江西赣南地区网纹红土粒度组合特征及其指示意义

Grain-size Features of the Red Earth in Southern Jiangxi Province and Its Environmental Significance

对赣南地区黄金剖面(HJ)和沙河剖面(SH)红土粒度特征研究表明:(1)两个剖面粒度组成表现出较好的一致性。粉砂(4～63μm)为优势粒组,HJ和SH剖面含量的平均值分别为51.51%、55.02%,其中粗粉砂(10～50μm)分别为29.14%、30.79%;粘粒组分(<4μm)含量平均值分别为28.69%、23.13%,风尘"基本粒组"明显富集,反映赣南红土具有风成特性。砂粒组分(>63μm)含量平均值分别为19.78%、21.84%。粒度频率由3个明显的峰段组成,概率累积曲线由两个拐点1.5Φ和10.5Φ分为三段,悬浮粒组分占优势,跃移组分和次生组占的比例相当;推测赣南红土系风成作用形成,沉积后经历了风化成壤作用的改造。(2)SH和HJ红土剖面的磁化率曲线、Kd值曲线和风化强度曲线纵向变化呈现显著的相关性,近似地出现6个峰谷旋回波动,粒度组成曲线和参数曲线也有相应的反映。初步推测赣南红土形成经历了6个"沉积-成土"旋回,对应于6次气候冷暖变化。

Grain-size distbution of the red earth of the Huangjin profile(HJ) and Shahe profile(SH) was measured in the Gannan region.The results showed that:(1)Grain-size distributions of two red earth sections in the Gannan region are very similar.The average contents of silt-fraction(4~63 μm) particle groups in the HJ and SH profiles are respectively 51.51%、55.02%.The average contents of coarse silt fraction(10~50 μm) are 29.14% and 30.79%.The average contents of clay(<4 μm) fraction are respectively 28.69% and 23.13%.The basic fraction of dust is rich,indicating there are aeolian characteristics of the red earth in the Gannan region.The average contents of clay fraction(> 63 μm) are respectively 19.78% and 21.84%.The grain-size frequency curves are made up of three-peak part.The probability accumulation curves of the red earth could be divided into three segments by two flex points of 1.5Φ and 10.5Φ.The components of suspended particles are dominant,the other two parts are very similar,which probably indicates aeolian characteristics from their parent materials in the Gannan red earth.The sedimental parent materials were reconstructed by water erosion and weathering processes.(2) The vertical change curve for magnetic susceptibility,Kd and weathering coefficient shows a rmarkable correlation.There are six-cyclic peaks and valleys.The particle distribution and particle parameters are correlated,indicating the existence of six cycles of depositional alternation with the pedogenic process in the Gannan red earth,accordingly there are six cycles of climate change.