西秦岭上三叠统浊积岩系中波痕的主要特征及其成因探讨  

A Discussion on Main Characteristics and Origin of the Ripple Marks of Upper Triassic Turbidites in west Qinling Mis.

作　　者：张晓宝[1] 方国庆[1] 何海清[1] 

机构地区：[1]中国科学院兰州地质研究所

出　　处：《沉积学报》1994年第4期124-131,共8页Acta Sedimentologica Sinica

摘　　要：西秦岭上三叠统为一套半深海环境中形成的陆源碎屑浊积岩系，于该该积岩系中发现了大量的波痕。本文详细研究了这些波痕的形态特征及其与鲍马尾序和浊积岩相组合的关系。研究结果表明这些波痕是浊流演化过程中转化而来的牵引流作用于底部床沙形成的。For a long time. ripple marks were often regarded as one of sedimentary indicators of shallow water, bUt large quantities of them were also found in bathyal terrigenous elastic turbidites of Upper Triassic of west Qunling Mis. The ripple marks characterize that (1)they occour on the surface of T. of Bouma sequence, which means that they were formed by tractive currents derived turbidity flows, (2) they exist in the lobe factes facies associations of seafloor fan sequencas, which indicates that the most favourable hydrodynamic conditions to form them appeared in outer fans,(3)they are all symmetrical, which shows that tractive currents to form them were unidirectional,(4)They ate small-scale, which proves that the velocity .of tractive eurrents and the grain size ofbottom bed sands varied in a certain extend, (5) their wavelengths and heights are directly proportional to the thickness of turbidites, which means the strength of tractive currents was controlled by the scale and strength of turbidity nows, (6)the shape of wave crests and troughs are smooth and the shapes of ripple ridges are tegularly changeable, (7)their thepes and scales are closely related with those of ripple laminations in Te intervals of Bouma sequence, who reflects that they were two forms of expression produced by the same tractive currents, (8) The flow directions determined by ripple marks are consistent with those determined by bottom maths,which reflects that the flow directions of tractive currents were controlled by there sf turbidity. The characteristics above reflect that ripple marks occoured not only in shallow-water enviroments but also in deep water enviroments.

关 键 词：浊流 牵引流 浊积岩 波痕 成因 

分 类 号：P588.2[天文地球—岩石学]