Life

Unveiling the Tarim Basin: From Ancient Ocean Floor to Modern Oasis

This is a terrifying desert in the heart of Asia, but it was also an ancient land mass surrounded by oceans.

The mountains here have witnessed the closure of ancient oceans one by one. The river here looks up at the uplift of the Qinghai-Tibet Plateau.

This is the Tarim Basin, one of the most desirable places for all geologists on earth.

A huge “Book of the Earth” is spread out silently here, leaving behind riddles of the ancient earth with traces of various rocks and minerals. This is a place where relics from ancient times accumulate. A large amount of geological, geochemical and geophysical information is spread luxuriously and randomly among the complex ancient strata.
The “largest basin” in China, please call me “Talim Craton”

When talking about the Tarim Basin, most people will think of it as the huge “basin” in northwest China, which contains the largest amount of sand in China – the Taklimakan Desert.

More often, the Tarim Basin is known as part of Xinjiang. When describing the topographic features of Xinjiang, one of the most commonly used descriptions is “three mountains and two basins”. Looking from north to south, the beautiful land of Xinjiang is straddled by three mountain ranges running east to west: Altai Mountains, Tianshan Mountains and Kunlun Mountains. Between the three are the Junggar Basin and the Tarim Basin. In fact, in the southeast, there is a smaller brother, the Qaidam Basin, which is closer to the Tarim Basin, but because it is already located in Qinghai Province, it is not included in the “Three Mountains and Two Basins”.

From the perspective of the shape of the earth’s surface, Tarim is the “largest basin” on the land of China: 520 kilometers at its widest point from north to south, 1,400 kilometers at its longest point from east to west, and covering an area of ​​more than 400,000 square kilometers. Data proves that it is the largest inland basin in China. There are Tianshan Mountains in the north, Kunlun Mountains and Altyn Mountains in the south. The entire basin is higher in the west and lower in the east, with an altitude ranging from 800 meters to 1,300 meters.

But “number one” is still not its most shining title. There are numerous large and small basins in China, but only Tarim can be called a “cratonic basin”.

“Craton” is a geological term derived from the Greek “Kratos” meaning “strength”. Specifically refers to stable continental blocks formed hundreds of millions of years ago. They exist widely on the earth. For hundreds of millions of years, cratons have floated above the deep asthenosphere of the earth and have survived several collisions of continental blocks. This is because they have hugely thick lithospheric mantle roots with many thicknesses. More than 200 kilometers. As an ancient and important earth surface structure, once a very rigid craton is formed, it can maintain its stability and not be disturbed by subsequent geological changes. The most typical one is that there is no obvious seismic activity.
It is no exaggeration to say that the stability of the earth’s surface depends entirely on cratons.

There are three major cratons in mainland China: the North China Craton, the Yangtze Craton and the Tarim Craton. According to current research, the Yangtze Craton and the Tarim Craton once belonged to a supercontinent in the southern hemisphere. After they decomposed, they drifted to the northern hemisphere and gathered together with the North China Craton to form the main body of the landmass where China is located. Over the next hundreds of millions of years, some new land masses of different sizes were gradually merged into this craton complex, and as the Indian Plate carried the Himalayan terrane, they collided and joined, eventually forming the shape of China’s territory.

Therefore, in China, only the Tarim Basin is the most special. When geoscientists studied the uplift of the Tibetan Plateau, they discovered that because it is located on the edge of the Tibetan Plateau, it faces the impact of the collision of the Indian and Eurasian plates – which is equivalent to being on the front line of the most magnificent orogeny on earth – the Tarim Basin and Qaidam Basin. Damu Basin had a mixed response.

From a geological point of view, today’s Qaidam Basin has been completely integrated into the Tibetan Plateau and has undergone overall deformation with it, while the Tarim Basin still retains its own mechanical integrity, which means that it is still independent of the Tibetan Plateau. geological structure. The reason is that as a craton basin, Tarim has the most solid crystallization base – the earliest layer, which even originated from the Proterozoic period hundreds of millions of years ago.

Yes, at that time, the infant Tarim could not be called a craton. It was immersed under the warm ocean in the southern part of the earth, growing from a “terrestrial core” into a “platform.” Floating around it are flourishing blue-green algae. These simple organisms are desperately inhaling carbon dioxide and spitting out oxygen, laying the most important foundation for the emergence of animals in the future.

As one of the oldest continental massifs in the world, the fate of the Tarim Craton cannot be simply summarized by the vicissitudes of life. It is itself a great and magnificent earth epic. For ten thousand years, it expanded, squeezed, and rotated together with other land masses in the warm ocean of Mother Earth, sometimes emerging from the ocean surface and sometimes sinking to the bottom of the ocean. After crossing the equator and migrating from the southern hemisphere to the northern hemisphere, they witnessed the disappearance of the Tianshan Ocean, Kunlun Ocean and Qinling Ocean. In the end, like ancient marine animals, they moved to land and built the topographic structure of the inland basin with their own layer-by-layer deposition of marine creatures.

The Tarim Craton once faced the sea, but in the end it saw huge rocks growing into mountains and became the older neighbor beside the young and majestic Qinghai-Tibet Plateau.
Whose home was it? civilizations that disappeared

Starting about 50 million years ago, as the surrounding mountains rose, the climate in the Tarim area changed more and more intensely. For animals and plants, perhaps the most direct feeling is that there is less and less water. Today’s geologists can clearly see the desertification process of Tarim through the fossils of animals and plants in the Tarim formation. By 3 million years ago, the Qinghai-Tibet Plateau was so majestic that it could easily block the monsoon from the Indian Ocean from the south. In the once warm and humid Tarim region, the Taklimakan Desert was born almost simultaneously with humans.

If today’s Tarim Basin is like a huge basin, then the entire basin is filled with the Taklimakan Desert. As a child of the sea and the land, Tarim used the remains of the sea to create the Taklimakan, the largest desert in China and the second largest mobile desert on the earth.

Some geologists once traced the source of sand in this desert. With the help of a magnifying glass, they found that most of these fine gravels had a V-shaped imprint of the ocean. Only the transport and impact of waves will leave this mark on the gravel. Today’s people, standing on the edge of the desert basin and looking at the surrounding mountain valleys, can imagine that there was once the pass of the ancient strait. Tarim was once surrounded by a broad ancient ocean. The wind and sea continued to peel away the surrounding land, and the sea continued to deposit biological remains. After the ocean dried up, all these aggregates of sea and land formed an undulating sea of ​​sand amidst the destruction of the wind.

In the hinterland of the Taklimakan Desert, there is a place called “Mazhatage”. There is an exposed rocky mountain range here. The three colors of “red, white and yellow” are regularly distributed on the mountain, showing a wave-like visual effect of undulating layers. It is very eye-catching in the desert and is called “Red and White Mountain” by the locals.

Here is the “Earth Book” that geologists are crazy about. White rocks, namely gypsum, dolomite and limestone, are all rocks that can only be formed under the sea – Tarim has been immersed in the ocean several times over hundreds of millions of years. The red sand and mudstone was generated in lakes on land – as the ancient ocean gradually closed, Tarim began to emerge from the ocean, showing more of the characteristics of land. After that, the surface of Tarim forms the Taklimakan Desert, and the vast yellow sand covers all the white and red colors.

Until hundreds of thousands of years ago, the huge squeezing pressure brought by the Qinghai-Tibet Plateau finally raised this mountain range in the hinterland of the desert, silently telling the past of Tarim’s sea. It is this mountain range that divides the Taklimakan Desert into two completely different parts. In the southeast, you can also see desert plants such as Populus euphratica growing. Going to the northwest, it is an extremely arid climate area. Here, giant sand dunes tens of meters high stand clustered together – this area is the real “Sea of ​​Death.”

Hot and dry wind blows here all year round, raising endless wind and sand, pushing the sand dunes to move eagerly to the south.

Some people say that “Taklimakan” means “if you go in, you can’t get out.” There is also a theory that it is a legendary cursed city submerged under the desert. According to this view, “Takla” means “underground” and “Magan” means “home” and “place of life”. Then, Taklimakan is an “underground city” or “a city underground.” Some scholars also believe that “Takla” represents “Tocharians”, so Taklamakan should be the “homeland of Tocharians”.
Whose homeland was this terrifying desert?

The desert is surrounded by the Yarkand River, Tarim River, Hotan River and Cheershen River belonging to the Kunlun River System. As a desert basin, the water flowing down from the surrounding mountains will eventually collect in the basin itself. To the naked eye, it looks like the river has dried up in the desert. Perhaps wherever rivers flow, deserts will form oases, and life will appear. Archaeologists have discovered that starting from 5,000 years ago, there was a wet period accompanied by rivers in the Taklimakan Desert. This period coincided with the period of those ancient civilizations that disappeared. For example, at the Niya site where the Han Dynasty brocade “Five Stars Emerged from the East Benefited China” was unearthed, archaeologists found not only wind-made sand, but also river sand and still water sediments more than one meter thick.
Exploring “Underground Everest” Is there a vast ocean hidden under the ground?

The ancient continental core of the Tarim Basin has experienced the ups and downs of ocean sedimentation over hundreds of millions of years. The material combination caused by the mutual impact of various marine and continental plates eventually formed rich oil and natural gas resources. It is the largest oil and gas basin in my country. Among them, oil and natural gas resources buried at a depth of 6,000 meters to 10,000 meters account for 83.2% and 63.9% of the total reserves in the Tarim Basin respectively, so 80% of the country’s ultra-deep wells are distributed here.

However, the geological structure of the Tarim Basin is so complex that searching for oil and gas resources here is tantamount to finding a needle in a haystack. The writer Hu Lan once made a vivid analogy in his reportage: finding liquid oil in reservoirs below 8,000 meters in the Taklimakan Desert is equivalent to extracting oil and natural gas from a room-sized crack across a Mount Everest. Mined… It is difficult to climb Mount Everest, and it is even harder to climb “Underground Everest” in Tarim!

Since the founding of the People’s Republic of China, Chinese geologists and oilmen have never given up searching for treasures in deserts with harsh environments. After decades of hard work, good news finally came in Tarim——

In 2022, Well Fudong 1 in Tarim will become the fastest-producing oil field in my country’s deep underground field. In 2023, my country’s first 10,000-meter-deep well will be drilled in the Tarim Fuman Oilfield. In 2024, the designed vertical deep well of Tarim Deep Underground Taco No. 1 has reached 11,100 meters, and the country’s first 12,000-meter automated drilling rig independently developed by my country is operating here.

In addition to the sand sea and the oil sea, theoretically, there is an “underground sea” hidden deep under the Taklimakan sand dunes. To be precise, it is an ancient underground water layer deep in the Tarim Basin. Some people speculate that it may be the remaining water of the ancient ocean, while more people believe that it is accumulated by mountain rivers around the basin. From the surface, the river disappears into the dry desert, but if you stand under the desert, you may see a steady stream of water gathering together to form unusable “static water.” It is estimated that if this water is pumped above the ground, 30 square kilometers of Taklimakan can be submerged under tens of meters of water.

Of course, this is another story of great changes.

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