松辽盆地梨树凹陷泉头组沉积特征

松辽盆地梨树凹陷泉头组主要发育有冲积扇、辫状河、曲流河、浅水湖和滨浅湖等沉积相,盆地的轻微振荡性升降使其沉积演化可分为 4个时期,早期 (泉一段)是断陷沉积向坳陷沉积转换的过渡时期;中期 (泉二段)由于盆地沉降速率大,河流冲积作用弱,发育了大规模的浅水湖,沉积环境由浅水湖、洪泛洼地和少量曲流河组成;晚期 (泉三段-泉四段中期)区域沉积变缓、河流作用再度增强,形成十分发育的储层段;末期 (泉四段晚期)受全盆地发展影响,松辽大湖盆形成雏形并开始扩展。泉头组的沉积演化经历了河流冲积平原沉积的完整沉积序列,代表了松辽盆地断坳转换时期的沉积特征。

SEDIMENTARY CHARACTERISTICS OF QUANTOU FORMATION IN LISHU SAG OF SONGLIAO BASIN

The mainly developments of sedimentary facies in Quantou Formation of Lishu Sag in Songliao basin are as follows: alluvial fan, braided river, mendering river, shallow water lake and shore shallow water lake etc. Slightly vibration-uplift and subsidence of the basin make it possible to divide it sedimentary evolution into 4 stages; early stage( Quan No.1 interval) is the stage of fault subsidence transited to sag deposition; middle stage(Quan No.2 interval) is the stage of large scale shallow water lakes developed due to great subsidence rate of the basin and weak {effects} of river alluviation, and sedimentary environment is composed of shallow water lakes, flooding lacunae and a few meandering rivers; later stage(Quan No.3 interval and middle stage of Quan No.4 interval) reservoir intervals were quite developed due to the slow down of regional sedimentation and reinforcement of river {effect;} during final stage({later} stage of Quan No.4 interval)Songliao big lake-basin came into an embryonic form and began to expand due to the effect of the development of the whole basin. Sedimentary evolution of Quantou Formation has experienced a complete sedimentary sequence of river alluvium plain sedimentation representing the sedimentary characteristics of transformational period of Songliao basin fault sag.