MID-PLEISTOCENE CLIMATE TRANSITION EVENT RECORDED BY JL RED EARTH SECTION, JIUJIANG, JIANGXI PROVINCE

The data of grain-sizes prove that the Jiujiang red earth has some aeolian features. Silt is the dominant grain component of aeolian dust, counting up to 66.20%~74.02%. The particles of 15~30μm were selected as the climate proxy indicators. Based upon the ESR dating and grain size-age model, a time scale was established. It suggests that this section covers a time span from Early-Pleistocene to Mid-Pleistocene. The reticular red earth in this section was formed during 2098.4 kaBP~441.5 kaBP, and the brown-yellow earth deposited in the period of 441.5 kaBP~2332 kaBP. The 3 pbase software was adopted to analyze the climatic cycles through frequency spectrum analysis. The results show that in the JL red earth section there are cycles of 100ka, 41ka and 30ka as the records of earth's orbit elements. The climatic cycles suffered a dramatic change during the period of 734 kaBP~784 kaBP. The cycles of 41ka and 30ka corresponding to the cycle of tilting of the earth axis was transited to the 100ka cycles controlled by the earth's orbital eccentricity. The transition is the record of the world-wide Mid-Pleistocene Climate Transition Event. In addition, the spectral analysis results show that the climatic cycles of this section have its own complexity, and it is possibly related to the nonlinear feedback mechanisms of the East Asian monsoon.