Spatial variations of magnetic susceptibility of Chinese loess for the last 600 kyr: Implications for monsoon evolution

摘要

We examine spatial variations in magnetic susceptibility (MS) over the Loess Plateau in China based on 50 sections in order to identify spatial changes in monsoon climate at key glacial, interglacial, and interstadial intervals for the last 600 kyr. The results indicate strong coherence between MS variations during the interglacial periods and present-day precipitation and temperature patterns. This suggests that the strength of the summer monsoon had a dominant influence on the MS signals in soils, through modulating pedogenic intensity. The distribution of MS during glacial periods is characterized by weak S-N gradients and rough W-E zonal patterns, indicating a negligible effect of the summer monsoon. Interstadial patterns are intermediate between the glacial and interglacial ones. Interglacial patterns for the last 600 kyr are essentially similar, suggesting that the climate regime during these periods has not undergone significant changes and that the east Asian summer monsoon has remained the main moisture carrier. Our estimates of the relative amplitudes of climate oscillations during these time slices are consistent with earlier paleoclimate studies. These data, associated with the available susceptibility-based climofunctions, may be used to estimate spatial changes of paleorainfall and paleotemperature for these key periods and hence to test climate models.