Linking coarse silt production in Asian sand deserts and Quaternary accretion of the Chinese Loess Plateau

Abstract

The Chinese Loess Plateau (CLP) is a large, spatially well defi ned and persistent zone of loess accumulation developed near the fl uctuating northwest margin of the East Asian monsoon. Many studies have analyzed its loess sediments to provide insights into paleoclimatic conditions. Although spatial and temporal variations in the grain sizes of CLP sediments are fundamental to this effort, controversy over the origin of the dominant coarse quartz silt has limited interpretations. Reexamination of the spatial pattern of grain-size distribution across the CLP and a fi eld-scale experiment conducted in the Gobi Desert revealed a genetic association between the coarse silt fraction of the loess and primary production of coarse silt through eolian abrasion of sand in the proximal Mu-Us, Tengger, and Badain Jaran sandy deserts. Our results demonstrate the effectiveness of eolian abrasion of quartz sand in primary coarse silt production in Central Asia and identify this process as the most consistent with the wellrecognized systematic northwest-southeast depositional pattern of the CLP. We suggest that only abraded coarse quartz grains transported short distances by long-term persistent eolian activity can build up thick loess sequences to form a massive and spatially well defi ned loess plateau. These results decouple the production and transport of coarse silt and fi ner silt and clay particles, which have a more distant and wider provenance, changing the constraints on previous paleoclimatic reconstructions.

Eolian cannibalism: Reworked loess and fluvial sediment as the main sources of the Chinese Loess Plateau

“…In the modern interglacial climate, dust storms originate north and northwest of the Chinese Loess Plateau, in the Gobi Desert, commonly during the breakdown of the Siberian High in Spring (Roe, 2009), and they track across the Badan Jaran, Tengger, and Mu Us Deserts (Wang et al, 2004). These desert areas are thought to be the main source areas for the coarse fraction of the modern dust to the plateau, though the exact locus of dust generation in these regions-piedmont alluvial fans, dried lake basins, or sand dune fields-is widely debated (Pye, 1995;Sun, 2002;Amit et al, 2014). Additionally, recent provenance studies of loess have also highlighted the importance of reworking of local substratum rocks (mostly pre-Quaternary terrestrial sediment) and of fluvial detritus brought by the Yellow River, with headwaters in northeastern Tibet (Fig.…”

Geochemical evidence for seasonal variations in potential loess sources of the western Chinese Loess Plateau

“…In addition, particle size analysis and previous studies indicate that the coarse fractions of the fallout at the present sample site were not generated from local sources because local surface soils are enriched in fine calcium carbonates (CNEMC, 1990). The current data do not reveal whether the thick loess stratigraphic sequences on the CLP were generated from the Mu Us, Tengger, and Badain Jaran sandy deserts (Amit et al, 2014), although the high proportion of coarse fractions within the fallout shows that at least part of the loess at the site was derived from adjacent deserts, the nearby Yellow River, and associated systems (Stevens et al, 2013a,b), and was only transported a short distance before being deposited.…”

Deciphering magnetoclimatological patterns of late Early to early Middle Pleistocene loess–paleosol sequences in the western Chinese Loess Plateau

“…In the hinterland of the CLP, spatially consistent bulk grain size variability implies that the transport and deposition of loess materials which have undergone thorough mixing, multiple recycling, and grain-size sorting processes are largely controlled by regional winds, and that dust inputs from local sources may be minor (Jahn et al, 2001;Ding et al, 2002;Maher et al, 2009;Amit et al, 2013). In addition, the widespread consistency in the phasing of susceptibility and bulk grain size records further suggests that the summer monsoon is anti-phased with the winter monsoon, at least on orbital timescales (Ding et al, 2002;Hao et al, 2012).…”