Eolian environmental changes in the Northern Mongolian Plateau during the past ∼ 35,000 yr

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 similar to 35,000 C-14 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 C-14 yr BP, 31,000 C-14 yr BP, 34,000 C-14 yr BP. Loess-paleosol sequences in the western Siberian Lowland exhibit four palcosols formed from > 40,000 to 25,000 C-14 yr BP (i.e., MIS 3). During MIS 2 two Mollisol-like paleosols were formed from similar to 25,000 to similar to 21,000 C-14 yr BP and from similar to 16,000 to similar to 13,000 C-14 yr BP and one Entisol-like paleosol was formed around 9500 C-14 yr BP at the Shaamar section. The MIS 2 was characterized primarily by silt deposition, except for the interval between similar to 21,000 and similar to 16,000 C-14 yr BP that was dominated by sand deposition. The Holocene began with the Mollisol-like paleosol formation (from similar to 8600 to similar to 7000 C-14 yr BP). The mid-Holocene (similar to 7000 to similar to 3000 C-14 yr BP) was marked by a relatively poor vegetation cover and the late Holocene (since similar to 3000 C-14 yr BP) by the densest vegetation cover of the entire Holocene. In summary, the maximal extent of hyperarid and and areas (Gobi deserts and Gobi-like) occurred twice: (1) from similar to 21,000 to similar to 16,000 C-14 yr BP and from similar to 13,000 to similar to 8600 C-14 yr BP when the dominant eolian deposition conditions extended from 56 degrees N to 33 degrees N or even larger. The extent of hyperarid and arid areas retreated to the area between 38 degrees N and 48 degrees 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: similar to 13,000 to similar to 16, 000 14C yr BP; and IIIa: similar to 21,000 to similar to 25,000 C-14 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 (similar to 25,000 to similar to 21,000 C-14 yr BP) and during the last glacial maximum-deglacial transition (similar to 16,000 to similar to 13,000 C-14 yr BP) were much more humid in the north than in the south. (c) 2006 Elsevier B.V. All rights reserved.