Geoscience Reference
In-Depth Information
Figure 9.4. Map showing the distribution of loess in China. (After Williams et al.,
1998 .)
meant fewer incursions of high-intensity, potentially erosive summer rain. By analogy
with the present, the winter rains were most likely prolonged and gentle, enabling the
thin loess deposits to be washed off the slopes and down to the valley bottoms by
overland flow (Williams et al., 2001 ).
A major environmental change took place close to the onset of the Last Glacial
Maximum (21
2 ka), after which episodic floods deposited the laminated unit
(Haberlah et al., 2010a ; Haberlah et al., 2010b ). These findings show that the LGM
climate was not uniformly cold and arid, and in fact experienced significant decadal
scale variability. Abrupt incision after 15 ka denoted a return to a high-intensity
summer rainfall regime and the end of the wetlands (Williams et al., 2001 ; Williams
et al., 2009b ).
±
9.6 The Loess Plateau of China
By far the best terrestrial record of wind-blown dust accumulation is that preserved in
the Loess Plateau of China ( Figure 9.4 ), which covers an area of about 440,000 km 2 and
ismantled by loess that reaches up to 350m in thickness but is usually only about 100m
(Liu, 1985 ;Liu, 1987 ;Liu, 1991 ; Kukla, 1987 ). Wind-blown dust began to accumulate
in China early in the late Miocene, some 8 million years ago (8 Ma) (An and Porter,
1997 ) and possibly even as early as 22-24 Ma ago (Guo et al., 2002 ; Sun et al., 2010 ).
Search WWH ::




Custom Search