Songliao basin has undergone tectonic uplift at the end of Qinshankou during earlier Cretaceous.The changes in stratigraphic thickness

the erosion and weathering surfaces as well as absence of paleentolagical zones reveal that various types of contacts such as conformity

disnonfatmily and uncnnfoxmity

exist in the area between Qinshankou and Yaojia Foxmalions. The Putachua reservoir was formed under the influence of the extent of erosnon zones

which has resulted in the formation of impartant sedimentary fades

such as Proluvial fens and fan deltas etc. The development of great quantitirs of these facies sueely could enhance the availability of lithological traps and consequently shouid giver rise to more prospective areas for petroleum. The existence of odap zones in the west part of this basin favors the discovering of new reservoirs of unconformit type.