华南沿海黄色粉土石英颗粒的扫描电镜特征及其对成因的指示

SEM study of quartz grains of yellow silt in the coastal area of South China and the interpretationof its origin

对华南沿海地区黄色粉土剖面中的石英颗粒进行扫描电镜观测,并与混杂在粉土层中的基岩风化残余石英颗粒进行对比:黄色粉土的石英颗粒以次棱角状-次圆状为主,多发育碟形撞击坑、麻面,并伴有一定的化学溶蚀及化学沉淀现象,指示风成成因;黄褐色粉土夹层中的石英颗粒表面化学结构更为发育,表明该阶段气候环境更为湿热,粉土经历了强烈的风化成壤作用。而基岩残积石英颗粒粒度粗大、棱角鲜明、贝壳状断口及新鲜断面发育,与黄色粉土中的石英颗粒所反映的成因类型、搬运动力及沉积环境存在较大差异。在以往对黄色粉土理化特征研究的基础上,本文主要采用扫描电镜观测的方法,从石英颗粒形态特征和表面结构的角度,为黄色粉土的风成成因提供了新的证据。

Scanning electron microscope(SEM)observation of quartz grains of yellow silt deposited in the coastal area of south China represented by Jin Shuitai section in central Guangdong province is compared with that of the quartz grains of weathered bedrock residuals mixed within the yellow silt layer.The morphological characters and surfacetextures of quartz grains of the studied yellow silt show clearly subangulartosubrounded shape,pitting surface and collision pits,which are typical aeolian evidences.Chemical denudation and chemical precipitation on the quartz grains of reddish-brown silt interlayer are more developed indicating a stronger weathering pedogenesis.The coarse residual quartz grains show sharp edges,poor sphericity,irregular shapes and well-developed conchoidal fractures,which is quite different from the quartz grains of the yellow silt in transportation agent and sedimentary environment.Based on the physicochemical characteristics of the yellow silt in previous study and the morphological characters and surface textures of the quartz grains in this study,a new evidence for aeolian origin of the yellow silt is provided in this paper.