Glacial Geomorphology of Mt . Asralt Khairkhan and Mt . Baga Khentii Saridag in Khentii Mountain Range , Northeastern Mongolia

This study provides a map of glacial geomorphology of Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag in Khentii Mountain Range in northeastern Mongolia. In the Khentii Mountain Range, only two types of glacial landforms including glacial cirques and terminal moraines are observed for the paleoglacial reconstructions of Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag, and are mapped based on a mapping from 30 m resolution ASTER DEM and Landsat 8 satellite imagery. Spatial distribution of the glacial landforms indicates that the Khentii Mountain Range has experienced valley glaciations with small ice caps centered on the high mountains. The glacial cirques mark numerous glacial erosional landforms, while the terminal moraines indicate glacial advances and depositional landforms at outlets of valleys. Outer limits of these glacial landforms show their maximum glaciation of 10.0 km and 0.7 km for Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag, respectively. This study demonstrates that spatial analysis of the glacial landforms is crucial for reviewing the paleoglacier extent. The map of the glacial geomorphology will be a key for further detailed studies in paleoglaciology and paleoclimate of the mountain range.


Introduction
Reconstructing paleoglaciers is in efforts critical to understanding climate change in the past, glacier behavior and sensitivity to climate change, i.e., reconstructing the paleo record of the paleoglacier changes contributes to under- In Mongolia, evidence for paleoglaciers has been widely found in the Altai, Khangai, Khuvsgul and Khentii Mountain Ranges (Figure 1) because the four mountain ranges were glaciated in Pleistocene [1], three to four times in the Altai, twice to three times in the Khangai and Khuvsgul, and one in the Khentii [2].
The extent of paleoglaciation in Mongolia is the greatest in the north and west compared to the south and east, and this trend is also observed for modern glaciers [1] [2].The dominant style of glaciations recorded in the landforms and deposits of Mongolia is valley glaciations [1] [2].The Khentii Mountain Range differs as only one mountain range where the modern glaciers do not take still place today, compared with other three mountain ranges, namely the Altai, Khangai and Khuvsgul in Mongolia (Figure 1).There has been a lack of work reconstructing long-term glacier fluctuations.The purpose of this paper is to provide a reconstruction of paleoglaciers for Khentii Mountain Range in northeastern Mongolia.
There is still poor scientific information about the spatial and temporal paleoglaciers including their extents and chronology in Khentii Mountain Range, compared with other Altai, Khangai and Khuvsgul Mountain Ranges, even in the World Glacier Inventory or in the database of the US National Snow and Ice Data Center.In other words, no any detailed studies except for the studies by Tsegmid [3] and Jigj [2] have been completed in the Khentii, where the paleoglacier remains have been abundant [2].

Site Description
The Khentii Mountain Range extends southwest-northeast trends from its most southwestern tip, the Mt.Bogd, to the Russian border in the northeast of Mongolia (Figure 1, Figure 2), with a mean elevation of 1600 m a.s.l (extending from 2800 m a.s.l. of Mt.Asralt Khairkhan in the highest part to 600 m a.s.l. of the estuary of River Yeruu in the lowest part).In other words, the Khentii Mountain Range extends from the northeastern corner of Mongolia towards the southwest, where it becomes the most southern end of the Siberian wetland, merging into the prairie of central Mongolia (Figure 1).The Khentii Mountain Range is surrounded by the valleys of the River Onon in the east, River Kherlen in the southeast, of River Tuul in the southwest, of River Orkhon in the west and Rivers of Kharaa and Yeruu in the northwest (Figure 2).The Khentii Mountain Range is predominantly composed of early Paleozoic and Mesozoic granites, and consists of dome-shaped tops, peaks with steep gorges and cliffs, and valleys with gentle slopes formed by the Cenozoic glaciations [1] [15].The climate of this range is characterized by large annual temperature variations [16].The large Rivers Onon, Kherlen, Terelj, Tuul, Kharaa, Yeruu drain the Khentii Mountain Range (Figure 2) into Atlantic and Pacific Ocean Basins [16].The International Journal of Geosciences Khentii Mountain Range is known for its high diversity of vegetation types going from Siberian taiga forests to Mongolian steppe vegetation [17].
Mt. Asralt Khairkhan, one of our study areas, is located in the center of the Khentii Mountain Range (Figure 2).Mt.Asralt Khairkhan is the peak of the Khentii Mountain Range and is situated at an elevation of 2800 m a.s.l.According to a meteorological station in Terelj village (Figure 3), locating 61 km south of the Mt.Asralt Khairkhan and at an elevation of 1530 m a.s.l, the annual mean precipitation is 225.3 mm (ranging from 1.4 mm in January to 76.2 mm in July), and the annual mean air temperature is -3.3˚C (ranging from -21.6˚C in January to 13.0˚C in July) [18].Rivers Khongor, Asralt and Khurkhree drain Mt.
Mt. Baga Khentii Saridag, another one of our study areas, is located at an elevation of 2534 m a.s.l. on the center of the Khentii Mountain Range (Figure 2).

Method
In

Results and Discussion
Glacial landforms in Khentii Mountain Range are compiled on glacial geomorphological map (Figure 4, Figure 6).The Khentii Mountain Range has experienced to glaciations once in the Quaternary period [1]

Glacial Landforms
On the maps, glacial landforms were identified as glacial cirques and terminal

Glacial Cirques
Glacial cirques are formed in a bowl-shaped depression on the side near mountains [25].Although Heyman et al. [20] and Blomdin et al. [4] included the cirques in the category of glacial valleys, they have been identified in individual category in this study.It has been predicted as their identifications as that if a glacial cirque advances far enough, it may become a valley glacier.On the contrary, it is a cirque glacier because a valley glacier retreats enough that it is within cirques [26].Snow may be situated on the leeward slope of a mountain, where it is sheltered from wind and rock fall from above slopes also plays an important role in sheltering the snow and ice from sunlight [26].In Mt.Asralt Khairkhan and Mt.Baga Khentii Saridag, glacial cirques clearly observed are identified in Landsat imagery and AGDEM (Figure 4

Terminal Moraines
Terminal or end moraines are ridges of unconsolidated debris deposited at the snout or end of the glacier, i.e., if the material pushed in front of the glacier is left, this material is called a terminal/end moraine.They usually reflect the shape of the glacier's terminus and the more debris accumulates in the end moraine [25].
Glaciers act much like a conveyor belt as carrying debris from the top of the glacier to the bottom where end moraines form.Size and shape of end moraine are determined by whether the glacier is advancing, receding or at equilibrium.Sizes of end moraine vary from smaller ridges with areas less than a couple of meters wide and tens of meters long to larger complexes more than 100 km 2 areas [4].The end moraines mark the maximum advance of the glacier.In Mt.Asralt Khairkhan, clearly exposed end moraines are most easily identified in Landsat imagery and AGDEM (Figure 4

Paleoglacier Extent
For spatial reconstruction on paleoglacier extent in the Mt.Asralt Khairkhan and Mt.Baga Khentii Saridag in Khentii Mountain Range, the aerial extent of paleoglaciation based on the distribution of glacial landforms described above (see Section 4.1) is estimated.The maximum glacier extents were delineated in the GIS environment using the margins of the glacial cirques and terminal moraines (Figure 4(d), Figure 6(d)).This method enables a straightforward delineation of the maximum glacier extent in formerly glaciated mountain regions using the glacial landforms [4].This reconstruction based on remote sensing represents the minimum extent of maximum glaciation, i.e., this paleoglaciological footprint yields a useful estimate of paleoglacier coverage based on the distribution of glacial landforms and allows for a comparison with the modern glacier extent (e.g.[4] [27]).Consistency and accuracy of the glacial geomorphological mapping have been strictly strengthened by previous mapping procedures [4]

Conclusion
Paleoglacier extents of Mt.Asralt Khairkhan and Mt.Baga Khentii Saridag in Khentii Mountain Range in northeastern Mongolia have been spatially reconstructed as 10.0 km 2 and 0.7 km 2 , respectively.With the reconstruction with glacial landforms, large terminal moraines formed by glacial advances are mainly

A
. Orkhonselenge, M. Uuganzaya DOI: 10.4236/ijg.2018.96019309 International Journal of Geosciences standing how glaciers vary with climate change, and provides opportunities to reconstruct paleoclimates.Mountain glaciers respond sensitively to local-to-regional patterns of climate change which are driven by global-scale processes.Paleoglacier evolution in high mountains is the key parameter for a reliable prediction of future glacier change.Determinations of paleoglacier extent during glacial maximums and paleoclimatic reconstructions are still a challenge.

Figure 1 .
Figure 1.Location of mountain ranges in Mongolia.Red box denotes the location of Khentii Mountain Range, study area presented in detail in Figure 2.

Figure 2 .
Figure 2. Topography of Khentii Mountain Range.Red box denotes the location of study area presented in Figure 3.
[20] [21][22] [23][24].In this study, the reconstructed paleoglacier extents in Mt.Asralt Khairkhan (Figure4(d)) and Mt.Baga Khentii Saridag (Figure 6(d)) are calculated from the Randolph Glacier Inventory V3.2.The maximum glaciation areas are reconstructed by 10.0 km 2 and 0.7 km 2 for Mt.Asralt Khairkhan and Mt.Baga Khentii Saridag, respectively (Figure 4(d), Figure 6(d)).Results in this study reconstruct spatial extents on the maximum paleoglaciations of the Mt.Asralt Khairkhan and Mt.Baga Khentii Saridag in Khentii Mountain Range.Furthermore, the spatial analyses contribute to have been predicted that paleoglaciers near 48˚N -49˚N in northeastern Mongolia may have retreated with faster rate for these individual mountains depending on geographical position in southern latitudes and vulnerability of the glaciers to solar