Application of Fourier Transform Infrared (FTIR) Spectroscopy in Quantitative Mineralogy of the South China Sea: Example of Core MD01-2393

The Fourier transform infrared(FTIR)spectroscopy has a large advantage in paleoenvironmental study, through its measurement of various minerals in absolute proportions. This paper reports the mineral contents of Core MD01-2393, located off the Mekong River estuary in the southern South China Sea, using the FTIR method.Along with a comparison of semiquantitative determination by the X-ray diffraction(XRD)method, we present a reconstruction of the erosion and weathering history of the eastern Tibetan plateau and the Mekong basin since 190 ka in the late Quaternary. The results indicate that the bulk kaolinite/quartz ratio and clay-sized(< 2μm)kaolinite/smectites ratio may serve as mineralogical proxies of erosion and weathering occurrence in source areas. Since 190 ka in the eastern Tibetan plateau and the Mekong basin, the mechanical erosion has been stronger in glacials than in interglacials, while the chemical weathering is stronger in interglacials than in glacials, implying an Asian monsoon-controlled erosion and weathering history. During the Holocene, although both the bulk kaolinite/quartz ratio and clay-sized (< 2μm)smectites/kaolinite ratio indicate a similar evolution process of erosion and weathering, the bulk kaolinite/quartz ratio presents a stronger mechanical erosion ability. This phenomenon could be affected by rapid sea-level changes in the Mekong River estuary.