Oxygen-isotope record of paleorainwater in authigenic carbonates of Chinese loess-paleosol sequences and its paleoclimatic significance

Geochemical studies on the source region of Asian dust

“…The difference of silicate CaO content between loess and paleosol is about 0.3% [27]. Sedimentation rate of glacial loess is more than twice of the interglacial paleosol [26] and the temperature and precipitation are lower in ice age [25]. Thus, it could be inferred that the weathering intensity of loess is less than half of the paleosol with silicate CaO released by weathering less than 0.3%.…”

“…Precipitation is not an important source of calcium either. Taking Xifeng for example, the concentration of calcium in precipitation is about 5.6 ppm [21], precipitation in glacial period is about half of the modern level (~300 mm/yr) [25], and dust flux is about 400 g/(m 2 ·yr) [26]. Based on these data, the amount of carbonate that can be formed from the calcium in precipitation can only make up less than 0.5% of the loess deposits.…”

“…Older eolian deposits up to the late Oligocene have also been discovered on CLP by Chinese scientists in recent years, providing an invaluable archive for the formation and evolution of aridification of Asian Interior and Asian monsoon climate as well as the environmental effects of Tibetan uplift [60][61][62]. Paleo-climate proxies have been developed in the eolian deposits, including magnetic susceptibility reflecting the intensity of summer monsoon [63], the grain size and Zr/Rb ratio recording the wind strength [40,64], the dust accumulation rate indicating the aridity of source region [26], the C and O isotope of authigenic carbonate being controlled by the type of vegetation cover and monsoon rainfall [25,65], and the Rb/Sr and Mg/Al ratios reflecting the intensity of weathering and pedogenesis [66,67]. Many of the proxies are based on the assumption of stable dust provenance, which attributes the changes of proxy value either to the transport processes or to weathering and pedogenic processes after deposition.…”

Nd and Sr isotopic characteristics of Chinese deserts: Implications for the provenances of Asian dust

“…/j.gca.2007 Long-range transports of Asian dust have been identified in China (e.g., Liu, 1985;Ding et al, 2001), Korea and Japan (Kanayama et al, 2002a,b;Mori et al, 2002), North Pacific Ocean (Nakai et al, 1993;Pettke et al, 2000), western America (Wilkening et al, 2000), Greenland (Biscaye et al, 1997;Svensson et al, 2000;Bory et al, 2002Bory et al, , 2003, and Europe . The Ancient dust deposits in these regions, for example, the loess-paleosol sequences in Chinese Loess Plateau, provide archives to trace the atmospheric circulation pattern, as well as paleoclimate change Chen et al, 1999Chen et al, , 2006Ding et al, 2001;Guo et al, 2002;Li et al, 2007). Mineral dust particles are highly heterogeneous, but are commonly treated as a relatively homogeneous group, and this may lead to increasing uncertainties in the atmospheric chemistry and climate models (Buseck and Pó sfai, 1999), and misleading the interpretation of the environmental proxies archived in dust deposits, since evidences show that the dusts originated from different source regions have different physicochemical properties (e.g., Zhang et al, 1993Zhang et al, , 1997.…”

Strontium isotopic and elemental characteristics of calcites in the eolian dust profile of the Chinese Loess Plateau during the past 7 Ma

“…Thus, carbonates in eolian deposits perhaps record much information on paleoclimate and paleoenvironment. In recent decades, researchers have mainly investigated carbonate contents and C and O isotopes in carbonates from eolian dust profiles to explore the evolutions of paleotemperature, paleoprecipitation and the East Asian summer monsoon (Han et al, 1997;Ding and Yang, 2000;Li et al, 2007). However, only a few pioneers studied chemical weathering associated with the East Asian summer monsoon in the Chinese Loess Plateau using the method of strontium isotope tracing.…”