Dust Sources of Last Glacial Chinese Loess Based on the Iron Mineralogy of Fractionated Source Samples

Abstract

AbstractThe Chinese Loess Plateau (CLP) is composed of an enormous volume of aeolian dust, the provenance of which is still debated. In the present study, we attempt to distinguish different sources of Last Glacial (LG) sediments of the CLP based on the iron mineralogical characteristics of different particle size fractions of surface samples from potential source areas in Northwest China. The result reveals that the iron mineral characteristics of the surface samples are spatially heterogeneous and that differences between sedimentary basins are greater than those within the basins. The contents of magnetite and goethite have a significant particle size dependency, but this is not the case for hematite. The iron mineralogical characteristics of the samples are closely related to the distribution of mountain ranges and tectonic activity in NW China. Basing on mathematical calculation, we propose that (i) the 8‐ to 31‐μm fractions, the major component of CLP loess, is a mixture of sediment weathering from NE Tibetan Plateau and Central Asian Orogenic Belt, with a majority from Tibetan Plateau; (ii) S. Alxa Plateau is the dominant source of 31‐ to 63‐μm fractions of CLP LG loess; (iii) the Qaidam Basin is the dominant source of 2‐ to 8‐μm fractions of CLP LG loess; and (iv) the material contribution from Ordos Plateau is limited to CLP LG loess, especially for the loess on the western CLP.