Search

The Asian interior has the largest mid-latitude arid zone in the Northern Hemisphere, and so has become increasingly attractive for studying the initiation and the past extent of aridifi cation in this zone. Given the enormousness of the Asian interior, it remains unclear how old and extensive the eolian deposits might have been, and what wind regimes have been responsible for the formation of the mid-latitude arid zone. Here we report new eolian records of widespread Tertiary eolian deposits in a region far from the Chinese Loess Plateau, the giant Junggar inland basin of northwestern China. Our results demonstrate that the earliest eolian deposition initiated ca. 24 Ma. We interpret that the Tertiary eolian dust in the Junggar Basin was transported by westerly winds, possibly from areas in Kazakhstan; the dust differs from the airborne dust transported by winter monsoon winds from the deserts of Mongolia and northern China that accumulated on the Loess Plateau. These results further reveal that the climate pattern, similar to that of the present, has prevailed at least since the latest Oligocene in Central Asia. [ABSTRACT FROM AUTHOR]

Controversy exists regarding the sources of the eolian dust for the immense Loess Plateau of north-central China, the largest accumulation of windblown bess in the world. Because the bess accumulation rate, unit thickness, and particle size all decrease from northwest to southeast, it has long been thought that the northern deserts, especially the Mongolian Gobi, are the major bess source, a view supported by newly applied mineralogical provenance techniques (electron spin resonance, ESR). Here, we examine surface samples from the Gobi Desert and compare their magnetic and geochemical properties with those of last glacial bess samples from across the Loess Plateau region. The mineralogy, geochemistry, and magnetic properties of Gobi Desert samples are variable (most likely reflecting local lithobogical complexity), distinctive, and, critically, nonoverlapping with the notably homogenous characteristics of the last glacial boesses spanning the Loess Plateau. It is likelythat the source areas for the plateau encompass a much larger area than any one proximal desert region, in order to account for (1) the extreme degree of mixing, (2) the volume of bess generated and transported, and (3) the mineralogical and magnetic mismatch evident here between the Mongolian Gobi samples and the last glacial bess. [ABSTRACT FROM AUTHOR]