论文部分内容阅读
长江三角洲晚更新世暗绿色硬粘土层是一个埋藏的古土壤层。它具有土壤的基本性质：（１）具植物根孔、植物碎屑及网状黑色腐殖质；（２）具粘土化作用；（３）存在淋溶、淀积作用；（４）缺乏层理。但与一般土壤却又有明显的区别；（１）上部致密、坚硬，超固结比２．１～２．２，下部则固结程度较差，与一般土壤剖面正好相反；（２）呈绿色和黄绿色；（３）普遍合形态各异的结核，其成分由上至下为黄铁矿→菱铁矿、菱锰矿→褐铁矿、软锰矿，反映由还原－氧化环境的过渡。原因在于早期成岩作用的改造使其特征发生了变化。富氧的海水在细菌的作用下，使古土壤中的有机质被分解，从而使其具备了早期成岩作用的条件。伴随着游离氧的消耗以及氧化离子的还原作用，形成硫化氢、低价铁、低价锰等，使古土壤的颜色、硬度、结核和粘土矿物发生了明显的变化，从而改变了古土壤的整体面貌。
The late Pleistocene dark green hard clay layer of the Yangtze River Delta is a buried ancient soil layer. It has the basic properties of soil: (1) with plant root holes, plant debris and reticulate black humus; (2) with clay; (3) the existence of leaching, deposition; (4) lack of bedding. (1) The upper part is dense and hard, the over consolidation ratio is 2.1-2.2, while the lower part is less consolidated, which is opposite to the general soil profile. (2) Green and yellow-green; (3) Generally, the nodules with different morphological conformations are pyrite → siderite, rhodochrosite → limonite and pyrolusite from top to bottom, reflecting the transition from reduction-oxidation environment. The reason is that the transformation of the early diagenesis changed its characteristics. Oxygen-rich seawater under the action of bacteria, the ancient soil organic matter is decomposed, so that it has the conditions of early diagenesis. Along with the depletion of free oxygen and the reduction of oxidized ions, hydrogen sulfide, low-valent iron, low-cost manganese and the like are formed, causing obvious changes in the color, hardness, tuberculosis and clay minerals of ancient soils, Overall look.