安徽寿县新元古界球-枕状构造的双重成因与古地震脉动旋回研究

在安徽寿县新元古界四十里长山组下部粉砂-细砂岩沉积地层中,发育一组具有双重成因的球-枕状软沉积物变形构造.对露头剖面进行实地观测研究显示,变形构造形成于浅海陆棚边缘斜坡带的地震灾变事件层中.由于滑塌砾石落入表层粉砂质软沉积层,在地震震颤应力作用下形成具砾石核心的球-枕状体,又在地震脉动旋回性连续震颤作用下,继续沉陷至下部液化砂层中,形成了具有双重成因的球-枕状软沉积变形构造.它经受了地震、海啸、滑塌、滑褶、震颤晃动沉陷、液化泄水、软塑性紧缩变形等多项复杂的同沉积变形作用过程.显示出该地震事件具有前震阶段、主震阶段、余震阶段等多次震颤脉动旋回性地质作用的地质事件,地震能量强度最大应超过里氏7级,为研究海洋震积岩的软沉积变形及脉动旋回性过程提供了重要的实物资料.

Study on Double Causes and Paleoseismic Pulse Cycle of the Neoproterozoic Ball-Pillow Structure in Shou County, Anhui Province

The silt~fine sandstone sediments of lower Neoproterozoic Sishilichangshan Formation in Shouxian County of Anhui Province was found to host a set of ball pillow shaped soft sediment deformation structures with double causes. The study of outcrop profiles has shown that the soft sediment deformation structures formed from earthquake disaster event in shallow slope of the shelf edge. As slump gravels fell into the surface of soft silty sediments, primary ball pillow shaped bodies formed due to tremor shaking stress of earthquake. And then, under the pulsation and cycled earthquake shaking effect, the gravel continued to sink into the bottom of liquefied sand layer, forming the formation of a ball pillow shaped deformed structure with double caused stress. Our study suggests that the deposition deformation has undergone synsedimentary deformation process, such as earthquake, tsunamis, slump, slide fold, tremors shaking subsidence, liquefaction draining, gravels screen directional aligned, and the soft plastic tighten deformation, etc. It is also revealed that the earthquake is characterized by multiple cycle geological event, which contains a fore shock stage, the main shock stage and after shock stage. The intensity of seismic energy should have exceeded the magnitude 7 and this provides important information for the study of sediments deformation and the pulsation and cycle process of marine seismite.