Study on the distinguishing marks of seismites in clastic rock strata of Paleogene in Jiyang depression

Key words:  Jiyang depression  Paleogene  clastic rock  seismites  distinguishing mark

Abstract:

The seismites are developed through the formed sediments reformed by seismic forces in lacustrine basin. Establishing the accurate and reliable distinguishing marks is one of the most criticel problems of researching seismites. Based on core observation， thin section and Sraging logging analysis，the typical distinguishing marks and genesis of seismic disaster event in arenaceous- pelitic sediments，Shahejie formation of Paleogene in Jiyang depression were discussed. During earthquake， seme deformation structures (step microfault，microfissure and mixed layers)，sedimentary and diagenitic structures (liquefied sandstone vein， liquefied mud-stone vein，water-escape structure，pillow structure，bal structure，pinch-and-swell structure and convolute lamination) and special rodk (seismic corrugated rock， shattering rock， seismic fall-massss and liquefied breccia) are formed. The seismic liquefied se-quence of unconsolidated soft sediments with high content of pore water and seismic sequence of semi- consolidated or consolidated sediments dominated by fracture and broken deformation were summarized. The feature and integrity of sequence depend on the location of section，magnitude of earthquake and duration time，especially lithologic characters of seismic area. The research about di--tinguishing marks of lacustrine slsmite core and genesis provide geologists with one of correlation standards for identifying the event deposition of lacustrine basin and judging the genesis of reservoir andbody as well a theoreticll foundatiom for judging the ‘ polyge-nesis，of reservoir sandbody in Jiyang depresion.