九江JL红土剖面记录的中更新世气候转型事件

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

  • 摘要: 粒度测试表明九江红土具风成特征。粉砂(4~63 μm)为优势粒级,含量为66.20%~74.02%,富集风尘粒组。选择敏感粒组15~30 μm作为气候代用指标,根据ESR测年和粒度年龄模型,建立JL剖面时间标尺,结果表明其沉积时代为2 098.4~233.2 kaBP,跨早、中更新世。下段网纹红土的沉积年龄为2 098.4~441.5 kaBP,上段棕黄色土的沉积时代为441.5~233.2 kaBP。基于3PBase软件对234~2 084 kaBP期间气候周期的频谱分析,九江JL红土剖面记录了准100 ka、准41 ka和准30 ka的地球轨道要素变化周期,并在734~784 kaBP期间,气候周期发生了转型,由之前的准41和准30 ka地轴倾斜率周期变成之后的准100 ka地球轨道偏心率周期,这一信号响应了全球范围内中更新世气候转型事件。谱密度分析还表明剖面气候周期具复杂性,可能与东亚季风的非线性反馈机制有关。

     

    Abstract: 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.

     

/

返回文章
返回