岱海湖盆沿坡流与顺坡流相互作用的沉积响应

Sedimentary Response to Interaction between Alongslope and Downslope Currents in Daihai Lake,North China

为了探讨陆相湖盆中沿坡流的作用强度及其对三角洲前缘沉积的影响,对内蒙古岱海断陷湖盆的现代沉积进行了调查.通过卫星图像分析、现场湖浪观察与浮球实测、探槽挖掘与详细沉积特征描述、取样与样品分析、以及骨架剖面砂体对比,证明岱海湖盆陡坡带以顺坡流作用为主,分流河道和河口坝发育,砂体垂向连通性好,常形成大套块状砂体;缓坡带的三角洲前缘存在强烈的沿坡流与顺坡流相互作用,浪成成因的岩相最为发育,沙质沉积物席状化严重,垂向序列呈不明显的反韵律,河口砂体不对称分布,沿坡漂流的上游方向砂体连片、多层叠置、侧向连通性好;下游方向泥质夹层发育、砂体孤立、储层非均质性强.

In order to confirm the intensity of atongslope current in lacustrine basin and its effect on the sedimentation of delta front, the modem sedimentation of fault-depression lacustrine basin （Daibai Lake） in Inner Mongolia, North China has been explored in this study. Based on analysis of satellite images, on-site wave observation and floating ball measurement, trench excavation, sedimentary characteristics description, sample analysis, and sandbodies comparison at the framework section, it can be concluded that the steep side of IMibai lacustrine basin was dominated by the process of downslope current, where distributary channels and river mouth bar were developed with good connectivity of sandbodies in vertical, forming large set of massive sandbodies; the interaction between downslope and alongslope currents can be found in the delta front of the gentle side, where the wave-genetic lithofacies was welldeveloped with sandy sediments sheeted seriously, coarsening upward rhythm was not obvious in vertical sequence, sandbodies in the river mouth were distributed asymmetrically. Sandbadies in the upstream direction of alongslope drifting were distributed continuously and superposed of multi-layers, with good connectivity in lateral; in the downstream direction, muddy intercalations were welldeveloped, sandbodies were distributed isolatedly with strong heterogeneity.