贵州中三叠统上部垄头组的沉积性质——再论其钙结壳的成因
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Sedimentological Nature of Late Middle Triassic Longtou Formation--Re-discussion on the Origin of Its Caliche Crusts
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    摘要:

    钙结壳是土壤层之下的岩石在出露地表渗流带环境内受大气雨水的溶解,并通过上覆土壤层的淋滤而成的产物。由于雨水的不断的溶解,使原始的岩石或沉积物发生破裂,从而形成各种大小的砾块或砾石。随着雨水不断的溶解,雨水逐渐增加 CaCO_3的含量。这些富含碳酸钙的雨水,当它流到位于潜水面之上的下渗流带时,就在土壤层之下、原来岩石之上沉积了特殊的、层纹状方解石胶结物。它们往往覆盖岩石表面或沿着砾石的外缘、呈包覆状沉积,从而形成典型的层纹状钙结壳。渗滤豆粒的外皮也属于层纹状钙结壳的性质,这些外皮有向下方加厚的趋势,这表明渗流带的含碳酸钙的雨水,受重力作用影响下,具有往下悬垂现象,类似于洞穴内的钟乳石。豆粒之间的相互衔接呈多边形构造,也表明它是受重力作用而形成的构造。

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    Caliche crusts are secondary products formed by the dissolution of meteoric water on former lithified sediments and rocks during their exposure into subaerial vadose environments. Because of continuous dissolution on former lithified sediments or rocks, these sediments or rocks will be broken into various sizes of clasts and pebbles. With uninterrupted dissolution by meteoric water, these waters will be saturated finally with great amounts of CaCO3. When these supersaturated waters flow down into the lower part of vadose zone just above phreatic zone, these calcium carbonates enclosed within the waters will be deposited as peculiar, laminated calcite cements which usually encrust around breccias or clasts of various sizes, thus forming typical laminated caliche deposits. Outer encrustations of these pisolites are also believed as the nature of laminated caliche deposits. These encrustations usually show some tendencies of thickening at the underside, thus indicating that these vadose waters which saturated with calcium carbonates have the features of hanging down towards the lower by the effects of the gravitation. These features are very similar to stalactites in the caves. Polygonal structures of the pisolites indicate also that these structures are formed by the effects of the gravitation.

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范嘉松 吴亚生.2004.贵州中三叠统上部垄头组的沉积性质——再论其钙结壳的成因[J].地质学报,78(2):149-155.
FAN Jiasong, WU Yasheng Institute of Geology, Geophysics, Chinese Academy of Sciences, Beijing,.2004. Sedimentological Nature of Late Middle Triassic Longtou Formation--Re-discussion on the Origin of Its Caliche Crusts[J]. Acta Geologica Sinica,78(2):149-155.

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  • 最后修改日期:2002-09-06
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