Abstract:

The major northern hemisphere climate systems, including the mid-latitude westerlies and Siberian high, intersect over central Eurasia; the thick piedmont loess of this region therefore represents a potential archive of dynamical changes in these systems over long time scales. In this study we focus on loess deposits along the northern Tien Shan piedmont in eastern Kazakhstan, where wind trajectory models suggest a stronger influence of the Siberian High and polar jet than the better studied westerly-dominated Ili basin further south. In particular, we investigate the properties of ubiquitous magnetic minerals in the loess: their concentration, mineralogy and thermal properties are closely linked to environmental conditions prevailing during soil formation.
we propose that the post-~39 ka variations in loess magnetic properties might reflect changing contributions from different sediment source regions, because the observed increase in magnetic signal associated with higher sand content cannot be attributed to pedogenic magnetic enhancement. We suggest that post–~39 ka variations in loess magnetic properties reflect changes in the relative contributions of different sediment sources, since the observed increase in magnetic concentration with higher sand content cannot be explained by the classic pedogenic magnetic enhancement model.