Micromorphological variation of the S 1 paleosol across northwest China

A micrornorphological approach, based upon sets of closely-spaced thin sections taken from three sites located along a climatic and depositional gradient, has been utilised to reconstruct the sequence of pedogenic and sedimentary events leading to the development of the S1 paleosol in northwest China. Two main pedosedimentary stages related to regional changes in monsoonal controls are evident at each site, although the resolution, processes and resultant features vary in a manner reflecting differences in climate and rates of loess deposition. Around Xining in the west, where loess accumulation rates were high, and pedogenic processes were restricted to shallow leaching and limited bioturbation by the low rainfall, S 1 comprises two discrete weakly-developed paleosol units separated by a less-pedogenically altered layer of loess. In contrast, at sites farther away from the loess source area in the more humid southeast, S 1 is a thinner, welded and more pedogenically-developed unit dominated by the effects of extensive leaching, bioturbation and sometimes even clay translocation processes.