Surface exposure dating reveals MIS-3 glacial maximum in the Khangai Mountains of Mongolia

Abstract

This study presents results from geomorphological mapping and cosmogenic radionuclide dating (10Be) of moraine sequences at Otgon Tenger (3905 m), the highest peak in the Khangai Mountains (central Mongolia). Our findings indicate that glaciers reached their last maximum extent between 40 and 35 ka during Marine Oxygen Isotope Stage (MIS) 3. Large ice advances also occurred during MIS-2 (at ~ 23 and 17–16 ka), but these advances did not exceed the limits reached during MIS-3. The results indicate that climatic conditions during MIS-3, characterized by a cool-wet climate with a greater-than-today input from winter precipitation, generated the most favorable setting for glaciation in the study region. Yet, glacial accumulation also responded positively to the far colder and drier conditions of MIS-2, and again during the last glacial–interglacial transition when precipitation levels increased. Viewed in context of other Pleistocene glacial records from High Asia, the pattern of glaciation in central Mongolia shares some features with records from southern Central Asia and NE-Tibet (i.e. ice maxima during interstadial wet phases), while other features of the Mongolian record (i.e. major ice expansion during the MIS-2 insolation minimum) are more in tune with glacier responses known from Siberia and western Central Asia.

Oxygen isotope composition of diatoms from sediments of Lake Kotokel (Buryatia)

“…In the ~36-32 kyr BP interval, δ 18 O diatom in the Kotokel archive (Fig. 3) decreases gradually and matches the cooling trend evident in the paleoclimate records of Mongolia (Rother et al, 2014), North China (Wen et al, 2008), and Yakutia (Müller et al, 2010). The Kotokel δ 18 O signal agrees with the general temperature trend reconstructed from Greenland ice cores: the maximums 29.0‰ at ~35.8 kyr BP and 27.9‰ at 33.4 kyr BP correlate with the time of the Dansgaard-Oeschger events (DO7 and DO6 in Fig.…”

“…Most likely, the climate at ~40-38 kyr BP was not as cold and dry as at ~24.7-23 kyr BP, and/or evaporation from the lake surface was less intense. Wet winters at ~43-34 kyr BP were inferred for Central Mongolia (Rother et al, 2014), while the Kotokel deposits from that interval bear more abundant Alnus fruticosa growing in wet but not swampy areas with thick seasonal snow compared to the values for thẽ 24.7-23.0 kyr BP interval (Bezrukova et al, 2010). In the ~36-32 kyr BP interval, δ 18 O diatom in the Kotokel archive (Fig.…”

Extensive glaciation in Transbaikalia, Siberia, at the Last Glacial Maximum

“…We note that a similar pattern has recently been reported from the Khangai Mountains of Mongolia (Fig. 1), where an ice re-advance at 17-16 ka reached within 1-2 km of the local LGM limits (Rother et al, 2014). In addition, evidence of minor still-stands or re advances of glaciers higher in the mountains exists in the form of recessional moraines in some mountain valleys (Fig.…”

“…Glaciallakes j 9 0rka ice7 sh e e t e xte nt after G lac ial Lake V itim Komatsu et al (2007a) Kazakhstan Lehmkuhl et al (2004) Zhao et al (2013 K h a n g a i Rother et al (2014) …”

“…A large ice cap that existed in the central SayanTuva Upland in OIS-6 and -4 was apparently absent during OIS-3 and -2 when the character of glaciation changed to branching valley glaciers (Komatsu et al, 2007b;Arzhannikov et al, 2012). In the Khangai Mountains of west-central Mongolia, the most extensive preserved moraine ridges date to OIS-3 with OIS-2 ice limits reaching nearly the same extents (Rother et al, 2014). An even stronger trend of successively diminishing glacial advances is documented for the Verkhoyansk Mountains, a large mountain group east of the Aldan and Lena rivers in eastern Siberia (Fig.…”