THE KOREAN JOURNAL OF QUATERNARY RESEARCH Vol. 21, No. 2, p. 19-22 (December. 2007)

Structure‐Geomorphological Districts of

Khukhuudei Ulambadrakh Faculty of Geosciences, National University of Mongolia

1. Introduction and method geomorphological districts in territory of Mongolia have a few, but have been observed the lack. Structure geomorphological districts of any territory Principle to making of boundary of morphostructural distinguish evident that based on its geological structure, district hasn’t in use, but, in most cases, based on figures depth structure and paleogeography. of altitude in relief, making morphometric analysis. Structure geomorphology or morphostructural study Boundaries of morphostructural districts are encountered that is to make the accurate link of mentioned features with faults, although district is divided to blocks. Each based on and defined as “morphostructure is geological blocks have feature to geological and tectonic structure, and tectonic structure which formed endogenous process depth structure and morphology. and re‐changed exogenous process “by I.P.Gerasimov This paper is not aimed at entering a description and Yu.V.Mescheryakov, Russian scientists, in 1965. of physical geography to each blocks, and determined Scientific papers that touched on dividing in to structure‐ a just morphostructural description.

Fig. 1. Schematic map for geomorphological districts of Mongolia (by N.A.Florensov and S.S.Korjuev, 1982)

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2. Structure‐geomorphological districts Mongolian Altay macroblock. Mongolian Altay is mountain range located in western part of Mongolia Morphostructurally, Mongolia is divided into several and separated by Pre‐Altay deep‐seated fault in the east different blocks including 2 megablocks and 13 macro- from Basin of Great Lakes and deep‐seated fault blocks related from region to local for terminology. in the south from Baruun khuuray basin. It belongs to A. Mountainous country province megablock: epiplatformic orogeny that formed on folded, then pene- Macroblocks: 1. Mongolian Altay plained basement of Paleozoic age. Its main morphostruc- 2. Khubsugul tural elements are occurred in present relief as changed 3. Khangay by exogenic process neotectonic structure. 4. Khentey The basement of Mongolian Altay is divided into 5. Gobi‐Altay and Pre‐Altay Gobi tectonic blocks with strike of north‐west, and cutted by 6. Orkhon‐Selenge basin deep‐seated faults. B. Plain country province megablock: Morphostructural feature for Mongolian Altay is Macroblocks: 7. Basin of Great Lakes (Lake Valley) composite result of fracturing and folding defomation 8. Baruun Khuuray basin at the Pre‐Cenozoic basement. 9. Sulinkheer (South East Mongolia) By a terrane subdivision of plate tectonics, Mongolian 10. Khoit Kherulen (North East Mongolia) Altay is forearc/backarc basin. 11. Central Gobi peneplain The thickness of earth’s crust beneath Mongolian 12. Dornod‐Mandal Altay is 42‐60km. 13. Atas Bogd‐Gurvansaikhan

Fig. 2. Schematic map of structure‐geomorphological districts (Kh.Ulambadrakh, 2007)

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Khubsugul macroblock. Khubsugul macroblock is horst (Boroo), and small dome (Modot, Janchivlan) located northern part of Mongolia and separated by morphostructures. Ereendavaa block of it is more interest- Kangay deep‐seated fault in the south and Agardag fault ing morphostructure and here is alternated horst and in the west. Khubsgul morphostructure is also composite graben structure. result of fracturing and folding deformation related thickly Tectonically, Khentey macroblock consists of turbi- with development of south west side of Baigal rift zone. dite basin (Baga Khentey, South East, Periphery blocks) Main morphostructure for Khubsugul is influenced forearc/back arc basin (North West block) and cratonal Khubsugul, Darkhad and Busingol rift basins. Furthermore, block (Ereendavaa). East Khubsugul, West Khubsugul and Shishged arched The thickness of earth’s crust beneath is 45km. uplifths are to composite structure. The bigger faults which formed in Caledonian time and directed to meridian are Pre‐Altay Gobi and Gobi Altay macroblock. Generally, controlled the development of them. this is east continuation of Mongolian Altay, but differ- Khubsugul macroblock is cratonal block and island ence of it is strike that directing west to east and northwest arc for tectonic classification. to south east. The thickness of earth’s crust in Khubsugul is 45‐ Pre‐Altay Gobi and Gobi Altay are the similar to 55km and is the thinner of 5‐6km in Darkhad and some morphostructural features, history of relief develop- Khubsugul rifts. ment, although considered together. Macroblock’s “face” is blocking, folding‐blocking mountain and transverse Khangay macroblock. Khangay is located in west basin. and central part of Mongolia. Khangay uplift or dome The example of transverse morphostructure is Arts is composite structure that distinguished to the bigger Bogd. Gobi Altay mountain range is piedestal mountain and smaller blocks. Khangay dome is subdivided into which is first stage of regenerated mountain development. several blocks including Bulnay, Tarvagatay, North‐west This macroblock shows island arc and its basin. Khangay, East Khangay and South Khangay. It not oc- The thickness of earth’s crust is 45‐50km. curred horst and graben structure, but is dominantly ring structure of variuos size and origin. From ring structure, Orkhon‐Selenge macroblock. This is located in cen- Chuluut gol, Shireet nuur, Upper Orkhon and Upper tral‐north part of Mongolia. By a morphostructural fea- Ongiin gol are the evident and they related to granitic tures, it subdivided into Selenge‐Jid, Orkhon–Selenge intrusive of Late Paleozoic and Mesozoic ages and basalt and Tuul–Orkhon blocks. This macroblock has weak of Cenozoic. South limb of Khangay dome is very high differentiated dome blocking uplift (Khangay, Buteel, seismic activity. In central part of Khangay, the thickest Buren), blocking uplift (, Khoshoot), horst earth’s crust of Mongolia is 55‐60km. (Nomgon, uul, Khalzan uul, Tuleet uul), graben Tectonically, is cratonal block with superimposed and graben–like basin (Jargalant, Mogod, , Lun). basin of Late Paleozoic‐Lower Mesozoic. Moreover, well kept volcanic (Togoo, Uranmandal, Khuis mandal) and active faults (Orkhon, Selenge, Mogod, Khentey macroblock. Khentey macroblock is uplift Bayangol). or dome dominated ring structure of various size, kind The thickness of earth’s crust is 42.5 (north east and age, horst and dome intrusive. Ereendavaa, Baga side of macroblock)‐44km. Khentey, South East, North West and Periphery blocks distinguished within Khentey macroblock. These blocks Basin of Great Lakes (Lakes Valley) macroblock. are with eroded, strong fractured ring structure, moreover, This macroblock is located in western part of Mongolia,

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directing to submeridian. (East Gobi tectonic depression). Basin of Great Lakes is superimposed, composite Dornod–Mandal Ovoo and Khoit Kherulen macro- basin system and formed in place of previous Mesozoic blocks have ring structure from remains of volcanoes. basin. It is divided into Uvs nuur, Central, Khar Us‐ These macroblocks are not distinguished to detailed Zeergent and Shargiin Gobi blocks. blocks, but with many faults. The thickness of earth’s Within these blocks, not occured specific main struc- crust for them is 42.5 (Sulinkheer, Khoit Kherulen) to ture and occurs few faults (Bayan nuur, Darvi) 45km (Dornod‐Mandal Ovoo, Atas Bogd–Gurvan sai- Morphostructural feature of this macroblocks that consist- khan). ing of alluvial, proluvial, alluvial–proluvial and aeolian plain should occur and explain the information based on geophysical data to each blocks. References The thickness of earth’s crust is 42– 44km. Tectonically, this is island are. Badarch G., Cunningham D., Windley B. (2002) A new terrane subdivision for Mongolia: implications for Baruun Khuuray basin macroblock. Baruun Khuuray the Phanerozoic crustal growth of Central Asia. basin macroblock is located in south west of Mongolia Journal of Asian Earth sciences 21:87‐110 and separated by Bulgan fault in the north west and Byamba J. (2001) Physical geography districts of Alag nuur fault in the east. Mongolia. Problems of geology : 279‐301 (in mon- Structurally, it is relative stable block of earth’s golian ) crust that consisted of Middle‐Paleozoic rocks. Chichagov V.P. (1975) Morphostructural feature of re- It is seen as structural wedge with separated by generated mountains of Khangay, Khentey and faults in all side. The smaller faults in macroblock are Khingan. Structure geomorphology of mountainous as horst and graben to composite structure. Weak occured country: 241‐250 (in russian) this structure at surface is seen as plain, either hilly Geomorphology of People′s Republic of Mongolia territory. (1982), editors‐in‐chief: Florensov N.A and BaruunKhuuray is island are for tectonic district. Korjuev S.S, Moscow, pp.256 (in russian) Earth’s crust is 45km. Morphostructural study (1985), editor‐in‐chief: Vasilkovsky N.V., Moscow, pp. 209 (in russian) Central Gobi peneplain macroblock. Morphostructurally, Mordvinova V.V., Zorin Yu. A., Gao Sh., Davis P. (1995) relative weak studied. Intensive stage of peneplainisation Depth structure of lithosphere along Baikal‐ is explained that Mesozoic to Oligocene. Mongolian transect. Depth structure and geo- The main “role“ in peneplain is completed various dynamics of Mongolia‐Sybir region: 64‐73 (in rus- faults. Grabens formed along faults (Ikh Bogd–Ondor sian) shil, Dundgobi, Khoshuu Khiid). Munkhu Z. (1979) Structure‐geomorphology of East Sulinkheer (South East Mongolia), Khoit Kherulen Khangay, pp. 64 (in mongolian ) (North East Mongolia), Dornod–Mandal Ovoo and Atas Schmidt G,A (2006) Main types of relief in Mongolia. Bogd–Gurvan Saikhan macroblocks are dominantly plain Physical geography of Mongolia:17‐39 (in russian) relief, and, weak occurred morphostructure. Zorin Yu.A., Turutanov E.Kh., Kozhevnikov V.M., Sulinkheer is the one of main structure of platform Novoselova M.R., Balk T.V. The geophysical data. development in Mongolia. Its basement is occured at Complex geophysical and seismological inves- surface and is to 700‐800m depth in north west side tigation in Mongolia: 7‐13 (in russian)

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