Sedimentary characteristics and sequence stratigraphy of Wumishan Formation in Lingyuan area, western Liaoning Province

Abstract：Based on outcrop information, the authors made a detailed analysis of stratigraphic sedimentary facies of the Wumishan Formation in Lingyuan area of western Liaoning Province. Depositional environment of Wumishan Formation was divided into supratidal, intertidal and subtidal zones in accordance with the regularity of epicontinental sea tides, and the Wumishan deposition model was established. On the basis of sedimentary facies, combined with sequence characteristics of the interface, the Wumishan sequence was studied, four second-order sequences and twenty-two third-order sequences were recognized, and rock, structure and characteristics of systems tract of each sequence were described systematically. Sequence boundaries were mainly indicated by sediments and sedimentary structures, especially by exposed symptoms, of the shallow water environment. SQ1 is sequence type Ⅰ, Ⅱ-type sequence is more well developed, and SQ2-SQ22 is sequence type Ⅱ. Wumishan deposition in this area belongs to a shallow continental sea sedimentary environment, so that the depositional systems tracts belong mainly to transgressive systems tract and highstand systems tract, commonly with the lack of lowstand systems tract or shelf marginal sysrems tract. It does not have the environment for the formation of condense section either, which makes the maximum flooding surface and deep-sea condense section correspondingly.