| Qaidam Basin | |
|---|---|
| Tsaidam Basin or Chaidamu Basin | |
 Qaidam Basin | |
  Qaidam Basin  Qaidam Basin | |
| Location | Haixi Prefecture,Qinghai Province |
| Coordinates | 37°16′N94°27′E / 37.267°N 94.450°E /37.267; 94.450 |
| Type | Hyperarid basin |
| Part of | Qinghai–Tibet Plateau |
| Basin countries | China |
| Surface area | 120,000 km2 (46,000 sq mi) |
| Surface elevation | 3,000 m (10,000 ft) |
| Location | |
 Interactive map of Qaidam Basin | |
| Qaidam Basin | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Chinese name | |||||||||
| Traditional Chinese | 柴達木盆地 | ||||||||
| Simplified Chinese | 柴达木盆地 | ||||||||
| Postal | Zaidam Swamp | ||||||||
| Literal meaning | Qaidam Lowlands | ||||||||
| |||||||||
| Tibetan name | |||||||||
| Tibetan | ཚྭའི་འདམ་ | ||||||||
| |||||||||
| Mongolian name | |||||||||
| Mongolian Cyrillic | Цайдам | ||||||||
| |||||||||
| Qaidam Desert | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Traditional Chinese | 柴達木盆地沙漠 | ||||||||
| Simplified Chinese | 柴达木盆地沙漠 | ||||||||
| Literal meaning | Qaidam Lowland Desert | ||||||||
| |||||||||
TheQaidam,Tsaidam, orChaidamu Basin is ahyperaridbasin that occupies a large part ofHaixi Prefecture inQinghai Province,China. The basin covers an area of approximately 120,000 km2 (46,000 sq mi), one-fourth of which is covered bysaline lakes andplayas. Around one third of the basin, about 35,000 km2 (14,000 sq mi), is desert.
Tshwa'i 'Dam is theWylieromanization of theTibetan nameཚྭའི་འདམ་, meaning "SaltMarsh"; theTibetan Pinyin romanization of the same name isCaidam.Qaidam is theGNCromanization of its transcription intoMongolian;Tsaidam[1] is a variant romanization of the same name.Chaidamu is thepinyinromanization of itstranscription intoChinese characters; the same name was formerly romanized as theZaidam Swamp for theChinese Postal Map.[2]
Orographically, the Qaidam Basin is a comparatively low area in the northeastern part of theQinghai–Tibet Plateau.[3] With an elevation of around 3,000 m (10,000 ft), Qaidam forms a kind of shelf between Tibet to the south (around 4,300 m or 14,000 ft) andGansu to the north (around 1,100 m or 3,500 ft). A low water divide separates the Qaidam Basin proper from that ofQinghai Lake to the east. Despite this lower elevation, Qaidam is still high enough that its mean annual temperature is 2–4 °C (36–39 °F)[4] despite lying onthe same latitude asAlgeria,Greece, andVirginia in theUnited States.
The crescent-shaped basin[5] covers an area of approximately 120,000 km2 (46,000 sq mi).[6][7] Its substrate is broadly divided into three blocks: the Mangya Depression, a northern fault zone, and theSanhu Depression.[8] Qaidam is an intermontane basin, surrounded on all sides by mountain ranges.[3] In the south, theKunlun Mountains separate it from the higher central section of theTibetan Plateau. 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, theQilian or Nanshan. In the northwest, theAltyn-Tagh separates it from theKumtagh Desert of southeasternXinjiang.
Because of this position, Qaidam forms anendorheic basin accumulating lakes with no outlet to the sea. The area is among the most arid non-polar locations on Earth, with some places reporting anaridity index of 0.008–0.04.[10] Across the entire basin, the mean annual rainfall is 26 mm (1 in) but the mean annual evaporation is 3,000–3,200 mm (120–130 in).[4] Because of the low rainfall, these lakes have becomesaline or dried up completely. Presently, there are four mainplayas in the basin:Qarhan in the southeast and (from north to south)Kunteyi,Chahanshilatu, andDalangtan in the northwest.[10] These playas and a few othersaline lakes occupy over one-fourth of the basin,[6] with the sediments deposited since theJurassic as deep as 10[7] to 14 km[4] (6–9 mi) in places despite tectonic activity having repeatedly shifted the center of the region's sedimentation.[10] 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,[11] another reckoned 43 with a total area of 16,509 km2 (6,374 sq mi).[12]
The aridity, salinity, wide diurnal and seasonal temperature swings, and relatively high ultraviolet radiation has led to Qaidam being studied by theChina Geological Survey as aMars analogue[13] for use in testingspectroscopy and equipment for China's2020 Mars rover program.[14]
Qaidam was part of theNorth China Craton from at least 1 billion years ago, before breaking offc. 560 million years ago at the end of theNeoproterozoic.[5] It was an island in a shallow sea until uplift beginning around 400 Ma finally rejoined it to the mainland by 200 Ma.[5]
Three-dimensional modeling shows that the present basin has been squeezed to an irregular diamond shape since the beginning of theCenozoic,[15] with theIndian Plate beginning to impact the ancientTibetan shoreline somewhere between 55[16]–35 Ma.[17] At first, Qaidam was at a far lower elevation.Pollen found incore samples shows that theOligocene (34–23 Ma) was relatively humid.[18] A great lake slowly formed in the western basin, which two major tectonic movements raised and cut off from its original sources of sediment.[18] At its greatest extent during theMiocene (23–5 Ma), this lake spread at the present 2,800 m (9,200 ft) elevation contour[6] over 300 km (190 mi)[4] and was among thelargest lakes in the world. Nutrient-rich inflows contributed toplankton blooms, which supported an ecosystem that built up reserves of organic carbon.[19] The Tibetan plateau's uplift, however, eventually cut it off from the warm and humidIndian monsoon.[19] It went from aforest steppe to adesert.[5] By 12 Ma, the climate had dried enough to break Qaidam's single lake into separate basins, which frequently became saline.[4] During thePliocene (5–2.5 Ma), the focus of most sedimentation was at what is nowKunteyi but, during thePleistocene (after 2.5 Ma), tectonic activity shifted the basin's tributaries and floor, moving the focus of sedimentation from theDalangtan toQarhan area.[10] During this time, the record'sglacial intervals suggest a low-temperature climate[18] and itssandstoneyardangs attest to strong winds.[19]
From 770,000 and 30,000 years ago, the enormous lake which filled much of the southeastern basin alternated nine times between being afresh- andsaltwater lake.[20]Pollen studies suggest the bed ofDabusun Lake in the Qarhan Playa—nearly the lowest point of the basin—was elevated about 700 m (2,300 ft) within the last 500,000 years.[21] At around 30kya, this great—at the time, freshwater—lake spread over at least 25,000 km2 (9,700 sq mi) with a surface 50–60 m (160–200 ft) above the present levels of its successors.[22] At the same time, a river from the "Kunlun" paleolake to its south was enriching the Sanhu region with enormous reserves oflithium[23] derived fromhot springs nearMount Buka Daban which now feed into theNarin Gol River[24] that flows intoEast Taijinar Lake.[25]
Around 30kya, 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.[22] The basin's continuing formation and evolution is controlled by theAltyn Tagh fault constituting the northern basin boundary.[15]
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) ofsalt.[9]
Beneath the salt, Qaidam is one of China's nine most importantpetroliferous basins[26] 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.[27] All together, it has proven reserves of 347.65 million metric tons (more than 2 billionbarrels) ofpetroleum and 306.6 billion cubic meters (10.83 trillion cubic feet) ofnatural gas.[28] 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 a majorrefinery atGolmud, and the Sebei gas fields are connected toXining,Lanzhou, andYinchuan.[29]
Qaidam has reserves ofasbestos,borax,gypsum, and severalmetals, with the greatest reserves oflithium,magnesium,potassium, andsodium found anywhere in China.
The Xining-Golmud rail line (the first stage of theQinghai–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. Additional railroads spanning the basin include theGolmud–Dunhuang Railway completed in December 2019[30] and a 25 km private railway constructed by Zangge Mining Co., Ltd.[31]
TheNational Development and Reform Commission began conducting preliminary planning for theGolmud-Korla Railway in September 2013, which would stretch across the western portion of the Qaidam Basin.[32] Construction began in November 2014 and concluded in 2020.[33]
