An EPR study on the chemical form of Mn2+ in the Chinese loess samples

Electron paramagnetic resonance (EPR) spectroscopy in combination with ther mal methods were used to identify and characterize Mn2+ in the Chinese loes s that is a multimineral system. EPR spectra of the loess samples from the classic loess-paleosol section in central China show the presence of trace amounts of Mn2+; whereas paleosol samples present no Mn2+ EPR signal. The s pectral changes upon step heating from room temperature to 1000 degrees C s uggest that this EPR signal in the loess arises from Mn substituted into Ca CO3. This study provides a direct evidence that the loess-paleosol profiles were formed under the changing redox conditions caused by a past climatic change.