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Clay record of climate change since the mid‐ P leistocene in J iujiang, south C hina
Ist Teil von
Boreas, 2013-01, Vol.42 (1), p.173-183
Erscheinungsjahr
2013
Link zum Volltext
Quelle
Wiley-Blackwell Journals
Beschreibungen/Notizen
To obtain a better understanding of climate change in south C hina in the Q uaternary, a clay mineralogical study was undertaken on the red earth profile at J iujiang, using X ‐ray diffraction ( XRD ) and particle‐size distribution analysis methods. The XRD results showed that the clay minerals of the J iujiang red earth were mainly mixed‐layer illite–smectite ( I / S ), illite, kaolinite and vermiculite, with trace amounts of mixed‐layer kaolinite–smectite ( K / S ). Changes in clay mineral composition displayed a trend of three‐stage evolution. The higher mixed‐layer I / S clays and kaolinite contents in the lower portion suggest extremely warm and humid climates over the period c . 700 to c . 350 ka ago. A gradual decrease in I / S clays and kaolinite reveals a gradual climate change from warm/humid to cool/dry during the period c . 350 to c . 130 ka ago. The higher illite and vermiculite contents indicate a relatively cool and dry climate during the period since c . 130 ka ago. The particle‐size distribution pattern of the upper section was similar to that of the X iashu loess, while that of the middle to lower section was similar to those of fluvially reworked red earth. A rapid increase in the abundance of large grain‐size components at 2.6 m depth indicates an intensification of the winter monsoon and a cool and dry climate during the period, in good agreement with results from the clay mineral composition and homogeneous structure. The red earth sequences in south C hina could probably be used to test the response of tropical to subtropical regions to global climate changes.