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震积岩是灾变性事件岩的典型代表,是具有震积构造和震积岩序列有一定成因联系的一组岩石的总称。成都金沙遗址区全新统地层中首次发现震积岩,该地层自下而上为底部砾石层、中部暗色(含炭)泥质层、上部褐黄色土壤层,整体属河流冲积物。通过野外观察,研究区发育一组走向SE120°的正断层,断层两盘的底部砾石层顶界面有明显的错断。构成地垒构造;在IT6511、IT6610层位中的断层带中见明显阶梯状断裂,其以张性正断层为主,断距约为10~90cm。在靠近阶梯状断裂的IT6512、IT6613-6614层位中发现一系列地震成因的软沉积物变形标志及破裂构造,包括砂土液化(脉)、液化卷曲变形构造、负载构造、微断裂、地裂缝、震塌岩等。分析认为这些软沉积物变形标志及破裂构造是由同期地壳活动引起的地震作用形成的。金沙遗址区震积岩的发现,对研究四川盆地全新世以来的古环境有重要意义。
Seismite is a typical representative of catastrophic event rocks, and is a general term for a group of rocks that have a certain genesis of seismogenic structures and seismites. For the first time, seismite rocks were found in the Holocene strata in the Jinsha site of Chengdu. The strata from bottom to top are the bottom gravel layer, the middle dark (charcoal) mudstone layer and the upper brownish yellow soil layer, which are generally alluvial rivers. Through field observation, a group of normal faults developed toward SE120 ° are developed in the study area. There is a clear fault at the top of the bottom gravel layer at both sides of the fault. Constitute a basement structure; IT6511, IT6610 layer fault zone in the obvious ladder-shaped fracture, which Zhangzhang normal fault, the fault is about 10 ~ 90cm. In the IT6512 and IT6613-6614 layers close to the stepped faults, a series of seismic signatures and ruptures of soft sediments have been found, including sand liquefaction (liquefaction), liquefaction and crimp deformation structure, load structure, micro-faults and ground fissures , Collapsed rock and so on. It is considered that these deformation signs and ruptures of soft sediments are formed by the seismic action caused by the same period of crustal activity. The discovery of seismites in the Jinsha site is of great significance for studying the paleoenvironment since the Holocene in the Sichuan Basin.