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Vitim Plateau is a
plateau In geology and physical geography, a plateau (; ; ), also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. Often one or more sides ...
in Buryatia and
Zabaykalsky Krai Zabaykalsky Krai ( rus, Забайкальский край, r=Zabaikal'skii krai, p=zəbɐjˈkalʲskʲɪj kraj, lit. " Transbaikal krai"; bua, Yбэр Байгалай хизаар, Uber Baigalai Xizaar) is a federal subject of Russia (a krai ...
, Russia. The plateau is sparsely populated, the main settlements are Romanovka and Bagdarin. An area of the plateau is an ancient volcanic field with a number of cinder cones and volcanoes, the last of which was active about 810,000 years before present. The P436 regional road connecting
Ulan-Ude Ulan-Ude (; bua, Улаан-Үдэ, , ; russian: Улан-Удэ, p=ʊˈlan ʊˈdɛ; mn, Улаан-Үд, , ) is the capital city of the Republic of Buryatia, Russia, located about southeast of Lake Baikal on the Uda River at its confluence wi ...
and Chita passes through Romanovka across the plateau.


Geography

The Vitim Plateau lies along the headwaters of the
Vitim River The Vitim (russian: Витим; evn, Витым, ; sah, Виитим, ; Buryat and mn, Витим, ''Vitim'') is a major tributary of the Lena. Its source is east of Lake Baikal, at the confluence of rivers Vitimkan from the west and China ...
, a tributary of the
Lena Lena or LENA may refer to: Places * Léna Department, a department of Houet Province in Burkina Faso * Lena, Manitoba, an unincorporated community located in Killarney-Turtle Mountain municipality in Manitoba, Canada * Lena, Norway, a village in ...
between the
Southern Muya Range The Southern Muya Range (russian: Южно-Муйский хребе́т, translit=Yuzhno-Muyskiy khrebet) is a mountain range in Buryatia and Zabaykalsky Krai, Russia, part of the Stanovoy Highlands. The highest point of the range is 3,067 m high ...
to the north, the
Ikat Range Ikat Range () is a mountain range in Buryatia, Russia. It runs in a parallel direction to the Baikal Rift. The range is named after two small rivers sharing the name "Ikat" which have their sources in opposite slopes of the range one is a tribu ...
to the west, the Yablonoi Mountains to the south, and in the east with the lower reaches of the Kalakan River to the right bank of the lower reaches of the Karenga River (both Vitim tributaries) and the latter's right tributary, the Bugarikta.Энциклопедия Забайкалья - Vitim Plateau
/ref> The Vitim River begins at the confluence of the China and Vitimkan rivers on the plateau and makes a wide bend around the volcanic zone before flowing northwards. Rivers Tsipa, Tsipikan and Amalat cut across the plateau and the Baunt Depression is located in the northwestern corner. The plateau has a surface area of . In it smooth, low mountain ranges such as the Bolshoy Khapton, with average heights between and , alternate with
intermontane basin Intermontane is a physiographic adjective formed from the prefix " inter-" (''signifying among, between, amid, during, within, mutual, reciprocal'') and the adjective "montane" (inhabiting, or growing in mountainous regions, especially cool, moi ...
s. The Vitim Plateau is covered by
larch Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains furt ...
taiga Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces ...
and
forest steppe A forest steppe is a temperate-climate ecotone and habitat type composed of grassland interspersed with areas of woodland or forest. Locations Forest steppe primarily occurs in a belt of forest steppes across northern Eurasia from the easter ...
, as well as thickets of shrubby
birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains 3 ...
es, meadows, and swampy areas in the river basins.Витимское плоскогорье
- ''
Great Soviet Encyclopedia The ''Great Soviet Encyclopedia'' (GSE; ) is one of the largest Russian-language encyclopedias, published in the Soviet Union from 1926 to 1990. After 2002, the encyclopedia's data was partially included into the later ''Bolshaya rossiyskaya e ...
:''
n 30 vols. N, or n, is the fourteenth letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''en'' (pronounced ), plural ''ens''. History ...
/ Ch. ed.
A.M. Prokhorov Alexander Mikhailovich Prokhorov (born Alexander Michael Prochoroff, russian: Алекса́ндр Миха́йлович Про́хоров; 11 July 1916 – 8 January 2002) was an Australian-born Soviet-Russian physicist known ...
. - 3rd ed. 1969-1978.
The volcanic field in its southwestern part has an area of .Chemical Variations in Peridotite Xenoliths from Vitim, Siberia: Inferences for REE and Hf Behaviour in the Garnet-Facies Upper Mantle
/ref> There are a number of lakes, such as
Baunt Baunt (russian: Баунт; bxr, Баунт нуур, ''Baunt nuur'') is the name of a body of fresh water in the Bauntovsky District, Buryatia, Russia. The village of Kurort Baunt, where there are some hot springs, is located on the southwes ...
, Busani,
Kapylyushi Kapylyushi (russian: Капылюши) or Kapylyushy is a body of fresh water in the Bauntovsky District, Buryatia, Russia. The name originated in an Evenki word. The lake is located in the northwestern corner of the Vitim Plateau, near the ...
,
Telemba Telemba (russian: Телемба; bua, Тэлэмбэ, ''Telembe'') is a rural locality (a selo) and the administrative centre of Kondisnkoye Rural Settlement, Yeravninsky District, Republic of Buryatia, Russia. The population was 1,256 as of 2 ...
, Arakhley, Bolshoy and
Maly Yeravna Maly Yeravna (russian: Малое Еравное; bxr, Бага Ярууна) is a fresh water body in the Yeravninsky District, Buryatia, Russia. There are two inhabited places by the lake, Tuldun in the northwestern shore and Shiringa in the ...
. The area is marked by
permafrost Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surfac ...
.


Volcanism

About five circular groups of volcanoes occur in the field, which is in turn subdivided into two major provinces. Both central volcanoes and
cinder cone A cinder cone (or scoria cone) is a steep conical hill A conical hill (also cone or conical mountain) is a landform with a distinctly conical shape. It is usually isolated or rises above other surrounding foothills, and is often of volcanic ...
s occur in the volcanic field, with the largest volcanoes reaching heights of and diameters of .


Geology

Since the
Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but ...
and especially the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Asian Plate has been rifting apart in the Baikal Rift where the Siberian craton and a
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...
assembly of
terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its ow ...
s (ancient microcontinents) form a contact zone. This rifting process is associated with volcanism in the neighbourhood of the rift zone, and this volcanism has produced about of volcanic rock in several volcanic fields, including the Udokan Plateau and the Vitim Plateau which are the largest volcanic fields of the Baikal Rift. The reasons for the rifting process aren't well known. One theory holds that the collision between
India India, officially the Republic of India ( Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the ...
and
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an ...
and other tectonic processes triggered the pull-apart in the Baikal Rift. Another one postulates the existence of thermal anomalies such as a
mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hot ...
beneath the Baikal Rift as the driving force of the rifting. The
basement A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the Furnace (house heating), furnace, ...
beneath the Baikal Rift is
granitic A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quart ...
and up to thick. It may be of
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...
age. Other rocks in the region are sediments close to river valleys and
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...
volcanic rocks.


Composition

Vitim Plateau volcanic rocks are mainly alkaline to subalkaline
basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...
s,
nephelinite Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite). If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite is dark in color and may rese ...
s and melanephelinites, with
phenocryst 300px, Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter 2.3 cm) for scale. A phenocryst is an early forming, relati ...
phases containing
clinopyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...
,
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...
and
plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...
. Younger rocks have a tendency towards alkaline compositions. The melts that give rise to Vitim Plateau
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...
s appear to originate in the
lithospheric A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years or ...
mantle, starting from
garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different ...
pyroxenite Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite, diopside, hypersthene, bronzite or enstatite. Pyroxenites are classified into clinopyroxenites, orthopyroxenites, and the websterit ...
and
peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high prop ...
and leaving
phlogopite Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica. Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg3AlSi3O ...
as residual phase when starting from pyroxenite. Petrology indicates that a complex magma production process takes place beneath the Vitim Plateau, including remelting and crystallization.


Eruption history

Two volcanic phases have been identified in the Vitim Plateau. The first took place during the
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...
; potassium-argon dating has yielded ages of 10.65 - 6.6 million years ago. The second occurred during the
Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...
with the most recent eruption dated 810,000 years ago. Later volcanic activity was concentrated in river valleys and cones on the surface of the plateau.


References


Sources

* {{refend Landforms of Buryatia Landforms of Zabaykalsky Krai Pleistocene volcanoes Volcanoes of Russia Plateaus of Russia South Siberian Mountains