Abstract:

An analysiswas carried out on the sedimentary features of the Paleogene Dongying Formation in the tidal area ofLiaohe Basin based on core，drilling and seism ic data aswell asmodern sedimentology concepts and methods.Six sedimentation types are identified in the Dongying Formation in the tidal area，namely fan delta，braided delta，delta，lake，beach bar and sublacustrine fan.The temporal and spatial distribution as well as the evolutionary features of the sedimentary system in the Formation was controlled by the structural background and lake level variation.The third member of the Formation was deposited in the early stage of lake expansion when the basin was experiencing themost intense subsidence.The sedimentary facies are dom inated by fan delta，braided delta and sublacustrine fan.The second member was formed during the lake expansion when the tectonic movementweakened and the lake basin was shallower.Sedimentary facies during the time were mainly braided delta and shallow lake-beach bar.The firstmemberwas deposited during lake shrinking and braided delta dom inated except for shallow lake-beach bar in local deep sags.

Key words: Formation, sedimentary feature, sedimentary system, sedimentary evolution, Liaohe Basin