Characteristics and significance of seismite of Silurian in member III at Shahejie Formation

Abstract

Based on studies of regional tectonic setting and the observation of drilling cores, the seismite is recognized in member III at Shahejie Formation in the Xianhe area of the Dongying sag. The principal mark of the seismite is the develop ment of all kinds of soft sedimentary deformation structures, such as micro-step fault, intraformational minor fold, deformation, vibrational liquefied sandstone dike and seismic breccias. By observing the drilling cores of He 152, Wang 59, Niu 38, Niu 22 and so on, we found that the vertical sequences of the seismite are different because of the differences in structure and seismic intensity. We also found that different seismite structures are formed by different seismic intensities and that the relationships between seismite structures and paleoearthquakes were further confirmed by studying the relationship between all kinks of seismite structures and seismic intensity. Researches on reservoirs show that seismite can be an effective reservoir. These researches provide an important geological theoretical foundation for the study of the tectonic evolution of the Dongying sag and for seismite identification and description, and also supplies evidence for the researches of paleoearthquakes.