Paleoclimatic significance of the temperature-dependent susceptibility of Holocene loess along a NW-SE transect in the Chinese loess plateau

摘要

We have conducted mineral magnetic investigations of samples of modem dune sand, pristine loess and present-day loess along a NW-SE transect from the northern to the central loess plateau in China. The methods used include the temperature-dependence of susceptibility (TDS) before and after citrate-bicarbonate-dithionite (CBD) treatment as well as X-ray diffraction (XRD) analysis. The XRD analyses demonstrate that magnetite and hematite both exist in the Chinese loess-paleosol sequence and its modern source area, but the TDS measurements show that magnetite is the predominant contributor to magnetic susceptibility. Maghemite is present in the pristine loess and the present-day loess due to pedogenesis. The pedogenic processes that produce the maghemite are closely linked to paleoclimate, and for this transect, precipitation appears to be the most important climatic variable. We suggest that TDS can be used as a useful method for the analysis of pedogenesis and climatic change. [References: 26]