河床底部沙火山特征、演化及其研究意义

沉积后尚未固结的砂体在外部动力的干扰下容易发生液化,形成沙火山、液化砂岩脉等沉积构造,地震是触发液化的最常见动力.在河床现代沉积中发现大量的沙火山构造,其产生过程虽受人为活动影响,形成条件却在盆地特殊构造部位可以满足,分析其特征、演化及动力可以为震积岩及其他成因软沉积变形研究提供参考.研究结果显示,不同规模及对应特征的...

Characteristics,Evolution and Research Significance of Sand Volcanoes in River Beds

Unconsolidated sand bodies are prone to liquefaction due to external forces， forming sedimentary structures such as sand volcanoes and liquefied sandstone veins. Earthquakes are the most common triggers of liquefaction. A large number of sand volcanic structures were discovered in modern river bed sediments. Although their generation is affected by human activities， their formation conditions occur in particular structural parts of sedimentary basins. Analysis of their characteristics， evolution and dynamics provides references for the study of seismites and soft-sediment deformation in other types of formation. This study found sand volcanoes of different scale and characteristics at different evolutionary stages. Small-scale sand volcanoes have a small crater and no overflow channel， and turbid water is ejected from the crater during the growth stage. The presence of clear water and the generation of overflow channels in a sand volcano indicate that it has entered its extinction stage. The volume of a sand volcano gradually increases after it is produced， the outflow water becomes clear and overflow channels are generated. This increases its size， and re-deposition then takes place after reworking. It is suggested that sand volcanic structures are formed when earthquake or fault activity produces sufficient pressure difference between the parent base rock and the surface to fracture weak zones in the overlying strata. Sand volcanoes formed by low pressure differences may be more universal.