Qaidam Basin semi-desert
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The Qaidam, Tsaidam, or Chaidamu Basin is a
hyperarid An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. A number of aridity indices have been proposed (see below); these indicators serve to identify, locate or delimit regions that suffer from a ...
basin that occupies a large part of Haixi Prefecture in
Qinghai Province Qinghai (; alternately romanized as Tsinghai, Ch'inghai), also known as Kokonor, is a landlocked province in the northwest of the People's Republic of China. It is the fourth largest province of China by area and has the third smallest pop ...
, China. The basin covers an area of approximately , one-fourth of which is covered by
saline lake A salt lake or saline lake is a landlocked body of water that has a concentration of salt (chemistry), salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of ...
s and playas. Around one third of the basin, about , is desert.


Name

''Tshwa'i 'Dam'' is the Wylie
romanization Romanization or romanisation, in linguistics, is the conversion of text from a different writing system to the Roman (Latin) script, or a system for doing so. Methods of romanization include transliteration, for representing written text, a ...
of the Tibetan name , meaning "
Salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
Marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found a ...
"; the Tibetan Pinyin romanization of the same name is ''Caidam''. ''Qaidam'' is the GNC
romanization Romanization or romanisation, in linguistics, is the conversion of text from a different writing system to the Roman (Latin) script, or a system for doing so. Methods of romanization include transliteration, for representing written text, a ...
of its transcription into Mongolian; ''Tsaidam'' is a variant romanization of the same name. ''Chaidamu'' is the
pinyin Hanyu Pinyin (), often shortened to just pinyin, is the official romanization system for Standard Chinese, Standard Mandarin Chinese in China, and to some extent, in Singapore and Malaysia. It is often used to teach Mandarin, normally writte ...
romanization Romanization or romanisation, in linguistics, is the conversion of text from a different writing system to the Roman (Latin) script, or a system for doing so. Methods of romanization include transliteration, for representing written text, a ...
of its
transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...
into
Chinese characters Chinese characters () are logograms developed for the writing of Chinese. In addition, they have been adapted to write other East Asian languages, and remain a key component of the Japanese writing system where they are known as ''kanji ...
; the same name was formerly romanized as the for the
Chinese Postal Map The history of the postage stamps and postal history of China is complicated by the gradual decay of Imperial China and the years of civil war and Japanese occupation in the 1930s and 1940s. In modern times, postal delivery is handled by Ch ...
.


Geography

Orographically, the Qaidam Basin is a comparatively low area in the northeastern part of the Qinghai–Tibet Plateau.. With an elevation of around , Qaidam forms a kind of shelf between Tibet to the south (around ) and Gansu to the north (around ). A low water divide separates the Qaidam Basin proper from that of
Qinghai Lake Qinghai Lake or Ch'inghai Lake, also known by other names, is the largest lake in China. Located in an endorheic basin in Qinghai Province, to which it gave its name, Qinghai Lake is classified as an alkaline salt lake. The lake has fluctuate ...
to the east. Despite this lower elevation, Qaidam is still high enough that its mean annual temperature is despite lying on the same latitude as
Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , largest_city = capital , relig ...
,
Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders ...
, and
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...
in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
. The crescent-shaped basin covers an area of approximately . Its substrate is broadly divided into three blocks: the Mangya Depression, a northern fault zone, and the
Sanhu Depression The Qarhan Playa or also misleadingly described as , is a playa in the Golmud and Dulan counties of Haixi Prefecture, Qinghai, China. Formerly a single unitary lake, it is now an expansive salt flat divided into four greater sections ( Dabu ...
. Qaidam is an intermontane basin, surrounded on all sides by mountain ranges. In the south, the Kunlun Mountains separate it from the higher central section of the
Tibetan Plateau The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the ...
. In the north, a number of smaller ridges like the Shulenanshan separate it from another higher plateau, which usually referenced by the name of its northern escarpment, the Qilian or Nanshan. In the northwest, the
Altyn-Tagh Altyn-Tagh (also Altun Mountains, Altun Shan; , Pinyin: ''A'erjin Shan'', Wade–Giles: ''A-erh-chin Shan;'' Uyghur'':ئالتۇن تاغ'') is a mountain range in Northwestern China that separates the Eastern Tarim Basin from the Tibetan P ...
separates it from the Kumtagh Desert of southeastern
Xinjiang Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwest ...
. Because of this position, Qaidam forms an
endorheic basin An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...
accumulating lakes with no outlet to the sea. The area is among the most arid non-polar locations on earth, with some places reporting an
aridity index An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. A number of aridity indices have been proposed (see below); these indicators serve to identify, locate or delimit regions that suffer from a ...
of 0.008–0.04. Across the entire basin, the mean annual rainfall is but the mean annual evaporation is . Because of the low rainfall, these lakes have become saline or dried up completely. Presently, there are four main playas in the basin: Qarhan in the southeast and (from north to south) Kunteyi, Chahanshilatu, and Dalangtan in the northwest. These playas and a few other
saline lake A salt lake or saline lake is a landlocked body of water that has a concentration of salt (chemistry), salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of ...
s occupy over one-fourth of the basin, with the sediments deposited since the
Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
as deep as 10 to 14 km (6–9mi) in places despite tectonic activity having repeatedly shifted the center of the region's sedimentation. The seasonal nature and commercial exploitation of some of the lakes makes an exact count problematic: one count reckoned there were 27 lakes in the basin,. another reckoned 43 with a total area of . The aridity, salinity, wide diurnal and seasonal temperature swings, and relatively high ultraviolet radiation has led to Qaidam being studied by the
China Geological Survey The China Geological Survey (CGS) () is a government-owned, not-for-profit, Chinese organization researching China's mineral resources. It is a public institution managed by the State Council’s ministries and commissions responsible for geologi ...
as a
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
analogue for use in testing spectroscopy and equipment for China's 2020 Mars rover program.


Geological history

Qaidam was part of the
North China Craton The North China Craton is a continental crustal block with one of Earth's most complete and complex records of igneous, sedimentary and metamorphic processes. It is located in northeast China, Inner Mongolia, the Yellow Sea, and North Korea. Th ...
from at least 1 billion years ago, before breaking off million years ago at the end of the
Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is prec ...
. It was an island in a shallow sea until uplift beginning around 400 Ma finally rejoined it to the mainland by 200Ma. Three-dimensional modeling shows that the present basin has been squeezed to an irregular diamond shape since the beginning of the Cenozoic, with the
Indian Plate The Indian Plate (or India Plate) is a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian Plate broke away from the other fragments of Gondwana , began ...
beginning to impact the ancient Tibetan shoreline somewhere between 55–35Ma. At first, Qaidam was at a far lower elevation. Pollen found in
core sample A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The ...
s shows that the Oligocene (34–23Ma) was relatively humid. A great lake slowly formed in the western basin, which two major tectonic movements raised and cut off from its original sources of sediment. At its greatest extent during the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
(23–5Ma), this lake spread at the present elevation contour over . and was among the largest lakes in the world. Nutrient-rich inflows contributed to
plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
blooms, which supported an ecosystem that built up reserves of organic carbon. The Tibetan plateau's uplift, however, eventually cut it off from the warm and humid
Indian monsoon The Monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year fro ...
. It went from a
forest steppe A forest steppe is a temperate-climate ecotone and habitat type composed of grassland interspersed with areas of woodland or forest. Locations Forest steppe primarily occurs in a belt of forest steppes across northern Eurasia from the eastern ...
to a desert. By 12Ma, the climate had dried enough to break Qaidam's single lake into separate basins, which frequently became saline. During the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Kunteyi but, during the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
(after 2.5Ma), tectonic activity shifted the basin's tributaries and floor, moving the focus of sedimentation from the Dalangtan to Qarhan area. During this time, the record's glacial intervals suggest a low-temperature climate and its
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...
yardangs attest to strong winds. From 770,000 and 30,000 years ago, the enormous lake which filled much of the southeastern basin alternated nine times between being a fresh- and
saltwater Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...
lake. Pollen studies suggest the bed of
Dabusun Lake Dabusun or alternately known as is a lake beside the town Qarhan, just north of Golmud in the Haixi Prefecture of Qinghai Province in northwestern China. Fed by the main course of the Golmud River, it is the largest present-day lake in the Q ...
in the Qarhan Playanearly the lowest point of the basinwas elevated about within the last 500,000 years. At around 30 kya, this greatat the time, freshwaterlake spread over at least with a surface above the present levels of its successors. At the same time, a river from the "Kunlun" paleolake to its south was enriching the Sanhu region with enormous reserves of
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...
derived from
hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by c ...
s near Mount Buka Daban which now feed into the
Narin Gol River The Narin Gol River (), sometimes spelled Narin-Gol River, also known as Narenguole River, or Nalenggele River, is an inland river in Qinghai Province of China, located in the Qaidam Basin, with a length of 435 kilometres, a catchment area of ...
that flows into East Taijinar Lake. Around 30 kya, the lake in the Kunluns dried up and the Qarhan was cut off from sufficient inflows of fresh water. It became saline again, beginning to precipitate salts about 25,000 years ago.. The basin's continuing formation and evolution is controlled by the
Altyn Tagh fault The Altyn Tagh Fault (ATF) is a 2,000 km long, active, sinistral (left lateral) strike-slip fault that forms the northwestern boundary of the Tibetan Plateau with the Tarim Basin. It is one of the major sinistral strike-slip structures that t ...
constituting the northern basin boundary.


Resources

The basin's large mineral deposits caused a great deal of investment interest from 2005. Qarhan Playa, a salt flat including about ten of the lakes, contains over 50 billion metric tons (55 billion short tons) of
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
. Beneath the salt, Qaidam is one of China's nine most important petroliferous basins and its largest center of onshore production. The Qinghai Oilfield, exploited since 1954, includes the Lenghu, Gasikule, Yuejin-2, and Huatugou oil fields and the Sebei-1, Sebei-2, and Tainan gas fields. All together, it has proven reserves of 347.65 million metric tons (more than 2 billion barrels) of
petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
and 306.6 billion cubic meters (10.83 trillion cubic feet) of
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
. Annual production capacity is about 2 million metric tons of petroleum and 8.5 billion cubic meters of natural gas. A pipeline connects the Huatugou field with the major
refinery A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value. Types of refineries Different types of refineries ...
at
Golmud Golmud, also known by various other romanizations, is a county-level city in the Haixi Mongol and Tibetan Autonomous Prefecture of Qinghai Province, China. It is now the second-largest city in Qinghai and the third largest in the Tibetan Pl ...
, and the Sebei gas fields are connected to
Xining Xining (; ), alternatively known as Sining, is the capital of Qinghai province in western China and the largest city on the Tibetan Plateau. The city was a commercial hub along the Northern Silk Road's Hexi Corridor for over 2000 years, and w ...
, Lanzhou, and
Yinchuan Yinchuan (, ; ) is the capital of the Ningxia Hui Autonomous Region, China, and was the capital of the Tangut-led Western Xia dynasty. It has an area of and a total population of 2,859,074 according to the 2020 Chinese census, and its buil ...
. Qaidam has reserves of asbestos,
borax Borax is a salt ( ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular for ...
,
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywal ...
, and several
metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s, with the greatest reserves of
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...
,
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
,
potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...
, and
sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
of anywhere in China.


Transportation

The Xining-Golmud rail line (the first stage of the Qinghai–Tibet Railway), which crossed the eastern part of the Qaidam Basin in the early 1980s, is an essential transportation link for accessing the region's mineral resources. As of 2012, additional rail lines are under construction. The construction of the Golmud–Dunhuang Railway started in October 2012; it is expected to be completed within 5 years.格尔木至敦煌铁路开工
, ''Renmin Tielu Bao'', 2012-10-20
In the early 2012, Zangge Potash Co Ltd started the construction of a 25-km private railway from the Qarhan station on the Qinghai–Tibet Railway (near the eponymous salt lake) to their facilities nearby. As of the late 2013, preliminary planning is conducted for the Golmud-Korla Railway, which will stretch along the entire western part of the Qaidam Basin as well.库尔勒—格尔木铁路项目预可研报告获批
(Korla-Golmud Railway project preliminary feasibility study report approved), 中华铁道网, 2013-09-30


References


Citations


Bibliography

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External links


"Qaidam"
in the ''
Columbia Encyclopedia The ''Columbia Encyclopedia'' is a one-volume encyclopedia produced by Columbia University Press and, in the last edition, sold by the Gale Group. First published in 1935, and continuing its relationship with Columbia University, the encyclope ...
''
Qaidam Basin Photos
from
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...
{{coord, 37, 16, N, 94, 27, E, region:CN_type:landmark, display=title Landforms of Qinghai Drainage basins of China