CHARACTERISTICS AND PETROLEUM GEOLOGIC SIGNIFICANCES OF THE SEQUENCE BOUNDARY SURFACE OF CAMBRIAN STRATA IN TARIM BASIN

Cambrian strata in Kepingtage and Kulukegetage areas of northwest and northeast Tarim and well as logging of TS1 and YQ6 in central basin,have been studied by outcrop investigation,geochemical and petrology tests.Six types of sequence boundary surfaces have been recognized:①weathering crust;②paleosol;③paleo-karst surface;④onlap surface;⑤surface of lithologic and facies transition and ⑥ maximum flooding surface.These surfaces are categorized into four genetic types of unconformity related to orogeny,unconformity related to uplifting,transgressive onlap and exposure unconformity respectively.These genetic types reflect the interplay of sea level fluctuation and tectonic subsidence,and the resultant variations in sediment supply.Finally,the significance of characteristics of the sequence boundary surface is analyzed in detail on following aspects:(1) basin configuration and evolution;(2) their controlling effects on reservoir development and (3) their controlling effects on the migration of oil and gas (specifically,sequence boundary surfaces,fissures and fault formed a conduit system for the migration of oil and gas).This research provide basic and necessary information for further petroleum exploration in Cambrian strata in Tarim Basin.