The movie "Jurassic Park" is familiar to everyone, but do you know that there is a "Cretaceous Park" in the west of Liaoning Province? Compared to the movies, the wonders created here are real: since the early 1990s, important fossils have emerged. Starting with fish, to amphibians, reptiles (turtles and turtles, lizards, apatosaurs, pterosaurs, theropods, sauropods, ornithopods), birds, all the way to mammals, and many angiosperms. For scientists studying paleontology, Liaoxi is a natural treasure trove of fossils, and all this stems from the unique paleogeographic background and burial environment of Liaoxi.
<h1>Western Liaoning and Rehe biota</h1>
Chaoyang and Jinzhou in western Liaoning are the core areas of the Rehe biota, and the surrounding areas are also widely distributed, such as Chifeng in the southeast of Inner Mongolia and Chengde in the north of Hebei Province. Because these areas originally belonged to the Rehe Province, as early as 1928, the American geologist Greep first used the "Rehe Fauna" in his book to name a series of discoveries he had made. Subsequent discoveries were not limited to animals, but also plants, so the "Rehe Biota" was formed. The controversy over the Age of the Rehe Biota has lasted for nearly a century. Through the discovery of the past decade or so, judging from the vertebrate combination, its age should belong to the Early Cretaceous, and isotopic ageing has also verified this conclusion. That is to say, the era of the Rehe biota dates back to 1. 3～1． 200 million years.
In recent years, due to the widespread concern of the Rehe biota, many places in western Liaoning that were not originally well known have become famous. A large number of Confucius birds, feathered dinosaurs Chinese dragon birds, Beipiao dragons, Chinese birds and their fish, amphibians, turtles, lizards, pterosaurs, horned dragons and mammals, etc., has now become one of the most famous fossil sites in the world, its popularity even surpasses the German Archaeopteryx Saurenhofen, adjacent to the jianshan ravine has long ago found a large number of fish, invertebrates and plant fossils, and later caused a sensation because of the excavation of the first primitive bird Confucius bird specimens and mammals Zhang He beast • Fossils of theropod dinosaurs with real feathers, primitive ancestral birds, and other vertebrate fossils were found in Zhangjiagou.
<h1>The "city of Pompeii" in the Cretaceous</h1> Period
Why are there such rich and diverse fossils of paleontology in western Liaoning? Why are they so well preserved and so beautifully preserved?
Let's first look at what really happened to Pompeii nearly 2,000 years ago: the ancient italian city was buried by the powerful eruption of Mount Vesuvius in 79 AD. In 1784, archaeologists discovered the ancient city inside the ash layer, and some people, some animals, and some other things in the city were very well preserved and vivid. The reason is that after the volcanic eruption, the entire city was quickly buried by volcanic ash, making it completely stuck in this moment of history.
The reason why Liaoxi is so rich in biological fossils is also the reason. Through field expeditions and fossil excavations, scientists have found that the Rehe biota has had frequent volcanic eruptions. Sudden natural catastrophes caused by volcanic eruptions result in sudden death, which is then quickly buried in volcanic ash.
As we all know, volcanic eruptions are the most serious natural disasters, and they are also considered to be one of the main reasons for the death of biological clusters and even the extinction of global biological clusters in geological history. Volcanic action directly and indirectly leads to the death of biological clusters, and the large amount of lava flows and hot pyroclastic flows from volcanic eruptions directly reduce the surrounding close-up organisms into ashes, the scope of influence is relatively small, it is a local effect, and fossils are difficult to preserve. The most important impact is that large-scale volcanic eruptions cause changes in the earth's atmosphere and hydrosphere, resulting in sudden changes in climate and environment and resulting in the death or extinction of biological clusters, which is a regional or even global catastrophe event, which is characterized by a large scope and degree of influence, a large number of fossils, and complete preservation.
In the western Liaoning region, dozens of vertebrate swarm deaths can now be confirmed. For example, the death of the Confucius bird swarm in the Sihetun area. Excavation statistics show that the average of Confucius bird fossils is 1 piece of 5-6 square meters, and the local area is 1-2 square meters of 1 piece, which shows that its abundance is not caused by normal death. The fossils are extremely well preserved and exquisite, not only the hard part of the skeleton is preserved completely, but also the soft parts such as feathers are preserved, and the body feathers, flying feathers and two long tail feathers and their feather branches and feather shafts are clearly visible. Bird fossils have their forehand limbs and tail feathers stretched out and their necks stretched forward, clearly reflecting unnatural death. In addition, the fossils of Confucius birds are all adult individuals, and no juvenile individuals have been found. When a sudden volcanic eruption occurs, birds avoid the danger of continental volcanic eruptions as much as possible, and adult individuals have well-developed feathers and strong flight ability, and have the ability to fly to the middle of lakes with relatively little danger and far from the shore. This explains why only adult bird fossils are found in the semi-deep-deep lake environment.
In addition, some dinosaurs still retain undigested food in the stomach cavity - the skeletons of lizards and mammals, the abdomen retains intact egg fossils, and the egg shell clearly preserves the ornamental structure. The burial status and preservation characteristics of these fossil groups are a true record of volcanic eruptions and the rapid instantaneous burial of fossils, which is a direct reflection of unnatural deaths.
<h1>Several major factors that form fossils</h1>
To form a fossil, several factors must be present: the first is that the biota should be very rich, and the second is the way the organism died, whether it was a normal death or a catastrophic death. For example, earthquakes or volcanic eruptions, this kind of catastrophic death can often enable a large number of organisms to be preserved in a concentrated manner; the third is the distance of the transport, that is, to see whether the organisms are buried in situ, or buried in a different place, and the fourth is the burial speed, that is to say, whether the organisms are buried quickly or for a period of time exposed to the surface of the slow burial, the fifth is the buried environment, whether the oxidation environment or the reduction of the environment is finally time. Let's analyze them one by one.
Biota Various evidence now shows that the climate of western Liaoning in the early Cretaceous is warm and humid, with abundant rainfall, connected lakes, and relatively developed vegetation, which is very suitable for biological growth and development. There are many creatures on land, fish in the water, aquatic reptiles, birds in the air, insects, pterosaurs, etc., which form a good food chain. At that time, angiosperms, that is, flowering plants, appeared, and some insects that picked flowers flourished in large numbers. And if the bird wants to eat these insects, it has to take the initiative to fly. In short, the environment at that time was very suitable for the large-scale reproduction and evolution of organisms.
Volcanic eruptions in western Liaoning were very frequent at the time, and this volcano was a medium acid volcano, and the eruption was not a large amount of lava magma, but mainly toxic gases, such as hydrogen sulfide, sulfur dioxide, and volcanic ash. And the eruption also caused fires in terrestrial forests, and researchers found a lot of carbon chips in the formation, which is evidence of forest fires. Beneath each layer of volcanic ash there are a large number of creatures buried. It was volcanic eruptions that caused their deaths, abnormal sudden cluster deaths.
If the organism is buried in situ after death, then it should be well preserved, and if it is transported for a long time, it will not preserve a good skeleton, nor can it preserve the tissue of the soft body. An interesting discovery is that many birds and dinosaurs are living on land, but their fossil burial sites are some lake deposits, and they are semi-deep lakes and deep lakes, and there is a distance from the environment where the land lives, and it is reasonable to say that it is carried over a certain distance. Careful observation of the original buried state of the fossil during field excavations shows that this transport is not carried out after the creature dies, but on its own initiative while it is alive, in order to escape the forest fire or toxic gases produced by volcanic eruptions.
Burial speed Burial speed is also a very critical factor, if the burial speed is fast, it can preserve very good fossils, if the burial speed is slow, after a period of exposure to the surface, the organic matter decays and oxidizes, and cannot preserve good fossils.
Burial environment To see whether it is an oxidizing environment or a reduced environment, the general fossil is often well preserved if it is in a reduced environment, and if it is exposed to the surface in an oxidizing environment, it will soon decay and the fossil will not be preserved. Therefore, many specimens found in Western Liaoning are a kind of deep lake environment, which is quickly deposited at the bottom of the lake, and volcanic ash is quickly covered and buried, which is a state of restoration.
Time The formation of fossils takes a certain amount of time, and the fossil formation time of the Rehe biota is very long, about 100 million years ago.
The western Liaoning region just meets all the conditions for the formation of fossils, so it has become a "cornucopia" of paleontological fossils. The reason why people like this unique treasure land is because they can understand the radiation, extinction and mutual relationship between the Rehe biota and its interaction with the environment. Throughout the evolutionary history of the earth, the period of the greenhouse effect of the earth is precisely the period of biological development, and the reason why the Rehe biota radiates so widely is also the environmental changes of volcanic eruptions, increased carbon dioxide and increased temperature of the earth, which have a positive impact on terrestrial and shallow sea organisms. More importantly, the prototype of the ecosystem on the earth was formed in this period of the Mesozoic Era, and angiosperms, birds, mammals, and the current distribution pattern of sea and land began to diverge from this period, so the study of the Rehe biota is also of great significance to today's earth.