黄河三角洲冰冻沉积构造及其环境意义

Ice-frozen Sedimentary Structures and Their Significance for Environment in the Yellow River Delta

采用野外定位连续观测和实验模拟的方法 ,研究了各冰冻构造的特征和成因。冰冻沉积构造是冰成沉积构造的主要类型之一。与水成沉积构造一样 ,冰成沉积构造也有丰富的类型和独特的特征。在黄河三角洲新识别出 6种冰冻沉积构造 :冰劈裂缝、冰成滑痕、冰塌裂缝、冰成球粒、冰蚀波痕和冰位痕。其中 ,冰劈裂缝、冰位痕分布最广 ,成因与冰晶生长有关 ;冰塌裂缝、冰成滑痕分布较局限 ,受冰层垮塌和滑动控制 ;冰成球粒与冰劈作用和冰携泥作用有关 ;冰蚀波痕为冰对波痕强烈改造的产物。综合黄河三角洲现代冰冻构造和胶莱盆地莱阳组马耳山段地层中冰冻构造的识别和环境解释认为 ,冰冻构造对季节冰冻 (冻土 )的存在 (± 0℃的气候条件 )和河床、河漫滩。

Ice formed sedimentary structures, like water formed ones, are also abundant and characteristic in nature. Ice formed sedimentary structures can be divided into two categories, i.e. ice frozen sedimentary structure and ice molten one according to the factors controlling their formation. Observations of some points in field and laboratory simulation with sediments and water from Yellow river are used in this paper to describe the characters and origin of ice frozen sedimentary structures. Six sedimentary structures, ice split seams, ice slid marks, ice collapsed seams, ice induced pellets, ice eroded ripple marks and ice level marks, are newly found in Yellow River delta. Observations show that ice split seams and ice level marks, most widely distributed, have something to do with growth of ice crystals, that ice collapsed seams and ice slid marks, more partly distributed, are formed by the collapse and slippage of ice beds, that ice induced pellets are formed by ice splitting action and ice carrying particles action, and ice eroded ripple marks are the results from strong reworking of ice to old ripple marks. Distinguishing and environment interpretation of ice frozen sedimentary structures in Yellow River delta and Maershan member of Laiyang formation in Jiaolai basin suggest that the existing of ice frozen sedimentary structures is the important indication for the seasonal frozen soil ( the temperature about ±0℃) and sedimentary settings of riverbed, delta, flood land or tidal flat.