Sedimentary facies in the Changlongshan Formation, Xuanlong depression, Yanshan area, Hebei

Two types of sedimentary facies may be classified, on the basis of field observation, thin-section examination, grain-size analysis and lithologic and sedimentary facies indicators, for the high-maturity littoralneritic clastic rocks in the Qingbaikouan Changlongshan Formation, Xuanlong depression, Yanshan area. They are the nonbarrier coast facies and neritic shelf facies. The former appears in the first member of the Changlongshan Formation, and may be subdivided into the foreshore and shoreface subfacies. The latter is organized in the second member of the Changlongshan Formation, and dominated by the offshore shelf deposits. The results of research in this study lead to the construction of the sedimentary facies model, and thus provide one useful approach to the improvement of the sedimentary facies analysis and prediction of the favourable reservoirs in the study area.