Abstract:

The sedimentary characteristics are treated in this study for Jijialing profile which is located in the southeast margin of the Songliao basin. According to the accurate investigation and granulometric analysis，Jijialing profile is a typical profile which reflected the evolution of alluvial fan to meandering river.Vertically，the profile developed alluvial fan facies from 0 to 28 m, braided river facies from 28 to 70 m and meandering river facies from 70 to 510 m.The alluvial fan was divided into two subfacies，namely medial fan and distal fan.The two subfacies can be subdivided into five microfacies，namely debris flow，mudflow，fun-surface channel，cross flow and shoal materials.The braided river was divided into two subfacies，namely channel and floodplains.The two subfacies can be subdivided into three microfacies，namely channel lag deposit，braided bar and overbank.The meandering river was divided into three subfacies，namely channel，channel levee and floodplains.The three subfacies can be subdivided into five microfacies，namely channel lag deposit，point bar，natural levee， crevasse fan and overbank.The characteristics of probability cumulative grain size curves in different sedimentary facies are as follows: The probability cumulative grain size curves of alluvial fan include ‘one suspension’and‘roll-leap-suspension’ patterns；The braided river has ‘roll-leap-suspension’ pattern; The meandering river has ‘leap-suspension’ pattern.The continuous evolution of alluvial fan—braided river—meandering river reflected paleogeographic background of large terrain elevation—steep slope—peneplain during the sedimentary period of Quantou Formation in the southeast margin of the Songliao basin.

Key words: Songliao basin, Jijialing profile, Quantou Formation, sedimentary facies, sedimentary evolution