Dongying depression has experienced evolution of blockfaulting

erosion and overlapping during Eogene

resulting

in a gently Waved erosional surface of basement rocks on its north steep slope where lacustrine embayments were separated by basement;noses and subaqueous alluvial fans well developed

These paleomorphological and paleotopographical features have obviously controllcd the size and geometry of fans

which can be divided into three types:1) lacustrine cliff fans;2) faulted scarp fans:and 3) terraced fans

with the first one being the dominant type. They are coalescing each other to form a kind of skirt-hem. The fans are sand and conglomerate bodies formed by rapid deposition of flood turbidite near the source area.It has become a new field for the exploration of oil and gas

since it may contain important stratigraphical types of oil traps. Different parts of these fans form different traps The model roughly is: the innerfans form stratigraphical overlapping traps;the mid-fans lithologic traps sealed by faults;the outerfans lenticular lithologic traps. The basement noses are the prerequisite ground for oil accumulation. The mid-fan front and channels

having a lot of secondary pores and good reservoir properties

may be prolific in oil and gas.