Russian and American scientists have determined the age of the Aral sea
Russian and American scientists have traced the history of the Aral sea.
Russian and American scientists have traced the history of the Aral sea. As described in an article in Quarternary Science Review and in the press release of the Siberian branch of the Russian Academy of Sciences, the lake was formed approximately 17.6 thousand years ago, at the end of the last glacial maximum. The main sources of water, apparently, was water from the glaciers of the Terskey-Alatau, Tien Shan and Pamir.
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The Aral sea was a salty lake located on the border of Kazakhstan and Uzbekistan. It fell to the two major rivers Amudarya and Syrdarya. Until 1950-ies it was considered the fourth largest lake on the planet. In the 1930-ies in Central Asia, began the construction of irrigation canals, which diverted water from the Amu Darya and Syr Darya.
In the 1960-ies, the water level in the Aral sea began to decline until it’s separated into two isolated lakes of the North and South seas. By 2014, South sea 90 percent dry. But in the past the water level in the Aral sea periodically fell also significantly. In particular, over the last two thousand years, the lake became shallow twice, and for a long time. To understand what influenced the shallowing of the lake, but human activities or changing environmental conditions, researchers are studying the history of the Aral sea, particularly over the last two thousand years.
Russian and American researchers under the leadership of Sergey Krivonogova and Yaroslav Kuzmin Institute of Geology and Mineralogy SB RAS Sobolev studied deposits in the area of the former island of Barsa-Kelmes island. Field work was conducted in 2009, two years after the lake in this place is dry. Scientists drilled a well at a depth of 14.9 metres and selected at different depths in samples of lake sediments.
It turned out that the sediments at depths of up to 10 meters belong to the time of existence of the Aral sea.
The researchers analyzed the size of the particles in the sediments and their composition, and collected paleontological data (sediments they found the shells of mollusks, ostracods, and foraminifera), and conducted radiocarbon analysis of organic remains.
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The results of the analysis of sediments and paleontological specimens, as well as using radiocarbon Dating, the authors determined the age of the lake. Apparently, it was formed 17,6 thousand years ago, at the end of the last glacial maximum.
Presumably, the main sources were water from the glaciers of the Tien Shan, Pamir and Terskey-Alatau, which began to melt during the next warming. They were brought to the Aral sea, the Syr Darya and Amu Darya. Approximately two thousand years after the formation of the lake, it began to get less river water and its salinity has increased. This is evidenced by the increased number of shells of ostracods Cyprideis torosa crustacea, which maintained the concentration of salts in water at 70 percent higher than other ostracods. The peak salinity of the lake is between 14.5 and 14 thousand years ago, and for the next thousand years the waters of the Aral sea again became salted.