山东小清河流域黄土的发现及勘探意义

通过钻孔取样、野外考察、粒度分析等方法对山东小清河流域浅层的沉积物特征进行研究。结果表明:小清河流域南部浅层沉积物以泥质粉砂和粉砂质泥为主,富含钙质结核和蜗牛化石等黄土标志物,发育明显的黄土-古土壤沉积旋回;南部粒度特征与青州黄土、北京降尘、西峰黄土等典型的风成沉积物相似,具有中国黄土的典型双峰特征,粒度分布明显粗于北京降尘和西峰黄土,而与邻近的青州黄土相似或较其稍粗,体现近物源的特性;末次冰期时裸露的渤海陆架是研究区黄土的主要物源区,中国东部季风和流域以南的山脉为黄土的形成提供搬运动力和地形条件;流域最北端发育古河道沉积,黄土与古河道间存在一个过渡带,沉积特征的差异和流域内南高北低的地势致使南部潜水面深度远大于北部,最终导致油气地震勘探中北部的地震激发效果明显优于南部。

Discovery and exploration significance of loess in Xiaoqinghe River drainage, Shandong Province

The characteristics of shallow sediments in the south of Xiaoqinghe River drainage, Shandong Province were studied by using samples from drilling holes, field study and grain size analysis. The results show that the shallow sediments in the south of Xiaoqinghe River drainage are mainly argillaceous silt and silty mud. The sediments consist of loess markers including calcareous concretions and snail fossils and develop obvious sedimentary cycle of loess-paleosol. By analyzing grain size of the samples systematacially and contrasting those samples with some aeolian sediments such as Qingzhou loess, Xifeng loess and dust fallouts in Beijing, it is proved that, loess from the study area carries the typical characteristics of aeolian loess in China which possesses the typical double-peak feature in grain size frequency curves. Furthermore, it is evident that the average grain size is larger than that of dust fallouts in Beijing and Xifeng loess, but is coarser than that of Qingzhou loess or resembles, which reflects a nearer provenance. The main provenance of loess in the study area is the exposed Bohai continental shelf during the last glacial period. The monsoon in the eastern China and mountains in the south area of Xiaoqinghe River drainage provide transporting force and topographic condition for the formation of loess in the study area. Paleochannels develop in the northernmost of the drainage, and there is a transitional zone between the loess and paleochannel. The depth of water table in the south of the drainage is greater than that in the north because of the difference of sedimentary characteristics and topography. The difference finally results in that the excitation effect in the north is much better than that in the south.