating that the environment was not very good at that time. The rocks formed by these sediments are similar to sandstone, indicating that the area has become extremely dry.

The creator of the ridge was in Paleogene, where the ridge was once an active transform fault, that is, the boundary between two tectonic plates. When India finally collided with China and Tibet and stopped moving, the Indian Ocean was formed. Today, this ridge is silent, but it still stands at the bottom of India, at an altitude of 3000 meters.

Spain and Italy merged into the European continent. With the Iberian Peninsula (Spain and Portugal) rotating counterclockwise, the Bay of Biscay appeared. It collided with southern France and squeezed the middle stratum, forming the Pyrenees Mountains. Italy moved northward to southern Europe, pushing the Alps upward in the process of moving.

7 Arabia is separated from Africa. With the extension of the crust in northeast Africa, the Red Sea appeared. In the late Eocene (40 million years ago), a large amount of lava poured into the vast area of the Ethiopian plateau, and a volcanic belt appeared along the rift valley.

At the beginning of Paleogene volcanic activity, the expansion of the North Atlantic was extremely slow. At the turn of Cretaceous and Paleogene about 65 million years ago, Greenland and the British Isles were still connected with each other, but Iceland had not yet appeared. From 63 million years ago to 52 million years ago, there was a large-scale volcanic movement in this area. A large number of lava erupted from a series of cracks extending from southwest to northeast, covering the whole land. These volcanic eruptions may be due to the eruption of a hot spot, leading to the eruption of hot magma from the interior of the earth. With the extension of continental crust, Eurasia and Lauren split and a new Atlantic seabed was formed. The submarine expansion covers most of the area between Norway and Greenland. Iceland was formed by magma erupting from the mid-Atlantic ridge and is still above the hot spot.

The Atlantic Ocean continued to expand northward in Paleogene. The crust under the ocean is pushed up by "hot spots" from the depths of the mantle. With the dispersion and division of the earth's crust, a large number of lava erupted from cracks, and a series of large volcanoes were distributed from Dingle in southwest Ireland to the east of Greenland. At this time, Iceland was formed, and Greenland was separated from Navia, Skand.

The sea level continued to decline from the highest point in the middle Cretaceous. But in detail, the whole Cenozoic sea level has been fluctuating. During the Paleogene, the global climate gradually became humid, which extended the tropical and subtropical climate to high latitudes. However, since the end of Eocene, the global climate has gradually become dry and cold. This has had a great impact on the overall development of marine and terrestrial life.

After the extinction of modern life at the end of Cretaceous, with the revival of life, animals and plants have been sharply divided. In the marine environment, life quickly becomes active and takes on a more modern look. Skeletal fish in bony fish and sharks in cartilaginous fish become dominant. In addition, the earliest marine mammals, such as primitive whales, appeared.

Messer's flora and fauna The messer mining area in Frankfurt is one of the most important fossil sites of Paleogene life in the world. About 50 million years ago, this place was a lake, surrounded by many plants, vertebrates and invertebrates. These words represent a relatively complete ecosystem.

A variety of mammals Although mammal fossils account for only a small part (2%-3%) of vertebrates unearthed in messer, there are 35 different species belonging to 13 orders. These purpose still exist today. although mammals in Messer are quite different from modern mammal in size, they can still be identified by their appearance. These include the 25 cm marsupial opossum and many bats and rodents. In addition, primates that can climb trees like lemurs have been found, such as European lemurs, which are 50 cm long. Primates use fingers instead of claws. Their forefinger and thumb can be used to grab and use tools. Lemurs, monkeys, humans and other orangutans all belong to primates.

At that time, the ancestors of horses were only as big as big dogs, and the ancestors of cattle and deer were smaller, about the size of rabbits. Other mammals include anteaters and some extinct early mammals.

The creatures in Messer mine are composed of 65 species of plants, which form the basis of the ecosystem in this area, and obviously have a modern appearance. Tropical citrus trees, palm trees, climbers and camphor trees are widely distributed. Oaks, water lilies and rare conifers, which are mainly distributed in temperate regions today, also showed signs of growth at that time. There are many water lilies, rich animals and insects in the freshwater lake, such as Daphnia, midges and midges.

These insects are the food of frogs, toads and salamanders. Groups of carnivorous fish, aquatic reptiles (such as freshwater turtles) and carnivorous crocodiles up to three meters long occupy the lake.

The first snake fossil was produced in the late Cretaceous, and its ancestor is still unknown. The types of snake fossils are mang snake, barrel snake and digger snake. Pythons are more than two meters long and feed on small animals.

The appearance of birds has gradually changed, from the flightless mystery bird to the eagle, chicken and goose, flamingo, owl and ostrich. This biological cluster covers all kinds of modern Europe, North America, South America and South Asia.

Lava is in Northern Ireland and hebrides. Many basalts erupted from cracks and volcanoes, some of which are still visible today. There are still about 3800 square kilometers of lava in Northern Ireland. Antrim's huge staircase is also one of many visible volcanic eruption ruins.

The second stage of volcanic activity is the volcanic belt formed from Ireland to the west coast of Scotland. Although the rocks are hard, these extinct volcanoes were severely eroded by glaciers in the last ice age (1.8 million years ago), which made it easier for scientists to study them.

The investigation of volcanic rocks in this area provides important clues for studying their formation. The magma that constitutes rocks has also undergone a series of changes in composition. In different periods, minerals precipitated from magma have different crystals, and some rocks have been layered. A stratum was found on Ram Island on the south coast of Scotland, which confirmed that Cenozoic rocks were caused by mantle hot spots. This stratum is rich in platinum group minerals, which is closely related to the high temperature during the mantle plume activity.

The evolution of plants and flowers When it comes to the early evolution of terrestrial plants, our understanding mainly comes from Rainey, Scotland. In 390 million years of sediments, there are 22 species of plants, including the original plant Dryopteris Rainii, which circulate water through their veins. These erect plants live in swamps and are 20 to 30 cm high.

Differentiation of Mammals The differentiation of mammals was obvious in Paleogene. During the Paleogene and Neogene (also known as Tertiary) lasting 63 million years, 4,000 species of mammals will evolve, most of which were realized in the Paleocene 654.38+00 million years ago, including at least 654.38+05 new lineages-groups composed of close relatives. The appearance of angiosperms (flowering plants) in this period stimulated the differentiation of some mammals (many of which are herbivores). Mammals may have intelligence and adaptability in order to survive and reproduce in a rapidly changing environment.

Greer's mouse was discovered in messer. It is 75 cm long and is an extinct mammal. Its hind legs are long, its forelimbs are short, and its tail is used to keep balance. It seems to jump, but the nostalgic structure shows that it actually ran when hunting small animals.

Python pythons and pythons in the Paleogene belong to pythons, and they can suffocate their prey. Ancient pythons were two meters long and fed on small reptiles, birds and mammals. This poisonous snake did not appear until the Miocene in the third season.

At the crossroads, anteater (European anteater) and pangolin (pangolin) appear in Europe, which is of great significance. People used to think that they belonged to South America and Southeast Asia respectively, so Europe became the crossroads of Eocene mammal migration.

Primitive centaurs found 70 horse fossils in messer, including foals and pregnant mares. The ancient beast horse has four toes on the front foot and three toes on the back foot, and its shoulder height is only 60 cm.

The columnar basalt in the Sugar Cave is located on Staffa Island on the west coast of Scotland. The cooled basalt formed pillars supporting the cave, which was named after a mythical giant. This basalt is part of a rock with a thickness of 2000 meters, which erupted from the nearby Moore Island in Paleogene.

The Paleogene in China generally inherited the paleogeography and paleoclimate characteristics of the Late Cretaceous. Most of our country is land, only southern Tibet and Tarim basin are still oceans. They were connected with East Asia and the ancient Mediterranean Sea, forming a long and narrow ancient Tethys sea area, and Taiwan Province Province at that time also sank into the sea. 10.3 billion years ago, the Indian plate broke away from the Pan-continent composed of Africa, Antarctica and Australia in the southern hemisphere and began to drift northward. By the middle of Paleogene about 40 million years ago, it collided with Central Asia and Tibet and formed Himalayan orogeny. The ancient Tethys sea area rose to the land, and the previously deposited strata were folded and fractured to varying degrees. It also caused the rapid uplift of the terrain in the western part of China, which caused the Shanxi-Shaanxi basin and the southwest basin in China to rise to the Loess Plateau and Yunnan-Guizhou Plateau respectively in the late Paleogene, and formed large subsidence basins such as North China Basin, Songliao Basin, Jianghan Basin and Subei Basin in the east. Especially Bohai Bay, Yellow Sea and Taiwan Province Strait, all belonged to land at that time. Therefore, very thick Paleogene continental strata were deposited in these places. However, the East China Sea and the South China Sea still belong to the ocean, where marine strata are deposited.

Paleogene is an important metallogenic period of coal, oil, gypsum and salt deposits in China. Coal mines are mainly distributed in Northeast China, Shandong, Hebei and Shanxi, among which Fushun, Liaoning is the largest. Oil is mainly distributed in Songliao Basin, Bohai Bay, Jianghan Basin, Nanyang Basin, Junggar Basin, Qaidam Basin, Tarim Basin and Subei Basin. These places are oil fields formed by continental strata. However, in the west of Taiwan and Kashi Bay in the southwest of Tarim, as well as in the East China Sea and South China Sea, oil fields are formed by marine strata. Because the climate was dry in the early Paleogene, it turned warm and humid in the later period. Therefore, Kashi Bay in the early west, Lanping, Simao and Sanshui basins in Guangdong in the south, Jianghan basin and Hengyang basin in the east are all plateau deposits. Potash ore was also found near Dawenkou, Shandong Province.