海拉尔盆地乌尔逊凹陷上侏罗统大磨拐河组障壁砂坝和斜坡裙沉积

ON THE SEDIMENTATION OF THE BARRIER BAR AND SLOPE APRON OF THE DAMOGUAIHE FORMATION,UPPER JURASSIC,IN THE WURXUN DEPRESSION, THE HAILAR BASIN

本文通过钻井取芯资料,并结合地震地层学和测井资料,对乌尔逊凹陷大磨拐河组的障壁砂坝和斜坡裙沉积进行了沉积学研究。障壁砂坝分布在湖滨浅水区,与湖岸线平行展布,它们与局限湾泥岩和煤层共生,组成了数百米厚的沉积层序。本区障壁砂坝多为水进型,具有明显的层理旋回特点,并具细-粗-细的垂向层序特征。斜坡裙是乌尔逊凹陷新发现的砂体类型,分布在近滨至滨外斜坡环境,斜坡裙由内碎屑砂岩和纹层状砂岩组成,与暗色泥岩互层,内碎屑的定向反映了波浪作用。斜坡裙砂体平行于沉积斜坡展布,倾向剖面为不对称的丘形,向岸一侧陡倾,而向盆地一侧缓倾。

Based on the data of drilling cores, seismic stratigraphy and loggings, the sedimentary analysis are made on the barrier bar and slope apron in the Damoguaihe Formation of the Wurhe Depression. Barrier bars distributed in the area of shallow water of lake shore, which are parallel to the lake strandline,and associated with restricted mudstone and coal layers, all together composing of sedi mentary sequences of hundreds of metres thick. Most of barrier sandstones are transgressive-type, characterized by bedding cycles with the sequence of fine-coarse-fine cycles. Slope apron is a type of sandbody newly discovered in Wurxun Dpression, and usually distributed in the onshore-offshore slope environments. It mainly consists of intraclastics and laminated sandstone, interbedded with dark mudstone. The orientation of intraclastics in the area reveals wave action. Slope apron sandbodies spreading parallel to sedimentary slope,are asymetric mound shape along the section in the direction of dip, being steep towards lake shoreline while gently dipping basinward.