Identifying pedogenic magnetic minerals in loess from China and Siberia using isothermal remanent magnetization acquisition curves

Abstract

Aeolian loess is carried by wind and undergoes pedogenesis after deposition. Therefore, both detrital components from the source region and soil pedogenic components contribute to the magnetic properties of the loess. The pedogenic component can be identified by analyzing the coercivity spectra of loess with different degrees of pedogenesis. We used isothermal remanent magnetization acquisition curves to analyze the coercivity spectra of loess in China and Siberia and defined the low ( 100 mT) coercivity components, i.e., components 1, 2, and 3, respectively. In the arid region of Xinjiang, Northwest China, the Bole section, with negligible soil development has loess with only component 2 centered at ∼80 mT. In semiarid central China, the Xifeng section has both loess and paleosols with three coercivity components centered at ∼26 mT, ∼82 mT, and ∼960 mT. Component 1 has a pedogenic origin, and the remanence contribution increases in a positive linear relationship with the intensity of pedogenesis. In the humid region of Siberia, the Kurtak section has three coercivity components are centered at ∼23 mT, ∼78 mT, and ∼1014 mT. The remanence contribution of component 1 shows a low correlation with the intensity of pedogenesis. Component 3 is characterized by high-coercivity minerals and its remanence contribution is related to the intensity of pedogenesis. The soil development in the semi-arid Xifeng section tends to produce massive fine-grained ferromagnetic minerals, so the remanence contribution of component 1 is positively correlated with the intensity of pedogenesis. The humid pedogenic environment of the Kurtak section is prone to form high-coercivity minerals and destroys fine-grained ferromagnetic minerals, so the remanence contribution of component 3 increases with the degree of pedogenesis.