Biyang Depression is a typical continental fault-depressed lacustrine basin. The Eh

3

member in the depression is in the A～B substages of late diagenesis

the cementation and solution of the diagensis bear close relation with the formation of diagenetic traps. Carbonate is the main cement; deep burial solution in the late diagenetic stage is the major solution types. The existence of shielding bed is the key factor of forming the diagenetic traps. According to their characteristics

the diagenetic traps could he divided into three types such as the traps relating to lithologic pinch out

fault and lenticular types. These traps could be further divided into 9 subtypes. The factors that effected the formation of the traps include sedimentary facies

diagenesis

the features of fluid

solution

faulting and expulsive pressure. Among them

sedimentary facies

diagencsis and the feature of fluid are the main factors.