A 450-ka long record of glaciation in Northern Mongolia based on studies at Lake Khubsugul: high-resolution reflection seismic data and grain-size variations in cored sediments

We use high-resolution reflection seismic data and detailed grain-size analysis of a drill core (KDP-01) from Lake Khubsugul (northern Mongolia) to provide an improved reconstruction of the glacial history of the area for the last 450 ka. Grain-size analysis of suspended sediment load in modern rivers draining into the lake and of moraine material from the northern part of the catchment shows that the silt fraction is transported to the central part of the lake mainly by river suspension, whereas the clay fraction is mainly transported by glacial meltwater during deglaciation. The changes in of the clay/silt ratio in Lake Khubsugul sediments correlates well with the standard global paleoclimate records: low clay/silt ratios indicate warm climates, while a high clay/silt ratio reflects glacial erosion and cold climates. Pulses of clay input into the lake occur at the final stages of glacial periods (i.e., glacial maxima and subsequent onsets of deglaciation). The periodicity in glacial clay input in Lake Khubsugul is in tune with global periods of deglaciation, but there are differences in the intensity of the deglacial events for MIS-12 and MIS-2. These differences are attributed to specific conditions in regional distribution of moisture during glaciation, glacial ice volumes, and solar insolation intensity at the onset of deglaciation. Deglaciation of the Khubsugul glaciers occurred in response to an increase in summer solar insolation above a threshold value of 490 W/m 2 . Two types of deglaciation can be distinguished: (1) slow melting during several tens of 1,000 years during weak increases in summer insolation, and (2) short and fast melting during several thousands of years in response to strong increases in summer insolation. The maximum ice volume in the area of Lake Khubsugul during the past 450 ka occurred during the period of 373–350 ka BP (MIS 11a-10) and was caused by high levels of moisture in the region, whereas the MIS-2 and MIS-12 glacial periods were characterized by minima in ice volume, due to the strong aridity in the region.