Assessing the provenance of loess and desert sediments in northern China using U-Pb dating and morphology of detrital zircons

Abstract

Chinese loess is regarded as one of the most detailed and long-term archives of climate on land. However, there is still signifi cant controversy over the deposit's origin, limiting interpretation of the sedimentological and paleoclimatic mechanisms responsible for its emplacement. Here this is addressed through morphology and the fi rst laser ablationinductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb ages of detrital zircons from loess (last glacial age; northern Loess Plateau). These are compared to zircon U-Pb age spectra from desert and sandy lands surrounding the Loess Plateau. Surface samples were taken from the Tengger and Mu Us deserts, as well as the Horqin and Otindag sandy lands. The results demonstrate that zircon U-Pb ages can discriminate between potential source areas and highlight both similarities and differences in age spectra for the desert and sandy land samples. Most signifi cantly, the loess age spectrum shows no single affi nity to any of these regions and exhibits zircon ages associated with granitoid rocks representing tectonic events in both west and east northern China. Furthermore, and in contrast to proximal deserts, a signifi cant proportion of zircons from the loess show affi nities with rocks cropping out in the Qilian Mountains. The euhedral form of many of these grains further suggests direct transport from these crystalline source rocks, in contrast to previously hypothesized production or storage in deserts. Thus, dusttransporting storms tracked from the west during the last glacial maximum, although this does not explain all the zircon variability and implies multiple sources and stormtrack variation over the depositional period.

Geochemical studies on the source region of Asian dust

“…Compared with the average signal provided by Nd, Sr, Pb isotopes, age spectra of zircon have advantages reflecting the multiple stages of rock forming in the source regions. Xie et al [48] and Stevens et al [49] found that the distributions of zircon age between several deserts in North China differ significantly and have potential to distinguish the PSAs of Asian dust. There are also some limitations when applying zircon age distribution as source tracer of Asian dust: (1) Picking and measurement of zircon is time-consuming.…”

Geochemical and magnetic characteristics of aeolian transported materials under different near-surface wind fields: An experimental study

“…Throughout the Quaternary, dust emissions from these regions, which include the Tarim Basin, the northeastern Qinghai-Tibetan Plateau (Honda et al, 2004;Stevens et al, 2010;Pullen et al, 2011), the Ala Shan Plateau, and the Southern Gobi Desert of Mongolia (Sun et al, 2000(Sun et al, , 2002a, have been the source of the material transported to form vast accumulations of dust such as those on the Chinese Loess Plateau (Liu, 1985). Transported materials provide evidence concerning atmospheric circulation patterns as well as dust traces in ice cores in Arctic regions (Bory et al, 2002(Bory et al, , 2003,and have been used as proxies for past climate changes (Hao and Guo, 2005;Bloemendal et al, 2008;Sun et al, 2008Sun et al, , 2010 in depositional areas.…”

A Review of Recent Advances in Red-Clay Environmental Magnetism and Paleoclimate History on the Chinese Loess Plateau

“…Unfortunately, Guo Z. T. et al (2001)'s work was only performed in one section, so it remains to be explored if similar observations can be found for other lower red-clay sediments of similar age at different locations on the CLP. Zircon U-Pb age distribution patterns have proven to be particularly useful for tracing the provenance of Chinese loess (Stevens et al, 2010;Pullen et al, 2011). We have generated some zircon U-Pb ages (Nie et al, 2014a) from the Chaona red-clay section (Figure 1).…”