松辽盆地东南缘六台地区下白垩统营城组二段砾岩沉积特征及成因模型

松辽盆地东南缘六台地区营城组二段发育一套冲积扇砾岩层。根据砾岩成因不同分为泥石流砾岩、河道砾岩和漫流砾岩等沉积类型,其中泥石流砾岩最为发育。通过研究泥石流砾岩的成分、结构成熟度和粒度分布特征,并运用经验公式最终判断其为再沉积的水上泥石流砾岩。河道砾岩和漫流砾岩沉积类型在本区保存较少,或许曾经在单个旋回中非常发育,但是被下个旋回猛烈的泥石流所改造。河道砾岩和漫流砾岩中层理的收敛方向及硅化木走向均表明本区古水流方向为近北西—东南向。根据古水流向等信息判断出本区砾岩的物源来自北西方向的北山,并在此基础上建立了本区砾岩冲积扇成因模型。

Sedimentary Characteristics and Origin Model of Conglomerate of Second Member,Yingcheng Formation in Liutai, Southeast Margin of Songliao Basin

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 depo-sits 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 conglome-rate 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.