The spatial characteristics of the detrital-zircon age spectra among different sites are more complicated than the glacial-interglacial patterns. Specifically, except for Xifeng, glacial samples show similar age populations in the 560–360 Ma and 360–200 Ma ranges, respectively, albeit the peaks are different to some extent (Figures 2a, 2c, 2e, 2g, and 2h). In contrast, paleosol samples show notable variations in the proportion of the 360–200 Ma zircon grains, increasing gradually from the western CLP to the eastern CLP, from 3.7%, 17.6%, and 23.9% for Xining, Xifeng, and Weinan, respectively (Figures 2b, 2d, and 2f). This different glacial-interglacial pattern of age spectra among Xining, Xifeng, and Weinan indicates the dust provenance on the CLP is heterogeneous and spatially variable, possibly for the following reasons. First, the sediments in the potential source areas in northern China and southern Mongolia show a predominant zircon age population in the range of 360–200 Ma (47.7%), with a relatively smaller proportion (14.1%) of zircon grains in the range of 560–360 Ma (Figure 2i) [Stevens et al., 2010; Xie et al., 2007, 2012]. However, the areas in the northern Tibetan Plateau and western China are predominated by the 560–360 Ma zircon grains, with a relatively limited (<20%) proportion of zircons in the range of 360–200 Ma (Figures 2j and 2k) [Gehrels et al., 2003a, 2003b, 2011; Lease et al., 2007, 2012; Li and Peng, 2010; Pullen et al., 2011; Xie et al., 2007; Yue et al., 2005]. Hence, we argue that 1) the major age population of 560–360 Ma in all the aeolian samples is mainly derived from northern Tibetan Plateau and western China, as previous studies suggested [Pullen et al., 2011; Stevens et al., 2010], rather than northern China and southern Mongolia, and 2) the eastwardly increase of the 360–200 Ma proportion in the paleosol samples likely indicates that the source contribution from northern China and southern Mongolia increases eastwardly under a NW-SE climate pattern during interglacial periods [Hao and Guo, 2005; Lu and Sun, 2000]. Second, in loess samples, the relative proportions of the 560–360 Ma and 360–200 Ma zircon grains are closely similar (Figures 2a, 2c, 2e, 2g, and 2h), which cannot be simply explained by materials from the arid regions in northern China and southern Mongolia nor by the source contribution from northern Tibetan Plateau and western China, and thus suggests a mixing of sources from these regions. Third, the late Cenozoic zircon grains, although mostly with concordance <90% except one, are probably derived from the northern Tibetan Plateau, as concluded by Pullen et al. .
 Additional lines of evidence support the interpretation that the dust provenance of the CLP is heterogeneous and spatially variable. First, the huge area of the CLP contains an immense volume of silts and finer-sized particles that must involve multiple sources. It has been argued that no specific desert is able to offer such vast amounts of silt materials required to form the CLP [Maher et al., 2009]. Second, detailed reconstruction of wind patterns during the last glacial-interglacial cycle has demonstrated that the two most important agents for transport of dust to the CLP were northwesterly and westerly winds, but lack of northeasterly wind [Lu and Sun, 2000]. This wind pattern would result in the lack of dust materials transported from the arid regions north of CLP, such as Mu Us desert, to the western CLP, although these northern regions are probably important sources for the eastern CLP [Yang and Ding, 2008].