Dabusun or Dabuxun Lake, alternately known as Dabasun Nor, is a lake beside the townQarhan,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 Qarhan Playa. Like the other lakes of the surrounding Qaidam Basin,it is extremely saline,with 307–338 grams of salt per liter of water (2.5 lb/gallon).
Dabusun[1][2] or Dabasun Nor[3][4] is a romanization of its Mongolian name,which means simply "Salt Lake".[5] In Mongolian,the name is sometimes designated "eastern",to distinguish it from West Dabusun Lake.[5] It is sometimes misspelled Dabsun[6] or Dabsan.[7][8] It was formerly known as the Dalai Dabasun,[9] meaning "Sea" or "Ocean of Salt".
Dabusun lies in the Dabusun subbasin in the central Qarhan Playa.[10] It is one of the many saltwater lakes in the endorheicQaidam Basin,[6] bound by the Qilian Mountains to the north,the Altun to the west,and the Kunlun to the south.[11] Lying at an elevation of 2,675m (8,776ft) above sea level,it has a mean annual temperature of 0.1°C (32.2°F) despite lying on the same latitude as Greece,Algeria,and Virginia in the United States.[7] Dabasun is the largest present lake in the Qarhan Playa.[6] It is fed by the main course of the Golmud River from the south and,to a lesser extent,by mineral springs[2] from the north.[12] In Qaidam's hyperarid climate,there is generally only 28–40mm (1–2in) of annual rainfall but about 3,000mm (120in) of annual evaporation.[7] Its area is thus variable by season and year,[13] usually 184–334km2 (71–129sqmi) but increasing in the wetter winter and spring and decreasing through the summer and fall. The lake is elongated,stretching from the northwest to the southeast. Its length is usually about 30km (19mi) east to west,and its width is usually about 4–7.5km (2–5mi) north to south. The maximum depth is 1.72m (5ft 8in),and the average depth varies from 0.5 to 1.02m (1ft 8in to 3ft 4in).
Geology
Although the northern springs contribute much less volume,their waters carry far greater concentrations of solutes and are important to the chemical composition of the lake.[14] Below,the alternating beds of mud and halite extend at least 40m (130ft) in some places.[6] In addition to common salt,it also has an abundance of carnallite[1] (potassiummagnesiumchloride) in an area of 2km ×35km (1mi ×22mi) and magnesium sulfate. The known beds are exposed at the surface or buried by 3–4m (10–13ft) of sedimentation.[6]
Paleoclimatologists believe that between 770,000 and 30,000 years ago Dabusun formed part of a much larger Qarhan Lake,which alternated nine times between being a fresh- and saltwater lake.[15]Pollen studies suggest that the area of the lake bed which now underlies Dabusun was raised around 700m (2,300ft) in just the last 500,000 years.[16] Tectonic activity also varied sedimentation in the lake by shifting its tributaries and basins,although it remained in the Qarhan Playa during this period.[17] At around 30,000 years ago,this great freshwater lake spread over at least 25,000km2 (9,700sqmi) with a surface 50–60m (160–200ft) above the present levels of its successors. It was cut off and became saline again around 30,000 years ago and began precipitating salts about 25,000 years ago.[18] It has been shrinking in size by evaporation for most of that time,[9] although it was only about 42km (26mi) in circumference in the mid-19th century,when it was visited by the Polono-Russian explorer Przhevalsky.[9][a]
Until the recent commercial exploitation of the salts and other minerals,the district has remained largely unpopulated,as the salt deposits made it difficult for the nomads of northwestern China to use the area for their herds.[9] The area's potassium deposits were accidentally discovered in 1957[20] and exploratory wells found the Yanhu Gas Field north of the lake the next year.[21]
"The Monthly Record", The Geographical Journal, 31 (4): 438–451, 1908, JSTOR1777861 .
Casas, Enrique; etal. (1992), "Carnallite Mineralization in the Nonmarine, Qaidam Basin, China: Evidence for the Early Diagenetic Origin of Potash Evaporites", SEPM Journal of Sedimentary Research, 62 (5): 881–898, doi:10.1306/D4267A05-2B26-11D7-8648000102C1865D .
Dexin, J. (2000), "Quaternary Palynofloras and Paleoclimate of the Qaidam Basin, Qinghai Province, Northwestern China", Palynology, 24: 95–112, doi:10.2113/0240095 .
Qi, Huang; etal. (1997), "Stable isotopes distribution in core Ck6 and variations of paleoclimate over Qarhan Lake region in Qaidam Basin, China", Chinese Journal of Oceanology and Limnology, 15 (3): 271–278, Bibcode:1997ChJOL..15..271H, doi:10.1007/BF02850884, S2CID129491899 .
Yang, Hui; etal. (2012), "Integrated geophysical studies on the distribution of Quaternary biogenic gases in the Qaidam Basin, NW China", Petroleum Exploration and Development, 39 (1): 33–42, doi:10.1016/S1876-3804(12)60012-3.
Zhang Baozhen; etal. (1990), "Hydrogen and Oxygen Stable Isotope Analyses of Fluid Inclusions in Halite in Charhan Salt Lake with Geochemical Implications", Acta Sedimentologica Sinica, 8 (1): 3–17.
Zhou, S. L.; etal. (2016), "Spatial-temporal variations and their dynamics of the saline lakes in the Qaidam Basin over the past 40 years", IOP Conference Series: Earth and Environmental Science, 46 (1) 012043, Bibcode:2016E&ES...46a2043Z, doi:10.1088/1755-1315/46/1/012043.
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