Characteristics of Cretaceous Seismite in the Tamuchage Depression,Mongolia,and Its Significance

Based on observation of drilling cores and study of tectonic setting,seismite was recognized in the Cretaceous strata of the Tamuchage depression. Seismite is mainly characterized by various soft-sediment deformation structures such as synsedimentary faulting and microfractures,liquefaction vein,pillow structure,and accompanying structures,etc. Based on observation of drilling cores from Ta 21-9 and Ta 19-43 wells,a vertical succession of seismites was established,which is in ascending order,liquefied veins,hydroplastic deformation,axe-formed,slump,ladder-shaped microfracture,and shatter fissure,and so on,which correspond to a change process of earthquake with an intensity from strong to weak. The discovery of seismites is of great significance and will be conducive to understanding of intense action period of basin-controlling boundary fault.