Framework of Sequence Stratigraphy and Depositional Characteristics of Yingcheng Formation in Lishu Fault Depression

Key words: 
• Lishu fault depression /
• Yingcheng Formation /
• sequence stratigraphy framework /
• sedimentary characteristic

Abstract: Based on the sequence stratigraphy theory of Vail, sequence stratigraphy framework of Yingcheng Formation in Lishu fault depression is established through analysing  seismic data, core data, logging data and other materials. Yingcheng Formation  is divided into 4 3rd-order sequences from the bottom to the top, SQ1, SQ2, SQ3, SQ4, which are, respectively,  equal to YC1, YC2, YC3, YC4 stages. SQ1-SQ3 at the bottom are T-R sequences, and SQ4 sequence is composed of transgressive system. According to the characteristics of sequence development of target strata in the study area, and based on the division and comparison of sequence formation unit, this paper studies on sedimentary types and its distribution law. This area mainly develops fan delta and braided river delta, which are characteristicted by  mixed-source sedimentary and regional distribution. The whole area develops fan delta in SQ1; SQ2 exits fan delta in the east area and braided river delta in the north area of the depression. The sedimentary facies evolved to braided river delta within the scope of whole depression in SQ3 and SQ4 sequences.