海拉尔-塔木察格断陷盆地大型三角洲形成机制

GENERATION MECHANISM OF LARGE DELTA IN HAILAER-TAMTSAG RIFTED BASIN

为了搞清海拉尔-塔木察格盆地大磨拐河组二段发育的前积体成因，进行了构造演化史和重矿物分析、地震剖面和测井曲线解释研究，认为大型三角洲是特定构造背景下的产物，在大磨拐河组二段沉积时断裂活动趋于静止，海拉尔-塔木察格盆地发生了整体上的翘倾——东北的翘起和西南的沉降，形成了区域性的北北东-南南西向水系，物源供给充足，形成了明显的前积结构。前积结构规模较大且顶超、底超现象明显，可作为大磨拐河组二段地震地层的对比标准。伊敏组沉积末期的强烈改造作用肢解了大磨拐河组二段形成的长轴向大型三角洲，给识别带来困难。由于三角洲的前积特征在地震剖面上具有方向性，提出的宏观上沿河流方向追踪大型三角洲的方法，有效地解决了三角洲前积体在地震剖面上的识别难题。

In order to clarify the origin of foreset body in Member Ⅱ of Upper Zuunbayan Formation of Hailaer- Tamtsag Basin, the analysis on structural evolution history and heavy mineral and the interpretation of seismic profile and logging trace were implemented. It is considered that the huge delta is generated under particular structural setting, the faulting activities tend to be rest during sedimentary period of Member Ⅱ of Damoguaihe Formation, overall tilt and subsidence occur in Hailaer-Tamtsag Basin--tilting in northeast and subsiding in southwest, which formed local NNE-SSW trending drainage system, and the sediment source is rich which formed obvious foreset configuration. The foreset configuration has relatively large scale extension, with obvious toplap and baselap, and can be used as the marker of seismic stratigraphic correlation in Member Ⅱ of Damoguaihe Formation. The strong reconstruction at the end of Yimin Formation sedimentation disrupts the long-axis huge delta formed during the Member Ⅱ of Damoguaihe Formation, which brings difficulties for identification. Since the foreset feature of delta has directivity in seismic profile, the method of macroscopically tracing huge delta along river trend effectively solved the knotty problem of identifying delta foreset body in seismic profile.