EARLY TERTIARY SEDIMENTARY ENVIRONMENT AND THE OIL AND GAS OF DONG MING DEPRESSION

Dong Ming Depression is an early Tertiary block-faulting basin of graben type.The basin in-fillings are predominatingly clastic with subordinate lacustrine chemical rocks.Fluvial sediment developed only in Dong Ying Formation,The lacustrine sediments of Dong Ming Depression are devided into three sedimentary systems:lacustrine allochthonous clastic;and reworked sediments.It is thought that the alluvial fan subfacies,overbank and lake sub-facies,and gravitational current sediment sub-fades with different sedimentary backgrounds are characteristics of the sedimentary environment for block-faulting lake.The alluvial fan sand body and the gravitational current sand body are the major reservior for oil and gas;and the combined structural and lithological trap is the main type of oil and gas traps in Dong Ming Depression.