Ustyurt plateau

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On the Ustyurt plateau in Uzbekistan

The Ustyurt Plateau or Ust-Urt Plateau is an extensive, desert to steppe-like plateau in Central Asia. It belongs to the Turan lowlands and lies between the Caspian Depression and the Western Aral Sea on the territory of Uzbekistan , Turkmenistan and Kazakhstan . The plateau is about 180,000 km² and stands out from its surroundings with a 60 to 150 m high steep step. Its altitude is on average 160 to 200 m, the highest point is 370  m . According to M. Goeje (1875), the name Ust-Urt means "highlands".

Geologically, it is a table land made up of a large plate of marl and limestone , in the depressions of which salt lakes have formed. Crude oil and natural gas occur below the plateau . Four areas are distinguished according to surface form and vegetation :

  • wide, completely flat clay regions
  • the large salt region on the Aral Sea
  • some hilly sandy areas in the southeast
  • the marl region in the east.

In terms of plant geography and geology, there is a relationship to the southern foothills of the Ural Mountains , which continue as a chain of hills of the Mugodscharen about 500 km to the northwest of the Northern Aral Sea .

The Mangyschlak peninsula, which protrudes far to the west into the Caspisee , is usually counted as part of the Ust-Urt, but has mountain axes running across it. On the northern edge of the plateau in the Mangistau Mountains (Gora Bessoki) it reaches an altitude of 556 meters.

The Ust-Urt is very poor in running waters. The Tschegan flows in the northwest, but soon disappears in the desert. The only river Arass-Kuil on the east side turns to the west, but in summer it mostly dries up.

geology

Alexander von Humboldt carried out his first geological research around 1830. He put geognostisch and orographic a connection to the Urals found u. a. in the almost parallel alignment of the central axes . Geologically, however, the Ust-Urt is younger (see below) and is largely composed of horizontal tertiary layers .

The northwestern edge of the plateau shows an uninterrupted series of deep cuts, the terraces of which are often covered by large debris from a conglomerate of mussels. They were therefore interpreted as traces of an earlier coast over 100 years ago.

Today's geology sees a connection with the Sarmatian Sea , which after the Oligocene stretched from the Mediterranean via the Black and Caspian Seas to the Central Asian Depression . Fluvial sediments from the adjacent mountains settled on its banks and unfolded at about the same time as the Alps . The Sarmatian sediments of the former sea consist of clay minerals , sand, sandstone , conglomerates and limestone . Later crustal movements displaced the sea into a small part of the southern Turan while the north was raised.

In the Pliocene (3–6 million years ago) the sea came back again, but no longer reached its earlier dimensions and created the border between the Ust-Urt plateau and the Karakum desert and the Ungus (a drainless valley in the middle of the desert). In addition to many small depressions, the tectonic movements also created the Aral Basin , which corresponds to part of the sunken base.

With the exception of the slightly raised central part, the table land is structured quite uniformly and consists of horizontally lying marls and limestone of the middle and upper Sarmatian , underneath are red sands and clays, underneath these are iron-shed sands and conglomerates of Aquitaine . In the southern part, the erosion edge of the table runs from the Karabugas Gulf to the southeast to the Karakum Desert and makes this underlay visible, as do some gullies and troughs on the plateau itself.

At its northern edge, the Miocene sub-base is also exposed: all stratification sequences from the Oligocene, Eocene and Paleocene are present, as well as the Upper Cretaceous at a greater distance . They are almost horizontal - with a slight slope to the south - and are unfolded , which emphasizes the Ust-Urt as a separate block. Only between the Oligocene and Miocene does a weak discordance indicate tectonic movements of this period.

Flora and fauna

The desert-like Ustyurt plateau is home to various - sometimes rarer - animal species such as the saiga antelopes , caracals and steppe wild sheep (Trans-Caspian Urial ). Various reptile and rodent species also live on the plateau. The flat, undulating soil structure also offers various birds of prey a hunting ground, such as the Turkmen eagle owl , the sucker falcon or the black vulture . The Ustyurt Plateau was once home to Asiatic cheetahs ( Acinonyx jubatus raddei , only lives in Iran and is acutely threatened with extinction) and various subspecies of the goitered gazelle . Due to the climatic changes caused by the drainage of water from Amu Darja and Syr Darja for the irrigation of the cotton monocultures in Uzbekistan, the flora and fauna of the Ustyurt plateau has also changed. The exact population of the individual animal species is largely unknown, as the plateau is remote and there are no roads or railways. The Kaplankyr Nature Reserve in Turkmenistan is an important protected area on the southern edge of the plateau . A part of the Ustyurt plateau in Kazakhstan is also a state nature reserve.

Web links

Coordinates: 43 ° 17 ′ 0 ″  N , 55 ° 33 ′ 0 ″  E