Mixed-layer illite-vermiculite as a paleoclimatic indicator in the Pleistocene red soil sediments in Jiujiang, southern China

摘要: Abstract The mineralogy and chemical composition of the Jiujiang red soil sediments were investigated using X-ray diffraction (XRD), fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS). Mixed-layer illite–vermiculite (I/V) was confirmed based on conditions that a broad peak 1.0 to 1.4 nm appeared in XRD after Mg-saturation, its d-spacing did not change glycol treatment, but collapsed 1.0 nm heating, owing loss water hydroxy-cations from interlayer. mixed-layer I/V contents fluctuate throughout section show decreasing trend upwards, suggesting decreased weathering towards surface section. index alteration (CIA) values Rb/Sr ratios also exhibit upward trends, jointly revealing climate shift warm/humid cool/dry Middle Late Pleistocene. Although general evolution can be evaluated by CIA ratios, sub-climatic events within cannot identified. SiO2/Al2O3, Al2O3/Fe2O3, SiO2/Fe2O3 clearly along section, especially net-like sediments, they do reveal multiple cycles. This is because an inhomogeneous distribution SiO2, Al2O3, Fe2O3 white veins matrix non-uniform sampling. variation content strong positive correlation with changes magnetic susceptibility loess-paleosol marine oxygen isotope sub-climate cycles global scale since Therefore, only whole documented Pleistocene, disclose related deposit-pedogenesis process.