A Discussion on Deformation Structures of Early Silurian Soft Sediment and Its Trigger Mechanism in the front of Micangshan Mountain

Key words: 
• soft sediment deformation structures /
• storm action /
• Early Silurian /
• the front of Micangshan

Abstract: As we know, soft sediment deformation structures in the geological history can be found in different space-time sedimentary rocks, however, its deformation process, active force and trigger mechanism are still in dispute in academia. Through the observation on the field outcrops in the front of Micangshan, there develop multiple sets of soft sediment deformation structures in the sandstone, siltstone and shale strata in Early Silurian. The distribution of the layer is stable, and each stratum has different morphological characters. According to its morphological characteristics and stratigraphic distribution, it can be divided into wavy deformation structure, convolute bedding, pillow structure and flamy structure. What's more, they always accompany with hummocky cross-beddings. On the basis of the lithologic character and profile structure combination of the soft sediment deformation structures, they can be divided into three types, which all belong to the continental shelf sedimentary environments. Based on the characteristics of the soft sediment deformation structures and combined with the paleoclimate and paleo-plate materials, carbon isotope data, and modern hurricane research results, the study area is located in the north of the equator. There is hot and arid, and the storm occurs frequently. The soft sediment deformation structures of the research area are mainly the consequence of the storm. Unconsolidated sediments are oscillated and liquefied when the strong storm hit the bottom of the sea. The discovery and the trigger mechanism of the soft sediment deformation structures in the front of Micangshan has a great significance for studying the recovery of the paleoclimate and paleo-plate, and the evolution of ancient Yangtze plate.