福建永安地区网纹红土粒度特征及其成因指示意义

为了探讨首次在闽西发现的网纹红土的成因，采用将永安地区网纹红土的粒度实验结果与典型风成沉积物、现代河流沉积物以及其他地区的网纹红土相对比的方法，对位于闽西永安地区的网纹红土剖面进行了粒度分析。结果表明:永安地区网纹红土以粉砂级组分为主，黏粒组分次之，砂级组分最少，全部样品属于黏土质粉砂；剖面从上到下粉砂级组分、黏粒组分逐渐增多，砂级组分明显逐渐减少；10~50 μm粒组体积分数均值为29.71%，远低于典型风成沉积物；沉积物岩性三角图、粒度参数特征、粒度参数散点图、M_z-A图和M_z-L图以及频率曲线显示永安地区网纹红土不是风积成因，但也不是典型的冲积成因；判别函数结果均为正值，显示了水成成因；永安地区网纹红土的成因是两方面的，为冲积成因下经过强烈化学风化作用的产物，福建其他地区、江西泰和以及广东东江一级阶地的网纹红土也具有相同成因。研究结果进一步明确了福建省境内网纹红土的分布，同时更深入理解与认识了网纹红土的成因。 

Grain size characteristics and origin of red earth in Yong'an,Fujian Province

Based on analyzing the grain size of a red earth profile in Yong'an, which is the first discovery of red earth in western Fujian province, and comparison of grain size result in Yong'an, typical eolian deposit, modern fluvial sediment and red earth in other areas, the causes of the red earth in Yong'an are discussed in this study.The results show as follows: The component particles of the red earth in Yong'an are silt predominantly, clay secondly and sand least. All the samples name clayey silt; silt and clay increase gradually and sand decreases obviously from top to bottom of the profile.The average content of 10-50 μm is 29.71%, and far less than typical atmospheric dust sediments; Sand-silt-clay triangular plot, characteristics of grain size parameter, scattergram of grain size parameter, A-M, L-M chart and frequency curves indicate the red earth in Yong'an is neither aeolian origin nor typical alluvial origin.All of the discriminant analysis results are positive value, which display the water flow action.The red earth in Yong'an is the product of intense chemical weathering after alluvial origin; The red earth of other areas in Fujian Province, Taihe in Jiangxi Province and the first terrace of Dong River in Guangdong Province have the same origin.This study has further identified the distribution of red earth in Fujian province, and origin mechanism of red earth.