Characteristics,origin and geological significance of rhizolith in Shidao of Xisha Islands
Characteristics,origin and geological significance of rhizolith in Shidao of Xisha Islands
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DOI：
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发表时间：
2008
影响因子：
1.8
通讯作者：
Wei Xi;Jia Cheng;Menghan Wei
中科院分区：
文献类型：
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作者：
Wei Xi;Jia Cheng;Menghan Wei
西沙群岛石岛地区地层为第四纪地层，由四层风成生物钙质砂屑岩和三层化石土壤组成，相互交错，化石土壤中有根石存在。研究表明，根石在结构、结构、成分、沉积成岩作用等方面可分为三个带，带内为泥晶碳酸盐岩，泥晶结构、环状纹层或丝状结构，中臭氧层和外臭氧层，由珊瑚藻、珊瑚、软体动物、棘皮动物、有孔虫和芳烃的碎片组成，具有细粒砂晶结构和块状或层理结构，是特殊微观化学成岩作用的产物，西沙石岛的三层根际岩标志着三个成土和植被生长阶段，风成生物钙质砂屑岩层与化石土壤层的交替层、CaO/ MgO比值、锶和有机质含量的变化记录了4个气候和风成沉积演化旋回。
The strata in Shidao of Xisha Islands is Quaternary,including four layers of eolian biocalcarenite and three layers of fossil soil,which alternate with each other.Rhizolith exist in fossil soil.Studies indicate that rhizolith has three zones in texture,structure, component and the aspects of sedimentation and diagenesis.The intrazone,composing of micrite carbonate,with micritic texture and ringlike lamina or filiform structure,is the result of replacement and petrifaction of plant root.Mesozone and exozone,composing of fragments of coralline algae,coral,mollusca,echinoderm and foraminifera and arene,with fine grain psammitic texture and blocklike or bedding structure,is the product of chemical diagenesis in special micro-milieu around plant root and difference weathering after diagenesis.Three layers of rhizolith in Shidao of Xisha Islands mark three stages of pedogenesis and vegetation growing,reflecting magnitude alteration of climatic condition.Alternating beds between eolian biocalcarenite layer and fossil soil layer,variation of CaO/ MgO ratio,strontium and organic content record four cycles of climate and eolian deposition evolution.