为了阐明二连盆地白音查干凹陷南部缓坡带达尔其－锡林好来地区结合部的下白垩统腾格尔组底部砾质滩坝沉积特征，在区域地质背景分析基础上，应用岩心和测井等资料，通过砾质滩坝砾岩的空间发育、结构、沉积构造及垂向沉积序列等特征分析，指出砾质滩坝砾岩呈薄层夹于泥石流砂砾岩及含砾砂泥岩沉积中；砾质滩坝砾岩中砾石磨圆较好但分选较差，杆状、扁平状砾石相对较多；砾石最大扁平面／长轴相对具一定的双向排列；砾质滩坝底部与泥石流沉积呈渐变接触并呈逆粒序，而顶部与浅湖泥或泥石流沉积多呈突变接触，整体上表现为逆—正粒序、正—逆粒序等的垂向交替变化。研究区砾质滩坝的沉积模式主要为滨浅湖波浪对早期泥石流沉积进行淘洗、簸选，其中易搬运的细粒碎屑被带入浅湖形成砂质滩坝，而难搬运的砾石则留在原地形成砾质滩坝，二者之间可能发育有沟槽。其形成条件主要有4个———较强的水动力、较平坦的地形、低位体系域发育期以及适量的物源。%In order to demonstrate the sedimentary characteristics of gravelly beach-bar in the Lower Cretaceous Tenggeer Formation in the joint area of the Xilinhaolai and Daerqi of the southern gentle slope of the Baiyinchagan sag,Erlian Ba-sin,abundant cores and logging data were utilized to analyze the spatial distribution,texture,sedimentary structure and vertical sedimentary sequences in the context of regional geological setting.The beach-bar conglomerates occur in the debris flow conglomerates and pebble sandstone-mudstone as thin interbeds,featuring in fair roundness but worse sorting, relative abundance of pebbles with barred and flat shape,and Janus configuration of maximum flat plain/major axis.It is in gradational contact with the underlying debris-flow deposits featuring in reverse grading,while it is in abrupt contact with the overlying shallow lake mudstones or debris-flow deposits,featuring,as a whole,in vertical alternation of reverse and normal grading.The sedimentary model in the study area is dominated by elutriation and winnowing of the early deb-ris-flow deposits by the waves in the waterfront and shallow lacustrine.The fine-grained clasts were transported to the shallow lake to form the sandy beach-bar,while the pebbles stayed to form gravelly beach-bar,with troughs possibly oc-curring between these two deposits system.They were formed under 4 main conditions, namely the powerful water strength,low relief landform,low system tract( LST) and suitable sedimentary sources.
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