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ice was more extensive in the Tian Shan during MIS 4 than during MIS 2, indicating
increasingly arid conditions in Central Asia during the last glacial cycle (Zech, 2012 ).
This conclusion accords with the evidence of increasing aridity in the Pamir inferred
by Zech et al. ( 2005 ) to account for the progressive reduction in late Pleistocene
glaciation over time.
An interesting new approach to checking glacial chronologies involves dating
boulders from very large landslides. Sanhueza-Pino et al. ( 2011 ) used this approach
in three formerly glaciated valleys in the Kyrgyz Tian Shan. The ages of the landslides
were obtained using 10 Be exposure dating methods, and care was taken to establish
that the landslides showed no signs of having been exposed to glacial erosion since
their accumulation. The ages obtained for the three landslides were 67-63 ka, 15-
11 ka and 8-6 ka, and they provide a minimum age for glacier advances in their
respective valleys. They also mark the maximum extent of the ice within those valleys.
The MIS 4 age for one of the glacial advances again confirmed that 'glaciations in
the Tien Shan are distinctly asynchronous with regard to glaciations in Europe and
North America' (op. cit., p. 303). They also concluded that previous estimates for
minimum equilibrium snow-line altitudes for the northern Tian Shan needed to be
revised upwards by about 400 m.
Gillespie et al. ( 2008 ) mapped three main late Pleistocene glacial advances in the
Darhad Basin in northern Mongolia and were able to date two of them reasonably
accurately. They used a combination of 14 C dating, cosmic ray exposure dating ( 10 Be)
and luminescence (IRSL) dating methods in order to obtain a reliable chronology of
times of maximum local ice advance and times of ice retreat. The two most recent
advances had ages of around 53-35 ka (MIS 3) and around 19-17 ka (MIS 2), syn-
chronous with advances of similar extent across northern Mongolia but different from
glacial advances in Siberia and western Central Asia. An older and more extensive
glaciation possibly dates back to MIS 6, but there was remarkably little difference
in the equilibrium line altitude (ELA) for all three glaciations. In contrast to the
Tian Shan, where enhanced aridity during the LGM confined glaciers to high eleva-
tions at that time, glaciers advanced to relatively low elevations during MIS 2 in the
DarhadBasin of northernMongolia, indicating less arid conditions in that region at that
time.
The Tibetan Plateau is the largest high plateau on earth, and covers an area of
2.6 million km 2 with a mean elevation of 4,600 m. Opinions about the extent of
the ice cover on the plateau during the LGM differ radically, with most workers
arguing for limited and spatially isolated glaciations (Owen, 2009 ), but Kuhle ( 2001 ;
2002 ) claimed that an ice cap covered most of the plateau. An independent test
of these conflicting scenarios is provided by a detailed ecological analysis of the
Alpine Steppes of the Tibetan highlands (Miehe et al., 2011 ). The high proportion
of endemic species in this biome argue for prolonged stability during the LGM, and
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