Qaidam Basin

Jurassic 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 the

2020 Mars rover program.^[14]

Geological history

Wade-Giles romanization

)

Qaidam was part of the

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 the

glacial intervals suggest a low-temperature climate^[18] and its sandstone yardangs 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 a

saltwater lake.^[20] Pollen studies suggest the bed of Dabusun 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 30 kya, 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 of lithium^[23] derived from hot springs near Mount Buka Daban which now feed into the Narin Gol River^[24] that flows into East Taijinar Lake.^[25]

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.^[22] The basin's continuing formation and evolution is controlled by the Altyn Tagh fault constituting the northern basin boundary.^[15]

Resources

Sanhu Depression in SE Qaidam (2014). The two Taijinar lakes lie to the northwest and the lakes of the Qarhan Playa to the southeast. (ESA

)

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.^[9]

Beneath the salt, Qaidam is one of China's nine most important petroliferous 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 billion barrels) of petroleum and 306.6 billion cubic meters (10.83 trillion cubic feet) of natural 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 the major refinery at Golmud, and the Sebei gas fields are connected to Xining, Lanzhou, and Yinchuan.^[29]

Qaidam has reserves of asbestos, borax, gypsum, and several metals, with the greatest reserves of lithium, magnesium, potassium, and sodium found anywhere in China.

Transportation

The Xining-Golmud rail line (the first stage of the

Golmud–Dunhuang Railway started in October 2012; it is expected to be completed within 5 years.^[30] 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.^[31]

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.^[32]