黄河三角洲冰携泥现象及冰成沉积构造

ICE-CARRYING PARTICLES AND ICE-INDUCED SEDIMENTARY STRUCTURES IN YELLOW RIVER DELTA

在黄河三角洲出现一种特殊的、冰 - (水 ) -泥共同作用的冰携泥现象。冬末春初 ,冰雪融化 ,位于冰层底部的细粒碎屑沉积物质 (粉砂或粘土 )常被冰向上携起 ,当冰融化后形成了一些冰成沉积构造。通过野外实地考察和实验模拟研究 ,冰携泥作用过程可以分为三个阶段 :沉积物冰劈破碎阶段 ,冰层底部融化 -泥沙被冰垂向搬运阶段及泥沙下落 -冰成沉积构造形成阶段。在冰携泥的整个过程中形成的冰劈裂缝、冰成球粒和冰成泥沙片等特殊的沉积构造 ,是冰携泥现象留下的重要的地质记录 ,对于研究这一特殊现象及其形成的环境条件具有重要的理论意义。造成冰携泥现象有两种可能机制 :冰层中的毛细作用和冰融水的对流作用。前者只在冰融水能及时渗漏或排出的开放系统中发生作用 ;而在冰融水不能被渗漏或排出的密闭系统中两种机制共同发生作用。

A special phenomenon,vertical movement of ice-carrying particles,resulting from interactions among ice,water and silt (mud) particles in the Yellow River delta was studied through field observations and simulation experiments. In late winter and early spring,ice melts and the fine sediments (silt or mud particles) under the ice layer are carried upwards with the melting of ice. Studies show that the processes of vertical movement of ice-carrying particles may be divided into three stages,i.e. fragmentation of sediments,part melting of ice and vertical carrying of silt or mud particles,and silt or mud particles falling and some ice-induced sedimentary structures forming. These sedimentary structures of ice-split seams,ice-induced pellets and ice-induced silt or mud slices are important records for existing of ice and reconstruction of sedimentary environment and climate. In addition,the dynamical mechanism of this special movement is discussed in this paper,and two dynamical mechanisms are worked out. The first one is capillary action,and the second thermal convection of ice-melt water. Capillary action is the only dynamics in the open system where the ice-melt water can be discharged or leaked out,and the two dynamical mechanisms contribute together to the special movement in the close system where the ice-melt water can not be discharged or leaked out.