CENOZOIC SEQUENCE STRATIGRAPHY AND CHARACTERISTICS OF THE SEDIMENTARY SYSTEM IN THE SHUBEI AREA,LIAOHE BASIN

The Shubei area is a secondary unit of the West subbasin of the Liaohe basin and a Cenozoic rift basin that developed on the Archean and Meso- and Neoproterozoic basements.The Cenozoic strata may be divided in ascending order into the Paleogene Fangshenpao Formation,Shahejie Formation and Dongying Formation and the Neogene Guantao Formation,overlain by Quaternary deposits.By an integrated study of the seismic,logging and geological data and application of the time-frequency analytical technique,the Cenozoic rift deposits may be divided into 1 continental rift megasequence,1 continental postrift heat-sink supersequence,1 synrift sink supersequence,4 sequences and 14 systems tracts,and there exist type I sequences and type II sequences.A sequence stratigraphic model of the gentle slope in a down-faulted lake basin has been constructed.The authors propose that the developments of sedimentary systems in different systems tracts have different characteristics.Between the transgressive systems tract (TST) and highstand systems tract (HST) there usually occurs a large suite of shale,which forms the main source rock and sealing rock,and the reservoir rock forms on the margins of various systems tracts.The sequence stratigraphic division in the area has great significance for the search for good-quality reservoirs and the study of the characteristics of petroleum concentration.