Dark-green stiff clay of Late Pleistocene in the Yangzi River Delta is a buried Paleosol Bed.It possesses the basic property of soil:1.contains root holes,fragments and dark network humus of plants;2.underwent clayization;3.eluviaton and illuviation could be found;4.lacking of lamination.The distinct defferences between the paleosol and ordinary soil are:1.The upper part of the paleosol is light,stiff,and the ratio of hyperconsolidation is 2.1～2.2,but the lower part is less consolidated.This is contrary to ordinary soil; 2.The paleosol is green and yellow-green;3.The paleosol contains various types of nodules.They are mainly pyrite→siderite→dialogite→limonite and pyrolusite from top to bottom,reflecting a transition process of reducing-oxidizing environment.Oxygen-rich sea-water resolved the organic matter in the paleosol through the action of bacteria.With the consumption ot free oxygen and the reduction of oxidized ions,HS-,Fe+2,Mn+2 thus formed.This resultes in distinct changes of the colour,the hardness,the nodules and the clay minerals of the paleosol,thus changing the whole of the soil's property.
