Mu Us Desert
The Mu Us desert of Inner Mongolia
(Fig. 1) lies in the
semi arid zone of northern China and has a mean annual temperature 10 degrees C and gets less than 250 mm of rainfall per year.
Fig 1. Semi-arid Mu Us desert, with vegetation and large sand dunes.
Apart from being the homeland of Genghis Kahn, the
desert has been hypothesised as a source of dust to the Chinese Loess Plateau
and lies immediately to the north of the vast loess accumulations. The Mu Us has been argued as
a major loess source based upon grain-size (Yang and Ding,
2008) and geochemical analysis (Sun, 2002) of sediments. Hypotheses over the
origin of the Mu Us desert sands have centred on reworking of underlying
fluvial and aeolian sands of the Quaternary, themselves reworked from
underlying Cretaceous aeolian sandstone (Sun, 2000; 2002). Currently, many dunes in the desert are covered by grassland vegetation but recent reactivation of dunes in the Mu
Us appears to be reworking Quaternary sands (Sun, 2000) and interfingered loess
and sand deposits on the edge of the Mu Us and bordering on the Loess Plateau
testify to the desert’s past expansion and contraction (Fig. 2).
Fig 2. Northern edge of the loess plateau near Jingbian showing sand deposits interfingering with loess layers.
Our recent paper (Stevens et al., 2013) based on heavy minerals
and zircon dating strongly suggests that the desert has a complex source
signature, with local sources dominating in the east and sand derived from the
Tibetan plateau coming into the west (Fig 3).
Fig 3. Stevens et al. (2013). Map of Mu Us with zircon U-Pb age spectra for samples. Lower map shows location of Mu Us and Chinese Loess Plateau. U-Pb age Kernel density Estimators (KDEs) and number of analyses are shown. Modern - black; Quaternary - red; Creatceaou - green, *indicates sample taken from Pullen et al. (2011) and MD-1 is from Stevens et al. (2010); arrows on lower map show approximate wind directions; yellow - westerlies; blue - winter monsoons; red - summer monsoons.
This sand is likely transported via the Yellow River and carries the
same source signatures as loess (Stevens et al., 2010; Pullen et al., 2011). The link between the Tibetan plateau, the Yellow River, the
Loess Plateau and the Mu Us now requires further testing as the desert is
clearly part of a larger-scale sedimentary system. This possibility is explored in Stevens et al. (2013).
Stevens, T., Carter, A., Watson, T.P., Vermeesch, P., Ando, S., Bird, A.F., Lu, H., Garzanti, E., Cottam, M.A., Sevastjanova, I. 2013. Genetic linkage between the Yellow River, the Mu Us desert and the Chinese Loess Plateau. Quaternary Science Reviews.
Pullen, A., Kapp, P., McCallister, A.T., Change, H., Gehrels, G.E., Garzione, C.N., Heermance, R.V. & Ding, L. 2011. Qaidam Basin and northern Tibetan Plateau as dust sources for the Chinese Loess Plateau and paleoclimatic implications. Geology, 39, 1031-1034.
Stevens, T., Palk, C.,Carter, A., Lu, H. & Clift, P. 2010. Assessing the provenance of loess and desert sediments in northern China using U-Pb dating and morphology of detrital zircons. Geologocal Society of America Bulletin.
Yang, S., Ding, Z., 2008. Advance-retreat history of the
East-Asian summer monsoon rainfall belt over northern China during the last two
glacial-interglacial cycles. Earth and Planetary Science Letters 274, 499-510.
Sun, D., Su, R., Bloemendal, J. & Lu, H. 2008. Grain-size and accumulation rate records from Late Cenozoic sequences in northern China: Implications for variations in the East Asian winter monsoon and westerly atmospheric circulation. Palaeogeography, Palaeoclimatology, Palaeoecology, 264, 39-53.
Sun, J.M., 2002. Provenance of loess material and formation
of loess deposits on the Chinese Loess Plateau. Earth and Planetary Science
Letters 203, 845-859.
Sun, J.M. & Liu, T.S. 2000. Stratigraphic evidence for the uplift of the Tibetan Plateau between ~1.1 and ~0.9 Myr ago. Quaternary Research, 54, 309-320.