Relief of the Darkhat Depression

The Darkhat Depression,one of the greatest depressions situated in the northern part of Mongolia, was the floor of an ancient lake in the Quaternary. At present, itis an interesting geomorphological research area where varied relief forms of different geneses occur. The absolute heights within thisdepression vary from 1,540 to 1,600 m. This paper deals with the principal characteristics of the Darkhat Depression and palaeogeographicaspects of its development. The paper is based on the analysis of the literary contributions and the present author's expeditionaryresearch on the depression relief during 2003-2006. In the field studies, the primary data on the relief and processes of the depressionrelief-formation (near 100 km of the total route was passed and forty points were described). Moreover, in the work, topographicmaps of scale 1:100,000, geological map of scale 1:500,000, the satellite Landsat-7 multichannel photos were used, the digitalrelief model was constructed according to SRTM (AsterDEM 30 m). The analysis of the depression relief was performed applying theprogram ArcGIS; the steepness, exposition, relative height of the territory, its horizontal ruggedness were established. The Darkhat Depression,stretching over 120 km from north to south and 40-50 km from west to east, is surrounded by high mountain ridges: Khardyl-Sardyk and Bayan-Ula, the Shishkhid Upland (Ulan-Taiga) and others. The absolute heights of the ridges vary from 2,000 to 4,000 m.The following genetic relief types are distinguished within the Darkhat Depression: glacial, limnic, eolian, alluvial-proluvial, alluvial,cryogenic, phytogenic and anthropogenic. In the Late Pleistocene, ridges surrounding the depression were exposed to glaciation of theglen character. Terminal moraines of the Late Pleistocene glaciation in the Darkhat Depression are well-defined in the outflow of therivers Khugein-Gol and Dzharain-Gol from mountains. The Darkhat Depression, as well as the majority of the mountain troughs in thesouth Siberia and Northern Mongolia, has gone through the "lacustrine" stage of development, which spanned the period from the Eopleistoceneto the end of the Late Pleistocene with interruptions. The reasons of the lakes formation include both the tectonic (warpingof depressions) and climatic factors (glaciations and interglacials). The complicated combination of them within the Darkhat Depressiongoverned the specific history of the development of the paleolacustrine reservoir in this region and also the formation of its modern relief.

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