Abstract: A set of conglomerates of alluvial fan occurred in the second member of Yingcheng Formation of Liutai, southeast margin of Songliao Basin. According to different origins, it can be divided into three types: debris flow deposits, channel deposits and sheetflood deposits. The debris flow deposits is the best developed. Based on the study of components, textural maturities and grain size distributions, and by using the experiential formula, it has been found that the debris flow deposits in this area were redeposited and occurred above the water. Channel deposits and sheetflood deposits were preserved much less than debris flow deposits. Maybe they had been well developed in single cycle, however, they were eroded by the violent debris flow of the next cycle. The convergence direction of bedding and the strike of petrified wood in the channel deposits and sheetflood deposits show that the paleocurrent flowed from northwest to southeast. The direction of paleocurrent indicates that the provenance of conglomerate is Beishan which locates in the northwest of the study area. Based on the result, the origin model of gravelly alluvial fan has been set up.

Key words: Songliao Basin, Yingcheng Formation, conglomerate, sedimentary characteristics, origin model