东营箕状断陷沉积物源的演变

The evaluation of sedimental source in Dongying dustpanlike rift

东营箕状断陷下第三系沉积厚度大 ,孔店组—沙河街组岩石学特征变化也较大 ,具有从喷出岩屑向石英岩屑和变质岩屑演变的特征。结合断陷周缘各地层的出露情况 ,确定其剥蚀充填序列为中生界喷出岩和砂、砾岩逐渐向古生界碳酸盐岩和前震旦系片麻岩演变。该断陷沉积体系的垂向演化具有明显的两分性 ,即孔店组—沙四段沉积时期 ,为沿盆地短轴方向局限分布的冲积体系 ,表明碎屑物仅来自于其周缘的隆起 ;沙三段—沙二段沉积时期 ,为沿长轴方向广泛分布的三角洲体系 ,表明碎屑物供给充足且稳定。据此 ,可将断陷的沉积物源划分为近源物质供给期 (Ek—Es4)和远源物质供给期 (Es3—Es2 )。

The sedimentary thickness of Paleogene in Dongying dustpanlikerift is big. The lithologic characteristic change of Kongdian groupShahe group is also obvious. It has the evolutionary character from eruptive detritus to quartzose and metamorphic detritus. Combined with the emergence condition of formation in the periphery of rift, it is determined that its denudation packing sequence evolved from Mesozoic eruptive rock and quartzite to Paloeozoic carbonat rock and Presinian gneiss. The vertical evolution of this rift sedimentary system has one dividing into two, that is, during Kongdian groupEs 4 sedimentary period, there was alluvial system distributed within limits along minor axis direction of basin and detrital material only comes from its peripheral uplift, during Es 3Es 2 sedimentary period, there was delta system distributed extendedly along major axis direction and detrital material is sufficient and stable. In view of the above, the rift sedimentary source can be divided into proximal material supply period (EkEs 4) and far material supply period (Es 3Es 2).