Tarim Basin

The largest inland basin in China. The basin lies between Tianshan, Kunlun and Altun Mountains. It is 1500 km long from east to west and 600 km wide from north to south, covering an area of 530000 square kilometers. The altitude is between 800 and 1300 meters. The terrain is high in the West and low in the East. In the middle of the basin is the famous Taklimakan Desert, with Piedmont, Gobi and Oasis (alluvial plain) on the edge.

Tarim Basin

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Tarim Basin is located in the south of Xinjiang, China

It is the largest inland basin in China. The basin lies between Tianshan, Kunlun and Altun Mountains. The widest part in the north and south is 520 kilometers, and the longest part in the East and West is 1400 kilometers, covering an area of about 400000 square kilometers

. The altitude is between 800 and 1300 meters, and the terrain is high in the West and low in the East.

Tarim Basin is a large closed Intermountain basin. Geologically, it is a stable block restricted by many deep faults. The terrain of the basin is high in the West and low in the East, with a slight North dip. The elevation of the old Lop Nur Lake is 780 meters, which is the lowest point of the basin. The Tarim River is located in the northern margin of the basin and flows eastward.

The basin landform is distributed in a ring, with the edge of Gravel Gobi connected with mountains, the center of vast desert, alluvial fan and alluvial plain between the edge and desert, and oasis distribution. To the south of Tarim River is Taklimakan Desert, which is the largest desert in China and the second mobile desert in the world. Tarim Basin has a warm temperate climate with an average annual temperature of 9-11 ℃ and a frost free period of more than 200 days. The main natural disasters are sandstorm and dry hot wind, mainly northeast wind and northwest wind, and the sand dunes on the edge of the basin move southward seriously.

The water in the basin mainly comes from the westerly flow. The precipitation in the basin is scarce, and the basin itself cannot form runoff. The larger rivers are Yeerqiang, Kizil, Gaizi, Hetian and Keliya in the south, and Aksu, Tailan, Weigan, Kuqa and Kaidu (Kongque in the lower reaches) in the North. The recharge of groundwater in the basin mainly comes from river bed, channel and field leakage. The dynamic reserves of groundwater are 11-14.8 billion cubic meters.

Along the southern foot of Tianshan Mountain and the northern foot of Kunlun Mountain, the basin is mainly composed of brown desert soil, cracked soil and residual saline soil, while the northern foot of Kunlun Mountain and Altun mountain is mainly composed of gypsum salt pan brown desert soil. Tarim Basin is rich in oil and gas resources, accounting for about 1 / 6 and 1 / 4 of China's oil and gas resources respectively.

Geology and geomorphology

geological environment

geological structure

Tarim Basin is a large closed Intermountain basin, which is a stable block restricted by many deep faults. The basement of the block is ancient crystalline rock, on which there are about 1000 meters thick Paleozoic and Proterozoic sedimentary overburden, and thin Mesozoic and Cenozoic sedimentary layers. The area of Quaternary sediments is large.

 

The tectonic Tarim Basin block is not consistent with the geomorphic Tarim plain. There are huge Mesozoic and Cenozoic continental deposits in the depression, with a maximum thickness of 10000 meters, which is a good aquifer. The basin is irregular rhombic, surrounded by high mountains. The terrain of the basin is high in the West and low in the East, with a slight dip to the north. The elevation of the old Lop Nur Lake is 780 meters. The lowest point of the basin is located in the northern margin of the basin, and the water flows eastward.

soil

Along the southern foot of Tianshan Mountain and the northern foot of Kunlun Mountain, the basin is mainly composed of brown desert soil, cracked soil and residual saline soil, while the northern foot of Kunlun Mountain and Altun mountain is mainly composed of gypsum salt pan brown desert soil. The alluvial plain along the lower reaches of the Tarim River and the lower reaches of the Tarim River is mainly composed of meadow soil and Populus euphratica forest soil. Meadow soil is widely distributed, and most concentrated on both sides of the river between Luntai and Yuli. Populus euphratica forest soil is developed under dense and shady Populus euphratica forest, characterized by high content of organic matter (more than 1% - 2%) and low salt content. Meadow soil and Populus euphratica forest soil are the main objects of agricultural reclamation. This causes forest damage, which is not conducive to environmental protection.

 

Geomorphological features

The terrain of the basin is high in the West and low in the East, slightly dipping to the north. The elevation of the old Lop Nur Lake is 780 meters, which is the lowest point of the basin. The Tarim River is located in the northern margin of the basin and flows eastward.

 

The basin landform is distributed in a ring, with the edge of Gravel Gobi connected with mountains, the center of vast desert, alluvial fan and alluvial plain between the edge and desert, and oasis distribution. To the south of the Tarim River is the Taklimakan Desert, covering an area of 337000 square kilometers, accounting for 20% of the area of Xinjiang and 26% of the total area of deserts and Gobi in China (43% for deserts alone). It is the largest desert in China and the second largest mobile desert in the world. Individual sand dunes move southward about 50-60 meters every year, and the area of mobile sand dunes accounts for 85%. The shape of sand dunes is complex, including pyramid shape, dome shape, fish scale shape, compound sand dune chain, compound sand ridge and so on.

 

Regional scope

The largest inland basin in the world is located in the south of Xinjiang Uygur Autonomous Region, starting from the eastern foot of Pamir Plateau in the west, to Lop Nur depression in the East, to the southern foot of Tianshan Mountains in the north, and to the northern foot of Kunlun Mountains in the south, roughly in the warm temperate zone of 37 ° to 42 ° n.

Climatic characteristics

Tarim Basin has a warm temperate climate, and the annual total solar radiation is 575-627 kJ / cm2. The annual sunshine hours are about 3000 hours in the north and less than 3000 hours in the south. The average annual temperature is 9-11 ℃, which is slightly higher in the South than in the north. The average temperature in January is 3.2 ℃ lower than that in Hetian and 2.4 ℃ lower than that in Kashgar. The average temperature in winter is lower than - 20 ℃ for only 1-2 days. The average temperature in July is 25-27 ℃. The active accumulated temperature above 10 ℃ is more than 4000 ℃, which is higher in the South than in the north; its duration is 200 days in the South and more than 190 days in the north; the interannual variation of accumulated temperature is large. The frost free period is more than 200 days, 200-210 days in the north and 220 days in the south. The annual average daily temperature range is 14-16 ℃, and the maximum daily temperature range is 25 ℃.

 

The main natural disasters are sandstorm and dry hot wind. There are gales above level 8 (wind speed is more than 17 m / s), and only Ruoqiang, Kashi and Korla have more than 20 days a year. However, the vegetation coverage at the edge of the basin is only 10%, and there is no vegetation in the center of the desert, and the wind speed is 5 meters per second. Therefore, the annual sandstorm weather in the South reaches 30-40 days. The sand dunes in the basin edge move southward seriously. ② Dry hot air. The most serious damage area is the eastern part of the basin, 10-20 days a year, and the frequency of occurrence is less in other areas of the basin.

 

Origin of water system

The water in the basin mainly comes from the westerly flow, which flows from Central Asia across the southern Tianshan River Valley (such as Kezi River Valley) or from Junggar basin across Tianshan Yakou (such as Hami and Urumqi) into the basin. There is little precipitation in the basin, which is 85mm in Wushi and 57mm in Aksu on the western margin, 63mm in Kuqa and 52mm in Korla on the northern margin, and 78mm in Atushi, 65mm in Kashi, 35mm in Hotan and 17mm in Ruoqiang on the southern margin from west to East. The basin itself can not form runoff, but the annual precipitation in Zhouwei mountainous area is 200-400mm, which can converge into rivers to reach the basin. The larger rivers are Yeerqiang, Kizil, Gaizi, Hotan, Keriya, Cheerchen (Qiemo) in the south, and Aksu, Tailan, Weigan, Kuche and Kaidu (Kongque) in the north. Under the natural condition, the above rivers can reach the Tarim River; under the condition of large amount of water diversion irrigation, only Aksu, Hetian and Yeerqiang rivers can reach the Tarim River. The annual runoff from the surrounding mountainous areas to the basin is about 37 billion cubic meters. The area to the east of 84 ° east longitude accounts for 45%, and the annual runoff is 18%. In addition, the water transported eastward by Tarim River is 3.2 billion cubic meters, accounting for 26%; the area to the West accounts for 55%, and the annual runoff is 82%, minus the part transported eastward, accounting for 74%.

 

Lop Nur in the eastern part of the basin is the terminal point of Tarim River, which used to be known as a migratory lake.

 

Tectonic evolution

Tarim Basin is a typical large superimposed composite basin with long-term evolution. It developed on the Archean early Mesoproterozoic crystalline basement and metamorphic folded basement, and the Sinian system constituted the first set of sedimentary cover of the basin. During the Sinian Quaternary, Tarim Basin experienced a complicated tectonic evolution.

 

Pre Sinian

Rocks and data with the oldest isotopic age in Tarim basin indicate that the eruption of alkaline basaltic magma from depleted mantle occurred in middle Archean and even early Archean, and the intrusion of magma formed the original continental core of Tarim Basin.

 

The early Proterozoic is an important period of rapid crustal growth in this region, and it is also a period when the continental core developed into a continental block. During the early Proterozoic Xingdi period, extensive and violent tectonic movement resulted in strong deformation of the rocks, and finally the Tarim block, Qaidam block and Junggar micro block converged into one.

After cratonization at the end of Mesoproterozoic Xingdi period, the aggregated Tarim landmasses split again, and the Tarim landmasses began to break up again

Chinese PinYin : Ta Li Mu Pen Di