Eolian environmental changes in the Northern Mongolian Plateau during the past ∼ 35,000 yr
Abstract This study focuses on an eolian section (Shaamar section) in the Northern Mongolian Plateau and compares the eolian sequences in the Northern Mongolian Plateau with those along the southern boundary of the Gobi Deserts to better understand the dynamics of the Gobi deserts during the past ∼ 35,000 14C yr BP. Only a weak Entisol-like paleosol was formed around 29,000 14C yr BP in the exposed MIS 3 portion at the Shaamar section, whereas an eolian–colluvium–paleosol sequence at nearby Bureghkanga section exhibits three paleosols formed around 29,000 14C yr BP, 31,000 14C yr BP, 34,000 14C yr BP. Loess–paleosol sequences in the western Siberian Lowland exhibit four paleosols formed from > 40,000 to 25,000 14C yr BP (i.e., MIS 3). During MIS 2 two Mollisol-like paleosols were formed from ∼ 25,000 to ∼ 21,000 14C yr BP and from ∼ 16,000 to ∼ 13,000 14C yr BP and one Entisol-like paleosol was formed around 9500 14C yr BP at the Shaamar section. The MIS 2 was characterized primarily by silt deposition, except for the interval between ∼ 21,000 and ∼ 16,000 14C yr BP that was dominated by sand deposition. The Holocene began with the Mollisol-like paleosol formation (from ∼ 8600 to ∼ 7000 14C yr BP). The mid-Holocene (∼ 7000 to ∼ 3000 14C yr BP) was marked by a relatively poor vegetation cover and the late Holocene (since ∼ 3000 14C yr BP) by the densest vegetation cover of the entire Holocene. In summary, the maximal extent of hyperarid and arid areas (Gobi deserts and Gobi-like) occurred twice: (1) from ∼ 21,000 to ∼ 16,000 14C yr BP and from ∼ 13,000 to ∼ 8600 14C yr BP when the dominant eolian deposition conditions extended from 56° N to 33° N or even larger. The extent of hyperarid and arid areas retreated to the area between 38° N and 48° N or even much smaller several times during MIS 3 and during the early Holocene. Considering the uncertainties of dates, it seems that the Holocene bioclimatic conditions might have changed more or less synchronously between the north and the south and that the bioclimatic conditions varied more frequently in the north than in the south during MIS 3. Two Mollisol-like paleosols (IIc: ∼ 13,000 to ∼ 16,000 14C yr BP; and IIIa: ∼ 21,000 to ∼ 25,000 14C yr BP) were well developed during MIS 2 in the north, but no corresponding major paleosols were discovered in the south, suggesting that the climate did not change synchronously during MIS 2. The climates during the stadial–interstadial MIS 3–2 transition (∼ 25,000 to ∼ 21,000 14C yr BP) and during the last glacial maximum-deglacial transition (∼ 16,000 to ∼ 13,000 14C yr BP) were much more humid in the north than in the south.