关键词: 浅水三角洲, 沉积特征, 泉四段, 兴城地区, 松辽盆地北部

Abstract:

The fourth member of Quantou Formation in Xingcheng area in Songliao Basin is mainly consisted of mudstone, silty mudstone, pelitic siltstone and siltystone. Based on the analysis of mudstone color, palaeophyte fossil, sedimentary structure and logging facies, the fourth member of Quantou Formation was confirmed as retrograding shallow water delta depositional system which develops delta plain and delta front subfacies, and distributary channel and crevasse splay are the main microfacies. According to the principle of high sequence resolution stratigraphy, this paper divided the sequence of Quan-4 member, combining with the distribution regularity of sandstone and mudstone, prepared the distribution layout of sedimentary facies, and analyzed the regularity of vertical evolution. The result shows that: Quan-4 member can be divided into seven short-term sequences, from Q4-SSC1 to Q4-SSC7. During the Q4-SSC7 period, water reached the deepest, and only developed delta front subfacies; during the period of Q4-SSC1, channel sand body is mostly developed, which is the best period for development of reservoir. In the vertical, Quan-4 member experienced a sedimentary evolution process from shallow to deep water, which is an transformation process from delta plain to delta front, reflecting an lake invasion of the sedimentary process in the study area.

Key words:  shallow water delta, sedimentary characteristics, the fourth member of Quantou Formation, Xingcheng area, northern Songliao Basin